Pneumatic tires

Abstract

To restrain the color change of a different color rubber layer in a pneumatic tire in which the different color rubber layer is exposed on the external surface of a sidewall part.SOLUTION: A pneumatic tire includes a tread part 2, a sidewall part 3, a bead part 4, and a carcass 6. At least one of a pair of sidewall parts 3 includes a first sidewall rubber 10 disposed outside the carcass 6 in a tire axial direction. The first sidewall rubber 10 includes a different color rubber layer 11 and a barrier rubber layer 12. The different color rubber layer 11 has a color different from an external fundamental color of the sidewall part 3, and at least a part thereof is exposed on the external face of the sidewall part 3. The barrier rubber layer 12 is disposed between the different color rubber layer 11 and the carcass 6, and includes a first portion 16 having rubber compounding for inhibiting migration of a rubber compounding agent on the carcass 6 side to the different color rubber layer 11.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Patent Document 1 below proposes a pneumatic tire with a convex pattern formed on a sidewall portion. The pneumatic tire has a non-black rubber layer inside the sidewall portion, and a part of the non-black rubber layer is exposed on the raised surface of the convex pattern. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-203420 A Summary of the Invention [Problem to be solved by the invention]

[0004] The pneumatic tire of Patent Document 1 is expected to have an improved appearance due to the exposed different color rubber layer.

[0005] However, the different-color rubber layer has a problem that rubber compounding agents such as antioxidants are easily transferred from the surrounding rubber members, and the different-color rubber layer is easily discolored. In particular, in recent years, the sidewall portion has become thinner, and the rubber compounding agents of the carcass topping rubber tend to transfer to the different-color rubber layer, which easily causes the above-mentioned discoloration.

[0006] The present invention has been devised in view of the above-mentioned circumstances, and has as its main object to suppress discoloration of a different-color rubber layer in a pneumatic tire in which a different-color rubber layer is exposed on the outer surface of a sidewall portion. [Means for solving the problem]

[0007] The present invention is a pneumatic tire including a tread portion, a pair of sidewall portions, a pair of bead portions, and a carcass extending from one of the bead portions to the other of the bead portions, at least one of the pair of sidewall portions includes a first sidewall rubber arranged on the axially outer side of the carcass, the first sidewall rubber including a different color rubber layer and a barrier rubber layer, the different color rubber layer having a color different from a basic color of an outer surface of the sidewall portion and at least a portion of it being exposed to the outer surface of the sidewall portion, the barrier rubber layer being arranged between the different color rubber layer and the carcass, and including a first portion having a rubber compounding that suppresses migration of a rubber compounding agent on the carcass side to the different color rubber layer.

[0008] In the pneumatic tire of the present invention, it is preferable that the pair of bead portions include clinch rubbers constituting their respective outer surfaces, the first sidewall rubber includes an inner rubber portion in contact with the clinch rubber, and the barrier rubber layer includes a second portion disposed between the inner rubber portion and the different color rubber layer and having a rubber compounding that suppresses migration of the rubber compounding agents of the inner rubber portion to the different color rubber layer.

[0009] In the pneumatic tire of the present invention, it is desirable that the barrier rubber layer is disposed between the tread rubber constituting the tread portion and the different color rubber layer, and includes a third portion having a rubber compounding that suppresses migration of the rubber compounding agents on the tread rubber side to the different color rubber layer.

[0010] In the pneumatic tire of the present invention, in the tire meridian cross section, the distance from the outer end in the tire radial direction of the first sidewall rubber to the tread ground contact edge is desirably 20 to 40 mm.

[0011] In the pneumatic tire of the present invention, a boundary between a first outer surface vulcanized in a tread mold and a second outer surface vulcanized in a sidewall mold is included, and the different color rubber layer is arranged radially inward of the boundary, and in the tire meridian cross section, the distance from the boundary to the radial outer end of the different color rubber layer is desirably 10 to 30 mm.

[0012] In the pneumatic tire of the present invention, it is preferable that the tread portion includes a tread rubber, and an axially outer end of the tread rubber is covered by the first sidewall rubber.

[0013] In the pneumatic tire of the present invention, the section height is desirably 120 mm or less.

[0014] In the pneumatic tire of the present invention, it is desirable that the barrier rubber layer contains 60% or less of a butyl-based rubber. Effect of the Invention

[0015] By adopting the above-described configuration, the pneumatic tire of the present invention can suppress discoloration of the different color rubber layer. [Brief description of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view showing one embodiment of a tire of the present invention. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a sidewall portion of FIG. [Diagram 3] FIG. 3 is an enlarged view of the raised portion of FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a cross-sectional view of a pneumatic tire (hereinafter, sometimes simply referred to as "tire") 1 of this embodiment in a normal state. Note that FIG. 1 is a so-called tire meridian cross-sectional view including the tire's rotation axis. As shown in FIG. 1, the tire 1 of this embodiment is, for example, a tire for passenger cars, and is a relatively low-profile tire with a section height h1 of 120 mm or less. However, the present invention is not limited to this embodiment.

[0018] In the case of a pneumatic tire for which various standards are established, the "normal state" refers to a state in which the tire is mounted on a normal rim (not shown), inflated to the normal internal pressure, and no load is applied. In the case of a tire for which various standards are not established, the normal state refers to a standard use state according to the intended use of the tire, in which the tire is not mounted on a vehicle and no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal state.

[0019] A "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "Design Rim," and in the case of ETRTO, it is called a "Measuring Rim."

[0020] "Normal internal pressure" is the air pressure set for each tire by each standard in the standard system on which the tire 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." In the case of ETRTO, it is the "INFLATION PRESSURE."

[0021] The section height h1 means the height in the radial direction of the tire 1 from the bead base line in the normal state. The bead base line is an axial line of the tire that passes through a rim diameter position determined by the standard on which the tire is based.

[0022] The tire 1 of this embodiment includes a tread portion 2, a pair of sidewall portions 3, a pair of bead portions 4, and a carcass 6 extending from one bead portion 4 to the other bead portion 4.

[0023] The carcass 6 is composed of, for example, two carcass plies 6A and 6B. The carcass plies 6A and 6B include, for example, a plurality of carcass cords and a topping rubber covering the same. The carcass cords are arranged at an angle of, for example, 75 to 90° with respect to the tire circumferential direction. For the carcass cords, organic fiber cords such as nylon, polyester, or rayon are preferably used.

[0024] The carcass 6 has a main body portion 6a and a turn-up portion 6b. The main body portion 6a extends between the bead cores 5 of the pair of bead portions 4. The turn-up portion 6b is continuous with the main body portion 6a and is turned-up around the bead core 5 to extend radially outward of the tire. The turn-up portion 6b in this embodiment is turned-up around the bead core 5 from the inner side to the outer side in the axial direction of the tire. In addition, in the turn-up portion 6b, the outer end of one carcass ply 6A and the outer end of the other carcass ply 6B are misaligned in the radial direction of the tire.

[0025] In the tread portion 2 of this embodiment, for example, a belt layer 7 is disposed on the tire radial outer side of the carcass 6. The belt layer 7 includes, for example, two belt plies 7A and 7B. Each of the belt plies 7A and 7B includes, for example, a belt cord disposed inclined with respect to the tire circumferential direction and a topping rubber covering the belt cord. Each belt cord is preferably inclined at an angle of 10 to 45° with respect to the tire circumferential direction.

[0026] The tread portion 2 includes a tread rubber 2G. The pair of bead portions 4 include clinch rubbers 15 constituting the outer surfaces thereof. At least one of the pair of sidewall portions 3 includes a first sidewall rubber 10 disposed on the axially outer side of the carcass 6.

[0027] 2 shows an enlarged cross-sectional view of the sidewall portion 3. As shown in FIG. 2, the first sidewall rubber 10 also includes a different color rubber layer 11 and a barrier rubber layer 12.

[0028] The different color rubber layer 11 has a color (white in this embodiment) different from the basic color of the outer surface of the sidewall portion 3 (black in this embodiment), and at least a part of it is exposed to the outer surface of the sidewall portion 3. In this embodiment, most of the different color rubber layer 11 is covered with the cover rubber layer 13 composed of the basic color, and a part of the different color rubber layer 11 is exposed so as to depict letters, marks, or figures.

[0029] FIG. 3 shows an enlarged cross-sectional view of a portion (raised portion) where the different-color rubber layer 11 is exposed. In this embodiment, the raised portion 20 is provided on the outer surface of the sidewall portion 3, and the different-color rubber layer 11 is exposed at a top surface 20t on the tire axially outer side. In the manufacturing method of the tire 1 of this embodiment, for example, a part of the sidewall portion 3 including the different-color rubber layer 11 covered with the cover rubber layer 13 is inserted into a corresponding recess of a vulcanization mold to form the raised portion 20, and then the top surface of the raised portion 20 is buffed so that the different-color rubber layer 11 is exposed. Such a manufacturing method is known and is suitably applied to the tire 1 of this embodiment. Note that FIG. 2 shows the side surface of the raised portion 20, not the cross section of the raised portion 20.

[0030] In the present invention, it is only necessary that the different color rubber layer 11 is exposed, and the present invention may be applied to a tire that does not include the above-mentioned raised portion 20.

[0031] 2, the barrier rubber layer 12 is disposed between the different color rubber layer 11 and the carcass 6, and includes a first portion 16 having a rubber compounding that suppresses the rubber compounding agent on the carcass 6 side from migrating to the different color rubber layer 11. In the present invention, by adopting the above-mentioned configuration, it is possible to suppress discoloration of the different color rubber layer 11. The following mechanism is presumed to be the reason for this.

[0032] Conventionally, the different-color rubber layer 11 has tended to discolor due to migration of rubber compounding agents such as antioxidants from the surrounding rubber members and also due to the influence of ultraviolet rays and the like, thereby impairing the appearance of the sidewall portion 3. As a result of intensive research, the inventors have found that the discoloration is largely influenced by the rubber compounding agents contained in the topping rubber of the carcass 6. In addition, it has also been found that in recent years, the sidewall portion has become thinner, so the distance between the carcass 6 and the different-color rubber layer 11 is smaller, and the influence of the topping rubber of the carcass 6 is greater. In the present invention, it is presumed that the above-mentioned first portion 16 of the barrier rubber layer 12 can effectively suppress migration of the rubber compounding agents from the topping rubber of the carcass 6, thereby effectively suppressing discoloration of the different-color rubber layer 11.

[0033] A more detailed configuration of this embodiment will be described below. Each configuration described below shows a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the above-mentioned effects even if it does not have the configuration described below. In addition, even if any one of the configurations described below is applied alone to the tire of the present invention having the above-mentioned characteristics, an improvement in performance according to each configuration can be expected. Furthermore, when some of the configurations described below are applied in combination, a composite improvement in performance according to each configuration can be expected.

[0034] The barrier rubber layer 12 is composed entirely of the same rubber compounding. The rubber compounding of the barrier rubber layer 12 contains, for example, butyl-based rubber. Butyl-based rubber exhibits extremely low air permeability and can effectively suppress migration of rubber compounding agents. On the other hand, if a rubber layer containing butyl-based rubber comes into contact with a rim, there is a risk of the rim corroding. From this perspective, the barrier rubber layer 12 preferably contains 60% or less butyl-based rubber, and more preferably contains 40% to 60% butyl-based rubber.

[0035] The barrier rubber layer 12 desirably contains an inorganic clay mineral such as kaolin clay, clay, mica, feldspar, or a hydrated complex of silica and alumina. This can further suppress the migration of the rubber compounding agents. A known rubber compounding can be applied to the barrier rubber layer 12 of the present invention.

[0036] The first sidewall rubber 10 includes an inner rubber portion 21 that contacts the clinch rubber 15 of the bead portion 4. The inner rubber portion 21 is made of a rubber compounding of a general sidewall rubber. This improves durability in the vicinity of the boundary between the first sidewall rubber 10 and the clinch rubber 15. From the viewpoint of ensuring sufficient durability, the length L1 of the inner rubber portion 21 along the outer surface of the sidewall portion 3 or the bead portion 4 in the tire meridian cross section is 10 mm or more, and preferably 10 to 30 mm.

[0037] The barrier rubber layer 12 also includes a second portion 17 disposed between the inner rubber portion 21 and the different color rubber layer 11. It goes without saying that the second portion 17 has a rubber compounding that suppresses the rubber compounding agents of the inner rubber portion 21 from migrating to the different color rubber layer 11. This suppresses the migration of the rubber compounding agents from the inner rubber portion 21 to the different color rubber layer 11.

[0038] The barrier rubber layer 12 includes a third portion 18 disposed between the tread rubber 2G and the different color rubber layer 11. It goes without saying that the third portion 18 has a rubber compounding that suppresses the rubber compounding agents on the tread rubber 2G side from migrating to the different color rubber layer 11. This suppresses the migration of the rubber compounding agents from the tread rubber 2G to the different color rubber layer 11.

[0039] In this embodiment, it is preferable that the axially outer end 2a of the tread rubber 2G is covered by the first sidewall rubber 10. This improves durability in the vicinity of the boundary between the first sidewall rubber 10 including the barrier rubber layer 12 and the tread rubber 2G.

[0040] From the same viewpoint, in the tire meridian cross section, the distance L2 from the tire radial outer end 10a of the first sidewall rubber 10 to the tread ground contact edge Te is preferably 20 to 40 mm. The tread ground contact edge Te corresponds to the axially outermost ground contact position when the tire 1 in the normal state is loaded with a normal load and contacts a flat surface with a camber angle of 0°.

[0041] In the case of a pneumatic tire for which various standards are established, the "normal load" is the load that each standard specifies for each tire in the standard system including the standard on which the tire is based, and is the "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. In addition, in the case of a tire for which various standards are not established, the "normal load" refers to the load acting on one tire in the standard mounting state of the tire. The "standard mounting state" refers to a state in which the tire is mounted on a standard vehicle corresponding to the intended use of the tire, and the vehicle is stationary on a flat road surface in a drivable state.

[0042] The different-color rubber layer 11, except for the cover rubber layer 13 covering the outer surface thereof, is in contact only with the barrier rubber layer 12 and is not in contact with other rubber members, thereby reliably suppressing migration of rubber compounding ingredients.

[0043] The outer surface of the tire 1 includes a boundary 25 between a first outer surface 23 vulcanized in a tread mold and a second outer surface 24 vulcanized in a sidewall mold. In general, slight burrs tend to occur at the boundary 25 due to rubber entering the gap between the two molds. That is, the movement of rubber during vulcanization is large near the boundary 25. In a tire 1 having a relatively small section height as in the present embodiment, the boundary 25 and the different color rubber layer 11 are close to each other, and the movement of rubber near the boundary 25 may cause the different color rubber layer 11 to be exposed at unintended locations. To prevent such a problem, the different color rubber layer 11 is disposed on the inner side in the tire radial direction than the boundary 25. In addition, in the tire meridian cross section, the distance L3 from the boundary 25 to the outer end 11a in the tire radial direction of the different color rubber layer 11 is preferably, for example, 10 to 30 mm.

[0044] The cover rubber layer 13 has a sufficient thickness to prevent the different color rubber layer 11 from being exposed in unnecessary places. On the other hand, if the cover rubber layer 13 is too thick, the workability of the buffing described above may decrease. From this viewpoint, the cover rubber layer 13 is desirably 0.5 to 1.0 mm.

[0045] In a more desirable embodiment, the cover rubber layer 13 is made of the same rubber compound as the barrier rubber layer 12. This makes it possible to suppress peeling of the cover rubber layer 13.

[0046] Although the preferred embodiments of the pneumatic tire of the present invention have been described in detail above, the present invention is not limited to the above specific embodiments and can be modified and practiced in various aspects. EXAMPLES

[0047] A pneumatic tire of size 225 / 50R18 having the basic structure of FIG. 1 was prototyped based on the specifications of Table 1. As a comparative example, a pneumatic tire in which a barrier rubber layer was not disposed between the carcass and the different color rubber layer was prototyped. The comparative example tire has substantially the same configuration as the example tire, except for the above-mentioned points. The discoloration resistance performance of the different color rubber layer was tested for each test tire. The common specifications and test methods for each test tire are as follows. Rim: 18×7.0J Tire pressure: 220kPa

[0048] <Discoloration resistance of different color rubber layers> The test tire was run for 18 hours at a speed of 80 km / h on a drum tester with a constant vertical load. During this run, ultraviolet light was continuously irradiated using a black light on the exposed part of the different-colored rubber layer on the sidewall. After the run, the degree of discoloration of the exposed part of the different-colored rubber layer was visually evaluated. The results were shown on a 5-point scale from 1 to 5, with a higher score indicating better discoloration resistance. The test results are shown in Table 1.

[0049] [Table 1]

[0050] As a result of the test, it was confirmed that the discoloration resistance performance of the different color rubber layer of the tire of the embodiment example was 4 to 5 points, and discoloration of the different color rubber layer was effectively suppressed. [Explanation of symbols]

[0051] 2 Tread section 3 Sidewall 4 Bead section 6. Carcass 10 First sidewall rubber 11 Different color rubber layer 12 Barrier rubber layer 16 Part 1

Claims

1. A pneumatic tire, The tire includes a tread portion, a pair of sidewall portions, a pair of bead portions, and a carcass extending from one of the bead portions to the other of the bead portions, At least one of the pair of sidewall portions includes a first sidewall rubber disposed axially outward of the carcass, The first sidewall rubber includes a different color rubber layer and a barrier rubber layer, the different color rubber layer has a color different from a basic color of the outer surface of the sidewall portion, and at least a part of the different color rubber layer is exposed to the outer surface of the sidewall portion, the barrier rubber layer includes a first portion that is disposed between the different-color rubber layer and the carcass and has a rubber compounding that suppresses migration of a rubber compounding agent on the carcass side to the different-color rubber layer, The tire includes a boundary between a first outer surface vulcanized and molded in a tread mold and a second outer surface vulcanized and molded in a sidewall mold, the different color rubber layer is disposed radially inward of the boundary, In a tire meridian cross section, a distance from the boundary to an outer end of the different color rubber layer in a tire radial direction is 10 to 30 mm. Pneumatic tires.

2. The pair of bead portions each include a clinch rubber that configures an outer surface of the pair of bead portions, the first sidewall rubber includes an inner rubber portion in contact with the clinch rubber, 2. The pneumatic tire according to claim 1, wherein the barrier rubber layer is disposed between the inner rubber portion and the different color rubber layer and includes a second portion having a rubber compounding that suppresses migration of a rubber compounding agent of the inner rubber portion to the different color rubber layer.

3. 3. The pneumatic tire according to claim 1, wherein the barrier rubber layer is disposed between a tread rubber constituting the tread portion and the different-color rubber layer, and includes a third portion having a rubber compounding that suppresses migration of a rubber compounding agent on the tread rubber side to the different-color rubber layer.

4. 4. The pneumatic tire according to claim 3, wherein in a tire meridian cross section, a distance from an outer end in a tire radial direction of the first sidewall rubber to a tread ground contact edge is 20 to 40 mm.

5. The tread portion includes a tread rubber, The pneumatic tire according to claim 1 , wherein an axially outer end of the tread rubber is covered by the first sidewall rubber.

6. A pneumatic tire described in any one of claims 1 to 5, having a section height of 120 mm or less.

7. A pneumatic tire as described in any one of claims 1 to 6, wherein the barrier rubber layer contains 60% or less of butyl-based rubber.

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