Pneumatic tire

Abstract

Provided is a pneumatic tire in which a different-color rubber layer is exposed on the outer surface of a side portion, and discoloration of the different-color rubber layer is suppressed. The pneumatic tire includes a tread portion (2), a pair of side portions (3), a pair of bead portions (4), and a carcass (6). At least one of the pair of side portions (3) includes a first side rubber (10). The first side rubber (10) includes a base rubber layer (9), a different-color rubber layer (11), and a barrier rubber layer (12). The base rubber layer (9) is in contact with the carcass (6). At least a portion of the different-color rubber layer (11) is exposed on the outer surface of the side portion (3). The barrier rubber layer (12) is disposed between the different-color rubber layer (11) and the base rubber layer (9), and has rubber compounding that suppresses transfer of a rubber compounding agent on the base rubber layer (9) side to the different-color rubber layer (11). The thickness of the barrier rubber layer (12) is 1.0 mm or less.

Description

TECHNICAL FIELD

[0001] The present application relates to a pneumatic tire. BACKGROUND

[0002] In the following Patent Literature 1, a pneumatic tire in which a convex pattern is formed in a side portion is proposed. The pneumatic tire has a non-black rubber layer inside the side portion, and a part of the non-black rubber layer is exposed on a raised surface of the convex pattern.

[0003] Patent Literature 1: Japanese Patent Application Publication No. 2016-203420

[0004] The pneumatic tire of Patent Literature 1 expects an improvement in appearance by the exposed different color rubber layer.

[0005] However, the different color rubber layer has a problem that a rubber additive such as an anti-aging agent is transferred from a rubber member around the different color rubber layer, and thus easily discolors. On the other hand, it is conceivable to provide a barrier rubber layer having a rubber formulation capable of suppressing the transfer of the rubber additive between the different color rubber layer and other rubber members. However, such a barrier rubber layer is high in cost compared to other rubber members, and has a tendency to be low in durability. SUMMARY

[0006] The present application has been made in view of the above-described actual circumstances, and a main object thereof is to maintain the manufacturing cost and durability of a tire, and suppress discoloration of a different color rubber layer in a pneumatic tire in which a different color rubber layer is exposed on an outer surface of a side portion.

[0007] The present application is a pneumatic tire including a tread portion, a pair of side portions, a pair of bead portions, and a carcass from one of the bead portions to the other bead portion, at least one of the pair of side portions including a first side rubber disposed on an outer side of the carcass in a tire axial direction, the first side rubber including a base rubber layer, a different color rubber layer, and a barrier rubber layer, the base rubber layer being in contact with the carcass, the different color rubber layer having a color different from a basic color of an outer surface of the side portion, and at least a part of the different color rubber layer being exposed on the outer surface of the side portion, the barrier rubber layer being disposed between the different color rubber layer and the base rubber layer, and having a rubber formulation that suppresses transfer of a rubber additive on the base rubber layer side to the different color rubber layer, the barrier rubber layer having a thickness of 1.0 mm or less.

[0008] In the pneumatic tire of the present application, it is preferable that the pair of bead portions include a chafer rubber that constitutes an outer surface of each of the bead portions, and a portion of the barrier rubber layer is exposed on an outer surface of the side portion, and a distance from an inner end of the barrier rubber layer in the tire radial direction to the chafer rubber along the outer surface of the side portion on the outer surface of the side portion is 10 mm to 30 mm.

[0009] In the pneumatic tire of the present application, it is preferable that the first side rubber include a cover rubber layer that covers an outer surface of the tire in the tire axial direction of the different color rubber layer and exposes a portion of the different color rubber layer, and the cover rubber layer is constituted of the same rubber compound as the barrier rubber layer.

[0010] In the pneumatic tire of the present application, it is preferable that the pneumatic tire include a boundary between a first outer surface that is vulcanization-molded by a tread mold and a second outer surface that is vulcanization-molded by a side mold, and the different color rubber layer is disposed at a position that is located more inward in the tire radial direction than the boundary, and in a tire meridian cross section, a distance from the boundary to an outer end of the different color rubber layer in the tire radial direction is 10 mm to 30 mm.

[0011] In the pneumatic tire of the present application, it is preferable that the different color rubber layer include an exposed portion that is exposed on an outer surface of the side portion, and a thickness of the different color rubber layer at a position that is separated by 10 mm outward in the tire radial direction from the exposed portion is 1.0 mm to 2.0 mm.

[0012] In the pneumatic tire of the present application, it is preferable that a distance in the tire radial direction from a bead line to an outer end of the barrier rubber layer in the tire radial direction is 65% or more of the segment height.

[0013] In the pneumatic tire of the present application, it is preferable that the segment height is 120 mm or less.

[0014] In the pneumatic tire of the present application, it is preferable that the barrier rubber layer include 60% or less of butyl-based rubber.

[0015] The pneumatic tire of the present application, by adopting the above structure, can maintain the manufacturing cost, durability of the tire, and suppress discoloration of the different color rubber layer. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a cross-sectional view showing one embodiment of the tire of the present application.

[0017] Figure 2 is Figure 1 is an enlarged cross-sectional view of the side portion of

[0018] Figure 3 is Figure 2An enlarged view of the protrusion.

[0019] Explanation of Reference Signs

[0020] 2: tread portion; 3: side portion; 4: bead portion; 6: carcass; 9: base rubber layer; 10: 1st side rubber; 11: different color rubber layer; 12: barrier rubber layer. DETAILED DESCRIPTION

[0021] Hereinafter, one embodiment of the present application will be described based on the drawings.

[0022] Figure 1 A cross-sectional view of a pneumatic tire (hereinafter, sometimes simply referred to as "tire") 1 in a normal state of the present embodiment is shown. In addition, Figure 1 is a so-called tire meridian cross-sectional view including the rotation axis of the tire. As Figure 1 shown, the tire 1 of the present embodiment is, for example, a tire for a passenger car, and is a relatively low flat tire with a section height hi of 120 mm or less. However, the present application is not limited to such a mode.

[0023] The "normal state" means a state in which the tire is assembled to a normal rim (omitted from illustration) and filled with a normal internal pressure, and is not under load, in the case where various specifications of the pneumatic tire are defined. In the case where the tire is not defined by various specifications, the normal state means a standard use state corresponding to the purpose of use of the tire, and means a state in which the tire is not mounted to a vehicle and is not under load. In the present specification, unless otherwise specified, the dimensions and the like of each portion of the tire are values measured in the normal state.

[0024] The "normal rim" is a rim that is defined for each tire in a specification system including the specification to which the tire is subjected, and is, for example, a "standard rim" if JATMA, a "Design Rim" if TRA, and a "Measuring Rim" if ETRTO.

[0025] The "normal internal pressure" is an air pressure defined for each specification in a specification system including the specification to which the tire is subjected, and is, for example, a "maximum air pressure" if JATMA, a maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" if TRA, and an "INFLATION PRESSURE" if ETRTO.

[0026] The section height hi means a height in the tire radial direction of the tire 1 from a bead base line in the normal state. In addition, the bead base line is a tire axial line that passes through a rim radial position determined by the specification to which the tire is subjected.

[0027] 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 tire body 6 extending from one bead portion 4 to the other bead portion 4.

[0028] The tire carcass 6 is, for example, composed of two carcass ply layers 6A and 6B. Carcass ply layers 6A and 6B, for example, contain multiple carcass cords and adhesive rubber covering these carcass cords. The carcass cords are, for example, arranged at an angle of 75° to 90° relative to the tire circumference. The carcass cords are preferably made of organic fibers such as nylon, polyester, or rayon.

[0029] The tire carcass 6 has a main body portion 6a and a folded-back portion 6b. The main body portion 6a extends between the bead cores 5 of a pair of bead portions 4. The folded-back portion 6b is connected to the main body portion 6a and extends outward in the radial direction of the tire, folding back around the bead cores 5. In this embodiment, the folded-back portion 6b folds back from the axially inner side of the tire to the outer side around the bead cores 5. Furthermore, in the folded-back portion 6b, the outer ends of one tire carcass ply 6A and the outer ends of the other tire carcass ply 6B are misaligned in the radial direction of the tire.

[0030] In the tread portion 2 of this embodiment, a belt layer 7 is disposed, for example, on the outer side of the tire carcass 6 in the radial direction. The belt layer 7 comprises, for example, two belt ply layers 7A and 7B. Each belt ply layer 7A and 7B comprises, for example, belt cords arranged obliquely relative to the tire circumference and adhesive rubber covering the belt cords. Preferably, each belt cord is obliquely arranged at an angle of 10° to 45° relative to the tire circumference.

[0031] The tread portion 2 includes tread rubber 2G. A pair of bead portions 4 include edge rubber 15 forming their outer surfaces. At least one of a pair of sidewall portions 3 includes a first sidewall rubber 10 disposed on the axially outer side of the tire body 6.

[0032] exist Figure 2 An enlarged cross-sectional view of the tire sidewall 3 is shown. (See image.) Figure 2 As shown, the first sidewall rubber 10 includes a base rubber layer 9, rubber layers of different colors 11, and a barrier rubber layer 12.

[0033] The base rubber layer 9 contacts the tire carcass 6 and constitutes the main part of the first sidewall rubber 10. The base rubber layer 9 preferably uses existing sidewall rubber components.

[0034] The different colored rubber layer 11 has a color different from the basic color (black in this embodiment) of the outer surface of the sidewall portion 3 (white in this embodiment), and at least a portion of it is exposed on the outer surface of the sidewall portion 3. In this embodiment, most of the different colored rubber layer 11 is covered by a covering rubber layer 13 composed of the basic color, and a portion of the different colored rubber layer 11 is exposed in a manner that depicts text, markings, or graphics.

[0035] exist Figure 3 The image shows an enlarged cross-sectional view of the exposed portions (raised portions) of the different colored rubber layers 11. In this embodiment, a raised portion 20 is provided on the outer surface of the sidewall portion 3, and the different colored rubber layers 11 are exposed on its top surface 20t on the outer side of the tire axial direction. In the manufacturing method of the tire 1 of this embodiment, for example, after a portion of the sidewall portion 3, including the different colored rubber layers 11 covered by the covering rubber layer 13, enters the recess of the corresponding vulcanizing mold to form the raised portion 20, the top surface of the raised portion 20 is polished to expose the different colored rubber layers 11. Such a manufacturing method is known and suitable for application to the tire 1 of this embodiment.

[0036] In this invention, as long as the different colored rubber layers 11 are exposed, the invention can also be applied to tires that do not have the above-mentioned raised portion 20.

[0037] like Figure 2 As shown, the barrier rubber layer 12 is disposed between the different colored rubber layers 11 and the base rubber layer 9, and has a rubber compound that inhibits the transfer of rubber compounding agents from the base rubber layer 9 side to the different colored rubber layers 11. Furthermore, the thickness t1 of the barrier rubber layer 12 is 1.0 mm or less. In this invention, by adopting the above structure, it is possible to maintain tire manufacturing costs and durability, and to suppress discoloration of the different colored rubber layers 11. The following mechanism can be inferred as a reason for this.

[0038] Conventionally, different colored rubber layers 11 tend to migrate from the surrounding rubber components and are also affected by ultraviolet light, causing discoloration and damaging the appearance of the tire sidewall 3. In this invention, by placing a barrier rubber layer 12 between the different colored rubber layers 11 and the base rubber layer 9, the aforementioned adverse conditions can be prevented.

[0039] On the other hand, the rubber components constituting the barrier rubber layer 12 tend to be more expensive and less durable compared to existing sidewall rubbers. In this invention, by limiting the thickness t1 of the barrier rubber layer 12 to less than 1.0 mm, it is possible to maintain the tire's manufacturing cost and durability.

[0040] Hereinafter, a more detailed structure of the present embodiment will be described. Note that each structure described hereinafter indicates a specific mode of the present embodiment. Therefore, the present application can of course exert the above-mentioned effects even if it does not have the structure described hereinafter. Also, in the tire of the present application having the above-mentioned characteristics, even if any one of each structure described hereinafter is applied alone, an improvement in performance corresponding to each structure can be expected. Furthermore, in the case where several of each structure described hereinafter are applied in combination, an improvement in combined performance corresponding to each structure can be expected.

[0041] The base rubber layer 9 includes a portion in contact with the edge rubber 15 of the bead portion 4. Thereby, the barrier rubber layer 12 and the different color rubber layer 11 are separated from the edge rubber 15. Also, the base rubber layer 9 includes a portion in contact with the tread rubber 2G constituting the tread portion 2. Thereby, the barrier rubber layer 12 and the different color rubber layer 11 are separated from the tread rubber 2G.

[0042] In the present embodiment, the outer end 2a of the tread rubber 2G in the tire axial direction is preferably covered with the base rubber layer 9 of the first side rubber 10. Thereby, the durability in the vicinity of the boundary between the first side rubber 10 and the tread rubber 2G is improved.

[0043] The barrier rubber layer 12 is composed of the same rubber formulation throughout. The rubber formulation of the barrier rubber layer 12 contains, for example, butyl rubber. Butyl rubber exhibits extremely low air permeability, and can effectively suppress the transfer of the rubber formulation. On the other hand, when a rubber layer containing butyl rubber comes into contact with a rim, it can possibly cause corrosion of the rim. From such a viewpoint, the barrier rubber layer 12 preferably contains 60% or less of butyl rubber, and more preferably contains 40% to 60% of butyl rubber.

[0044] Also, the barrier rubber layer 12 preferably contains a hydrous complex inorganic clay mineral of kaolin, clay, mica, feldspar, silica, and alumina. Thereby, the transfer of the rubber formulation can be further suppressed. Note that the barrier rubber layer 12 of the present application can apply a publicly known rubber formulation.

[0045] The barrier rubber layer 12 preferably has a maximum thickness of 1.0 mm or less. From the viewpoint of maintaining the manufacturing cost and durability of the tire and reliably suppressing discoloration of the different color rubber layer 11, the maximum thickness of the barrier rubber layer 12 is more preferably 0.5 mm to 1.0 mm.

[0046] The inner end 12a and outer end 12b of the blocking rubber layer 12 in the tire radial direction are exposed on the outer surface of the tire 1. In the tire radial section, the distance L1 from the inner end 12a of the blocking rubber layer 12 in the tire radial direction to the outer surface of the bead rubber 15 along the sidewall portion 3 or the bead portion 4 is preferably 10 mm to 30 mm. This suppresses damage near the inner end 12a of the blocking rubber layer 12 in the tire radial direction.

[0047] The distance from the tread contact point Te to the outer end 12b of the blocking rubber layer 12 in the tire radial direction along the outer surface of the sidewall portion 3 is preferably 20 mm or more. This suppresses damage near the outer end 12b of the blocking rubber layer 12 in the tire radial direction. Furthermore, the tread contact point Te corresponds to the contact point furthest axially outer of the tire when a normal load is applied to the tire 1 in its normal state and it contacts the plane at a camber angle of 0°.

[0048] "Regular load" refers to the load specified for each tire according to its specifications within a specification system that includes the specifications on which the tire is based, when various sizes of pneumatic tires are defined. For JATMA, it is the "maximum load capacity"; for TRA, it is the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and for ETRTO, it is the "LOAD CAPACITY". Furthermore, when tire sizes are not specified, "regular load" refers to the load acting on a single tire under its standard mounting condition. The "standard mounting condition" refers to the tire being mounted on a standard vehicle corresponding to the tire's intended use, with the vehicle stationary on a flat road surface in a drivable condition.

[0049] like Figure 1 As shown, the distance h2 (hereinafter sometimes referred to as the height h2 of the blocking rubber layer 12 in the tire radial direction) from the bead baseline to the outer end 12b of the blocking rubber layer 12 in the tire radial direction is preferably 65% ​​or more of the section height h1. In a more preferred embodiment, the height h2 of the blocking rubber layer 12 is 65% to 75% of the section height h1. Therefore, even when the sidewall portion 3 flexes, stress concentration at the outer end 12b can be suppressed.

[0050] like Figure 2 As shown, the different colored rubber layers 11 only contact the barrier rubber layer 12, and not other rubber components, except for the cover rubber layer 13 covering its outer surface. This reliably suppresses the transfer of rubber compounding agents.

[0051] The outer surface of the tire 1 includes a boundary 25 of the first outer surface 23 formed by vulcanization molding with a tread mold and the second outer surface 24 formed by vulcanization molding with a sidewall mold. Generally, there is a tendency that a slight burr is generated due to rubber entering a gap between the two molds at the boundary 25. That is, near the boundary 25, the movement of rubber at the time of vulcanization molding is large. In the tire 1 in which the segment height is small as in the present embodiment, the boundary 25 is close to the different color rubber layer 11, and due to the movement of rubber near the boundary 25, it is possible that the different color rubber layer 11 is exposed at an unexpected site. In order to prevent such a bad situation, the different color rubber layer 11 is disposed at a position inside in the tire radial direction than the boundary 25. Also, in the tire meridian cross section, the distance L2 from the boundary 25 to the outer end 11a of the different color rubber layer 11 in the tire radial direction is preferably, for example, 10 mm to 30 mm.

[0052] The different color rubber layer 11 includes an exposed portion exposed on the outer surface of the sidewall portion 3. As described above, in the present embodiment, the exposed portion of the different color rubber layer 11 is constituted on the top surface 20t of the protrusion portion 20. The thickness t2 of the different color rubber layer at a position 10 mm apart from the exposed portion to the outside in the tire radial direction is preferably 1.0 mm to 2.0 mm. Thereby, the rubber volume of the different color rubber layer 11 is sufficiently ensured around the exposed portion, and the durability of the different color rubber layer 11 is improved.

[0053] The cover rubber layer 13 has, for example, a sufficient thickness for preventing the different color rubber layer 11 from being exposed at an unnecessary site. On the other hand, when the thickness of the cover rubber layer 13 is too large, it is possible that the workability of the above-described polishing is reduced. From such a viewpoint, the thickness of the cover rubber layer 13 is preferably 0.5 mm to 1.0 mm.

[0054] In a more preferable mode, the cover rubber layer 13 is constituted by the same rubber compound as the barrier rubber layer 12. Thereby, the peeling of the cover rubber layer 13 is suppressed.

[0055] The above describes the preferable embodiment of the pneumatic tire of the present application in detail, the present application is not limited to the above-described specific embodiment, and can be changed to various modes to be implemented.

[0056]

Example

[0057] A tire having the specifications based on Table 1 was trial-produced, and the following was confirmed. Figure 1a basic structure of a pneumatic tire of size 225 / 50R18. As Comparative Example 1, a pneumatic tire in which a barrier rubber layer was not provided between the base rubber layer and the different color rubber layer was prepared. As Comparative Example 2, a pneumatic tire in which a barrier rubber layer having a thickness of 3.0 mm was provided between the base rubber layer and the different color rubber layer was prepared. The tires of Comparative Examples 1 to 2 had substantially the same structure as the tires of the examples except for the above. With respect to each of the test tires, the discoloration resistance of the different color rubber layer, the cost of the first side rubber, and the durability of the exposed portion of the different color rubber layer were tested. The common specifications of each of the test tires and the test methods were as follows.

[0058] Rim: 18 x 7.0J

[0059] Tire internal pressure: 220 kPa

[0060] <Discoloration resistance of different color rubber layer>

[0061] The test tire was run on a drum tester for 18 hours under application of a constant longitudinal load at a speed of 80 km / h. Also, during the running, the exposed portion of the different color rubber layer of the side portion was continuously irradiated with ultraviolet rays using a black light. After the running, the degree of discoloration of the exposed portion of the different color rubber layer was visually evaluated. The result was expressed in 5 ranks of 1 to 5, and the higher the score, the more excellent the discoloration resistance.

[0062] <Cost of first side rubber>

[0063] The manufacturing cost of the first side rubber was calculated. The result was expressed in 5 ranks of 1 to 5, and the higher the score, the lower the cost of the first side rubber, and the better.

[0064] <Durability of exposed portion of different color rubber layer>

[0065] After the test tire was run on a drum tester for 15,000 km under application of a constant longitudinal load at a speed of 80 km / h, the degree of damage of the exposed portion of the different color rubber layer was visually evaluated. The result was expressed in a score in which the degree of damage of Comparative Example 1 was 100, and the larger the value, the more excellent the durability of the exposed portion of the different color rubber layer.

[0066] The results of the tests are shown in Table 1.

[0067] [Table 1]

[0068]

[0069] From the test results, it was confirmed that the tire of the example could maintain the manufacturing cost of the tire, the durability, and the discoloration of the different color rubber layer was suppressed.

Claims

1. A pneumatic tire comprising a tread portion, a pair of side portions, a pair of bead portions, and a carcass from one of the bead portions to the other bead portion, at least one of the pair of side portions comprises a first side rubber disposed on a tire axial outside of the carcass, the first side rubber comprises a base rubber layer, a different color rubber layer, and a barrier rubber layer, the base rubber layer is in contact with the carcass, the different color rubber layer has a color different from a base color of an outer surface of the side portion, and at least a part of the different color rubber layer is exposed on the outer surface of the side portion, the barrier rubber layer is disposed between the different color rubber layer and the base rubber layer, and has a rubber formulation that suppresses transfer of a rubber additive on the base rubber layer side to the different color rubber layer, a thickness of the barrier rubber layer is 1.0 mm or less, the different color rubber layer comprises an exposed portion that is exposed on the outer surface of the side portion, a thickness of the different color rubber layer at a position 10 mm apart from the exposed portion toward an outside in a tire radial direction is 1.0 mm to 2.0 mm.

2. The pneumatic tire according to claim 1, wherein the pair of bead portions comprises a chafer rubber that constitutes an outer surface of each bead portion, a part of the barrier rubber layer is exposed on the outer surface of the side portion, a distance along the outer surface of the side portion from an inner end in the tire radial direction of the barrier rubber layer to the chafer rubber is 10 mm to 30 mm on the outer surface of the side portion.

3. The pneumatic tire according to claim 1 or 2, wherein the first side rubber comprises a cover rubber layer that covers an outer surface in the tire axial direction of the different color rubber layer and exposes a part of the different color rubber layer, the cover rubber layer is constituted of the same rubber formulation as the barrier rubber layer.

4. The pneumatic tire according to claim 1 or 2, wherein the pneumatic tire comprises a boundary between a first outer surface that is vulcanization-molded by a tread mold and a second outer surface that is vulcanization-molded by a side mold, the different color rubber layer is disposed at a position closer to an inner side in the tire radial direction than the boundary, a distance in the tire radial direction from the boundary to an outer end in the tire radial direction of the different color rubber layer is 10 mm to 30 mm in a tire meridian cross section.

5. The pneumatic tire according to claim 1 or 2, wherein a distance in the tire radial direction from a bead line to an outer end in the tire radial direction of the barrier rubber layer is 65% or more of a segment height.

6. The pneumatic tire according to claim 1 or 2, wherein the segment height is 120 mm or less.

7. The pneumatic tire according to claim 1 or 2, wherein the barrier rubber layer contains 60% or less of butyl rubber.

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