Pneumatic tires

Abstract

To provide a pneumatic tire that can prevent a crack from reaching a carcass ply, even if the crack occurs along a joint interface between different-colored rubber and black-colored rubber.SOLUTION: The pneumatic tire comprises: a pair of left and right beads 1; a pair of left and right side walls 2 provided at outside in a tire radial direction of the pair of left and right beads 1; a tread 3 provided between the pair of left and right side walls 2; a carcass 4 extended through the side walls 2 from the tread 3 and locked at the beads 1; a different-colored rubber part 12 provided outside in a tire shaft direction of the carcass 4, in the side walls 2; and a crack preventing part 11a provided in an area wider in the tire radial direction RD than the different-colored rubber part 12, between the carcass 4 and the different-colored rubber part 12, which is constituted of rubber which is larger in carbon black content percentage than rubber constituting the different-colored rubber part 12.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] The sidewall of a tire is provided with marks such as letters, symbols, figures, etc. As the markings, for example, white letters that stand out against the tire's original black background may be used, and these are called white letter tires.

[0003] White letter tires are generally made by providing a white rubber (different color rubber) for marking on the sidewall rubber, and covering the surface of the white rubber with a cover rubber layer made of black rubber to produce an unvulcanized green tire.Then, when vulcanizing and molding the green tire, the part where the marking is to be formed is raised by the concave part of the mold, and the surface of the raised part is scraped to expose the different color rubber, thereby forming the white letter, which is a raised mark made of the different color rubber (see Patent Document 1 below).

[0004] In general, the different color rubber reinforced with non-carbon black fillers has a lower rigidity than the black rubber reinforced with carbon black, and therefore, in conventional white letter tires, cracks may occur along the bonding interface between the different color rubber and the black rubber due to repeated compression and tension during driving. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2018-103849 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in Patent Document 1, the tip of the joint interface between the different color rubber and the black rubber reaches the carcass ply provided inside the tire, so if a crack occurs along the joint interface between the different color rubber and the black rubber, the tip of the crack may reach the carcass ply and damage the carcass ply.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a pneumatic tire that can prevent cracks from reaching the carcass ply even if cracks occur along the joint interface between the different color rubber and the black rubber. [Means for solving the problem]

[0008] A pneumatic tire according to an embodiment of the present invention includes a pair of left and right beads, a pair of left and right sidewalls provided radially outward from the pair of left and right beads, a tread provided between the pair of left and right sidewalls, a carcass extending from the tread through the sidewalls and anchored to the beads, a different color rubber portion provided on the sidewall outer side of the carcass in the tire axial direction, and a crack prevention portion provided between the carcass and the different color rubber portion in a region wider in the tire radial direction than the different color rubber portion, the crack prevention portion being made of rubber having a higher carbon black content than the rubber constituting the different color rubber portion, The radially outer ends of the pair of left and right sidewalls are joined to the widthwise ends of the tread, The pair of beads includes a pair of bead cores spaced apart in the tire axial direction, and a pair of bead fillers provided on the tire radially outer side of the bead cores, the carcass includes a carcass main body portion provided between the pair of bead portions, and a turn-up portion extending from the carcass main body portion and turned back around the bead core from the inner side in the tire axial direction to the outer side and rolled up to the outer side in the tire radial direction, and the different color rubber portion is The tire radially outer end is located radially inward from the maximum tire width position, The tire has a first portion at its radially outer end which faces the carcass main body in the tire axial direction with the crack prevention portion sandwiched therebetween, and a second portion which is provided radially inward of the first portion and faces the carcass main body in the tire axial direction with the crack prevention portion and the bead filler sandwiched therebetween. Effect of the Invention

[0009] In the above pneumatic tire, even if a crack occurs along the joint interface between the different color rubber and the black rubber, the crack can be prevented from reaching the carcass ply. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a half cross-sectional view of a pneumatic tire according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a main part of the pneumatic tire of FIG. 1. [Diagram 3] FIG. 11 is an enlarged cross-sectional view of a main portion of a pneumatic tire according to a modified example of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] As shown in Fig. 1, the pneumatic tire T according to this embodiment is a pneumatic radial tire including a pair of left and right beads 1, a pair of left and right sidewalls 2 extending radially outward from the beads 1, and a tread 3 forming a contact surface by connecting radially outer ends of the pair of sidewalls 2. Note that Fig. 1 is a right half cross-sectional view of the tire T cut along a meridian cross section including the tire rotation axis, and in this example, the tire T is symmetrical.

[0012] In the figure, the symbol CL indicates the tire equatorial plane corresponding to the tire axial center. In this specification, the tire axial direction refers to the direction parallel to the tire rotation axis, and is indicated by the symbol WD in FIG. 1. The tire axially inner side refers to the direction approaching the tire equatorial plane CL, and the tire axially outer side refers to the direction away from the tire equatorial plane CL. The tire radial direction refers to the direction perpendicular to the tire rotation axis, and is indicated by the symbol RD in FIG. 1. The tire radially inner side refers to the direction approaching the tire rotation axis, and the tire radially outer side refers to the direction away from the tire rotation axis.

[0013] In the pneumatic tire T, an annular bead core 1a formed by rubber-coating a bundle of steel wires or the like in a bead 1, and a bead filler 1b having a triangular cross section located on the outer side of the bead core 1a in the tire radial direction are embedded in the bead 1. A carcass 4 is provided between the pair of right and left beads 1.

[0014] The carcass 4 runs from the tread 3 through the left and right sidewalls 2, and is anchored to annular bead cores 1a embedded in the beads 1, reinforcing the beads 1, the sidewalls 2, and the tread 3. In this example, both ends of the carcass 4 are anchored by folding back around the bead cores 1a from the inside to the outside.

[0015] The carcass 4 is made of at least one carcass ply, in which carcass cords are arranged at an angle of 70 to 90 degrees with respect to the tire circumferential direction, and in this example, is formed of two carcass plies. As the carcass cord, for example, a metal cord such as a steel cord or an organic fiber cord such as rayon, aramid, or polyester is preferably used. The carcass 4 is disposed along the inner surface of the tire, and an inner liner 5 is provided on the inner surface side of the carcass 4 as an air permeation resistant rubber layer.

[0016] A belt 6 is disposed on the outer side of the carcass 4 in the tread 3. The belt 6 is provided between the carcass 4 and the tread rubber 8 in the tread 3. The belt 6 is made up of a plurality of belt plies (for example, 2 to 4 plies) in which belt cords are arranged at an angle of 10 to 70 degrees with respect to the circumferential direction of the tire. As the belt cords, steel cords or organic fiber cords having high tensile strength are used.

[0017] In the bead 1, a rubber pad 17 is provided on the axially outer side of the bead filler 1b, covering the folded-up portion 4a of the carcass 4 from the axially outer side of the tire. A rim strip rubber 9 is disposed on the axially outer side of the rubber pad 17, and a rim line 10 consisting of small protrusions is formed on its outer surface.

[0018] In the sidewall 2, a sidewall rubber 11 and a different color rubber portion 12 are disposed on the outer side of the carcass 4 in the axial direction of the tire.

[0019] The sidewall rubber 11 is joined at its radially outer end to the width direction end of the tread rubber 8, and at its radially inner end to the radially outer end of the rim strip rubber 9. Like the tread rubber 8 and the rim strip rubber 9, the sidewall rubber 11 uses a black rubber composition (black rubber) containing carbon black as a reinforcing filler.

[0020] In this embodiment, the different color rubber portion 12 is made of white rubber and forms white letters 15 that display marks such as letters and symbols of trade names, trademarks, product numbers, etc. The different color rubber portion 12 is provided in an area on the inner side of the sidewall 2 in the tire radial direction.

[0021] 2, the tire radially outer end of the different color rubber portion 12 is located radially inward from the tire maximum width position, and is located radially outward from the tip (outer peripheral end) of the bead filler 1b and the tire radially outer end of the rim strip rubber 9. Also, the tire radially inner end of the different color rubber portion 12 is located radially outward from the rim line 10 and the tire radially inner ends of the rim strip rubber 9, and is located radially inward from the tip (outer peripheral end) of the bead filler 1b.

[0022] The different color rubber portion 12 is inclined so that both ends in the tire radial direction narrow toward the tire axially inner side. A sidewall rubber 11 is disposed on the tire axially inner side of the different color rubber portion 12. In other words, the sidewall rubber 11 extends from the end of the tread rubber 8 in the width direction toward the tire radially inner side, passes through the tire axially inner side of the different color rubber portion 12, and is provided to the radially outer end of the rim strip rubber 9, and is provided in an area wider in the tire radial direction than the different color rubber portion 12.

[0023] In this embodiment, the outer end of the different color rubber portion 12 in the tire radial direction faces the carcass 4 in the tire axial direction WD, with the sidewall rubber 11 in between. The center of the different color rubber portion 12 in the tire radial direction faces the bead filler 1b in the tire axial direction WD, with the sidewall rubber 11 in between. The inner end of the different color rubber portion 12 in the tire radial direction faces the bead filler 1b in the tire axial direction WD, with the sidewall rubber 11 and rubber pad 17 in between.

[0024] The thickness (length in the axial direction of the tire) of the sidewall rubber 11 on the axially inner side of the different color rubber portion 12 (hereinafter, this portion may be referred to as the crack prevention portion 11a) can be set arbitrarily, but it is more preferable for the thickness at the thinnest point to be 3 mm or more in order to prevent cracks.

[0025] The white rubber constituting the different color rubber portion 12 does not contain carbon black as a reinforcing filler, and is made of a rubber composition containing a filler other than carbon black (i.e., a non-carbon black-based filler), such as silica, talc, or clay. The different color rubber portion 12 is made of a rubber composition that is softer (has lower hardness) and has lower rigidity than the black rubber containing carbon black constituting the crack prevention portion 11a (i.e., the sidewall rubber 11). As an example, the rubber hardness of the different color rubber portion 12 (rubber hardness tested in accordance with the durometer hardness test (type A) of JIS K6253) can be 45 to 72.

[0026] Furthermore, the rubber constituting the sidewall rubber 11 may be a rubber composition having a lower rubber hardness than the rubber constituting the rim strip rubber 9. The rubber constituting the rim strip rubber 9 may be a rubber composition having a higher rubber hardness than the rubber constituting the rubber pad 17, and the rubber constituting the rubber pad 17 may be a rubber composition having a higher rubber hardness than the rubber constituting the bead filler 1b.

[0027] The different color rubber portion 12 is covered with a cover rubber 13 made of a black rubber composition whose outer surface is more ozone-resistant, fatigue-resistant, and cut-resistant than the different color rubber portion 12. The different color rubber portion 12 is exposed by scraping off the cover rubber 13 on the surface at raised portions 14 that are raised corresponding to the mark (letter), thereby displaying white letters 15, which are raised marks made of white rubber.

[0028] It is not necessary that the different color rubber portion 12 is provided on both side walls 2, but it may be provided only on one side which is the outer side of the vehicle when the tire is mounted on the vehicle.

[0029] In addition, in this embodiment, the rubber pad 17 and the rim strip rubber 9 cover the radially inner side of the bead filler 1b from the axially outer side of the tire, and the sidewall rubber 11 covers the tip of the bead filler 1b. However, the rubber pad 17 and the rim strip rubber 9 may be arranged to cover the entire bead filler 1b from the axially outer side.

[0030] In the pneumatic tire of this embodiment, a crack prevention portion 11a made of black rubber is disposed on the axially inner side of the different color rubber portion 12, and a rubber having a higher carbon black content (i.e., the mass of carbon black contained in the total mass of rubber) than the white rubber constituting the different color rubber portion 12 is disposed between the different color rubber portion 12 and the carcass 4. Therefore, in the unlikely event that a crack occurs along the interface of the different color rubber portion 12, the crack prevention portion 11a disposed on the axially inner side of the different color rubber portion 12 can prevent the crack from reaching the carcass 4.

[0031] Furthermore, in this embodiment, the radially inner end of the different color rubber portion 12 is located radially outward of the rim line 10, so that the different color rubber portion 12 does not come into contact with the rim flange when mounted on the vehicle, thereby preventing cracks from occurring at the interface of the different color rubber portion 12.

[0032] Furthermore, in this embodiment, the tire radially outer end of the different color rubber portion 12 is located radially inward of the maximum tire width position, so that the different color rubber portion 12 can be positioned to avoid the maximum tire width position which is likely to bend significantly during driving, thereby preventing cracks from occurring at the interface of the different color rubber portion 12.

[0033] In this specification, the dimensions of each part of a pneumatic tire and the maximum tire width position are values ​​measured in an unloaded state when the pneumatic tire is mounted on a standard rim and inflated to the standard internal pressure. The standard rim is a rim that is determined for each tire by the standard system including the standard on which the tire is based, for example, the standard rim for JATMA, and the "Measuring Rim" for TRA and ETRTO. The standard internal pressure is an air pressure that is determined for each tire by each standard in the standard system including the standard on which the tire is based, for example, the 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. However, when the tire is for a passenger car, it is usually 180 kPa, but when the tire is labeled "Extra Load" or "Reinforced", it is 220 kPa.

[0034] The pneumatic tire according to this embodiment may be a tire for various vehicles, such as a tire for passenger cars, or a heavy-duty tire for trucks, buses, and light trucks (for example, SUVs and pickup trucks).

[0035] (Example of change) The above-described embodiment is presented as an example and is not intended to limit the scope of the invention. This novel embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention.

[0036] For example, in the above embodiment, the sidewall rubber 11 is positioned on the axially inner side of the different color rubber portion 12 so as to be in contact with the different color rubber portion 12, but as shown in FIG. 3, a tape layer 16 may be provided between the different color rubber portion 12 and the sidewall rubber 11.

[0037] The tape layer 16 extends radially from the axially inner side of the different color rubber portion 12, and is provided so as to cover the entire axially inner side of the different color rubber portion 12. The tape layer 16 increases the adhesion between the different color rubber portion 12 and the sidewall rubber 11, and can prevent the migration of fillers such as carbon black between the different color rubber portion 12 and the sidewall rubber 11.

[0038] In the above embodiment, the different color rubber portion 12 is formed from white rubber that does not contain carbon black as a reinforcing filler. However, carbon black may be blended into the rubber composition that forms the different color rubber portion 12 as long as the carbon black content is smaller than that of the sidewall rubber 11.

[0039] In addition, in the above embodiment, the sidewall rubber 11 arranged on the outer surface side of the sidewall 2 is also arranged axially inside the different color rubber portion 12 to form a crack prevention portion. However, a crack prevention portion made of a rubber composition different from the sidewall rubber 11 may be arranged axially inside the different color rubber portion 12.

[0040] In the above embodiment, the folded portion 4a of the carcass 4 covers only a portion of the axial outside of the bead filler 1b. However, the folded portion 4a may be provided so as to cover the entire axial outside of the bead filler 1b, and a crack prevention portion, i.e., a rubber having a higher carbon black content than the rubber composition constituting the different color rubber portion 12, may be provided between the folded portion 4a and the different color rubber portion 12 over an area wider in the tire radial direction RD than the different color rubber portion 12. [Explanation of symbols]

[0041] 1...bead, 2...sidewall, 3...tread, 4...carcass, 5...inner liner, 6...belt, 8...tread rubber, 9...rim strip rubber, 10...rim line, 11...sidewall rubber, 12...different color rubber part, 13...cover rubber, 14...raised part, 15...white letter, 16...tape layer

Claims

1. a pair of left and right beads, a pair of left and right sidewalls provided radially outward from the pair of left and right beads, a tread provided between the pair of left and right sidewalls, a carcass extending from the tread through the sidewalls and anchored to the beads, a different color rubber portion provided on the sidewall outer side of the carcass in the tire axial direction, and a crack prevention portion provided between the carcass and the different color rubber portion in a region wider in the tire radial direction than the different color rubber portion, the crack prevention portion being made of rubber having a higher carbon black content than the rubber constituting the different color rubber portion, The radially outer ends of the pair of left and right sidewalls are joined to the widthwise ends of the tread, The pair of beads includes a pair of bead cores spaced apart in the tire axial direction, and a pair of bead fillers provided on the outer sides of the bead cores in the tire radial direction, the carcass includes a carcass main body portion provided between a pair of the bead portions, and a turn-up portion extending from the carcass main body portion and turned up around the bead core from the inner side in the tire axial direction to the outer side and rolled up to the outer side in the tire radial direction, The different color rubber portion has an outer end in the tire radial direction located radially inward from a maximum width position of the tire, and includes a first portion at the outer end in the tire radial direction facing the carcass main body portion in the tire axial direction with the crack prevention portion therebetween, and a second portion provided radially inward from the first portion and facing the carcass main body portion in the tire axial direction with the crack prevention portion and the bead filler therebetween.

2. The pneumatic tire according to claim 1 , wherein the length of the crack prevention portion in the tire axial direction is 3 mm or more.

3. The pneumatic tire according to claim 1 or 2, wherein an inner end in the tire radial direction of the different color rubber portion is located outer than a rim line in the tire radial direction.

4. The pneumatic tire according to any one of claims 1 to 3, wherein a tape layer is provided between the different color rubber portion and the crack prevention portion.

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