JP2010137604A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire improved in durability and rigidity by suppressing separation on an interface of dissimilar color rubber layers arranged on a sidewall. <P>SOLUTION: The pneumatic tire comprises a bead filler 1b provided at a bead 1, a carcass ply 4 wound up so as to hold the bead filler 1b, and a black side rubber layer 10 formed at the outer side of the carcass ply 4 of the sidewall 2, and a white letter or line is formed at least at one side of the sidewall 2. A white rubber layer 11 is formed adjacent to the outer side of the side rubber layer 10, an inner circumferential end of the white rubber layer 11 is located at the inner side in the tire radial direction from an outer circumferential end of the bead filler 1b, and an interface between the side rubber layer 10 and the white rubber layer 11 forms a wavy shape at the section of a tire meridian. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which characters and lines having different colors are formed on a sidewall portion.

  Conventionally, a pneumatic tire in which characters and lines of different colors are formed on a sidewall portion is known for the purpose of enhancing fashionability. In the following Patent Document 1, a different color rubber layer having a color different from that of the side rubber layer is disposed outside the carcass ply of the sidewall portion, and the different color rubber layer is covered with a cover rubber having the same color as the side rubber layer, A method is disclosed in which a cover rubber is scraped off into a line shape to expose a different color rubber layer.

  As such a different color rubber layer, a white rubber layer has been conventionally used and is used to form various white patterns. The white rubber layer is generally disposed in a region closer to the bead portion than the maximum tire width position where compression strain tends to act repeatedly during running, and such a white rubber layer is disposed. Tires are often used mainly for high-load vehicles such as RV (recreational vehicle) and LT (light truck).

  Since the white rubber layer retains its white color, carbon black having a high reinforcing property cannot be used. Therefore, the white rubber layer is softer and less rigid than the normal side rubber layer constituting the sidewall portion. For this reason, due to the compressive strain that repeatedly acts during traveling, there is a problem that separation tends to occur at the interface between the white rubber layer and the side rubber layer adjacent thereto, and the durability and rigidity of the tire are reduced.

Patent Document 2 listed below describes a pneumatic tire in which a boundary between a tread rubber layer and a rubber layer adjacent to the circumferential belt layer or a coating rubber of the circumferential belt layer is an uneven surface. However, this is merely a structure for preventing tread rubber peeling (chunk out), and does not assume a countermeasure against separation in a different color rubber layer such as a white rubber layer disposed in the sidewall portion.
JP-A-9-1694 JP-A-9-71105

  The present invention has been made in view of the above circumstances, and its purpose is to suppress the occurrence of separation at the interface of the different color rubber layer disposed in the sidewall portion, and to improve durability and rigidity. The purpose is to provide tires.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire of the present invention includes a bead filler provided in a bead portion, a carcass ply wound up so as to sandwich the bead filler, and a first disposed on the outside of the carcass ply in a sidewall portion. A pneumatic tire having a second color character or line different from the side rubber layer on at least one of the side wall portions, wherein the second color different color rubber layer is the side rubber layer. The inner peripheral end of the different color rubber layer is disposed on the inner side in the tire radial direction from the outer peripheral end of the bead filler, and the interface between the side rubber layer and the different color rubber layer is a tire meridian cross section. It has a wave shape.

  In the pneumatic tire according to the present invention, when the interface between the side rubber layer and the different color rubber layer has a wave shape in the tire meridian cross section, the contact between both the rubber layers is compared to the case where the interface is formed flat. The area can be increased. Therefore, the adhesion strength between the two rubber layers can be increased to suppress the occurrence of separation, and the durability of the tire can be improved. And since the volume of a side rubber layer can be increased because this interface makes a wave shape, the improvement of tire rigidity can be aimed at.

  In the present invention, it is preferable that the wavelength of the interface in the inner peripheral portion of the different color rubber layer is smaller than the wavelength of the interface in the outer peripheral portion. Thereby, since the adhesive strength of the interface is further increased in the inner peripheral side portion of the different color rubber layer, which tends to increase the compressive strain, the occurrence of separation can be suppressed accurately, and the durability of the tire can be effectively improved. In addition, since the wavelength of the interface is relatively large at the outer peripheral side portion of the different color rubber layer, it is possible to contribute to a reduction in the occurrence of a problem that air stays at the interface during tire molding (hereinafter referred to as “air entering”).

  In the present invention, it is preferable that the radius of curvature of the top of the interface protruding toward the side rubber layer is smaller than the radius of curvature of the top of the interface protruding toward the different color rubber layer. Thereby, the volume of a side rubber layer can be increased as much as possible and it can contribute to the improvement of durability and rigidity of a tire.

  In the present invention, the interface may be formed of uneven stripes that are inclined with respect to the tire radial direction and extend radially in the tire axial direction view. According to such a configuration, even if a minute separation occurs at the interface between the side rubber layer and the different color rubber layer, the separation is prevented from propagating to the periphery, and a decrease in durability is kept to a minimum range. be able to. Moreover, since air at the interface is easily removed during molding of the tire, occurrence of air entry is suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a tire meridian cross-sectional view schematically showing an example of a pneumatic tire according to the present invention. FIG. 2 is an essential part cross-sectional view showing the principal part in an enlarged manner. The pneumatic tire includes a pair of bead portions 1, a sidewall portion 2 extending outward in the tire radial direction from each of the bead portions 1, a tread portion 3 connected to each outer peripheral end of the sidewall portion 2, and a pair of beads. A radial tire including a carcass ply 4 disposed so as to be bridged between the portions 1.

  The bead portion 1 has an annular bead core 1a formed by rubber-covering a converging body such as a steel wire, and an annular bead filler 1b made of hard rubber having a triangular cross section located outside the bead core 1a in the tire radial direction. Is provided. The carcass ply 4 is wound up so as to sandwich the bead core 1a and the bead filler 1b and engages an end portion thereof, and an inner liner rubber layer 5 for holding air pressure is disposed inside thereof. In the present embodiment, an example in which one carcass ply 4 is disposed is shown. However, in the present invention, a plurality of carcass plies may be stacked and disposed.

  A belt layer 6 and a belt reinforcing layer 7 are disposed outside the carcass ply 4 of the tread portion 3, and a tread rubber layer 8 is disposed outside the belt layer 6. On the outside of the carcass ply 4 of the bead portion 1, a rim protector 9 that contacts the rim flange when the vehicle is mounted is disposed. A side rubber layer 10 is disposed on the outside of the carcass ply 4 of the sidewall portion 2. These rubber layers are usually made of carbon black having a high reinforcing property as a filler, and exhibit a black color (first color).

  In the side wall portion 2, a white rubber layer 11 (corresponding to the different color rubber layer) exhibiting white (second color) is disposed adjacent to the outside of the side rubber layer 10. The outer surface of the white rubber layer 11 is covered with a black, thin-walled cover rubber 12, and white characters and lines are formed by grinding this to partially expose the white rubber layer 11. . The white rubber layer 11 does not necessarily need to be disposed on the sidewall portions 2 on both sides, and in this embodiment, the white rubber layer 11 is disposed only on the side that is the vehicle outer side (right side in FIG. 1) when the vehicle is mounted.

  The white rubber layer 11 has an inner peripheral end 11 a located on the inner side in the tire radial direction from the outer peripheral end of the bead filler 1 b, and is disposed in a region near the bead portion 1 in the sidewall portion 2. In this region, compression strain tends to act repeatedly during travel, and tires used in heavy duty vehicles such as RV and LT have a greater compression strain due to the recent increase in speed symbol (high speed). Tend to work.

  The rubber composition for molding the white rubber layer 11 is known, and conventionally known rubber compositions can be used without any particular limitation in the present invention. For the white rubber layer 11, carbon black is not used as a reinforcing material, and metal oxides such as alumina, magnesia, and silica are used instead. The white rubber layer 11 is softer and less rigid than the side rubber layer 10, and its rubber hardness (rubber hardness measured according to JISK6253 durometer hardness test (type A)) is, for example, 45 to 72 °.

  When compressive strain repeatedly acts during running, separation tends to occur at the interface 20 between the side rubber layer 10 and the white rubber layer 11 due to the difference in hardness and rigidity between the rubber layers 10 and 11. In the pneumatic tire, when the interface 20 has a wave shape, the contact area between the rubber layers 10 and 11 can be increased to increase the adhesive strength, and the occurrence of separation can be suppressed to improve the durability. Moreover, since the side rubber layer 10 periodically bulges outward at the interface 20, the volume of the side rubber layer 10 can be increased by the amount of bulge, and tire rigidity can be improved.

  FIG. 3 is a schematic diagram showing a cross-sectional shape of the interface 20 shown in FIG. The wavelength W of the interface 20 is preferably 20 mm or less from the viewpoint of sufficiently increasing the contact area between the rubber layers 10 and 11 and improving the adhesive strength, and suppressing the occurrence of air entry during tire molding. Therefore, it is preferably 2 mm or more. In addition, the amplitude A of the interface 20 is preferably 1 mm or more from the viewpoint of improving the adhesive strength, and is preferably 10 mm or less so that black color does not appear in the formed white characters or lines. .

  The compressive strain acting on the interface 20 tends to be larger in the inner peripheral portion closer to the rim flange than in the outer peripheral portion. Therefore, as shown in FIG. 4, it is preferable that the wavelength Wi of the interface 20 in the inner peripheral portion of the white rubber layer 11 be smaller than the wavelength Wo of the interface 20 in the outer peripheral portion. For example, the wavelength Wi is set to 2 to 5 mm, and the wavelength Wo is set to 5 to 20 mm. The region in which the wavelength is set to be small is preferably on the inner side in the tire radial direction from the center in the height direction of the white rubber layer 11, and is a region from the inner peripheral end 11 a to 25 to 50% of the height of the white rubber layer 11. It is preferable that

  Further, from the viewpoint of increasing the volume of the side rubber layer 10 as much as possible and contributing to the improvement of the durability and rigidity of the tire, as shown in FIG. 5, the curvature radius R1 of the top of the interface 20 protruding toward the side rubber layer 10 is set. The curvature radius R2 of the top of the interface 20 protruding toward the white rubber layer 11 is preferably smaller. For example, the curvature radius R1 is set to 0.5 to 3.0 mm, and the curvature radius R2 is set to 3 to 30 mm.

  As shown in FIG. 6, the interface 20 is composed of concavo-convex ridges extending annularly along the tire circumferential direction when viewed in the tire axial direction. Create a wave shape. However, in the present invention, as shown in FIG. 7, it is also possible to configure it with uneven strips that are inclined with respect to the tire radial direction and extend radially in the tire axial direction view. In this case, it is possible to prevent the propagation of separation, suppress the decrease in durability, and suppress the occurrence of air entry. Such concavo-convex strips are inclined at 0 to 45 ° with respect to the tire circumferential direction, for example. 6 and 7 are schematic diagrams, and the pitch of the uneven stripes is actually finer.

  The side rubber layer 10 and the white rubber layer 11 having such a cross-sectional wave-shaped interface can be molded by a conventionally known method, or a method of continuously forming a molded product extruded with a predetermined cross-sectional shape, or a narrow and thin wall. Any method of winding a rubber ribbon several times to form a desired cross-sectional shape may be used.

  The pneumatic tire of the present invention is the same as a normal tire except for the structure of the sidewall portion, and any conventionally known material, shape, structure, manufacturing method, etc. can be adopted in the present invention.

  INDUSTRIAL APPLICABILITY The present invention is useful as a pneumatic tire (high-load pneumatic tire) used in high-load vehicles such as RV and LT, in which a white rubber layer is often provided in the sidewall portion.

[Another embodiment]
In the above-described embodiment, the example in which the cross-sectional shape of the interface between the side rubber layer and the white rubber layer forms a wave shape extending while curving is shown, but the present invention is not limited to this, and the cross-sectional shape as shown in FIG. There may be. The interface 30 shown in (a) has a rectangular corrugated cross section, which is preferable in terms of an increase in the adhesion area and an increase in the volume of the side rubber layer. The interface 40 shown in (b) is an example in which the cross section has a triangular wave shape. However, in any case, distortion may concentrate on the corners of the interface, so the above-described embodiment is advantageous in terms of separation measures.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In addition, the evaluation item in an Example etc. measured as follows.

(1) General durability In accordance with the conditions stipulated in the US automobile safety standard FMVSS 139, a durability test is performed with a drum-type testing machine, and a failure due to separation at the interface between the side rubber layer and the white rubber layer is recognized. The running time of was measured. The result of Comparative Example 1 is set to 100, and the larger the value, the better the durability.

(2) Rigidity When a tire was mounted on a rim and a lateral force along the tire width direction was applied simultaneously with a specified load, the force required to bend the tire by a unit length was measured. The result of Comparative Example 1 is set to 100, and the larger the value, the higher the rigidity.

  In a tire having the structure as shown in FIGS. 1 and 2 (tire size: LT285 / 70R17), the interface between the side rubber layer and the white rubber layer is flattened as Comparative Example 1, and the interface is formed into a corrugated cross section. Were made Examples 1-5. In Examples 1 to 4, the interface is made of an annular ridge as shown in FIG. 6, and in Example 5, the interface is made of a radial ridge as shown in FIG. The evaluation results of each example are shown in Table 1.

  From Table 1, in Examples 1-5, compared with the comparative example 1, the general durability and rigidity can be improved. Also, in Example 2, the wavelength was reduced at the inner peripheral portion of the interface, and in Example 3, the interface amplitude was increased, so that in Example 4, the curvature radius at the top of the interface was different inside and outside. In Example 5, since the interface is formed of radial ridges, the durability or rigidity can be improved.

Tire meridian cross-sectional view schematically showing an example of a pneumatic tire according to the present invention Fig. 1 is an enlarged cross-sectional view of a main part of the pneumatic tire shown in Fig. 1. Schematic diagram showing the cross-sectional shape of the interface shown in FIG. Schematic diagram showing the cross-sectional shape of the interface according to another embodiment Schematic diagram showing the cross-sectional shape of the interface according to another embodiment Schematic diagram showing the interface seen from the tire axial direction Schematic diagram showing the interface seen from the tire axial direction Schematic diagram showing the cross-sectional shape of the interface according to another embodiment

Explanation of symbols

1 Bead part 2 Side wall part 3 Tread part 4 Carcass ply 10 Side rubber layer 11 White rubber layer (different color rubber layer)
11a Inner edge of white rubber layer 12 Cover rubber 20 Interface

Claims (4)

A bead filler provided in a bead part; a carcass ply wound up so as to sandwich the bead filler; and a side rubber layer of a first color disposed outside the carcass ply in a side wall part, In a pneumatic tire in which characters or lines of a second color different from the side rubber layer are formed on at least one of the wall portions,
A different color rubber layer of a second color is disposed adjacent to the outside of the side rubber layer, and an inner peripheral end of the different color rubber layer is located on an inner side in a tire radial direction from an outer peripheral end of the bead filler, and the side rubber layer A pneumatic tire characterized in that an interface with the different color rubber layer has a wave shape in a tire meridian cross section.   The pneumatic tire according to claim 1, wherein a wavelength of the interface in an inner peripheral side portion of the different color rubber layer is made smaller than a wavelength of the interface in an outer peripheral side portion thereof.   The pneumatic tire according to claim 1 or 2, wherein a radius of curvature of the top of the interface protruding toward the side rubber layer is smaller than a radius of curvature of the top of the interface protruding toward the different color rubber layer. .   The pneumatic tire according to any one of claims 1 to 3, wherein the interface is formed of uneven strips that are inclined with respect to a tire radial direction and extend radially in a tire axial direction view.