JP2007320354A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire having both of the on-ice performance and on-snow maneuvering stability by providing a specified skin layer on a cap tread. <P>SOLUTION: In this pneumatic tire, a tire tread member is formed by arranging the cap tread on the under tread and, furthermore, providing the skin layer in the surface of the cap tread. Hardness of the skin layer is set at 45-60 by JIS Shore hardness at 20°C, and hardness of the skin layer is set higher by 3 than the hardness of the cap tread. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire in which a specific skin layer is provided on a cap tread to achieve both on-ice performance and on-snow handling stability.

  According to Patent Document 1 of the prior art, a rubber layer having a hardness lower than that of the cap layer is arranged on the cap tread layer of the pneumatic tire, and the pneumatic is excellent in both braking performance and driving stability on a snowy and ice road surface. Tires are presented.

JP 2005-280511 A

  An object of the present invention is to provide a pneumatic tire having excellent performance on ice and driving stability on snow by disposing a skin layer having a hardness higher than that of the cap tread on the cap tread layer of the pneumatic tire. .

  According to the present invention, a tire tread member in which a cap tread is disposed on an under tread and a skin layer is further provided on the surface thereof, and the skin layer has a JIS Shore A hardness of 45 to 60 in terms of JIS Shore A hardness. And a pneumatic tire characterized in that the hardness of the skin layer is 3 or more higher than the hardness of the cap tread.

  Further, according to the present invention, the thickness ratio of the cap tread to the skin layer (the thickness of the skin layer / the thickness of the cap tread) is in the range of 0.05 to 0.5. Tires are provided.

  Moreover, according to this invention, the pneumatic tire by which the fine groove is provided in the skin layer in the block top part surface formed in the said cap tread is provided.

  Furthermore, a pneumatic tire is provided in which thermally expandable microcapsules and / or thermally expandable graphite are blended in the skin layer.

  In the present invention, as compared with the above-described prior art, a skin layer having a hardness higher than that of the cap layer is arranged on the cap tread layer of the pneumatic tire, so that the edge effect and the block rigidity are enhanced, and the performance on ice and the snow are increased. It has been found that both handling stability can be achieved.

  The structure of the tread portion of the pneumatic tire according to the present invention will be outlined with reference to FIGS. 1 and 2. FIG. 1 shows an example of a tire tread in which a narrow groove is not provided in the skin layer, and FIG. 2 shows an example of a tire tread in which a fine groove is provided in a part of the skin layer. In the tire tread of FIG. 1A, a cap tread is laminated on the upper layer of the undertread, and the skin layer of the present invention is provided on the entire surface. Further, in the tire tread of FIG. 2A, a cap tread is laminated on the upper layer of the under tread, a skin layer is formed on the entire surface, and the surface skin layer on the top of the block formed on the cap tread is thin. Grooves are provided. In the tire tread of FIG. 2 (a), the edge effect in the initial traveling is ensured by providing this narrow groove. 1 (b) and 2 (b) show the surface skin layer (in the case of the tire tread in FIG. 1 (a)) or the narrow groove and the surface skin layer (FIG. 2) of the grounding part after a certain amount of running. The case of the tire tread (a) shows the state of the tire tread portion after disappearing due to wear. Even after the narrow groove and the surface skin layer of the ground contact portion disappear after a certain amount of travel, the tire treads of FIGS. 1 (a) and 2 (a) are shown in FIGS. 1 (b) and 2 (b). In addition, the edge effect including the block rigidity is maintained by the skin layer remaining on the side surface of the block formed on the cap tread.

  In general, a tire with a large amount of silica compounded has a large electric resistance, and static electricity generated in the vehicle body is accumulated without being able to flow out to the ground through the tire, thereby causing problems such as radio noise. Since the skin layer of the invention has a high electrical conductivity due to its formulation, the effect of releasing static electricity can be obtained. In the tire tread of FIG. 1 (a) and FIG. 2 (a) in the present invention, even after the skin layer and its narrow groove on the surface of the cap tread disappear due to traveling as well as in the initial traveling state, FIG. As shown in (b), since a part of the skin layer remaining on the side surface of the block formed on the cap tread is always in contact with the ground, the function of causing the static electricity to flow to the ground through the skin layer is also provided. , Also have.

  In the pneumatic tire of the present invention, in the structure of the tire tread portion described above, a skin layer having a hardness higher than that of the cap tread is provided on the surface of the cap tread, and the skin layer has a hardness of JIS. It is necessary to employ and arrange a rubber composition having a Shore A hardness of 45 to 60, more preferably 48 to 56, and a skin layer with a hardness of 3 or more higher than that of the cap tread. As a rubber composition used for the skin layer and the cap tread, for example, a rubber composition for a general cap tread is used, and an oil blending amount or a filler blending amount such as carbon black in the blending composition is appropriately adjusted. Thus, the hardness of the skin layer and the cap tread can be set within a predetermined range. The role of the skin layer is to improve the edge effect and block rigidity of the tire tread by disposing a skin layer having a higher hardness than the cap tread on the cap tread.

  In the pneumatic tire of the present invention, the thickness ratio of the cap tread to the skin layer (the thickness of the skin layer / the thickness of the cap tread) is in the range of 0.05 to 0.5, more preferably 0.07. It is preferable to set in the range of -0.4. Here, the thicknesses of the skin layer and the cap tread are the thicknesses in the central portion of the block. When the thickness ratio between the cap tread and the skin layer is less than 0.05, the edge effect and the block rigidity are not improved. Conversely, when the thickness ratio exceeds 0.5, braking on ice is deteriorated, which is not preferable.

  In the pneumatic tire of the present invention, it is preferable that a narrow groove is provided in the skin layer on the surface of the block top formed on the cap tread in order to improve the edge effect and block rigidity. In general, the rubber composition constituting the ground contact surface (or ice contact surface) of the tire tread portion is preferably soft from the viewpoint of improving friction on ice. In this respect, in the present invention, the narrow groove is formed in the skin layer at the top of the block. By providing this, the rubber composition on the surface of the skin layer can be moved easily, so that it has the effect of braking on ice at the beginning of running. From this viewpoint, the narrow groove preferably has a width and depth of 0.1 to 0.8 mm and a pitch of 0.5 to 2 mm.

  Furthermore, in the pneumatic tire of the present invention, it is preferable to add thermally expandable microcapsules and / or thermally expandable graphite to the skin layer in order to further improve braking on ice and driving stability on snow. The amount of the thermally expandable microcapsule and / or thermally expandable graphite is preferably 1 to 15 parts by weight, more preferably 5 to 10 parts by weight, with respect to 100 parts by weight of the rubber component of the skin layer. If the blending amount is less than 1 part by weight, the desired effect cannot be exhibited, and if it exceeds 15 parts by weight, wear resistance is lowered, which is not preferable.

  The heat-expandable microcapsule blended in the skin layer of the present invention comprises thermally expandable thermoplastic resin particles encapsulated in a thermoplastic resin that is vaporized by heat to generate a gas at a temperature equal to or higher than the expansion start temperature. Heat is expanded to enclose gas in the outer shell made of the thermoplastic resin, and the true specific gravity of the gas-encapsulated thermoplastic resin particles is 0.1 or less and the particle size is 5 to 300 μm. Is preferably used. As such heat-expandable thermoplastic resin particles (unexpanded particles), trade names “EXPANCEL 091DU-80” or “EXPANCEL 092DU-120” manufactured by EXPANSEL, Sweden, or Matsumoto Yushi Seiyaku Under the trade name “Matsumoto Microsphere F-85D” or “Matsumoto Microsphere F-100D”.

  The heat-expandable graphite blended in the skin layer of the present invention is a powder particle having a particle size of 30 to 600 μm, preferably 100 to 300 μm, enclosing a substance that is vaporized by heat between the layers, and heat during vulcanization. Is expanded into a graphite expanded body. A conventionally well-known thing can be used as the said thermally expansible graphite. For example, natural scaly graphite, pyrolytic graphite, quiche graphite, etc. with concentrated sulfuric acid or nitric acid as inorganic acid and concentrated nitric acid, perchlorate, permanganate or dichromate as strong oxidizing agent Examples thereof include a crystalline compound that maintains a layered structure of carbon that has been processed to form a graphite intercalation compound. Furthermore, it is also preferable to use the acid-treated expanded graphite neutralized with a basic compound.

  In the pneumatic tire according to the present invention, first, a predetermined tread member according to the present invention simultaneously extrudes a rubber composition constituting each of an undertread, a cap tread and a skin layer into three layers by an extruder by conventional means. Then, the tread member is integrated with other predetermined members to form a green tire, and then finally obtained by heating and vulcanizing in a predetermined mold.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further, it cannot be overemphasized that the scope of the present invention is not limited to these Examples.

Preparation of rubber composition used for cap tread and skin layer According to the composition (parts by weight) shown in Table 1 below, thermally expandable microcapsules, thermally expandable graphite, rubber excluding sulfur and vulcanization accelerator, carbon black, etc. Each of the above ingredients was loaded into a 1.7 L closed Banbury mixer, mixed for 5 minutes, the rubber composition was discharged out of the mixer and cooled to room temperature, and the master batch was again charged into the Banbury mixer. A rubber composition used for the cap tread and the skin layers 1 to 5 was obtained by blending and mixing the thermally expandable microcapsule, the thermally expandable graphite, sulfur and the vulcanization accelerator.

Test tires having the layer structure defined in Table 2 below were prepared and attached to a 2000 cc vehicle, and predetermined test results were obtained according to the following test method.

Test method 1) Braking on non-running ice: The braking distance was measured when the test tire was stopped at a speed of 40 km / hour with the air pressure of the test tire set to 200 kPa and braked. The evaluation result was obtained by calculating the reciprocal of the braking distance and using an index in which the comparative example 1 that was not running was 100. The larger the value, the better the braking on ice.
2) Non-running control stability: The test tire pressure was set to 200 kPa, the surface of the snowy road was run at a speed of 40 km / hour, the feeling of each test tire by the test driver was scored, and the non-running comparative example 1 was set to 100 The index was displayed. The larger the value, the better the snow handling stability.
3) Braking on ice after running: The test tire was run at a test course consisting of a paved road surface with an air pressure of 200 kPa, and the tire was worn. The amount of wear generated in the block defined by the grooves was measured, and after running until the result reached 2 ± 0.2 mm, the above-mentioned test on ice was carried out. The comparative example 1 which has not run is indicated by an index of 100. The larger the value, the better the braking on ice.
4) Steering stability after running: Using a vehicle equipped with test tires worn in the same manner as above, run on a snowy road surface at a speed of 40 km / hour, and score the feeling of each test tire by a test driver. The comparative example 1 of driving | running | working was set as the index | exponent. The larger the value, the better the snow handling stability.

  From the results of Table 2 above, it can be seen that in the pneumatic tire according to the present invention, an excellent pneumatic tire having both on-ice braking and on-snow handling stability is obtained.

It is a partial longitudinal cross-sectional view of the tire tread which does not have a narrow groove in the skin layer which is one embodiment of this invention. It is a fragmentary longitudinal cross-sectional view of the tire tread which has a narrow groove in the skin layer which is one embodiment of this invention.

Claims (4)

  A tire tread member in which a cap tread is disposed on an under tread and a skin layer is further provided on the surface thereof, and the skin layer has a JIS Shore A hardness of 45 to 60 at 20 ° C., and the skin A pneumatic tire characterized in that the hardness of the layer is 3 or more higher than the hardness of the cap tread.   The pneumatic tire according to claim 1, wherein a thickness ratio of the cap tread and the skin layer (a thickness of the skin layer / a thickness of the cap tread) is in a range of 0.05 to 0.5.   The pneumatic tire according to claim 1 or 2, wherein a narrow groove is provided in a skin layer on a top surface of the block formed on the cap tread.   The pneumatic tire according to any one of claims 1 to 3, wherein the skin layer is blended with thermally expandable microcapsules and / or thermally expandable graphite.

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