JP2010188931A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce sand splash noise from a new pneumatic tire without running-in. <P>SOLUTION: In the pneumatic tire including a tread section 1 with a land section 4 formed by grooves 2 and 3, the tread section 1 is composed of a tread rubber whose JIS A-hardness at 20°C is 55-75, and includes a plurality of projected portions 5 protruding 0.5-1.0 mm from a tread surface 4a of the land section 4 in a range of 50-75% to the entire area of the tread surface 4a of the land section 4. With the pneumatic tire, grains of sand are flipped by these projected portions 5, thus reducing the grains of sand cut into the tread surface 4a of the land section 4. This reduces the sand splash noise. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire suitable for suppressing sand splash noise caused by sand grains biting into a tread surface.

  A pneumatic tire is assembled to a rim and is mounted on a vehicle in a state where air is filled therein. Then, when sand particles bite into the tread surface during traveling of the vehicle, the sand particles are rolled up in the wheel house of the vehicle and repelled, thereby generating a sand splash sound. Such sand splashing, which causes sand splashing, is likely to occur when new, and tends to decrease when the tread surface becomes rough due to wear. Therefore, it is difficult to suppress the sand splashing sound until a certain amount of break-in operation is performed and the tread surface is roughened to reduce the sand bite.

  Conventionally, a pneumatic tire is known in which a tread surface is devised for the purpose of exhibiting performance on ice without running-in. Such a pneumatic tire has a land portion that is partitioned by a groove in a tread, and a large number of spew removal marks are formed on the tread surface of the land portion. The outer skin layer is not formed on the tread (see, for example, Patent Document 1).

JP 2002-301907 A

  However, in the pneumatic tire of the above-mentioned Patent Document 1, the outer skin layer is taken into the spew at the time of vulcanization molding, and the installation range with respect to the entire area of the tread surface of the spew and the protruding height from the tread surface after removing the spew. Not shown about. Therefore, in the pneumatic tire of patent document 1, it is difficult to reduce the biting of sand particles when new.

  This invention is made | formed in view of the above, Comprising: It aims at providing the pneumatic tire which can suppress a sand splash sound from the time of a new article, without running-in.

  In order to solve the above-described problems and achieve the object, the pneumatic tire of the present invention is a pneumatic tire having a tread portion in which a land portion is formed by a groove, and the tread portion has a JIS A hardness at 20 ° C. Is made of a tread rubber of 55 or more and 75 or less, and is within a range of 50% or more and 75% or less with respect to the total area of the tread of the land, and 0.5 [mm] or more and 1.0 [mm from the tread of the land. A plurality of protrusions protruding below are provided.

  According to this pneumatic tire, when a vehicle equipped with the pneumatic tire is driven, sand particles on the road surface are repelled by the convex portions on the tread surface of the land portion, so that it is difficult to bite into the tread surface of the land portion. . As a result, it is possible to suppress the generation of sand splash sound from the time of a new article. In addition, if the protrusion height of a convex part is less than 0.5 [mm], it will be hard to play a sand grain. On the other hand, if the protruding height of the convex portion exceeds 1.0 [mm], the convex portion falls down when touching the road surface and affects the running performance. Therefore, the protrusion preferably has a protrusion height in the range of 0.5 [mm] to 1.0 [mm].

  In the pneumatic tire of the present invention, the convex portion is formed such that the protruding end gradually becomes narrower as the distance from the tread surface of the land portion increases.

  According to this pneumatic tire, the convex portion formed so that the protruding end gradually becomes narrower as the distance from the tread surface of the land portion becomes easier to repel sand particles. Can be reduced.

In the pneumatic tire according to the present invention, the single convex portion is formed so that an area on the tread surface side of the land portion is in a range of 0.5 [mm ² ] to 5 [mm ² ]. Features.

  Many sand grains that dig into the treads on land have a particle size of 2.5 [mm] to 5.0 [mm]. According to this pneumatic tire, since the single convex portion is formed with an area in a range smaller than the above particle size so as to repel the sand particles having the above particle size, the sand particles bite into the tread of the land portion. Can be further reduced.

  In the pneumatic tire according to the present invention, sand encroachment on the tread is reduced by a plurality of convex portions formed on the tread of the land portion, so that sand splash noise can be suppressed from the new time without running-in.

FIG. 1 is a schematic perspective view of a tread portion of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a schematic view of a convex portion of the pneumatic tire according to the embodiment of the present invention. FIG. 3 is a schematic view of a convex portion of the pneumatic tire according to the embodiment of the present invention. FIG. 4 is a schematic view showing the action of the pneumatic tire according to the embodiment of the present invention. FIG. 5 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention.

  Embodiments of a pneumatic tire according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

  In the following description, the tire radial direction refers to a direction orthogonal to the rotational axis (not shown) of the pneumatic tire, and the inner side in the tire radial direction is the side toward the rotational axis in the tire radial direction, and the outer side in the tire radial direction. The side away from the rotation axis in the tire radial direction. The tire circumferential direction is a circumferential direction with the rotation axis as the central axis. The tire width direction refers to a direction parallel to the rotation axis, the inner side in the tire width direction is the side facing the tire equator in the tire width direction, and the outer side in the tire width direction is away from the tire equator in the tire width direction. Say the side. The tire equator plane is a plane that is orthogonal to the rotational axis of the pneumatic tire and passes through the center of the tire width of the pneumatic tire. The tire width is the width in the tire width direction between the portions located outside in the tire width direction, that is, the distance between the portions farthest from the tire equatorial plane in the tire width direction.

  The pneumatic tire of the present embodiment has a tread portion 1 as shown in FIG. The tread portion 1 is made of a tread rubber having a JIS A hardness of 55 or more and 75 or less at 20 ° C., is exposed at the outermost side in the tire radial direction of the pneumatic tire, and the surface thereof is the contour of the pneumatic tire. The surface of the tread portion 1 is formed as a tread surface that comes into contact with the road surface when a vehicle (not shown) equipped with a pneumatic tire travels.

  The tread portion 1 is provided with a plurality of main grooves 2 extending along the tire circumferential direction and parallel to the tire equatorial plane. Further, the tread portion 1 is provided with a plurality of sub-grooves 3 that extend along the tire width direction while intersecting the main grooves 2. In the tread portion 1, a block-shaped land portion 4 is formed by the main groove 2 and the sub-groove 3. Although not clearly shown in the figure, a land portion formed in a rib shape by only the main groove 2 may be used.

  In such a pneumatic tire, the tread surface 4a of the land portion 4 in the tread portion 1 is provided with a plurality of convex portions 5 protruding in the tire radial direction. The convex part 5 is made of a tread rubber having a JIS A hardness of 55 or more and 75 or less at 20 ° C. as in the tread part 1 and is in a range of 50% or more and 75% or less with respect to the total area of the tread surface 4a in all land parts 4. Is provided.

  Fig.2 (a) is a top view of an example of the convex part 5, FIG.2 (b) is a side view of the convex part 5 shown to Fig.2 (a). Moreover, Fig.3 (a) is a top view of the other example of the convex part 5, and FIG.3 (b) is a side view of the convex part 5 shown to Fig.3 (a).

  As shown in FIGS. 2 and 3, the convex portion 5 has a protruding height T in the tire radial direction from the tread surface 4a (bottom portion 5a) of the land portion 4 to the protruding end 5b of 0.5 [mm] or more. It is formed in a range of 0.0 [mm] or less.

  Further, the convex portion 5 is formed so as to gradually become narrower from the bottom portion 5a to the projecting end 5b as the distance from the tread surface 4a of the land portion 4 increases. The convex part 5 shown in FIG. 2 is formed so that the bottom part 5a is formed in a quadrangular shape, and each side of the bottom part 5a reaches the projecting end 5b so that the projecting end 5b is sharply pointed. Further, the convex portion 5 shown in FIG. 3 has a bottom portion 5a formed in a hexagonal shape, each side of the bottom portion 5a reaches the protruding end 5b and becomes shorter, the protruding end 5b becomes thinner, and the protruding end 5b reduces the bottom portion 5a. The hexagonal surface is formed. Further, although not shown in the drawing, the convex portion 5 may be formed in a cone shape in which the bottom portion 5a is formed in a polygonal shape or a circular shape and the protruding end 5b is thin and sharp as a shape close to FIG. Further, although not shown in the drawing, the convex portion 5 may have a shape close to that of FIG. 3, the bottom portion 5 a being formed in a polygonal shape or a circular shape, and the protruding end 5 b being formed with the top portion of the thrust shape as a surface. . In addition, the shape of the convex part 5 demonstrated here is based on the shape of the metal mold | die which shape | molds a pneumatic tire, In the pneumatic tire formed by vulcanizing tread rubber in this metal mold | die, the convex part 5 Is assumed to have slightly rounded corners.

Further, a single projecting portion 5, the area of a tread 4a side bottom 5a of the land portion 4 is formed in a range of 0.5 [mm ^2] or more 5 [mm ^2] or less.

  FIG. 4A shows the operation of the pneumatic tire not having the convex portion 5, and FIG. 4B shows the operation of the pneumatic tire of the present embodiment having the convex portion 5.

  As shown to Fig.4 (a), in the pneumatic tire which does not have the convex part 5, the tread 4a of the land part 4 is formed smoothly at the time of a new article. When a vehicle equipped with this pneumatic tire is driven, the sand particles S on the road surface G tend to bite into the smooth tread 4a of the land portion 4. Then, the sand particles S that have bitten into the tread 4a are wound up and repelled in the wheel house of the vehicle as the pneumatic tire rotates. For this reason, a sand splash sound is generated.

  On the other hand, as shown in FIG. 4B, in the pneumatic tire of the present embodiment having the convex portion 5, the convex portion 5 protrudes from the tread surface 4a of the land portion 4 when new. When the vehicle equipped with this pneumatic tire is driven, the sand particles S on the road surface G are repelled by the convex portions 5 on the tread surface 4a of the land portion 4, so that it is difficult to bite into the tread surface 4a of the land portion 4. As a result, it is possible to suppress the generation of sand splash noise. In addition, if the protrusion height T of the convex part 5 is less than 0.5 [mm], it will become difficult to play the sand grain S. Moreover, if the protrusion height T of the convex part 5 exceeds 1.0 [mm], the convex part 5 will fall down at the time of the earthing | grounding to the road surface G, and it will affect driving performance. Therefore, the protrusion height T of the convex portion 5 is preferably in the range of 0.5 [mm] to 1.0 [mm].

  Further, in the pneumatic tire of the present embodiment, since the protruding portion 5 is formed so that the protruding end 5b gradually becomes thinner as the distance from the tread surface 4a of the land portion 4 is increased, the sand particles S are formed in the land portion. 4 can be further reduced. In particular, as shown in FIG. 2, when the protruding end 5 b of the convex portion 5 is sharply formed, the sand particles S can be easily played by the top portion, and the biting of the sand particles S into the tread surface 4 a of the land portion 4 can be reduced. Moreover, when the bottom part 5a of the convex part 5 is formed in polygonal shape, it is easy to play the sand grain S by the corner | angular part, and the biting of the sand grain S to the tread 4a of the land part 4 can be reduced. Moreover, as shown in FIG. 3, when the protrusion end 5b of the convex part 5 is formed as a surface, the ground contact area to the ground can be increased and traveling performance can be improved.

Moreover, in the pneumatic tire of the present embodiment, the single convex portion 5 is formed in the range where the area on the tread surface 4a side of the land portion 4 is 0.5 [mm ² ] or more and 5 [mm ² ] or less. Yes. Many of the sand particles S that bite into the tread 4a of the land portion 4 have a particle size of 2.5 [mm] or more and 5.0 [mm] or less. In order to repel this sand grain S, it is preferable that the convex part 5 is formed by the bottom part 5a having an area in the range of 0.5 [mm ² ] to 5 [mm ² ] which is smaller than the particle diameter.

  In this example, as shown in FIG. 5, a performance test regarding the state of occurrence of sand splash sound was performed on a plurality of types of pneumatic tires having different conditions.

  In this performance test, a pneumatic tire having a tire size of 175 / 65R15 84S is assembled to an applicable rim (15 × 5JJ), mounted on a test vehicle (1300 [cc] front-wheel drive domestic car), and 230 kPa on a front tire. The rear tire was filled with an air pressure of 220 [kPa].

  The evaluation method creates a course in which sand [60 kg] is evenly distributed on a paved road having a length of 50 [m] × width of 3 [m]. As the sand, sand particles having a particle size of 2.5 [mm] or more and 5.0 [mm] or less among S-5 (No. 7) single-grain crushed stone defined in JIS A 5001 are used. And a panelist evaluates the sand splash sound when driving | running | working the said course with the speed 40 [km / h] with the said test vehicle from the inside of a vehicle. In this evaluation, an index value based on a conventional pneumatic tire as a reference (three points) is shown as an average of three tests, and the index value is preferably 3.25 or more.

  The pneumatic tire of the conventional example is a pneumatic tire that has been run for 100 [km] by accustoming a new article that does not have a convex portion on the tread surface of the land. The pneumatic tire of Comparative Example 1 is a pneumatic tire that has been practiced and traveled for 500 [km] with a new article that does not have a convex portion on the tread surface thereof. The pneumatic tire of Comparative Example 2 is a pneumatic tire in which riblets (unevenness) having a width of 0.5 [mm] and a depth of 1.0 [mm] are provided on the tread surface of the land portion along the tire circumferential direction. .

On the other hand, the pneumatic tire of the example is a new pneumatic tire having a convex portion on the tread surface of the land, and the pneumatic tire of Example 1 is a quadrangular pyramid shape as shown in FIG. T has a convex portion provided in a range of 1.0 [mm], an area on the tread surface side of the land portion is 0.5 [mm ² ], and 60% of the total area of the tread surface of the land portion. Further, the pneumatic tire of Example 2 has a hexagonal bottom as shown in FIG. 3 with a protruding end as a surface, a protruding height T of 1.0 [mm], and an area on the tread side of the land portion. 2.0 [mm < ² >], It has a convex part provided in 60% of range with respect to the total area of the tread of a land part.

  As shown in the test results of FIG. 5, it can be seen that in the pneumatic tires of Example 1 and Example 2, sand splash noise is suppressed.

  As described above, the pneumatic tire according to the present invention is suitable for suppressing sand splash noise from the new article without running-in.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Main groove 3 Sub groove 4 Land part 4a Tread surface 5 Convex part 5a Bottom part 5b Projection end T Projection height S Sand grain G Road surface

Claims (3)

In a pneumatic tire having a tread portion in which a land portion is formed by a groove,
The tread portion is made of a tread rubber having a JIS A hardness of 55 or more and 75 or less at 20 ° C., and is within a range of 50% or more and 75% or less with respect to the total area of the land surface. A pneumatic tire characterized by being provided with a plurality of convex portions projecting in a range of 5 mm to 1.0 mm.   2. The pneumatic tire according to claim 1, wherein the convex portion is formed such that a protruding end gradually becomes narrower as it is separated from a tread surface of the land portion. Single said convex portion according to claim 1 or 2, characterized in that the area of the tread side of the land portion is formed in a range of 0.5 [mm ^2] or more 5 [mm ^2] or less Pneumatic tires.

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