JP4471272B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire in which a bonding portion between a side rubber and a tread rubber is improved and durability is improved.

  During tire vulcanization molding, an air pocket called a bear may be generated between the mold and the tire. In order to prevent the generation of bears, a small hole called a vent hole is provided in the mold to release air accumulated in the mold. In order to suck out the air sufficiently, the rubber flows into the vent hole to some extent. As a result, a beard-like rubber called bent spew after molding appears on the tire surface, which is not preferable in appearance. An operation of trimming such a vent spew (trimming operation) is required, which reduces the production efficiency and increases the manufacturing cost. In particular, the shoulder portion including the joint portion between the tread rubber and the side rubber has a small radius of curvature, so that the trimming operation becomes difficult, and more time is required.

In the pneumatic tire disclosed in Patent Document 1, a plurality of fine grooves extending in the tire circumferential direction are provided in a predetermined range including a joint portion between a tread rubber and a side rubber. Fine grooves corresponding to the fine grooves are formed on the surface of the mold for molding the tire. Therefore, the air accumulated in the mold flows out along the fine groove of the mold, and the vent hole can be substantially eliminated.
Japanese Patent Laid-Open No. 8-1113010

  However, when the fine groove extending continuously in the tire circumferential direction is provided, the load is most applied to the bottom of the fine groove during traveling. As a result, a crack along the fine groove tends to occur at the joint between the tread rubber and the side rubber. Further, the cracks are extended, and the durability of the tire may be deteriorated.

  An object of the present invention is to eliminate the vent spew at the shoulder portion, improve the adhesiveness of the joint portion between the tread rubber and the side rubber, and enhance the durability.

As a result of intensive studies to solve the above-described problems, the present invention has a pair of bead cores, a carcass wound around the bead core to form a toroidal shape, and at least one sheet disposed on the crown portion of the carcass on the outer side in the tire radial direction. In a pneumatic tire provided with a belt layer, a tread rubber disposed on the outer side in the tire radial direction from the belt layer, and a pair of side rubbers connected to an end portion of the tread rubber from the outer side in the tire axial direction,
A pneumatic tire provided with a plurality of depressions having circular openings in at least 5 mm regions on both sides in the tire radial direction centering on the joint portion of the tire surface between the tread rubber and the side rubber.

  In order to vulcanize and mold the pneumatic tire according to the present invention, a convex portion for forming a depression on the inner surface of the mold corresponding to a region of at least 5 mm on both sides in the tire radial direction centering on the joint portion between the tread rubber and the side rubber. A mold with is used. At the time of vulcanization molding, air discharge is promoted along the uneven surface of the mold, and air is discharged without accumulating in the mold, thereby preventing the occurrence of bears. Furthermore, since the said junction part is pressed more strongly by the convex part of the said metal mold | die, the adhesiveness of a tread rubber and a side rubber improves.

Further, during traveling, the load is most applied to the joint, but there is no circumferential groove that is liable to crack. Therefore, generation | occurrence | production of a crack can be suppressed and durability of a tire improves. The opening of the recess may be an oval extending in the tire radial direction or the tire circumferential direction, and may be either an ellipse, a triangle, a rhombus, or a quadrangle including a parallelogram or a polygon.

The present invention provides the pneumatic tire according to claim 1, wherein the sum of the surface areas of the depressions is 15% or more of an area of a region of 5 mm on both sides in the tire radial direction centering on the joint portion.

  If the sum of the surface areas of the depressions is 15% or more of the area, the corresponding convex part of the mold will increase, the joint will be pressed sufficiently during vulcanization molding, and the adhesion between the tread rubber and side rubber will be improved. To do. In addition, from the viewpoint of promoting the air flow in the mold, it is preferable that the total surface area of the recesses is 60% or less of the area of the region.

Present invention, the surface area of the recess is 0.5mm ² ~30mm ^2, the depth of the recess is 0.2Mm～1.5Mm, the tire circumferential length of the recess is W, the tire radial direction length 3. The pneumatic tire according to claim 1, wherein a tire circumferential interval between the depressions is 1.1 W to 3.0 W, and a tire radial interval is 1.1 H to 3.0 H.

When the surface area of the dent is less than 0.5 mm ² or the depth of the dent is less than 0.2 mm, the pressure on the joint during vulcanization molding may be insufficient. If the depth of the dent exceeds 1.5 mm, a thin portion may be formed at the joint, and the strength may be reduced. When the surface area of the dent exceeds 30 mm ² , the air flow of the mold may be difficult to be promoted. Moreover, if the tire circumferential direction interval and the tire radial direction interval are smaller than the above ranges, the rubber in the region sandwiched between the depressions may become thin and cracks may occur. On the other hand, if it is larger than the above range, the density of the convex portions of the mold may be small, and the pressure on the joint during vulcanization molding may be insufficient.

  The pneumatic tire of the present invention includes a recess in the vicinity of the joint between the tread rubber and the side rubber. Since the mold is not provided with a smooth surface but has a convex part for molding the depression, air is discharged without being accumulated in the mold at the time of molding. Moreover, since the joint part of a tread rubber and a side rubber is fully pressed by the said convex part, the adhesiveness of the said joint part improves. In addition, during running, the occurrence of cracks at the joint can be suppressed, and the durability of the tire is improved.

  Hereinafter, embodiments of a pneumatic tire according to the present invention will be described with reference to the drawings. FIG. 1A is a cross section including a shoulder portion of the pneumatic tire according to the present invention, and FIG. 1B is a perspective view of the shoulder portion. In the figure, a carcass 1 having a toroidal shape for winding a pair of bead cores (not shown), two belt layers 2 disposed on the crown portion of the carcass 1 on the outer side in the tire radial direction, and the outer side in the tire radial direction from the belt layer 2 And a pair of side rubbers 4 connected to end portions of the tread rubber 3.

  The ends of the tread rubber 3 and the ends of the side rubber 4 are joined with the end of the side rubber 4 being on the outer side in the tire axial direction. A shoulder part is comprised by the block 7, and is equipped with the several hollow 6 in the vicinity of the junction part 5 (it represents with the virtual line n) on the tire surface.

  Further description will be given with reference to FIG. 2A. A plurality of depressions 6 are provided in a region S 5 mm on both sides in the tire radial direction with the joint 5 on the tire surface as the center. The length of the recess 6 in the tire circumferential direction R is W, the length in the tire radial direction A is H, and the intervals between the tire circumferential direction R and the recess 6 in the tire radial direction are L1 and L2, respectively.

  A mold for molding such a tire has a protrusion on the inner surface of the mold. Therefore, at the time of vulcanization molding, since the convex portion presses the vicinity of the joint portion 5, the adhesion between the tread rubber 3 and the side rubber 4 is improved.

  Further, the inner surface of the mold is not a smooth surface but has a convex portion and is a surface having irregularities. As a result, the air flow is promoted along the uneven surface, and the air is discharged outside the mold without accumulating in the mold.

  During traveling, the load is most applied to the joint portion 5, but there is no circumferential groove that is liable to crack. As a result, the occurrence of cracks can be suppressed, and the durability of the tire is improved.

The total surface area of the recesses 6 is preferably 15% or more of the area S. Surface area of the recess 6 is preferably 0.5mm ² ~30mm ^2. The depth D of the recess 6 is 0.2 mm to 1.5 mm, the tire circumferential direction interval L1 of the recess 6 is 1.1 W to 3.0 W, and the tire radial direction interval L2 is 1.1H to 3.0H. Is preferred.

  The BB cross-sectional shape of the recess 6 may be either a substantially semicircular shape shown in FIG. 2B or a substantially rectangular shape shown in FIG. Further, the shape of the recess 6 does not have to be circular, and may be an ellipse extending in the tire radial direction or the tire circumferential direction as shown in FIGS. 3 (a) and 3 (b). In addition, a quadrangle and a polygon including an ellipse, a triangle, a rhombus and a parallelogram may be used. Further, the depressions 6 may be arranged irregularly without being arranged regularly.

  The case where the shoulder portion is a block pattern has been described above, but may be a rib pattern. In this case, it is preferable that the sum of the areas of the depressions provided in the entire rib is 15% or more with respect to the area of the annular region 5 mm on both sides in the tire radial direction centering on the joint portion 5 on the tire surface.

  Each of 60 example tires and conventional tires according to the present invention was made as a prototype. Any tire size is 275 / 35R18. 2A and 2B, the embodiment has a surface area of 3 mm 2, a depth of 0.5 mm, a radial length W extending in the circumferential direction W, 2 mm, and a circumferential interval. The radial interval L2 over L1 is 1.8 mm. Further, the total surface area of the recesses 6 is 20% of the region S.

  Conventional example 1 is a tire manufactured with a mold having two vent holes per block, and vent spew 11 extends from the tire surface as shown in FIG. As shown in FIG. 4 (b), Conventional Example 2 is a tire provided with a plurality of circumferential fine grooves 12 in the same region S as the example. The width and depth of fine grooves 12 are 0.5 mm, and the interval is 1.2 mm.

Table 1 shows the presence / absence of bear occurrence in the trial production. In Table 1, the durability is determined by using a drum testing machine, mounting on a rim of size 10.5 J × 8, running at an internal pressure of 220 kPa and a longitudinal load of 510 kgf (about 5 kN) at a speed of 80 km / h. It is the result of measuring the distance until a crack occurs, and is represented by an index with Conventional Example 1 being 100, and the larger the number, the better the performance.

  According to Table 1, the tire according to the embodiment of the present invention suppresses the generation of bears without providing a vent hole, so that the trimming operation is unnecessary as in the case of the conventional example 2. Moreover, the durability is improved as compared with Conventional Example 2.

(A) is a figure which shows a part of cross section of the pneumatic tire which concerns on this invention, (b) is a perspective view of the pneumatic tire which concerns on this invention. (A) is a figure which shows the block of the pneumatic tire which concerns on this invention, (b) and (c) are figures which show the cross section of a hollow. (A) And (b) is a figure which shows the shape of another hollow. (A) is a figure which shows the block of the pneumatic tire which concerns on the prior art example 1, (b) is a figure which shows the block of the pneumatic tire which concerns on the prior art example 2. FIG.

Explanation of symbols

1 carcass 2 belt layer 3 tread rubber 4 side rubber 5 joint 6 recess 7 block

Claims (5)

A pair of bead cores, a carcass wound around the bead core to form a toroidal shape, at least one belt layer disposed radially outward of the crown of the carcass, and disposed radially outward of the belt layer In a pneumatic tire provided with a tread rubber and a pair of side rubbers connected to an end portion of the tread rubber from the outer side in the tire axial direction,
A pneumatic tire having a plurality of depressions that are circular in at least 5 mm regions on both sides in the tire radial direction centering on a joint portion of the tire surface between the tread rubber and the side rubber. A pair of bead cores, a carcass wound around the bead core to form a toroidal shape, at least one belt layer disposed radially outward of the crown of the carcass, and disposed radially outward of the belt layer In a pneumatic tire provided with a tread rubber and a pair of side rubbers connected to an end portion of the tread rubber from the outer side in the tire axial direction,
A pneumatic tire provided with a plurality of depressions that are oval extending in the tire radial direction or the tire circumferential direction in at least 5 mm regions on both sides in the tire radial direction centering on the joint portion of the tire surface between the tread rubber and the side rubber . A pair of bead cores, a carcass wound around the bead core to form a toroidal shape, at least one belt layer disposed radially outward of the crown of the carcass, and disposed radially outward of the belt layer In a pneumatic tire provided with a tread rubber and a pair of side rubbers connected to an end portion of the tread rubber from the outer side in the tire axial direction,
In the region of at least 5 mm on both sides in the tire radial direction centering on the joint portion of the tire surface between the tread rubber and the side rubber, the shape is either a rectangle or a polygon including an ellipse, a triangle, a rhombus or a parallelogram, Pneumatic tire with multiple indentations . The pneumatic tire according to any one of claims 1 to 3 , wherein a total surface area of the depressions is 15% or more of an area of a region of 5 mm on both sides in the tire radial direction with the joint portion as a center . The surface area of the recess is 0.5 mm ² ~ 30mm ² The depth of the recess is 0.2 mm to 1.5 mm, the tire circumferential length of the recess is W, the tire radial length is H, and the tire circumferential interval of the recess is 1.1 W to The pneumatic tire according to any one of claims 1 to 4, wherein 3.0 W and a tire radial direction interval are 1.1H to 3.0H.

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