JP6003257B2 - Pneumatic tire and manufacturing method thereof - Google Patents

Description

  The present invention relates to a pneumatic tire having a land portion such as a block in a tread portion and a manufacturing method thereof, and more specifically, it is possible to effectively prevent appearance defects due to rubber behavior during vulcanization. The present invention relates to a pneumatic tire and a manufacturing method thereof.

  In the tread portion of the pneumatic tire, land portions such as a large number of blocks defined by grooves are defined. On the other hand, a cavity for molding a land portion such as a block is provided on the inner surface of a mold for molding a pneumatic tire. Since such a cavity forms a substantially closed space, when unvulcanized rubber flows into the cavity in the tire vulcanization process, air is generated in a portion corresponding to an edge portion (particularly a corner portion) of the land portion. It is trapped and vulcanization may be performed in that state. In this case, there is a problem in that the edge of the land portion is partially missing in the product tire and the appearance is deteriorated.

  In order to avoid such an inconvenience, a vent hole communicating with the cavity is generally formed in the mold (see, for example, Patent Documents 1 and 2). By providing the vent hole, the air remaining between the mold and the tire can be discharged to the outside of the mold. However, in recent years, the shape of the land and the characteristics of rubber have been diversified, and the air remaining between the mold and the tire cannot be sufficiently exhausted simply by providing a vent hole. At present, it is not always possible to prevent appearance defects due to rubber behavior at the time.

JP 2004-98815 A JP 2011-168178 A

  An object of the present invention is to provide a pneumatic tire and a method for manufacturing the same that can effectively prevent appearance defects due to rubber behavior during vulcanization.

In order to achieve the above object, a pneumatic tire according to the present invention has a tread portion formed with a plurality of main grooves extending in the tire circumferential direction and a plurality of horizontal grooves extending in the tire width direction, and the tread is formed by the main grooves and the horizontal grooves. In a pneumatic tire that divides a land portion composed of a plurality of blocks in a portion, a chamfered portion is formed at a corner portion forming an acute angle in plan view of the land portion so as to be cut out obliquely, and the land portion the benthos Pugh the shortest distance from the edge of a by該陸portion at the tread surface is formed by a die of the vent hole at a position to be 5mm or less arranged, at least said from the benthos Pew on tread surface of the land portion A small land portion extending to a position adjacent to the chamfered portion is provided, and the height of the small land portion from the tread surface is gradually increased toward the vent spew.

  The method for manufacturing a pneumatic tire according to the present invention for achieving the above object is a method for manufacturing the pneumatic tire, wherein the land portion is formed with a cavity, a vent hole communicating with the cavity, and the small tire. A mold having a small land portion forming groove for forming a land portion is used, an unvulcanized pneumatic tire is introduced into the die, and the pneumatic tire is vulcanized in the die. It is characterized by doing.

  In the present invention, in the pneumatic tire, a vent spew formed by a mold vent hole is disposed at a position on the tread surface of the land portion where the shortest distance from the edge portion of the land portion is 5 mm or less, and A small land extending from the bent spew to the edge of the land is formed on the tread of the land. That is, a pneumatic tire is vulcanized using a mold including a cavity for forming a land portion, a vent hole communicating with the cavity, and a small land portion forming groove for forming a small land portion. Therefore, the air remaining in the vicinity of the edge portion of the land portion during vulcanization can be effectively discharged through the vent hole and the small land portion forming groove. In particular, by gradually increasing the height of the small land portion from the tread toward the vent spew, the small land portion forming groove is effectively prevented from being blocked during vulcanization, and the exhaust path until residual air is discharged. Can be secured. As a result, poor appearance due to rubber behavior during vulcanization can be effectively prevented.

  In the present invention, the small land portion is preferably extended to the corner portion of the land portion. As a result, the air remaining in the vicinity of the corner of the land portion can be reliably discharged, and the appearance defect can be more effectively prevented.

  In forming the small land portion, it is preferable to change the height of the small land portion so that the ridge line of the small land portion forms a curved line or a bent line that protrudes in a direction away from the tread surface. Thereby, a favorable exhaust effect can be obtained while minimizing the volume of the small land portion.

  The maximum width of the small land portion is preferably 1 mm or less. Moreover, it is preferable that the width | variety in the position connected with the vent spew of a small land part shall be 30%-70% of the outer diameter of this vent spew. Furthermore, it is preferable that the maximum height of the small land portion is 0.5 mm to 1.0 mm. Thereby, a favorable exhaust effect can be obtained while avoiding the deterioration of the appearance caused by the small land portion itself.

  The small land portion preferably has a main body portion extending from the vent spew and a pair of branch portions branched from the main body portion, and these branch portions preferably extend to the corner portions of the land portion. Alternatively, the small land portion has a base end portion extending from the bent spew to the edge of the land portion and a tip end portion extending along the edge of the land portion, and the tip portion extends to the corner portion of the land portion. It is preferable. When such a structure is adopted, a good exhaust effect can be ensured.

It is an expanded view which shows an example of the tread pattern of the pneumatic tire of this invention. It is a top view which shows an example (land part provided with the Y-shaped small land part) of the land part divided by the tread part of the pneumatic tire of this invention. The land part provided with the Y-shaped small land part is shown, (a)-(d) is a principal part perspective view which shows a land part, respectively. It is a top view which shows the other example (land part provided with the L-shaped small land part) of the land part divided by the tread part of the pneumatic tire of this invention. The land part provided with the L-shaped small land part is shown, (a)-(c) is a principal part perspective view which shows a land part, respectively. It is a top view which shows the reference example (land part provided with the I-shaped small land part) of the land part divided into the tread part of the pneumatic tire of this invention. It is a principal part perspective view which shows the land part provided with the I-shaped small land part. It is sectional drawing which shows the rubber behavior in the metal mold | die at the time of manufacturing the pneumatic tire of this invention. It is sectional drawing which shows the rubber behavior in the metal mold | die at the time of manufacturing the pneumatic tire corresponded to the comparative example of this invention. It is a principal part side view which shows the land part provided with the small land part which forms the curved line which becomes convex toward the direction in which a ridgeline leaves | separates from a tread. It is a principal part side view which shows the land part provided with the small land part which forms the bending line which becomes convex toward the direction in which a ridgeline leaves | separates from a tread. It is a principal part top view which shows the land part provided with the small land part.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 to 7 show a pneumatic tire according to an embodiment of the present invention. As shown in FIG. 1, a plurality of main grooves 2 extending in the tire circumferential direction and a plurality of lateral grooves 3 extending in the tire width direction are formed in the tread portion 1. The main groove 2 and the lateral groove 3 define a land portion 4 composed of a plurality of blocks in the tread portion 1.

  In the pneumatic tire described above, formed on the tread surface S of each land portion 4 at a position where the shortest distance D (see FIG. 12) from the edge portion 4a of the land portion 4 is 5 mm or less by a vent hole of a mold. A bent spew 10 is arranged. By arranging the vent spew 10 at a position where the shortest distance D from the edge 4a of the land portion 4 is 5 mm or less, the exhaust effect based on the vent hole can be sufficiently secured, and at a position farther than this When the vent spew 10 is arranged, it is difficult to ensure a sufficient exhaust effect.

  In FIG. 2, on the tread S of the land portion 4, a Y-shaped small land portion 11 extending from the bent spew 10 to the edge portion 4a of the land portion 4, specifically, to an acute corner portion 4b is formed. Has been. A chamfered portion 4c is formed in the corner portion 4b so as to cut out the land portion 4 obliquely, and the Y-shaped small land portion 11 extends at least to a position adjacent to the chamfered portion 4c.

  FIGS. 3A to 3D show a land portion having a Y-shaped small land portion. As shown in FIGS. 3A to 3D, the height from the tread surface S of the small land portion 11 gradually increases toward the vent spew 10. That is, the small land portion 11 is gradually lowered as the distance from the vent spew 10 increases. The small land portion 11 has a main body portion 11a extending from the bent spew 10 and a pair of branch portions 11b branched from the main body portion 11a, and these branch portions 11b extend to the corner portions 4b of the land portion 4 respectively. .

  In the example of FIG. 3 (a), the cross-sectional shape of the small land portion 11 is rectangular, but in the example of FIG. 3 (b), the cross-sectional shape of the top portion of the small land portion 11 is arc-shaped. In the example of (c), the cross-sectional shape of the small land portion 11 is a triangle. 3 (a) to 3 (c), the small land portion 11 is formed only on the tread surface S of the land portion 4. In the example of FIG. 3 (d), one branch portion of the small land portion 11 is formed. 11b extends along the chamfered portion 4c.

  In FIG. 4, on the tread surface S of the land portion 4, an L-shaped small land portion 11 extending from the bent spew 10 to the edge portion 4a of the land portion 4, specifically, an acute corner portion 4b is formed. Has been. A chamfered portion 4c is formed in the corner portion 4b so as to cut out the land portion 4 obliquely, and the L-shaped small land portion 11 extends at least to a position adjacent to the chamfered portion 4c.

  5A to 5C show a land portion having an L-shaped small land portion. As shown in FIGS. 5A to 5C, the height from the tread surface S of the small land portion 11 gradually increases toward the vent spew 10. That is, the small land portion 11 is gradually lowered as the distance from the vent spew 10 increases. The small land portion 11 has a proximal end portion 11c extending from the bent spew 10 to the edge portion 4a of the land portion 4 at the shortest distance and a distal end portion 11d extending along the edge portion 4a of the land portion 4, and this distal end portion 11 d extends to the corner 4 b of the land 4.

  In the example of FIG. 5A, one small land portion 11 is formed for one vent spew 10, but in the example of FIG. The small land portion 11 is formed. 5 (a) and 5 (b), the small land portion 11 is formed only on the tread surface S of the land portion 4. In the example of FIG. 5 (c), the tip portion 11d of the small land portion 11 is formed. It branches and extends along the chamfered portion 4c.

  In FIG. 6, an I-shaped small land portion 11 extending from the bent spew 10 to the edge portion 4 a of the land portion 4, specifically, the corner portion 4 b forming an acute angle, is formed on the tread surface S of the land portion 4. Has been. Here, the chamfered portion 4c is not formed in the corner portion 4b, and the I-shaped small land portion 11 extends to the tip of the corner portion 4b.

  FIG. 7 shows a land portion having an I-shaped small land portion. As shown in FIG. 7, the height of the small land portion 11 from the tread surface S gradually increases toward the vent spew 10. That is, the small land portion 11 is gradually lowered as the distance from the vent spew 10 increases.

  FIG. 8 shows the rubber behavior in the mold when manufacturing the pneumatic tire of the present invention, and FIG. 9 shows the rubber behavior in the mold when manufacturing the pneumatic tire corresponding to the comparative example of the present invention. Is shown.

When manufacturing a pneumatic tire provided with the vent spew 10 on the tread S of the land portion 4 and the small land portion 11 extending from the vent spew 10 to the edge portion 4a of the land portion 4 as described above, it is shown in FIG. As described above, a mold 20 having a cavity 21 for forming the land portion 4, a vent hole 22 communicating with the cavity 21 , and a small land portion forming groove 23 for forming the small land portion 11 is used. An unvulcanized pneumatic tire is put into the mold 20, and the pneumatic tire is vulcanized in the mold 20. When the pneumatic tire is pressed against the inner surface of the mold 20 during vulcanization, the unvulcanized rubber R is gradually filled into the cavity 21. At that time, as shown in FIG. 8, the air remaining in the vicinity of the edge 4 a (particularly the corner 4 b) of the land portion 4 is effectively discharged through the vent hole 22 and the small land portion forming groove 23. Here, the height of the small land portion 11 from the tread S is gradually increased toward the vent spew 10, in other words, the depth of the small land portion forming groove 23 is gradually increased toward the vent hole 22. It is possible to effectively prevent the small land portion forming groove 23 from being blocked at the time of sulfuration, and to secure an exhaust path until residual air is discharged. As a result, poor appearance due to rubber behavior during vulcanization can be effectively prevented.

  On the other hand, as shown in FIG. 9, when the height from the tread surface S of the small land portion 11 is made constant, in other words, when the depth of the small land portion forming groove 23 is made constant, the residual air is sufficiently discharged. The portion close to the vent hole 22 of the small land portion molding groove 23 was previously blocked by the unvulcanized rubber R, and the exhaust path for residual air was blocked. Therefore, if the height from the tread S of the small land portion 11 is constant, the exhaust effect cannot be sufficiently obtained.

  In forming the small land portion 11 described above, it is desirable to adopt a structure as shown in FIGS. That is, it is preferable to change the height of the small land portion 11 so as to form a curved line (FIG. 10) or a bent line (FIG. 11) in which the ridge line of the small land portion 11 protrudes in the direction away from the tread surface S. . When the ridge line of the small land portion 11 forms a curved line or a bent line that protrudes in the direction away from the tread surface S in this way, in view of the behavior of the unvulcanized rubber R described above, the small land portion A good exhaust effect can be obtained while minimizing the volume of 11. Although the exhaust effect can be enhanced by increasing the volume of the small land portion 11, the small land portion 11 is arranged on the tread S of the land portion 4, so that it is as much as possible considering generation of pattern noise and the like. Small is desired.

  Furthermore, it is desirable to set the maximum height Hmax of the small land portion 11 in the range of 0.5 mm to 1.0 mm. Thereby, the favorable exhaust effect can be acquired, avoiding the deterioration of the external appearance resulting from the small land part 11. FIG. If the maximum height Hmax of the small land portion 11 is less than 0.5 mm, the exhaust effect is reduced, and conversely if it exceeds 1.0 mm, the appearance is deteriorated.

  As shown in FIG. 12, it is desirable to set the maximum width Wmax of the small land portion 11 to 1 mm or less. Thereby, the favorable exhaust effect can be acquired, avoiding the deterioration of the external appearance resulting from the small land part 11. FIG. If the maximum width Wmax of the small land portion 11 exceeds 1.0 mm, the appearance is deteriorated.

  Further, it is desirable that the width W at the position where the small land portion 11 is connected to the vent spew 10 is set in a range of 30% to 70% of the outer diameter φ of the vent spew 10. Thereby, the favorable exhaust effect can be acquired, avoiding the deterioration of the external appearance resulting from the small land part 11. FIG. When the width W of the small land portion 11 is smaller than 30% of the outer diameter φ of the vent spew 10, the exhaust effect is lowered. Conversely, when the width W is larger than 70%, the appearance is deteriorated. Although FIG. 12 depicts a case where the width W of the small land portion 11 connected to the vent spew 10 is substantially the same as the maximum width Wmax of the small land portion 11, the vent spew of the small land portion 11 is depicted. The width W at the position connected to 10 may be smaller than the maximum width Wmax of the small land portion 11.

  The pneumatic tire described above may be provided to the market with the bent spew 10 formed on the tread portion 1 as it is, or may be provided to the market with the bent spew 10 trimmed. Since the small land portion 11 has a small volume, it is not particularly necessary to consider the trimming.

  In a pneumatic tire with a tire size of 185 / 60R15 and a land portion divided into a tread portion, a mold vent hole on the tread surface at a position where the shortest distance D from the edge portion of the land portion is 5 mm. The vent spew is formed by a small land that extends from the vent spew to the corner of the land, and the height structure of the small land, the ridge shape of the small land, Example 1 in which the maximum width Wmax of the land portion, the width W (ratio to the outer diameter φ of the vent spew) at the position connected to the vent spew of the small land portion, and the maximum height Hmax of the small land portion are set as shown in Table 1. To 11 and Comparative Example 1 were manufactured. Moreover, the tire of the prior art example 1 which has the same structure as Examples 1-11 and the comparative example 1 was prepared except not attaching the small land part with respect to vent spew for the comparison.

  Regarding the height structure of the small land part, the case where the height from the tread part of the small land part is constant over the entire length is indicated as “constant”, and the height from the tread part of the small land part is gradually increased toward the vent spew. The case is shown as “gradual increase”. About the ridgeline shape of the small land part, when the ridgeline of the small land part forms a bending line that protrudes toward the tread, the direction in which the ridgeline of the small land part moves away from the tread The case of forming a bent line that is convex toward the top is indicated by “convex upward”, and the case where the ridgeline of the small land portion forms a straight line is indicated by “linear”.

  About these test tires, the external appearance after vulcanization was evaluated by the following evaluation method, and the results are also shown in Table 1.

Appearance after vulcanization:
After 100 test tires were vulcanized one by one, the occurrence locations of appearance defects in the vulcanized tires were examined, and the total number of appearance failure locations for each test tire was determined. The evaluation results are shown as an index with the conventional example 1 as 100, using the reciprocal of the measured value. A larger index value means fewer appearance defects.

  As can be seen from Table 1, the tires of Examples 1 to 11 had fewer appearance defects in comparison with Conventional Example 1. In particular, when Examples 1 to 3 are compared, it can be seen that the best results are obtained when the ridgeline of the small land portion forms a bent line that protrudes in the direction away from the tread. Further, comparing Examples 3 to 5, it can be seen that when the maximum width Wmax of the small land portion exceeds 1.0 mm, the effect of improving the appearance defect is saturated and the small land portion is simply enlarged. Further, in contrast to Examples 3 and 6 to 8, when the width W at the position connected to the vent spew in the small land exceeds 0.7φ, the effect of improving the appearance defect is saturated, and the small land is simply enlarged. It turns out that it is. Further, comparing Examples 3 and 9 to 11, it can be seen that when the maximum height Hmax of the small land portion exceeds 1.0 mm, the effect of improving the appearance defect is saturated and the small land portion is simply enlarged. .

  In contrast, the tire of Comparative Example 1 has a small land portion connected to the vent spew on the tread surface of the land portion, but does not change the height of the small land portion from the tread surface along the longitudinal direction. Therefore, the effect of improving the appearance defect could not be obtained. In other words, it was recognized that increasing the height of the small land from the tread gradually toward the bent spew was significant.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Main groove 3 Horizontal groove 4 Land part 4a Edge part 4b Corner | angular part 4c Chamfering part 10 Vent spew 11 Small land part 11a Main body part 11b Branch part 11c Base end part 11d Tip part 20 Mold 21 Cavity 22 Vent hole 23 Small Land forming groove S Tread

Claims (8)

A pneumatic tire in which a plurality of main grooves extending in the tire circumferential direction and a plurality of horizontal grooves extending in the tire width direction are formed in the tread portion, and a land portion composed of a plurality of blocks is defined in the tread portion by the main grooves and the horizontal grooves. A chamfered portion is formed so as to cut out the land portion obliquely at a corner portion forming an acute angle in plan view of the land portion, and the shortest distance from the edge portion of the land portion on the tread surface of the land portion A vent spew formed by a vent hole of a mold is disposed at a position where the distance is 5 mm or less, and a small land portion extending from the vent spew to at least a position adjacent to the chamfered portion is provided on the tread surface of the land portion, A pneumatic tire characterized in that the height of the small land portion from the tread is gradually increased toward the vent spew. According to claim 1, characterized in that the ridge line of the small land portion is the changing the height of the small land portion to form a curved line or bent line is convex toward the direction away from the tread surface Pneumatic tire. The pneumatic tire according to any one of claims 1-2, characterized in that the maximum width of the small land portion and 1mm or less. The pneumatic tire according to any one of claims 1 to 3 , wherein a width of the small land portion at a position connected to the vent spew is set to 30% to 70% of an outer diameter of the vent spew. The pneumatic tire according to any one of claims 1 to 4 , wherein a maximum height of the small land portion is set to 0.5 mm to 1.0 mm. The said small land part has a main-body part extended from the said vent spew, and a pair of branch part branched from this main-body part, These branch parts are each extended to the corner | angular part of the said land part. The pneumatic tire according to any one of 1 to 5 . The small land portion has a base end portion extending from the bent spew to an edge portion of the land portion and a tip end portion extending along the edge portion of the land portion, and the tip portion is a corner portion of the land portion. The pneumatic tire according to any one of claims 1 to 5 , wherein the pneumatic tire is extended to. A method for manufacturing the pneumatic tire according to any one of claims 1 to 7 , wherein a cavity for forming the land portion, a vent hole communicating with the cavity, and a small land portion forming groove for forming the small land portion. A pneumatic tire is characterized in that an unvulcanized pneumatic tire is introduced into the mold, and the pneumatic tire is vulcanized in the mold. Production method.

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