JP2016083819A - Method of manufacturing pneumatic tire, mold for molding tire and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a pneumatic tire which can prevent the appearance defect due to the rubber flow defect based on a vent hole and effectively prevent the deficiency of a tread part caused by a rubber column formed in the vent hole when the vent hole is provided in a blade to form a sipe, a mold for molding the tire, and the pneumatic tire.SOLUTION: There is provided a method of manufacturing a pneumatic tire in which a blade 15 to form a sipe is planted in the inner face of a mold, at least one vent hole 16 penetrating in the thickness direction of the blade 15 is formed on the blade 15, an area S1 of a first opening end 16a of the vent hole 16 which opens in the one face of the blade 15 is set to be larger than an area S2 of a second opening end 16b of the vent hole 16 which opens in the other face of the blade 15, and the distance from the center of the second opening end 16b to the tread face of a tread part is set to be larger than the distance from the center of the first opening end 16a to the tread face of the tread part.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for manufacturing a pneumatic tire having a sipe in a tread portion, a tire molding die used in the manufacturing method, and a pneumatic tire obtained by the manufacturing method, and more specifically, molding a sipe. When a vent hole is provided in the blade, the appearance defect due to the rubber flow failure is prevented based on the vent hole, and the tread portion is effectively prevented from being lost due to the rubber column formed in the vent hole. The present invention relates to a pneumatic tire manufacturing method, a tire molding die, and a pneumatic tire that can be used.

  In order to improve the appearance of a pneumatic tire, vent holes formed on the inner surface of the mold are reduced as much as possible. However, when a large number of sipe forming blades are implanted on the inner surface of the mold, air tends to stay in the space partitioned by the sipe forming blades during vulcanization of the tire, resulting in poor rubber flow in the tread portion of the pneumatic tire. Appearance defects are likely to occur. In order to prevent such appearance defects, it has been proposed to form a vent hole in a sipe forming blade to ensure air permeability between spaces partitioned by the blade (see, for example, Patent Documents 1 to 3). ).

  However, when the sipe forming blade is provided with a vent hole, the rubber column formed in the vent hole needs to be smoothly cut at the time of releasing, but the rubber column is not cut and the vent hole of the blade is not cut. If the mold is released while remaining inside, the tread portion may be lost.

  Particularly in recent years, in order to improve the fuel efficiency of automobiles, rubber compounds with low heat generation are used in the tread portion of pneumatic tires. However, such rubber compounds have low strength as a counter-action. The elongation at break tends to be small. Therefore, in a pneumatic tire that employs this type of rubber compound as a tread rubber compound, the tread portion is more likely to be damaged.

  Further, if the size of the vent hole provided in the sipe forming blade is reduced and the rubber column formed in the vent hole is made thin, the above-described loss of the tread portion can be prevented. However, when the size of the vent hole provided in the sipe molding blade is reduced, the vent hole of the sipe molding blade is likely to be blocked when the rubber flows, and thus there is a problem that the appearance defect cannot be prevented sufficiently. .

Japanese Patent No. 2754036 JP 2002-67042 A JP 2013-75593 A

  An object of the present invention is to prevent a poor appearance due to a poor rubber flow based on the vent hole when a vent hole is provided in a blade for molding a sipe, and to originate from a rubber column formed in the vent hole. An object of the present invention is to provide a pneumatic tire manufacturing method, a tire molding die, and a pneumatic tire that can effectively prevent a tread portion from being damaged.

  In order to achieve the above object, a method for producing a pneumatic tire according to the present invention is to load an unvulcanized tire in a mold and heat the unvulcanized tire while pressurizing it toward the inner surface of the mold. In the manufacturing method of a pneumatic tire in which a pneumatic tire having a sipe in a tread portion is molded, a blade for molding the sipe is implanted in the inner surface of the mold, and the blade is formed in a thickness direction thereof. A second opening end of the vent hole that opens to the other surface of the blade is formed with at least one vent hole that penetrates and has an area S1 of the first opening end of the vent hole that opens to one surface of the blade. The distance d2 from the center position of the second opening end to the tread surface of the tread portion is larger than the distance d1 from the center position of the first opening end to the tread surface of the tread portion. It is characterized in that it has increased.

  Further, a tire molding die of the present invention for achieving the above object is a tire molding die for molding a pneumatic tire having a sipe in a tread portion, and the sipe is molded on the inner surface of the die. And forming at least one vent hole penetrating in the thickness direction of the blade, and defining an area S1 of the first opening end of the vent hole opened on one surface of the blade. It is larger than the area S2 of the second opening end of the vent hole that opens to the other surface, and the distance d2 from the center position of the second opening end to the tread surface of the tread portion is from the center position of the first opening end. It is characterized in that it is larger than the distance d1 to the tread surface of the tread portion.

  Furthermore, the pneumatic tire of the present invention is a pneumatic tire obtained by the method for manufacturing a pneumatic tire described above, and has a rubber column formed in the vent hole on the inner wall surface of the sipe, and the rubber The column is in a state of being cut at the second opening end side of the vent hole.

  In the present invention, by providing a vent hole in a blade for molding a sipe, air permeability between spaces partitioned by the blade based on the vent hole is secured, and appearance defects due to poor rubber flow can be prevented. it can. At this time, by making the area S1 of the first opening end of the vent hole larger than the area S2 of the second opening end, the rubber column formed in the vent hole is formed on the second opening end side of the vent hole when releasing. The distance d2 from the center position of the second opening end to the tread surface is larger than the distance d1 from the center position of the first opening end to the tread surface. Therefore, the rubber pillar is cut at a position relatively far away from the tread surface. Therefore, it is possible to effectively prevent the tread portion from being lost due to the rubber column formed in the vent hole.

  In the present invention, the vent hole preferably has a conical shape. As a result, the rubber column formed in the vent hole is cut off at the second opening end side of the vent hole at the time of releasing and is smoothly separated from the vent hole. Can be prevented.

  Moreover, it is preferable that the area S1 of the first opening end and the area S2 of the second opening end satisfy a relationship of S1 × 0.7 ≧ S2. In this way, by clarifying the magnitude relationship between the area S1 of the first opening end and the area S2 of the second opening end, the rubber column formed in the vent hole is on the second opening end side of the vent hole when the rubber pillar is released. Therefore, it is possible to effectively prevent the tread portion from being lost due to the rubber column.

  Further, the distance d1 from the center position of the first opening end to the tread surface and the distance d2 from the center position of the second opening end to the tread surface t2 are d2−d1 ≧ 0 with respect to the blade thickness t. It is preferable to satisfy the relationship of .5t. Thereby, since the 2nd opening end of a vent hole fully spaces apart from the tread surface of a tread part, the loss of the tread part resulting from a rubber pillar can be prevented effectively.

  The present invention is suitable when a rubber composition having a breaking elongation at 100 ° C. in the range of 200% to 300% after vulcanization is used for a tread portion of a pneumatic tire. Low exothermic rubber compositions generally have a small elongation at break, but when such a rubber composition having a small elongation at break is employed in the tread portion of a pneumatic tire, the tread portion tends to be easily damaged. . In contrast, by adopting the vent hole as described above, it is possible to effectively prevent the tread portion from being lost.

  In the present invention, the elongation at break at 100 ° C. is the rate of deformation in the tensile direction that occurs when the rubber test piece is pulled, and is the percentage (%) of the length at break relative to the original length of the rubber test piece. is there. This breaking elongation is measured according to JIS K6251.

It is sectional drawing which shows an example of the tire vulcanizer used with the manufacturing method of the pneumatic tire of this invention. It is an expanded view which shows an example of the tread pattern of the pneumatic tire obtained by the manufacturing method of the pneumatic tire of this invention. It is sectional drawing which shows the braid | blade implanted by the inner surface of a metal mold | die. It is XX arrow sectional drawing of FIG. It is sectional drawing which shows the sipe shape | molded by the braid | blade of FIG.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an example of a tire vulcanizing apparatus used in the method for producing a pneumatic tire of the present invention. As shown in FIG. 1, the tire vulcanizing apparatus includes a mold 10 for molding a pneumatic tire T. The mold 10 includes a lower side plate 1 and an upper side plate 2 for forming a sidewall portion of the tire T, a lower bead ring 3 and an upper bead ring 4 for forming a bead portion of the tire T, A plurality of sector molds 5 for molding the tread portion of the tire T are provided, and an unvulcanized tire T loaded with the rotation axis in the vertical direction in the cavity is vulcanized and molded. At the time of vulcanization, a rubber bladder 6 formed into a cylindrical shape is inserted inside the tire T.

  The lower end of the bladder 6 is sandwiched between the lower bead ring 3 and the lower clamp ring 7, and the upper end of the bladder 6 is between the upper clamp ring 8 and the auxiliary ring 9 configured to be movable in the vertical direction. It is sandwiched between. Therefore, when the mold is closed, the upper clamp ring 8 is disposed at a lower position as shown in the figure, thereby allowing the bladder 6 to expand. On the other hand, when the mold is opened, the upper clamp ring 8 is moved to the upper position so that the tire T The bladder 6 is pulled out from the inside.

  The tire vulcanizing apparatus is provided with a pressure medium supply means (not shown) for introducing a pressure medium into the bladder 6. The tire T is vulcanized at the time of vulcanization based on the pressure of the pressure medium. The inner surface of the mold 10 is pressed from the inside. As the pressurizing medium, for example, an inert gas such as nitrogen gas or steam can be used.

  On the other hand, a heat source 11 is disposed outside the lower side plate 1, the upper side plate 2, and the sector mold 5. The structure of these heat sources 11 is not particularly limited. For example, a structure in which a cavity is provided inside and a heating medium such as steam is introduced into the cavity can be adopted.

  FIG. 2 shows an example of a tread pattern of the pneumatic tire T obtained by the pneumatic tire manufacturing method of the present invention. As shown in FIG. 2, the tread portion 21 of the pneumatic tire T has a plurality of main grooves 22 extending in the tire circumferential direction, a single circumferential narrow groove 23 extending in the tire circumferential direction, and a tire width direction. A plurality of lug grooves 24 extending and a plurality of sipes 25 extending in the tire width direction are formed.

  In the tire vulcanizing apparatus described above, as shown in FIG. 1, the groove forming bone 12 and the circumferential narrow groove 23 for forming the main groove 22 are formed on the inner surface of the sector mold 5 constituting the mold 10. A groove forming bone 14 for forming a groove forming bone 13 and a lug groove 24 is provided, and a blade 15 for forming a sipe 25 is implanted as shown in FIGS. Yes. The blade 15 is formed with at least one vent hole 16 penetrating in the thickness direction.

  The vent hole 16 has a first opening end 16 a that opens to one surface of the blade 15 and a second opening end 16 b that opens to the other surface of the blade 15. Here, the area S1 of the first opening end 16a of the vent hole 16 is larger than the area S2 of the second opening end 16b of the vent hole 16, and the tread portion 21 extends from the center position of the second opening end 16b. The distance d2 to the tread surface (that is, the mold inner surface S) is larger than the distance d1 from the center position of the first opening end 16a to the tread portion 21 tread surface.

  When the pneumatic tire T is manufactured using the tire vulcanizing apparatus configured as described above, the unvulcanized tire T is loaded into the mold 10, and the unvulcanized tire T is molded by the bladder 6. The pneumatic tire T is molded by heating while pressing toward the inner surface of the tire 10. Thereby, the predetermined groove pattern which consists of the main groove 22, the circumferential direction fine groove 23, and the lug groove 24 is shape | molded by the tread part 21 of the pneumatic tire T after vulcanization based on the groove forming bones 12-14, A predetermined sipe 25 is formed based on the blade 15.

  In the manufacturing method of the pneumatic tire T described above, by providing the vent hole 16 in the blade 15 for forming the sipe 25, air permeability between the spaces partitioned by the blade 15 based on the vent hole 16 is secured. In addition, poor appearance due to poor rubber flow can be prevented. At that time, since the area S1 of the first opening end 16a of the vent hole 16 is larger than the area S2 of the second opening end 16b, the rubber column 26 (see FIG. 5) formed in the vent hole 16 is separated. At the time of forming, the vent hole 16 is preferentially cut on the second opening end 16b side. Moreover, since the distance d2 from the center position of the second opening end 16b to the tread surface of the tread portion 21 is larger than the distance d1 from the center position of the first opening end 16a to the tread surface of the tread portion 21, the rubber column 26 Is cut at a position relatively far from the tread surface of the tread portion 21. Therefore, it is possible to effectively prevent the tread portion 21 from being lost due to the rubber column 26 formed in the vent hole 16.

  Thus, according to the manufacturing method described above, the rubber column 26 corresponding to the vent hole 16 is provided on the inner wall surface of the sipe 25, and the rubber column 26 is cut on the second opening end 16 b side of the vent hole 16. The pneumatic tire T in a state is molded. Such a pneumatic tire T is advantageous in that there are few appearance defects due to poor rubber flow and there are few defects in the tread portion 21 due to the rubber pillars 26 formed in the vent holes 16.

  In the method for manufacturing the pneumatic tire T described above, the shape of the vent hole 16 is preferably a conical shape. When the conical vent hole 16 is formed, the shape of the rubber column 26 formed in the vent hole 16 becomes a conical shape, and the rubber column 26 is cut off at the second opening end 16b side of the vent hole 16 when it is released. As a result, the vent hole 16 is smoothly separated. Therefore, the loss of the tread portion 21 due to the rubber column 26 can be effectively prevented. For example, a conical vent hole 16 can be easily formed in the blade 15 by drilling the blade 15 with a tapered drill along a direction inclined with respect to the normal of one surface of the blade 15. Can do.

  Regarding the vent hole 16 of the blade 15, it is preferable that the area S1 of the first opening end 16a and the area S2 of the second opening end 16b satisfy the relationship of S1 × 0.7 ≧ S2. In this way, by clarifying the size relationship between the area S1 of the first opening end 16a and the area S2 of the second opening end 16b, the rubber column 26 formed in the vent hole 16 can be removed from the vent hole 16 at the time of release. Since the second opening end 16b is preferentially cut, it is possible to effectively prevent the tread portion 21 from being lost due to the rubber column 26. When the ratio S2 / S1 is larger than 0.7, the effect of preferentially cutting the rubber column 26 on the second opening end 16b side of the vent hole 16 is lowered.

Note that it the area S1 of the first opening end 16a is set to 0.25 mm ² ～0.49Mm ^2, the area S2 of the second opening end 16b is set to 0.09mm ² ~0.25mm ^2. Area S1 of the first opening end 16a is likely to occur a deficiency of as large as the tread portion 21 than 0.49 mm ^2, easily occurs a small rubber flow failure than 0.25 mm ² in the opposite. The area S2 of the second opening end 16b is large with tends to occur a defect in the tread portion 21 than 0.25 mm ^2, easily occurs a small rubber flow failure than 0.09 mm ² in the opposite.

  Further, regarding the vent hole 16 of the blade 15, the distance d1 from the center position of the first opening end 16a to the tread surface of the tread portion 21 and the distance d2 from the center position of the second opening end 16b to the tread surface of the tread portion 21 are: The relationship of d2−d1 ≧ 0.5t, more preferably, 2.0t ≧ d2−d1 ≧ 0.5t is satisfied with respect to the thickness t of the blade 15. As a result, the second opening end 16b of the vent hole 16 is sufficiently separated from the tread surface of the tread portion 21, so that the loss of the tread portion 21 due to the rubber column 26 can be effectively prevented. If the difference d2-d1 is smaller than 0.5t, the effect of cutting the rubber column 26 at a position away from the tread surface of the tread portion 21 is reduced. On the other hand, if the difference d2-d1 is larger than 2.0 t, it is difficult to ensure good air permeability between the spaces partitioned by the blade 15.

  The distance d1 from the center position of the first opening end 16a to the tread surface of the tread portion 21 is preferably 0.70 mm to 1.00 mm. If the distance d1 is too small, the tread portion 21 is likely to be lost. Conversely, if the distance d1 is too large, a rubber flow failure is likely to occur.

  The thickness t of the blade 15 is preferably set in the range of 0.5 mm to 1.0 mm. If the thickness t of the blade 15 is smaller than 0.5 mm, the durability of the blade 15 becomes insufficient. Conversely, if the thickness t is larger than 1.0 mm, the workability of the blade 15 is lowered.

  In the pneumatic tire manufacturing method described above, the configuration of the pneumatic tire T is not particularly limited, and in particular, the elongation at break at 100 ° C. after vulcanization of the tread portion 21 of the pneumatic tire T is 200%. It is suitable when a rubber composition in the range of ˜300% is employed. In other words, in order to reduce the rolling resistance of the pneumatic tire T, when a low heat generation rubber composition with a reduced amount of carbon black is used as the tread rubber compound, such a low heat generation rubber composition is used. Tends to reduce elongation at break, and tends to cause defects in the tread portion 21.

  Therefore, when manufacturing a pneumatic tire using a low heat-generating rubber composition in the tread portion, the use of the vent hole 16 as described above can prevent the tread portion 21 from being damaged. Of course, it goes without saying that even when the elongation at break at 100 ° C. is out of the above range, the effect of preventing the tread portion 21 from being lost can be obtained.

  A pneumatic tire in which a tire composition having a tire size of 195 / 65R15 and a rupture elongation at 100 ° C. after vulcanization of 250% is adopted in a tread portion and a groove pattern including sipes is provided in the tread portion. In manufacturing, a vent hole penetrating in the thickness direction is formed in a blade (thickness: 0.6 mm) for forming a sipe, and the shape of the vent hole, the area S1 of the first opening end of the vent hole, Table 1 shows the area S2 of the second opening end of the vent hole, the distance d1 from the center position of the first opening end to the tread surface, and the distance d2 from the center position of the second opening end to the tread surface. Pneumatic tires were obtained by the manufacturing methods of Conventional Example 1, Comparative Examples 1-2, and Examples 1-4 set as described above.

  1,000 pneumatic tires were manufactured by the manufacturing methods of Conventional Example 1, Comparative Examples 1 and 2 and Examples 1 to 4 described above, and occurrence of defects in the tread portion and rubber of the obtained pneumatic tires. The appearance of appearance defects due to flow defects was visually inspected to determine the occurrence rate of defects in the tread portion and the appearance rate of appearance defects. The results are also shown in Table 1. In addition, strict judgment was applied about the defect of a tread part and the appearance defect.

  As is apparent from Table 1, in the manufacturing methods of Examples 1 to 4, in comparison with Conventional Example 1, the occurrence rate of defects in the tread portion and the occurrence rate of appearance defects were significantly reduced. In contrast, while making the area S1 of the first opening end of the vent hole larger than the area S2 of the second opening end of the vent hole, the distance d2 from the center position of the second opening end to the tread surface of the tread portion is set. While Comparative Example 1 was made equal to the distance d1 from the center position of the first opening end to the tread surface, and the area S1 of the first opening end of the vent hole was made equal to the area S2 of the second opening end of the vent hole. In Comparative Example 2 in which the distance d2 from the center position of the second opening end to the tread surface is larger than the distance d1 from the center position of the first opening end to the tread surface, the improvement effect is not necessarily sufficient. There wasn't.

DESCRIPTION OF SYMBOLS 10 Mold 15 Blade 16 Vent hole 16a 1st opening end 16b 2nd opening end 21 Tread part 25 Sipe 26 Rubber pillar T Pneumatic tire

Claims (10)

  An air in which an unvulcanized tire is loaded in a mold, and the unvulcanized tire is heated while being pressed toward the inner surface of the mold to form a pneumatic tire having a sipe in a tread portion. In the method for manufacturing a tire, a blade for molding the sipe is implanted in the inner surface of the mold, and at least one vent hole penetrating in the thickness direction is formed in the blade, and one surface of the blade is formed. The area S1 of the first opening end of the vent hole that opens to the other side of the blade is made larger than the area S2 of the second opening end of the vent hole that opens to the other surface of the blade, and the center position of the second opening end A method for manufacturing a pneumatic tire, characterized in that a distance d2 to the tread surface is larger than a distance d1 from the center position of the first opening end to the tread surface.   The method for manufacturing a pneumatic tire according to claim 1, wherein the vent hole has a conical shape.   3. The method for manufacturing a pneumatic tire according to claim 1, wherein an area S 1 of the first opening end and an area S 2 of the second opening end satisfy a relationship of S 1 × 0.7 ≧ S 2. .   The distance d1 from the center position of the first opening end to the tread surface of the tread portion and the distance d2 from the center position of the second opening end to the tread surface of the tread portion are d2− with respect to the blade thickness t. The method for manufacturing a pneumatic tire according to claim 1, wherein a relationship of d1 ≧ 0.5 t is satisfied.   5. The rubber composition having an elongation at break at 100 ° C. in a range of 200% to 300% after vulcanization is adopted in a tread portion of the pneumatic tire. A method of manufacturing a pneumatic tire.   In a tire molding die for molding a pneumatic tire provided with a sipe in a tread portion, a blade for molding the sipe is implanted on the inner surface of the die, and at least one penetrating in the blade in the thickness direction A vent hole is formed, and the area S1 of the first opening end of the vent hole that opens to one surface of the blade is larger than the area S2 of the second opening end of the vent hole that opens to the other surface of the blade. The tire is characterized in that the distance d2 from the center position of the second opening end to the tread surface is larger than the distance d1 from the center position of the first opening end to the tread surface. Mold for molding.   The tire molding die according to claim 6, wherein the vent hole has a conical shape.   The tire molding die according to claim 6 or 7, wherein an area S1 of the first opening end and an area S2 of the second opening end satisfy a relationship of S1 x 0.7 ≥ S2.   The distance d1 from the center position of the first opening end to the tread surface of the tread portion and the distance d2 from the center position of the second opening end to the tread surface of the tread portion are d2− with respect to the blade thickness t. The tire molding die according to any one of claims 6 to 8, wherein a relationship of d1≥0.5t is satisfied.   It is a pneumatic tire obtained by the manufacturing method of the pneumatic tire according to any one of claims 1 to 5, and has a rubber pillar formed in the vent hole on the inner wall surface of the sipe, and the rubber pillar Is a state where it is cut at the second opening end side of the vent hole.

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