JP4608986B2 - Pneumatic tire manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a pneumatic tire, and more particularly, to a method for manufacturing a pneumatic tire in which air accumulation between an unvulcanized tire and a bladder generated during tire vulcanization molding is improved.

  The vulcanization of the pneumatic tire is performed by inflating the bladder from the inside of the unvulcanized tire set in the mold and pressing the unvulcanized tire against the inner surface of the mold by the expansion pressure. In such a vulcanization process, if air stays between the bladder and the unvulcanized tire, a vulcanization failure may occur due to the heat insulating action of the air. In order to prevent such a vulcanization failure, in the conventional vulcanization molding machine, a large number of grooves are provided along the radial direction on the surface of the bladder, and air is discharged to the outside along these grooves. (Patent Document 1, etc.).

However, it is difficult to secure a sufficient air discharge amount simply by providing a groove on the surface of the bladder. For this reason, if an attempt is made to secure a sufficient air discharge amount by increasing the groove depth, for example, the deep groove becomes a bladder. When inflated, it moves relative to the surface of the unvulcanized tire and scrapes a part of the surface to deteriorate the appearance of the inner wall of the tire, and further, vulcanization failure occurs due to the gradual accumulation of rubber residue and mold release agent at the groove bottom. There was a problem of causing.
JP 2002-137227 A

  The objective of this invention is providing the manufacturing method of the pneumatic tire which eliminates the air accumulation of the contact interface of a bladder and an unvulcanized tire, and prevents a vulcanization failure.

The pneumatic tire manufacturing method of the present invention to achieve the above object, the thermoplastic resin or thermoplastic resin / elastomer comprising the composition innerliner one surface is a bladder side, and that is thicker uneven thickness than the adjacent portion the Rukoto provided a number of ridges or independent projections with height in the range of 0.05 to 1.0 mm,. 5 to an area percentage of said inner liner surface therebetween of said multiple ridges or independent projection An unvulcanized tire having an air guide path of 50% is made, and the unvulcanized tire is pressed against the inner surface of a mold by expansion of a bladder and vulcanized.

In order to obtain a greater effect of the present invention, an inner liner composed of a thermoplastic resin or a thermoplastic resin / elastomer composition, also bladder good those surface unevenness difference is less smooth 0.5 mm.

  According to the present invention, by providing a protrusion or an independent protrusion that is thicker than the adjacent portion on the inner liner side of the unvulcanized tire, the protrusion or the independent protrusion is crushed by the pressing force of the bladder. In order to ensure a sufficient clearance between the bladder and the air, and to secure a sufficient amount of air discharge, it is possible to eliminate air accumulation at the contact interface between the bladder and the inner liner and prevent vulcanization failure.

In the method of the present invention, since the inner liner was configured from a thermoplastic resin or a thermoplastic resin / elastomer composition, the rigidity of the projection or independent projections than in the unvulcanized rubber is increased, the The effect of can be greatly obtained . Moreover, when using a thing with high smoothness whose surface unevenness | corrugation difference is 0.5 mm or less as a bladder, the said effect can be improved further.

  In the present invention, the vulcanization molding of a pneumatic tire is performed by setting an unvulcanized tire having an inner liner as an innermost layer in a mold and inflating a bladder from the inside of the unvulcanized tire. An unvulcanized tire is pressure-bonded to the inner surface, and in this state, heating is performed from both the mold side and the bladder side.

  In the present invention, the pneumatic tire may be either a radial tire or a bias tire, and is not particularly limited as long as an inner liner is provided as an air seal layer on the innermost side.

  As the unvulcanized tire before being set in the mold, a tire provided with a large number of protrusions or independent protrusions on the surface of the inner liner is used. In the case of a large number of protrusions, an air guide path is formed between adjacent protrusions. In the case of a large number of independent protrusions, an air guiding path can be formed between the adjacent independent protrusions. These air guide paths are preferably configured such that the end portions thereof pass out to the inner diameter side of the bead portion. Only one of the protrusions and the independent protrusions may be provided, or both may be provided simultaneously.

  Both the protrusions and the independent protrusions provided on the surface of the inner liner need to have an uneven thickness structure that is thicker than the adjacent portion. By making the protrusions and independent protrusions thicker than the periphery, the rigidity of the protrusions and independent protrusions increases, so even if a large pressing force is applied due to the expansion of the bladder during the vulcanization process. Since it is not easily crushed and an air guide path is secured, air discharge performance can be improved.

In the present invention, the material constituting the inner liner is a thermoplastic resin or a thermoplastic resin / elastomer composition . Thermoplastic resins and thermoplastic resin / elastomer compositions have the property of low air permeability and are not in a plastic state like unvulcanized rubber when they are applied as an inner liner of an unvulcanized tire. Since it is in a non-plastic state, the location of the protrusions and independent protrusions can be combined with the above-described uneven thickness structure to further improve the deformation resistance, and the air discharge performance can be further improved.

  The type of thermoplastic resin and the type of elastomer blended with the thermoplastic resin are not particularly limited as long as they have moldability. For example, examples of the thermoplastic resin include nylon resin, polyester resin, polynitrile resin, polymethacrylate resin, polyvinyl resin, cellulose resin, fluorine resin, and imide resin. Examples of the elastomer include diene rubber and its additives, olefin rubber, halogen-containing rubber, silicone rubber, sulfur-containing rubber, and fluorine rubber.

In the present invention, the height of the protrusions or independent protrusions formed on one surface on the bladder side of the inner liner is in the range of 0.05 to 1.0 mm . If it is lower than 0.05 mm, it is difficult to ensure sufficient air discharge performance. On the other hand, if the height is higher than 1.0 mm, the air dischargeability is sufficient, but the amount of discharged air increases, so that the remaining air causes a vulcanization failure.

Further, it is important that the area ratio of the air guide path formed between the protrusions or the independent protrusions on the inner liner surface is in the range of 5 to 50% . If it is less than 5%, it is difficult to ensure sufficient air discharge performance. Further, if it exceeds 50%, the amount of air to be discharged also increases, and there is a problem that vulcanization failure is caused by the remaining air.

  In the case of a ridge, it is preferable that the angle θ of the ridge with respect to the tire meridian direction is 0 to 85 °. When the angle θ is larger than 85 °, the distance of the air guide path increases, the exhaust resistance increases, and the air discharge performance decreases.

  In the present invention, it is preferable that the bladder used in the vulcanization molding machine has a surface as smooth as possible. As the smoothness, the surface roughness difference (height difference between the concave and convex portions adjacent to each other) on the surface is preferably 0.5 mm or less, more preferably less than 0.1 mm. Is good. If the unevenness difference on the bladder surface becomes large, the bladder may scrape off the surface of the unvulcanized tire or accumulate rubber residue or a release agent in the recess to cause a vulcanization failure.

  FIG. 1 illustrates an unvulcanized tire used in the production method of the present invention.

  In the unvulcanized tire 1, 2 is a tread portion, 3 is a sidewall portion, and 4 is a bead portion. The carcass layer 5 is inserted in the entire inside of the tire. The carcass layer 5 has both end portions folded around the bead core 6 from the inner side to the outer side of the tire, two belt layers 7 are arranged on the outer periphery, and an inner liner 8 is provided as a sealing layer on the inner side.

As shown in FIGS. 2 and 3, the inner liner 8 is formed so as to have a large number of protrusions 9 on one surface on the bladder side . These ridges 9 are characterized in that they are formed to be thicker than the adjacent grooves 10 and have an uneven thickness structure .

  The ridge 9 formed in this way is formed so that the angle θ with respect to the tire meridian direction M is 0 ° to 85 ° (see FIG. 2), and its extended end is outside the inner liner end of the bead portion 4. It comes to come out. Further, the height of the protrusion 9 (and hence the depth of the groove 10) is 0.05 to 1.0 mm, respectively, and the air guide path by the groove 10 excluding the top surface of the protrusion 9 occupies the inner liner surface. The area ratio is 5 to 50%.

In the green tire 1, each part has been configured with unvulcanized rubber, the inner liner 8 is composed of a thermoplastic resin or a thermoplastic resin / elastomer composition.

In the vulcanization molding of the unvulcanized tire 1 molded as described above, the unvulcanized tire 1 is set in the mold 20 as shown in FIG. 4 and heated gas is supplied to the bladder 21. The unvulcanized tire 1 is inflated and pressed against the inner surface of the mold 20. In the expansion process of the bladder 21, the inner liner 8 on the inner surface of the unvulcanized tire 1 is provided with a large number of protrusions 9, so that the air guide path of the groove 10 is maintained at the contact interface with the bladder 21. To do. In addition, since the uneven rib 9 has rigidity, the air guide path (groove 10) is maintained without being easily crushed by the pressing force of the bladder 21. Therefore, most of the air to be trapped between the bladder 21 and the inner liner 8 is discharged from the end of the bead portion to the outside of the tire via the air guide path (groove 10) and becomes an air pool. There is no.

  Therefore, vulcanization without vulcanization failure is achieved by supplying heated gas to the bladder 21 while maintaining the above-mentioned pressed state and applying heating energy to the mold 20 to heat the unvulcanized tire 1 from inside and outside. Can be completed. As the bladder at this time, it is preferable to use a highly smooth bladder having a surface unevenness difference of 0.5 mm or less, whereby a product tire having a further improved inner surface appearance and no vulcanization failure can be obtained.

  The tire size is the same as 195 / 65R15, and the ridges as shown in FIGS. 2 and 3 on the inner liner surface (the ridge height is 0.2 mm, the ridge angle θ = 0 °, the groove portion excluding the ridge An unvulcanized tire having an area ratio of 10%) and an unvulcanized tire having an inner liner with a smooth inner surface without such protrusions were molded.

  The two types of unvulcanized tires were each vulcanized using a vulcanization molding machine having a grooved bladder and a vulcanization molding machine having a smooth surface bladder without grooves.

  The four types of product tires after vulcanization were examined for the presence or absence of vulcanization failure and the roughness of the internal appearance, and the results shown in Table 1 were obtained.

It is a meridian half section view which illustrates the unvulcanized tire used for the manufacturing method of the present invention. It is an arrow view when it sees with the arrow A in FIG. It is sectional drawing of the arrow BB in FIG. It is sectional drawing which illustrates the vulcanization molding machine used for implementation of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Unvulcanized tire 2 Tread part 3 Side wall part 4 Bead part 5 Carcass layer 8 Inner liner 9 Projection 10 Groove 20 Mold 21 Bladder

Claims (3)

The inner liner made of a thermoplastic resin or a thermoplastic resin / elastomer composition has one surface on the bladder side that is thicker than the adjacent portion and has a height in the range of 0.05 to 1.0 mm . the Rukoto provided projections or independent projections, making the unvulcanized tire to form the air guide path 5 to 50% by area percentage of the inner liner surface therebetween of said multiple ridges or independent projection A method for producing a pneumatic tire, characterized in that the unvulcanized tire is pressed against the inner surface of a mold by expansion of a bladder and vulcanized. The manufacturing method of the pneumatic tire of Claim 1 which made the surface of the said bladder the smooth surface whose unevenness | corrugation difference is 0.5 mm or less. The method for manufacturing a pneumatic tire according to claim 1 or 2, wherein an angle of the protrusion with respect to a tire meridian direction is 0 to 85 °.

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