JP2018024142A - Production method for pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method for a pneumatic tire improving a shape stability in the vicinity of a bead part by restraining rubber fluidization at the bead part during vulcanization.SOLUTION: A production method for a pneumatic tire includes setting a molded green tire in the mold of a vulcanizer, inserting a vulcanization bladder in the green tire, and vulcanizing the green tire by expanding the vulcanization bladder. An objective tire production method is characterized by previously plastically deforming a bead part 3 of the green tire into a shape fitting into a space which is composed of a mold and the expanded bladder before setting the green tire in the mold after molding that tire.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for manufacturing a pneumatic tire, and more particularly, to a method for manufacturing a pneumatic tire that suppresses the flow of rubber in a bead portion during vulcanization and improves shape stability in the vicinity of the bead portion.

  A pneumatic tire is manufactured by vulcanizing a green tire formed by combining various unvulcanized tire constituent members in a mold (see, for example, Patent Document 1). At this time, in the tread portion, for example, the unvulcanized rubber flows according to the protrusions for forming the grooves, whereby the pneumatic tire is formed into a desired shape, but the unvulcanized rubber flows in the bead portion. Even if the tire components (for example, bead cores, bead fillers, carcass layers, etc.) are assembled accurately when the green tire is molded, the arrangement may be misaligned, or the green tire may not be pressed sufficiently and unvulcanized. There is a possibility that problems such as rubber slipping on the mold surface and proper vulcanization cannot be achieved. Therefore, there is a demand for a measure for suppressing the flow of rubber in the bead portion during vulcanization and improving the shape stability in the vicinity of the bead portion.

Japanese Patent Laid-Open No. 2003-300212

  The objective of this invention is providing the manufacturing method of the pneumatic tire which suppressed the flow of the rubber | gum in the bead part at the time of vulcanization | cure, and improved the shape stability of the bead part vicinity.

  In order to achieve the above object, the method for producing a pneumatic tire according to the present invention comprises: forming a green tire; then placing the green tire in a mold of a vulcanizer; and vulcanizing bladder in the green tire. In the method of manufacturing a pneumatic tire that is inserted and inflated the vulcanization bladder to vulcanize the green tire, after the green tire is molded and before the green tire is installed in the mold, The bead portion of the green tire is plastically deformed in advance into a shape suitable for a space formed by the mold and the bladder when inflated.

  In the present invention, as described above, the bead portion is plastically deformed into a shape that fits the space formed by the mold and the bladder during expansion, that is, a shape that approximates the tire after vulcanization. Occasionally large-scale flow of unvulcanized rubber can be prevented, and improper deformation of the tire components and the positional relationship between the tire components can be prevented, and the shape stability in the vicinity of the bead portion can be prevented. Can be improved. Further, when the tire to be manufactured is a tire intended for retreading, the shape stability in the vicinity of the bead portion is improved, so that the quality of the base tire is improved, which is advantageous for performing retreading.

  In the present invention, the plastic deformation may be performed by pressing a plurality of rollers having different rotation axes against the bead portion of the green tire.

It is explanatory drawing which shows typically the green tire after the shaping | molding process of the manufacturing method of this invention. It is explanatory drawing which shows typically the bead part of the green tire after the pre-shaving process of the manufacturing method of this invention. It is explanatory drawing which shows the deformation | transformation method of the bead part in the pre-shaving process of the manufacturing method of this invention.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  The manufacturing method of the pneumatic tire of the present invention includes a molding step for molding a green tire, a pre-shaping step for molding a bead portion of the molded green tire into a shape described later, and a bladder in the green tire that has undergone the pre-shaping step. And a shaping step of shaping the entire green tire into a predetermined shape, and a vulcanization step of vulcanizing the green tire that has undergone the shaping step in a mold.

  The method for producing the green tire in the molding step is not particularly limited, and a method generally used in the production of a pneumatic tire can be employed. For example, cylindrical inner liner layer, unvulcanized tie rubber layer, unvulcanized carcass layer, unvulcanized bead filler and bead core, unvulcanized rim cushion rubber layer, unvulcanized side rubber on molding drum A layer is attached to form a cylindrical first molded body, and the first molded body is detached from the molding drum and attached to a shaping drum to apply internal pressure, thereby expanding the first molded body into a toroidal shape. After that, the first molded body expanded in a toroidal shape is pressed against the inner peripheral side of the annular second molded body in which the unvulcanized tread rubber layer is bonded to the outer peripheral side of the unvulcanized belt layer. Thus, a green tire can be formed.

  For example, as shown in FIG. 1, the green tire formed in the forming process includes a tread portion 1 that extends in the tire circumferential direction and forms an annular shape, and a pair of sidewall portions 2 that are disposed on both sides of the tread portion 1. And a pair of bead portions 3 disposed inside the sidewall portion 2 in the tire radial direction. CL in the figure indicates the tire equator. In the illustrated example, an unvulcanized carcass layer 4 is mounted between the pair of left and right bead portions 3. The unvulcanized carcass layer 4 is folded around the unvulcanized bead core 5 disposed in each bead portion 3 from the tire inner side toward the tire outer side. An unvulcanized bead filler 6 is disposed on the outer periphery of the unvulcanized bead core 5. The unvulcanized bead core 5 and the unvulcanized bead filler 6 are wrapped by the main body portion and the folded portion of the unvulcanized carcass layer 4. A plurality of layers (two layers in the illustrated example) of unvulcanized belt layers 7 are embedded on the outer peripheral side of the unvulcanized carcass layer 4 in the tread portion 1. An inner liner layer (not shown) is provided on the tire inner surface.

  At this time, the bead portion 3 has a cross-sectional shape that is substantially half as shown by the solid line in FIG. 1, unlike the cross-sectional shape of the product tire in which the bead toe 3A and the bead heel 3B are clearly formed (broken line in the figure). It has a circular shape. Therefore, in the conventional manufacturing method in which the green tire in this state is vulcanized as it is in the mold without undergoing the pre-shaving step described later, the solid line in the figure shows the vulcanization particularly in the bead portion 3. The unvulcanized rubber flows greatly so as to be deformed from the substantially semicircular cross-sectional shape before vulcanization to the cross-sectional shape of the product tire indicated by the broken line in the figure. As a result, there is a possibility that problems such as displacement of the tire constituent members (bead core 5, bead filler 6, carcass layer 4 and the like) constituting the bead portion 3 may occur. In the present invention, in order to avoid such a problem, a pre-shaving step described later is performed.

  In the pre-shaping step, as shown in FIG. 2, the cross-sectional shape of the bead portion 1 of the green tire formed in the above-described forming step is changed from a substantially semicircular cross-sectional shape (a one-dot chain line in FIG. 2) immediately after forming to a product. It is plastically deformed into a shape (solid line in FIG. 2) that approximates the cross-sectional shape of the tire (broken line in FIG. 2). In other words, it is plastically deformed into a shape suitable for the space formed by the mold used in the vulcanization process described later and the bladder expanded in the vulcanization process. In particular, in the example of FIG. 2, the bead portion 3 is plastically deformed into a shape including three planes (a shape including three sides in the cross-sectional view). In particular, in this example, the bead portion 3 of the green tire that has undergone the pre-shaving process is configured by a plurality of planes, and as a result, corner portions are formed at positions corresponding to the bead toe 3A and the bead heel 3B in the product tire, and the bead toe 3A and the bead heel are formed. The position corresponding to 3B is clear.

  In this way, the pre-shaving process plastically deforms the bead portion 3 into a shape that approximates the product tire (a shape that fits the space formed by the mold and the bladder during expansion). Can prevent large-scale flow of vulcanized rubber, prevents improper deformation of tire components and the positional relationship between tire components, and improves shape stability in the vicinity of bead portion 3 can do.

  The plastic deformation in the pre-shaving step does not need to be performed on the entire bead portion 3, and is preferably performed at least on the region from the bead toe 3A to the bead heel 3B of the vulcanized pneumatic tire. That is, the region from the bead toe 3A to the bead heel 3B is a side that abuts on the mold side rather than the bladder at the time of vulcanization, and the flow of the unvulcanized rubber is likely to occur. It is effective to keep going.

  The method of plastic deformation in the pre-shaving step is not particularly limited as long as the bead portion 3 of the green tire can be plastically deformed into the shape described above. For example, as shown in FIG. 3, a method of pressing a plurality of rollers 10 having different rotation axes against the outer surface of the bead portion 3 of the green tire can be employed. 3 is a schematic diagram for illustrating an example of how to apply the roller 10, and actually includes a mechanism for pressing the roller 10 against the green tire. 3 illustrates plastic deformation by the two rollers 10. For example, three rollers 10 are used to obtain the shape of the bead portion 3 shown in FIG. As a method of plastic deformation, for example, a method of pressing a iron instead of the roller 10 can be adopted.

  The shaping step is a step of molding the entire green tire that has undergone the pre-shaping step into a predetermined shape before vulcanization, and the specific method is not particularly limited, and a method generally used in the manufacture of pneumatic tires. Can be adopted. For example, a bladder is inserted into a green tire that has undergone a pre-shaping step, and the bladder is inflated to mold the entire green tire into a predetermined shape.

  The vulcanization step is a step of vulcanizing the green tire that has undergone the shaping step in a vulcanization mold, and the specific method is not particularly limited, and a method commonly used in the manufacture of pneumatic tires is adopted. can do. In the present invention, in the above pre-shaving step, the bead portion 3 is plastically deformed into a shape that fits the space formed by the vulcanization mold and the bladder during expansion, so any vulcanization method is adopted. Even if it does, it will be hard to produce the large-scale flow of unvulcanized rubber at the time of vulcanization, and it will prevent that an improper deformation of a tire constituent member and a positional relation between tire constituent members collapse in this vulcanization process.

  As described above, in the tire manufactured by the manufacturing method of the present invention, the shape stability in the vicinity of the bead portion 3 is improved. Therefore, the manufacturing method of the present invention can be suitably used for manufacturing tires intended for retreading. That is, in a tire intended for retreading, although the tread portion 1 is replaced, the base tires (sidewall portion 2 and bead portion 3) are repeatedly used, so that the quality of the base tire is required to be good. However, since the tire manufactured by the manufacturing method of the present invention has improved shape stability in the vicinity of the bead portion 3, the quality of the base tire can be improved, which is advantageous for retreading.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 3A Bead toe 3B Bead heel 4 Unvulcanized carcass layer 5 Unvulcanized bead core 6 Unvulcanized bead filler 7 Unvulcanized belt layer 8 Unvulcanized belt cover layer 9 Unvulcanized inner liner layer 10 Roller CL Tire equator

Claims (2)

After forming the green tire, the green tire is placed in a mold of a vulcanizer, a vulcanizing bladder is inserted into the green tire, and the vulcanizing bladder is inflated to vulcanize the green tire. In the manufacturing method of the entering tire,
After the green tire is molded and before the green tire is installed in the mold, the bead portion of the green tire fits into the space formed by the mold and the bladder when inflated. A method of manufacturing a pneumatic tire, wherein the plastic tire is previously plastically deformed.   The method for manufacturing a pneumatic tire according to claim 1, wherein the plastic deformation is performed by pressing a plurality of rollers having different rotation axes against a bead portion of the green tire.

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