JP2008127710A - Method for finishing ply cord, method for producing pneumatic tire by using the ply cord finished by the finishing method, and the pneumatic tire produced by the production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for finishing a ply cord by which the engaging force between the ply cord and a bead core can be improved, a method for producing a pneumatic tire using the ply cord finished by the finishing method, and the pneumatic tire produced by the production method and having excellent durability of the bead part. <P>SOLUTION: The method for finishing the ply cord (3) constituting the pneumatic tire includes a step for covering a metal cord with a rubber, a step for cutting the rubber-coated cord into a prescribed length, a step for arranging both end parts of the cut cord into a molding die (1), and a step for plastically deforming both ends of the cord into prescribed shapes by extracting the cord from the molding die while pushing a part of the outer periphery of the cord by a pressing member (2) arranged in the molding die (1). The method for producing the pneumatic tire by using the ply cord (3) finished by the finishing method, and the pneumatic tire produced by the production method are also provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for processing a ply cord constituting a carcass ply of a pneumatic tire, a method for manufacturing a pneumatic tire using a ply cord processed by the processing method, and a pneumatic tire manufactured by the manufacturing method. Therefore, the durability of the bead portion of the pneumatic tire is improved.

  A pneumatic tire includes a pair of bead portions, a pair of sidewall portions, a tread portion, and a carcass ply including a ply cord that reinforces them. Generally, a bead portion includes at least one layer of a carcass ply. The bead core embedded in the portion has a folded portion that winds up around the bead core from the inside in the tire radial direction toward the outside. However, in this type of carcass ply, the folded end portion of the folded portion is disposed in a region that is easily deformed, so that stress tends to concentrate on the folded end portion of the carcass ply during tire load rolling, and rigidity With the different tire configurations, cracks occur between the rubber and the folded end of the carcass ply, and the separation between the folded end and the rubber is likely to occur, and resists the tensile force of the carcass on the outer side in the tire radial direction. Since the locking force to be reduced also decreases, the carcass ply may be pulled out.

  Therefore, in Patent Document 1, by winding the carcass ply around the bead core, the folded end portion of the carcass ply is arranged in a region with less distortion of the bead portion, and the occurrence of cracks from the folded end portion is prevented, The winding of the carcass ply around the bead core becomes a locking force against the tensile force of the carcass ply outward in the tire radial direction when the tire rolls, causing the carcass ply to pull out from the bead part. Difficult pneumatic tires have been proposed.

  However, on the other hand, the tire having the carcass structure described in Patent Document 1 requires manpower until vulcanization molding, and is not fully labor-saving and labor-saving, and is fully automatic for the near future. It becomes an obstacle. For this reason, in Patent Document 2, in each bead portion, by wrapping the inner end portion in the tire radial direction of the carcass ply between the pair of bead cores, the winding of the carcass ply around the bead core is omitted, There has been proposed a tire suitable for fully automatic molding that can simplify the manufacturing process and sufficiently achieve labor saving and labor saving. Further, since the end portion of the carcass ply is disposed on the inner side in the tire radial direction of the bead core, the tire described in Patent Document 2 prevents separation from the rubber without concentrating stress on the end portion of the carcass ply. It is possible.

  The tire described in Patent Document 2 can be manufactured using, for example, the apparatus described in Patent Document 3, thereby eliminating the need to prepare tire components such as a carcass ply and a reinforcing belt for each tire having a different size. The manufacturing process can be made more efficient and space can be saved.

JP 2001-191758 A Japanese Patent Laid-Open No. 2002-12011 JP 2004-122626 A

  The tire described in Patent Literature 2 holds the carcass ply between the pair of bead cores, thereby locking the carcass ply to the bead portion. However, a large load is applied to the carcass ply, particularly like a heavy load tire. In some cases, the locking force for locking the carcass ply may not be sufficient only by the sandwiching effect by the bead core, and there is a possibility that the pull-out at the time of tire load rolling cannot be prevented sufficiently. In Patent Document 2, the end of the carcass ply is bent so as to cover the bead core on the inner side in the tire width direction, so that the locking force against pulling out at the time of tire load rolling is also improved. There is a possibility that it is not sufficiently improved. Furthermore, since the operation of a bladder or the like is required to bend the end portion of the carcass ply, there is a disadvantage that the manufacturing process becomes complicated.

  Accordingly, an object of the present invention is to provide a method for processing a ply cord capable of improving a locking force with a bead core, a method for manufacturing a pneumatic tire using a ply cord processed by the processing method, and a method for manufacturing the same. An object of the present invention is to provide a pneumatic tire excellent in durability of a bead portion manufactured by the above method.

In order to achieve the above object, a first invention is a method of processing a ply cord constituting a carcass ply of a pneumatic tire, the step of coating a metal cord with rubber, and the rubber-coated cord with a predetermined length Cutting the cord, pulling out the cord from the molding die while pressing a part of the outer peripheral surface of the cord with a pressing member disposed in the molding die. Thus, the ply cord processing method includes a step of plastically deforming both ends of the cord into a predetermined shape. With this processing method, both end portions of the ply cord can be easily plastically deformed, so that a manufacturing process of winding a bead core using a bladder can be omitted. In addition, since the plastically deformed end portion improves the locking force to prevent pull-out from the bead portion, it is possible to provide a ply cord that is suitable for fully automatic molding but can sufficiently prevent pull-out. It becomes. Each end portion of the ply cord is preferably in the range of 1 to 10% of the total cord length.

  Further, it is preferable to pull out the cord from the forming die while pressing about a half circumference of the outer circumference of the cord. Here, “about half circumference” means 30 to 50% of the circumferential length of the outer circumference of the cord.

  Furthermore, it is preferable to plastically deform both ends of the cord in a spiral shape. Here, the “spiral shape” refers to a curved shape that is spirally wound in a plan view.

  In the second invention, an inner bead core is disposed in the bead portion of the rigid core, and a ply cord is attached to the outer periphery of the inner bead core in the tire width direction along the axial direction on the outer peripheral surface of the rigid core. The outer bead core is disposed on the outer side of the ply cord in the tire width direction so as to sandwich the ply cord together with the inner bead core, and the tire is added by attaching tread rubber, other reinforcing members and rubber members on the outer peripheral surface thereof. At the time of molding, the ply cord processed by using the above-described processing method in each bead portion is such that the plastically deformed end portion is inside the tire radial direction inner side of the bead core in the tire radial direction. It is a manufacturing method of a pneumatic tire characterized by arranging in. At this time, the distance in the tire width direction of the end portion of the ply cord that is plastically deformed is preferably larger than the distance in the tire width direction between the pair of bead cores. Compared to the case where the end of the carcass ply is straight, the tire manufactured by such a manufacturing method has a greater resistance force when the end passes between the bead cores when rolling the tire load, and the force required for pulling out is increased. Since it increases, it becomes difficult for the carcass ply to be pulled out. In addition, if the distance in the tire width direction of the end portion of the ply cord that has been plastically deformed is larger than the distance in the tire width direction between the bead cores, even if the carcass ply is pulled outward in the tire radial direction during tire load rolling, the plasticity Since the end portion of the deformed ply cord is caught by the bead core, the locking force of the carcass ply to the bead portion can be further improved, and the carcass ply can be effectively prevented from being pulled out. Here, “the innermost end of the bead core in the tire radial direction” refers to the innermost position of the bead core in the tire radial direction.

  3rd invention is a pneumatic tire manufactured using said manufacturing method of a pneumatic tire.

  According to the present invention, a method for processing a ply cord capable of improving the locking force with a bead core, a method for manufacturing a pneumatic tire using a ply cord processed by the processing method, and a method for manufacturing the same It becomes possible to provide a pneumatic tire excellent in durability of the manufactured bead part.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 show a forming die for processing a typical ply cord according to the present invention, and FIG. 3 shows an end portion of the ply cord processed by the forming die and a ply cord portion in the vicinity thereof. ing. FIG. 4 is a cutaway perspective view of a bead portion of a pneumatic tire (hereinafter referred to as “tire”) using such a ply cord, and FIG. 5 is a left half sectional view of the tire shown in FIG. 4 in the width direction.

In the method for processing a ply cord of a pneumatic tire according to the present invention, a metal cord is covered with rubber, and the rubber-coated cord is cut to such a length that it can straddle between both bead portions. Next, the molding die 1 that can be divided into upper and lower parts shown in FIG. 1 and FIG. 2 is opened by dividing it into two parts in the upper and lower parts, and both ends of the cut cord are arranged and closed on the molding die 1. The cord is pulled out of the molding die 1 while pressing a part of the outer peripheral surface of the cord with the pressing member 2 disposed in the molding die 1. As a result, distortion is generated mainly by shear deformation on the side where the force is applied by pressing, and both ends of the cord are plasticized into a geometric shape that improves the locking force that resists pulling out from the bead. Deform. With such a processing method, both ends of the ply cord can be easily plastically deformed, and a conventional manufacturing process such as winding around a bead core can be omitted, so that labor saving and labor saving are sufficiently achieved. It becomes possible to provide a ply cord suitable for fully automatic molding. At this time, the cord is not an organic fiber cord such as a polyester cord, a nylon cord, or a rayon cord, but a metal cord such as a steel cord is preferable in order to maintain the plastically deformed form at both ends of the ply cord. Because. In this embodiment, a plurality of ballpoint pen nib-shaped pressing members 2 each including a ball and a pedestal on which the ball is placed are disposed in the molding die 1, and the cord is disposed in the molding die 1. When the ball is pulled out, the ball rotates to reduce the coefficient of friction of the pressed portion, so that the cord can be plastically deformed without damaging the rubber surface of the cord. The molding die 1 shown in FIGS. 1 and 2 is an embodiment according to the present invention, and it is possible to change the size and the like of the inner diameter according to the shape of the rubber-coated cord.

  Further, it is preferable to pull out the cord from the forming die 1 while pressing the pressing member 2 about half of the outer periphery of the cord. Because, since the cord is processed by pressing about half of the outer circumference of the cord against the pressing member 2 and pulling it out, both ends of the cord can be pulled out at the same time, so the end of the cord is processed one by one This is because the time required for processing the cord can be shortened, and the manufacturing process can be labor-saving and labor-saving. At this time, the end of the carcass cord can be formed in various desired shapes by adjusting the pressing force and the direction of the cord.

  Furthermore, as shown in FIG. 3, it is preferable to plastically deform both ends 4 of the ply cord 3 in a spiral shape. This is because, by making the both ends 4 of the ply cord 3 spiral, when the tire rolls, both the spiral ends of the carcass ply constituted by the ply cord 3 are pulled outward in the tire radial direction. This is because it exerts a locking force that resists this, so that the carcass ply is less likely to be pulled out from the bead portion, and the durability of the bead portion may be improved.

  Next, a tire manufacturing method using the ply cord 3 processed in this way will be described.

  The tire manufacturing method according to the present invention can be carried out, for example, using an apparatus basically similar to the apparatus described in Patent Document 3. 6 to 8 show a part of the detailed manufacturing process of the tire according to the present invention. First, as shown in FIG. 6, the inner bead core 5 formed in a ring shape is disposed on the rigid core 8. Next, as shown in FIG. 7, on the rigid core 8 and the inner bead core 5, the end portion 4 of the ply cord protrudes inwardly in the tire radial direction from the innermost end 7 in the tire radial direction of the inner bead core. The ply cord 3 is attached over the entire circumference. Next, an outer bead core is disposed outside the ply cord 3 in the tire radial direction. At this time, the end portion 4 of the ply cord protrudes inward in the tire radial direction from the innermost end in the tire radial direction of the outer bead core 6, and the ply cord 3 is sandwiched between the inner bead core 5 and the inner bead core 6. Thus, a sandwiched bead structure as shown in FIG. 8 is obtained. An unvulcanized rubber strip is wound and laminated thereon, and other tire components such as a reinforcing belt layer and a tread portion are attached to form a green tire. Although not shown, when this green tire is vulcanized in a molding die, a tire according to the present invention is obtained. In this manufacturing method, since the carcass cord processed in advance by the processing method according to the present invention is used, an operation using a bladder or the like for bending the end portion of the carcass ply can be omitted. It can be further simplified, and labor saving and labor saving are sufficiently achieved.

  A tire manufactured by such a manufacturing method has a bead portion structure as shown in FIGS. According to this, the end portion 4 of the ply cord is disposed so as to be on the inner side in the tire radial direction than the innermost end 7 in the tire radial direction of the inner bead core 5 and the outer bead core 6, and the inner bead core 5 and the outer bead core 6. Since the distance in the tire width direction of the end portion 4 of the ply cord that is plastically deformed is longer than the distance in the tire width direction between the tire and the carcass ply, even when the carcass ply is pulled outward in the tire radial direction during tire load rolling Since the carcass ply is sufficiently held between the inner bead core 5 and the outer bead core 6 and the end portion 4 of the plastically deformed ply cord is locked to the bead cores 5 and 6, the carcass ply is connected to the bead portion of the carcass ply. The locking force is remarkably improved, and it is possible to effectively prevent the carcass ply from being pulled out even when traveling under heavy load conditions, and to improve the durability of the bead part. It can be.

The above description shows only a part of the embodiment of the present invention, and various modifications can be made without departing from the gist of the present invention. For example, the carcass ply is configured so that the end portions 4 of the ply cords are plastically deformed every other one or two when viewed in the tire circumferential direction without plastically deforming the end portions 4 of all the ply cords. It is good as a tire.

  As is apparent from the above description, according to the present invention, a ply cord processing method capable of improving the locking force with the bead core, and manufacturing a pneumatic tire using the ply cord processed by the processing method It has become possible to provide a pneumatic tire excellent in durability of the bead portion manufactured by the method and the manufacturing method thereof.

1 is a perspective view of a forming die according to the present invention. It is sectional drawing of the shaping | molding die according to this invention. It is the end part of the spiral ply cord processed with the processing method according to this invention, and the ply cord part of the vicinity. It is a fracture perspective view of the bead part of the typical pneumatic tire according to this invention. FIG. 5 is a left half sectional view of the tire shown in FIG. 4 in the tire width direction. It is a figure for demonstrating the manufacturing process of this invention. It is a figure for demonstrating the manufacturing process of this invention. It is a figure for demonstrating the manufacturing process of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Forming die 2 Pressing member 3 Ply cord 4 Ply cord end 5 Inner bead core 6 Outer bead core 7 Innermost end 8 in the tire radial direction of the bead core Rigid core

Claims (5)

  A method for processing a ply cord constituting a carcass ply of a pneumatic tire, the step of coating a metal cord with rubber, the step of cutting the rubber-coated cord into a predetermined length, and both ends of the cut cord A portion of the cord is pulled out from the molding die while pressing a part of the outer peripheral surface of the cord with a pressing member disposed in the molding die. A method for processing a ply cord, comprising the step of plastically deforming the portion into a predetermined shape.   The ply cord processing method according to claim 1, wherein the cord is pulled out from the forming die while pressing about a half circumference of the outer circumference of the cord.   The ply cord processing method according to claim 1 or 2, wherein both ends of the cord are plastically deformed in a spiral shape.   An inner bead core is disposed on the bead portion of the rigid core, and a ply cord is extended and adhered to the outer peripheral surface of the rigid core along the axial direction on the outer side in the tire width direction of the inner bead core. An outer bead core is disposed on the outer side of the cord in the tire width direction so as to sandwich the ply cord together with the inner bead core, and a tire is formed by attaching tread rubber, other reinforcing members and rubber members on the outer peripheral surface thereof. In doing so, in each of the bead portions, the ply cord processed by using the processing method according to any one of claims 1 to 3, wherein an end portion in which the plastic deformation is performed is an innermost portion in the tire radial direction of the bead core. A method for producing a pneumatic tire, wherein the pneumatic tire is disposed so as to be inside in a tire radial direction from an end.   The pneumatic tire manufactured using the manufacturing method of the pneumatic tire of Claim 4.

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