JP2005289301A - Pneumatic tire and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire which achieves an improvement in durability by effectively preventing separation in a folded-back end of a carcass ply while being a relatively simple structure, and its manufacturing method. <P>SOLUTION: A tire 1 is formed by folding both ends 4 of a carcass ply 2 back around a bear core 3 while toroidally extending across the pair of bead cores 3 at least one carcass ply 2 in which a plurality of ply cords are coated with rubber so as to be arranged in parallel. The end positions 6a, 6b of a ply cord 5 forming the carcass ply 2 are separately arranged on at least two virtual circumferences C<SB>1</SB>and C<SB>2</SB>which are coaxial with the outer periphery C<SB>0</SB>of the tire 1 and have different diameters. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, at least one carcass ply formed by rubber-covering a plurality of ply cords in a parallel arrangement is extended in a toroid shape between a pair of bead cores, and both ends thereof are folded around the bead cores. The present invention relates to a pneumatic tire and a method for manufacturing the same, and particularly to prevent separation at the end portion of the carcass ply of such a tire.

  Usually, a pneumatic tire has at least one carcass ply formed by rubber-coating a plurality of ply cords in a parallel arrangement, and extends in a toroid shape between a pair of bead cores. Truck and bus tires generally employ a structure in which both ends of the carcass ply are folded around the bead core and locked by the bead core in order to prevent a failure due to the carcass ply being pulled out. However, in a tire having such a structure, if the bead portion deforms during traveling, stress tends to concentrate on the folded end portion of the carcass, and separation between the ply cord and the covering rubber occurs at the end portion. There was a problem that this easily reduced the durability of the tire.

  In order to avoid the concentration of stress on the folded end portion of the carcass, for example, in Patent Document 1, the folded carcass is wrapped with two layers of steel chafers around the bead core, and the meridian direction of both steel chafers is determined. Each of the cord angles is in the range of 15 ° to 35 °, crosses in opposite directions to each other, the distance from the center of the bead core to the folded end of the carcass is H, and the outer and inner steel chafers located on the outer side in the tire width direction When the distances to the ends are h1 and h2, respectively, and the distances to the ends of the outer and inner steel chafers located on the inner side in the tire width direction are h3 and h4, respectively, the relationship of h1 <h2 <H <h3 <h4 Pneumatic tire with both steel chafers covered with harder rubber than the surrounding rubber Is described.

  Patent Document 2 describes a pneumatic tire in which a folded end portion of a carcass is further folded toward the bead core, and the folded terminal is disposed at a position corresponding to the bead core.

  In Patent Document 3, an auxiliary bead wire is disposed in a bead portion located on the outer side in the tire width direction of the folded end portion of the carcass and above the rim flange, and a reinforcing ply is wound around the auxiliary bead wire. A pneumatic tire is described in which the tip of the tire is extended to the tip of the bead.

  Patent Document 4 describes a pneumatic tire in which a carcass ply is fixed between an outer portion of a bead core in a tire radial direction and a fixing ring-shaped body that engages with the outer portion.

  In Patent Document 5, the end portion of the folded carcass ply is arranged on the outer side in the tire radial direction from the straight line passing through the outer end in the tire radial direction of the rim flange in the cross section in the tire width direction, and at least one bend is formed in the folded portion. The actual length of the carcass ply between the intersection and the end of the carcass ply is 1.3 times the length of the straight line connecting the intersection of the carcass ply and the straight line and the end of the carcass ply. The pneumatic tire described above is described.

  Each of the pneumatic tires described in Patent Documents 1 to 5 has a certain effect in terms of preventing separation from the folded end portion of the carcass and improving durability, but the manufacturing process becomes complicated. In addition, it is necessary to add a member that is not included in the conventional tire, which is disadvantageous in terms of manufacturing efficiency, manufacturing cost, and weight. In particular, in recent years, there is an increasing demand for weight reduction of tires for the purpose of reducing fuel consumption, and therefore, separation from the carcass folded end portion is prevented by means different from the means described in these patent documents. It is hoped that.

JP-A-5-155208 Japanese Patent Laid-Open No. 5-178034 Japanese National Patent Publication No. 5-508366 JP-A-8-40026 JP 2000-225816 A

  Accordingly, an object of the present invention is to provide a pneumatic tire and a method of manufacturing the same that have a relatively simple structure but effectively prevent separation at the folded end of the carcass ply to improve durability.

  In order to achieve the above object, the first invention extends at least one carcass ply formed by rubber coating a plurality of ply cords in a parallel arrangement state in a toroidal shape between a pair of bead cores, In a pneumatic tire in which both end portions are folded around a bead core, at least one carcass ply has an end position of a ply cord constituting the concentric outer periphery of the tire as seen from the side of the tire. A pneumatic tire characterized in that the pneumatic tire is spaced apart on at least two virtual circumferences having different diameters.

  Further, the same carcass ply is composed of a ply cord having a constant length, and at least a part of the ply cords is arranged such that the center position in the length direction is shifted from the position of the tire equatorial plane. It is preferable that

  Alternatively, the same carcass ply may be composed of at least two types of ply cords having different lengths, and all of the ply cords may be arranged such that the center position in the length direction coincides with the tire equatorial plane position. preferable.

  Furthermore, it is preferable that the contour shape formed when one end position of the ply cord is connected by a virtual line segment is a triangular wave shape, a sine wave shape or a trapezoidal wave shape.

  Further, the second aspect of the present invention is to apply an annular non-added shape by sequentially attaching a plurality of narrow strips formed by coating at least one ply cord with unvulcanized rubber on a cylindrical or toroid-shaped rigid body. In a method for producing a pneumatic tire, comprising: a step of forming a sulfur ply; a step of attaching a bead ring on the unvulcanized ply; and a step of folding both ends of the unvulcanized ply around the bead ring. A plurality of narrow strips with a single length are pasted on the rigid body, alternately shifting in the direction of the axis of rotation of the rigid body, and the unvulcanized ply is placed so that the end position of the ply cord is staggered. It is a manufacturing method of a pneumatic tire characterized by forming.

  Further, according to the third aspect of the present invention, a plurality of narrow strips formed by coating at least one ply cord with unvulcanized rubber are sequentially pasted on a rigid body having a cylindrical shape or a toroid shape, and an annular non-added portion is added. In a method for producing a pneumatic tire, comprising: a step of forming a sulfur ply; a step of attaching a bead ring on the unvulcanized ply; and a step of folding both ends of the unvulcanized ply around the bead ring. A plurality of two kinds of narrow strips having different lengths are stuck on the rigid body alternately so that the longitudinal center position thereof coincides with the planar position including the central circumferential line of the rigid body, and the ply cord In this method, the unvulcanized ply is formed so that the end positions of the tires are staggered.

  According to the first invention, it is possible to provide a pneumatic tire that has a relatively simple structure but effectively prevents separation at the folded end of the carcass ply and has improved durability. According to the third aspect, the tire according to the first aspect can be produced efficiently.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a left half section of a typical pneumatic tire (hereinafter referred to as “tire”) according to the present invention in the tire width direction, and FIG. 2 shows one end of a carcass ply from the side of the tire in FIG. FIG. 3 is a partially expanded view of the carcass ply of the tire of FIG.

  As shown in FIG. 1, a tire 1 includes at least one carcass ply formed by covering a plurality of ply cords with rubber in a parallel arrangement state, and in FIG. 1, a carcass ply 2 includes a pair of bead cores 3 ( While extending in a toroid shape between only one side (shown only on one side), both end portions 4 (only one side shown) are folded around the bead core 3. In addition, although illustration was abbreviate | omitted, you may provide suitably the members which comprise conventional tires, such as a belt layer, a bead filler, and a chafer. In the illustrated example, the carcass ply 2 is folded back from the inside of the bead core 3 to the outside, but it may be folded back from the outside of the bead core 3 to the inside.

The main features of the structure of this invention, as shown in FIG. 2, the end position 6a of the ply cords 5 constituting the carcass ply 2, 6b is a and different diameter outer peripheral C ₀ concentric tire 1 At least two of the virtual circle having, in placing by separation on Figure 2, two virtual circle C ₁ and C _2.

Hereinafter, the background to the completion of the present invention will be described together with the operation.
It is known that separation from the turn-up end portion of the carcass ply is known as one of the causes of shortening the life of the tire that turns the carcass ply around the bead core or inducing trouble. The main cause of the occurrence of such separation is considered to be that cracks grow between the ply cord having different rigidity and the covering rubber as a result of repeated stress concentration on the folded end portion of the carcass ply during traveling. As described above, conventionally, an additional member is provided around the folded end portion of the carcass ply, or the folded end portion is reinforced with a special shape to thereby stress the folded end portion of the carcass ply. Was avoiding concentration. However, since such a conventional technique has a complicated structure, there is a problem that manufacturing efficiency is lowered, manufacturing cost is increased, and weight is further increased.

  The inventor found that the stress concentration on the folded end portion of the carcass ply is caused by the fact that all the end positions of the ply cords constituting the carcass ply are arranged on the same virtual circumference concentric with the outer circumference of the tire. I got the idea. Therefore, the inventor can disperse and arrange the end positions of the ply cords on at least two different virtual circumferences, and as a result, the stress is also distributed. As a result, the structure is relatively simple. The inventors have found that it is possible to effectively prevent the separation at the folded end of the carcass ply and improve the durability, and have completed the first invention.

  As a means for dispersively arranging the end positions 6 of the ply cords 5 on different virtual circumferences, for example, as shown in FIG. 3, the same carcass ply 2 is composed of ply cords 5 having a constant length. Preferably, at least a part of the ply cords 5 of the ply cords 5, each ply cord in FIG. 3, are arranged such that the center position M in the longitudinal direction is deviated from the tire equatorial plane position E. More preferably, the tires are arranged so as to be staggered at equal distances from the tire equatorial plane position E. Since such a carcass ply is composed of only a single length of ply cord, it is advantageous in that the manufacture, management and storage of the ply cord is simplified. In this case, from the viewpoint of ensuring tire uniformity, the number of ply cords in which the longitudinal center position M of the ply cord 5 is located on the right side of the tire equatorial plane position E and the longitudinal center position M Is preferably the same as the number of ply cords located on the left side of the tire equatorial plane position E.

  As shown in FIG. 4, the same carcass ply 2 may be composed of at least two types of ply cords having different lengths, in FIG. 4, two types of ply cords 5a and 5b. In this case, the ply cord 5a 5b is preferably arranged so that its longitudinal center position M coincides with the tire equatorial plane position E. In such a carcass ply, the center of gravity of all ply cords coincides with the position of the tire equatorial plane, so that the carcass ply has a symmetrical structure with respect to the tire equatorial plane, which is further advantageous in terms of improving uniformity.

  Further, the contour formed when the one end position 6 of the ply cord 5 is connected by the imaginary line L can have various shapes. For example, as shown in FIGS. 3 and 4, by alternately shifting the end positions 6 of the ply cord 5, the contour shape can be a triangular wave. Further, when it is necessary to further enhance the stress dispersion effect at the cord end position, as shown in FIG. 5, the ply cord 5 is placed on three or more virtual circumferences (indicated by a one-dot chain line in FIG. 5). The end shape 6 may be arranged to make the contour shape sinusoidal. Further, when it is particularly necessary to simplify the manufacturing process, a plurality of ply cords are set as one unit, and the end positions 6 of the ply cords 5 are arranged so as to be shifted for each unit. As shown in FIG. 3, the contour shape may be a trapezoidal wave. The number of ply cords constituting one unit is not particularly limited, but the number of ply cords constituting one unit is reduced from the viewpoint of reducing the balance difference on the circumference and suppressing the occurrence of vibration during traveling. Is preferably 3 or less.

  In addition, as shown in FIG. 7, the ply cords 5 c and 5 d arranged by shifting the longitudinal center position M from the tire equatorial plane position E and the longitudinal center position M coincide with the tire equatorial plane position E. The arranged ply cords 5e and 5f can also be used in combination.

Next, a method for manufacturing the tire according to the first invention will be described.
First, at least one ply cord is covered with unvulcanized rubber, and a large number of narrow strips having a single length are prepared. Next, a gas-impermeable inner liner is affixed on a rigid body having a cylindrical or toroidal shape that can be reduced or divided. On this, the said narrow strip is affixed by shifting alternately in the rotation-axis direction of a rigid body. Then, when this operation is repeated until the entire outer peripheral surface of the rigid body is covered with the narrow strip, as shown in a partial development view in FIG. 8, the end position 6 of the ply cord 5 is a staggered annular shape. An unvulcanized ply 2 is formed. Next, a bead ring is attached on the unvulcanized ply, and both ends of the unvulcanized ply are folded around the bead ring using a known means such as a bladder. Then, according to a conventional tire manufacturing method, necessary members such as a belt and a tread are further attached to form a green tire, and when this is vulcanized and molded in a mold, a pneumatic tire according to the first invention is obtained. It is done.

  Also, instead of the narrow strip having a single length, two kinds of narrow strips having different lengths are used so that the longitudinal center positions thereof coincide with the plane positions including the central circumference of the rigid body. It may be pasted alternately. In this case, a development view of a part of the unvulcanized ply formed is as shown in FIG.

  As described above, the method of manufacturing the carcass ply by attaching the narrow strip on the rigid body is less advantageous in manufacturing the carcass ply, and is more advantageous in terms of improving tire quality, particularly uniformity.

  Alternatively, a plurality of ply cords having a constant length are used, and at least some of the ply cords are arranged in parallel so that the center position in the length direction is shifted from the center position in the width direction of the carcass ply. Or at least two types of ply cords having different lengths, and all these ply cords are arranged in parallel so that the center position in the length direction coincides with the center position in the width direction of the carcass ply, By winding a wide ply formed by covering this with a rubber according to a conventional manufacturing method in the circumferential direction of the rigid body, the same carcass ply having a developed shape as shown in FIGS. 3 to 6 can be obtained. These methods are particularly advantageous in that the processes after the rubber coating of the cord can be shared with the conventional tire manufacturing process.

  Furthermore, after forming a cord-filled rubber sheet with a constant width in which both end portions of the cord are used, which is used in the conventional manufacturing method, a carcass ply having a desired contour shape is formed by cutting the both ends into a predetermined shape. You can also

  In addition, the place mentioned above only showed a part of embodiment of this invention, and can change a various change in a claim. For example, in FIGS. 2 to 9, the ply cord has been described taking as an example a so-called radial ply in which the ply cord extends substantially at right angles to the tire equatorial plane. The present invention can also be applied to a so-called bias ply that extends at an angle.

  According to the present invention, there are provided a pneumatic tire having a relatively simple structure and effectively preventing separation at the folded end of the carcass ply to improve durability, and a method for efficiently manufacturing such a tire. It became possible to do.

1 is a left half sectional view in a width direction of a typical pneumatic tire according to the present invention. FIG. 2 is a perspective view of a part of the end portion of the carcass ply as viewed from the side of the tire shown in FIG. 1. FIG. 2 is a development view of a part of the carcass ply of the tire shown in FIG. 1. FIG. 5 is a development view of a part of a carcass ply of another tire according to the present invention. FIG. 5 is a development view of a part of a carcass ply of another tire according to the present invention. FIG. 5 is a development view of a part of a carcass ply of another tire according to the present invention. FIG. 5 is a development view of a part of a carcass ply of another tire according to the present invention. FIG. 5 is a development view of a part of a carcass ply of another tire according to the present invention. FIG. 5 is a development view of a part of a carcass ply of another tire according to the present invention.

Explanation of symbols

1 tire 2 carcass ply 3 bead core 4 ply end 5, 5a, 5b, 5c, 5d, 5e, 5f ply cord 6, 6a, 6b ply cord end position 7 narrow strip

Claims (8)

At least one carcass ply formed by covering a plurality of ply cords with rubber in a parallel arrangement is extended in a toroid shape between a pair of bead cores, and both ends thereof are folded back around the bead cores. In the tire,
At least one carcass ply is separated from the end position of the ply cords constituting the carcass ply on at least two virtual circumferences that are concentric with the tire outer circumference and have different diameters as seen from the side of the tire. A pneumatic tire characterized by being arranged.   The same carcass ply is composed of ply cords having a constant length, and at least some of the ply cords are arranged such that the center position in the length direction is deviated from the tire equatorial plane position. The pneumatic tire according to claim 1.   The same carcass ply is composed of at least two types of ply cords having different lengths, and all of the ply cords are arranged such that the center position in the length direction coincides with the tire equatorial plane position. Pneumatic tire described in 2.   The pneumatic tire according to any one of claims 1 to 3, wherein a contour shape formed when the one end position of the ply cord is connected by a virtual line segment is a triangular wave shape.   The pneumatic tire according to any one of claims 1 to 3, wherein a contour shape formed when one end position of the ply cord is connected by a virtual line segment is a sine wave shape.   The pneumatic tire according to any one of claims 1 to 3, wherein a contour shape formed when one end position of the ply cord is connected by a virtual line segment is a trapezoidal wave shape. Forming an annular unvulcanized ply by sequentially affixing a plurality of narrow strips formed by coating at least one ply cord with unvulcanized rubber on a cylindrical or toroid-shaped rigid body; In the method for producing a pneumatic tire, comprising a step of attaching a bead ring on the unvulcanized ply and a step of folding back both ends of the unvulcanized ply around the bead ring.
On the rigid body, a plurality of narrow strips having a single length are affixed alternately in the rotational axis direction of the rigid body, and the unvulcanized ply is formed so that the end positions of the ply cords are staggered. Forming a pneumatic tire. Forming an annular unvulcanized ply by sequentially affixing a plurality of narrow strips formed by coating at least one ply cord with unvulcanized rubber on a cylindrical or toroid-shaped rigid body; In the method for producing a pneumatic tire, comprising a step of attaching a bead ring on the unvulcanized ply and a step of folding back both ends of the unvulcanized ply around the bead ring.
A plurality of two types of narrow strips having different lengths are affixed on the rigid body alternately so that the longitudinal center position thereof coincides with the planar position including the central circumference of the rigid body. A method for producing a pneumatic tire, characterized in that the unvulcanized ply is formed so that the end positions of the cords are staggered.

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