JP2012240373A - Method of manufacturing pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a pneumatic radial tire, reducing rolling resistance while securing steering stability and durability.SOLUTION: Inside belt ply 5 including an organic fiber cord arranged so as to be inclined to a tire circumferential direction is molded into a cylindrical shape, and a diameter of the inside belt ply 5 molded into the cylindrical shape is expanded. A pair of split ply pieces 4a and 4b constituting a carcass ply 4 is disposed. The center area of the inside belt ply 5 is opened, while covering both end areas of the inside belt ply 5 with the ends of the pair of split ply pieces 4a and 4b. An outside belt ply 6 including a steel cord arranged so as to be inclined to the tire circumferential direction and opposite to the organic fiber cord is molded into the cylindrical shape. The ends of the split ply pieces 4a and 4b are held by the inside belt ply 5 and the outside belt ply 6.

Description

  The present invention relates to a method for manufacturing a pneumatic radial tire in which a carcass ply is divided in a tire width direction in a central region of a tread portion.

  As disclosed in Patent Documents 1 and 2 below, a pneumatic radial tire having a so-called hollow structure in which a carcass ply is divided in a tire width direction in a central region of a tread portion is known. In such a hollow structure, the carcass ply is constituted by a pair of left and right divided ply pieces, and a hollow portion lacking the carcass ply is formed in the central region of the tread portion, so that the riding performance is improved and contradicted. There is an advantage that compatibility with steering stability performance can be achieved.

  However, in a tire having a hollow structure, separation tends to occur starting from the end of the split ply piece arranged in the tread portion, which may damage the inner liner rubber. This is due to the fact that the end of the split ply piece is easily displaced by the load repeatedly input as the tire rolls during traveling, in order to suppress the displacement of this end and ensure durability. Measures were needed.

  On the other hand, in Patent Document 1, among the two carcass plies, at least the carcass ply on the outer side in the tire radial direction has a hollow structure, and the ends of the pair of split ply pieces arranged in the tread portion are a plurality of pieces. A structure that is sandwiched between belt plies has been proposed.

  Moreover, in patent document 2, the structure which arrange | positions a reinforcement layer inside a tire radial direction separately from the two belt plies which comprise a belt layer, and clamps the edge part of a division | segmentation ply piece with a belt ply and a reinforcement layer Has been proposed. The reinforcing layer is composed of a fiber material (cord material) arranged in a calendar shape, and in this document, the durability of the tire can be improved satisfactorily by extending the fiber material substantially in the tire circumferential direction. Is positioned.

  In Patent Documents 1 and 2, steel cords and organic fiber cords are cited as the cord material constituting the belt ply. However, a belt ply made of a steel cord tends to increase the tire weight and increase rolling resistance. On the other hand, a belt ply made of an organic fiber cord can reduce the rolling resistance as compared with the case where a steel cord is used, but on the other hand, the belt rigidity is lowered and the steering stability performance tends to deteriorate.

JP-A-2005-081873 JP 2007-283962 A

  This invention is made | formed in view of the said situation, The objective is to provide the manufacturing method of a pneumatic radial tire which can reduce rolling resistance, ensuring steering stability performance and durability performance.

  The above object can be achieved by the present invention as described below. That is, the method for manufacturing a pneumatic radial tire according to the present invention is the method for manufacturing a pneumatic radial tire in which the carcass ply is divided in the tire width direction in the center region of the tread portion. The inner belt ply arranged so as to be inclined is formed into a cylindrical shape, the diameter of the inner belt ply formed into the cylindrical shape is expanded, and a pair of split ply pieces constituting the carcass ply are arranged. A step of opening a central region of the inner belt ply while covering both end regions of the inner belt ply with ends of the pair of split ply pieces, and a steel cord inclined with respect to the tire circumferential direction. And forming the outer belt ply disposed in the opposite direction to the organic fiber cord into a cylindrical shape and covering both end regions of the inner belt ply. A step of sandwiching an end portion of the ply pieces and the outer belt ply and the inner belt ply, in which comprises a.

  In the present invention, since the inner belt ply is made of an organic fiber cord, the inner belt ply is lighter than when a steel cord is used, and an effect of reducing rolling resistance can be obtained. In addition, the diameter of the inner belt ply formed into a cylindrical shape is expanded, and then an outer belt ply made of steel cord is provided. Therefore, tension is applied to the organic fiber cord of the inner belt ply, and the belt rigidity is increased to improve the steering stability. Can be secured. Nevertheless, by sandwiching the end portions of the pair of split ply pieces between the inner belt ply and the outer belt ply, it is possible to suppress the displacement of the end portions of the split ply pieces and ensure durability.

  As described above, the present invention aims to improve belt rigidity by expanding the diameter of the inner belt ply formed into a cylindrical shape and applying tension to the organic fiber cord. Therefore, an organic fiber cord having a lower tensile modulus than the steel cord is used for the inner belt ply, and the organic fiber cord is inclined with respect to the tire circumferential direction, and the outer belt ply is disposed after the inner belt ply is expanded. Thus, the inner belt ply can cope with the diameter change.

  On the other hand, when the inner belt ply is made of a steel cord, the tensile modulus becomes too high, and when the inner belt ply cord is arranged in the tire circumferential direction, the circumferential length thereof is reduced. In addition, if the outer belt ply is disposed before the inner belt ply is expanded, the inner belt ply cannot respond to the change in diameter because the restraining force of the outer belt ply acts. It becomes difficult to apply tension to the cord.

  In the present invention, it is preferable that the inclination angle of the organic fiber cord with respect to the tire circumferential direction is within a range of 20 to 45 ° before the diameter of the inner belt ply formed into a cylindrical shape is expanded. As a result, when the diameter of the inner belt ply formed into a cylindrical shape is expanded, the inner belt ply can easily cope with a change in diameter, and tension is appropriately applied to the organic fiber cord to effectively improve the belt rigidity. Can be increased.

  In the present invention, when the diameter of the inner belt ply formed into a cylindrical shape is expanded, the expansion rate of the inner belt ply is preferably 3 to 15%. By setting the expansion rate of the inner belt ply within the above range, it is possible to appropriately apply tension to the organic fiber cord without deteriorating workability, and to improve the belt rigidity and ensure the steering stability performance. .

In the present invention, the inner belt ply cord preferably has a tensile modulus of 25000 N / mm ² or more. In this case, the belt modulus can be effectively increased by securing a certain tensile modulus in the inner belt ply. The “tensile modulus” refers to a value obtained by obtaining the initial tensile resistance from the maximum point of load change with respect to the extension change of the cord in accordance with JISL1017 and obtaining the apparent Young's modulus by the following equation.
E ′ = 100 × ρ × Rd
E ′: Apparent Young's modulus (N / mm ² )
ρ: Fiber density (g / cm ³ )
Rd: Initial tensile resistance (cN / dtex)

  In the present invention, it is preferable that the pair of split ply pieces are respectively wound around the bead core from the outside to the inside. As a result, the change in curvature of the inner surface of the carcass ply from the belt end to the bead portion can be suppressed, the tension due to the internal pressure can be made uniform, and the cornering characteristics can be made linear, thereby improving the steering stability performance. In addition, since the rubber flow failure on the outside of the carcass ply is suppressed during vulcanization molding, it is possible to reduce the weight by reducing the thickness of the rubber at that portion, and to further reduce the rolling resistance.

A tire meridian half sectional view showing an example of a pneumatic radial tire manufactured by the present invention Sectional drawing which shows the ply in a tread part typically Top view showing ply in tread Schematic sectional view for explaining a method for producing a pneumatic radial tire according to the present invention Schematic sectional drawing explaining the manufacturing method of the pneumatic radial tire which concerns on another embodiment of this invention Schematic sectional drawing explaining the manufacturing method of the pneumatic radial tire which concerns on another embodiment of this invention

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a half sectional view of a tire meridian schematically showing a pneumatic radial tire manufactured according to the present invention. FIG. 2 is a cross-sectional view schematically showing a ply in the tread portion 3 of the tire. FIG. 3 is a plan view showing these plies, but the cords in the drawing are conceptually drawn, and the actual arrangement pitch becomes denser.

  The pneumatic radial tire T has a symmetrical structure with respect to the tire equator CL, and includes a pair of bead portions 1, a sidewall portion 2 extending outward from the bead portion 1 in the tire radial direction, and a sidewall portion thereof. And a tread portion 3 connected to each outer end in the tire radial direction. Each of the pair of bead portions 1 is provided with an annular bead core 1a and a bead filler 1b made of hard rubber disposed on the outer side in the tire radial direction of the bead core 1a.

  The tread portion 3 includes an inner belt ply 5 in which the organic fiber cord 5C is inclined with respect to the tire circumferential direction CD, and an organic fiber cord so that the steel cord 6C is inclined with respect to the tire circumferential direction CD. An outer belt ply 6 disposed in the direction opposite to 5C is embedded. Examples of the inclination angles θ5 and θ6 of the cords 5 and 6 with respect to the tire circumferential direction CD are 18 to 42 °, respectively. As the material for the organic fiber cord 5C, aramid is preferably used, but polyester, rayon, nylon or the like may be used.

  The carcass ply 4 is provided in a toroid shape as a whole, but is divided in the tire width direction in the central region of the tread portion 3 and has a so-called hollow structure. The carcass ply 4 is composed of a pair of split ply pieces 4 a and 4 b, each of which reaches the end of the belt plies 5 and 6 via the bead part 1 and the sidewall part 2. The ends of the divided ply pieces 4a and 4b arranged in the tread portion 3 are separated from each other in the tire width direction, and a hollow portion where the carcass ply 4 is missing is formed between them.

  The carcass ply 4 includes a carcass cord 4C disposed so as to be substantially orthogonal to the tire circumferential direction CD. As the carcass cord 4C, an organic fiber cord is preferably used. The pair of split ply pieces 4a and 4b constituting the carcass ply 4 has a so-called down structure in which the periphery of the bead core 1a is wound back from the outside to the inside, and the ends thereof are locked by the bead portion 1. .

  An inner liner rubber 7 constituting the inner surface of the tire T is provided inside the carcass ply 4. The inner liner rubber 7 has a function of blocking the permeation of the gas filled in the tire. In the sidewall portion 2, a sidewall rubber 8 constituting the outer wall surface of the tire T is provided outside the carcass ply 4, and in the tread portion 3, a tread rubber 9 constituting the tread surface of the tire T is provided. It has been. A tread pattern is formed on the surface of the tread rubber 9 when vulcanization molding is performed.

  A method for manufacturing the pneumatic radial tire T will be described with reference to FIG. Since the manufacturing method of the pneumatic radial tire according to the present invention can be performed in the same manner as the conventional tire manufacturing process except for the processes related to the belt ply and the carcass ply, the belt ply 5 and 6 and the carcass ply 4 will be described below. The arrangement process will be mainly described.

  First, a belt-like ply formed by coating an array of organic fiber cords 5C with rubber is prepared, and the ply is attached to the outer periphery of the rigid core 11 as shown in FIG. The inner belt ply 5 disposed so as to be inclined with respect to the direction is formed into a cylindrical shape. The rigid core 11 is a drum-like member configured to be able to expand the diameter, and the surface to which the inner belt ply 5 is attached is gently curved along the tire width direction. Subsequently, as shown in FIG. 4B, the diameter of the inner belt ply 5 formed into a cylindrical shape is expanded by expanding the diameter of the rigid core 11. Thereby, tension is applied to the organic fiber cord 5 </ b> C of the inner belt ply 5.

  Next, as shown in FIG. 4 (c), a pair of split ply pieces 4a and 4b constituting the carcass ply 4 are disposed, and both end regions of the inner belt ply 5 are located at the ends of the split ply pieces 4a and 4b. The central region of the inner belt ply 5 is opened while covering. At this stage, tire constituent members such as the inner liner rubber 7, the side wall rubber 8, the bead core 1a, and the bead filler 1b are also disposed, and the end portions of the divided ply pieces 4a and 4b are wound around the bead core 1a. Although not shown in the drawing.

  After that, a belt-like ply formed by coating the steel cord 6C array with rubber is prepared, and is attached to the outer periphery of the inner belt ply 5 in an annular shape as shown in FIG. 4 (d). The outer belt ply 6 disposed so as to be inclined with respect to the organic fiber cord 5C is formed into a cylindrical shape. At this time, the end portions of the divided ply pieces 4 a and 4 b covering both end regions of the inner belt ply 5 are sandwiched between the inner belt ply 5 and the outer belt ply 6.

  And although illustration is abbreviate | omitted, the tread rubber 9 is provided in the outer periphery of the outer side belt ply 6, and a green tire like FIG. 1 is shape | molded. A cylindrical member combining the outer belt ply 6 and the tread rubber 9 may be formed in advance, and the cylindrical member may be pressure-bonded to the outer periphery of the inner belt ply 5. The molded green tire is removed from the rigid core 11 and then vulcanized.

  In the manufactured tire T, the inner belt ply 5 is made of an organic fiber cord, so that an effect of reducing rolling resistance associated with a reduction in tire weight can be obtained, and an effect of improving riding comfort performance by reducing out-of-plane bending rigidity. Can also be obtained. In addition, since tension is applied to the organic fiber cord 5C of the inner belt ply 5, it is possible to increase the belt rigidity and ensure the steering stability performance (particularly cornering characteristics). Nevertheless, by sandwiching the end portions of the split ply pieces 4a and 4b between the inner belt ply 5 and the outer belt ply 6, it is possible to suppress the displacement of the end portions of the split ply pieces 4a and 4b and to ensure durability. .

  From the viewpoint of firmly suppressing the displacement of the end portions of the split ply pieces 4a and 4b and ensuring the durability, the overlap margin L (see FIG. 2) between the end portions of the split ply pieces 4a and 4b and the narrow belt ply is: 10 mm or more is preferable. The narrow belt ply indicates the narrower one of the inner belt ply 5 and the outer belt ply 6, and the inner belt ply 5 corresponds to the present embodiment. In the present invention, since the cord material is different between the inner belt ply 5 and the outer belt ply 6, either of them may be narrow. The step S (interval in the tire width direction) between the end of the inner belt ply 5 and the end of the outer belt ply 6 is preferably 4 to 12 mm.

  The width EW of the hollow portion (the interval between the ends of the divided ply pieces 4a and 4b) is preferably 70 to 90% of the width BW of the narrow belt ply (inner belt ply 5 in this embodiment). In the hollow section, the organic fiber cord 5C and the steel cord 6C are laminated so as to cross each other in the opposite directions between the plies. By making this ratio 70% or more, the function as a belt can be sufficiently exerted. At least, the steering stability performance (especially cornering characteristics) can be secured satisfactorily. On the other hand, by setting the ratio to 90% or less, a sufficient overlap margin L can be easily secured.

  In the state shown in FIG. 4A, that is, before the diameter of the inner belt ply 5 formed into a cylindrical shape is expanded, the inclination angle of the organic fiber cord 5C with respect to the tire circumferential direction is in the range of 20 to 45 °. It is preferable to be inside. As a result, when the diameter of the cylindrical inner belt ply 5 is expanded, the inner belt ply 5 can easily cope with a change in diameter, and tension is appropriately applied to the organic fiber cord 5C to effectively improve the belt rigidity. Can be increased.

  When the diameter of the cylindrical inner belt ply 5 is expanded as shown in FIG. 4B, the expansion rate of the inner belt ply 5 is preferably 3 to 15%. Thereby, without accompanying workability deterioration, it is possible to appropriately apply tension to the organic fiber cord 5C, increase belt rigidity, and ensure steering stability performance. This expansion rate is expressed by the formula of (diameter after expansion−diameter before expansion) / diameter before expansion based on the inner diameter of the inner belt ply 5 (or the outer diameter of the rigid core 11) at the tire equator. Is calculated by

The inner belt ply 5 preferably has a cord tensile modulus of 25000 N / mm ² or more. Thereby, the tensile modulus in the inner belt ply 5 can be secured to some extent, and the belt rigidity can be effectively increased. The tensile modulus of the cord of the outer belt ply 6 made of the steel cord 6C is approximately 160000 to 170000 N / mm ² , while the tensile modulus of the cord of the inner belt ply 5 is lower, at most 40000 N / mm ² . is there.

  In the tire T of the present embodiment, the tread rubber 9 is directly placed on the outer periphery of the outer belt ply 6 without any other belt ply so that the effect of reducing the rolling resistance can be enhanced. We are trying to make it. However, in order to enhance the high-speed durability performance, it is possible to provide a belt reinforcing layer in which the cord is arranged substantially parallel to the tire circumferential direction as necessary. In addition, the carcass ply 4 may be a plurality of stacked ones, but it is desirable that the carcass ply 4 is configured as a single layer as in this embodiment in order to reduce the tire weight and the rolling resistance.

  A method for manufacturing a pneumatic radial tire T according to another embodiment of the present invention will be described with reference to FIGS. In addition, since it is the same as that of embodiment of FIG. 4 except the matter demonstrated below, a common point is abbreviate | omitted and it mainly demonstrates a difference.

  The example of FIG. 5 is the same as the method of FIG. 4 except that a bladder 12 is used instead of the rigid core 11. The bladder 12 is a rubber bag that can be expanded and contracted, and corresponds to a drum-shaped member configured to be able to expand its diameter. First, as shown in FIG. 5A, on the outer periphery of the bladder 12, the inner belt ply 5 disposed so that the organic fiber cord 5C is inclined with respect to the tire circumferential direction is formed into a cylindrical shape. Subsequently, as shown in FIG. 5B, the diameter of the inner belt ply 5 is expanded by expanding the diameter of the bladder 12, and tension is applied to the organic fiber cord 5C.

  Next, as shown in FIG. 5 (c), a pair of split ply pieces 4a and 4b constituting the carcass ply 4 are arranged, and both end regions of the inner belt ply 5 are covered with the end portions of the split ply pieces 4a and 4b. Meanwhile, the central region of the inner belt ply 5 is opened. Thereafter, as shown in FIG. 5D, the outer belt ply 6 is formed into a cylindrical shape, and the end portions of the divided ply pieces 4a and 4b that cover both end regions of the inner belt ply 5 are connected to the inner belt ply 5 and the outer belt ply 6 And put in between. Then, a tread rubber 9 is provided on the outer periphery of the outer belt ply 6 to form a green tire as shown in FIG.

  In the example of FIG. 6, the forming drum 13 is used, but the above-described bladder 12 can also be used. As will be described later, the forming drum 13 can perform a stepwise diameter expansion operation, and corresponds to a drum-shaped member configured to be able to expand the diameter. First, as shown in FIG. 6A, a pair of split ply pieces 4 a and 4 b constituting the carcass ply 4 are disposed on the outer periphery of the bladder 12. At this stage, the surface to which the divided ply pieces 4a and 4b are attached is flat along the tire width direction, but it may be curved.

  Next, as shown in FIG. 6 (b), the diameter of the forming drum 13 is increased, the ends of the divided ply pieces 4a and 4b are raised, and the organic fiber cord 5C is inclined therewithin the tire circumferential direction. The inner belt ply 5 arranged as described above is formed into a cylindrical shape. Subsequently, as shown in FIG. 6C, the forming drum 13 is further expanded in diameter, the diameter of the inner belt ply 5 is expanded, and tension is applied to the organic fiber cord 5C. Thereafter, the end portions of the split ply pieces 4a and 4b that have been raised are returned to their original positions, and the central region of the inner belt ply 5 is opened while covering both end regions of the inner belt ply 5 with the end portions of the split ply pieces 4a and 4b. To do.

  Next, as shown in FIG. 6 (d), the outer belt ply 6 disposed so that the steel cord 6C is inclined with respect to the tire circumferential direction and opposite to the organic fiber cord 5C is formed into a cylindrical shape, The end portions of the divided ply pieces 4 a and 4 b that cover both end regions of the inner belt ply 5 are sandwiched between the inner belt ply 5 and the outer belt ply 6. Then, a tread rubber 9 is provided on the outer periphery of the outer belt ply 6 to form a green tire as shown in FIG.

  Examples that specifically show the structure and effects of the present invention will be described below. In addition, each performance evaluation of the tire was performed as follows.

(1) Steering stability performance The tire was assembled on a 15X6-JJ rim, the internal pressure was set to 220 kPa, and the tire was mounted on a 1800 cc test vehicle, and evaluated by sensory evaluation of the driver. The results are expressed as an index when Comparative Example 1 is set to 100, and the larger the value, the better the performance.

(2) Rolling resistance Rolling resistance under the conditions of load load of 4.8kN and speed of 80km / h using a uniaxial drum testing machine for measuring rolling resistance with the tire assembled on a 15X6-JJ rim and internal pressure of 210kPa. Was measured and its reciprocal was evaluated. The results are expressed as an index when Comparative Example 1 is set to 100, and the larger the value, the better the performance.

(3) Durability Performance The tire was assembled to a 15X6-JJ rim, the internal pressure was 200 kPa, the vehicle was run under the conditions of a load of 4.2 kN and a speed of 80 km / h, and the running distance when damage occurred in the tread portion was evaluated. . The results are expressed as an index when Comparative Example 1 is set to 100, and the larger the value, the better the performance.

Comparative Examples 1-4 and Examples 1-3
In tires having a size of 195 / 65R15, those having the structure shown in Table 1 were designated as Comparative Examples 1 to 4 and Examples 1 to 3, respectively. The up structure in Comparative Example 1 is a carcass ply that is wound around the bead core from the inside to the outside. In Comparative Examples 1 and 2, the hollow structure is not employed, and the carcass ply is disposed inside the inner belt ply in the tread portion. Examples 1 to 3 are all manufactured by the method shown in FIG.

  As shown in Table 1, in Examples 1 to 3, the rolling resistance can be reduced as compared with Comparative Examples 1 to 4, while ensuring steering stability performance and durability performance. That is, in the tire manufactured according to the present invention, the inner belt ply made of an organic fiber cord is used, but the steel cord is not inferior to the case where the steel cord is used in terms of steering stability performance and durability performance, and the organic fiber cord is used. Thus, the rolling resistance can be reduced.

DESCRIPTION OF SYMBOLS 1a Bead core 3 Tread part 4 Carcass ply 4a Divided ply piece 4b Divided ply piece 5 Inner belt ply 5C Organic fiber cord 6 Outer belt ply 6C Steel cord 11 Rigid core 12 Bladder 13 Molding drum

Claims (5)

In the method for manufacturing a pneumatic radial tire in which the carcass ply is divided in the tire width direction in the center region of the tread portion,
Forming the inner belt ply arranged so that the organic fiber cord is inclined with respect to the tire circumferential direction into a cylindrical shape, and expanding the diameter of the inner belt ply formed into the cylindrical shape;
Disposing a pair of split ply pieces constituting the carcass ply, covering both end regions of the inner belt ply with ends of the pair of split ply pieces, and opening a central region of the inner belt ply;
An outer belt ply arranged in a cylindrical shape so that a steel cord is inclined with respect to the tire circumferential direction and opposite to the organic fiber cord is formed into a cylindrical shape, and And a step of sandwiching an end portion between the inner belt ply and the outer belt ply. A method for manufacturing a pneumatic radial tire, comprising:   2. The pneumatic radial according to claim 1, wherein an inclination angle of the organic fiber cord with respect to a tire circumferential direction is within a range of 20 to 45 ° before the diameter of the inner belt ply formed into a cylindrical shape is expanded. Tire manufacturing method.   The method for manufacturing a pneumatic radial tire according to claim 1 or 2, wherein when the diameter of the inner belt ply formed in a cylindrical shape is expanded, an expansion rate of the inner belt ply is set to 3 to 15%. The method for manufacturing a pneumatic radial tire according to any one of claims 1 to 3, wherein a tensile modulus of a cord of the inner belt ply is 25000 N / mm ² or more. The method of manufacturing a pneumatic radial tire according to any one of claims 1 to 4, wherein the pair of split ply pieces are respectively wound around the bead core from the outside to the inside.

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