JP2006044339A - Pneumatic radial-ply tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial-ply tire capable of improving uniformity at the time of vulcanization molding an unvulcanized tire formed by assembling tire components on a rigid core using an outside-fastening type vulcanization die. <P>SOLUTION: This pneumatic radial tire is obtained by vulcanizing an unvulcanized tire formed by assembling tire components on a rigid core having a shape identical to an inner cavity of a finished tire using an outside-fastening type vulcanization die while the rigid core is mounted. When a carcass layer 4 including carcass cords reciprocating between a pair of bead parts is formed, an organic fiber cord with intermediate elongation of 5% or more and 7% or less at the time of 2.0cN/dex loading, and dry heat contraction rate of 3% or more when left at 150 °C for 30 minutes is used. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic radial tire obtained by vulcanizing and molding an unvulcanized tire obtained by assembling a tire constituent member on a rigid core using a vulcanization mold of an external fastening system. The present invention relates to a pneumatic radial tire with improved uniformity.

  Generally, when manufacturing a pneumatic radial tire, a cylindrical primary green tire including a carcass layer and a tread ring including a belt layer are respectively formed, and the axial central portion of the primary green tire is expanded. A secondary green tire is obtained by joining the primary green tire and the tread ring together. The secondary green tire is put into a mold and vulcanized while being pressed against the inner surface of the mold by a bladder inserted inside the tire. However, such a method for manufacturing a pneumatic radial tire has a drawback that the accuracy and reproducibility of the finished tire are not necessarily sufficient because the tire constituent member is greatly deformed in an unvulcanized state.

  On the other hand, as a method for manufacturing a pneumatic radial tire, after molding an unvulcanized tire on a rigid core having the same shape as the inner cavity of the finished tire, the unvulcanized tire was attached to the rigid core. It has been proposed to perform vulcanization molding using an external fastening vulcanization mold (see, for example, Patent Document 1). In such a pneumatic radial tire manufacturing method, since the tire components are not greatly deformed in all the processes from assembling the tire to vulcanization molding, it is possible to manufacture a pneumatic radial tire with high accuracy and reproducibility. It is expected to become.

However, as described above, when an vulcanized tire is vulcanized and molded using an external fastening vulcanization mold with a rigid core attached, it is different from the conventional vulcanized molding using a bladder. Since a new tension cannot be applied to the tire cord during vulcanization molding, the influence of the rubber flow during the vulcanization molding on the tension of the tire cord is increased. In other words, if the accuracy of the rubber extrudate that covers the tire cord is low, an excess rubber flow occurs during vulcanization molding, and the tire cord that is not tensioned is displaced due to the rubber flow, resulting in a uniformity of the finished tire. There is a problem of worsening.
JP 2003-39915 A

  The object of the present invention is to improve the uniformity when an unvulcanized tire formed by assembling tire components on a rigid core is vulcanized using an external fastening vulcanization mold. The object is to provide a pneumatic radial tire.

  In order to achieve the above object, the pneumatic radial tire of the present invention is an unvulcanized tire formed by assembling tire constituent members on a rigid core having the same shape as the inner cavity of the finished tire, and the rigid core is mounted on the pneumatic tire. In forming a carcass layer including a carcass cord reciprocating between a pair of bead parts in a pneumatic radial tire obtained by vulcanization molding using a vulcanization mold of an external tightening method, 2.0 cN / It is characterized by using an organic fiber cord having an intermediate elongation at dtex loading of 5% or more and 7% or less and a dry heat shrinkage of 3% or more when left at 150 ° C. for 30 minutes. .

  In the present invention, in a pneumatic radial tire obtained by vulcanizing and molding an unvulcanized tire obtained by assembling a tire constituent member on a rigid core using a vulcanization mold of an external fastening system, as a carcass cord, An organic fiber cord having a relatively large intermediate elongation at a load of 2.0 cN / dtex and a relatively large dry heat shrinkage when left at 150 ° C. for 30 minutes is used. By increasing the intermediate elongation of the carcass cord, the carcass cord can be knitted on the rigid core with uniform tension, and by increasing the dry heat shrinkage rate of the carcass cord, Can be contracted to increase the tension, thereby suppressing the effects of rubber flow. As a result, the uniformity of the pneumatic radial tire can be improved when an unvulcanized tire obtained by assembling the tire constituent members on the rigid core is vulcanized using an external fastening vulcanization mold. .

  According to the present invention, a pneumatic radial tire having high accuracy and reproducibility can be manufactured because the tire constituent member is not greatly deformed in all steps from assembling the tire to vulcanization molding.

  For intermediate elongation, in accordance with the test method for chemical fiber tire cords of JIS L1017, tensile tests were conducted at a gripping interval of 250 mm and a tensile speed of 300 mm / min, and the elongation rate of the sample cord when loaded with 2.0 cN / dtex ( %).

  The dry heat shrinkage rate was determined in accordance with the chemical fiber tire cord test method of JIS L1017, and the dry heat shrinkage rate (%) of the sample cord after heating at a sample length of 500 mm and a heating condition of 150 ° C. × 30 minutes was determined. .

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

  FIG. 1 shows a pneumatic radial tire according to an embodiment of the present invention. In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A bead core 5 in which a carcass layer 4 including a carcass cord oriented in the tire radial direction is mounted between the pair of left and right bead portions 3 and 3, and an end portion in the tire width direction of the carcass layer 4 is embedded in the bead portion 3. It is locked by. Here, the bead core 5 is divided into two in the tire axial direction, and the end of the carcass layer 4 is sandwiched between these divided pieces. On the other hand, on the outer peripheral side of the carcass layer 4 in the tread portion 1, a plurality of belt layers 6 are embedded over the entire circumference of the tire. Each of the belt layers 6 includes a plurality of reinforcing cords that are aligned with each other, and the reinforcing cords are arranged so as to intersect each other between the layers.

  Next, the manufacturing method of the pneumatic radial tire mentioned above is demonstrated. FIG. 2 shows a process of knitting a carcass cord on a rigid core, and FIG. 3 shows a process of vulcanizing and molding an unvulcanized tire using an external fastening vulcanization mold.

  In FIG. 2, the rigid core 11 has the same shape as the inner cavity of the finished tire and serves as a foundation for assembling the pneumatic radial tire. However, since the finished tire undergoes a slight dimensional change after vulcanization, the rigid core 11 does not need to exactly match the inner cavity of the finished tire. The structure of the rigid core 11 is not particularly limited as long as it maintains a stable shape during tire assembly and can be removed from the finished tire. For example, an iron splittable core can be used.

  When assembling an unvulcanized tire from a tire component using the rigid core 11 as a base, as shown in FIG. 2, the carcass cord 12 is guided along the tire radial direction, folded around the bead portion, and this is repeated. A toroidal carcass layer is formed on the rigid core 11 by reciprocating between the parts. Further, after the carcass layer is knitted, an unvulcanized tire is formed on the rigid core 11 by assembling a tire constituent member such as a belt layer or a tread rubber layer on the rigid core 11. Next, as shown in FIG. 3, the unvulcanized tire 13 is sandwiched between the rigid core 11 and an external fastening vulcanization mold 14, and the vulcanized mold 13 is vulcanized using the vulcanization mold 14. By doing so, the finished tire is obtained.

  In the pneumatic radial tire, the carcass cord constituting the carcass layer 4 has an intermediate elongation at a load of 2.0 cN / dtex of 5% to 7%, more preferably 5.5% to 7%. An organic fiber cord having a dry heat shrinkage of 3% or more, more preferably 3% or more and 5.5% or less when left at 150 ° C. for 30 minutes is used. Examples of such an organic fiber cord material include polyethylene terephthalate (PET).

  In the pneumatic radial tire described above, by making the intermediate elongation of the carcass cord relatively large, the carcass cord can be knitted on the rigid core with uniform tension, thereby improving the uniformity of the pneumatic radial tire. be able to. That is, when the carcass cord is knitted, an inevitable tension fluctuation occurs due to a minute change in the supply speed of the carcass cord, but the tension fluctuation becomes large when the intermediate elongation of the carcass cord is small and the rigidity is high. When an unvulcanized tire with a carcass layer knitted in such a situation is vulcanized, the state of biting into the inner rubber (inner liner) that has become fluidized by heat differs from carcass cord to tire uniformity. Will be adversely affected. Here, if the intermediate elongation of the carcass cord under 2.0 cN / dtex is less than 5%, the effect of suppressing the tension fluctuation of the carcass cord becomes insufficient, and conversely if it exceeds 7%, the rigidity of the carcass cord Is too low, the durability is reduced.

  In addition, by increasing the dry heat shrinkage rate of the carcass cord, the carcass cord is shrunk during vulcanization to create a tension state, thereby suppressing the influence of rubber flow, so a pneumatic radial tire The uniformity can be improved. Here, when the dry heat shrinkage rate when the carcass cord is left at 150 ° C. for 30 minutes is less than 3%, the effect of improving uniformity is insufficient.

  When manufacturing pneumatic radial tires (conventional examples, examples 1-2, and comparative examples 1-2) with tire sizes 215 / 45R17 that differ only in the physical properties of the carcass cord, they are made of iron and can be divided into rigid cores. An unvulcanized tire was assembled on top, and the unvulcanized tire was vulcanized and molded using an external vulcanization mold with a rigid core attached. For the carcass cord, the intermediate elongation at the time of loading 2.0 cN / dtex and the dry heat shrinkage rate when left at 150 ° C. for 30 minutes were set as shown in Table 1.

  These test tires were evaluated for uniformity and durability by the following test methods, and the results are also shown in Table 1.

Uniformity:
The test tire is mounted on a 17 x 7 JJ wheel, the air pressure is 200 kPa, and it is mounted on a drum testing machine equipped with a rotating drum with a diameter of 1707 mm. In accordance with the JASO C607-87 standard, radial force variation (RFV) The value from the maximum peak to the minimum peak (PP value) was measured. About the conventional example, Examples 1-2, and Comparative Examples 1-2, the said measurement was performed with respect to each five tires, and the reciprocal number of the average value was calculated | required. The evaluation results are shown as an index with the conventional example being 100. A larger index value means better uniformity.

durability:
The test tire was assembled on a 17 × 7 JJ wheel, the air pressure was 240 kPa, the load was 140% of the maximum load defined in the JATMA standard, a drum test was performed, and the travel distance until a tire failure occurred was measured. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the durability.

  As can be seen from Table 1, the tires of Examples 1 and 2 were good in both uniformity and durability in comparison with the conventional example. On the other hand, the durability of the tire of Comparative Example 1 was lowered because the intermediate elongation of the carcass cord was too large. In the tire of Comparative Example 2, the effect of improving the uniformity was insufficient because the dry heat shrinkage rate of the carcass cord was too small.

1 is a meridian half cross-sectional view showing a pneumatic radial tire according to an embodiment of the present invention. In the manufacturing method of the pneumatic radial tire of this invention, it is a perspective view which shows the process of knitting a carcass cord on a rigid core. In the manufacturing method of the pneumatic radial tire of this invention, it is sectional drawing which shows the process of vulcanization-molding an unvulcanized tire using the vulcanization metal mold | die of an external fastening system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Belt layer 11 Rigid core 12 Carcass cord 13 Unvulcanized tire 14 Vulcanization mold

Claims (3)

Vulcanization molding of an unvulcanized tire made by assembling tire components on a rigid core having the same shape as the inner cavity of the finished tire, using an external tightening vulcanization mold with the rigid core attached In forming a carcass layer including a carcass cord reciprocating between a pair of bead portions in the pneumatic radial tire obtained by the above, the intermediate elongation at a load of 2.0 cN / dtex is 5% or more and 7% or less, A pneumatic radial tire using an organic fiber cord having a dry heat shrinkage of 3% or more when left at 150 ° C. for 30 minutes. The pneumatic radial tire according to claim 1, wherein the intermediate elongation of the organic fiber cord is 5.5% or more and 7% or less. The pneumatic radial tire according to claim 1 or 2, wherein the dry heat shrinkage rate of the organic fiber cord is 3% or more and 5.5% or less.

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