JP2016187968A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of effectively restraining blister failure by improving air dispersibility at vulcanization on the boundary faces of plural kinds of rubber layers to be integrally molded through a rolling or extrusion process.SOLUTION: In a pneumatic tire having a cap tread rubber layer 11A and under-tread rubber layer 11B molded integrally by extrusion, at least one thread 20 is disposed on a boundary face between the above layers 11A and 11B to extend in a tire circumferential direction. The breaking strength of the thread 20 is 100 N or less, and the implantation density of the thread 20 is 5 lines/50 mm or less. Besides, in the pneumatic tire having an inner liner layer 15 and tie rubber layer 16 molded integrally by rolling, at least one thread 20 is similarly disposed on the boundary face between the above layers 15 and 16 to extend in the tire circumferential direction.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire provided with a plurality of types of rubber layers that are integrally molded by rolling or extrusion, more specifically, improving air dispersibility during vulcanization at the interface of these rubber layers, The present invention relates to a pneumatic tire that can effectively suppress a blister failure.

  When vulcanizing a pneumatic tire, a vulcanization failure called a blister failure may occur. Blister failure is caused by the moisture and residual air contained in the rubber, as well as the air remaining at the steps formed at the ends of the tire components during tire molding, which is collected locally during vulcanization and the resulting bubbles are This is a failure that does not completely disperse during vulcanization but becomes a blister and remains in the tire. Moisture and residual air contained in the rubber foam innumerably in the early stages of vulcanization, but most of the bubbles disappear by being micro-dispersed during vulcanization. However, at the site where the pressure is weak at the time of micro-dispersion, bubbles are collected and may re-foam after vulcanization to form blisters.

  To suppress blister failure, tire components are pressed by a stitcher during tire molding to promote air dispersion, and during vulcanization, air is discharged through a vent hole provided on the inner surface of the mold. However, that alone cannot sufficiently eliminate the air remaining inside the tire.

  On the other hand, based on the knowledge that an air reservoir is easily formed between the carcass layer and a member adjacent to the carcass layer, an organic fiber cord for air absorption that is not covered with rubber is disposed on at least one surface of the carcass layer. However, it has been proposed that the organic fiber cord absorbs air remaining between the carcass layer and a member adjacent thereto to prevent formation of an air pool during vulcanization (for example, Patent Document 1). reference).

  However, when an organic fiber cord for air absorption that is not rubber-coated is disposed on at least one surface of the carcass layer as described above, it is possible to absorb the air remaining between the carcass layer and the adjacent members. Although it is possible, the current situation is that blister failure cannot always be effectively suppressed. Further, when an organic fiber cord for absorbing air that is not covered with rubber is disposed on the surface of the carcass layer, the organic fiber cord may be detached in the tire molding process or may be displaced.

International Publication No. WO2013 / 035555

  The object of the present invention is to improve air dispersibility during vulcanization at the interface of a plurality of types of rubber layers that are integrally molded by rolling or extrusion, and to effectively suppress blister failure. It is to provide a pneumatic tire.

In order to achieve the above object, the pneumatic tire of the present invention is a pneumatic tire provided with a plurality of types of rubber layers integrally formed by rolling or extrusion, and at least at the interface of the plurality of types of rubber layers. One yarn is arranged, and more specifically, has the following configuration (1) or (2).
(1) In a pneumatic tire including a cap tread rubber layer and an under tread rubber layer that are integrally formed by extrusion, at least one yarn is provided at an interface between the cap tread rubber layer and the under tread rubber layer. A pneumatic tire characterized by being arranged to extend in a tire circumferential direction, wherein the breaking strength of the yarn is 100 N or less, and the thread driving density is 5 pieces / 50 mm or less.
(2) In a pneumatic tire including an inner liner layer and a tie rubber layer that are integrally formed by rolling, at least one yarn extends in the tire circumferential direction at the interface between the inner liner layer and the tie rubber layer. The pneumatic tire is characterized in that the yarn has a breaking strength of 100 N or less and a yarn driving density of 5 pieces / 50 mm or less.

  As a result of earnest research on blister failures occurring during vulcanization, the present inventor has found that blisters are formed at the interfaces between these rubber layers in a pneumatic tire having a plurality of types of rubber layers that are integrally formed by rolling or extrusion. The present inventors have found out that a failure is likely to occur and have reached the present invention.

  That is, in the present invention, air dispersibility at the time of vulcanization at the interface of the rubber layer is provided by disposing at least one yarn at the interface of the plurality of types of rubber layers that are integrally formed by rolling or extrusion. The blister failure can be effectively suppressed. In addition, when the yarn is arranged at the interface between a plurality of types of rubber layers that are integrally molded by rolling or extrusion, the tire does not detach or cause misalignment in the tire molding process. There is also an advantage that the molding process can be performed smoothly.

  In a pneumatic tire including a cap tread rubber layer and an under tread rubber layer that are integrally formed by extrusion, at least one yarn may be disposed at the interface between the cap tread rubber layer and the under tread rubber layer. preferable. As a result, air that tends to collect at the interface between the cap tread rubber layer and the undertread rubber layer during vulcanization can be dispersed by the yarn.

  In particular, the thread is in a region corresponding to 30% of the distance A from the outer end position of the interface between the cap tread rubber layer and the under tread rubber layer with respect to the distance A from the outer end position of the under tread rubber layer to the tire center line. Is preferably arranged. Since the tire shoulder portion is weak in the pressure applied at the time of micro-dispersion at the initial stage of vulcanization, air bubbles are easily formed. However, by arranging the yarn in the region A, blister failure can be effectively suppressed.

  In a pneumatic tire provided with a tread rubber layer and an edge rubber layer that are integrally formed by extrusion, it is preferable to dispose at least one yarn at the interface between the tread rubber layer and the edge rubber layer. As a result, air that tends to collect at the interface between the tread rubber layer and the edge rubber layer during vulcanization can be dispersed by the yarn. The tire shoulder portion is weak in the pressure applied at the time of micro-dispersion at the initial stage of vulcanization, so that bubbles are likely to be formed. However, the blister failure can be effectively suppressed by arranging the yarn in the above-mentioned part.

  In a pneumatic tire including a side rubber layer and a rim cushion rubber layer that are integrally formed by extrusion, it is preferable to dispose at least one yarn at the interface between the side rubber layer and the rim cushion rubber layer. As a result, air that tends to collect at the interface between the side rubber layer and the rim cushion rubber layer during vulcanization can be dispersed by the yarn. Since the rim cushion portion is weak in the pressure applied at the time of micro dispersion at the initial stage of vulcanization, bubbles are likely to be formed. However, it is possible to effectively suppress blister failure by arranging the yarn at the above-mentioned part.

  In a pneumatic tire provided with an inner liner layer and a tie rubber layer that are integrally formed by rolling, it is preferable to dispose at least one yarn at the interface between the inner liner layer and the tie rubber layer. As a result, air that tends to collect at the interface between the inner liner layer and the tie rubber layer during vulcanization can be dispersed by the yarn.

  In the present invention, the yarn is preferably arranged so as to extend in the tire circumferential direction. When inserting a thread | yarn by an extrusion process or a rolling process, the continuous insertion of a thread | yarn can be performed easily by extending the thread | yarn along an extrusion direction or a rolling direction. As a result, a structure in which the yarn is oriented in the tire circumferential direction is obtained. Moreover, when arrange | positioning so that a thread | yarn may extend in a tire circumferential direction, the air which remains between the layers of a rubber layer can be disperse | distributed effectively along a tire circumferential direction.

  The breaking strength of the yarn is preferably 100 N or less. Since this yarn is intended to improve air dispersibility and is not a reinforcing member, the influence on the behavior of the rubber layer can be minimized by regulating the upper limit value of the breaking strength.

  The thread driving density is preferably 5 pieces / 50 mm or less. Since this yarn is intended to improve air dispersibility and is not a reinforcing member, the influence on the behavior of the rubber layer can be minimized by restricting the upper limit value of the driving density.

It is a meridian half section view showing a pneumatic tire according to an embodiment of the present invention. It is sectional drawing which shows the tread rubber layer and edge rubber layer in which the thread | yarn was inserted in the interface. It is sectional drawing which shows the side rubber layer and rim cushion rubber layer in which the thread | yarn was inserted in the interface. It is sectional drawing which shows the inner liner layer and tie rubber layer in which the thread | yarn was inserted in the interface.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic tire according to an embodiment of the present invention, and FIGS. 2 to 4 show components of the pneumatic tire. Although FIG. 1 shows only a portion on one side of the tire center line CL, this pneumatic tire has a structure corresponding to the other side of the tire center line CL.

  In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. Between the pair of left and right bead portions 3, 3, a two-layer carcass layer 4 including a plurality of reinforcing cords extending in the tire radial direction is mounted, and an end portion of the carcass layer 4 extends around the bead core 5 from the inside of the tire. It is folded outside. A bead filler 6 made of a rubber composition having a high hardness is disposed on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by the carcass layer 4.

  A plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers.

  A tread rubber layer 11 is disposed on the outer peripheral side of the belt layer 7 in the tread portion 1. The tread rubber layer 11 includes a cap tread rubber layer 11A exposed on the outer surface of the tire and an under tread rubber layer 11B located on the inner side in the tire radial direction of the cap tread rubber layer 11A. Further, edge rubber layers 12 are disposed on both outer sides of the tread rubber layer 11 in the tire width direction. The cap tread rubber layer 11A, the under tread rubber layer 11B, and the edge rubber layer 12 are integrally formed by extrusion, and then used for the tire forming process as an integral tire constituent member (see FIG. 2).

  A side rubber layer 13 is disposed outside the carcass layer 4 in the tire width direction in the sidewall portion 2, and a rim cushion rubber layer 14 adjacent to the side rubber layer 13 is disposed in the bead portion 3. The side rubber layer 13 and the rim cushion rubber layer 14 are integrally formed by an extrusion process, and thereafter used as an integral tire constituent member (see FIG. 3) for the tire forming step.

  Further, a laminated body of an inner liner layer 15 and a tie rubber layer 16 is disposed along the carcass layer 4 on the inner surface of the tire. The inner liner layer 15 is exposed on the inner surface of the tire, and the tie rubber layer 16 is interposed between the carcass layer 4 and the inner liner layer 15. The inner liner layer 15 and the tie rubber layer 16 are integrally formed by rolling, and are then used as an integral tire component (see FIG. 4) for the tire forming step.

  In the pneumatic tire, a plurality of types of rubber layers (for example, cap tread rubber layer 11A, under tread rubber layer 11B, edge rubber layer 12, side rubber layer 13, rim cushion rubber layer, which are integrally formed by rolling or extruding. 14, at least one thread 20 (see FIGS. 2 to 4) is disposed at the interface between the inner liner layer 15 and the tie rubber layer 16).

  In the case of vulcanizing the pneumatic tire configured as described above, an unvulcanized tire molded through the tire molding process is put into a mold and heated while applying pressure from the inside of the tire by a bladder. At that time, moisture and air remaining inside the tire are foamed at the initial stage of vulcanization, but most of the bubbles are dispersed microscopically during vulcanization and disappear. However, bubbles tend to gather locally at a site where the applied pressure is weak during micro-dispersion. On the other hand, by disposing at least one yarn 20 at the interface of a plurality of types of rubber layers that are integrally formed by rolling or extrusion, the air dispersibility during vulcanization at the interface of the rubber layer is improved. The blister failure can be effectively suppressed. In addition, when the yarn 20 is disposed at the interface between a plurality of types of rubber layers that are integrally molded by rolling or extrusion, the yarn 20 does not come off or cause a displacement in the tire molding process. The tire molding process can be performed smoothly.

  Hereinafter, when a cap tread rubber layer 11A and an under tread rubber layer 11B that are integrally formed by extrusion are described, a more specific structure will be described. As shown in FIG. 2, the cap tread rubber layer 11A and the under tread are provided. At least one thread 20 may be disposed at the interface with the rubber layer 11B. In FIG. 2, the yarn 20 extends in the tire circumferential direction and is disposed so as to exist in the entire region in the tire circumferential direction. As a result, air that tends to collect at the interface between the cap tread rubber layer 11A and the undertread rubber layer 11B during vulcanization can be dispersed in the tire circumferential direction by the yarn 20.

  In particular, the distance A from the outer end position of the undertread rubber layer 11B to the tire center line CL corresponds to 30% of the distance A from the outer end position of the interface between the cap tread rubber layer 11A and the undertread rubber layer 11B. The yarn 20 may be selectively disposed in the region X to be used. Since the tire shoulder portion is weak in the pressure applied at the time of micro-dispersion at the initial stage of vulcanization, bubbles are easily formed. However, by arranging the yarn 20 in the region A, blister failure can be effectively suppressed. Here, it is possible to arrange the yarn 20 at a position deviating from the region X. However, when the yarn 20 is selectively arranged in the region X corresponding to 30% of the distance A, air dispersion is most effective. Can be done. The distance A and the region X are specified in a state where the cap tread rubber layer 11A and the under tread rubber layer 11B are spread on a plane.

  Further, when the tread rubber layer 11 and the edge rubber layer 12 are integrally formed by extrusion, as shown in FIG. 2, at least one interface is formed at the interface between the tread rubber layer 11 and the edge rubber layer 12 as described above. It is preferable to arrange the thread 20. As a result, air that tends to collect at the interface between the tread rubber layer 11 and the edge rubber layer 12 during vulcanization can be dispersed in the tire circumferential direction by the yarn 20. Since the tire shoulder portion is weak in the pressure applied at the time of micro dispersion at the initial stage of vulcanization, bubbles are likely to be formed, but the blister failure can be effectively suppressed by disposing the yarn 20 at the above-mentioned site. The tread rubber layer 11 may be a laminate of a cap tread rubber layer 11A and an under tread rubber layer 11B made of different rubber compositions, or may be composed of a single type of rubber composition. There may be.

  Further, when the side rubber layer 13 and the rim cushion rubber layer 14 that are integrally formed by extrusion are provided, as shown in FIG. 3, at least one thread 20 is provided at the interface between the side rubber layer 13 and the rim cushion rubber layer 14. It is good to place. In FIG. 3, the yarn 20 extends in the tire circumferential direction and is disposed so as to exist in the entire region in the tire circumferential direction. As a result, air that tends to collect at the interface between the side rubber layer 13 and the rim cushion rubber layer 14 during vulcanization can be dispersed in the tire circumferential direction by the yarn 20. Since the rim cushion portion is weak in the pressure applied at the time of micro-dispersion at the initial stage of vulcanization, bubbles are likely to be formed, but the blister failure can be effectively suppressed by arranging the yarn 20 at the above-mentioned site.

  Further, when the inner liner layer 15 and the tie rubber layer 16 that are integrally formed by rolling are provided, as shown in FIG. 4, at least one yarn 20 is disposed at the interface between the inner liner layer 15 and the tie rubber layer 16. Good. In FIG. 4, the thread | yarn 20 is arrange | positioned so that it may extend in the tire circumferential direction and may exist in the whole region of a tire circumferential direction. As a result, air that tends to collect at the interface between the inner liner layer 15 and the tie rubber layer 16 during vulcanization can be dispersed in the tire circumferential direction by the yarn 20.

  In the pneumatic tire described above, it is desirable to arrange the yarn 20 so as to extend in the tire circumferential direction, but other arrangements are also possible. When inserting the thread | yarn 20 in an extrusion process or a rolling process, the continuous insertion of the thread | yarn 20 can be easily performed by extending the thread | yarn 20 along an extrusion direction or a rolling direction. As a result, a structure in which the yarn 20 is oriented in the tire circumferential direction is obtained.

  The breaking strength of the yarn 20 is 100 N or less, more preferably 1N to 5N. Since the yarn 20 is intended to improve air dispersibility and is not a reinforcing member, the influence on the behavior of the rubber layer can be minimized by regulating the upper limit value of the breaking strength. If the breaking strength of the yarn 20 is too large, the tire forming process may be adversely affected.

  Although the constituent material of the thread | yarn 20 is not specifically limited, Natural fibers, such as cotton other than synthetic fibers, such as nylon, polyester, and rayon, can be used, for example. The total fineness of the yarn 20 is preferably in the range of 25 dtex to 170 dtex. As a result, the breaking strength can be lowered and good air dispersibility can be ensured.

  The driving density of the yarn 20 is preferably 5 pieces / 50 mm or less. Since the yarn 20 is intended to improve air dispersibility and is not a reinforcing member, the influence on the behavior of the rubber layer can be minimized by restricting the upper limit value of the driving density. If the driving density of the yarn 20 is too large, the tire forming process may be adversely affected. The driving density of the yarn 20 is specified from the mutual interval of the yarn 20. For example, when the mutual interval between the yarns 20 is P mm, the driving density (lines / 50 mm) of the yarns 20 is 50 / P. Further, when the number of driven yarns 20 at each interface is one, the driven density is considered to be 5/50 mm or less.

  In a pneumatic tire of tire size 225 / 65R17, two yarns are arranged at the interface between the cap tread rubber layer and the under tread rubber layer, and two yarns are arranged at the interface between the tread rubber layer and the edge rubber layer, A tire of Example 1 was manufactured in which one thread was disposed at the interface between the side rubber layer and the rim cushion rubber layer, and eight threads were disposed at the interface between the inner liner layer and the tie rubber layer. Further, a tire of Conventional Example 1 having the same structure as Example 1 was manufactured except that no yarn was arranged at each interface of the rubber layer.

  In Example 1, the distance A from the outer end position of the undertread rubber layer to the tire center line corresponds to 30% of the distance A from the outer end position of the interface between the cap tread rubber layer and the undertread rubber layer. A thread was selectively placed in the area. As the yarn, a yarn made of cotton fiber and having a total fineness of 29.5 dtex was used. The breaking strength of this yarn is 1N.

  Each of the 96 tires of Example 1 and Conventional Example 1 was vulcanized, and after vulcanization, the presence or absence of blister failure in each tire was inspected to determine the incidence of blister failure. As a result, in the tire of Example 1, the occurrence of blister failure was reduced in each part of the shoulder portion, the rim cushion portion, and the tire inner surface in comparison with Conventional Example 1. The occurrence rate of blister failure in Example 1 was about 14% of the occurrence rate of blister failure in Conventional Example 1.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 11 Tread rubber layer 11A Cap tread rubber layer 11B Under tread rubber layer 12 Edge rubber layer 13 Side rubber layer 14 Rim cushion rubber layer 15 Inner liner layer 16 Tie rubber layer 20 Thread CL Tire center line

Claims (2)

  In a pneumatic tire including a cap tread rubber layer and an under tread rubber layer that are integrally formed by extrusion, at least one yarn is provided in the tire circumferential direction at an interface between the cap tread rubber layer and the under tread rubber layer. The pneumatic tire is characterized in that the yarn has a breaking strength of 100 N or less and a yarn driving density of 5 pieces / 50 mm or less.   In a pneumatic tire including an inner liner layer and a tie rubber layer that are integrally formed by rolling, at least one yarn extends in the tire circumferential direction at an interface between the inner liner layer and the tie rubber layer. A pneumatic tire is provided, wherein the yarn has a breaking strength of 100 N or less and a yarn driving density of 5 pieces / 50 mm or less.

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