JP6743563B2 - Pneumatic tire and manufacturing method thereof - Google Patents

Description

The present invention relates to a pneumatic tire including at least one tire constituent member having a splice portion formed at an arbitrary position in the tire circumferential direction and a method for manufacturing the pneumatic tire, and more specifically, to improve air dispersibility during vulcanization. The present invention relates to a pneumatic tire capable of effectively suppressing a blister failure and a manufacturing method thereof.

When vulcanizing a pneumatic tire, a vulcanization failure called a blister failure may occur. Blister failure is caused by moisture and residual air contained in rubber, as well as air remaining at the step formed at the end of the tire component during tire molding is locally collected during vulcanization, and bubbles generated by it are generated. This is a failure in which the blister is not completely dispersed during vulcanization and becomes a blister and remains in the tire. Moisture and residual air contained in rubber foam innumerably in the early stage of vulcanization, but most of the bubbles are microdispersed and disappear during vulcanization. However, when micro-dispersed, air bubbles are aggregated in a portion where the pressure is weak, and re-foaming may occur after vulcanization to form a blister.

In order to suppress blister failure, the tire components are pressed by a stitcher during tire molding to promote air dispersion, and during vulcanization, air is exhausted through a vent hole provided on the inner surface of the mold. However, the air remaining inside the tire cannot be sufficiently removed by itself.

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

However, when arranging the organic fiber cord for air absorption on at least one surface of the carcass layer as described above, the organic fiber cord has a rolling direction similar to that of the carcass cord in the rolling process of the tire constituent member to be the carcass layer. It is generally arranged along with. On the other hand, in the green tire molding process, when splicing the tire circumferential end portions of a tire constituent member such as a carcass layer, the stepped portion formed by the spliced portion extends along the tire width direction. Will be done. Therefore, the organic fiber cord for air absorption attached to the tire constituent member as described above extends substantially parallel to the splice portion of the tire constituent member, resulting in a step formed by the splice portion. Very unlikely to come into contact with parts. As a result, the air remaining in the stepped portion formed by the splice portion cannot be reliably removed, and the blister failure due to the air remaining in this portion cannot be suppressed under the present circumstances.

International Publication No. WO2013/035555

An object of the present invention is to provide a pneumatic tire capable of improving air dispersibility during vulcanization and effectively suppressing blister failure, and a method for manufacturing the pneumatic tire.

A pneumatic tire of the present invention for achieving the above object is a pneumatic tire including at least one tire constituent member having a splice portion formed at an arbitrary position in a tire circumferential direction, the pneumatic tire being formed by the splice portion. At least one yarn having a breaking strength of 100 N or less and extending in the tire width direction is arranged in the step portion.

Further, the method for manufacturing a pneumatic tire of the present invention for achieving the above-mentioned object includes at least one tire constituent member having a splice portion formed at an arbitrary position in the tire circumferential direction, and is formed by the splice portion. A green tire having a breaking strength of 100 N or less and at least one thread extending in the tire width direction is formed in a step portion, and the green tire is vulcanized. is there.

According to the present invention, in a pneumatic tire including at least one tire constituent member having a splice portion formed at an arbitrary position in the tire circumferential direction, at least 1 extending in the tire width direction at a step portion formed by the splice portion. By arranging the threads of the book, the air remaining in the step portion can be effectively dispersed by the threads, so that the air dispersibility during vulcanization can be improved and the blister failure can be effectively suppressed. it can.

In the present invention, the breaking strength of the yarn needs to be 100 N or less. Since this yarn is intended to improve the air dispersibility and is not a reinforcing member, it is possible to minimize the influence on the behavior of the tire constituent member by limiting the upper limit of the breaking strength thereof. In particular, the yarn is preferably composed of synthetic fibers or natural fibers.

When manufacturing the pneumatic tire of the present invention, the pneumatic tire is provided with at least one tire constituent member in which a splice portion is formed at an arbitrary position in the tire circumferential direction, and a breaking strength is 100 N or less in a step portion formed by the splice portion. Thus, a green tire in which at least one thread extending in the tire width direction is arranged is formed. At that time, in the step of forming the green tire, when the tire constituent member is cut in accordance with the tire specifications, a thread may be attached to the cut end portion, or it is formed by the splice portion of the tire constituent member. A thread may be attached to the step portion. As described above, after molding the green tire having the thread in the stepped portion formed by the splice portion, the green tire may be vulcanized.

It is a meridian half cross section which shows the pneumatic tire which consists of embodiment of this invention. FIG. 3 is a development view showing a state in which threads are arranged in a step portion formed by a splice portion of a carcass layer (tire constituent member) in the method for manufacturing a pneumatic tire of the present invention. FIG. 3 is a sectional view taken along the line III-III in FIG. 2. FIG. 3 is a cutaway perspective view showing a green tire in the pneumatic tire manufacturing method of the present invention.

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. 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. A two-layer carcass layer 4 including a plurality of reinforcing cords extending in the tire radial direction is mounted between the pair of left and right bead portions 3, 3 and the end portion of the carcass layer 4 surrounds the bead core 5 from the inside of the tire. It is folded back to the outside. A bead filler 6 made of a rubber composition having a high hardness is arranged on the outer periphery of the bead core 5, and the bead filler 6 is wrapped in a 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 the reinforcing cords are arranged so as to intersect each other between the layers. An inner liner layer 8 is arranged along the carcass layer 4 on the inner surface of the tire.

Tire constituent members represented by the carcass layer 4 and the belt layer 7 are embedded in the pneumatic tire. For example, as shown in FIGS. 2 and 3, the carcass layer 4 is a member including a plurality of carcass cords C extending along the tire width direction Tw, but the carcass layer 4 has an end portion in the tire circumferential direction Tc. A splice portion S is formed at an arbitrary position in the tire circumferential direction Tc by overlapping the 4a and 4b with each other. Then, at the step portion formed by the splice portion S, at least one yarn 10 having a breaking strength of 100 N or less is arranged so as to extend in the tire width direction Tw. More specifically, as shown in FIG. 3, in the splice portion S of the carcass layer 4, a step is formed at a portion adjacent to the end surface of the end portion 4a of the carcass layer 4 and a portion adjacent to the end surface of the end portion 4b. However, the thread 10 is arranged in each of these step portions. Similarly, at least one thread 10 extending in the tire width direction Tw is also arranged at the step portion formed by the splice portion S of the belt layer 7. In any case, it is desirable that the yarn 10 be arranged within a range of 3 mm from the end surface of the tire constituent member such as the carcass layer 4 and the belt layer 7. By arranging the thread 10 at a position close to the end surface of the tire constituent member, the thread 10 effectively functions as a distribution path of air remaining in the step portion.

When manufacturing the pneumatic tire as described above, the carcass layer 4 and the belt layer 7 each having the splice portion S formed at an arbitrary position in the tire circumferential direction are provided as tire constituent members, and the carcass layer 4 and the belt layer 7 are provided. The green tire G (see FIG. 4) in which the thread 10 extending in the tire width direction is arranged in the stepped portion formed by the splice portion S is molded. In the green tire G, the thread 10 extends along the step portion formed by the splice portion S. Such a thread 10 is inserted inside the green tire G at any time during the process of reaching the green tire G.

For example, in the molding process of the green tire G, when the carcass layer 4 which is a tire constituent member is cut in accordance with the tire specifications, the thread 10 can be attached to the cut ends 4a and 4b. Alternatively, after the carcass layer 4 that is a tire constituent member is attached to the periphery of the forming drum to splice the end portions 4a and 4b in the tire circumferential direction, the thread 10 is attached to the step portion formed by the splice portion S. be able to. In any case, the worker may manually attach the thread 10 or may use a device for ejecting the thread 10.

Thus, after molding the green tire G in which the thread 10 is arranged at the step portion formed by the splice portion S of the carcass layer 4 or the belt layer 7, the green tire G is vulcanized to obtain the above-mentioned pneumatic You can get tires.

In the vulcanization step, the unvulcanized green tire G is put into a mold and heated while applying pressure from inside the tire with a bladder. At that time, moisture and air remaining inside the tire are foamed in the initial stage of vulcanization, but most of the bubbles are microdispersed and disappear during vulcanization. However, air bubbles tend to be locally collected at a portion where the pressure is weak during micro dispersion. In particular, the air remaining in the step portion formed by the splice portion S of the carcass layer 4 or the belt layer 7 causes air accumulation. On the other hand, by disposing at least one yarn 10 extending in the tire width direction at a step portion formed by the splice portion S of the carcass layer 4 or the belt layer 7, air remaining in the step portion is removed. Since it can be effectively dispersed based on the yarn 10, the air dispersibility during vulcanization can be improved, and blister failure can be effectively suppressed.

In the pneumatic tire, the breaking strength of the yarn 10 is 100 N or less, and more preferably 1 N to 5 N. Since the yarn 10 is intended to improve air dispersibility and is not a reinforcing member, the upper limit of the breaking strength of the yarn 10 can be regulated to minimize the influence on the behavior of the tire constituent member. .. If the breaking strength of the yarn 10 is too large, the tire performance may be unintentionally affected.

The constituent material of the yarn 10 is not particularly limited, but for example, synthetic fibers such as nylon, polyester, rayon and the like, as well as natural fibers such as cotton can be used. The total fineness of the yarn 10 is preferably in the range of 25 dtex to 170 dtex. This makes it possible to reduce the breaking strength and ensure good air dispersibility.

In the above-described embodiment, the case where the yarn 10 is arranged at the step portion formed by the splice portion S of the carcass layer 4 or the belt layer 7 has been described. The thread 10 can be arranged in the step portion. Examples of such tire constituent members include a bead reinforcing layer, a side reinforcing layer, an inner liner layer, and a sidewall rubber layer. The splice portion S may extend obliquely with respect to the tire width direction. In that case, the yarn 10 may be arranged obliquely with respect to the tire width direction along the splice portion S. Further, the tire reinforcing member may include a cord or may not include a cord.

A pneumatic tire having a tire size of 235/40R18, in which at least one thread extending in the tire width direction is arranged in a stepped portion formed by a splice portion of a carcass layer (tire constituent member), to manufacture the tire of Example 1. did. As the thread, a thread made of cotton fiber and having a total fineness of 29.5 dtex was used. The breaking strength of this yarn is 1N.

Further, a tire of Conventional Example 1 having the same structure as that of Example 1 was manufactured except that the yarn was not arranged in the step portion formed by the splice portion of the carcass layer.

The tires of Example 1 and Conventional Example 1 were vulcanized. At that time, vulcanization was performed for a time shorter than the normally required vulcanization time, and the conditions were such that blister failure was likely to occur. After vulcanization, each tire was disassembled and the number of blisters generated in the splice part of the carcass layer was examined. As a result, in the tire of Example 1, the occurrence of blister failure was reduced as compared with Conventional Example 1. In particular, the number of blisters generated in the tire of Example 1 was about half the number of blisters generated in the tire of Conventional Example 1.

1 tread part 2 sidewall part 3 bead part 4 carcass layer 4a, 4b end part 5 bead core 6 bead filler 7 belt layer 8 inner liner layer 10 yarn C carcass cord S splice part

Claims (6)

In a pneumatic tire including at least one tire constituent member having a splice portion formed at an arbitrary position in the tire circumferential direction, a step strength portion formed by the splice portion has a breaking strength of 100 N or less and a tire width direction. A pneumatic tire having at least one extending yarn arranged therein. The pneumatic tire according to claim 1, wherein the yarn is made of synthetic fiber or natural fiber. The tire includes at least one tire constituent member in which a splice portion is formed at an arbitrary position in the tire circumferential direction, and at least the step strength portion formed by the splice portion has a breaking strength of 100 N or less and extends in the tire width direction. A method for producing a pneumatic tire, comprising molding a green tire in which one thread is arranged, and vulcanizing the green tire. The manufacturing of the pneumatic tire according to claim 3, wherein, in the step of forming the green tire, when the tire constituent member is cut to meet tire specifications, the thread is attached to the cut end portion. Method. The pneumatic tire manufacturing method according to claim 3, wherein, in the step of molding the green tire, the thread is attached to a step portion formed by a splice portion of the tire constituent member. The method for producing a pneumatic tire according to any one of claims 3 to 5, wherein the yarn is made of synthetic fiber or natural fiber.

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