JP6743571B2 - Pneumatic tire manufacturing method - Google Patents

Description

The present invention relates to a method for producing a pneumatic tire, in which a green tire including a belt-shaped tire constituent member is molded, and the green tire is vulcanized. More specifically, the air dispersibility during vulcanization is improved and a blister failure occurs. The present invention relates to a method for manufacturing a pneumatic tire capable of effectively suppressing the above.

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 to disperse the residual air between the carcass layer and the member adjacent thereto through the organic fiber cord to prevent the formation of an air pocket during vulcanization (for example, Patent Document 1). reference).

However, when arranging the organic fiber cords for air absorption on at least one surface of the carcass layer as described above, the air dispersibility is improved as the number of arranged fibers is increased, but the organic fiber cords for air absorption are tires. It does not contribute to the performance, and moreover, as the number of organic fiber cords for air absorption increases, the adhesiveness with the adjacent member deteriorates, and the manufacturing cost increases, so the number of arrangements is naturally limited. Therefore, it is difficult for such an organic fiber cord for absorbing air to secure air dispersibility over the entire region of the tire constituent member.

As another method, it has been proposed to provide a plurality of grooves on the surface of the tire constituent member made of rubber in contact with other members, and to promote air dispersion through these grooves (for example, Patent Document 1). 2-4).

However, when a plurality of grooves are provided on the surface of the tire constituent member, these grooves disperse the air inside the green tire, and at the same time, the grooves themselves cause an increase in the air inside the tire. Therefore, when the green tire is pressed into the mold in the vulcanization process, the air inside the groove cannot be dispersed unless sufficient pressure is applied to the groove, which may cause product failure. is there.

International Publication No. WO2013/035555 JP-A-6-55659 JP, 7-308984, A JP, 2004-284165, A

An object of the present invention is to provide a method for producing a pneumatic tire, which improves air dispersibility during vulcanization and effectively suppresses blister failure.

A method for manufacturing a pneumatic tire of the present invention for achieving the above object, a plurality of yarns are attached in parallel to one surface of a first tire constituent member formed into a belt shape, while a plurality of threads are formed into a belt shape. A plurality of grooves are formed in parallel on one surface of the second tire constituent member, and the second tire constituent member is arranged so that each of the grooves comes into contact with at least one of the threads. It is characterized in that it is laminated on a tire constituent member, a green tire including these first and second tire constituent members is molded, and the green tire is vulcanized.

In the present invention, a plurality of threads are attached in parallel on one surface of the first tire constituent member, while a plurality of grooves are formed in parallel on one surface of the second tire constituent member, and By stacking the second tire component on the first tire component so that each is in contact with at least one thread, the air remaining between the first and second tire components is separated from each other. Since it becomes possible to effectively disperse through the intersecting yarns and grooves, it is possible to improve the air dispersibility during vulcanization and effectively suppress the blister failure. In particular, since the air collected inside the groove is surely dispersed through the thread that comes into contact with the groove, it is possible to prevent the groove itself from becoming a factor of residual air. Further, since the air and the groove cooperate with each other to promote air dispersion, excellent air dispersibility can be secured over the entire joint surface of the first and second tire constituent members, while air dispersion is achieved. There is also an advantage that it is not necessary to excessively arrange the yarns.

In the present invention, the distance between the yarns in the first tire constituent member in the tire circumferential direction is W (mm), the inclination angle of the yarns in the first tire constituent member with respect to the tire circumferential direction is θ (°), When the width of the joint surface of the second tire constituent member to the first tire constituent member is H (mm), the inclination angle α (°) of the groove formed in the second tire constituent member with respect to the tire circumferential direction is lower. It is preferable to satisfy the formula (1) or (2). As a result, the groove and the yarn can be surely brought into contact with each other, and a sufficient air movement path can be secured.

In the present invention, the breaking strength of the yarn is preferably 100N 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.

In the present invention, although the first and second tire constituent members are not particularly limited, for example, when the first tire constituent member is a carcass layer and the second constituent member is a sidewall rubber layer. Suitable for Alternatively, it is also suitable when the first tire constituent member is a belt layer and the second tire constituent member is a tread rubber layer.

It is a meridian half cross section which shows an example of the pneumatic tire manufactured by the manufacturing method of the pneumatic tire of this invention. FIG. 3 is a development view showing a state in which a sidewall rubber layer (second tire constituent member) is laminated on a carcass layer (first tire constituent member) in the method for manufacturing a pneumatic tire of the present invention. It is a development view showing a sidewall rubber layer with a groove used in a manufacturing method of a pneumatic tire of the present invention. It is a development view showing a carcass layer with a thread used in a manufacturing method of a pneumatic tire of the present invention. It is a front view showing an example of a green tire obtained by a manufacturing method of a pneumatic tire 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, and FIGS. 2 to 5 show a manufacturing method thereof. 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.

A tread rubber layer 11 is arranged on the outer peripheral side of the belt layer 7 in the tread portion 1. A sidewall rubber layer 12 exposed on the outer surface of the tire is provided in the sidewall portion 2. Further, the bead portion 3 is provided with a rim cushion rubber layer 13 exposed on the outer surface of the tire. On the other hand, an inner liner layer 14 is arranged along the carcass layer 4 on the inner surface of the tire.

When manufacturing the pneumatic tire configured as described above, the green tire G (see FIG. 5) is molded by bonding various tire constituent members on the molding drum. For example, as shown in FIG. 2, after a band-shaped carcass layer 4 (first tire constituent member) is wound around a molding drum in the tire circumferential direction Tc, a band-shaped sidewall is formed on the carcass layer 4. There is a step of attaching the rubber layer 12 (second tire constituent member). Here, a plurality of threads 10 are attached in parallel to one surface of the carcass layer 4 so as to extend along the tire width direction Tw. Such a yarn 10 can be attached to the surface of the carcass layer 4 in advance in the calendar process of the carcass layer 4. On the other hand, on one surface of the sidewall rubber layer 12 (bonding surface with the carcass layer 4), as shown in FIG. 3, a plurality of grooves 20 are arranged in parallel so as to intersect the yarn 10 of the carcass layer 4. Is formed in. Such a groove 20 can be appropriately processed after the extrusion process of the sidewall rubber layer 12. When the sidewall rubber layer 12 is laminated on the carcass layer 4, it is necessary to arrange both of them so that each groove 20 is in contact with at least one yarn 10.

As shown in FIG. 4, the distance in the tire circumferential direction Tc of the yarn 10 in the carcass layer 4 (first tire constituent member) is W (mm), and the yarn 10 in the carcass layer 4 (first tire constituent member) is shown. Is θ (°) with respect to the tire circumferential direction Tc, and the width of the joint surface of the sidewall rubber layer 12 (second tire constituent member) to the carcass layer 4 (first tire constituent member) is H (mm ), the inclination angle α (°) of the groove 20 formed in the sidewall rubber layer 12 (second tire constituent member) with respect to the tire circumferential direction Tc satisfies the following expression (1) or (2). Is good. That is, the inclination direction of the groove 20 is preferably included in the ranges X1 and X2 shown in FIG. As a result, the groove 20 and the yarn 10 can be surely brought into contact with each other, and a sufficient air movement path can be secured.

In particular, when the inclination angle α (°) of the groove 20 with respect to the tire circumferential direction Tc satisfies the following expression (3) or (4), the length of the groove 20 is shortened as much as possible, and The yarn 10 can be reliably brought into contact with each other.

After molding the green tire G including the carcass layer 4 (first tire constituent member) and the sidewall rubber layer 12 (second tire constituent member) in this manner, the green tire G is vulcanized. The pneumatic tire described above can be obtained.

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, air remaining in a portion where two tire constituent members are bonded, such as an interface between the carcass layer 4 and the sidewall rubber layer 12, causes air accumulation. On the other hand, while the plurality of threads 10 are attached in parallel to one surface of the carcass layer 4, the plurality of grooves 20 are formed in parallel on one surface of the sidewall rubber layer 12, and By stacking the sidewall rubber layer 12 on the carcass layer 4 so that each of them contacts the at least one yarn 10, the air remaining between the carcass layer 4 and the sidewall rubber layer 12 intersects with each other. It can be effectively dispersed through the thread 10 and the groove 20. As a result, the air dispersibility during vulcanization can be improved and blister failure can be effectively suppressed.

In particular, since the air collected inside the groove 20 is surely dispersed through the yarn 10 that is in contact with the groove 20, it is possible to prevent the groove 20 itself from being a factor of residual air. Further, since the air 10 is promoted by the cooperation of the thread 10 and the groove 20, the entire area of the joint surface between the carcass layer 4 and the sidewall rubber layer 12 can be provided without excessively disposing the air-dispersing thread 10. It is possible to secure excellent air dispersibility over the entire length.

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.

On the other hand, the groove 20 preferably has a groove width of about 1 mm to 3 mm and a groove depth of about 1 mm to 3 mm. Since the groove 20 has the groove width and groove depth as described above, good air dispersibility can be ensured. For the same reason, the pitch of the grooves 20 is preferably about 10 mm to 20 mm.

In the above-described embodiment, the case where the first tire constituent member is the carcass layer 4 and the second constituent member is the sidewall rubber layer 12 has been described, but in the present invention, the first tire to which the yarn 10 is applied is provided. The second tire constituent member provided with the constituent member and the groove 20 is not particularly limited. For example, a composite of the sidewall rubber layer 12 and the rim cushion rubber layer 13 can be used as the second tire constituent member. When the belt layer 7 is the first tire constituent member, the tread rubber layer 11 can be the second constituent member.

In manufacturing a pneumatic tire having a tire size of 235/40R18, a plurality of threads are attached in parallel to one surface of a carcass layer (first tire constituent member) formed in a belt shape while being formed in a belt shape. A plurality of grooves are formed in parallel on one surface of the sidewall rubber layer (second tire constituent member), and the sidewall rubber layer is used as a carcass layer so that each groove contacts at least one thread. A green tire including the carcass layer and the side wall rubber layer was formed by lamination, and the green tire was vulcanized (Example 1). 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.

A tire was manufactured by the same method as in Example 1 except that the carcass layer was provided with threads and the sidewall rubber layer was provided with grooves, but the grooves and the threads were not in contact with each other (conventional example). 1).

When the tire was vulcanized in Example 1 and Conventional Example 1, the 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 of the obtained tires was disassembled, and the number of blisters generated at the interface between the carcass layer and the sidewall rubber 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. That is, by arranging the groove and the thread so as to be in contact with each other between the two tire constituent members, a very remarkable effect for suppressing the blister failure was obtained.

1 Tread Part 2 Sidewall Part 3 Bead Part 4 Carcass Layer 5 Bead Core 6 Bead Filler 7 Belt Layer 10 Yarn 11 Tread Rubber Layer 12 Sidewall Rubber Layer 13 Rim Cushion Rubber Layer 14 Inner Liner Layer 20 Groove G Green Tire

Claims (6)

A plurality of threads are attached in parallel to one surface of the band-shaped first tire constituent member, while a plurality of grooves are arranged in parallel on one surface of the band-shaped second tire constituent member. And the second tire component is laminated to the first tire component so that each of the grooves is in contact with at least one of the threads, and the first and second tire components are formed. A method for producing a pneumatic tire, which comprises molding a green tire including a member and vulcanizing the green tire. An interval of the yarn in the tire circumferential direction in the first tire constituent member is W (mm), an inclination angle of the yarn in the first tire constituent member with respect to the tire circumferential direction is θ (°), and When the width of the joint surface of the second tire constituent member to the first tire constituent member is H (mm), the inclination angle α(of the groove formed in the second tire constituent member with respect to the tire circumferential direction [Deg.] satisfies the following formula (1) or (2).

The pneumatic tire according to claim 1 or 2, wherein the breaking strength of the yarn is 100 N or less. The method for producing a pneumatic tire according to claim 1, wherein the yarn is made of synthetic fiber or natural fiber. The method for producing a pneumatic tire according to claim 1, wherein the first tire constituent member is a carcass layer, and the second constituent member is a sidewall rubber layer. The said 1st tire structural member is a belt layer, and the said 2nd structural member is a tread rubber layer, The manufacturing method of the pneumatic tire in any one of Claims 1-4 characterized by the above-mentioned.

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