JP7661814B2 - Tire manufacturing method - Google Patents

Description

This disclosure relates to a method for manufacturing tires.

Generally, when the electrical resistance of a tire increases, static electricity accumulates in the vehicle, which can cause radio interference, such as radio noise. To prevent such problems, for example, Patent Document 1 below proposes a pneumatic tire in which conductive threads are arranged on the outer surface of the carcass ply.

Patent No. 6544140

However, in the pneumatic tires described above, conductive threads are attached continuously to the outer surface of the rubber material such as the carcass ply in advance, but there is a problem that the conductive threads fall off from the outer surface of the material during the tire manufacturing process.

The present disclosure was devised in light of the above-mentioned circumstances, and its main objective is to provide a tire manufacturing method that can prevent conductive threads from falling off the outer surface of the rubber material during the manufacturing process.

The present disclosure relates to a method for manufacturing a tire, the method including a first step of attaching conductive threads to an outer surface of an unvulcanized rubber material constituting the tire to reduce the electrical resistance of the tire, the first step including a step of heating the outer surface of the rubber material prior to arranging the conductive threads and/or at the same time as arranging the conductive threads on the outer surface of the rubber material.

By adopting the above configuration, the tire manufacturing method disclosed herein can effectively prevent the conductive threads from falling off from the outer surface of the rubber material during the manufacturing process.

1 is a meridian cross-sectional view of a tire manufactured by the manufacturing method of this embodiment. FIG. FIG. 2 is a perspective view showing a manufacturing line in a first step of the present embodiment. FIG. 3 is an enlarged perspective view of the roller of FIG. 2 . FIG. 3 is an enlarged side view of the pressing surface of the roller of FIG. 2 . FIG. 11 is a perspective view showing a manufacturing line for a first step according to another embodiment of the present disclosure.

Below, an embodiment of the present disclosure will be described with reference to the drawings. The present disclosure relates to a method for manufacturing a tire having conductive yarn. The conductive yarn can reduce the electrical resistance of the tire and prevent static electricity from accumulating on the vehicle. FIG. 1 shows a meridian cross section of a tire 1 manufactured by the manufacturing method of this embodiment. As shown in FIG. 1, the tire 1 has a carcass 6, and conductive yarn 10 is attached to the outer surface of the carcass 6.

The carcass 6 includes a carcass ply 6A that extends from one bead portion 4 through the tread portion 2 to the other bead portion (not shown). Needless to say, the carcass ply 6A passes through the sidewall rubber 3G of the sidewall portion 3 between the bead portion 4 and the tread portion 2. The carcass ply 6A is formed, for example, by covering parallel carcass cords with a topping rubber. The carcass 6 in this embodiment is formed of one carcass ply 6A, but may be formed of multiple carcass plies 6A.

The carcass ply 6A includes, for example, a main body portion 6a and a folded-up portion 6b. The main body portion 6a extends from at least the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4. The folded-up portion 6b is, for example, connected to the main body portion 6a and folded back from the axially inner side to the outer side around the bead core 5.

The conductive thread 10 is arranged, for example, on the outer surface of the carcass ply 6A, and in this embodiment, extends from one bead portion 4 to the other bead portion (not shown). Note that the conductive thread 10 is shown by a dashed line in Fig. 1. It is desirable that the conductive thread 10 has an electrical resistance per unit length of 10 ⁸ Ω/cm or less. A tire in which such conductive thread 10 is arranged has low electrical resistance and can suppress the accumulation of static electricity on the vehicle.

The manufacturing method of tire 1 of the present disclosure includes a first step of attaching conductive threads 10 to the outer surface of the unvulcanized rubber material that constitutes tire 1 in order to reduce the electrical resistance of tire 1. In addition, in the manufacturing method of tire 1 of the present disclosure, publicly known matters are applied to matters that are not specifically described.

Figure 2 shows a perspective view conceptually illustrating the manufacturing line in the first process. As shown in Figure 2, the unvulcanized rubber material 15 that constitutes the tire 1 is fed by the main roller 12. The unvulcanized rubber material 15 refers to a rubber material in a state in which the rubber is not completely vulcanized and therefore has a sticky outer surface, and includes semi-vulcanized rubber material. The rubber material 15 in this embodiment is configured as a carcass ply 6A (shown in Figure 1) and contains a carcass cord inside. However, the present disclosure is not limited to such an embodiment.

The first step of the present disclosure includes a step of heating the outer surface 16 of the rubber material 15 before arranging the conductive thread 10 and/or at the same time as arranging the conductive thread 10 on the outer surface 16 of the rubber material 15. In the tire manufacturing method of the present disclosure, by adopting the above configuration, it is possible to effectively prevent the conductive thread 10 from falling off the outer surface of the rubber material 15 during the manufacturing process. The following mechanism is presumed to be the reason for this.

As described above, the first step of the present disclosure includes a step of heating the outer surface 16 of the rubber material 15, and the conductive thread 10 is placed when the adhesiveness of the outer surface 16 of the rubber material 15 has been increased by heating. Therefore, it is believed that the rubber material 15 and the conductive thread 10 are securely attached to each other, and the conductive thread 10 can be effectively prevented from falling off the outer surface 16 of the rubber material 15.

The following describes the configuration of this embodiment in more detail. Each of the configurations described below represents a specific aspect of this embodiment. Therefore, it goes without saying that the present disclosure can achieve the above-mentioned effects even if it does not include the configurations described below. Furthermore, even if any one of the configurations described below is applied alone to the manufacturing method of the present disclosure having the above-mentioned characteristics, an improvement in performance corresponding to each configuration can be expected. Furthermore, when several of the configurations described below are applied in combination, a composite improvement in performance corresponding to each configuration can be expected.

In the first step shown in FIG. 2, one conductive thread 10 is arranged in the rubber material 15, but FIG. 2 is a simplified drawing to make the embodiment easier to understand. Therefore, multiple conductive threads 10 may be arranged in the rubber material 15. In this case, multiple conductive threads 10 are arranged side by side in the width direction of the rubber material 15.

In the present disclosure, the first step may be introduced into any step of the tire manufacturing method. On the other hand, since the rubber material 15 of this embodiment is applied to the carcass ply, it undergoes an EBR step after topping in which electrons are emitted to the outer surface to promote moderate vulcanization. For this reason, it is preferable that the first step of this embodiment is applied after this EBR step. If the first step is applied before the EBR step, there is a risk of sparks being generated by the conductive thread 10 during the EBR step. More specifically, it is preferable that the first step of this embodiment is applied after the EBR step and before the cutting step of the rubber material 15.

The first step of this embodiment includes a step of pressing the conductive thread 10 against the outer surface 16 of the rubber material 15 with the pressing surface 21 of the roller 20 having a heated pressing surface 21. The pressing surface 21 of the roller 20 is also heated to an appropriate required temperature. That is, in the first step of this embodiment, the roller 20 places the conductive thread 10 on the outer surface 16 of the rubber material 15 and at the same time, the roller 20 heats the outer surface 16 of the rubber material 15. However, this disclosure is not limited to such an embodiment, and even if the outer surface of the rubber material 15 is heated by some means and then the conductive thread 10 is simply placed on the outer surface 16, the adhesiveness of the rubber material 15 can be expected to prevent the conductive thread 10 from falling off.

Although omitted in FIG. 2, a known means can be appropriately adopted as a means for heating the pressing surface 21, such as arranging and controlling an electric heating wire inside the roller 20. In addition, a known means can be appropriately adopted as a means for controlling the heating temperature of the pressing surface 21, such as detecting and controlling the temperature of the pressing surface 21 with a non-contact temperature sensor.

It is desirable that the temperature of the pressing surface 21 be set to a temperature that can increase the adhesion of the outer surface 16 of the rubber material 15, but does not cause the rubber material 15 to vulcanize. From this perspective, the temperature of the pressing surface 21 is desirably 70°C or higher, more desirably 80°C or higher, and desirably 130°C or lower, more desirably 120°C or lower.

The roller 20 presses the conductive thread 10 with a pressure that ensures that the conductive thread 10 adheres to the outer surface of the rubber material 15 and does not cause excessive deformation of the rubber material 15. From this perspective, the pressure with which the roller 20 presses the conductive thread 10 is preferably 0.1 to 2.0 MPa, and more preferably 0.2 to 1.0 MPa.

Figure 3 shows an enlarged perspective view of roller 20. Figure 4 shows an enlarged side view of pressing surface 21 of roller 20. As shown in Figures 3 and 4, roller 20 is configured in a cylindrical shape, and its outer circumferential surface is configured as pressing surface 21.

As a more desirable aspect, the pressing surface 21 of this embodiment is provided with a plurality of ridges 23 extending in a direction intersecting the roller circumferential direction. The conductive thread 10 pressed by the roller 20 having such ridges 23 is more likely to adhere to the rubber material 15, and the conductive thread 10 is further prevented from falling off.

As shown in FIG. 4, from the viewpoint of suppressing excessive deformation of the outer surface of the rubber material 15 while exerting the above-mentioned effect, the height h1 of the ridges 23 is, for example, 0.1 to 1.5 mm, and preferably 0.2 to 1.1 mm. From the same viewpoint, the distance L1 between two adjacent ridges 23 is, for example, 0.3 to 2.5 mm, and preferably 1.0 to 1.6 mm. Note that the distance L1 corresponds to the distance between the apexes of the two ridges 23 in the circumferential direction of the roller.

Conventionally, conductive threads containing metal materials have a problem in that they tend to fall off from the outer surface of the rubber material during the manufacturing process, making them difficult to use. On the other hand, the manufacturing method disclosed herein can sufficiently prevent the conductive threads from falling off, even when they contain metal materials. For this reason, the conductive threads 10 may contain metal materials. In a more preferable embodiment, the conductive threads 10 of this embodiment contain metal materials and resin materials. In such conductive threads 10, the metal material increases the conductivity, while the resin material ensures adhesion with the rubber material. Therefore, the manufacturing method of this embodiment can manufacture tires with excellent conductivity with a low defect rate.

The resin material of the conductive thread 10 may be, for example, a polyester material. The metal material of the conductive thread 10 may be, for example, SUS. In a more preferred embodiment, the conductive thread 10 of this embodiment is a blended thread containing PET short fibers and SUS short fibers.

In this embodiment, the conductive thread 10 preferably contains 10% to 30% metal material by weight. Such conductive thread 10 is less likely to fall off from the rubber material 15 and can exhibit excellent conductivity.

Figure 5 shows a perspective view conceptually illustrating a manufacturing line in the first step of another embodiment of the present disclosure. As shown in Figure 5, in the first step of this embodiment, the outer surface 16 of the rubber material 15 is heated before the conductive thread 10 is placed. Even in such an embodiment, it is possible to effectively prevent the conductive thread 10 from falling off.

In this embodiment, a heating roller 26 for heating the outer surface 16 of the rubber material 15 and an attachment roller 27 for attaching the conductive thread 10 to the outer surface of the rubber material 15 are arranged separately. In this embodiment, the conductive thread 10 does not come into contact with the heating roller 26, so that the thermal contraction of the resin material of the conductive thread 10 can be suppressed. Note that the configuration of the protrusions 23 of the roller 20 shown in Figures 3 and 4 can be applied to the attachment roller 27.

The means for heating the outer surface 16 of the rubber material 15 is not limited to the heating roller 26. For example, the conductive threads 10 can be prevented from falling off even if the outer surface 16 of the rubber material 15 is heated with a non-contact heater or a hot air dryer (not shown).

Although several embodiments of the tire manufacturing method of the present disclosure have been described in detail above, the present disclosure is not limited to the specific embodiments described above and can be modified in various ways.

As an example, a manufacturing method was prepared in which conductive threads were arranged on the outer surface of a rubber material in the manner shown in FIG. 2 or FIG. 5. Also, as a comparative example, a manufacturing method was prepared that did not include the first step of the present disclosure. The comparative example and each example are substantially the same manufacturing method, except for matters related to the first step. The comparative example and each example were tested for the frequency of the conductive threads falling off and the retention strength of the conductive threads. The test method is as follows.

<Frequency of conductive thread falling off>
For the comparative example and each example, the number of times the conductive yarn fell off when operated for the same period of time was measured.

<Retention power of conductive thread>
For the comparative example and each example, an unvulcanized rubber material with a conductive thread disposed thereon was taken, and the maximum stress when the conductive thread was peeled off from the rubber material was measured. The results are shown as an index with the maximum stress of the comparative example being set at 100. The larger this index, the better the retention force of the conductive thread, and therefore the more reliably the conductive thread can be prevented from falling off.
The test results are shown in Table 1.

As shown in Table 1, in the comparative example, the conductive thread fell off eight times when operated for the same amount of time, whereas in each of the examples, no conductive thread fell off. In addition, the retention strength of the conductive thread in the comparative example was 100 points, whereas the retention strength in each of the examples was 227 to 322 points, indicating that the retention strength of the conductive thread in each of the examples was significantly improved. As described above, it was confirmed that the tire manufacturing method disclosed herein can effectively prevent the conductive thread from falling off from the outer surface of the rubber material during the manufacturing process.

[This Disclosure]
The present disclosure is as follows: The present disclosure (1) is a method for manufacturing a tire, comprising a first step of attaching conductive threads to an outer surface of an unvulcanized rubber material constituting a tire, the conductive threads being used to reduce the electrical resistance of the tire, the first step including a step of heating the outer surface of the rubber material before arranging the conductive threads and/or at the same time as arranging the conductive threads on the outer surface of the rubber material.

Disclosure (2) is a method for manufacturing a tire according to Disclosure (1), in which the conductive thread has a diameter of 0.1 to 0.2 mm.

The present disclosure (3) is a method for manufacturing a tire according to the present disclosure (1) or (2), in which the conductive yarn includes a polyester material.

The present disclosure (4) is a method for manufacturing a tire in any combination with any of the present disclosures (1) to (3), in which the conductive yarn contains a metal material.

The present disclosure (5) is a method for manufacturing a tire according to the present disclosure (4), in which the conductive yarn contains 10% to 30% by weight of the metal material.

The present disclosure (6) is a method for manufacturing a tire in any combination with any of the present disclosures (1) to (5), in which the conductive yarn is a blended yarn of PET staple fiber and SUS staple fiber.

The present disclosure (7) is a method for manufacturing a tire in any combination with any of the present disclosures (1) to (6), in which the first step includes a step of pressing the conductive thread against the outer surface of the rubber material with the pressing surface of a roller having a heated pressing surface.

The present disclosure (8) is a method for manufacturing a tire according to the present disclosure (7), in which the temperature of the pressing surface is a temperature at which the rubber material does not vulcanize.

The present disclosure (9) is a method for manufacturing a tire according to the present disclosure (8), in which the temperature of the pressing surface is 80 to 120°C.

The present disclosure (10) is a tire manufacturing method in any combination with any of the present disclosures (7) to (9), in which the roller presses the conductive yarn with a pressure of 0.1 to 2.0 MPa.

The present disclosure (11) is a method for manufacturing a tire in any combination with any of the present disclosures (7) to (10), in which the pressing surface is provided with a plurality of ridges extending in a direction intersecting the roller circumferential direction.

The present disclosure (12) is a method for manufacturing a tire according to the present disclosure (11), in which the height of the ridge is 0.2 to 1.1 mm.

The present disclosure (13) is a method for manufacturing a tire in any combination with any of the present disclosures (1) to (12), in which the rubber material is a carcass ply.

The present disclosure (14) is a method for manufacturing a tire in any combination with any of the present disclosures (1) to (13), in which the rubber material is a carcass ply that has been subjected to an EBR process.

1 Tire 10 Conductive thread 15 Rubber material 16 Outer surface of rubber material

Claims (14)

A method for manufacturing a tire, comprising:
The method includes a first step of attaching conductive threads for reducing the electrical resistance of a tire to an outer surface of an unvulcanized rubber material constituting a tire,
The first step includes a step of heating the outer surface of the rubber material before disposing the conductive thread and/or at the same time as disposing the conductive thread on the outer surface of the rubber material.
A method for manufacturing tires. The tire manufacturing method according to claim 1, wherein the conductive thread has a diameter of 0.1 to 0.2 mm. The method for manufacturing a tire according to claim 1 or 2, wherein the conductive yarn includes a polyester material. The method for manufacturing a tire according to any one of claims 1 to 3, wherein the conductive yarn includes a metal material. The tire manufacturing method according to claim 4, wherein the conductive yarn contains 10% to 30% of the metal material by weight. The tire manufacturing method according to any one of claims 1 to 5, wherein the conductive yarn is a blended yarn of PET short fibers and SUS short fibers. The method for manufacturing a tire according to any one of claims 1 to 6, wherein the first step includes a step of pressing the conductive thread against the outer surface of the rubber material with the pressing surface of a roller having a heated pressing surface. The method for manufacturing a tire according to claim 7, wherein the temperature of the pressing surface is a temperature at which the rubber material does not vulcanize. The method for manufacturing a tire according to claim 8, wherein the temperature of the pressing surface is 80 to 120°C. The tire manufacturing method according to any one of claims 7 to 9, wherein the roller presses the conductive yarn with a pressure of 0.1 to 2.0 MPa. The tire manufacturing method according to any one of claims 7 to 10, wherein the pressing surface is provided with a plurality of ridges extending in a direction intersecting the roller circumferential direction. The tire manufacturing method according to claim 11, wherein the height of the ridge is 0.2 to 1.1 mm. The method for manufacturing a tire according to any one of claims 1 to 12, wherein the rubber material is a carcass ply. The tire manufacturing method according to any one of claims 1 to 13, wherein the rubber material is a carcass ply that has undergone an EBR process.

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