JP2019151045A - Method for manufacturing tire - Google Patents

Abstract

To suppress rubber shrinkage when a belt-like strip is directly wound on an outer surface of a rigid core.SOLUTION: In a green tire formation step S, a green tire 1 is formed by sequentially pasting a rubber material on an outer surface 10s of a rigid core 10. The rubber material contains a belt-like strip 2 having exhaust grooves 3. The green tire formation step S includes a winding step S1 for directly winding the belt-like strip 2 on the outer surface 10s of the rigid core 10 in an elevated temperature state Y. The elevated temperature state Y is a state in which the outer surface 10s is elevated to a temperature of 40°C or more.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a green tire forming process using a rigid core, and more particularly, to a tire manufacturing method capable of suppressing cracking due to rubber contraction of a strip-shaped strip.

  In the core method of forming a green tire by sequentially affixing unvulcanized rubber material to the outer surface of a rigid core, a so-called strip wind method using a strip-like strip as a rubber material is widely used ( For example, see Patent Document 1).

  In this strip winding method, a rubber member having a predetermined cross-sectional shape is formed by spirally winding a strip-like strip. At this time, in order to adhere the winding portions to each other, it is necessary to wind up a high-temperature strip-like strip immediately after extrusion. However, when the strip is directly wound around the outer surface of the rigid core, the strip is cooled by the rigid core and rubber contraction (shrink) occurs.

  In particular, in the strip wind method, it is desirable to form an exhaust groove on the surface of the strip strip in order to prevent air remaining between winding portions of the strip strip and other members adjacent to the strip strip. (See, for example, Patent Document 2). However, when rubber contraction occurs in such strip strips with exhaust grooves, there is a problem that cracks occur at the positions of the exhaust grooves, resulting in poor formation of raw tires.

Japanese Patent Laying-Open No. 2006-40102 JP 2006-51711 A)

  An object of the present invention is to provide a tire manufacturing method capable of suppressing cracking due to rubber shrinkage when a strip-shaped strip with an exhaust groove is directly wound around a rigid core.

The present invention is a tire manufacturing method including a raw tire forming step of forming a raw tire by sequentially pasting unvulcanized rubber material on the outer surface of a rigid core,
The rubber material includes a strip having an exhaust groove on the surface extending in a direction crossing the length direction,
The raw tire forming step includes a winding step in which the strip is directly wound around the outer surface of the rigid core in a heated state in which the outer surface is heated to a temperature of 40 ° C. or higher.

  In the tire manufacturing method according to the present invention, the temperature of the outer surface of the rigid core in the temperature-rise state is preferably in the range of 40 to 50 ° C.

  In the tire manufacturing method according to the present invention, the exhaust groove preferably has a width of 0.5 to 1.0 mm and a depth of 1 to 30% of the thickness of the strip.

  In the tire manufacturing method according to the present invention, it is preferable that the outer surface is heated by an electric heater provided in the rigid core.

  As described above, the present invention includes a winding step in which a strip is directly wound around the outer surface of a rigid core that has been heated to 40 ° C. or higher. This reduces the temperature difference between the strip and the rigid core. As a result, it is possible to suppress the rubber shrinkage of the strip strip after being attached while maintaining the adhesiveness of the strip strip high, and to suppress cracking at the position of the exhaust groove.

It is sectional drawing of the green tire formed by the green tire formation process in the tire manufacturing method of this invention. It is a perspective view which shows the winding process in a green tire formation process. FIG. It is a perspective view of a strip-shaped strip.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the tire manufacturing method of the present invention includes a green tire forming step S for forming a green tire 1 on a rigid core 10. After the green tire forming step S, the green tire 1 is put into the vulcanization mold together with the rigid core 10 and vulcanized (vulcanization step).

  In this example, the green tire 1 formed in the green tire forming step S includes an inner liner rubber G1, a carcass ply G2, a chafer rubber G3, a bead core G4, a bead apex rubber G5, a belt ply G6, a side wall rubber G7, and a tread rubber G8. It is comprised by the well-known tire structural member containing.

  These tire constituent members G1 to G8 are formed of an unvulcanized rubber material.

  The rubber material is rubber-coated with various rubber materials such as an inner liner rubber G1, chafer rubber G3, bead apex rubber G5, sidewall rubber G7, tread rubber G8, and the like, and an array of carcass cords. Various rubber materials such as carcass ply materials, bead core materials coated with a bead cord with rubber, and belt ply materials with a belt cord array coated with rubber are also included.

  In the raw tire forming step S, the raw tire 1 is formed by sequentially sticking the rubber materials to the outer surface 10 s of the rigid core 10.

  As shown in FIG. 2, the rigid core 10 has a well-known structure, and in this example, the core body 11 having the outer surface 10s and a cylindrical shape inserted into the center hole 11H of the core body 11 are used. A core 12 and a pair of side wall bodies 13 arranged on both sides in the axial direction of the core body 11 are provided. The outer surface 10s has a shape that approximates the inner cavity surface of the finished tire after vulcanization. The core body 11 can be disassembled and is formed of a plurality of core segments 11a divided in the tire circumferential direction. The core 12 prevents each core segment 11a from moving inward in the radial direction. Further, the side wall bodies 13 prevent the core segments 11a from moving in the axial direction. A support shaft portion 14 projects from the axially outer side surface of each side wall 13. The support shaft portion 14 functions as a gripping portion or a mounting portion for mounting the rigid core 10 on a raw tire forming device or a vulcanizing device.

  The raw tire forming step S includes a winding step S1 in which the strip 2 is directly wound on the outer surface 10s of the rigid core 10 as shown in FIG. By this winding step S1, in this example, the inner liner rubber G1 is directly formed on the outer surface 10s. In addition, the strip | belt-shaped strip 2 is supplied to the rigid core 10 in the state of the high temperature (for example, about 50-60 degreeC) extruded from the rubber extruder.

  In this example, the strip-shaped strip 2 is a rubber material for forming an inner liner rubber, and has an exhaust groove 3 extending in a direction crossing the length direction on at least one surface as shown in FIG. The thickness t and width W of the strip 2 are dependent on the tire component to be formed, but when forming the inner liner rubber G1, the thickness t is 0.9 to 1.1 mm and the width W is 17 to 19 mm. Is preferred.

  Further, the exhaust groove 3 preferably has a width Wg of 0.5 to 1.0 mm and a depth Hg of 10 to 30% of the thickness t of the strip 2. When the width Wg is less than 0.5 mm and the depth Hg is less than 10% of the thickness t, the exhaust effect is insufficient and it is difficult to sufficiently prevent the remaining air. On the other hand, when the width Wg exceeds 1.0 mm and the depth Hg exceeds 30% of the thickness t, the strength becomes insufficient and breakage damage may occur during conveyance. Also in the present invention, it is difficult to sufficiently suppress cracking due to rubber shrinkage.

  As the exhaust groove 3, one extending from one side edge of the strip 2 to the other side is preferable, but one having one end terminating in the strip 2 and one terminating both ends within the strip 2 are also employed. Yes. From the viewpoint of exhaust effect and strength, the exhaust groove 3 is preferably inclined at an angle θ of 20 to 60 ° with respect to the length direction of the strip 2.

  In the winding step S1, the strip 2 is directly wound around the outer surface 10s of the rigid core 10 in the temperature rising state Y. “Temperature rise state Y” means a state in which the outer surface 10s of the rigid core 10 is heated to a temperature T0 of 40 ° C. or higher.

  As shown in FIG. 3, the temperature rise state Y is raised by the electric heater 5 provided in the rigid core 10 in this example. Specifically, it is disposed on the inner cavity surface 15 of the core body 11. In this example, the electric heater 5 includes a tread heater 5A and side heaters 5B and 5B, and uniformly raises the temperature of the outer surface 10s. Various types of heaters using resistance heating elements can be used as the electric heater 5. In particular, a so-called planar heater having a sheet shape has a large contact area with the core body 11 and uniformly heats a wide area without unevenness. Preferred above.

  In this manner, by winding the strip 2 around the outer surface 10s of the rigid core 10 in the temperature rising state Y, the temperature difference between the strip 2 and the outer surface 10s is reduced. As a result, it is possible to suppress rubber contraction of the strip-shaped strip 2 after pasting, and to suppress rubber cracking in the exhaust groove 3.

  When the temperature T0 is lower than 40 ° C., it is difficult to sufficiently suppress the rubber shrinkage of the strip 2 after being attached. If the temperature T0 is too high, there is a problem that the operator cannot immediately cope with the high temperature because of the high temperature. Therefore, the upper limit of the temperature T0 is preferably 60 ° C. or lower, and more preferably 50 ° C. or lower.

  The temperature T0 can be detected by a temperature sensor 16 such as a mold surface temperature sensor embedded in the core body 11 and in the vicinity of the outer surface 10s, and the temperature T0 is known based on measurement data from the temperature sensor 16. It is controlled by the temperature controller 17.

  It is preferable that the temperature rising state Y is maintained not only during the winding step S1 but also during the raw tire forming step S.

  In the present invention, since the rubber contraction of the strip 2 can be suppressed, the width Wg and the depth Hg of the exhaust groove 3 can be relatively increased while suppressing cracking. As a result, the exhaust effect is further enhanced, and it can be expected to reduce the appearance defect due to the remaining air and the decrease in the formation accuracy of the raw tire.

  In the core method, in consideration of thermal expansion in the vulcanization process, the rigid core 10 is formed so that a gap is generated between the core segments 11a and 11a in a normal temperature state. However, when the rigid core 10 with a green tire formed at room temperature is put into the vulcanization process, a so-called rubber bite in which rubber enters the gap during vulcanization tends to occur. However, when the temperature rise state Y is maintained even during the raw tire formation step S, the gap is reduced in advance by the temperature rise, so that the rubber biting during vulcanization can be suppressed. Moreover, shortening of the process time of a vulcanization process can also be expected.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  A raw tire (tire size 245 / 45RF18) having the internal structure shown in FIG. 1 was prototyped according to the specifications shown in Table 1 based on the raw tire forming step in the production method of the present invention. Then, when forming the inner liner rubber in the winding process, the occurrence of cracks due to the exhaust grooves of the strip-like strip and the occurrence of remaining air were confirmed. Except for the description in Table 1, the specifications are substantially the same, and only the temperature T0 of the outer surface of the rigid core and the size of the exhaust groove formed in the strip are different.

  The strip has a thickness t = 1.0 mm and a width W = 18.5 mm, and the temperature when the strip is affixed to the rigid core is 60 ° C.

(1) Occurrence of cracks and remaining air:
When forming 200 present a green tire, in the winding step (formation of the inner liner rubber), and compared incidence of cracking caused by exhaust groove of the strip-like strips, and the air remaining occurrence. A smaller numerical value is preferable.

  As shown in the table, it can be confirmed that the embodiment can suppress the cracks caused by the exhaust grooves of the strip-shaped strip.

DESCRIPTION OF SYMBOLS 1 Raw tire 2 Strip | belt-shaped strip 3 Exhaust groove 5 Electric heater 10 Rigid core 10s Outer surface S Raw tire formation process S1 Winding process Y Temperature rising state

Claims (4)

A tire manufacturing method including a green tire forming step of forming a green tire by sequentially pasting an unvulcanized rubber material on the outer surface of a rigid core,
The rubber material includes a strip having an exhaust groove on the surface extending in a direction crossing the length direction,
In addition, the green tire forming step includes a winding step in which the strip is directly wound around the outer surface of the rigid core in a heated state in which the outer surface is heated to a temperature of 40 ° C. or higher. .   The tire manufacturing method according to claim 1, wherein the temperature of the outer surface of the rigid core in the temperature rise state is in a range of 40 to 50 ° C. 2.   The tire manufacturing method according to claim 1 or 2, wherein the exhaust groove has a width of 0.5 to 1.0 mm and a depth of 1 to 30% of the thickness of the strip.   The tire manufacturing method according to claim 1, wherein the outer surface is heated by an electric heater provided in the rigid core.

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