JP6988429B2 - Rigid core - Google Patents

Description

The present invention relates to a rigid core for vulcanizing and molding a tire.

In recent years, in order to improve the tire forming accuracy, a tire forming method using a rigid core has been proposed. This rigid core includes an annular core body having an outer shape that matches the shape of the lumen surface of the tire after vulcanization molding. The core body is composed of a plurality of core segments divided in the circumferential direction so that the core body can be disassembled and pulled out from the tire after vulcanization molding. Each of the plurality of core segments has a tire forming surface, and unvulcanized rubber members serving as tire constituent members are sequentially attached on the tire forming surface to form a raw tire. Then, the rigid core is put into the vulcanization die, and the tire is vulcanized between the rigid core which is the inner die and the vulcanization die which is the outer die.

In the tire forming method using such a rigid core, for example, the air remaining between the core body and the raw tire causes poor rubber flow on the lumen surface of the tire. , Deteriorate its appearance. Therefore, in Patent Document 1 below, it is proposed that the tire molding surface is provided with a plurality of air through holes opened at the tire molding surface so that the residual air is discharged to the outside of the rigid core. ..

JP-A-2015-214103

However, in such an air through hole, there is a problem that air cannot be sufficiently discharged and a defect in rubber flow cannot be suppressed.

The present invention has been devised in view of the above circumstances, and provides a rigid core capable of improving the appearance of the tire lumen surface based on improving the tire molded surface of the core segment. The main purpose is that.

The present invention is a rigid core for vulcanizing and molding a tire, and includes an annular core body composed of a plurality of core segments, and the core body projects most in the width direction of the core body. The plurality of core segments having a core maximum width position have a tire forming surface on which a raw tire is arranged and a predetermined drawing direction for pulling out from the tire, and the plurality of cores. The tire forming surface of at least one of the segments extends inward in the radial direction of the core body from the core maximum width position, substantially parallel to the pulling direction, and the tire forming surface and the raw tire. An inner vent line is provided for discharging the air between the tire and the tire to the outside of the rigid core.

It is desirable that the rigid core according to the present invention is provided with a plurality of inner vent lines separated from each other in the circumferential direction of the core body.

In the rigid core according to the present invention, it is desirable that each of the inner vent lines is arranged at intervals of 10 to 40 mm.

The rigid core according to the present invention preferably has a depth of 0.7 to 1.5 mm at the inner vent line.

In the rigid core according to the present invention, the tire forming surface is in the rigidity of the air between the tire forming surface and the raw tire on the radial side of the core body from the core maximum width position. It is desirable to provide an outer vent line for discharging to the outside of the child.

In the rigid core according to the present invention, it is desirable that the outer vent line communicates with the inner vent line.

The rigid core of the present invention is provided with an inner vent line extending substantially parallel to the pull-out direction on the tire forming surface of the core segment, inside the core body in the radial direction from the maximum width position of the core. Such an inner vent line can sufficiently discharge the air remaining between the core body and the raw tire. Further, the inner vent line forms, for example, a convex rubber piece extending substantially parallel to the pulling direction on the inner cavity surface of the tire after vulcanization molding. Since such a convex rubber piece reduces the shearing force received from the inner vent line when the core segment is pulled out from the tire, it is possible to suppress scratches on the lumen surface. Further, since the inner vent line can sufficiently discharge the air, defects due to rubber flow can be suppressed. Therefore, the rigid core of the present invention can improve the appearance of the lumen surface.

It is sectional drawing which shows the use state of one Example of the rigid core of this invention. It is a perspective view of a core body. It is a side view of a core body. It is an enlarged view of the core segment of FIG. It is a perspective view of a core segment. It is a perspective view of the core body of another embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a rigid core 1 showing an embodiment of the present invention. The rigid core 1 of the present embodiment is used, for example, for molding a pneumatic tire (hereinafter, may be simply referred to as a “tire”) T. As shown in FIG. 1, in the present embodiment, the rigid core 1 has an annular core body 2, a cylindrical core 3 inserted in the central hole 2H thereof, and both sides of the core 3 in the axial direction. It is configured to include a pair of side plates 4 and 4 arranged concentrically with each other.

The core body 2 has almost the same shape as the tire T by sequentially attaching components (not shown) for the tire T such as carcass ply, belt ply, sidewall rubber, and tread rubber on the outer surface thereof. Raw tire Ta is formed. The raw tire Ta is put into the vulcanization die B together with the rigid core 1, and is heated and pressed between the core body 2 which is the inner die and the vulcanization die B which is the outer die. It is vulcanized into T. The constituent member is formed of, for example, a ribbon-shaped rubber strip.

In the core body 2 of the present embodiment, for example, a hollow lumen portion N extending continuously in the circumferential direction of the core body 2 (hereinafter, may be simply referred to as “circumferential direction”) is formed inside the core body 2. ing. A heating means (not shown) such as an electric heater is arranged in the lumen portion N in order to heat the raw tire Ta from the inside.

FIG. 2 is a perspective view of the core body 2. FIG. 3 is a side view of the core body 2. As shown in FIGS. 2 and 3, the core body 2 is formed from a plurality of core segments 5 divided in the circumferential direction in the present embodiment.

The core segment 5 of the present embodiment includes end faces 8 on both sides separated in the circumferential direction, and a circumferential surface 9 extending between the end faces 8 and 8 in the circumferential direction.

The circumferential surface 9 of the present embodiment is the tire forming surface 11 on which the raw tire Ta is arranged and the radial direction of the core body 2 with respect to the tire forming surface 11 (hereinafter, may be simply referred to as “radial direction”). Includes a pair of inner side surfaces 12, 12 formed inside the tire. The inner side surface 12 is, for example, a portion where the raw tire Ta is not arranged and comes into contact with the vulcanization die B during vulcanization.

The tire forming surface 11 includes a tread forming surface 11a, a pair of sidewall forming surfaces 11b, and a pair of bead forming surfaces 11c. The tread molded surface 11a forms the lumen surface Tb of the tread portion T1 (shown in FIG. 1) of the tire T. The sidewall forming surface 11b is connected to both sides of the tread forming surface 11a and forms the lumen surface Tb of the sidewall portion T2 of the tire T. The sidewall molding surface 11b of the present embodiment is the tire molding surface 11 of the core body 2 and has the maximum width of the core most overhanging in the width direction of the core body 2 (hereinafter, may be simply referred to as “width direction”). Includes position 2c. The bead forming surface 11c is connected to the inside of the sidewall forming surface 11b in the radial direction and forms the lumen surface Tb of the bead portion T3 of the tire T. The width direction is a direction parallel to the core axis 2j of the core body 2.

In the present embodiment, the core segment 5 is composed of a first core segment 5A and a second core segment 5B. The first core segment 5A is formed so that the end faces 8A and 8A on both sides are inclined inward in the radial direction in a direction in which the circumferential width of the core segment 5 increases. The second core segment 5B is formed so that the end faces 8B and 8B on both sides are inclined inward in the radial direction so that the circumferential width of the core segment 5 becomes smaller. In the present embodiment, the first core segment 5A and the second core segment 5B are arranged alternately in the circumferential direction.

After vulcanization molding, the core body 2 first pulls out at least one first core segment 5A from the tire T inward in the radial direction, whereby the remaining first core segment 5A and each second core 2 are formed. The child segment 5B is pulled out and disassembled. The core 3 prevents each core segment 5 from moving inward in the radial direction, and integrally connects the core segments 5.

In the present embodiment, the core segment 5 has a predetermined drawing direction R for pulling out from the tire T. In the present embodiment, the drawing direction R is at least the circumferential width center surface Co which is the center of the circumferential width of the core segment 5 in the first core segment 5A which is first pulled out after vulcanization molding. It is oriented along. In the present embodiment, the circumferential width center surface Co overlaps with the side view of the core body 2 and the radiation passing through the core axis 2j of the core body 2. In the present embodiment, the extraction direction R of the remaining core segment 5 is also the direction along the circumferential width center surface Co overlapping with the radiation passing through the core axis 2j. The pull-out direction R is not limited to the above-described aspect.

FIG. 4 is an enlarged view of the core segment 5. As shown in FIG. 4, at least one core segment 5 has, for example, a tire forming surface 11 and a raw tire Ta on the tire forming surface 11 inside the core maximum width position 2c in the radial direction. An inner vent line 15 is provided which can discharge the air between them to the outside of the rigid core 1. The inner vent line 15 extends substantially parallel to the pull-out direction R. The inner vent line 15 forms, for example, a convex rubber piece (not shown) extending substantially parallel to the drawing direction R on the lumen surface (shown in FIG. 1) Tb of the tire T after vulcanization molding. .. Such a convex rubber piece substantially parallel to the pulling direction R is generated on the lumen surface Tb because the shearing force received from the inner vent line 15 becomes small when the core segment 5 is pulled out from the tire T. Can suppress scratches. Further, since the inner vent line 15 can sufficiently discharge the air, defects due to rubber flow can be suppressed. Therefore, the rigid core 1 of the present invention can improve the appearance of the lumen surface Tb. The "substantially parallel" means that the pull-out direction R and the inner vent line 15 are arranged in parallel, and of course, the angle θ between the pull-out direction R and the longitudinal direction of the inner vent line 15 is 10 degrees or less. This includes the case where the inner vent line 15 is arranged so as to be.

In the present embodiment, all the core segments 5 are provided with an inner vent line 15 extending substantially parallel to the drawing direction R. This further improves the appearance of the lumen surface Tb.

As shown in FIG. 1, the inner vent line 15 of the present embodiment is formed as a groove-like body recessed from the tire forming surface 11 toward the lumen portion N side. The inner vent line 15 may have a cross section formed in a polygonal shape such as a rectangular shape, or may be formed in a U shape or a V shape.

The inner vent line 15 extends continuously, for example, from the core maximum width position 2c of the sidewall forming surface 11b to the radial inner end of the bead forming surface 11c. Such an inner vent line 15 effectively exerts the above-mentioned action. The inner vent line 15 may extend from the core maximum width position 2c to the inner side surface 12, for example.

As shown in FIG. 4, a plurality of inner vent lines 15 are provided apart from each other in the circumferential direction in the present embodiment. As a result, the air between the tire forming surface 11 and the raw tire Ta is effectively discharged. In FIGS. 2 to 4 and 6, for convenience, the inner vent line 15 and the outer vent line 16 described later are shown by center lines, respectively.

It is desirable that each of the inner vent lines 15 is provided at intervals p of 10 to 40 mm. If the interval p is less than 10 mm, for example, the adhesiveness between the tire forming surface 11 and the rubber strip may decrease, and the raw tire Ta may not be formed accurately. If the distance p exceeds 40 mm, the air between the raw tire Ta and the tire forming surface 11 may not be effectively discharged.

FIG. 5 is a perspective view of the core segment 5. As shown in FIG. 5, in the present embodiment, the inner vent line 15 communicates with an air channel 17 formed of a groove-shaped body recessed toward the lumen N side. The air channel 17 is formed, for example, in the same opening width, depth, and shape as the inner vent line 15.

The air channel 17 of the present embodiment includes a first channel 17a arranged on the inner side surface 12 and a second channel 17b arranged on the end surface 8.

The radial outer end (not shown) of the first channel 17a of the present embodiment communicates with the radial inner end (not shown) of the inner vent line 15. The first channel 17a is formed of a plurality of lines communicating with each of the inner vent lines 15 extending to the inner end in the radial direction of the bead forming surface 11c.

The second channel 17b of the present embodiment includes an axial portion 18 extending axially from the end surface 8 and a radial portion 19 extending radially along the axial portion 18. The axial portion 18 communicates with, for example, an inner vent line 15a whose ends end at the end surface 8. In the present embodiment, a plurality of axial portions 18 are formed side by side in the radial direction. The radial portion 19 extends inward in the radial direction from, for example, the axial portion 18a located on the outermost side in the radial direction. The radial inner end of the radial portion 19 communicates with the radial inner edge 8e of the end face 8. In the present embodiment, a plurality of radial portions 19 are formed side by side in the axial direction.

In the present embodiment, the air channel 17 is provided in a bead ring (not shown) which is a constituent member of the vulcanization die B for forming the bead portion T3 of the tire T, and is opened outside the rigid core 1. It communicates with the exhaust passage. As a result, the air in the inner vent line 15 is discharged from the exhaust groove to the outside of the rigid core 1 via the air channel 17. The method of discharging the air in the inner vent line 15 is not limited to such an aspect. For example, the inner vent line 15 may be connected to a first channel 17a and a radial portion 19 formed on the outer surface of the core 3 and extending to the outside of the rigid core 1 (shown in FIG. 1). Further, for example, as is well known, the inner vent line 15 may be connected to a negative pressure source such as a vacuum (not shown) and connected to an exhaust passage (not shown) extending inside the core segment.

The inner vent line 15 preferably has a depth t of 0.7 to 1.5 mm. If the depth t of the inner vent line 15 is less than 0.7 mm, the air may not be effectively discharged. When the depth t of the inner vent line 15 exceeds 1.5 mm, the height of the rubber piece formed inside the inner vent line 15 (not shown) becomes large, and the core segment 5 after vulcanization molding is pulled out. At that time, the inner cavity surface Tb of the tire T may be scratched.

As shown in FIG. 4, the opening width w of the inner vent line 15 is preferably, for example, about 0.5 to 1.0 mm, although it is not particularly limited.

Further, in the present embodiment, the core segment 5 discharges the air between the tire forming surface 11 and the raw tire Ta to the outside of the rigid core 1 on the radial side of the core maximum width position 2c. The outer vent line 16 is provided. Since such an outer vent line 16 also suppresses poor rubber flow and the like, the appearance of the inner cavity surface Tb of the tire T can be improved.

The outer vent line 16 communicates with the inner vent line 15 in this embodiment. That is, in the outer vent line 16 of the present embodiment, the inner end 16i in the radial direction is located at the core maximum width position 2c. As a result, the air that has flowed into the outer vent line 16 is discharged to the outside of the rigid core 1 via the inner vent line 15. For example, the axial portion 18 of the air channel 17 may be connected to the outer vent line 16a terminated by the end surface 8.

In the present embodiment, the outer vent line 16 continuously extends from the tread forming surface 11a across the pair of sidewall forming surfaces 11b, 11b. Such an outer vent line 16 may expel air to more rigid cores 1. The outer vent line 16 may be interrupted at, for example, the tread forming surface 11a.

The outer vent line 16 is formed as a groove-like body recessed from the tire forming surface 11 toward the lumen portion N side, similarly to the inner vent line 15. Since the outer vent line 16 is formed in the same shape as the inner vent line 15 in the present embodiment, only a portion different from the inner vent line 15 will be described below.

In the present embodiment, the outer vent line 16 substantially extends in the radial direction passing through the core axis 2j of the core body 2. The rubber strips of the constituent members for the tire T arranged on the tire forming surface 11 extend, for example, along the circumferential direction. As a result, the outer vent line 16 is substantially perpendicular to the length of the rubber strip, so that the air can be discharged more effectively.

The shear force generated in the convex rubber piece (not shown) formed by the outer vent line 16 when pulled out from the tire T is higher than the shear force generated in the convex rubber piece (not shown) formed by the inner vent line 15. Is also small. Therefore, it is considered that the outer vent line 16 is less likely to cause scratches on the lumen surface Tb than the inner vent line 15. Therefore, unlike the inner vent line 15, the outer vent line 16 does not have to have a shape extending substantially parallel to the pull-out direction R.

FIG. 6 is a perspective view of the core body 2 of another embodiment. The same parts as the configuration of the core main body 2 of this embodiment and the configuration of the core main body 2 of the present embodiment are designated by the same reference numerals, and the description thereof will be omitted. As shown in FIG. 6, the outer vent line 16 of this embodiment is configured to include a first portion 16A extending in the radial direction passing through the core axis 2j and a second portion 16B extending in the circumferential direction. There is. Such an outer vent line 16 can more effectively expel the residual air.

The first portion 16A and the second portion 16B are provided so as to intersect each other in the present embodiment. In the present embodiment, a plurality of the first portion 16A and the second portion 16B are provided in each of the core segments 5. The first portion 16A and the second portion 16B are provided on the tread forming surface 11a and the sidewall forming surface 11b, respectively, in the present embodiment. The second portion 16B may be provided only on the tread forming surface 11a, for example. Further, the second portion 16B may be formed so as to extend spirally on the tread forming surface 11a, for example.

The first portion 16A may be inclined with respect to the radial direction passing through the core axis 2j, for example. The first portion 16A preferably communicates with the inner vent line 15. The second portion 16B may be continuously extended in the circumferential direction, or may be formed intermittently in the circumferential direction, for example. Further, the second portion 16B may be inclined with respect to the circumferential direction.

It is desirable that the pitch p2 of the second portion 16B is larger than the pitch p1 of the first portion 16A, for example. The rubber strip arranged on the outer surface of the core body 2 is usually attached along the circumferential direction. Therefore, it is difficult for the second portion 16B to discharge the residual air as compared with the first portion 16A. From this point of view, when the pitch p2 of the second portion 16B is small, the demerit that it becomes difficult to attach the rubber strip to the tire forming surface 11 is greater than the merit of discharging the residual air. Therefore, the pitch p2 of the second portion 16B is preferably, for example, 15 to 45 mm. The second portion 16B having a small angle with respect to the circumferential direction can easily maintain the stickability of the rubber strip to the tire forming surface 11 as compared with the second portion 16B having a large angle with respect to the circumferential direction. Can be made smaller.

Although the particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment and can be modified into various embodiments.

In order to confirm the effect of the present invention, a rigid core having the basic structure of FIG. 1 was prototyped based on the specifications of Table 1. Then, when a pneumatic tire was formed using this rigid core, the stickability of the rubber strip, the appearance due to the rubber flow, and the appearance due to scratches were tested. The common specifications and test methods are as follows.
Tire size: 225 / 45RF18
Inner vent line, outer vent line width: 0.7mm
Outer vent line depth and pitch: Same as inner vent line depth and pitch 2nd part (outer vent line) pitch p2: 15.0mm
Pitch and depth of the outer vent line of Comparative Example 3: 10 mm, 1.0 mm

<Attachability of rubber strip>
It was confirmed whether or not the rubber strip, which is a component of the tire, fell off from the tire molded surface when the rubber strip, which is a component of the tire, was attached to the tire molded surface. The result is the percentage of tires with rubber strips dropped out of 100 test tires. The smaller the value, the better the rubber strip does not fall off.

<Appearance due to rubber flow>
After vulcanization molding, the appearance was confirmed due to poor rubber flow on the inner surface of the tire. The result is a percentage of the number of tires determined to be defective with respect to 100 test tires. The smaller the value, the better the rubber flow is not defective.

<Appearance due to scratches>
After vulcanization molding, the appearance due to scratches on the inner surface of the tire was confirmed. The result is a percentage of the number of tires determined to be defective due to scratches with respect to 100 test tires. The smaller the value, the better there is no scratch.

As shown in Table 1, the rigid core of the embodiment has a high appearance because air is effectively discharged and the generation of scratches is suppressed. Further, the rigid core of the embodiment can be attached to the tire molded surface without the rubber strip falling off. Tests with different tire sizes and rubber strip materials gave similar results.

1 Rigid core 2 Core body 2c Core maximum width position 5 Core segment 11 Tire molding surface 15 Inner vent line R Pull-out direction T Tire Ta Raw tire

Claims (6)

It is a rigid core for vulcanizing and molding tires.
Includes an annular core body consisting of multiple core segments
The core body has a core maximum width position most overhanging in the width direction of the core body.
The plurality of core segments have a tire forming surface on which a raw tire is arranged and a predetermined drawing direction for pulling out from the tire.
The tire forming surface of at least one of the plurality of core segments extends inward in the radial direction of the core body from the maximum width position of the core, substantially parallel to the pulling direction, and the tire forming. inner vent line provided et been for discharging air between the face and the raw tire to the outside of the rigid core,
The tire forming surface is outside the core body in the radial direction from the maximum width position of the core, and the outside for discharging air between the tire forming surface and the raw tire to the outside of the rigid core. Bent line is provided,
The outer vent line extends in the radial direction through the core axis of the core body.
Rigid core. The rigid core according to claim 1, wherein a plurality of inner vent lines are provided apart from each other in the circumferential direction of the core body. The rigid core according to claim 2, wherein each of the inner vent lines is arranged at intervals of 10 to 40 mm. The rigid core according to any one of claims 1 to 3, wherein the inner vent line has a depth of 0.7 to 1.5 mm. The rigid core according to any one of claims 1 to 4 , wherein the inner vent line is a groove-shaped body. The rigid core according to any one of claims 1 to 5, wherein the outer vent line communicates with the inner vent line.

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