JP2019104208A - Rigid core - Google Patents

Abstract

To provide a rigid core for improving appearance of inner surface of a tire, for obtaining a better tire molding surface of a rigid core segment for enhancing molding precision of the tire.SOLUTION: The rigid core for vulcanization molding of a tire contains a circular core main body composed of a plurality of core segment 5. In the rigid core, the core main body contains a core maximum width position 2c extending mostly in the width direction of the core main body, and the core segment 5 has a tire molding surface 11 where a green tire is arranged and has a predetermined pull-out direction R for pulling out from a tire; the tire molding surface 11 is provided, on the inside of the radial direction of the core main body than the core maximum width position 2c, with an inside vent line 15 which extends substantially parallel to the pull-out direction R for discharging an air between the tire molding surface 11 and the green tire to the outside.SELECTED DRAWING: Figure 4

Description

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

  In recent years, in order to improve the formation accuracy of a tire, a tire formation method using a rigid core has been proposed. The rigid core includes an annular core body having an outer shape that matches the shape of the inner surface of the tire after vulcanization molding. The core body is constituted by a plurality of core segments which are circumferentially divided so that they can be disassembled and pulled out of the tire after vulcanization molding. Each of the plurality of core segments has a tire molding surface, and unvulcanized rubber members, which are components of the tire, are sequentially attached on the tire molding surface to form a green tire. Then, the whole rigid core is put into a vulcanizing mold, and a tire is vulcanized and formed between the rigid core which is an inner mold and the vulcanizing mold which is an outer mold.

  In a tire forming method using such a rigid core, for example, air remaining between the core body and the green tire causes a defect in rubber flow on the inner surface of the tire, and the like. , Worsen its appearance. Therefore, Patent Document 1 below proposes that the tire molding surface be provided with a plurality of air through holes opened at the tire molding surface, and the remaining air be discharged to the outside of the rigid core. .

JP, 2015-214103, A

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

  The present invention has been made in view of the above situation, and provides a rigid core capable of improving the appearance of the inner surface of the tire on the basis of improving the tire forming surface of the core segment. The main purpose is

  The present invention is a rigid core for vulcanizing and forming a tire, and includes an annular core main body consisting of a plurality of core segments, and the core main body projects most in the width direction of the core main body A plurality of core segments each having a core maximum width position, the plurality of core segments having a tire molding surface on which a green tire is disposed, and a predetermined drawing direction for drawing from the tire, At least one of the tire molding surfaces of the segments extends substantially inward of the core body in the radial direction with respect to the core maximum width position substantially parallel to the drawing direction, and the tire molding surface and the green tire And an inner vent line for discharging air between the two to the outside of the rigid core.

  In the rigid core according to the present invention, it is preferable that a plurality of the inner vent lines be provided in the circumferential direction of the core main body so as to be separated.

  In the rigid core according to the present invention, it is desirable that each of the inner vent lines be disposed at an interval of 10 to 40 mm.

  In the rigid core according to the present invention, the depth of the inner vent line is preferably 0.7 to 1.5 mm.

  In the rigid core according to the present invention, the tire molding surface is positioned between the tire molding surface and the green tire in the middle of the rigidity between the tire molding surface and the green tire on the radially outer side of the core main body than the core maximum width position. It is desirable to provide an outer vent line for venting the child out.

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

  In the rigid core of the present invention, the tire molding surface of the core segment is provided with an inner vent line extending radially inward of the core body than the core maximum width position and substantially in parallel with the drawing direction. Such an inner vent line can sufficiently discharge the air remaining between the core body and the green tire. In addition, the inner vent line forms, for example, a convex rubber piece extending substantially in parallel with the drawing direction on the inner surface of the tire after vulcanization molding. Such a convex rubber piece reduces the shear force received from the inner vent line when the core segment is pulled out of the tire, and therefore can prevent scratches on the inner surface. In addition, since the inner vent line can sufficiently discharge the air, defects due to the 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 condition 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 other embodiments.

Hereinafter, an embodiment of the present invention will be described based on 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, to form a pneumatic tire (hereinafter sometimes 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 into the central hole 2 H, and both sides of the core 3 in the axial direction. And a pair of side plates 4 and 4 arranged concentrically with each other.

  The core body 2 has substantially the same shape as the tire T by sequentially pasting components (not shown) for the tire T such as carcass ply, belt ply, sidewall rubber, tread rubber, etc. on the outer surface thereof A raw tire Ta is formed. The green tire Ta is placed in the vulcanizing mold B together with the rigid core 1 and heated and pressurized between the inner core body 2 and the outer mold. It is vulcanized to T. The component member is formed of, for example, a ribbon-like rubber strip.

  In the core body 2 of the present embodiment, for example, a hollow lumen N continuously extending in the circumferential direction of the core body 2 (hereinafter sometimes simply referred to as "circumferential direction") is formed. ing. In the bore N, heating means (not shown) such as an electric heater is arranged to heat the green 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, in the present embodiment, the core body 2 is formed of a plurality of core segments 5 divided in the circumferential direction.

  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 joint circumferential direction.

  The circumferential direction surface 9 of the present embodiment is a radial direction of the core body 2 with respect to the tire molding surface 11 on which the green tire Ta is disposed and the tire molding surface 11 (hereinafter sometimes referred to simply as "radial direction"). And a pair of inner surfaces 12, 12 formed on the inside of the housing. The inner side surface 12 is, for example, a portion where the green tire Ta is not disposed and which contacts the vulcanizing mold B at the time of vulcanization.

  The tire molding surface 11 includes a tread molding surface 11a, a pair of sidewall molding surfaces 11b, and a pair of bead molding surfaces 11c. The tread molding surface 11 a forms a bore surface Tb of the tread portion T1 (shown in FIG. 1) of the tire T. The sidewall molding surface 11b is continuous with both sides of the tread molding surface 11a, and forms a lumen surface Tb of the sidewall portion T2 of the tire T. The sidewall molding surface 11b of the present embodiment is the maximum width of the core in the width direction of the core body 2 (hereinafter may be simply referred to as "width direction") on the tire molding surface 11 of the core body 2 Includes position 2c. The bead molding surface 11c is continuous with the radially inner side of the sidewall molding surface 11b, and forms a lumen surface Tb of the bead portion T3 of the tire T. The width direction is a direction parallel to the core axial center 2 j of the core body 2.

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

  The core body 2 is at least one first core segment 5A extracted from the tire T radially inward after vulcanization molding, whereby the remaining first core segments 5A and the respective second middle segments are formed. The child segment 5B is pulled out and disassembled. The cores 3 prevent the core segments 5 from moving inward in the radial direction, and connect the core segments 5 integrally.

  The core segment 5 has a predetermined drawing direction R for drawing from the tire T in the present embodiment. In this embodiment, the drawing direction R is at least in the circumferential width center plane Co which is the center of the circumferential width of the core segment 5 in at least the first core segment 5A drawn out after vulcanization molding. It is the direction along. The circumferential width center plane Co overlaps with the radiation passing through the core axial center 2j of the core body 2 in a side view of the core body 2 in the present embodiment. In the present embodiment, the extraction direction R of the remaining core segments 5 is also the direction along the circumferential width center plane Co overlapping with the radiation passing through the core axial center 2j. In addition, extraction direction R is not limited to the above-mentioned aspect.

  FIG. 4 is an enlarged view of the core segment 5. As shown in FIG. 4, at least one core segment 5 is formed, for example, on the tire molding surface 11 at a position radially inward of the core maximum width position 2 c between the tire molding surface 11 and the green tire Ta. 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 withdrawal direction R. The inner vent line 15 forms, for example, a convex rubber piece (not shown) extending substantially in parallel with the drawing direction R on the inner surface (shown in FIG. 1) Tb of the tire T after vulcanization molding. . Such convex rubber pieces substantially parallel to the drawing direction R are generated on the inner surface Tb because the shear force received from the inner vent line 15 is reduced when the core segment 5 is drawn from the tire T. It can control the wound. In addition, since the inner vent line 15 can sufficiently discharge the air, defects due to the rubber flow can be suppressed. Therefore, the rigid core 1 of the present invention can improve the appearance of the inner surface Tb. The term "substantially parallel" means, of course, that when the drawing direction R and the inner vent line 15 are arranged in parallel, the angle θ between the drawing direction R and the longitudinal direction of the inner vent line 15 is 10 degrees or less To include the case where the inner vent line 15 is disposed.

  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 grooved body recessed from the tire molding surface 11 to the lumen N side. The inner vent line 15 may be formed, for example, in a U-shape or a V-shape in addition to the cross-section being formed in a polygonal shape such as a rectangular shape.

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

  As shown in FIG. 4, in the present embodiment, a plurality of inner vent lines 15 are provided circumferentially spaced apart. Thereby, the air between the tire molding surface 11 and the green tire Ta is effectively discharged. In FIG. 2 to FIG. 4 and FIG. 6, the inner vent line 15 and the outer vent line 16 described later are respectively shown by center lines for convenience.

  Each of the inner vent lines 15 is preferably provided at a spacing p of 10 to 40 mm. If the distance p is less than 10 mm, for example, the adhesion between the tire molding surface 11 and the rubber strip may be reduced, and the green tire Ta may not be formed with high accuracy. If the distance p exceeds 40 mm, air between the green tire Ta and the tire molding surface 11 may not be effectively discharged.

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

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

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

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

  In the present embodiment, the air channel 17 is provided in a bead ring (not shown) which is a component of the vulcanizing mold B for forming the bead portion T3 of the tire T and opens at the outside of the rigid core 1 It communicates with the exhaust channel. Thus, the air in the inner vent line 15 is exhausted from the exhaust groove to the outside of the rigid core 1 through the air channel 17. In addition, the exhaust method of the air in the inside vent line 15 is not limited to such an aspect. For example, the inner vent line 15 may be connected to the first channel 17a and the 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). Also, the inner vent line 15 may be connected to a negative pressure source such as a vacuum (not shown) and connected to an exhaust line (not shown) extending inside the core segment as well known, for example.

  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 discharged effectively. When the depth t of the inner vent line 15 exceeds 1.5 mm, the height (not shown) of the rubber pieces formed inside the inner vent line 15 becomes large, and the core segment 5 is pulled out after vulcanization molding. Sometimes, the bore surface Tb of the tire T may be damaged.

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

  Further, in the present embodiment, the core segment 5 discharges the air between the tire molding surface 11 and the green tire Ta to the outside of the rigid core 1 radially outward of the core maximum width position 2c. An outer vent line 16 is provided. Such an outer vent line 16 also suppresses the defect of the rubber flow and the like, so that the appearance of the inner 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 this embodiment, the radially inner end 16i is located at the core maximum width position 2c. Thus, the air flowing into the outer vent line 16 is discharged to the outside of the rigid core 1 through the inner vent line 15. Note that, for example, the axial direction portion 18 of the air channel 17 may be connected to the outer vent line 16 a that terminates at the end face 8.

  In the present embodiment, the outer vent line 16 extends continuously from the tread molding surface 11a across the pair of sidewall molding surfaces 11b and 11b. Such an outer vent line 16 may exhaust air to more rigid core 1. In addition, the outer side vent line 16 may be disconnected by the tread molding surface 11a, for example.

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

  The outer vent line 16 extends substantially in the radial direction passing through the core axial center 2j of the core body 2 in the present embodiment. The rubber strip of the component for the tire T disposed on the tire molding surface 11 extends, for example, along the circumferential direction. Thereby, the outer vent line 16 is in a direction 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 pulling out from the tire T is based on the shear force generated in the convex rubber piece (not shown) formed by the inner vent line 15 Too small. For this reason, the outer vent line 16 is considered to be less likely to cause a flaw on the inner surface Tb than the inner vent line 15. Therefore, unlike the inner vent line 15, the outer vent line 16 may not have a shape extending substantially in parallel with the drawing direction R.

  FIG. 6 is a perspective view of the core body 2 of another embodiment. The same portions as the configuration of the core body 2 of this embodiment and the configuration of the core body 2 of this embodiment are denoted by the same reference numerals, and the description thereof is omitted. As shown in FIG. 6, the outer vent line 16 of this embodiment comprises a first portion 16A extending radially through the core axis 2j and a second portion 16B extending circumferentially. There is. Such an outer vent line 16 can also effectively expel residual air.

  The first portion 16A and the second portion 16B are provided to cross each other in the present embodiment. In the present embodiment, a plurality of first portions 16A and second portions 16B are provided in each of the core segments 5. In the present embodiment, the first portion 16A and the second portion 16B are respectively provided on the tread molding surface 11a and the sidewall molding surface 11b. The second portion 16B may be provided only on the tread molding surface 11a, for example. In addition, the second portion 16B may be formed to extend, for example, the tread molding surface 11a in a spiral shape.

  The first portion 16A may be inclined, for example, with respect to the radial direction passing through the core axial center 2j. The first portion 16A desirably communicates with the inner vent line 15. For example, the second portion 16B may extend continuously in the circumferential direction or may be discontinuously formed in the circumferential direction. Furthermore, the second portion 16B may be inclined with respect to the circumferential direction.

  The pitch p2 of the second portion 16B is desirably, for example, larger than the pitch p1 of the first portion 16A. The rubber strip disposed on the outer surface of the core body 2 is generally affixed along the circumferential direction. For this reason, the second portion 16B is less likely to discharge the remaining air than the first portion 16A. From such a point of view, when the pitch p2 of the second portion 16B is small, the disadvantage that the rubber strip is difficult to stick to the tire molding surface 11 becomes larger than the merit of discharging the remaining 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 is easier to maintain the adhesion of the rubber strip to the tire molding surface 11 than the second portion 16B having a large angle with respect to the circumferential direction. It can be made smaller.

  As mentioned above, although the especially preferable embodiment of this invention was explained in full detail, this invention can be deform | transformed into a various aspect, and can be implemented, without being limited to embodiment of illustration.

In order to confirm the effect of the present invention, a rigid core having the basic structure of FIG. And when the 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 the scratch were tested. Common specifications and test methods are as follows.
Tire size: 225 / 45RF18
Inner vent line, outer vent line width: 0.7 mm
Outer vent line depth and pitch: same as inner vent line depth and pitch second part (outer vent line) pitch p2: 15.0 mm
The pitch of the outer vent line of Comparative Example 3, depth: 10 mm, 1.0 mm

<Applicability of rubber strip>
When the rubber strip which is a component of the tire was attached to the tire molding surface, the presence or absence of detachment from the tire molding surface was confirmed. The result is the percentage of tires that the rubber strip fell off with respect to 100 test tires. The smaller the value is, the better the rubber strip does not come off.

<Appearance by rubber flow>
After the vulcanization molding, the appearance due to the defect of the rubber flow on the inner surface of the tire was confirmed. The result is a percentage of the number of tires determined to be defective with respect to 100 test tires. The smaller the value is, the better the rubber flow is good.

<Appearance by 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 number, the better the scratch-free condition.

  As shown in Table 1, the rigid core of the example has high appearance because air is effectively exhausted and the occurrence of flaws is suppressed. In addition, the rigid core of the embodiment can be attached to the tire molding surface without the rubber strip falling off. Tests using different tire sizes and rubber strip materials resulted in similar results.

1 Rigid core 2 Core main body 2c Core maximum width position 5 Core segment 11 Tire molding surface 15 Inner vent line R Drawing direction T Tire Ta green tire

Claims (6)

A rigid core for vulcanizing and forming the tire,
Including an annular core body consisting of a plurality of core segments,
The core body has a core maximum width position that extends most in the width direction of the core body,
The plurality of core segments have a tire molding surface on which a green tire is disposed, and a predetermined drawing direction for drawing from the tire,
At least one of the tire molding surfaces of the plurality of core segments extends radially inward of the core body from the core maximum width position substantially in parallel with the drawing direction, and the tire molding An inner vent line is provided for discharging air between the surface and the green tire to the outside of the rigid core,
Rigid core.   The rigid core according to claim 1, wherein a plurality of the inner vent lines are provided spaced apart in the circumferential direction of the core body.   The rigid core according to claim 2, wherein each of the inner vent lines is spaced by 10 to 40 mm.   The rigid core according to any one of claims 1 to 3, wherein the depth of the inner vent line is 0.7 to 1.5 mm.   The tire molding surface is an outer side for discharging air between the tire molding surface and the green tire to the outside of the rigid core on the radially outer side of the core body than the maximum core width position. A rigid core according to any of the preceding claims, wherein a vent line is provided.   The rigid core of claim 5, wherein the outer vent line is in communication with the inner vent line.

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