JPH11300746A - Mold for molding tire and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate assembly even when the number of slits is increased and to prevent troubles in vulcanization caused by the slits. SOLUTION: In a tire molding mold, a tread molding mold part is constituted from sectors 1 divided in the circumferential direction, and the tread pattern molding part 1A of each sector 1 is constituted from blocks 1B partitioned every pitch or pitches of a tread pattern. Narrow slits 4 through which only air can pass are formed in the circumferential direction in the tread molding surface 1X of the block 1B. The slit 4 is made to communicate with the outside of the mold through an air outlet 7 formed on its back side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire molding die and a method of manufacturing the same, and more particularly, to a tire molding die which prevents vulcanization failure caused by an air vent slit and a tire molding die. It relates to a manufacturing method.

[0002]

2. Description of the Related Art In general, a vent hole is formed in a tread molding surface of a mold for molding a tire so that air sealed in the mold is released to the outside through the vent hole during vulcanization of the tire. . However, since unvulcanized rubber also flows out from the vent hole, a beard-like spew is generated on the tread surface of the tire after vulcanization. Therefore, a step of trimming the spew is required in the finishing step, which causes a great decrease in productivity, and there is a problem that the rubber that has flowed out is wasted.

Therefore, as a countermeasure, there has been proposed a technique of providing a narrow slit in the tread molding surface instead of the vent hole so as to allow only the air to pass without allowing the rubber to pass (for example, Japanese Unexamined Patent Publication No. 2-295706 and JP-A-4-223108). The tread pattern forming section of each sector is configured by stacking and connecting a plurality of segments, and a slit extending in the circumferential direction is formed between the stacked segments, or the tread pattern forming section of each sector is partitioned. A plurality of blocks are formed, and a slit extending in the radial direction is formed between the blocks.

However, since the width of the slit that allows only air to pass through without passing through the rubber is extremely narrow, the slit width often deviates from the range due to an error in assembling the segment or block. is there. As a result, there has been a problem that the slit width becomes too wide and the rubber enters into the slit to cause clogging or becomes too narrow, thereby causing air pockets and vulcanization failure.

[0005] Further, when an attempt is made to increase the number of slits, segments and blocks are subdivided in accordance with this, and there has been a problem that assembly is complicated.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a tire molding die which is easy to assemble even when the number of slits is increased and which does not cause vulcanization failure due to the slits, and a method of manufacturing the same. It is to provide a method.

[0007]

According to a first aspect of the present invention, there is provided a tire molding die according to the present invention, wherein a mold portion for forming a tread is constituted by a plurality of sectors divided in a circumferential direction. In a tire molding die composed of a plurality of blocks divided into sections at every pitch of the tread pattern or every plural pitches, a plurality of narrow slits that allow only air to pass through a tread molding surface of the block are formed in a circumferential direction. And the slit is communicated with the outside of the mold through an exhaust hole provided on the back side thereof.

In the method of manufacturing a tire molding die according to the present invention, the tread pattern forming portion of the sector formed by dividing a tread molding die portion into a plurality of portions in the circumferential direction is provided at every tread pattern pitch or at a plurality of pitches. When manufacturing each block divided into sections, a first exhaust hole is formed on the back side of the tread molding surface of the block to penetrate between both circumferential division faces of the block, and the first exhaust hole and the first exhaust hole are formed. A slit extending in the circumferential direction between the tread molding surface and the slit is formed by wire electric discharge machining, and a shot blasting process is performed on a peripheral portion of the slit on the tread molding surface, so that a narrow opening through which only the air passes through the opening of the slit. The width is formed, and a second exhaust hole is formed between the first exhaust hole and an outer peripheral surface of the block.

As described above, a narrow slit for allowing only air to pass through the tread molding surface of the block is provided in the circumferential direction, and the slit is connected to the outside through the exhaust hole on the back side, so that the influence of the assembly of the block is reduced. The slit can be provided without receiving it at all, and the air in the mold can be reliably discharged from the slit to the outside via the exhaust hole. Therefore, the vulcanization failure due to the slit does not occur. Further, since the slits are formed not in the blocks but in the blocks, the blocks are not divided even if the number of slits is increased, so that the assembly does not become complicated.

Further, by forming the slits using the wire electric discharge machining and the shot blasting as described above, it is possible to easily manufacture the mold.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows an example of a tire molding die according to the present invention. Reference numeral 1 denotes a sector for molding a tread portion of a tire, and a tread molding die portion is divided into a plurality in the circumferential direction. Although only one is shown in the figure, a plurality of sectors are assembled in an annular shape in the circumferential direction to constitute a tread molding die. Above and below this mold,
As shown by phantom lines, upper and lower molds 2 and 3 for molding a sidewall of a tire are assembled to form a sectional tire molding mold.

As shown in FIG. 2, the sector 1 is composed of a plurality of blocks 1B divided by a tread pattern forming section 1A at each pitch of the tread pattern or at a plurality of pitches. A plurality of narrow slits 4 are formed in the circumferential direction on the tread forming surface 1X of each block 1B, on which the groove forming protrusions 5 protrude, to allow only air to pass without passing unvulcanized rubber. .

On the back side of the slit 4 in the block 1B, there is formed a first exhaust hole 7 which penetrates the block 1B between the two circumferential division surfaces 1c (see FIG. 4), and the slit 4 is formed by the first exhaust hole. It communicates with 7. A second exhaust hole 8 communicates with the first exhaust hole 7 from the outer peripheral side of the block 1B so that air flowing out of the slit 4 escapes to the outside of the mold through the exhaust holes 7 and 8.

According to the above-described mold of the present invention, the slit 4 is formed in the tread molding surface 1X of the block 1B in the circumferential direction, and the slit 4 is formed through the exhaust holes 7 and 8 provided on the back side. , The slits 4 can be provided without being affected at all when the block 1B is assembled to form the sector 1, so that the air can be reliably discharged from the slits 4 through the exhaust holes 7, 8. Can be discharged outside.

Further, since the slits 4 are formed in the block 1B, the blocks need not be divided even if the number of the slits 4 is increased, so that the assembly of the blocks is not affected by the number of slits and is always easy. Becomes In the above mold, each block 1B can be manufactured as follows.

First, as shown in FIG. 4, a plurality of first exhaust holes 7 penetrating between the two circumferential division surfaces 1c are sequentially formed on the back side of the tread forming surface 1X of the block 1B by drilling. Next, as shown in FIG. 5, a wire W is inserted into the first exhaust hole 7 as an electrode, and wire electric discharge machining is performed.
That is, the slit 4 extending in the circumferential direction is formed between the first exhaust hole 7 and the tread molding surface 1X by moving the discharging wire W to the tread molding surface 1X side as shown by the arrow.

Since the slit 4 formed by the wire electric discharge machining has a minimum width a of about 0.1 mm at the minimum, it is too wide to allow only air to pass without passing unvulcanized rubber. Therefore, as shown in FIG. 6, a shot blast process using plastic particles, glass particles, or the like is performed on the periphery of the slit on the tread molding surface 1X. Due to the shot peening effect of this blasting, the slit 4
Opening 4a is crushed, and the slit 4 is formed to have a narrow opening width that allows only air to pass through. That is, the state changes from FIG. 6B to FIG. 6C.

Next, drilling is performed from the block outer peripheral surface 1Y side to sequentially form a second exhaust hole 8 communicating between the first exhaust hole 7 and the block outer peripheral surface 1Y. The formation of the second exhaust hole 8 allows the slit 4 to communicate with the outside of the mold through the first exhaust hole 7 and the second exhaust hole 8.

In the present invention, the opening width b of each slit 4 opening on the tread molding surface 1X is 0.01 to 0.01.
It can be in the range of 0.05 mm. The width b is 0.
If it is less than 01 mm, it is too narrow to allow air to escape effectively, and if it is more than 0.05 mm, unvulcanized rubber may enter the slit 4 and cause clogging.

The depth h of the slit 4 is preferably 2 to 5 mm. The number of slits 4 in each block 1B can be appropriately selected according to the tread pattern and the tire size, but can be generally arranged in 5 to 20 rows radial direction (vertical direction in the figure). The diameter of the first exhaust hole 7 formed in a circular cross section is 5 to 10 mm,
Similarly, the diameter of the second exhaust hole having a circular cross section is 5 to 10 mm.
It is preferred that

In the above embodiment, the slit 4 is provided so as to extend in the circumferential direction. In addition to this, as shown in FIG. It may be provided so as to extend in the radial direction.
The slit 14 communicates with a third exhaust hole 17 which penetrates the block 1B on the back side of the slit 1B between the two radial side surfaces 1d, and the third exhaust hole 17 is formed from the outer peripheral surface Y side of the block 1B. (4) It communicates with the exhaust hole 18 to allow air to escape to the outside of the mold. By providing the slits 14 in the radial direction as described above, the air discharging effect can be further enhanced. This slit 14 is formed in each block 1B
Is preferably provided at the center of each. The production can be performed in the same manner as the slit 4 described above.

[0022]

As described above, according to the present invention, a plurality of narrow slits for allowing only air to pass therethrough are formed in the tread forming surface of the block constituting the tread pattern forming portion of the sector in the circumferential direction, and the slits are formed in the tread forming surface. By communicating with the outside of the mold through the exhaust hole provided on the back side,
Since the number of slits can be increased without dividing the block, the assembling work is easy, and since the slits are not affected at all by the assembling, air is reliably discharged from the slits to the outside through the exhaust holes. It is possible to escape and prevent the occurrence of vulcanization failure due to the slit.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an essential part showing an example of a tire molding die of the present invention.

FIG. 2 is an explanatory perspective view of a sector.

FIG. 3 is an enlarged side view of a block constituting a tread pattern forming section of a sector.

4A and 4B show a step of forming a first exhaust hole in the method of manufacturing a tire molding die of the present invention, wherein FIG. 4A is an enlarged side view showing the outer peripheral surface of the block facing down, and FIG. FIG. 3A is a cross-sectional view taken along line AA of FIG.

FIG. 5 shows a step of forming a slit by wire electric discharge machining in the method for manufacturing a tire molding die of the present invention, wherein (a) is an enlarged side view showing the outer peripheral surface of the block as a lower side, and (b). FIG. 3A is a sectional view taken along the line BB in FIG.

FIG. 6 shows a step of narrowing the opening width of the slit by shot blasting in the method for manufacturing a tire molding die of the present invention, and (a) is an enlarged side view showing the outer peripheral surface of the block as a lower side; (B) is an explanatory view showing a slit before shot blasting, and (c) is an explanatory view showing a slit after shot blasting.

FIGS. 7A and 7B show a step of forming a second exhaust hole in the method of manufacturing a tire molding die of the present invention, wherein FIG. 7A is an enlarged side view showing the outer peripheral surface of the block facing down, and FIG. It is CC sectional view taken on the line CC of (a).

FIG. 8 shows an example of a slit provided in a radial direction, and FIG.
(B) is an arrow view seen from the direction of arrow D, (b) is an enlarged side view showing the outer peripheral surface of the block on the lower side, and (c) is an EE view of (b).

[Explanation of symbols]

Reference Signs List 1 sector 1A tread pattern forming portion 1B block 1X tread forming surface 1c circumferential dividing side surface 1d radial side surface 2 upper mold 3 lower mold 4,14 slit 5 groove forming projection 7 first exhaust hole 8 second exhaust hole b slit opening Width h slit depth

Claims (6)

[Claims] 1. A tread forming mold portion is composed of a plurality of circumferentially divided sectors, and a plurality of tread pattern forming portions of each sector are divided at every pitch of the tread pattern or at every plural pitches. In a tire molding die composed of a block, a plurality of narrow slits that allow only air to pass through the tread molding surface of the block are formed in the circumferential direction, and the slits are formed through exhaust holes provided on the back side thereof. A tire molding die that communicates with the outside of the die. 2. The tire molding die according to claim 1, wherein an opening width of the slit opening on the tread molding surface is 0.01 to 0.05 mm. 3. The tire molding die according to claim 1, wherein the depth of the slit is 2 to 5 mm. 4. The tire molding die according to claim 1, wherein 5 to 20 rows of the slits provided in the circumferential direction are arranged in the radial direction. 5. A narrow slit for allowing only air to pass through the tread molding surface in a radial direction.
Or the tire molding die according to 4. 6. When manufacturing each block in which a tread pattern forming section of a sector formed by dividing a tread forming mold section into a plurality of sections in the circumferential direction is divided at every pitch of a tread pattern or at every plural pitches, A first exhaust hole is formed on the back side of the tread forming surface of the block between the circumferentially divided surfaces of the block, and a slit extending in the circumferential direction between the first exhaust hole and the tread forming surface is formed. It is formed by wire electric discharge machining, and shot blasting is performed on the periphery of the slit of the tread forming surface, so that the opening of the slit is formed to have a narrow opening width that allows only air to pass therethrough. A method for manufacturing a tire molding die, wherein a second exhaust hole is formed between the mold and the surface.