JP2017056596A - Tire vulcanizing mold and pneumatic tire manufacturing method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire vulcanizing mold capable of suppressing clogging of a vent passage provided in a bead ring.SOLUTION: Provided is a vulcanizing mold 1 for molding a pneumatic tire having a bead part 6, which includes a bead ring 10 having a bead molding face 10s for molding an outer face of the bead part 6. The bead ring 10 has a vent passage 12 extended from the bead molding face 10s side toward the outer side of the mold. The vent passage 12 includes: a passage main body 15 extended in a cylindrical shape inside the bead ring 10; an opening part 16 which is opened in the bead molding face 10s and extended in an axial direction with an inner diameter larger than the passage main body 15; and a tapered part 17 which connects the opening part 16 and the passage main body 15, and has its inner diameter decreased gradually toward the passage main body 15.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a tire vulcanization mold capable of suppressing clogging of a vent channel provided in a bead ring, and a pneumatic tire manufacturing method using the same.

  For example, Patent Literature 1 below describes a tire vulcanization mold in which a vent channel is provided in a bead ring. Such a vent channel can discharge air between the bead ring and the bead portion of the green tire to the outside of the mold during vulcanization molding. For this reason, the dent of a bead part (henceforth a "bear" may be called) by the residual of air is suppressed.

  In general, at the time of vulcanization molding, a part of the rubber in the bead portion enters the vent flow path and is cured therein to form a vent spew. Originally, it is desirable that the vent spew is drawn out from the vent flow path together with the tire when the mold and the bead portion of the tire are separated from each other after the vulcanization molding. This is because if the vent spew is cut from the bead portion and remains in the vent flow path, the vent flow path may be clogged, and as a result, a molding defect such as a bear may occur during the next vulcanization molding.

  However, the vent spew formed by the vent flow path provided in the bead ring tends to be easily cut at the base portion due to the shape of the bead portion when the mold and the tire are separated. .

JP 2009-18509 A

  The present invention has been devised in view of the actual situation as described above, and is based on the improvement of the shape of the vent channel, and the tire vulcanization capable of suppressing clogging of the vent channel provided in the bead ring. The main purpose is to provide molds.

  The present invention is a vulcanization mold for molding a pneumatic tire having a bead portion, and includes a bead ring having a bead molding surface for molding an outer surface of the bead portion, and the bead ring is formed by the bead molding. There is a vent channel extending from the surface side to the outside of the mold, and the vent channel is formed in a cylindrical shape in the bead ring, and opens at the bead molding surface and is larger than the channel body. An opening portion extending in the axial direction with an inner diameter, and a tapered portion that connects the opening portion and the flow channel main body and has an inner diameter gradually decreasing toward the flow channel main body are included.

  In the tire vulcanization mold according to the present invention, it is preferable that the bead molding surface includes a bead heel molding surface for molding a bead heel having an arcuate cross section, and the opening portion is provided on the bead heel molding surface.

  In the tire vulcanization mold according to the present invention, it is desirable that the axial direction of the opening portion and the tapered portion extends in a normal direction with respect to the bead heel.

  In the tire vulcanization mold according to the present invention, it is preferable that the opening portion has an axial length of 0.1 to 0.5 mm and an inner diameter of 2.0 to 3.5 mm.

  In the tire vulcanization mold according to the present invention, the bead ring is supported so as to be movable in a first direction, and at least the opening portion and the taper portion of the vent channel have the axial directions thereof as described above. It is desirable to have an angle difference of 10 ° or more with respect to the first direction.

  According to a second aspect of the present invention, there is provided a method for producing a pneumatic tire, including a step of vulcanizing and molding a green tire using any of the tire vulcanization molds described above.

  The vent flow path provided in the bead ring of the tire vulcanization mold of the present invention includes a flow path body extending in a cylindrical shape in the bead ring, an axial direction with an inner diameter that is larger than the flow path body and opens at the bead molding surface. And an opening portion that extends, and a tapered portion that connects the opening portion and the flow channel body and has an inner diameter that gradually decreases toward the flow channel body.

  In such a vent flow path, the rubber enters the flow path main body after the opening portion and the tapered portion are filled with rubber at the time of vulcanization molding, so that the substantial length of the vent spew can be reduced. In addition, the vent spew formed by the vent channel of the present invention has a large rubber volume at the root portion, so that the vent spew is effectively cut and clogging of the vent channel is suppressed.

It is sectional drawing of the tire vulcanization metal mold | die of one Embodiment of this invention. It is a front view of the bead ring of FIG. FIG. 3 is a cross-sectional view of the bead ring of FIG. 2 taken along line BB. It is an expanded sectional view of a vent channel.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a cross-sectional view of a tire vulcanization mold 1 of the present embodiment. As shown in FIG. 1, a tire vulcanization mold (hereinafter may be simply referred to as “vulcanization mold”) 1 of the present embodiment has an unvulcanized raw tire 2 on its inner side. A molding surface for molding the outer surface 2s is provided. The raw tire 2 is heated in the vulcanization mold 1 and is pressed from the inside to the molding surface side by the expanded bladder 3. Thereby, the raw tire 2 is vulcanized.

  The raw tire 2 includes a tread portion 4, sidewall portions 5 extending inward in the tire radial direction from both ends thereof, and bead portions 6 disposed on the inner side in the tire radial direction. The raw tire 2 has a known configuration such as a carcass extending from the tread portion 4 through the sidewall portion 5 to the bead portion 6, a belt layer disposed outside the carcass in the tire radial direction and inside the tread portion 4, and the like. It is. In FIG. 1, the carcass and the belt layer are omitted.

  The tire vulcanization mold 1 of the present embodiment includes, for example, a tread segment 8, a sidewall ring 9, and a bead ring 10. The tread segment 8 has a tread molding surface 8 s for molding the tread portion 4. A plurality of tread segments 8 are arranged in the tire circumferential direction, and form the entire circumference of the tread portion 4. A pair of sidewall rings 9 are provided on the inner side in the tire radial direction of the tread segment 8. Each sidewall ring 9 has a sidewall molding surface 9 s for molding the sidewall portion 5. The sidewall molding surface 9s of the present embodiment can also mold a part of the bead portion 6, for example. The sidewall ring 9 has, for example, a ring shape that extends continuously over the entire circumference of the tire. A known configuration is preferably used for the tread segment 8 and the sidewall ring 9.

  The bead ring 10 is provided on the inner side in the tire radial direction of each sidewall ring 9. The bead ring 10 has a bead forming surface 10 s for forming the bead portion 6. The bead molding surface 10 s molds the outer surface of the bead portion 6 together with the sidewall molding surface 9 s of the sidewall ring 9.

  FIG. 2 shows a front view of the bead ring 10 of FIG. 1 as viewed from the A direction. As shown in FIG. 2, the bead ring 10 is, for example, an annular shape extending continuously over the entire circumference of the tire.

  The bead ring 10 is provided with a vent channel 12 that opens at a bead molding surface 10s. In the present embodiment, a plurality of vent flow paths 12 are provided in the circumferential direction of the bead ring 10. The vent channel 12 can discharge molding air between the bead portion of the green tire and the bead ring 10 to the outside of the mold during vulcanization molding, thereby suppressing molding defects such as bears.

  FIG. 3 shows a cross-sectional view taken along the line BB through the vent channel 12 of the bead ring 10 of FIG. As shown in FIG. 3, the vent channel 12 extends from the bead molding surface 10 s side to the outside of the mold. The vent channel 12 is connected to, for example, a vacuum means for sucking air outside the mold (not shown). In addition, a well-known thing is used for a vacuum means.

  FIG. 4 shows an enlarged cross-sectional view of the vent channel 12. As shown in FIG. 4, the vent channel 12 includes a channel body 15, an opening portion 16, and a tapered portion 17. The flow path body 15 extends in a cylindrical shape within the bead ring 10. The opening portion 16 opens at the bead molding surface 10 s and extends in the axial direction with an inner diameter larger than that of the flow path body 15. The tapered portion 17 connects the opening portion 16 and the flow channel body 15, and the inner diameter gradually decreases toward the flow channel body 15.

  In such a vent channel 12, since the rubber enters the channel body 15 after the opening portion 16 and the taper portion 17 are filled with rubber during vulcanization molding, the substantial length of the vent spew is reduced. be able to. In addition, while the opening portion 16 and the tapered portion 17 are filled with rubber, the flow path body 15 can continue to discharge air, so that the remaining of air can be further suppressed. In addition, the vent spew formed by the vent flow path 12 of the present embodiment has a large rubber volume at the root portion, so that the vent spew is effectively cut and clogging of the vent flow path is suppressed.

  The flow path main body 15 of this embodiment extends linearly, for example. However, the flow path body 15 may be bent in the middle according to the shape of the bead ring 10. The channel body 15 has an inner diameter W1 of 0.6 to 1.5 mm, for example. If the inner diameter W1 is smaller than 0.6 mm, the vent channel 12 may be easily clogged. When the inner diameter W1 is larger than 1.5 mm, the formed vent spew is increased, and the tire appearance may be deteriorated.

  As shown in FIG. 3, it is desirable that the opening portion 16 is opened at a bead heel forming surface 14 for forming a bead heel having an arcuate cross section, for example. Thereby, at the time of vulcanization molding, the air on the tire radius outer side and the rim contact surface 21 side than the bead heel is effectively discharged.

  For example, the opening portion 16 is preferably open in a circular shape (not shown). As shown in FIG. 4, the inner diameter W2 of the opening portion 16 is preferably 2.0 mm or more, more preferably 2.5 mm or more, preferably 3.5 mm or less, more preferably 3.0 mm or less. Such an opening portion 16 can increase the rigidity of the root portion of the vent spew while suppressing deterioration of the appearance of the bead portion due to the vent spew.

  The minimum length L1 in the axial direction of the opening portion 16 is preferably 0.1 to 0.5 mm. When the length L1 is smaller than 0.1 mm, the rigidity of the root portion of the vent spew may be reduced. When the length L1 is larger than 0.5 mm, the appearance of the bead heel may be deteriorated.

  The taper part 17 is formed in a truncated cone shape, for example. In the present embodiment, in the cross section including the central axis of the vent channel 12, the inner surface 18 of the taper portion 17 extends linearly. However, the inner surface 18 of the tapered portion 17 may be smoothly curved in the cross section.

  In the cross section, the angle θ1 of the inner surface 18 of the tapered portion 17 with respect to the axial direction of the vent channel 12 is, for example, 35 to 55 °. Such a taper part 17 can raise the flexibility of the root part of a vent spew, and can suppress the cutting | disconnection of a vent spew.

  In order to further enhance the above-described effect, the maximum first inner diameter W3 of the tapered portion 17 is, for example, 1.0 to 1.5 mm. The ratio W1 / W3 between the inner diameter W1 of the flow path main body 15 and the first inner diameter W3 of the tapered portion 17 is preferably 0.40 or more, more preferably 0.45 or more, and preferably 0.1. 55 or less, more preferably 0.50 or less.

  As shown in FIG. 3, the axial direction of the opening portion 16 and the tapered portion 17 extends, for example, in the normal direction to the bead heel. Thereby, at the time of vulcanization molding, the air on the tire radial outside of the bead heel and the rim contact surface 21 side is effectively discharged. On the other hand, the bead ring 10 is supported so as to be movable in a first direction (for example, parallel to the rotation axis direction of the tire to be molded) so that it can be separated from the tire after vulcanization molding. For this reason, at least the opening portion 16 and the tapered portion 17 of the vent channel 12 have an axial difference θ2 (not shown) of 10 ° or more with respect to the first direction.

  When the angle difference θ2 is large, when the bead ring 10 is pulled away from the tire, not only a tensile force but also a shear stress acts on the root portion of the vent spew. In this embodiment, the rigidity of the vent spew root portion is increased. Since it is large, the angle difference θ2 can be set large. Therefore, in order to improve the air exhaustability during vulcanization molding, the angle difference θ2 is preferably set to 15 ° or more, more preferably 20 ° or more. However, if the angle difference θ2 is excessive, the vent spew may be easily cut. For this reason, the said angle difference (theta) 2 becomes like this. Preferably it is 30 degrees or less, More preferably, it is 25 degrees or less.

  The tire vulcanization mold according to the above-described embodiment is suitably used for a known pneumatic tire manufacturing method. As described above, the method for manufacturing a pneumatic tire using the tire vulcanization mold according to the present invention suppresses clogging in the vent flow path provided in the bead ring, so that the frequency of bead ring maintenance is low. As a result, excellent productivity can be exhibited.

  The tire vulcanization mold according to one embodiment of the present invention has been described in detail above. However, the present invention is not limited to the specific embodiment described above, and can be implemented with various modifications. .

  As an example, a tire vulcanization mold composed of a bead ring having a vent channel shown in FIG. As a comparative example, a tire vulcanization mold composed of a bead ring having a vent channel composed only of a cylindrical channel main body was prototyped. The tire productivity was measured using each tire vulcanization mold. The measuring method is as follows.

<Tire productivity>
Tires were produced with each tire vulcanization mold, and the number of vulcanizations until the vent channel was clogged was measured. A result is an index which sets the number of vulcanizations of a comparative example to 100, and shows that it is excellent in tire productivity, so that the number of vulcanizations is large, so that a numerical value is large.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the tire vulcanization mold of the example effectively suppressed clogging of the vent flow path provided in the bead ring.

6 Bead part 10 Bead ring 10s Bead molding surface 12 Vent flow path 15 Flow path body 16 Opening part 17 Tapered part

Claims (6)

A vulcanization mold for molding a pneumatic tire having a bead portion,
Including a bead ring having a bead molding surface for molding the outer surface of the bead portion;
The bead ring has a vent channel extending from the bead molding surface side to the outside of the mold,
The vent channel includes a channel main body extending in a cylindrical shape in the bead ring, an opening portion that opens at the bead molding surface and extends in an axial direction with an inner diameter larger than the flow channel main body, the opening portion, and the A tire vulcanization mold characterized by including a taper portion that connects a flow path body and gradually decreases in inner diameter toward the flow path body. The bead molding surface includes a bead heel molding surface for molding a bead heel having an arc-shaped cross section,
The tire vulcanization mold according to claim 1, wherein the opening portion is provided on the bead heel molding surface.   The tire vulcanization mold according to claim 2, wherein axial directions of the opening portion and the tapered portion extend in a normal direction with respect to the bead heel.   The tire vulcanization mold according to any one of claims 1 to 3, wherein the opening portion has an axial length of 0.1 to 0.5 mm and an inner diameter of 2.0 to 3.5 mm. The bead ring is supported so as to be movable in a first direction;
The tire addition according to any one of claims 1 to 3, wherein at least the opening portion and the tapered portion of the vent flow path have an angular difference of 10 ° or more with respect to the first direction. Sulfur mold.   A method for producing a pneumatic tire, comprising a step of vulcanizing a green tire using the tire vulcanization mold according to any one of claims 1 to 5.

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