JP2018008450A - Bent piece and rubber mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the inflow of a rubber material while suppressing the inflow of the rubber material and enabling the exhaust from the vent hole. A vent piece (30) attached to a vent hole (26) of a rubber molding die (10), which is composed of an aggregate of particulates, and an outer peripheral part (32) fitted into the vent hole forms an inner part (34) thereof. The vent piece is formed of the granular material 38 having a larger particle size than the granular material 36. Further, the vent piece 30 is the rubber molding die 10 attached to the vent hole 26. [Selection diagram] Figure 2

Description

  Embodiments described herein relate generally to a vent piece and a rubber molding die.

  A mold used for molding a rubber product such as a tire (that is, a mold for rubber molding) is provided with a vent hole as an exhaust hole for exhausting air inside the mold. For example, many vent holes are formed in a tire vulcanization mold in order to exhaust air existing between an unvulcanized tire and a mold.

  In these vent holes, a rubber material flows into the vents to form hook-like projections called spews, so that a separate removal step is required. Therefore, various proposals have been made in order to suppress the inflow of the rubber material while enabling the exhaust from the vent hole. For example, Patent Document 1 discloses using a porous body made of a sintered metal as a vent piece attached to a belt hole.

JP 2007-062235 A

  As described above, the vent piece is attached to the vent hole of the mold and is a separate part from the mold main body, so that it is necessary to prevent the vent piece from falling off. That is, it is desirable that the vent piece is firmly fixed to the vent hole in order to avoid the vent piece from leaving the vent hole and remaining in the rubber product when the rubber product is removed.

  An object of the present invention is to provide a vent piece that can prevent the rubber material from flowing in and can be exhausted from the vent hole while suppressing the escape from the vent hole.

  The vent piece according to the embodiment of the present invention is a vent piece attached to a vent hole of a rubber molding die, and is composed of an aggregate of granular materials, and the outer peripheral portion is compared with the granular material forming the inner portion. It is formed of a granular material having a large particle size.

  In the rubber molding die according to the embodiment of the present invention, the vent piece is attached to a vent hole.

  According to this embodiment, it is possible to suppress the escape from the vent hole while suppressing the inflow of the rubber material and enabling the exhaust from the vent hole.

It is sectional drawing of the metal mold | die for rubber molding which concerns on one Embodiment. It is a principal part expanded sectional view of the metal mold | die for rubber molding which shows the state which attached the vent piece to the vent hole. (A) is a top view of a vent piece, (B) is the XX sectional drawing.

  Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of a rubber mold 10 according to an embodiment. The mold 10 is a mold for vulcanizing a pneumatic tire, that is, a tire vulcanization mold. The mold 10 forms an annular tread mold portion 12 for molding a tire tread portion, a pair of upper and lower side mold portions 14, 14 for molding a tire sidewall portion, and a tire bead portion. A pair of upper and lower bead rings 16 and 16 are provided to form a cavity 18 that is a molding space for a pneumatic tire.

  The tread molding surface which is the inner peripheral surface of the tread mold portion 12 is provided with ridges 20 for forming grooves in the tread portion, and regions defined by these ridges 20 are ribs or blocks on the tread portion. It becomes the recessed part 22 for forming the land part.

  The inner surface 24 of the mold including the tread molding surface is provided with a vent hole 26 for venting air that communicates with the outside of the mold 10. A vent hole 26 is provided in each recess 22. The vent hole 26 is provided not only on the inner peripheral surface of the tread mold part 12 but also on the side wall molding surface of the side mold part 14.

  As shown in FIG. 2, a vent piece 30 is attached to the vent hole 26. As shown in FIG. 3, the vent piece 30 is formed of an aggregate of granular materials, and the outer peripheral portion 32 fitted into the vent hole 26 has a larger particle diameter than the granular material 36 forming the inner portion 34. It is formed of an object 38. That is, the vent piece 30 is an aggregate formed by integrating a large number of granular materials, and is an inner portion 34 that is a core portion formed of the granular material 36 having a small particle size, and a sheath portion that surrounds the outer periphery thereof. And an outer peripheral portion 32 formed of a granular material 38 having a large particle size. Since the vent piece 30 is composed of an aggregate of the granular materials 36 and 38, the vent piece 30 is a porous body having voids between the granular materials and the voids communicating with each other. Therefore, it has many vertical holes extended in an axial direction (height direction), and can permeate | transmit air to the said axial direction.

  As a material of the granular materials 36 and 38 which comprise the vent piece 30, metals, such as iron (for example, steel) and aluminum, are preferable. The shape of the granular materials 36 and 38 is preferably a sphere.

  The vent piece 30 has a columnar shape, preferably a cylindrical shape, and the outer diameter D is not particularly limited, and may be, for example, 2.0 to 5.0 mm or 2.0 to 3.5 mm. Moreover, the height (axial direction length) L is not specifically limited, For example, 5-20 mm may be sufficient and 10-15 mm may be sufficient.

  The vent piece 30 has an inner portion 34 made of a granular material 36 having a small particle size as a main portion, and the outer periphery thereof is surrounded by the outer peripheral portion 32 over the entire periphery. Specifically, the inner portion 34 has a columnar shape, preferably a columnar shape, and the outer peripheral portion 32 has a cylindrical shape, preferably a cylindrical shape. In this example, the outer peripheral portion 32 is formed in a single particle film shape in which a granular material 38 having a large particle diameter is provided in a single layer structure on the outer peripheral surface of the inner portion 34. As shown in FIG. 3A, the end faces 40, 40 on both sides in the axial direction of the vent piece 30 are configured by an inner portion 34 and an outer peripheral portion 32 surrounding the periphery.

  The particle size of the granular material 36 forming the inner portion 34 is preferably 0.2 to 0.6 mm. Thereby, the effect of suppressing clogging due to the inflow of the rubber material can be enhanced while ensuring air permeability. The particle size of the granular material 38 forming the outer peripheral portion 32 is preferably 0.4 to 1.0 mm. Thereby, the effect which suppresses the escape of the vent piece 30 from the vent hole 26 can be heightened. The ratio of the particle size of the granular material 38 in the outer peripheral portion 32 to the particle size of the granular material 36 in the inner portion 34 is not particularly limited, but may be 1.3 to 2.5 times, for example, 1.5 to 2. It may be 0 times. The granular materials 36 and 38 are preferably spheres as described above, and more preferably spheres having a uniform diameter with no variation in particle diameter.

  Here, the particle size of the granular materials 36 and 38 is obtained by microscopic observation, and the diameter (length at the maximum difference portion) of 10 granular materials randomly extracted using this image is obtained. It is an average particle diameter obtained as an arithmetic average by measuring.

  The vent piece 30 is preferably a sintered body (porous sintered body) made up of a large number of granular materials, and is sintered by a normal sintering method or a 3D laser printer using granular materials having different particle sizes. It can be manufactured by law. As a normal sintering method, there is a method of forming by a mold and sintering by heating while applying pressure. As a sintering method using a 3D laser printer, for example, a powder sintering additive manufacturing method or the like can be used. In the case of a normal sintering method, for example, a columnar body that becomes the inner portion 34 is produced by sintering using a granular material 36 having a small particle size, and a large particle size granular material 38 is wound around the columnar body. The vent piece 30 is obtained by sintering. In the case of a sintering method using a 3D laser printer, for example, a columnar body serving as the inner portion 34 is manufactured using a small particle particle 36 and a large particle particle 38 is used. The vent piece 30 is obtained by manufacturing the cylindrical body used as the outer peripheral part 32 with a 3D laser printer, and then inserting a columnar body inside the cylindrical body and sintering the interface between the two.

  As shown in FIG. 2, the vent piece 30 is fitted and fixed in the vent hole 26. The vent piece 30 is attached with its end face 40 facing the cavity 18 of the mold 10 and is exposed to the molding surface of the mold 10. Therefore, the end surface 40 of the vent piece 30 constitutes a part of the molding surface.

  Specifically, the vent hole 26 is provided with a mounting hole 28 in which the vent piece 30 is mounted. The mounting hole 28 is a cylindrical hole opening in the mold inner surface 24 at the end of the vent hole 26 on the mold inner surface 24 side, and a step portion 28A is provided with respect to the main body flow path portion of the vent hole 26. It has a widened shape. The mounting hole 28 is formed in a size corresponding to the outer diameter D and height L of the vent piece 30. In this example, when the vent piece 30 is press-fitted into the vent hole 26, the vent piece 30 is tightly fitted. Thus, the inner diameter of the mounting hole 28 is set slightly smaller than the outer diameter of the vent piece 30.

  In the present embodiment, the granular material 38 that forms the outer peripheral portion 32 of the vent piece 30 is formed of a material that is harder than the wall surface of the vent hole 26. As an example, iron may be used as the material of the granular materials 36 and 38 constituting the vent piece 30, and the mold 10 (for example, the tread mold portion 12) provided with the vent hole 26 may be formed of aluminum.

  When manufacturing a pneumatic tire using the mold 10 having the above-described configuration, an unvulcanized tire (green tire) is set in the mold 10 and the mold is closed, and then a bladder (not shown) disposed inside is used. The unvulcanized tire is vulcanized and molded by pressing the unvulcanized tire against the inner surface 24 of the mold and keeping it heated. At this time, in the present embodiment, the air accumulated between the unvulcanized tire and the mold inner surface 24 passes through the vent piece 30 made of a porous body and is discharged to the outside through the vent hole 26. The rubber material is prevented from entering the vent hole 26 by the vent piece 30 made of a porous material. Therefore, it is possible to prevent the rubber material from flowing into the vent hole 26 while allowing the exhaust from the vent hole 26, and the spew removing step is not necessary.

  In the present embodiment, since the outer peripheral portion 32 of the vent piece 30 is formed of the granular material 38 having a larger particle size than the inner portion 34, the following effects can be obtained. That is, the mold 10 generally expands due to heat during molding. Due to the thermal expansion of the mold 10, the wall surface of the vent hole 26 is deformed so as to enter the gap between the particulates 38 of the vent piece 30. At this time, if the particle diameter of the vent piece outer peripheral portion 32 with which the vent hole 26 is in contact is large, the unevenness of the wall surface of the vent hole 26 formed by entering the gap between the granular materials 38 also increases. Therefore, this unevenness has a retaining structure, and the vent piece 30 can be effectively prevented from coming off from the vent hole 26.

  In addition, the vent piece 30 has a high effect of suppressing the inflow of the rubber material because the inner portion 34 is made of a granular material 36 having a small particle diameter. Further, the air layer present inside the inner portion 34 makes it easy to ensure heat retention, and can provide the same vulcanization promoting effect as the portion where the vent hole 26 is not provided.

  Moreover, in this embodiment, since the granular material 38 which forms the outer peripheral part 32 of the vent piece 30 is made of a material having a hardness higher than that of the wall surface of the vent hole 26, the following operational effects are achieved. That is, when the vent piece 30 is press-fitted into the vent hole 26, the wall surface of the vent hole 26 having a low hardness is deformed so as to enter the gap between the granular materials 38 constituting the vent piece 30. The unevenness of the wall surface of the vent hole 26 formed by this deformation forms a retaining structure, and the vent piece 30 can be prevented from coming off from the vent hole 26. Therefore, a retaining structure with unevenness can be formed from the stage before the thermal expansion described above, and the retaining effect can be enhanced. In addition, since the granular material 38 on the outer peripheral side has a large particle size, the formed irregularities are large, and the retaining effect can be further enhanced.

  In the above-described embodiment, a material having a hardness higher than that of the wall surface of the vent hole 26 is used for the granular material 38 that forms the outer peripheral portion 32 of the vent piece 30. On the contrary, the outer peripheral portion 32 is formed. A material having a lower hardness than the wall surface of the vent hole 26 may be used for the granular material 38. For example, aluminum may be used as the material of the particulates 36 and 38 constituting the vent piece 30, and the mold 10 (for example, the tread mold portion 12) provided with the vent hole 26 may be formed of iron. In that case, when the vent piece 30 is press-fitted into the vent hole 26, the granular material 38 having a low hardness is crushed, thereby increasing the contact area with the wall surface of the vent hole 26, and exhibiting a retaining effect by increasing the contact area. Can do.

  Moreover, you may form the granular material 38 which forms the outer peripheral part 32 of the vent piece 30, and the wall surface of the vent hole 26 with the same material. By using the same material, the thermal conductivity of the vent piece 30 and the surrounding mold 10 can be matched, and the difference in the vulcanization promoting effect between the two can be reduced.

  As one embodiment, when the tread mold part 12 is formed of aluminum and the side mold part 14 is formed of iron, iron may be used as the granular materials 36 and 38 constituting the vent piece 30. In this case, in the vent hole 26 of the tread mold portion 12, the unevenness of the wall surface of the vent hole 26 formed when the vent piece 30 is press-fitted can be increased. On the other hand, the vent hole 26 of the side mold part 14 is formed of the same material as the vent piece 30, so that the difference in vulcanization acceleration effect can be reduced by matching the thermal conductivity.

  In the above-described embodiment, the tire vulcanization mold has been described. However, for example, it can be used for a mold for molding various rubber products such as a vibration-proof rubber member.

  Although some embodiments have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 10 ... Mold, 12 ... Tread mold part, 14 ... Side mold part, 18 ... Cavity, 24 ... Mold inner surface, 26 ... Vent hole, 30 ... Vent piece, 32 ... Outer part, 34 ... Inner part, 36 ... Outer part Part granular material, 38 ... Inner part granular material, 40 ... End face

Claims (5)

  A vent piece attached to a vent hole of a mold for rubber molding, which is composed of an aggregate of granular materials, and an outer peripheral portion is formed of a granular material having a larger particle diameter than the granular material forming the inner portion. Bent piece.   The particle size of the granular material forming the inner portion is 0.2 to 0.6 mm, and the particle size of the granular material forming the outer peripheral portion is 0.4 to 1.0 mm. Bent piece.   A mold for rubber molding in which the vent piece according to claim 1 or 2 is attached to a vent hole.   The rubber mold according to claim 3, wherein an end face of the vent piece faces a cavity of the mold.   The rubber molding die according to claim 3 or 4, wherein the granular material forming the outer peripheral portion of the vent piece is made of a material having hardness higher than that of the wall surface of the vent hole.

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