JP2013059908A - Tire vulcanizing mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire vulcanizing mold which can suppress the bending of a vent piece when being inserted into a vent hole and reduce the length of a spew.SOLUTION: In the tire vulcanizing mold in which the tire molding surface 1a molding the outer surface of the tire is provided with the vent hole 5 that discharges air present between the outer surface of a tire and a tire molding surface 1a during vulcanization molding, the cylindrical vent piece 6 made of an iron-based material is inserted into the vent hole 5, and an intervention layer 7 which is formed from a material softer than a mold body and the cylindrical vent piece 6 and has a thickness of 500 μm or below is located in the interface 56 between the vent hole 5 and the cylindrical vent piece 6.

Description

  The present invention relates to a tire vulcanization mold in which a vent hole is provided on a tire molding surface for molding an outer surface of a tire.

  Conventionally, in a tire vulcanization mold, a plurality of vent holes are provided on a tire molding surface for molding an outer surface of a tire. This vent hole leads to the inside and outside of the mold, and prevents the occurrence of dents called bears by discharging air between the outer surface of the tire and the tire molding surface during vulcanization molding It is.

  At the time of vulcanization molding, rubber on the outer surface of the tire flows into the vent hole, thereby forming a large number of rubber protrusions called spews. The spew is generally excised by trimming, but there are cases where the spew remains at a portion where trimming is difficult. Therefore, in order to improve the appearance of the tire, a cylindrical vent piece is inserted into the vent hole to form a thin and short spew (for example, Patent Documents 1 to 3 below).

  However, due to the surface roughness of the inner wall of the vent hole and the surface roughness of the outer surface of the vent piece, the actual contact area between the vent hole and the vent piece is reduced. Instead, an air layer is interposed at the interface between the vent hole and the vent piece. . Since air has high heat insulating properties, heat conduction from the mold body to the vent piece is hindered, the progress of vulcanization of unvulcanized rubber flowing into the vent hole is suppressed, and a spew is formed longer. When the spew is long, the spew is easily cut when the tire is released from the mold after vulcanization molding, and the cut spew remains in the vent hole. As a result, the vent hole is clogged, and air may not be discharged during vulcanization molding to generate a bear.

  Therefore, the diameter of the vent hole is made smaller than the outer diameter of the vent piece, and the actual contact area is increased by press-fitting and driving into the fitting condition to increase the actual contact area, thereby suppressing deterioration of heat conduction from the mold body to the vent piece. It is usually adopted. However, due to the insertion method by press-fitting and driving-in, there is a problem that a defective construction such as bending and insertion of the bent piece is likely to occur, and there is a problem that a deformed spew is formed due to the bent or narrowed bent piece. In addition, the actual contact area between the vent hole and the vent piece cannot be appropriately increased, and it is difficult to improve the heat conduction from the mold body to the vent piece.

JP-A-5-138656 JP 2000-102926 A JP 2008-30402 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a tire vulcanization mold that can suppress bending of a vent piece when fitting into a vent hole and reduce the length of spew. It is in.

  The above object can be achieved by the present invention as described below. That is, the tire vulcanization mold according to the present invention is provided with a vent hole for discharging air between the outer surface of the tire and the tire molding surface during vulcanization molding on the tire molding surface for molding the outer surface of the tire. In the obtained tire vulcanization mold, a cylindrical vent piece made of an iron-based material is fitted into the vent hole, and is softer than the mold main body and the vent piece at the interface between the vent hole and the vent piece. It is characterized by comprising an intervening layer made of a material and having a thickness of 500 μm or less.

  In the tire vulcanization mold according to the present invention, the bent piece is made of a hard iron-based material as compared with copper, aluminum, or the like, so that bending of the bent piece when fitted into the vent hole can be suppressed. In the present invention, an intervening layer made of a material softer than the mold body and the vent piece and having a thickness of 500 μm or less is interposed at the interface between the vent hole and the vent piece. The vent hole and vent are generated by the surface roughness of the inner wall of the vent hole and the surface roughness of the outer surface of the vent piece by the deformation of the intervening layer corresponding to the minute uneven shape of the inner wall of the vent hole and the outer surface of the vent piece. The air layer at the interface with the piece can be removed. As a result, heat conduction from the mold body to the vent piece can be improved, vulcanization of the unvulcanized rubber that has flowed into the vent hole can be promoted and fluidity can be reduced, and the length of spew can be reduced. .

  In the tire vulcanization mold according to the present invention, it is preferable that the intervening layer is made of a material having better thermal conductivity than the mold body or the vent piece. By constituting the intervening layer with a material having excellent heat conductivity, heat conduction from the mold body to the vent piece can be further improved, and the length of spew can be effectively reduced.

  In the tire vulcanization mold according to the present invention, it is preferable that the intervening layer is formed by being laminated on the inner wall of the vent hole or the outer surface of the vent piece by coating or plating. According to this configuration, an intervening layer having a uniform thickness can be interposed in the entire interface between the vent hole and the vent piece, and heat conduction from the mold body to the vent piece can be further improved. Can be effectively reduced.

  In the tire vulcanization mold according to the present invention, it is preferable that the intervening layer is a paste having a viscosity measured by a B-type viscometer at 25 ° C. of 10,000 mPa · s or more. According to this configuration, by inserting the vent piece into the vent hole with the paste-like intervening layer applied to the inner wall of the vent hole and / or the outer surface of the vent piece, the interface between the vent hole and the vent piece is obtained. An intervening layer can be easily interposed.

  In the tire vulcanization mold according to the present invention, the intervening layer is preferably made of an epoxy resin adhesive in which a powder of a metal material is kneaded. According to this configuration, the thermal conductivity of the intervening layer can be improved, and the intervening layer can be easily applied to the inner wall of the vent hole and / or the outer surface of the vent piece.

1 is a longitudinal sectional view showing an example of a tire vulcanization mold according to the present invention. Sectional drawing which expands and shows the vent hole provided in the tire molding surface Sectional view showing enlarged vent piece

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an example of a tire vulcanization mold according to the present invention. The tire vulcanization mold (hereinafter may be simply referred to as a mold) of the present embodiment includes a tread mold part 1 that abuts on a tread part of the tire, a side mold part 2 that abuts on a sidewall part of the tire, and the like. 3 and a bead ring 4 to which a bead portion of a tire is fitted.

  At the time of vulcanization molding, the mold is opened by an unillustrated opening / closing mechanism, the green tire is set so that the tire axial direction is up and down, the mold is clamped, and a rubber bag called a bladder is inflated to expand the green tire. Extended deformation. Thereby, the outer surface of the green tire is pressed against the tire molding surface 1a and molded.

  Although not shown, the tire molding surface 1a is provided with a bone portion (convex portion) for forming a groove portion and a concave portion for forming a land portion. A tread pattern corresponding to the shape is formed on the tread surface of the tire. The tire molding surface 1a is formed with a plurality of vent holes communicating with the inside and outside of the mold so that air between the outer surface of the tire and the tire molding surface 1a can be discharged. Usually, a vent hole is provided in each of the recesses.

  FIG. 2 is an enlarged cross-sectional view showing a vent hole provided in the tire molding surface 1a. A cylindrical vent piece 6 is fitted in the vent hole 5. The vent piece 6 is made of an iron-based material such as stainless steel or carbon steel. Thereby, the bending of the vent piece 6 when fitting into the vent hole 5 can be suppressed. Further, since the iron-based material has a larger heat capacity than copper and aluminum, the vent piece 6 is used when the mold is opened when the green tire is set in the mold and when the unvulcanized rubber flows into the vent piece 6. Since the temperature drop on the inner surface of the steel does not easily occur, vulcanization proceeds appropriately and the spew can be shortened. In addition, iron-based materials are less resistant to spewing during mold release after vulcanization (resistance to spews coming out of holes) than metals with high (strong) adhesion to rubber like copper materials. Does not increase. The vent piece 6 is preferably formed of a material having a Mohs hardness of 5.0 or more. Thereby, the damage of the inner surface of the vent piece 6 can be prevented even during cleaning by using a drill bit or the like for removing contamination such as vulcanized gas and scraping off contaminated deposits.

  In the present embodiment, the head of the vent piece 6 located on the opening 5a side of the vent hole 5 is simplified in order to simplify the operation of inserting a drill into the vent piece 6 when the vent hole 5 is clogged (drilling operation). A countersink is formed on the surface. However, in the present invention, the vent piece 6 may not have a countersink. The outer diameter D1 of the vent piece 6 is preferably twice or more than the inner diameter D2, and more preferably four times or more. Thereby, the thickness of the vent piece 6 can be ensured, and the bending at the time of fitting into the vent hole 5 can be effectively suppressed.

  An intervening layer 7 made of a material softer than the mold body and the vent piece 6 is interposed at an interface 56 between the vent hole 5 and the vent piece 6. The mold body of the present invention refers to a mold provided with a vent hole 5, and in this embodiment refers to the tire molding surface 1a. The mold body is made of an iron-based material or an aluminum alloy having a Mohs hardness of 4.0 or more. Specific examples of the material include an aluminum alloy casting (AC7A) or a general structural rolled steel (SS400).

  At the interface 56 between the vent hole 5 and the vent piece 6, the actual contact area between the vent hole 5 and the vent piece 6 is reduced due to the surface roughness of the inner wall of the vent hole 5 and the surface roughness of the outer surface of the vent piece 6. In addition, an air layer is interposed at the interface 56 between the vent hole 5 and the vent piece 6. In the present invention, the intervening layer 7 is deformed corresponding to the minute uneven shape of the inner wall of the vent hole 5 and the outer surface of the vent piece 6, thereby removing the air layer at the interface 56 between the vent hole 5 and the vent piece 6. can do.

  The intervening layer 7 is made of a metal different from the material of the mold body and the vent piece 6, specifically, a metal such as copper, silver, aluminum, or zinc. The intervening layer 7 is preferably formed of a material having a Mohs hardness of 3.0 or less. Furthermore, the intervening layer 7 is more preferably formed of a material having a hardness difference of 1.5 or more from the material of the mold body and the vent piece 6. In the present invention, since the vent piece 6 is inserted into the vent hole 5, the intervening layer 7 is deformed along the uneven shape while being cut or compressed at the time of insertion. Rather than observing the Rockwell hardness, Vickers hardness, Brinell hardness, etc., and the amount of dents, the hardness should be expressed with an index indicating the ease of cutting, and is generally a general index Hardness is evaluated by different Mohs hardness.

  The intervening layer 7 has a thickness of 500 μm or less. By setting the thickness to 500 μm or less, the deformation of the intervening layer 7 can easily follow the surface properties of the vent hole 5 and the vent piece 6. When the thickness of the intervening layer 7 is larger than 500 μm, the internal stress of the intervening layer 7 tends to increase, and elastic deformation becomes dominant, so that it is difficult to obtain plastic deformation corresponding to a minute uneven shape. It is difficult to secure an actual contact area at the interface 56. Moreover, it is preferable that the thickness of the intervening layer 7 is 100 micrometers or more. When the thickness is less than 100 μm, the deformation margin of the intervening layer 7 is small, and it becomes difficult to appropriately cope with the uneven shape.

  FIG. 3 is an enlarged cross-sectional view of the vent piece 6. The intervening layer 7 is preferably laminated on the outer surface of the vent piece 6 by coating or plating such as spraying or vapor deposition. The intervening layer 7 may be formed at least on a portion of the outer surface of the vent piece 6 that is in contact with the vent hole 5. By inserting the vent piece 6 into the vent hole 5 with the intervening layer 7 formed on the outer surface, the intervening layer 7 can be easily interposed at the interface 56 between the vent hole 5 and the vent piece 6. The intervening layer 7 is preferably laminated and formed uniformly on the outer surface of the vent piece 6 without a gap. Thereby, the intervening layer 7 having a uniform thickness can be interposed in the entire interface 56 between the vent hole 5 and the vent piece 6. In addition, as for the thickness of the interposition layer 7 formed by lamination, 500 micrometers or less are preferable.

  The tire vulcanization mold of the present invention is a normal tire vulcanization mold except that a vent piece as described above is fitted into a vent hole provided on a tire molding surface, and an intervening layer is interposed at the interface between the two. Any of known shapes, materials, and opening / closing mechanisms can be employed in the present invention. In the above-described embodiment, a mold structure having a tread mold part and a pair of side mold parts has been shown. However, in the present invention, a mold that has a dividing surface at the center part of the tread mold part and is divided into two parts up and down. A mold structure may be used.

<Another embodiment>
(1) In the above-described embodiment, the intervening layer 7 is formed on the outer surface of the vent piece 6. However, the intervening layer 7 is laminated on the inner wall of the vent hole 5 by coating or plating such as spraying or vapor deposition. May be.

  (2) The intervening layer 7 may be in the form of a paste. The interface between the vent hole 5 and the vent piece 6 is obtained by inserting the vent piece 6 into the vent hole 5 with the paste-like intervening layer 7 applied to the inner wall of the vent hole 5 and / or the outer surface of the vent piece 6. The intervening layer 7 can be easily interposed in 56. The paste-like intervening layer 7 preferably has a viscosity measured by a B-type viscometer at 25 ° C. of 10,000 mPa · s or more in consideration of the workability during application and insertion of the vent piece 6.

  At this time, the intervening layer 7 is preferably made of an epoxy resin adhesive in which a powder of a metal material is kneaded. Examples of the metal material powder include aluminum nitride and magnesium oxide powders having a particle diameter of 10 μm or less. Aluminum nitride itself has a Mohs hardness of about 7 and is very hard. However, since the main intervening layer 7 is an epoxy resin adhesive, the particle size may be small or hard.

  When the intervening layer 7 is made into a paste, it is preferable that the hole diameter of the vent hole 5 is 200 to 400 μm larger than the outer diameter D1 of the vent piece 6. According to this, the intervening layer 7 is effectively removed at the interface between the vent hole 5 and the vent piece 6 without being scraped off when the vent piece 6 is inserted, together with the viscosity of the paste intervening layer 7. It is possible to intervene. Furthermore, since there is a gap between the vent hole 5 and the vent piece 6, deformation of the vent piece 6 can be suppressed during insertion. In addition, by including metal fine particles in the adhesive, which is a non-thermal conductor, it is possible to insert the vent piece 6 without damaging the heat conduction without destroying it, and to effectively reduce the length of the spew. It becomes.

  In order to specifically show the configuration and effects of the present invention, the vulcanization molding of the tire was performed by changing the material of the mold body, the material and outer diameter of the vent piece, and the thickness of the intervening layer, and the length of the spew generated evaluated. Moreover, the bending of the vent piece when fitted in the vent hole was evaluated. Note that the tire size, rubber composition, and vulcanization conditions to be evaluated are standardized in each example. The evaluation results are shown in Table 1.

  The material of the mold body was an aluminum alloy casting (AC7A) or a general structural rolled steel (SS400). The material of the vent piece was stainless steel (SUS301), pure aluminum (A1050), high-strength aluminum (A5052), or carbon steel material for machine structure (S45C). The material of the intervening layer was zinc. In each example, the inner diameter of the vent piece was 0.6 mm, the outer diameter was 1.0 to 4.0 mm, and the total length was 10 mm.

  From Table 1, it can be seen that in Examples 1 and 2, the length of the spew is reduced as compared with Comparative Example 2. The length of the spew is also reduced in Comparative Example 1 compared to Comparative Example 2, but the removal of the air layer is insufficient because the thickness of the intervening layer is too large. Long. In Examples 3 to 5, the spew length is suppressed to be equal to that in Examples 1 and 2. Moreover, in Examples 1-5, the bent of the vent piece did not occur, but when the vent piece was formed of A1050 and A5052 as in Comparative Examples 3-6, the bent piece was bent. Moreover, when the outer diameter of the vent piece was made smaller than twice the inner diameter as in Comparative Example 7, the bent piece was bent.

1a Tire molding surface 5 Vent hole 6 Vent piece 7 Intervening layer 56 Interface

Claims (5)

In the tire vulcanization mold provided with a vent hole for discharging air between the outer surface of the tire and the tire molding surface during vulcanization molding on the tire molding surface for molding the outer surface of the tire,
A cylindrical vent piece made of an iron-based material is inserted into the vent hole,
A tire vulcanization mold characterized in that an intervening layer made of a material softer than the mold body and the vent piece and having a thickness of 500 μm or less is interposed at an interface between the vent hole and the vent piece.   2. The tire vulcanization mold according to claim 1, wherein the intervening layer is made of a material having higher thermal conductivity than the mold body or the vent piece.   The tire vulcanization mold according to claim 1 or 2, wherein the intervening layer is laminated and formed on the inner wall of the vent hole or the outer surface of the vent piece by coating or plating.   The tire vulcanization mold according to claim 1 or 2, wherein the intervening layer is a paste having a viscosity measured by a B-type viscometer at 25 ° C of 10,000 mPa · s or more. The tire vulcanization mold according to claim 4, wherein the intervening layer is made of an epoxy resin adhesive in which a powder of a metal material is kneaded.

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