JP2016124148A - Die for tire molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die for tire molding, in which a bent piece is hardly deformed when hammering the bent piece to a lower hole.SOLUTION: A lower hole 22 comprises a large diameter part 221 which has a large diameter on an inside part of a die body 2, and a small diameter part 222 which has a small diameter relative to the diameter of the large diameter part 221 on an outside part of the die body, and comprises a step 223 on a boundary between the large diameter part 221 and the small diameter part 222. A bent piece 3 has hardness higher than that of the part where the lower hole 22 of the die body 2 is formed, and has a taper part 32 whose diameter becomes smaller as going to outside on the die body 2, on a position that matches to the step 223 when the bent piece is embedded in the lower hole 22.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a tire mold.

  In a tire molding die used when manufacturing a tire, a plurality of vent holes are provided on a tire molding surface for molding the outer surface of the tire. This vent hole allows the inside and outside of the mold to communicate with each other. When molding a tire, the air located between the outer surface of the tire and the tire molding surface is exhausted outside the mold. This prevents the formation of defective molding parts that are not filled with rubber.

  In the mold described in Patent Document 1, in order to form a vent hole, a cylindrical vent piece made of copper or aluminum is embedded in a pilot hole formed through the main body of the mold. In the mold of Patent Document 1, the vent piece is formed of a material having a higher thermal conductivity than that of an iron-based material. For this reason, at the time of tire molding, vulcanization can be accelerated by quickly transferring heat from the mold to the rubber that has flowed into the vent hole, and the fluidity of the rubber in the vent hole can be reduced. Therefore, the vent (also referred to as “beard”) protruding from the surface of the tire after molding does not become too long and can be formed with an appropriate length.

  In the mold of Patent Document 1, in order to prevent the vent piece from being displaced (sinked) in the axial direction with respect to the pilot hole due to the pressure of rubber applied at the time of tire molding, the inner diameter of the pilot hole is set. On the other hand, it was inserted by hitting a vent piece having a large outer diameter. However, since a relatively large diameter vent piece is struck into a small diameter pilot hole, the vent piece may be deformed by the struck force. When the vent piece is deformed, deformation such as bending or squeezing occurs in the through hole (hole that becomes the vent hole when the vent piece is embedded in the pilot hole) that passes through the vent piece in the axial direction for air discharge, The vent formed at the time of tire molding may be cut off at the time of mold release, resulting in uneven length, or the drill blade may break when cleaning through the through hole of the vent piece after molding through the drill blade .

JP 2009-292012 A

  Then, this invention makes it a subject to provide the metal mold | die for tire shaping | molding in which a vent piece is hard to deform | transform when hitting a vent piece with respect to a pilot hole.

  The present invention forms a plurality of vent holes on the tire molding surface for molding the outer surface of the tire, for discharging air located between the outer surface of the tire and the tire molding surface during molding to the outside of the mold. A mold body provided with a plurality of pilot holes and a vent piece embedded in each pilot hole of the mold body and having a through hole penetrating in the axial direction. The mold body has a large-diameter portion having a large diameter at an inner portion thereof, and an outer portion has a small-diameter portion having a small diameter with respect to the large-diameter portion. It is a hole having a step at the boundary, the vent piece is harder than the portion of the mold body where the pilot hole is formed, and in the portion that matches the step when embedded in the pilot hole, It has a taper part which becomes a small diameter as it goes to the outside in the mold body. A tire mold, characterized.

  According to this configuration, when the vent piece is struck from the inside to the outside of the mold body from the inside to the outside, the step of the pilot hole is compressed by the taper portion of the vent piece, so that the vent piece is against the pilot hole. Can be fixed. And since the hardness of a vent piece is larger than the hardness of a metal mold body, the vent piece is not easily deformed even when it is struck when the vent piece is inserted into the prepared hole. Moreover, since the tapered portion of the vent piece is in contact with the small diameter portion of the pilot hole in the embedded state, the vent piece is displaced to the outside of the mold body from the above state due to the pressure of rubber applied at the time of tire molding. (Sinking) can be prevented. For this reason, it is not necessary to set the inner diameter of the pilot hole too small with respect to the outer diameter of the vent piece in order to prevent the depression, so that the vent piece is also difficult to deform from this point.

  Further, the vent piece has a cylindrical portion having a constant diameter in the axial direction at a position adjacent to the inside of the die body of the tapered portion when embedded in the pilot hole, and the outer diameter of the cylindrical portion. Is larger than the inner diameter of the large-diameter portion of the pilot hole, and the cylindrical portion can be press-fitted into the large-diameter portion when the vent piece is inserted into the pilot hole.

  According to this configuration, the vent piece can be firmly fixed to the cylindrical portion in addition to the tapered portion by press-fitting the cylindrical portion of the vent piece into the large-diameter portion. It is possible to effectively prevent the piece from falling out of the pilot hole or sinking.

  The diameter of the tapered portion is 1.3 to 3.3 mm at the proximal end on the cylindrical portion side, and 0.7 to 2.7 mm at the distal end. The inclination of the tapered portion is 1 with respect to the axial direction. -10 °.

  According to this structure, the taper part of a vent piece and the level | step difference in a pilot hole can be made into appropriate dimensional relationship. For this reason, it is possible to achieve both ease of hitting the vent piece into the prepared hole and reliable fixation.

  The inner diameter of the through hole in the vent piece may be 0.2 to 1.5 mm.

  According to this configuration, a vent having an appropriate thickness can be formed on the surface of the tire.

  In the present invention, a plurality of vent holes are formed in the tire molding surface for molding the outer surface of the tire to discharge air located between the outer surface of the tire and the tire molding surface to the outside of the mold during molding. In the tire molding die, comprising: a mold body provided with a plurality of pilot holes for use; and a vent piece embedded in each pilot hole of the mold body and having a through hole extending in the axial direction. Is a tire molding die characterized in that it has a hardness higher than that of a drill blade used when removing deposits adhering to the through hole after using the die.

  According to this structure, the deposit | attachment adhering to a through-hole can be removed, without the inner surface of a through-hole being scraped off at the time of the cleaning after metal mold | die use.

  Further, the mold body has a hardness smaller than that of a drill blade used when removing deposits attached to the through hole in a portion where the vent piece is embedded, and the vent piece is smaller than the drill blade. Hardness can be increased.

  According to this structure, the deposit | attachment adhering to a through-hole can be removed, without the inner surface of a through-hole being scraped off at the time of the cleaning after metal mold | die use.

  The vent piece may be made of a metal containing nickel.

  According to this configuration, a vent piece that is not easily deformed even by being struck can be formed of a general-purpose material called nickel.

  According to the present invention, the vent piece is not easily deformed even by being struck when the vent piece is inserted into the prepared hole. For this reason, it is possible to provide a tire molding die in which the vent piece is not easily deformed when the vent piece is struck into the prepared hole.

It is sectional drawing of radial direction view which shows the metal mold | die for tire shaping | molding which concerns on one Embodiment of this invention. It is a longitudinal cross-sectional view of the vent piece in the tire mold according to the present embodiment. It is a longitudinal cross-sectional view which shows the state which buried the vent piece in the pilot hole in the tire shaping die of this embodiment. It is a longitudinal cross-sectional view which shows the shape of the pilot hole and vent piece which were used for performance evaluation, (A) is Example 1, (B) is Example 2, (C) is Comparative Example 1, (D) is a comparative example. 2 and (E) show Comparative Example 3.

  Next, the present invention will be described by taking up a tire mold according to an embodiment (hereinafter simply referred to as “mold”).

  The type of the mold 1 of the present embodiment is classified as “segmented mold”. As shown in FIG. 1 (hatching is omitted for the sake of illustration), the mold 1 includes a plurality of sectors 1a arranged in the circumferential direction when molding a tire and a pair of sectors arranged on both sides of the sector 1a during molding. Side plate 1b. A tire molding surface 21 for molding the outer surface of the tire is formed on the inner surfaces of the sector 1a and the side plate 1b. The tire molding surface 21 has irregularities for forming tire ribs, grooves, patterns, and the like. Is formed. The sector 1a forms a tread portion and a shoulder portion of the tire, and the side plate 1b forms a tire side portion and a bead portion.

  In using the mold 1, the sector 1a and the side plate 1b are assembled so as to wrap the annular unvulcanized tire (green tire), and the green tire is expanded and heated from the inside of the diameter. As a result, the rubber composing the green tire is vulcanized. This rubber is pressed against the tire molding surface 21 to form ribs, grooves, patterns and the like on the outer surface of the tire. Thereafter, the molded tire is taken out by separating the sector 1a and the side plate 1b.

  The mold 1 (both the sector 1a and the side plate 1b in the present embodiment) has a plurality of vents for discharging air located between the outer surface of the tire and the tire molding surface 21 to the outside of the mold during molding. As shown in FIG. 3, the mold body 2 provided with a plurality of pilot holes 22 for forming the holes 33, and embedded in each pilot hole 22 of the mold body 2, which is an embedded base material, Is provided with a vent piece 3 penetrating in the axial direction. The mold body 2 is formed by using, for example, structural steel (SS400 or the like) as a base material and using cast iron or an aluminum alloy at least on the tire molding surface 21. In the mold body 2 of the present embodiment, the sector 1a portion is made of an aluminum alloy, and the side plate 1b portion is made of SS400.

  As shown in FIG. 1, the pilot hole 22 extends through the mold body 2 across the sector 1 a and the side plate 1 b, and is provided in a direction perpendicular to the tire molding surface 21 (radial direction). Here, when the vent piece 3 is formed of a material having a hardness higher than that of a conventional material (stainless alloy or the like) such as pure nickel of the present embodiment, the base end surface 3a of the vent piece 3 is replaced with the conventional vent piece. As described in the above, it is possible to perform the cutting process according to the shape of the tire molding surface 21 (specifically, the inclination of the tire molding surface 21 with respect to the axial direction of the pilot hole 22 at the opening end of the pilot hole 22). It is very difficult. For this reason, in this embodiment, even if it is a case where cutting is not performed, compared with the case where the pilot hole 22 is formed along the radial direction and the axial direction with respect to the mold body 2, the tire molding surface 21 and the vent are formed. The angle difference with the base end surface 3a of the piece 3 can be made small, and it can suppress impairing the beauty | look of the vent which protrudes from the tire surface after shaping | molding.

  As shown in FIG. 3, the pilot hole 22 of the present embodiment has a large-diameter portion 221 having a large diameter at the inner portion of the mold main body 2, and a small diameter with respect to the large-diameter portion 221 at the outer portion. The hole has a small-diameter portion 222 and has a step 223 at the boundary between the large-diameter portion 221 and the small-diameter portion 222, and penetrates into and out of the mold body 2.

  The vent piece 3 has a pilot hole 22 so that the base end side is located on the tire molding surface 21 side (inside in the mold body 2) and the distal end side is located on the side away from the tire molding surface 21 (outside in the mold body 2). Inserted into. This insertion is made by hitting the vent piece 3 into the pilot hole 22 from the tire molding surface 21 side using a striking tool. In a state where the vent piece 3 is embedded in the mold body 2, the through hole 33 of the vent piece 3 becomes a vent hole in the mold 1. In this way, by inserting the vent piece 3 that is a separate body into the mold body 2 into the pilot hole 22 of the mold body 2, the inner diameter is small compared to drilling directly into the mold body 2. A vent hole can be easily formed in the mold 1.

  As shown in FIG. 2, the vent piece 3 has a proximal end side as a cylindrical portion 31 and a distal end side as a tapered portion 32. The cylindrical portion 31 and the tapered portion 32 are adjacent to each other. And the through-hole 33 has penetrated along the axial direction in the center of a cross section. The base end side of the through hole 33 is a tapered hole 331 whose inner diameter increases toward the base end. A rubber projecting from the tire surface is formed by the rubber during molding entering the through hole 33.

  The vent piece 3 of the present embodiment is made of pure nickel and is formed by casting. For this reason, the vent piece 3 which consists of a hard material which cannot change easily even if it strikes can be formed with a general purpose material called nickel.

  The vent piece 3 has a Vickers hardness (HV) of about 1000. Conventionally, since the hardness of a stainless alloy that has been generally used as a material for the vent piece 3 is about 200, the vent piece 3 of this embodiment has a relatively high hardness. In addition, the material which comprises the metal mold | die main body 2 is Vickers hardness (HV), and is 160-180 in the case of cast iron, and 45-100 in the case of an aluminum alloy. For this reason, the vent piece 3 of the present embodiment is sufficiently harder than the portion where the pilot hole 22 of the mold body 2 is formed. Therefore, when the vent piece 3 is struck into the prepared hole 22 due to the high hardness, it is possible to suppress the bent piece 3 from being deformed such as bending. Accordingly, deformation of the through-hole 33 provided in the vent piece 3 can be prevented from being deformed, so that the tire vent can be formed beautifully, and the cleaning drill blade D (see FIG. 3) used after the mold 1 is used. Breakage can also be suppressed. When the vent piece 3 is made of a material other than pure nickel, it is preferable that the hardness of the vent piece 3 is not less than three times the hardness of the mold body 2 (the portion where the pilot hole 22 is formed).

  Incidentally, the thermal conductivity of pure nickel is 94 W / (m · K), which is larger than the thermal conductivity of stainless steel (SUS303) 17 W / (m · K). For this reason, at the time of molding, vulcanization can be promoted by rapidly transferring heat to the rubber flowing into the through hole (vent hole) 33 from the inside of the mold, and the fluidity of the rubber can be reduced. For this reason, it can suppress that the vent of the tire after shaping | molding becomes unnecessarily long, or rubber | gum jumps out from the through-hole (vent hole) 33. FIG.

  When the vent piece 3 is embedded in the pilot hole 22, the taper portion 32 is formed in a portion that coincides with the step 223 as shown in FIG. 3, and has a shape that decreases in diameter toward the tip. The taper portion 32 of the present embodiment has a vertical cross-sectional shape that is linear, but is not limited thereto, and may be a curved shape. The cylindrical portion 31 is positioned so as to be closer to the tire molding surface 21 side (inner side in the mold body 2) than the tapered portion 32 when the vent piece 3 is embedded in the prepared hole 22, and has a constant diameter in the axial direction. It is the shape. The outer diameter portion of the cylindrical portion 31 is larger than the inner diameter of the large diameter portion 221 of the prepared hole 22. For this reason, the vent piece 3 is press-fitted into the prepared hole 22 at the time of insertion. However, since sufficient fixing strength can be exhibited by the step 223 and the tapered portion 32, the difference in the outer diameter of the cylindrical portion 31 with respect to the inner diameter of the large-diameter portion 221 of the pilot hole 22 is reduced compared to the conventional vent piece. (In this embodiment, it is 0.01 to 0.02 mm). For this reason, when inserting the vent piece 3 in the pilot hole 22, the resistance which the vent piece 3 receives can be made small, and the deformation | transformation of the vent piece 3 by the hammering at the time of insertion can be suppressed.

  The diameter of the tapered portion 32 is (d32a) 1.3 to 3.3 mm at the proximal end and (d32b) 0.7 to 2.7 mm at the distal end, and the inclination angle θ32 of the tapered portion 32 is 1 to 3 with respect to the axial direction. 10 ° is preferable. And it is preferable that the diameter d31 of the cylindrical part 31 is 1.3-3.3 mm. The inner diameter d221 of the large diameter portion 221 in the pilot hole 22 is preferably 0.01 to 0.02 mm smaller than the diameter d31 of the cylindrical portion 31, and the inner diameter d222 of the small diameter portion 222 in the pilot hole 22 is The diameter is preferably 0.4 to 0.6 mm smaller than the diameter d31 of the cylindrical portion 31 of the vent piece 3. Further, the ratio of the length of the cylindrical portion 31 to the entire length of the vent piece 3 is preferably 15% or more and 80% or less, and more preferably 25% or more and 65% or less. By adopting such a dimensional relationship, it is possible to achieve both ease of hitting the vent piece 3 into the pilot hole 22 and reliable fixation. The inner diameter of the through hole 33 is 0.2 to 1.5 mm. Thereby, a vent having an appropriate thickness can be formed on the surface of the tire.

  As the vent piece 3 is inserted into the lower hole 22, first, the tapered portion 32 of the vent piece 3 contacts the step 223 of the lower hole 22. In this state, when the vent piece 3 is struck toward the back side, that is, toward the outside of the mold body 2, the mold body 2 is harder (softer) than the vent piece 3, so that the step 223 is compressed. Deform. By the step 223 deformed in this way, the tapered portion 32 of the vent piece 3 is pressed radially inward over the entire circumference. For this reason, the vent piece 3 is securely fixed to the prepared hole 22. In addition, since the hardness of the mold body 2 is smaller than the hardness of the vent piece 3, the vent piece 3 is not easily deformed by the impact of the hit. Moreover, since the tapered portion 32 of the vent piece 3 is in contact with the small-diameter portion 222 of the pilot hole 22 in the embedded state, the vent piece 3 is made of gold more than the above state due to the pressure of rubber pressurized at the time of tire molding. It is possible to prevent the position of the mold body 2 from being displaced (recessed). For this reason, it is not necessary to set the inner diameter of the pilot hole 22 so small (excessively) with respect to the outer diameter of the vent piece 3 in order to prevent the vent piece 3 from sinking. The deformation that occurs when the vent piece 3 is inserted can be suppressed.

  Here, in order to remove deposits made of carbon or the like deposited from the rubber during vulcanization and adhered to the through-holes 33 after the molding of the tire, as shown in FIG. 33 is inserted. If the inner surface of the through-hole 33 is partially expanded by the drill blade D, inconveniences such as the tire vent being cut at the time of mold release at the next molding occur. Thus, since the drill blade D is used for cleaning, it is preferable that the vent piece 3 has higher hardness than the drill blade D. The drill blade D has a Vickers hardness (HV) of 750 or less when high-speed steel is used. On the other hand, the vent piece 3 of the present embodiment has a Vickers hardness (HV) of about 1000, which is higher than that of the high-speed steel. For this reason, even if the drill blade D is inserted into the through hole 33 at the time of cleaning, the inner surface of the through hole 33 is not scraped by the drill blade D, and deposits attached to the through hole 33 can be effectively removed.

  Next, since the inventor of the present application prototyped the molds 1A to 1E shown in FIGS. 4A to 4E and performed performance evaluation, the evaluation will be described.

  A mold 1A related to the combination of the pilot hole 22 and the vent piece 3 (3A) of the above-described embodiment of the five types of prototype molds 1A to 1E is referred to as Example 1 (see FIG. 4A). The mold 1B of Example 2 is an example in which the contact length of the vent piece 3B with respect to the pilot hole 22 (ratio of the length of the cylindrical portion 31 to the entire length of the vent piece 3) is 80% (50% in Example 1). (See FIG. 4B). A mold 1C of Comparative Example 1 is a vent piece 3C made of a stainless alloy, and the contact length is 50%, and the taper portion 32C is not in contact with the step 223 of the prepared hole 22 (FIG. 4C). reference). The mold 1D of Comparative Example 2 is a vent piece 3D made of a stainless alloy, the contact length is 50%, and the taper portion 32D is in contact with the step 223 of the prepared hole 22 (FIG. 4D). reference). The mold 1E of Comparative Example 3 is a pure nickel vent piece 3, the contact length is 80%, the step hole 223 is not formed with the step 223, and the tapered portion 32E is formed in the hole 22E. This is an example of no contact (see FIG. 4E).

  For the five types of molds 1A to 1E, the deformation of the vent pieces 3A to 3E at the time of hitting the pilot holes 22 and 22E was evaluated as the first (evaluation 1). The numerical value of evaluation is a relative numerical value based on Comparative Example 1 as a reference (100), and the higher the numerical value, the better the evaluation (the same applies hereinafter).

  Further, in the second (evaluation 2), vulcanization is performed in a state where the vent piece 3 is embedded so that the tire molding surfaces 21 of the molds 1A to 1E and the base end surfaces of the vent pieces 3A to 3E are flush with each other. The vent pieces 3 </ b> A to 3 </ b> E were repeatedly pressed with a load corresponding to the internal pressure, and the amount of depression of the vent pieces 3 </ b> A to 3 </ b> E with respect to the pilot hole 22 was evaluated.

  Moreover, the deformation | transformation of the opening hole diameter of the pilot holes 22 and 22E by hitting the vent pieces 3A-3E to the pilot hole 22 was evaluated to the 3rd (evaluation 3) ("Ease of protrusion" in Table 1). .

Table 1 shows a summary of each evaluation.

  From Table 1, it has confirmed that Example 1 and 2 was comprehensively superior to Comparative Examples 1-3. Therefore, the superiority of the mold according to the present invention was confirmed. It was also confirmed that Example 1 was superior to Example 2 for Evaluation 3. This is presumed to be because the contact length is short (30%), and the length of the force that pushes the pilot hole 22 when the vent piece 3 (3A) is struck is shortened.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the summary of this invention.

  For example, the type of the mold 1 of the embodiment is “segmented mold”. However, the application target of the present invention is not limited to this, and can be applied to a “two-piece mold” mold in which parts divided in the tire width direction are combined.

  In addition, the vent piece 3 of the above embodiment is made of pure nickel, but various materials can be used as long as the hardness is higher than a material (such as a stainless steel alloy) conventionally used for the vent piece. Therefore, it may be made of a metal containing nickel such as nickel alloy instead of pure nickel. In addition, it is preferable to use a material larger in thermal conductivity than a conventional material.

DESCRIPTION OF SYMBOLS 1 Tire shaping | molding die 2 Mold body 21 Tire shaping | molding surface 22 Pilot hole 221 Large diameter part 222 Small diameter part 223 Step 3 Vent piece 31 Cylindrical part 32 Tapered part 33 Through hole, Vent hole (in mold) D Drill blade

Claims (7)

A plurality of lower holes for forming a plurality of vent holes for discharging air located between the outer surface of the tire and the tire molding surface to the outside of the mold during molding on the tire molding surface for molding the outer surface of the tire In a mold for molding a tire comprising a mold body provided with a hole, and a vent piece embedded in each pilot hole of the mold body and having a through hole penetrating in the axial direction,
The pilot hole has a large-diameter portion having a large diameter at an inner portion of the mold body, and has a small-diameter portion having a small diameter with respect to the large-diameter portion at an outer portion, It is a hole with a step at the boundary with the small diameter part,
The vent piece is harder than the portion of the mold body where the pilot hole is formed, and the portion of the vent piece that coincides with the step when embedded in the pilot hole moves toward the outside of the mold body. A tire molding die having a tapered portion having a small diameter. The vent piece has a cylindrical portion having a constant diameter in the axial direction at a position adjacent to the inside of the die body of the tapered portion when embedded in the pilot hole,
The outer diameter of the cylindrical portion is larger than the inner diameter of the large diameter portion of the pilot hole,
2. The tire molding die according to claim 1, wherein the cylindrical portion is press-fitted into the large-diameter portion when the vent piece is inserted into the pilot hole.   The diameter of the tapered portion is 1.3 to 3.3 mm at the proximal end on the cylindrical portion side, and 0.7 to 2.7 mm at the distal end, and the inclination of the tapered portion is 1 to 10 with respect to the axial direction. The tire mold according to claim 2, wherein the mold is a tire.   The tire molding die according to any one of claims 1 to 3, wherein an inner diameter of the through hole in the vent piece is 0.2 to 1.5 mm. A plurality of lower holes for forming a plurality of vent holes for discharging air located between the outer surface of the tire and the tire molding surface to the outside of the mold during molding on the tire molding surface for molding the outer surface of the tire In a mold for molding a tire comprising a mold body provided with a hole, and a vent piece embedded in each pilot hole of the mold body and having a through hole penetrating in the axial direction,
The tire molding die according to claim 1, wherein the vent piece has a hardness higher than that of a drill blade used when removing deposits attached to the through hole after the die is used. The mold body has a hardness smaller than that of a drill blade used when removing deposits attached to the through hole in the portion where the vent piece is embedded,
The tire molding die according to claim 1 or 5, wherein the vent piece has a hardness higher than that of the drill blade.   The tire molding die according to claim 1 or 5, wherein the vent piece is made of a metal containing nickel.

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