JP2011212966A - Production process of tire mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production process of a tire mold, capable of abbreviating production steps, suppressing generation of a casting defect of the mold and improving dimensional accuracy of the mold obtained, in producing the tire mold by a casting production process using a transfer method.SOLUTION: The tire mold 18 having a blade is produced by: transfer forming a rubber mold 13 from a prototype 11 that has a tire tread shape; forming a degradable cast mold 14 by casting a degradable cast mold material without attaching a sipe molding blade 15 in the rubber mold 13; putting the blade 15 in the molded degradable cast mold 14; and performing the casting by using the degradable cast mold 14 after putting the blade in.

Description

  The present invention relates to a method for manufacturing a tire molding die. More specifically, the present invention relates to a manufacturing method for casting a tire molding die in which a blade for forming a sipe of a tire is cast.

  The tire molding die is a die that is used when a non-vulcanized rubber is accommodated in the die and vulcanized to produce a pneumatic tire. This tire molding die generally has an assembly structure of mold parts divided into a plurality of parts. The mold division structure includes a two-piece mold in which the tread portion of the tire is divided into two at the center in the width direction, and the tire. There are two types: sectional molds divided into 7 to 13 in the circumferential direction. In both the two-piece mold and the sectional mold, the tire mold has a complicated shape (design surface) corresponding to the tread portion of the tire to be molded, and the tire to be molded is a thin shape called a sipe. When the groove is provided in the tread portion, a high-strength thin member called a blade is fitted into the design surface of the mold to form the sipe, so that it has a protruding shape. It is often manufactured by a casting method using a transfer method.

  In the casting method using this transfer method, a tire prototype to be molded with a tire mold is produced, the tread portion of this prototype is transferred to a rubber mold, and the design surface transferred to this rubber mold is used for tire molding. The mold is transferred to a mold for casting, a molten metal is poured into the mold and solidified, and a tire molding mold as a casting is manufactured by casting. According to this casting manufacturing method, a tire-shaped prototype is manufactured by machining, and since a casting transfer manufacturing method is adopted throughout a process from casting a rubber mold to a casting through a mold, a tire molding mold is used. It is difficult to manufacture by machining, the pin angle corner part of the design surface and the R shape of the protrusion shape part can be formed, and the blade is cast into the tire molding die at the time of casting, It can be easily formed on the design surface of the mold.

  The blade needs to be formed at a predetermined protruding height at a predetermined position on the design surface of the tire molding die. Therefore, the conventional casting method using the transfer method described above includes the following steps. A prototype blade is attached and fixed at a position where a sipe is formed in the prototype, with or without forming a slit corresponding to the sipe. Next, transfer to a rubber mold is performed. Thereby, a slit formed by the prototype blade is formed on the mold surface of the rubber mold. Next, a mold blade is attached to the rubber mold slit, and one end of the mold blade is buried in the rubber mold slit at a predetermined depth, and the other end is sipe from the rubber mold surface to the tire sipe. Make sure that it protrudes with the same length as the depth. In this state, a mold for a tire mold is produced by a casting method using a rubber mold. This mold is made of a collapsible mold such as gypsum, for example. During casting, a slurry containing gypsum is poured into a rubber mold to cure the mold. When the cured mold is removed from the rubber mold, the mold blade leaves the rubber mold, is embedded in the mold surface of the mold at the same depth as the sipe of the tire, and is attached to protrude at a predetermined height. Is done. After performing mold finishing such as removing casting burrs generated around the mold blade formed on the mold, the mold is dried and fired to complete a mold for a tire molding mold. When the mold for tire molding is cast using the completed mold and the mold is collapsed after casting, the mold blade attached to the surface of the mold is the design surface of the cast tire mold It protrudes at a predetermined position at a length substantially the same as the sipe depth of the tire.

  When manufacturing a tire casting mold having a blade by a casting method using such a transfer method, the following problems (1) to (5) may occur.

(1) It is often difficult to machine a slit having a depth equivalent to a sipe for attaching a blade to a prototype, especially when the blade has a shape with an undercut. Met. If a prototype blade with a depth shallower than that of a sipe is formed in this prototype, or if a prototype blade is attached without forming any slit, the processing is somewhat easier than when a slit with a depth equivalent to a sipe is formed. However, in this case, it is necessary to separately prepare a prototype blade having a shape different from that of the mold blade. In addition, when no slit is formed at all, it is difficult to perform positioning when the blade is stuck and fixed on the prototype, and a gap between the prototype and the blade is likely to be generated due to a defective shape of the prototype blade.

(2) Since the rubber material shrinks in the rubber transfer process, when the mold blade is installed in the blade slit on the rubber mold, interference between the blade and the rubber is likely to occur, and the rubber mold deformation and dimensional accuracy are improved. Problems are likely to occur.

(3) As a result of the mold material entering the gap between the blade and rubber in the transfer process to the mold, casting burrs are likely to occur, and it takes time and effort to remove the burrs by mold finishing.

(4) In the step of transferring to the mold, when the mold is removed from the rubber mold, a mold defect may occur due to an undercut of the blade embedded on the rubber mold side.

(5) The mold is likely to break due to thermal expansion of the mold blade in the mold drying and casting process, and as a result, steps and depression defects are likely to occur around the blade of the cast tire molding mold.

  The following conventional techniques have been proposed for a method of manufacturing a mold for molding a tire that has improved these problems. Regarding the interference between the blade and the rubber due to the contraction of the rubber material in the above (2), there is a production method using a size of the original blade that is proportionally enlarged by the contraction between the mold blade and the rubber material ( Patent Document 1). As for the gypsum cast burr near the blade in (3), there is a manufacturing method using a blade in which a notch or a concave groove is formed in advance in a portion where the cast burr is generated (Patent Documents 2 and 3). Regarding the mold defect of (4) above, there is a manufacturing method in which a reinforcing material is embedded in a gypsum mold material near the blade (Patent Document 4). Regarding the mold breakage of (5) above, there is a production method in which the area ratio of the portion of the blade cast into the mold is in the range of 10 to 40%, and the remaining area ratio is embedded in the gypsum mold ( Patent Document 5).

JP 2006-103079 A JP 2005-169929 A JP 2005-169660 A JP-A-11-170267 JP 2004-17346 A

  Each of the prior art documents listed above solves any one of the above-mentioned problems in the casting method using the transfer method, and cannot solve all of the problems at once, and each technology However, another problem sometimes occurred. For example, in the technique of Patent Document 1, it is necessary to separately prepare a prototype blade having a dimension different from that of the mold blade. The technique of Patent Document 2 and the technique of Patent Document 3 require time and effort to form notches and constrictions in the blade, and the formation of the notches and constrictions causes a decrease in the breaking strength of the blade, resulting in a decrease in blade life. Was. The technique of Patent Document 4 requires time and effort to embed a reinforcing material only for reinforcement. The technique of Patent Document 5 requires a process of cutting off a part of the shape of the blade to be cast in order to adapt the area ratio, and in this blade shape, the area of the portion to be cast is reduced. As a result, the cast-in-place fixing force of the blade to the mold body has been reduced.

  In addition, among the above-mentioned problems, the problems such as the difficulty in processing the original mold (1) and the difficulty in positioning the original blade cannot be solved by the prior art documents listed above. There was a problem with the dimensional accuracy in the vicinity.

  The present invention advantageously solves the above problem, and in the casting method using the transfer method of the tire molding die, the manufacturing process can be omitted, and the occurrence of casting defects in the die can be suppressed and further obtained. It aims at providing the manufacturing method of the metal mold | die for tire molding which can raise the dimensional accuracy of a metal mold | die.

  The method for producing a tire molding die according to the present invention includes transferring a rubber mold from an original mold having a tire tread shape, and casting a collapsible mold material without attaching a sipe forming blade to the rubber mold. A collapsible mold is molded, a blade is implanted in the collapsible mold after molding, and casting is performed using the collapsible mold after implantation, thereby manufacturing a tire molding die having a blade.

  The method for manufacturing a tire molding die according to the present invention includes forming a groove at a position where a blade is attached in the original mold, transferring the groove from the original mold through a rubber mold onto a collapsible mold, and using the groove as a guide. Blades can be implanted.

  In the method for manufacturing a mold for molding a tire according to the present invention, a foamed mold material is preferably used as the collapsible mold material.

  Moreover, the manufacturing method of the tire molding die of the present invention can be implanted in a state where the blade is elastically deformed when the blade is implanted in the mold.

  According to the method for manufacturing a tire molding die of the present invention, a collapsible mold is molded without attaching a sipe forming blade to the rubber mold, and the blade is implanted in the collapsible mold after molding. The process of attaching the blade to the rubber mold can be omitted, and the casting defects and the deterioration of the dimensional accuracy of the mold derived from the process of attaching the blade to the rubber mold can be suppressed.

It is typical explanatory drawing of the manufacturing process of the tire mold which applied the manufacturing method of this embodiment. It is a schematic diagram explaining the implantation work of the blade for metal mold | die with respect to a collapsible mold. It is typical explanatory drawing of the process from preparation of a prototype in a 2nd embodiment to implantation of a blade for metallic molds into a collapsible mold. It is typical explanatory drawing of the process from preparation of a prototype in a 2nd embodiment to implantation of a blade for metallic molds into a collapsible mold. It is a schematic diagram explaining the implantation operation | work of the braid | blade for metal mold | die with respect to the collapsible casting_mold | template of FIG. It is a schematic diagram explaining the implantation operation | work of the braid | blade for metal mold | die with respect to the collapsible casting_mold | template of FIG. It is a schematic diagram explaining the implantation operation | work in the case of implanting the braid | blade for metal mold | die which has an undercut part of a circular cross section in a collapsible mold. It is a schematic diagram explaining the planting operation | work in the case of implanting the braid | blade for metal mold | die which has an undercut part of a waveform cross section in a collapsible mold. It is a schematic diagram of an example of the groove | channel formed in the collapsible casting_mold | template. It is a schematic diagram explaining the implantation operation | work of the braid | blade for metal mold | die with respect to the collapsible casting_mold | template of 3rd Embodiment. It is explanatory drawing of the buckling of a braid | blade. It is a schematic diagram explaining 4th Embodiment. It is a typical perspective view of the braid | blade for metal mold | die used for the Example.

  Hereinafter, a first embodiment of a method for manufacturing a tire mold according to the present invention will be specifically described with reference to the drawings.

  In FIG. 1, the typical explanatory drawing of the manufacturing process of the tire shaping die which applied the manufacturing method of this embodiment is shown in order of FIG. 1 (a)-(j) in order of a process. Although FIG. 1 shows an example in which the tire molding die is a sectional mold type die, this embodiment is not limited to the die shown in FIG. 1 and is a two-piece mold type die. There may be.

  In the present embodiment, a tire molding die is manufactured by a casting method using a transfer method. First, the prototype 11 is produced (FIG. 1 (a)). On the surface of the master 11, a tread shape to be transferred to a tire molding die manufactured by the manufacturing method of the present embodiment is processed and formed. Of course, a sipe forming blade is projected on the design surface of a tire molding die cast in a later process. However, unlike the prior art, a prototype blade is attached to the surface of the prototype 11. There is no need.

  Next, the produced prototype 11 is placed with the surface of the tread shape processed and formed in the mold 12 for rubber mold formation, and the raw material of the rubber mold is supplied to the prototype 11 and cured. Thus, the rubber mold 13 composed of the rubber portion 13a and the base portion 13b is manufactured (FIG. 1B). The raw material and manufacturing conditions of the rubber mold 13 can be the same as those of a known rubber mold. For example, the rubber part 13a can be made of silicone rubber and the base part 13b can be made of gypsum. When the original mold 11 is removed from the mold 12 for forming the rubber mold after the rubber mold 13 is cured, the surface shape of the original mold 11 is transferred to the surface of the first rubber portion 13a of the rubber mold 13. Unlike the prior art, the manufacturing method of this embodiment does not attach a mold blade to the surface of the transferred rubber mold 11.

  Slurry collapsible mold material toward the rubber mold 13 in which the vertical direction of the mold 12 is reversed from the time of manufacture of the rubber mold 13 so that the surface of the first rubber section 13a is above the base section 13b. Is injected to mold the collapsible mold 14 (FIG. 1C). As the collapsible mold material, plaster and other collapsible mold materials used for casting a tire molding die can be used. When the cured collapsible mold material is removed from the rubber mold 13, the tread shape transferred from the rubber mold 13 is formed on the surface of the molded collapsible mold 14.

  A mold blade 15 is prepared and implanted into the molded collapsible mold 14 (FIG. 1 (d)). As the mold blade 15, a blade itself that is cast into a tire molding mold casting and protrudes to the design surface in a later process is used. In the example shown in FIG. 1D, three types of mold blades 15 are prepared, which are blades 15a, blades 15b, and blades 15c, corresponding to the sipe at the end in the width direction and the center of the tire.

  Implanting of these mold blades 15 is performed at a predetermined position of the tread shape of the collapsible mold 14 using an implantation tool, for example, a hammer T1 (FIG. 1 (e)). The mold blade 15 is embedded at a predetermined depth from the surface of the collapsible mold 14, in other words, the mold blade 15 protrudes from the surface of the collapsible mold 14 at a predetermined height. The blade 15 is implanted while adjusting the height from the surface of the mold blade 15 using a height measuring tool, for example, a gauge T2. The implantation tool is not limited to a hammer, and for example, an ultrasonic vibration tool can be used.

  When a gap is formed between the mold blade 15 and the collapsible mold 14 around the mold blade 15 by the implantation of the mold blade 15, a slurry applicator, such as a brush T3, is formed in the gap. The collapsible mold material slurry S is applied to fill the gap (FIG. 1 (f)).

  The collapsible mold 14 in which the mold blade 15 is implanted is completed by drying and firing while circulating the air with the fan F while being heated with the heater H of the heater (FIG. 1 (g)).

  A metal mold casting is poured into a casting space formed by the completed collapsible mold 14 and the casting frame 16 to cast a tire molding mold casting 17 (FIG. 1 (h)). The casting frame 16 may be made of a collapsible material or a non-collapseable material as long as it is a material usually used for a tire molding die. Examples of the metal used as the tire molding die casting 17 include an aluminum alloy. In the present embodiment, the metal material is not particularly limited as long as it is a metal material suitable for the tire molding die.

  After the casting, the collapsible mold 14 and the casting frame 16 are removed from the tire molding die casting 17 (FIG. 1 (i)). Since the collapsible mold 14 is collapsible, the mold can be easily separated. When the collapsible mold 14 is removed from the tire casting mold casting 17, the mold blade 15 that has been implanted at a predetermined height on the surface of the collapsible mold 14 at a predetermined height is the length of the predetermined height. Thus, it is cast into the tire molding die casting 17 and protrudes from the design surface of the molding die casting 16 by the depth embedded from the surface of the collapsible mold 14 at a predetermined depth.

  Thereafter, the tire molding die casting 17 is processed into a predetermined size to complete the tire molding die 18 (FIG. 1 (j)).

  In the manufacturing method of the tire mold according to this embodiment, the collapsible mold 14 is molded without attaching the mold blade 15 to the rubber mold 13, and the mold blade 15 is formed on the collapsible mold 14 after molding. Implant. The collapsible mold material cast into the rubber mold 13 is a slurry in which a refractory material powder is kneaded with a solvent (liquid) or a binder (binding material), and the collapsible mold formed by curing the slurry. No. 14 has microscopic pores due to the solvent or binder. Due to the presence of the micropores, the collapsible mold 14 after molding has low hardness, so that the mold blade 15 can be easily implanted with an implantation tool. This is utilized in the present embodiment.

  In the manufacturing method of the present embodiment, it is not necessary to attach a prototype blade to the prototype 11, so that the process of manufacturing the prototype blade can be omitted. Further, since the mold blade is not attached to the rubber mold 13, this attachment step can be omitted. Also, as in the prior art, interference occurs between the blade and rubber in the rubber transfer process, the mold material enters the gap between the blade and rubber in the transfer process to the mold, or the mold is removed from the rubber mold. In this case, no template defect occurs. This makes it possible to avoid rubber mold deformation and dimensional accuracy problems, eliminate the need to remove the casting burr between the blade and rubber, and further reduce the dimensional accuracy near the blade due to mold defects. Can be avoided. Furthermore, since the mold blade 15 is attached to the collapsible mold 14 by implantation using an implantation tool, a small gap (0.02 to 0.02) is provided between the mold blade 15 and the collapsible mold 14 during implantation. (About 0.04 mm) is spontaneously formed. As a result, when the tire molding die casting 17 is cast, it is possible to avoid the occurrence of breakage of the collapsible mold 14 (mold depression defect) even if the mold blade 15 is thermally expanded.

  In the present embodiment, the mold blade 15 is implanted by physically pushing the thin plate-shaped mold blade 15 into the collapsible mold 14 made of gypsum or the like. The low-disintegrating mold 14 may cause chipping in the area where the mold blade 15 is to be implanted. In order to explain this with reference to the drawings, FIGS. 2 (a) to 2 (f) show schematic diagrams for explaining the operation of implanting the mold blade 15 into the collapsible mold 14 in chronological order.

  FIG. 2 shows an example in which a guide groove or the like is not formed in the collapsing direction of the mold blade 15 in the collapsible mold 14 at the position where the mold blade 15 is implanted (FIG. 2A). When the mold blade 15 is implanted in the collapsible mold 14 by the implantation tool T1, in the example shown in FIG. 2B, cracks are generated near the surface of the portion of the collapsible mold 14 where the mold blade 15 is implanted. Occurs, and the small pieces 14 p are missing from the surface of the collapsible mold 14. Therefore, a chip 14c is generated in the collapsible mold 14 around the mold blade 15 after the implantation operation (FIG. 2 (c)). In order to repair the chip 14c, the slurry S of the collapsible mold material used for casting the collapsible mold 14 is filled into the chip 14 using the brush T3 (FIG. 2 (d)), and after drying the slurry, The extra collapsible mold material is removed with a spatula T4 (FIG. 2 (e)). By performing this repairing operation, it is possible to prevent a decrease in dimensional accuracy of the tire molding die due to the occurrence of the chip 14c.

  Next, a second embodiment of the method for producing a tire mold according to the present invention will be described. In this embodiment, a groove for attaching a sipe blade is formed in the original mold, the groove is transferred from the original mold to a collapsible mold through a rubber mold, and the sipe blade is implanted in the groove. Other processes are the same as those in the first embodiment. This embodiment will be described with reference to FIGS.

  FIGS. 3A to 3D are schematic explanatory views of the steps from production of a prototype to implantation of a blade for a mold into a collapsible mold in the order of steps. In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and redundant description of the same components is omitted below.

  The present embodiment shown in FIG. 3 is different from the first embodiment shown in FIG. 1 in that the prototype 11A is manufactured (FIG. 3A). 11ss is formed. The groove 11ss is transferred in a subsequent process and formed on the collapsible mold 14A, and becomes a groove 14ss for guiding the mold blade 15 when the mold blade 15 is implanted in the collapsible mold 14A. The method for forming the groove 11ss in the prototype 11A is not particularly limited, and a formation method generally used for processing the prototype can be used. The groove 11ss is substantially the same as the width and thickness of the mold blade 15 and has a slightly larger width and thickness so that the mold blade 15 can be accommodated. Further, in the example shown in FIG. 3, the depth of the groove 11ss from the surface of the original mold 11 is shorter than the implantation depth when the mold blade 15 is implanted in the collapsible mold 14A in the subsequent process.

  The groove 11ss on the surface of the original mold 11A is transferred to the rubber part 13c on the surface of the rubber mold 13A when the rubber mold 13A is manufactured (FIG. 3B), and when the collapsible mold 14A is molded, It is transferred to the surface (FIG. 3C). When the cured collapsible mold material 14A is removed from the rubber mold 13A, a groove 14ss transferred from the rubber mold 13A is formed on the surface of the collapsible mold 14A (FIG. 3 (d)). Using 14ss as a guide, the mold blade 15 is attached to the collapsible mold 14A, and the mold blade 15 is implanted so as to have a predetermined height.

  FIG. 4 is a schematic explanatory view similar to FIG. In another example of the second embodiment shown in FIG. 4, in the production of the prototype 11B (FIG. 4A), a slit-shaped groove 11sl is formed on the surface of the prototype 11B. The other steps of the groove 11sl are the same as those shown in FIG. 4 in the example shown in FIG. 4 is that the depth of the groove 11sl is deeper than the depth of the groove 11ss. The depth of the groove 11sl from the surface of the original mold 11A in FIG. 4 is the same as the implantation depth when the mold blade 15 is implanted in the collapsible mold 14B in a later step.

  FIGS. 5A to 5C are schematic diagrams for explaining the implantation work of the mold blade 15 on the collapsible mold 14A shown in FIG. 3 in time series. FIGS. 6A to 6C are schematic diagrams for explaining the implantation work of the mold blade 15 on the collapsible mold 14B shown in FIG. 4 in time series. As understood from FIGS. 5 and 6, in this embodiment, the grooves 11ss and 11sl of the prototypes 11A and 11B are transferred to the collapsible molds 14A and 14B, and are shallower than the implantation depth of the mold blade 15. A groove 14ss (FIG. 5A) having a depth equal to the depth of implantation of the mold blade 15 is formed in advance. When the mold blade 15 is implanted into the collapsible molds 14A and 14B, the mold blade 15 is attached to the collapsible molds 14A and 14B using the groove 14ss or the groove 14sl as a guide, and the mold blade 15 is set to a predetermined height. Then, it is implanted (FIGS. 5B and 6B).

In this way, the groove 11ss or the groove 11sl is formed in the original mold, and when the blade is implanted in the collapsible molds 14A and 14B, the groove 14ss or the groove 14sl formed by the transfer is used as a guide, and the mold blade 15 is predetermined. By planting at a height, it is possible to suppress the occurrence of chipping in the collapsible molds 14A and 14B around the mold blade 15 (FIGS. 5C and 6C). Therefore, the manufacturing method of the tire molding die according to this embodiment not only has the effects of the first embodiment, but also has a collapsible mold in which no groove is formed as described in FIG. 14, it is not necessary to repair a chip that may occur when the mold blade 15 is implanted, and a tire molding mold having high dimensional accuracy can be manufactured.

  In order to form the groove 14ss in the collapsible mold 14A or the groove 14sl in the collapsible mold 14B, the groove 11ss or the groove 11sl formed in the prototypes 11A and 11B both have the above-described effects, but the depth of the groove However, the groove 11ss shallower than the groove 11sl has an advantage that the groove can be easily formed. On the other hand, the groove 11sl having the same depth as that of the mold blade is designed by devising the shape of the groove so that the mold blade having an undercut portion is cast on the collapsible mold 14 when the mold blade is implanted. There is an advantage that it can be rounded.

  7A to 7D are schematic diagrams for explaining an implantation operation when a mold blade 15A having an undercut portion having a circular cross section as an example of the undercut portion is implanted in the collapsible mold 14C. The figure is shown in chronological order. The groove formed in the original mold has a slit width wider than the diameter of the undercut portion of the circular cross section of the mold blade 15A, and a circular cross section cavity corresponding to the undercut portion is formed at the groove bottom center in the width direction of the groove. To the one end side of the groove is formed. The groove having such a shape is transferred from the original mold to the collapsible mold 14C through the rubber mold to form the groove 14a (FIG. 7A). The mold blade 15A is inserted into the groove 14a formed in the collapsible mold 14 (FIG. 7B), and then the mold blade 15A contacts one end face in the groove width direction in the groove 14a. The mold blade 15A is moved as shown in FIG. 7 (c) .This movement is simply because the circular cross-section cavity at the bottom of the groove 14a is biased toward one end in the groove width direction. This is realized simply by inserting the mold blade 15A until it reaches the bottom of the groove 14a, and after the movement, the space in the groove 14a is filled with a slurry of a collapsible mold material and solidified ((d) in FIG. 7). In this manner, the mold blade 15A having an undercut portion having a circular cross section can be implanted in the collapsible mold 14C with high dimensional accuracy.

  FIGS. 8A to 8D are schematic diagrams for explaining the implantation work when the mold blade 15B having an undercut portion having a corrugated cross section as an example of the undercut portion is implanted in the collapsible mold 14D. Shown in order of series. A groove having a slit width wider than the amplitude of the undercut portion of the corrugated cross section of the mold blade 15B is formed as the groove formed in the original mold. The groove having such a shape is transferred from the original mold to the collapsible mold 14D through the rubber mold to form the groove 14b (FIG. 8A). The mold blade 15B is inserted into the groove 14b formed in the collapsible mold 14D (FIGS. 8B and 8C). After the insertion, the space in the groove 14b is filled with a slurry of a collapsible mold material and solidified ((D) in FIG. 8) In this way, the mold blade 15B having an undercut portion having a corrugated cross section is obtained. The collapsible mold 14D can be implanted with high dimensional accuracy.

  8 is inserted into the groove 14b formed in the collapsible mold 14B, and then the space in the groove 14b is filled with the slurry of the collapsible mold material. Sometimes ((FIG. 8 (d)), depending on the relationship between the undercut shape and the groove shape of the groove 14b, it may be difficult to sufficiently fill the slurry into the groove 14b.

  In such a case, as shown in FIG. 9A, the groove 14c formed in the collapsible mold 14 has a shape in which a wide auxiliary groove 14d is connected to both ends in the length direction of the linear groove. The groove 14c may be formed. The groove 14c having this shape can be formed, for example, by forming a groove having the same shape in the original mold and transferring it from the original mold to the collapsible mold 14D through a rubber mold. The mold blade 15B is inserted into the groove 14c (FIG. 9B), and the space in the groove 14c is supplied with the slurry of the collapsible mold material from the auxiliary grooves 14d at both ends of the groove 14c and filled (FIG. 9B). 9 (c)). After the filled slurry is solidified, the surplus collapsible mold material is removed to complete the implantation process (FIG. 9D). By using the groove 14c having such a shape formed by connecting the auxiliary grooves 14d, the slurry can be sufficiently filled in the space in the groove 14c in which the mold blade 15B having the undercut portion is inserted.

  Next, a third embodiment of the method for producing a tire mold according to the present invention will be described. In this embodiment, a foamed mold material is used as the collapsible mold material. The other processes are the same as those in the first embodiment or the second embodiment. Foamed mold material is a material in which air is intentionally engulfed in the slurry when stirring the mold material slurry, and the bubbles are increased by the bubbles to lower the density, dramatically improving the lightness and air permeability after curing. It is. For this reason, the use of a foamed mold material generally improves the shape transfer accuracy, can suppress the occurrence of casting defects such as pinholes as much as possible, can improve the disintegration of mold varieties, etc. This has the effect of minimizing the amount of material used. In the present embodiment, by using a collapsible mold made of a foam mold material for casting a tire molding die, these effects are achieved, and the effects of the first embodiment or the second embodiment are further achieved. This has the effect of suppressing mold defects that may occur when a mold blade is implanted in the collapsible mold. The effect which can suppress this template defect | deletion is demonstrated using FIG.

  FIGS. 10A to 10E are schematic diagrams for explaining the operation of implanting the mold blade 15C into the collapsible mold 14E made of the foam mold material of the present embodiment in time series. A collapsible mold 14E shown in FIG. 10 is an example in which a guide groove is not formed in advance at a position where a mold blade 15C having a corrugated cross section is implanted (FIG. 10A). When the mold blade 15C is implanted in the collapsible mold 14E with the hammer T1, bubbles in the vicinity of the mold blade 15C in the collapsible mold 14E are crushed by the pressure by the mold blade 15C, and the mold for the blade is used. It will play the role of absorbing the volume exclusion of (Fig. 10 (b)). Therefore, by using the collapsible mold 14E made of the foam mold material according to the present embodiment, cracks are prevented from occurring in the mold material around the mold blade 15C when the mold blade 15C is implanted. It has the effect of making it difficult to generate. After the mold blade 15C is implanted in the collapsible mold 14E at a predetermined depth, the mold material slurry S is filled in the gap around the mold blade 15C using the brush T3 (FIG. 10C). After the filled slurry is solidified, the excess collapsible mold material is removed with a spatula T4 (FIG. 9D), and the implantation process is completed (FIG. 9E).

  As a technique for foaming the mold material, a conventional technique such as Japanese Patent No. 3560491 can be used. The expansion ratio depends on the thickness of the mold blade to be implanted, the undercut shape, and the strength characteristics of the mold material, but is preferably about 15 to 80 vol%. This foaming rate is defined as a percentage of a value obtained by dividing the volume increased by foaming by the volume before foaming of the slurry (volume increased by foaming / volume before foaming × 100). If the expansion ratio is less than about 15 vol%, a sufficient excluded volume absorption effect may not be exhibited, and the effect as a foam mold material is not sufficient. If the expansion ratio exceeds about 80 vol%, there may be a problem in strength characteristics and thermal expansion / contraction characteristics as a casting mold.

  In the example shown in FIG. 10, the collapsible mold 14E made of the foam mold material is an example in which there is no groove at the position where the mold blade 15C is implanted, but this embodiment is not limited to the illustrated example. 5 and a guide groove as shown in FIG. 6 may be used.

  Next, a fourth embodiment of the method for manufacturing a tire molding die according to the present invention will be described. In this embodiment, when the mold blade is implanted in the collapsible mold, the mold blade is implanted in a state of being elastically deformed.

  Generally, a mold blade attached to a tire mold is often manufactured by press molding with a press mold. Examples thereof are described in JP-A No. 2002-355823 and JP-A No. 2002-337147. However, when the material of the mold blade has a high strength property and a thin plate thickness, the press bending may not give a desired bending shape. For example, in the case of a bent shape with undulating undulations, it is difficult for plastic flow due to increase or decrease in sheet thickness to occur in press forming, and thus wrinkles may occur. Further, in the case of a gently bent shape, it may not be possible to deform the plastic deformation region of the material by press molding. The case of a gently bent shape will be described with reference to FIG. 11. A blade material m having a thin plate thickness is prepared (FIG. 11A), and this blade material m is loosened using a pair of press dies D1 and D2. When press-molding into a bent shape (FIG. 11B), the blade material m after pressing returns to a shape deviated from the bent shape at the time of pressing due to the elastic deformation recovery of the blade material m ( FIG. 11 (c)).

  Japanese Patent Laid-Open No. 11-33677 describes a technique for obtaining a high-strength blade by bending a precipitation-aged steel after solution treatment and then subjecting it to precipitation age hardening. It is theoretically possible to produce an ultrathin blade of about 0.1 to 0.15 mm. However, since the desired bending shape cannot be imparted to the blade even by this technique, the degree of freedom of application of this technique is low.

  As can be seen from the above, in order to obtain a mold blade having a predetermined bent shape by press molding, stress and strain exceeding the elastic yield limit must be applied over almost the entire area of the mold blade in the plate thickness direction. However, when it is desired to impart a gentle bending shape to a thin-walled, high-strength mold blade, it is extremely difficult to apply stress and strain exceeding the elastic yield limit to the mold blade by pressing.

  Therefore, in this embodiment, the mold blade is implanted into the collapsible mold in a state of being elastically deformed. The present embodiment will be described with reference to schematic explanatory diagrams shown in FIGS. 12A to 12F in time series order.

  The collapsible mold 14F is formed according to any of the first to third embodiments described above, and a mold blade 15D is prepared (FIG. 12A). When the mold blade 15D is implanted in the collapsible mold 14F, an external force is applied to the mold blade 15D to elastically deform it into a desired bent shape (FIG. 12B). The means for applying this external force is not particularly limited. For example, the mold blade 15D may be bent manually so that a predetermined bending shape is obtained, or a predetermined blade holder is prepared, and the mold blade 15D is attached to the blade holder, The bent shape may be held at the time of implantation.

  The mold blade 15D is implanted into the collapsible mold 14F in an elastically deformed state (FIG. 12C). On the surface of the collapsible mold 14F to be implanted, a groove 14e for guiding the mold blade 15D may be formed as in the second embodiment, or as in the first embodiment. It does not have to be. In addition, the collapsible mold 14F may be a non-foaming mold or a foaming mold.

  Since the implanted mold blade 15D is fixed by the collapsible mold 14F, it retains a predetermined bent shape without applying an external force. The tire molding die casting 17A is cast in a state where the bent shape is maintained (FIG. 12 (d)). After casting, the collapsible mold 14F is removed from the tire molding die casting 17A (FIG. 12 (e)) to obtain the tire molding die casting 17A (FIG. 12 (f)). The obtained tire molding die casting 17A is processed into a predetermined size to complete the tire molding die, as in any of the first to third embodiments.

  This embodiment has the effects of any of the first to third embodiments, and in addition, by implanting the mold blade 15D in the collapsible mold 14F in an elastically deformed state, This die for molding a tire is not necessary when the blade 15D is pressed, and particularly when it is desired to cast a blade having a material, thickness, and bending shape, to which plastic strain is difficult to apply, into the tire molding die casting 17A. This has the effect of maintaining the blade shape required for the casting 17A.

  When both ends of the mold blade 15D are open as shown in FIG. 12, there may be some springback after casting. In order to suppress this spring back, a method using a material showing age-hardening for the mold blade material as described in Japanese Patent No. 3312002 can be used.

The manufacturing conditions for tire molding of each Example described below were as follows.
Prototype material: synthetic wood (basic shrinkage setting: 11.5 / 1000),
Rubber type: Silicone rubber type with gypsum backing (rubber layer thickness 15mm),
Gypsum mold: G-1 foamed gypsum manufactured by Oritake Gypsum, or G-6 non-foamed gypsum cast alloy: AC4C aluminum alloy (Si: 7 mass%, Mg: 0.4 mass%, Fe: 0.3 mass%, Residual: Al),
Casting method: Block casting method Casting temperature: 700 ° C,

The basic dimensions of tire mold castings that are cast are:
Design surface diameter: φ600 ± 20mm,
Tire width dimension: about 195 ± 30mm,
Casting wall thickness: 70-100mm,
Total casting height: 300 ± 30mm,
Number of sector divisions: 9/1 ring (approximately 40deg),
Met.

  The tire molding die castings of each example were produced by transferring / reversing from an original mold → a rubber mold → a mold → a casting according to FIG.

  In addition, the number of blades cast into the casting was 4 types in total including the following types 1 to 4, and the shape of the blades, the blade material, and the number of cast balls were as follows.

(Type 1)
Blade shape: shape shown in FIG. 13 (a), plate thickness 0.15 mm, plate length: 50 mm, depth cast into mold: 5 mm, total height: 15 mm,
Blade material: MAS1C maraging steel (Ni: 18.5 mass%, Al: 0.1 mass%, Ti: 0.6 mass%, Mo: 4.8 mass%, Co: 9.0 mass%, the rest: Fe),
Casting number of sheets: 12 sheets / 1 sector, total of 108 sheets in 9 sectors,

(Type 2)
Blade shape: shape shown in FIG. 13B, plate thickness 0.4 mm, plate length: 65 mm, depth cast into mold: 5 mm, overall height: 15 mm, waveform amplitude: 4 mm, waveform cycle: 6 mm ,
Blade material: SUS 304 stainless steel (Cr: 18% by mass, Ni: 8% by mass, Mn: 2% by mass or less, Si: 1% by mass or less, C: 0.15% by mass or less, remainder: Fe),
Casting number of sheets: 12 sheets / 1 sector, total of 108 sheets in 9 sectors,

(Type 3)
Blade shape: shape shown in FIG. 13C, plate thickness 0.4 mm, plate length: 41 mm, depth cast into mold: 5 mm, total height: 15 mm, waveform amplitude: 4 mm, waveform cycle: 6 mm ,
Blade material: SUS 304 stainless steel (Cr: 18% by mass, Ni: 8% by mass, Mn: 2% by mass or less, Si: 1% by mass or less, C: 0.15% by mass or less, remainder: Fe),
Casting number of sheets: 24 sheets / sector, 9 sectors, a total of 216 sheets,

(Type 4)
Blade shape: shape shown in FIG. 13 (d), plate thickness 0.15 mm, plate length: 50 mm, depth cast into mold: 5 mm, total height: 15 mm, curvature radius R: 100 mm,
Blade material: MAS1C maraging steel (Ni: 18.5 mass%, Al: 0.1 mass%, Ti: 0.6 mass%, Mo: 4.8 mass%, Co: 9.0 mass%, the rest: Fe),
Casting number of sheets: 12 sheets / 1 sector, total of 108 sheets in 9 sectors,

  In addition, types 1 to 3 are formed by press molding, and type 4 is not subjected to press molding, and is elastically deformed into the above shape by hand when a blade is implanted in a mold.

Example 1
Example 1 is an example corresponding to the first embodiment.

  The mold material powder used is G-6 (non-foamed gypsum) of the above-mentioned gypsum mold, the water mixing ratio is 60% (600 g of water per 1 kg of the powder), and the foaming ratio is almost 0% (non-foamed). The cast slurry was poured into a rubber mold and cured to prepare a gypsum mold. In producing this gypsum mold, a slit for implanting a blade into the original mold was not formed, and only a marking line for positioning was used.

Using the above conditions, a mold casting for tire molding was cast and manufactured by directly implanting the type 1 blade into a predetermined part of a gypsum mold (green mold before drying). As a result, a sound casting was obtained.
An ultrasonic vibration tool was used when the blade was implanted in the mold.

(Example 2)
Example 2 is an example corresponding to the second embodiment.

  The mold material powder used is G-6 (non-foamed gypsum) of the above-mentioned gypsum mold, the water mixing ratio is 60% (600 g of water per 1 kg of the powder), and the foaming ratio is almost 0% (non-foamed). The cast slurry was poured into a rubber mold and cured to prepare a gypsum mold. In producing the gypsum mold, a slit for blade implantation into the original mold was given a slit shape having a depth of 60% (6 mm) of the height of the blade design surface.

Using the above conditions, a mold casting for tire molding was cast and produced by directly implanting the type 2 blade in a predetermined part of a gypsum mold (green mold before drying), and a sound casting was obtained.
An ultrasonic vibration tool was used when the blade was implanted in the mold.

(Example 3)
Example 3 is an example corresponding to the third embodiment.

  The mold material powder used is G-1 (foamed gypsum) of the above gypsum mold, the water mixing ratio is 70% (700 g of water per 1 kg of the powder), and the foaming ratio is approximately 50% (50% of the total mold volume). Was made into a rubber mold and cured to prepare a gypsum mold. In producing this gypsum mold, a slit for implanting a blade into the original mold was not formed, and only a marking line for positioning was used.

Using the above conditions, after directly implanting the type 3 blade in a predetermined part of the gypsum mold (green mold before drying), the gap formed between the mold and the blade is refilled with gypsum slurry and finished. After that, it was used for casting. In this way, when a tire casting mold casting was cast and produced, a sound casting was obtained.
A hammer was used to implant the blade into the mold.

Example 4
Example 4 is an example corresponding to the fourth embodiment.

  The mold material powder used is G-1 (foamed gypsum) of the above gypsum mold, the water mixing ratio is 70% (700 g of water per 1 kg of the powder), and the foaming ratio is approximately 30% (30% of the total volume of the mold). Was made into a rubber mold and cured to prepare a gypsum mold. In producing this gypsum mold, a slit for blade implantation into the original mold was given a slit shape having a depth of 40% (4 mm) of the height of the blade design surface.

  Using the above conditions, insert a flat blade material into a predetermined part of a gypsum mold (green mold before drying) by hand so as to be a type 4 shape and fit it into the slit part of the gypsum mold. Then, after being implanted into the mold while maintaining the shape, the blade was cast into a casting using casting.

  In this way, when a tire casting mold casting was cast and produced, a sound casting was obtained. Further, even in the obtained casting, a blade shape having a gentle R shape with a radius of curvature R100 was obtained.

(Comparative Example 1)
Comparative Example 1 is an example in which the same blade as in Example 2 was cast into a tire mold casting using a conventional manufacturing method. This conventional manufacturing method is a method in which a mold blade is implanted in a rubber mold and then a gypsum slurry is poured into the rubber mold and cured by using a gypsum mold obtained by curing, and the blade is cast. . This conventional method has the following problems.

  (1) When a blade was implanted in the rubber mold slit, a gap of about 0.1 to 0.3 mm was generated between the rubber mold and the blade, and a slight undulation was generated on the rubber surface (due to curing shrinkage of the rubber material). Bug).

  (2) In the gypsum mold, a large amount of gypsum deposits (burrs) were generated around the blades (problems caused by the occurrence of gaps between the rubber mold and the blade as described above).

  (3) A step defect (mold depression defect) of about 0.2 to 0.5 mm occurred at one end of the blade (defect caused by blade thermal expansion during casting).

(Comparative Example 2)
In Example 4 described above, an attempt was made to form with a press molding machine instead of elastically deforming the type 4 blade, but the spring back was large and the target shape could not be obtained.

  As mentioned above, although the manufacturing method of the mold for tire molding of this invention was demonstrated using each embodiment, each Example, and drawing, this invention is not limited to description of these embodiment, an Example, or drawing. Many variations are possible within the scope described in the specification and drawings.

11: prototype 12: mold 13: rubber mold 14: collapsible mold 15: blade 16: casting frame 17: tire molding mold 18: tire molding mold

Claims (4)

A rubber mold is transferred from a prototype having the tread shape of the tire,
Without attaching a sipe forming blade to this rubber mold, a collapsible mold material is cast to mold a collapsible mold,
Implant the blade in the collapsible mold after molding,
Cast using a collapsible mold after implantation,
Producing a mold for molding a tire having a blade;
A method for producing a mold for molding a tire characterized by the above.   A groove is processed and formed at a position where the blade is attached in the original mold, the groove is transferred and formed on the collapsible mold from the original mold through the rubber mold, and the blade is implanted in the groove as a guide. Manufacturing method of tire mold.   The method for manufacturing a mold for molding a tire according to claim 1 or 2, wherein a foamed mold material is used as the collapsible mold material.   The method for manufacturing a tire molding die according to any one of claims 1 to 3, wherein when the blade is implanted in a mold, the blade is implanted in a state of being elastically deformed.

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