Patent Description:
A mold for molding tire is provided in a tire vulcanizing apparatus to mold the tire during vulcanization of the tire (unvulcanized tire). In addition, the mold for molding tire is usually manufactured by casting according to their shape and required characteristics. As a method of manufacturing such mold for molding tire, a method of manufacturing has been known in which an original mold, a rubber mold, a gypsum mold and the mold for molding tire (tire vulcanization mold) are produced in order (see Patent Document <NUM>).

In a conventional method of manufacturing the mold for molding tire described in Patent Document <NUM>, the original mold is formed into a shape corresponding to a tread shape of the tire, and a rubber mold is molded by the original mold. Next, the gypsum mold is molded by the rubber mold, and the mold for molding tire is cast using the gypsum mold. But the original mold is formed into a complicated shape corresponding to the tread shape of the tire having various grooves. Therefore, it requires a lot of trouble to produce the original mold, and as the tread shape of the tire becomes complicated, manufacturing efficiency of the original mold and the mold for molding tire is lowered. In addition, it is difficult to form a wall surface of the groove of the original mold into a complicated shape.

In a tire having sipes (fine grooves) in the tread part, a sipe is molded in the tread part by a projection of the mold for molding tire. If the projection is formed in the mold for molding tire by casting, the projection is likely to be damaged by a force applied during molding of the tire. Therefore, a blade for molding the sipe is formed by press forming of a high-strength plate material (for example, steel). A part of the blade is cast in the mold for molding tire, the blade is thereby fixed to the mold for molding tire. In addition, when producing the original mold, a plate-like projecting member corresponding to a blade (a blade for the original mold) is attached to the original mold.

<FIG> are perspective views showing an example of a process for producing the original mold <NUM> of the conventional mold for molding tire. <FIG> shows the original mold <NUM> during production, and <FIG> shows the original mold <NUM> after production.

As shown in the figures, the projecting member <NUM> is attached so as to project toward the original mold <NUM>, thus the original mold <NUM> is produced. By the projecting member <NUM>, a groove part is formed in the rubber mold, and a blade is inserted into the groove part of the rubber mold. The blade is transferred from the rubber mold to a gypsum mold, and a part of the blade is cast in the mold for molding tire.

Since it is necessary to attach a plurality of projecting members <NUM> in the original mold <NUM> corresponding to the number of sipes, it requires a lot of work to produce the original mold <NUM>. In addition, the projecting member <NUM> is smaller than the blade and is easily deformed by the press forming. Therefore, if the blade and the projecting member <NUM> are molded by the same pressing mold with the same pressing pressure, the projecting member <NUM> is deformed larger compared with the blade. If a difference arises between dimension of the projecting member <NUM> and dimension of the blade in this way, the rubber mold is deformed by the blade inserted into the groove. In this case, the shape of the rubber mold is likely to be damaged, or a deviation is likely to occur in the rubber molding pattern. When gypsum enters between the blade and the rubber mold, burrs may be generated in the gypsum mold. Due to the work of removing burrs, the manufacturing efficiency of the mold for molding tire is further reduced.

Patent Literature <NUM>: Japanese Patent Application Laid-Open No. <CIT> Attention is also drawn to the disclosure of <CIT> which discloses a method of manufacturing a mold for molding a tire that is considered to comprise method steps corresponding to: producing an original mold having a tread shaping part including a tread shape of the tire, producing an intermediate mold having a transfer part to which the tread shaping part of the original mold is transferred, forming a casting mold by the transfer part of the intermediate mold, and casting the mold for molding tire using the casting mold, wherein the original mold is produced by forming a surface part of the tread shaping part and attaching the surface part to a base part of the original mold, wherein a projection of a shape corresponding to a cast-in part of a blade for molding sipe is formed integrally with the surface part of the tread shaping part, a groove part is formed in the transfer part of the intermediate mold by the projection of the surface part, and the cast-in part of the blade is inserted into the groove part of the transfer part.

<CIT> discloses when a dummy sipe is inserted in the sipe part of a master in a process for manufacturing a casting mold comprising gypsum, a recessed groove is preformed along the tread surface of the master in the thickness direction of the dummy sipe and, in a state that the dummy sipe is inserted in the sipe part of the master, the recessed groove is positioned in the vicinity of the tread surface.

The present invention has been made in view of conventional problems of the mold for molding tire that is cast using a mold, and its object is to easily manufacture a mold for
molding tire by easily producing an original mold of the mold for molding tire.

The present invention is related to a method of manufacturing a mold for molding tire as claimed in claim <NUM>.

According to the present invention, the original mold of the mold for molding tire can be easily produced, and the mold for molding tire can be easily manufactured.

One embodiment of a method of manufacturing a mold for molding tire of the present invention will be described with reference to the drawings.

In the method of manufacturing the mold for molding tire of the present example, the mold for molding tire is manufactured by casting. In addition, the mold for molding tire of the present example is a metal mold for molding tire and is used during vulcanization of the tire. The tire (unvulcanized tire) is vulcanized while being molded by the mold for molding tire. Hereinafter, a plurality of examples and an embodiment of the method of manufacturing the mold for molding tire will be described in order.

<FIG> to <FIG> are perspective views showing the manufacturing process of the mold for molding tire <NUM> of the 1st example.

As shown in the figures, the mold for molding tire <NUM> (see <FIG>) is manufactured by a casting production process using a transfer method. In addition, in the mold for molding tire <NUM>, a plurality of sipes (fine grooves) in the tread part of the tire are molded by a plurality of blades <NUM>.

At first, the original mold <NUM> of the mold for molding tire <NUM> is produced (see <FIG>). The original mold <NUM> is a master model including a shape of the tread part (a tread shape) of the tire and has a tread shaping part <NUM> and a plurality of projections <NUM> formed projecting on the tread shaping part <NUM>. Here, the tread shape of the tire is a shape of a part of the tread part in the tire circumferential direction (a divided part that is one of a plurality of divided parts of the tread part divided in the tire circumferential direction), and the original mold <NUM> is formed in a shape corresponding to the part of the tread part in the tire circumferential direction.

The tread shaping part <NUM> is a molding part of the original mold <NUM> and is formed in a shape corresponding to the tread shape of the tire. In addition, a plurality of grooves 3A are formed in the tread shaping part <NUM> corresponding to the grooves of the tread part of the tire, and a plurality of land parts 3B are formed in the tread shaping part <NUM> corresponding to a plurality of land parts of the tread part of the tire. The projection <NUM> is provided at a position corresponding to the sipe (sipe position) of the tire in the tread shaping part <NUM> and is formed in an elongated plate-shape extending along the sipe position. The land part 3B is partitioned by the grooves 3A, and the projection <NUM> is each formed in a plurality of positions on the land part 3B.

Next, an intermediate mold <NUM> is molded by the tread shaping part <NUM> of the original mold <NUM>, the intermediate mold <NUM> is thereby produced (see <FIG>). The intermediate mold <NUM> is a rubber mold produced at an intermediate stage while manufacturing the mold for molding tire <NUM> and has a rubber part <NUM> formed of a rubber material, a reinforcing part <NUM> that reinforces the rubber part <NUM>, and a transfer part <NUM> that is a part of the rubber part <NUM>. The rubber part <NUM> and the transfer part <NUM> are molded by the tread shaping part <NUM> of the original mold <NUM>, and the tread shaping part <NUM> including the tread shape of the tire is transferred to the transfer part <NUM>. In addition, a plurality of projections <NUM> are formed on the transfer part <NUM> by the plurality of grooves 3A of the tread shaping part <NUM>, and a plurality of groove parts <NUM> are formed on the transfer part <NUM> by a plurality of projections <NUM> of the tread shaping part <NUM>.

The groove part <NUM> of the transfer part <NUM> is a gap for holding the blade <NUM> (see <FIG>) and is formed in a slit-like shape. The blade <NUM> is a plate member (a sipe blade) for molding sipe and has a molding part <NUM> for molding the sipe in the tread part of the tire, a cast-in part <NUM> that is to be cast in the mold for molding tire <NUM> and a plurality of holes <NUM> formed in the cast-in part <NUM>. The molding part <NUM> is located on one edge side of the blade <NUM>, and the cast-in part <NUM> is located on the other edge side of the blade <NUM>. The projection <NUM> (see <FIG>) of the tread shaping part <NUM> is formed in a shape corresponding to the cast-in part <NUM> of the blade <NUM>. Therefore, the groove part <NUM> of the transfer part <NUM> is formed by the projection <NUM> in a shape corresponding to the cast-in part <NUM> of the blade <NUM>.

The cast-in part <NUM> of the blade <NUM> is inserted into the groove part <NUM> of the transfer part <NUM> (see <FIG>), the cast-in part <NUM> of the blade <NUM> is thereby fitted in the groove part <NUM> and held in the transfer part <NUM> of the intermediate mold <NUM>. The molding part <NUM> of the blade <NUM> projects from the transfer part <NUM> of the intermediate mold <NUM>. In that state, the casting mold <NUM> is molded by the transfer part <NUM> of the intermediate mold <NUM>, and the casting mold <NUM> is produced (see <FIG>). The casting mold <NUM> is formed of a collapsible mold material, here it is a gypsum mold formed by gypsum. The molding part <NUM> of the blade <NUM> is embedded in the casting mold <NUM> and attached to the casting mold <NUM>.

When the casting mold <NUM> is separated from the intermediate mold <NUM>, the cast-in part <NUM> of the blade <NUM> is removed from the intermediate mold <NUM> (see <FIG>). In addition, the molding part <NUM> of the blade <NUM> is held in the casting mold <NUM>, and the casting mold <NUM> having the plurality of blades <NUM> is produced. The cast-in part <NUM> of the blade <NUM> is located outside the casting mold <NUM> and projects from the casting mold <NUM>. The casting mold <NUM> is molded into a shape corresponding to the tread shaping part <NUM> of the original mold <NUM> and the tread shape of the tire by the transfer part <NUM> of the intermediate mold <NUM>. In addition, a plurality of grooves <NUM> and land parts <NUM> are formed in the casting mold <NUM> by the plurality of projections <NUM> of the transfer part <NUM>. The land part <NUM> is partitioned by the grooves <NUM>, and the blades <NUM> are attached to a plurality of position of the land part <NUM>.

Next, the mold for molding tire <NUM> is cast using the casting mold <NUM>. Specifically, the plurality of casting molds <NUM> are produced respectively, and the plurality of casting mold <NUM> are combined in an annular shape (see <FIG>). Metal (for example, aluminum alloy) is solidified around the annular mold <NUM> (see <FIG>) and a cast metal (a mold cast metal <NUM>) of the mold for molding tire <NUM> is cast. The mold cast metal <NUM> is formed in an annular shape and includes a plurality of molds for molding tire <NUM>. A plurality of risers <NUM> are connected to the mold cast metal <NUM>. The cast-in part <NUM> of the blade <NUM> is cast in the mold for molding tire <NUM> while the mold for molding tire <NUM> (mold cast metal <NUM>) is cast using the casting mold <NUM>. The cast-in part <NUM> of the blade <NUM> is thereby fixed to the mold for molding tire <NUM>.

By destructing the casting mold <NUM>, the casting mold <NUM> is removed from the mold cast metal <NUM> of the mold for molding tire <NUM> (see <FIG>). Subsequently, the riser <NUM> is removed from the mold cast metal <NUM>, and the mold cast metal <NUM> is divided into a plurality of parts in the circumferential direction (see <FIG>). In addition, the outer surface part (outer circumferential part, end surface part, etc.) of the mold cast metal <NUM> is processed (see <FIG>). A plurality of molds for molding tire <NUM> are produced. The plurality of molds for molding tire <NUM> have the plurality of blades <NUM> respectively and are combined in an annular shape when vulcanizing (when molding) the tire. The molding part <NUM> of the blade <NUM> is located outside the mold for molding tire <NUM> and projects from the mold for molding tire <NUM>. In addition, a plurality of projection parts 1A are formed in the mold for molding tire <NUM> by the plurality of grooves <NUM> of the casting mold <NUM>.

<FIG> is a perspective view showing the original mold <NUM> of the mold for molding tire <NUM> of the 1st example and shows the disassembled original mold <NUM>. In <FIG>, the shape of the original mold <NUM> is simplified, and the original mold <NUM> of a shape different from the original mold <NUM> shown in <FIG> is shown schematically.

As shown in the figure, the original mold <NUM> has a base part <NUM> and a surface part <NUM> of a tread shaping part <NUM> thinner than the base part <NUM>. The base part <NUM> is the base part of the original mold <NUM> excluding the surface part <NUM> from the original mold <NUM>, and the surface part <NUM> is a part on the surface side of the tread shaping part <NUM> of the original mold <NUM>. In addition, the surface part <NUM> is formed in a shape corresponding to the surface shape of the tread shaping part <NUM> and includes the surface shape of the tread shaping part <NUM>. The base part <NUM> and the surface part <NUM> of the original mold <NUM> are produced separately. The original mold <NUM> is produced by forming the surface part <NUM> of the tread shaping part <NUM> and attaching the surface part <NUM> to the base part <NUM> of the original mold <NUM>.

<FIG> is a perspective view showing the base part <NUM> of the original mold <NUM> of the 1st example.

As shown in the figure, the base part <NUM> of the original mold <NUM> is a part excluding at least a part (the surface part <NUM>) on the surface side of the tread shaping part <NUM> from the original mold <NUM> and has a plurality of grooves <NUM> and a plurality of covering parts <NUM>. The base part <NUM> is produced by machining using a processing machine (for example, a NC processing machine) and is formed of a material (for example, various chemical wood (synthetic wood) and aluminum alloy) that is easy to machine and hardly subject to a dimensional change.

The groove <NUM> and the covering part <NUM> of the base part <NUM> are formed on the surface part <NUM> side (tread shaping part <NUM> side) of the base part <NUM>. The groove <NUM> of the base part <NUM> is a bottom part of the groove 3A of the tread shaping part <NUM> and is formed in a position corresponding to the groove 3A (groove of the tread part of the tire) of the tread shaping part <NUM>. The covering part <NUM> of the base part <NUM> is a smooth surface and is formed in a position corresponding to the land part 3B of the tread shaping part <NUM> (land part of the tread part of the tire). The surface part <NUM> of the tread shaping part <NUM> is attached to the covering part <NUM>, and the covering part <NUM> is covered with the surface part <NUM>. In addition, the covering part <NUM> is partitioned by the grooves <NUM>, and the groove <NUM> is formed between the covering parts <NUM>. The base part <NUM> is a block-like retainer and holds the surface part <NUM> on the covering part <NUM>.

<FIG> are perspective views showing the surface part <NUM> of the tread shaping part <NUM> of the 1st example and show the surface part <NUM> viewed from two directions. <FIG> shows the surface part <NUM> viewed from the surface side of the tread shaping part <NUM>, and <FIG> shows the surface part <NUM> viewed from the base part <NUM> side.

As shown in the figures, the surface part <NUM> of the tread shaping part <NUM> is a part containing at least a part of the tread shaping part <NUM> on the surface side and is divided into a plurality of surface pieces 61A. The surface piece 61A is a part of the surface part <NUM> of the tread shaping part <NUM> and is formed in a shape including a part of the tread shaping part <NUM> on its surface side.

The plurality of surface pieces 61A of the surface part <NUM> are shaped and formed respectively by a three-dimensional shaping method (for example, an optical shaping method, a laser sintering lamination method) that is a direct modeling method. By a three-dimensional shaping apparatus (for example, an optical shaping apparatus, a laser sintering shaping apparatus, a 3D printer), the surface piece 61A of the surface part <NUM> is produced integrally based on three-dimensional shape data. The surface piece 61A of the surface part <NUM> is formed of, for example, a photosetting resin, a thermoplastic resin, and a sintered metal corresponding to a type of the three-dimensional shaping method. Whereas the surface piece 61A of the surface part <NUM> may be a laminated product obtained by laminating paper.

The surface piece 61A of the surface part <NUM> is the land part 3B of the tread shaping part <NUM> and is formed in a surface shape corresponding to the surface shape of the land part 3B. In addition, the plurality of surface pieces 61A are divided at a position corresponding to the groove 3A of the tread shaping part <NUM> in the surface part <NUM>. The surface piece 61A of the surface part <NUM> has an attaching part <NUM> formed on the base part <NUM> side of the surface piece 61A and projections <NUM> formed projecting at the tread shaping part <NUM>. The attaching part <NUM> is a smooth surface in a shape conforming to the covering part <NUM> of the base part <NUM> and adhered to the covering part <NUM> while being overlapped with the covering part <NUM>. The attaching part <NUM> is attached to the covering part <NUM> by attaching means (for example, adhesion, joining), and the surface piece 61A of the surface part <NUM> is attached to the covering part <NUM> of the base part <NUM>. The covering part <NUM> is covered with the surface piece 61A.

The projection <NUM> is provided at a sipe position of the tire in the surface piece 61A of the surface part <NUM> and is formed in an elongated plate that extends along the sipe position. In addition, the projection <NUM> is a projectedpiece shaped corresponding to the cast-in part <NUM> of the blade <NUM> and is formed integrally with the surface piece 61A and the surface part <NUM>. Here, the plurality of projections <NUM> are formed projecting at the surface piece 61A.

<FIG> is a perspective view showing the original mold <NUM> of the mold for molding tire <NUM> of the 1st example and shows the original mold <NUM> after production.

As shown in the figure, the surface part <NUM> is formed as being divided into the plurality of surface pieces 61A, and the plurality of surface pieces 61A of the surface part <NUM> are attached to the base part <NUM>, the surface piece 61A of the surface part <NUM> and the base part <NUM> are thereby combined to produce the original mold <NUM> having the plurality of projections <NUM>. In addition, the plurality of grooves 3A and the plurality of land parts 3B are formed in the tread shaping part <NUM> of the original mold <NUM> by the surface pieces 61A of the surface part <NUM> and the base part <NUM>. The groove 3A is formed between the surface pieces 61A by a gap between the adjacent surface pieces 61A and the groove <NUM> of the base part <NUM>. The land part 3B is formed by the surface piece 61A.

The projection <NUM> is formed integrally with the surface part <NUM> (the surface piece 61A) of the tread shaping part <NUM>, so that the groove part <NUM> is formed in the transfer part <NUM> of the intermediate mold <NUM> by the projection <NUM> of the surface part <NUM> of the tread shaping part <NUM> (see <FIG>). Thereafter, the cast-in part <NUM> of the sipe molding blade <NUM> is inserted into the groove part <NUM> of the transfer part <NUM> (see <FIG>). When the blade <NUM> is produced by the press forming of a plate material, a difference may be caused between actual dimension of the blade <NUM> (for example, the dimension of outer circumferential shape, the dimension of bending shape) and a design dimension of the blade <NUM> (for example, <NUM> to <NUM> difference). In order to cope with such difference in dimension, the dimension of the projection <NUM> of the surface part <NUM> is corrected based on the actual dimension of the cast-in part <NUM> of the blade <NUM>, and the projection <NUM> is formed on the surface part <NUM> with the corrected dimension.

Before production of the surface part <NUM> of the tread shaping part <NUM>, the blade <NUM> is produced and the actual dimension of the cast-in part <NUM> of the blade <NUM> is measured. The projection <NUM> is formed on the surface part <NUM> with the actual dimension of the measured cast-in part <NUM>. The projection <NUM> is thereby corrected so as to conform to the actual dimension of the cast-in part <NUM>. Whereas the dimension of the projection <NUM> may be corrected based on past data of the difference between the actual dimension of the cast-in part <NUM> and the design dimension of the cast-in part <NUM>. In addition, when the actual dimension of the cast-in part <NUM> is the same as the design dimension, the projection <NUM> of the surface part <NUM> is formed with the design dimension of the cast-in part <NUM>.

As described above, in the method of manufacturing the mold for molding tire <NUM> of the 1st example, the original mold <NUM> can be easily produced, so that the mold for molding tire <NUM> easily manufactured. In addition, the surface part <NUM> of the tread shaping part <NUM> can be reinforced by the base part <NUM>, so that the changes in shape and dimension of the surface part <NUM> can be restrained. Even when deformation occurs in the surface part <NUM> before attaching to the base part <NUM>, the shape of the surface part <NUM> can be corrected by attaching the surface part <NUM> to the base part <NUM>. It is also possible to correspond to the tread shaping part <NUM> of a complicated shape, and the tread shaping part <NUM> can be easily formed.

By forming the surface piece 61A and the surface part <NUM> by the three-dimensional shaping method, the tread shaping part <NUM> of the original mold <NUM> can be accurately formed, and time and cost required in the production of the original mold <NUM> can be reduced. In addition, formation of a fine shape or formation of parts that are hard to process can be easily performed, so that formation efficiencies of the surface piece 61A and the surface part <NUM> can be improved.

By dividing the surface part <NUM> of the tread shaping part <NUM> into the plurality of surface pieces 61A, members to be integrally formed can be made smaller. Therefore, the surface piece 61A can be accurately formed, and deformation of the surface piece 61A while forming can be restrained. Since the surface part <NUM> is formed for each component part (surface piece 61A), the surface part <NUM> can be easily formed. By forming the projection <NUM> integrally with the surface part <NUM>, the original mold <NUM> having the projections <NUM> can be easily produced and production time of the original mold <NUM> can be shortened. It can correspond to projection <NUM> of complicated shape as well.

By correcting the dimension of the projection <NUM> based on the actual dimension of the cast-in part <NUM> of the blade <NUM>, the difference between the dimension of the projection <NUM> and the actual dimension of the cast-in part <NUM> can be reduced. As a result, the cast-in part <NUM> of the blade <NUM> can be easily inserted into the groove part <NUM> of the transfer part <NUM> of the intermediate mold <NUM>. In addition, it is possible to restrain deformation of the transfer part <NUM> by the cast-in part <NUM>, and it is also possible to restrain generation of a gap between the cast-in part <NUM> and the transfer part <NUM>.

In addition, the projection <NUM> may be formed so as not be formed integrally with the surface part <NUM> and the surface piece 61A of the tread shaping part <NUM>. For example, when the blade <NUM> is not provided in the mold for molding tire <NUM>, the projection <NUM> is not formed on the surface part <NUM> and the surface piece 61A of the tread shaping part <NUM>. In addition, a part of the tread shaping part <NUM> may be formed by the surface part <NUM>, and the entire tread shaping part <NUM> may be formed by the surface part <NUM>. The tread shaping part <NUM> may be formed by one surface part <NUM> without dividing the surface part <NUM> of the tread shaping part <NUM>.

Next, other examples (2nd to 4th examples and 1st embodiment) of the method of manufacturing mold for molding tire <NUM> will be described. Regarding the method of manufacturing the mold for molding tire <NUM> of the 2nd to 4th examples and 1st embodiment, the description of the same matters as the method of manufacturing the mold for molding tire <NUM> of the 1st example is omitted. In addition, regarding configurations of the 2nd to 4th examples and 1st embodiment, terms of the configurations corresponding to the configurations of the 1st example are used the same terms as those of the configurations of the 1st example.

<FIG> is a perspective view showing the original mold <NUM> of the mold for molding tire <NUM> of the 2nd example and shows the decomposed original mold <NUM>. <FIG> is a perspective view showing a base part <NUM> of the original mold <NUM> of the 2nd example.

As shown in the figure, the base part <NUM> of the original mold <NUM> has a convex part <NUM> formed in the covering part <NUM>. The convex part <NUM> is a mounting part to which the surface part <NUM> (a surface piece 61B) of a tread shaping part <NUM> is mounted and is formed in each of a plurality of the covering parts <NUM> of the base part <NUM>. In addition, the convex part <NUM> is formed in a part excluding the edge part of the covering part <NUM> and projects toward the surface part <NUM>. A plurality of convex parts <NUM> are convexly formed in parts on the surface part <NUM> side of the base part <NUM>.

<FIG> are perspective views showing the surface part <NUM> of the tread shaping part <NUM> of the 2nd example and show the surface part <NUM> viewed from two directions. <FIG> shows the surface part <NUM> viewed from the surface side of the tread shaping part <NUM>, and <FIG> shows the surface part <NUM> viewed from the base part <NUM> side. <FIG> is a perspective view showing the original mold <NUM> of the mold for molding tire <NUM> of the 2nd example and shows the original mold <NUM> after production.

As shown in the figures, the surface part <NUM> has the concave part <NUM> formed in the attaching part <NUM> of the surface piece 61B. The surface piece 61B of the 2nd example is formed as with the surface piece 61A of the 1st example, except for the concave part <NUM>. The concave part <NUM> is a fitting part to be fitted in the convex part <NUM> of the base part <NUM> and is formed on each of the plurality of surface pieces 61B of the surface part <NUM>. In addition, the concave part <NUM> is formed in a part excluding the edge part of the attaching part <NUM> and is opened toward the base part <NUM>. The concave part <NUM> is concavely formed at a part on the base part <NUM> side of the surface piece 61B of the surface part <NUM>.

The base part <NUM> having the convex part <NUM> is formed, and the surface part <NUM> (here, the surface piece 61B of the surface part <NUM>) of the tread shaping part <NUM> having the concave part <NUM> is formed. The concave part <NUM> formed on the surface part <NUM> is fitted into the convex part <NUM> formed in the base part <NUM>, so that the surface part <NUM> is attached to the base part <NUM>. The concave part <NUM> is attached to the convex part <NUM> by fitting, so that the surface piece 61B of the surface part <NUM> is mounted to the convex part <NUM>. The original mold <NUM> is thereby produced.

By fitting of the convex part <NUM> into the concave part <NUM>, the surface part <NUM> (the surface piece 61B) of the tread shaping part <NUM> can be easily attached to the base part <NUM> of the original mold <NUM>. When deformation occurs in the surface piece 61B and the surface part <NUM> before attaching to the base part <NUM>, the shape of the surface piece 61B and the surface part <NUM> can be corrected by the convex part <NUM>. Due to formation of the concave part <NUM>, the surface piece 61B of the surface part <NUM> can be made thin. Therefore, the surface piece 61B of the surface part <NUM> can be easily formed by the three-dimensional modeling method, and the surface piece 61B of the surface part <NUM> can be accurately formed.

<FIG> is a perspective view showing the original mold <NUM> of the mold for molding tire <NUM> of the 3rd example and shows the decomposed original mold <NUM>. <FIG> is a perspective view showing the base part <NUM> of the original mold <NUM> of the 3rd example.

As shown in the figure, the base part <NUM> of the original mold <NUM> has convex parts <NUM> as with the base part <NUM> of the 2nd example.

<FIG> are perspective views showing the surface part <NUM> of the tread shaping part <NUM> of the 3rd example and show the surface part <NUM> viewed from two directions. <FIG> shows the surface part <NUM> viewed from the surface side of the tread shaping part <NUM>, and <FIG> shows the surface part <NUM> viewed from the base part <NUM> side. <FIG> is a perspective view showing the original mold <NUM> of the mold for molding tire <NUM> of the 3rd example and shows the original mold <NUM> after production.

As shown in the figures, the surface piece 61C of the surface part <NUM> has the plurality of land parts, the groove shaping parts <NUM> formed between adjacent land parts <NUM>, and the concave part <NUM> formed in an attaching part <NUM>. The land part <NUM> of the surface piece 61C corresponds to the surface piece 61B of the 2nd example, and the concave part <NUM> is formed on the attaching part <NUM> of the land part <NUM>. The groove shaping part <NUM> is a part corresponding to the groove 3A of the tread shaping part <NUM>. The land part <NUM> and the groove shaping part <NUM> are alternately formed and continuous with each other.

<FIG> is a perspective view showing the original mold <NUM> of the mold for molding tire <NUM> of the 4th example and shows the decomposed original mold <NUM>. <FIG> is a perspective view showing the base part <NUM> of the original mold <NUM> of the 4th example.

As shown in the figure, the base part <NUM> of the original mold <NUM> has the convex part <NUM> as with the base part <NUM> of the 3rd example.

<FIG> are perspective views showing the surface part <NUM> of the tread shaping part <NUM> of the 4th example and show the surface part <NUM> viewed from two directions. <FIG> shows the surface part <NUM> viewed from the surface side of the tread shaping part <NUM>, and <FIG> shows the surface part <NUM> viewed from the base part <NUM> side. <FIG> is a perspective view showing the original mold <NUM> of the mold for molding tire <NUM> of the 4th example and shows the original mold <NUM> after production.

As shown in the figures, a surface piece 61D of the surface part <NUM> is formed in a shape that the surface piece 61C of the 3rd example is divided by a groove shaping part <NUM>. In this way, the surface part <NUM> of the tread shaping part <NUM> can be divided into surface pieces of various shapes.

<FIG> is a perspective view showing a part of the surface part <NUM> of the tread shaping part <NUM> of the 1st embodiment and shows a surface piece 61E of the surface part <NUM>.

As shown in the figure, the surface piece 61E of the surface part <NUM> is formed as with the surface piece 61A of the 1st example or the surface piece 61B of the 2nd example, except for the projection <NUM>. The projection <NUM> has a thin part 4A on the root side (base end side). The thin part 4A of the projection <NUM> is formed thinner than the other parts of the projection <NUM> and is formed along the root of the projection <NUM>.

The thin part 4A that is thinner than the cast-in part <NUM> of the blade <NUM> is formed in a part on the root side of the projection <NUM> of the surface part <NUM>. In addition, by the thin part 4A of the projection <NUM>, a narrow part that is narrower in width than the thickness of the cast-in part <NUM> is formed in the groove part <NUM> (see <FIG>, <FIG>) of the transfer part <NUM> of the intermediate mold <NUM>. The thin part 4A is formed in whole or in part of the root side part of the projection <NUM>, and the narrow part of the groove part <NUM> is formed in whole or in part on the opening side of the groove part <NUM>.

By forming the narrow part in the groove part <NUM>, the cast-in part <NUM> of the blade <NUM> can be firmly fitted into the groove part <NUM> of the transfer part <NUM>, and a gap (a gap in the groove part <NUM>) can be restrained from generating between the cast-in part <NUM> and the transfer part <NUM>. Accordingly, when forming the casting mold <NUM> by the transfer part <NUM>, burrs of the casting mold <NUM> can be restrained from generating around the cast-in part <NUM>. In addition, the casting mold <NUM> can be accurately formed.

It is preferable that the thin part 4A is formed with a width of <NUM>. <NUM> to <NUM> along the root of the projection <NUM>. When the width of the thin part 4A is narrower than <NUM>. <NUM>, effect of restraining generation of the gap in the groove part <NUM> is likely to be affected. When the width of the thin part 4A is wider than <NUM>, amount of deformation of the transfer part <NUM> due to the cast-in part <NUM> of the blade <NUM> is likely to increase. By contrast when the width of the thin part 4A is <NUM>. <NUM> to <NUM>, the generation of gap in the groove part <NUM> and deformation of the transfer part <NUM> can be restrained.

Claim 1:
A method of manufacturing a mold for molding a tire (<NUM>) comprising: producing an original mold (<NUM>) having a tread shaping part (<NUM>) including a tread shape of the tire, producing an intermediate mold (<NUM>) having a transfer part (<NUM>) to which the tread shaping part of the original mold is transferred, forming a casting mold (<NUM>) by the transfer part of the intermediate mold, and casting the mold for molding tire using the casting mold,
wherein the original mold is produced by forming a surface part (<NUM>) of the tread shaping part and attaching the surface part to a base part (<NUM>) of the original mold, wherein the surface part is divided into a plurality of surface pieces (61A-61E) formed in a surface shape corresponding to a surface shape of a land part (3B) of the tread shaping part (<NUM>) and divided at a position corresponding to a groove (3A) of the tread shaping part (<NUM>),
wherein a projection of a shape corresponding to a cast-in part (<NUM>) of a blade (<NUM>) for molding sipe is formed integrally with the surface part of the tread shaping part, a groove part (<NUM>) is formed in the transfer part of the intermediate mold by the projection of the surface part, and the cast-in part of the blade is inserted into the groove part of the transfer part;
a thin part (4A) that is thinner than the cast-in part of the blade is formed in a part on a root side of the projection of the surface part, and a narrow part that is narrower in width than the thickness of the cast-in part of the blade is formed in the groove part of the transfer part by the thin part of the projection of the surface part.