JP2000229322A - Mold for vulcanizing and forming tire and its production, pneumatic tire formed by using mold and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold for vulcanizing and forming a tire by which a gap having necessary exhaust performance is easily formed in an arbitrary position on a formed face and thereby formation of a spew is avoided and the outward appearance of the tire being a product is made good and also generation of a defective at the time of vulcanization and formation is decreased. SOLUTION: The mold for forming a tire is equipped with a plurality of pieces 3 in which the tread pattern of the tire is formed at every section. These pieces 3 are fitted to a back block 4 and provided in a ring shape. Respective pieces 3 are constituted of piece blocks 3a, 3b of a plurality of layers in which metallic material is separated into shots of a plurality of times by die-cast casting. Minute gaps due to solidification shrinkage of the metallic material are formed in the cast joining part between the piece blocks 3a, 3b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire vulcanization mold having a plurality of pieces for molding a tread pattern of a tire for each section and a method of manufacturing the same, and more particularly to a method for avoiding formation of spews. Tire vulcanization molding mold and method for producing the same, and a pneumatic tire molded using the mold, so that the appearance of the product tire is improved and the occurrence of defective products during vulcanization molding is reduced. The present invention relates to the manufacturing method.

[0002]

2. Description of the Related Art Conventionally, a sector mold used as one of tire vulcanization molding dies is formed by adjoining a plurality of pieces having irregularities corresponding to a profile of a tread portion of a product tire to each other. One sector is constituted by being mounted on the back block, and a plurality of sectors are interconnected to form an annular sector mold.

[0003] At the time of tire vulcanization molding, air remains or gas is generated between the outer peripheral surface of the tire and the molding surface of the mold, and these air and gas form minute dents on the surface of the product tire. It is known to form and cause product defects. For this reason, a through hole for venting, called a vent hole, and a groove for exhausting, called a vent groove, are conventionally formed on the molding surface of the mold.

However, a rubber material flows into these vent holes and vent grooves at the time of tire vulcanization and forms spews (burrs, whisker-like rubber projections) on the surface of the product tire. For this reason, a finishing operation for removing the spew after the molding is necessary, and after removing the spew, there is a problem that the trace of the spew is left to impair the appearance of the tire product or increase the noise of the tire.

[0005] In recent years, tires with excellent appearance have been developed.
In addition, for the purpose of reducing the occurrence of defective products during tire vulcanization molding, a purees mold having a slit vent formed of a minute gap without forming a vent hole or a vent groove on a molding surface is used.

As the pures mold, for example, JP-A-4-223108 (title of the invention: a mold for vulcanizing an uncured tire carcass, a method for producing the mold, and the mold were used. Tire vulcanization method)
No. -24423 (Title of Invention: Mold for Tire Vulcanization Molding and Manufacturing Method Thereof) and the like have been proposed.

The former invention is a method of assembling a back block in which a tread pattern of a tire is divided for each pitch, and sucking air existing between the tire and a mold from outside through a gap provided between the back blocks. is there. In the latter invention, a dissimilar metal (SS400) is cast into the base metal (aluminum) of the pattern piece, and the gap formed by the difference in linear thermal expansion coefficient at the time of tire vulcanization molding (160 ° C) is used. This is a method of discharging air.
In addition, as a slit vent mold, there is a method of removing air by providing a step between pieces by machining or inserting a spacer between pieces.

However, the above-described invention has a problem that it is difficult to secure proper air bleeding at an arbitrary position, and a vacuum device or the like is necessarily required as an exhaust means. Further, in the above invention, a sufficient volume is required to form a gap due to a difference in linear thermal expansion coefficient, and it is difficult to secure a required gap amount at an arbitrary position. It is difficult to pull out.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to easily form a gap having a required exhaust performance at an arbitrary position on a molding surface, thereby avoiding the formation of spews and the production tire. A tire vulcanization molding die and a method for producing the same, and a pneumatic tire molded using the mold and a method for improving the appearance and reducing the occurrence of defective products during vulcanization molding It is to provide a manufacturing method.

[0010]

According to the present invention, there is provided a tire vulcanization mold having a plurality of pieces for forming a tread pattern of a tire for each section, and the plurality of pieces are back-blocked. A tire molding die mounted in a ring and arranged in an annular shape, wherein each of the pieces is constituted by a plurality of layered piece blocks formed by laminating a metal material into a plurality of shots by die casting. A minute gap is formed in the joint between the piece blocks by solidification shrinkage of the metal material.

Further, in the method for producing a tire vulcanization mold according to the present invention, a molten metal material is cast into the first mold in a first shot step by die casting to correspond to a tread pattern of a tire. A first piece block partially provided with a molding surface is formed, and in the second shot step, the same kind of metal material melted in the second mold while the first piece block is disposed in the second mold. The second piece block which complements the molding surface is formed on the first piece block by casting, and a minute gap due to solidification shrinkage of the metal material is formed in a joint portion of the first piece block and the second piece block. Is formed.

According to the present invention, when a plurality of pieces of piece blocks constituting a piece are cast from the same type of metal material and laminated, fine gaps are formed in the joint portion between the piece blocks due to solidification shrinkage of the metal material. Is done. The minute gap due to the solidification and shrinkage of the metal material exhibits an exhausting performance for satisfactorily discharging only the air and gas in the mold without allowing the rubber material to flow out. Therefore, it is possible to easily form a gap having the required exhaust performance as a pureeless mold at an arbitrary position on the molding surface based on the arrangement of the cast joint, thereby avoiding the formation of the spew while vulcanizing molding. , The occurrence of defective products can be reduced.

Further, the step of removing the spew after vulcanizing the tire is not required, and the appearance of the tire can be improved without leaving traces of the spew on the tire surface, which deteriorate tire noise.

Further, the pneumatic tire according to the present invention is characterized in that a tread pattern having no trace of spew is formed on the tire surface by using the above-described mold for vulcanization of a tire.

Further, the method of manufacturing a pneumatic tire according to the present invention is characterized in that a tread pattern having no trace of spew on a tire surface is formed by using the tire vulcanization mold.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 illustrates one sector constituting a split-type tire vulcanization mold (sector mold) embodying the present invention. This one sector 1
Is configured by mounting a plurality of pieces 3 having irregularities 2 corresponding to a profile of a tread portion of a product tire on a back block 4 so as to be adjacent to each other.

As shown in FIG. 2, a plurality of sectors 1 are arranged in a ring to form a sector mold 1A. In the present embodiment, eight sectors 1 constitute one set of sector molds 1A, but the number of sectors is not particularly limited. When vulcanizing the tire W using the sector mold 1A, a plurality of sectors 1 are mounted on a conventionally known mold supporting device 5 as shown in FIG.

In the mold supporting apparatus 5, an outer ring 7 is suspended below the outer peripheral edge of a disk-shaped support plate 6, and the sector 1 is mounted on a tapered surface 8 inside the outer ring 7 via a segment 9. It has a configuration. The segment 9 is slidable in the vertical direction with respect to the tapered surface 8, and expands and contracts the sector 1 in the radial direction of the mold based on the vertical movement of the support plate 6.

At the top of the sector 1, an upper plate 10
An upper mold side mold 11 that can be moved up and down through the upper mold is provided. On the other hand, below the sector 1, a lower mold side mold 13 fixed on the base plate 12 is provided.

At the time of vulcanizing the tire W, the support plate 6 is moved downward to slide the segment 9 against the tapered surface 8, thereby moving each sector 1 in the centripetal direction (toward the center of the mold). , Upper mold side mold 11
And the lower mold side mold 13 are brought into close contact with the upper and lower ends of each sector 1. When vulcanization is completed,
By moving the support plate 6 upward, each sector 1 is moved outward, and the upper die side mold 11 is moved upward to release the molded tire W.

As shown in FIG. 1, when the tread pattern of the tire is divided into a plurality of sections at a fixed pitch or an arbitrary pitch, the plurality of pieces 3 mounted on the back block 4 It is designed to be molded. The piece 3 is composed of a first piece block 3a and a second piece block 3b formed by laminating a metal material into a plurality of shots by die casting. However, in the present embodiment, the number of shots of die casting is two, but the number of shots is not particularly limited.

Metal material cast by multiple shots (first piece block 3a and second piece block 3b)
In the joint portion X, a fine gap h is formed by solidification shrinkage of a metal material as shown in FIG. Note that, as the cast metal material in the present embodiment, the same metal of aluminum is used for both the first piece block 3a and the second piece block 3b. The minute gap h formed by solidification shrinkage of the metal material is desirably 0.005 to 0.08 mm, preferably 0.02 mm. This gap h is 0.005 mm
If it is less than 0.08 mm, exhaust performance will be insufficient. Conversely, if it exceeds 0.08 mm, it will be easy to form spew. Further, by using the same kind of metal material as the metal material for casting of the first piece block 3a and the second piece block 3b, it is possible to prevent the gap h from changing at the tire vulcanization molding temperature.

Further, in the embodiment of the present invention, the exhaust holes 14 communicating with the minute gaps h are provided below the molding surface of the piece 3.
Are formed. The exhaust hole 14 communicates with the back side of the piece 3 and discharges air and gas remaining in the mold to the atmosphere.

Next, a method for manufacturing a tire vulcanization mold according to the present invention will be described with reference to FIGS.

First, as a pre-process for manufacturing a tire vulcanization molding die, a first split die 20 as a pattern insert die used in a first shot process of die casting shown in FIG.
a, 20b and a second split mold 2 as a pattern insert mold used in a second shot process of die casting shown in FIG.
1a and 21b are manufactured in advance. 4 and 5, the molten metal material is pressed by a piston 22 and injected into a pattern nest through a gate 23.

Using the first split molds 20a and 20b and the second split molds 21a and 21b, a piece 3 of a tire vulcanizing mold can be manufactured by the following steps. First shot casting process.

In the first shot casting step, molten metal (aluminum or an aluminum alloy in this embodiment) is poured from the gate 23 using the first split molds 20a and 20b of the first shot insert mold shown in FIG. By casting, the first piece block 3a partially provided with a molding surface corresponding to the tread pattern of the tire W and having an area for laminating the second piece block 3b is cast.

After the casting of the first piece block 3a,
The first piece block 3a is machined. For example, the first piece block 3a is prevented from disassembling the first piece block 3a and the second piece block 3b of the second shot.
Is preferably processed into an undercut shape. Also,
If necessary, the type, shape and size of the tread pattern can be changed and processed. Further, it is processed so that the molten metal flows into the thin bone of the tread pattern, or processed so that a sipe can be inserted. Second shot casting process.

The first piece block 3a manufactured in the first shot casting process is connected to the second split mold 21 as shown in FIG.
a, 21b, and the mold is clamped so that the molding surface of the first piece block 3a and the inner surface of the mold 21a are in close contact with each other. Then, a second piece block 3b that complements the molding surface of the tread pattern is cast. By firmly performing the mold clamping, the molten metal of the second shot is prevented from flowing between the molding surface of the first piece block 3a and the inner surface of the mold 21a, and the vent mechanism by the gap h is used for the piece 3. Can be reliably exposed to the molding surface. As shown in FIGS. 7 and 9, a piece 3 composed of a laminate of the piece blocks 3a and 3b is obtained from the second shot casting step. In FIG. 9, a hatched portion indicates an exposed portion of the second piece block 3b, and other portions indicate exposed portions of the first piece block 3a.

The casting conditions for forming a fine gap h in the joint portion X of the piece blocks 3a, 3b due to solidification shrinkage of the metal material in the second shot are set based on the following (a) to (d). good. (a) Injection speed of die casting In general, the higher the piston speed and gate speed in die casting, the more sound castings can be made with less casting defects in the tread pattern. The gap h
(Slits) are less likely to be formed. Therefore, the injection speed of the die casting is preferably low.

Further, in die casting, there is a characteristic that the slower the injection speed, the less air is entrained in the molten metal material, and the higher the injection speed, the more beautiful the surface shape. Therefore, in the present invention, after starting at a low injection speed, It is good to gradually increase the injection speed and reach the stroke end at a high speed. (b) Gate (gate) A thick gate (for example, 3.5 mm or more) transmits injection pressure more than necessary, so that solidification shrinkage does not occur and a gap h (slit) cannot be formed. Therefore, the thickness of the gate is 0.8-2.5
mm is the best, and the molten metal flows uniformly in the groove,
And it is good to provide in the place where it flows easily. (c) Hot metal temperature of molten metal Generally, the temperature is 650 to 720 ° C, but a low hot water temperature is preferable as long as it can be cast. When the temperature of the hot water is high, the pattern insert and the cast product come into close contact with each other and do not release, and no gap h is formed. (d) Injection pressure Generally, the injection pressure of a piston of a sound die-cast product is 600 kgf / cm ^{2 to} 1,200 kgf / cm ² . This injection pressure is optimal for the casting pressure of the first shot,
Not suitable for shot casting pressure.

That is, if a high pressure is applied at the time of the second shot, solidification shrinkage of the metal does not occur, and it becomes difficult to generate a minute gap h in the joint X. Therefore, the injection pressure during the second shot is about 50% of the first shot, that is, 30%.
It is preferably set to 0 kgf / cm ^{2 to} 800 kgf / cm ² .

Naturally, various casting conditions are complicatedly related. However, if the gap amount is increased at a low injection pressure (for example, 0.
08mm or more), the degree of occurrence of rubber overflow in the slit vent increases. Further, when a high injection pressure is applied, the metal of the joint portion X is welded, the gap amount approaches zero as much as possible, and the air bleeding effect cannot be expected. A step of processing an exhaust hole communicating with the gap.

After laminating the first piece block 3a and the second piece block 3b by die casting to produce the piece 3, the exhaust hole 14 communicating with the fine gap h is mechanically formed below the molding surface of the tread pattern. Process. Leak test process.

The piece 3 is immersed in a water tank or the like to determine whether or not the slit vent including the gap h is formed reliably.
Apply 2.0 kgf / cm ² air pressure to check the leak condition and complete the puree piece.

The plurality of pieces 3 obtained as described above are mounted on the back block 4 without securing a gap with a spacer or the like, and the sectors 1 are assembled by bringing all pieces into close contact with each other and welding. However, the sector 1 may be assembled without performing welding between the pieces. Then, by incorporating the sector 1 into the segment 9, the preparation of the tire vulcanization molding machine is completed.

According to the present invention, when the first piece block 3a and the second piece block 3b are cast from the same kind of metal material and laminated as described above, the piece made of the cast metal material of the first shot and the second shot is used. Since a minute gap h is formed in the joint portion X between the blocks 3a and 3b due to solidification shrinkage of the metal material, special processing is performed on the pieces when assembling the sector 1, and members such as spacers are provided between the pieces. The gap h for exhaust can be easily formed without intervening.

When vulcanization molding of a pneumatic tire is performed using the tire vulcanization molding die of the present invention, occurrence of defective products during vulcanization molding can be reduced while avoiding formation of spews. Moreover, a step of removing the spew after vulcanizing the tire is not required, and the appearance of the tire can be improved without leaving traces of the spew on the tire surface that deteriorate the tire noise.

In the above embodiment, the first shot and the second shot of die casting use the same kind of aluminum alloy for die casting. Is possible. As a material of the back block 4, it is preferable to use an aluminum alloy or steel.

In the above embodiment, a case was described in which a sector mold using a plurality of sectors was used as a split-type tire vulcanization mold, but the present invention is divided into two parts as shown in FIGS. The present invention can also be applied to a tire vulcanization molding die.

That is, FIG. 10 shows the upper and lower two-part mold 1B.
And the upper mold 15 and the lower mold 16 respectively.
It consists of.

FIG. 11 is a view taken in the direction of the arrows BB in FIG. 10, and FIG. 12 is a sectional perspective view taken in the direction of the arrows CC in FIG. Description is omitted. Upper mold 15 and lower mold 16
Are provided with bucklings 17 and 18 for molding from the tread portion to the side portion of the tire, respectively.
A plurality of pieces 3 are mounted on the tread molding portions 7 and 18, respectively.

As shown in FIG. 12, the upper and lower two-piece mold 1B also comprises a first piece block 3a and a second piece block 3b in which pieces 3 are laminated by die casting, and the piece blocks 3a, 3b
By forming a fine gap due to solidification shrinkage of the metal material in the joint portion between the joints, a slit vent required as a pureeless mold can be easily provided at an arbitrary position on the molding surface.

[0045]

The present invention is configured as described above.
It has the following excellent effects.

When casting and laminating pieces with the same kind of metal material,
A minute gap is formed in the joint between the piece blocks made of the cast metal material of the first shot and the second shot due to the solidification shrinkage of the metal material of the second shot, and this gap is used as a vent mechanism of the Spyless mold Therefore, there is no need to create a gap between pieces when assembling a sector or the like.

By forming the piece blocks of a plurality of layers from the same metal material, it is possible to confirm the gap amount of the joint at room temperature, so that it is possible to guarantee the exhaust performance required as a pureeless mold.

The gap can be set at any desired position based on the arrangement of the joints, and the amount of the gap can be easily controlled based on the casting conditions for the second shot.

Since a necessary and sufficient exhaust circuit can be provided as a pureeless mold, a conventional vacuum circuit is unnecessary.

Since the above-mentioned gap satisfactorily discharges air and gas in the mold without allowing outflow of the rubber material, it is possible to reduce the generation of defective tires during vulcanization molding while avoiding the formation of spews. Can be.

The step of removing the spew after vulcanization of the tire is not required, and the appearance of the tire can be improved without leaving traces of the spew on the tire surface, which deteriorate tire noise.

[Brief description of the drawings]

FIG. 1 is a perspective view of one sector constituting a split-type tire vulcanization molding die (sector mold) embodying the present invention.

FIG. 2 is an explanatory diagram of configuring a sector mold by connecting a plurality of sectors to each other to form an annular shape.

FIG. 3 is a sectional view in which a sector mold is mounted on a mold supporting device.

FIG. 4 is an explanatory diagram of a manufacturing process of a first piece block cast by a first shot of die casting.

FIG. 5 is an explanatory diagram of a manufacturing process of a second piece block cast by a second shot of die casting.

FIG. 6 is an enlarged cross-sectional view illustrating a gap in a portion A of FIG. 5;

FIG. 7 is a sectional view of a piece obtained by integrally casting a first piece block and a second piece block.

FIG. 8 is an enlarged sectional view of an exhaust hole communicating with a gap in a portion B in FIG. 7;

FIG. 9 is a plan view of a piece obtained by integrally casting a first piece block and a second piece block.

FIG. 10 is a cross-sectional view of a two-part mold for vulcanization molding of a tire according to the present invention.

FIG. 11 is a side view as viewed in the direction of arrows BB in FIG. 10;

FIG. 12 is a cross-sectional perspective view taken along the line CC of FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sector 1A Sector mold 1B Upper and lower two-part mold 2 Unevenness 3 pieces 3a First piece block 3b Second piece block 4 Back block 5 Mold support device 6 Support plate 7 External ring 8 Inner taper surface 9 Segment 10 Upper plate 11 Mold side mold 12 Base plate 13 Lower mold side mold 14 Exhaust hole W Tire X Spliced part h Gap 20a, 20b First split mold 21a, 21b Second split mold 22 Piston 23 Gate 15 Upper mold 16 Lower mold 17 Upper buckling 18 Lower buckling

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // B29K 21:00 105: 24 B29L 30:00

Claims (10)

[Claims] 1. A tire molding die having a plurality of pieces for molding a tread pattern of a tire for each section, wherein the pieces are mounted on a back block and arranged in an annular shape. The piece was composed of a multi-layered piece block formed by laminating a metal material into a plurality of shots by die casting, and a fine gap was formed in a joint portion between the piece blocks due to solidification shrinkage of the metal material. Mold for tire vulcanization molding. 2. The tire vulcanization mold according to claim 1, wherein the plurality of pieces of piece blocks are made of the same metal material. 3. The tire vulcanization mold according to claim 1, wherein each of the pieces is constituted by a two-layer piece block. 4. The tire vulcanization mold according to claim 1, wherein a minute gap formed by solidification shrinkage of the metal material is 0.005 to 0.08 mm. 5. The tire vulcanization mold according to claim 1, wherein an exhaust hole communicating with the minute gap is formed below the molding surface of the piece. 6. A molten metal material is cast into a first mold in a first shot step by die casting to form a first piece block partially provided with a molding surface corresponding to a tread pattern of a tire. In a second shot step, the same type of molten metal material is cast into the second mold while the first piece block is arranged in the second mold, and the molding surface is formed on the first piece block. A method of manufacturing a tire vulcanization molding die for forming a complementary second piece block and forming a fine gap in the joint portion of the first piece block and the second piece block by solidification shrinkage of the metal material. 7. The tire vulcanizing mold according to claim 6, wherein the first piece block formed in the first shot step is machined into an undercut shape and then subjected to a second shot step. Method. 8. The injection pressure in the first shot step is set to 600 to 1,200 kgf / cm ² , while the injection pressure in the second shot step is set to 300 to 800 kgf / cm ^2. A method for producing a tire vulcanization molding die according to claim 7. 9. A pneumatic tire obtained by molding a tread pattern having no trace of spew on a tire surface using the tire vulcanization mold according to any one of claims 1 to 5. 10. A method for manufacturing a pneumatic tire, comprising forming a tread pattern having no trace of spew on a tire surface by using the tire vulcanization mold according to any one of claims 1 to 5.