CN112672867B

CN112672867B - Method for manufacturing mold for tire

Info

Publication number: CN112672867B
Application number: CN201980058732.7A
Authority: CN
Inventors: 石原泰之
Original assignee: Bridgestone Corp
Current assignee: Bridgestone Corp
Priority date: 2018-09-06
Filing date: 2019-09-03
Publication date: 2023-10-17
Anticipated expiration: 2039-09-03
Also published as: WO2020050267A1; CN112672867A; JP7303201B2; JPWO2020050267A1

Abstract

The present invention provides a plurality of mold pieces capable of forming a slit vent, which can easily form a plurality of mold pieces, and can improve the manufacturing efficiency of a mold for a tire. The mold sheet forms the tire with the forming portions in a state in which the slit exhaust ports are formed between the slit forming portions. A plurality of mold pieces are formed from a mold blank (30). A plurality of dividing grooves (33) wider than the slit exhaust ports are formed along dividing positions of the plurality of mold pieces on the back surface portion (31) side of the mold material (30). A die blank (30) is cut by a laser beam at the bottom of the plurality of dividing grooves (33), thereby dividing the plurality of die pieces and forming slit forming portions on the forming portion sides of the plurality of die pieces.

Description

Method for manufacturing mold for tire

Technical Field

The present invention relates to a method for manufacturing a tire mold having a plurality of mold segments.

Background

In a tire mold having a plurality of mold pieces, the plurality of mold pieces are combined into a ring shape, and the plurality of mold pieces are used to mold a tire. The tire is vulcanized in a state of being pressed against the plurality of mold pieces. At this time, air may be trapped between the tire and the mold sheet. In particular, in the case of a mold sheet for molding a tread portion of a tire, a closed space is formed between the mold sheet and the tire due to a protrusion of the mold sheet corresponding to a groove of the tire, and thus air is easily sealed.

In order to prevent air from being sealed in, the tire mold generally includes an air discharge portion (exhaust portion) through which air is discharged. However, when the air discharge portion is a vent hole, rubber enters the vent hole, and thus an elongated rubber (whisker) is formed in the tire. Accordingly, conventionally, there has been known a method for manufacturing a tire vulcanization molding die in which air is discharged from a gap (slit vent) formed between opposed portions of a plurality of flaps (die pieces) instead of a vent hole (see patent document 1).

In the conventional method for manufacturing a tire vulcanization molding die described in patent document 1, a wire electric discharge machine is used to cut a tread ring, and a plurality of die pieces are divided. The opposing portion of the die sheet is formed in a shape (for example, a curved surface shape) that can be formed by movement of the wire. Therefore, in order to form the opposing portion of the die into a shape suitable for the discharge of air (for example, a shape having a discharge groove for air), the opposing portion of the die needs to be processed again by a processing machine, which takes labor and time in forming the die. In addition, since the processing margin of the die piece increases, the waste of the blank of the die piece also increases.

In recent years, in order to further improve the performance of a tire, the tread pattern of the tire has become complicated, for example, a curved groove having a large inclination with respect to the tire circumferential direction or inclination with respect to the tire width direction has been used. In such a tire, there is a possibility that a pattern shift is easily generated in the opposing portion of the mold sheet, and a variation is generated in the width of the slit vent. Thus, the labor and time required for forming the mold piece increase, and the manufacturing efficiency of the tire mold also decreases.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 5-220753

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to easily form a plurality of mold pieces capable of forming slit exhaust ports and to improve the manufacturing efficiency of a tire mold.

Solution for solving the problem

The present invention provides a method for manufacturing a mold for a tire, in which a plurality of mold pieces are formed by a mold blank, and the plurality of mold pieces are used for forming a tire by a forming part in a state that a slit vent is formed between slit forming parts of the plurality of mold pieces. The method for manufacturing the tire mold comprises the following steps: forming a plurality of dividing grooves wider than the slit exhaust ports along dividing positions of the plurality of die pieces on the back surface side of the die blank; and cutting the die blank by laser at the bottoms of the plurality of dividing grooves, thereby dividing the plurality of die pieces and forming slit forming portions at the forming portion sides of the plurality of die pieces.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a plurality of mold pieces capable of forming slit exhaust ports can be easily formed, and the manufacturing efficiency of the tire mold can be improved.

Drawings

Fig. 1 is a perspective view showing a tire mold according to embodiment 1.

Fig. 2 is a perspective view showing a die according to embodiment 1.

Fig. 3 is a perspective view showing the die of embodiment 1 after being disassembled.

Fig. 4 is a perspective view showing a mold sheet according to embodiment 1.

Fig. 5 is a perspective view showing a plurality of die pieces provided in the die of embodiment 1.

Fig. 6 is a perspective view showing a process of manufacturing a tire mold according to embodiment 1.

Fig. 7 is a perspective view showing a process of manufacturing a tire mold according to embodiment 1.

Fig. 8 is a perspective view showing a process of manufacturing the tire mold according to embodiment 1.

Fig. 9 is a perspective view showing a process of manufacturing a tire mold according to embodiment 1.

Fig. 10 is a perspective view showing a process of manufacturing a tire mold according to embodiment 1.

Fig. 11 is a perspective view showing a process of manufacturing a tire mold according to embodiment 1.

Fig. 12 is a perspective view showing a process of manufacturing a tire mold according to embodiment 1.

Fig. 13 is a perspective view showing a process of manufacturing a tire mold according to embodiment 1.

Fig. 14 is a perspective view showing a die according to embodiment 2.

Fig. 15 is a perspective view showing the die of embodiment 2 after disassembly.

Fig. 16 is a perspective view showing a mold sheet according to embodiment 2.

Fig. 17 is a perspective view showing a plurality of die pieces provided in the die of embodiment 2.

Fig. 18 is a perspective view showing a process of manufacturing a tire mold according to embodiment 2.

Fig. 19 is a perspective view showing a process of manufacturing a tire mold according to embodiment 2.

Fig. 20 is a perspective view showing a process of manufacturing a tire mold according to embodiment 2.

Fig. 21 is a perspective view showing a process of manufacturing a tire mold according to embodiment 2.

Fig. 22 is a perspective view showing a process of manufacturing a tire mold according to embodiment 2.

Detailed Description

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

In the method for manufacturing a tire mold according to the present embodiment, a mold blank is processed, and a plurality of mold pieces are manufactured from 1 mold blank. The tire mold is a mold for molding a tire, and is used for vulcanizing the tire. The tire (green tire) is molded and vulcanized by a tire mold. Hereinafter, a plurality of embodiments of a method for manufacturing a tire mold will be described in order.

(embodiment 1)

Fig. 1 is a perspective view showing a tire mold 1 according to embodiment 1, and shows the structure of the tire mold 1 in perspective. Fig. 1 a shows the tire mold 1 in an open state, and fig. 1B shows the tire mold 1 in a closed state.

As shown in the figure, the tire mold 1 is an annular outer mold for molding an outer surface of a tire, and is provided in a tire molding apparatus (tire vulcanizing apparatus). The tire mold 1 surrounds an annular tire, and forms an outer peripheral portion including a tread portion of the tire. Regarding the direction of the tire mold 1, the width direction of the tire mold 1 (mold width direction W) coincides with the tire width direction, and the circumferential direction of the tire mold 1 (mold circumferential direction S) coincides with the tire circumferential direction. The radial direction of the tire mold 1 (mold radial direction) coincides with the tire radial direction.

The tire mold 1 has a plurality of mold segments 2 arranged annularly along the mold circumferential direction S, and a tire is molded by the plurality of mold segments 2. The plurality of mold segments 2 are split molds, and are split along the mold circumferential direction S of the tire mold 1. The mold die 2 is a tread mold for molding a tread portion of a tire. In forming a tire, a plurality of mold segments 2 are moved in the radial direction of the mold in the tire forming apparatus, and are combined into a ring shape to surround the tire.

Fig. 2 is a perspective view showing the die 2 of embodiment 1, and shows the structure of the die 2 in perspective. Fig. 3 is a perspective view showing the die 2 of embodiment 1 after being disassembled.

As shown in the figure, the die 2 includes: a plurality of mold pieces 10, the plurality of mold pieces 10 being located at an inner peripheral portion of the tire mold 1; and a holder 3 located at the outer peripheral portion of the tire mold 1. The plurality of mold pieces 10 are molding members for molding the tire, are attached to the attachment portion 3A of the holder 3, and are arranged in order along the mold circumferential direction S.

The holder 3 holds the plurality of mold pieces 10 to the mounting portion 3A located on the inner peripheral side of the tire mold 1. The plurality of mold pieces 10 extend in the mold width direction W and are arranged adjacent to each other in the mold circumferential direction S. The plurality of die pieces 10 are formed with slit vents 4 as gaps for air discharge between the adjacent die pieces 10. The slit exhaust port 4 is a slit-shaped air discharge portion (exhaust portion) that discharges air between the tire and the mold sheet 10.

Fig. 4 is a perspective view showing the die sheet 10 of embodiment 1, and shows a part of the die sheet 10 among the plurality of die sheets 10 provided in the die segment 2. Fig. 5 is a perspective view showing a plurality of mold segments 10 provided in mold die 2 according to embodiment 1. Fig. 4 (a in fig. 4 and B in fig. 4) and fig. 5 (a in fig. 5 and B in fig. 5) each show a perspective view of the tire mold 1 as seen from the inner peripheral side and the outer peripheral side.

As shown, the die 10 has: a molding portion 11 located on the tire side (inner peripheral side of the tire mold 1); a back surface portion 12 located on the holder 3 side (outer peripheral side of the tire mold 1); and two opposing portions 13, the two opposing portions 13 being located between the forming portion 11 and the back surface portion 12. The die 10 forms a tire by the forming portion 11, and forms a concave portion (e.g., groove, sipe) in the tire by the protrusion 14 provided on the forming portion 11. The back surface portion 12 is located on the opposite side (back surface side) of the die sheet 10 from the forming portion 11, and contacts the mounting portion 3A (see fig. 3) of the holder 3. The opposing portions 13 are side portions located on both sides of the die circumferential direction S of the die sheet 10. The plurality of mold pieces 10 are arranged so that the opposing portions 13 face each other.

The die sheet 10 has a convex slit forming portion 15 and a concave accommodating portion 16 in the opposing portion 13. The slit forming portion 15 is a portion of the die sheet 10 where the slit vent 4 is to be formed, and is formed along the forming portion 11 at the opposing portion 13 of the die sheet 10. The plurality of mold pieces 10 are arranged so that the slit forming portions 15 face each other, and the tire is formed by the forming portion 11 in a state where the slit exhaust ports 4 (see fig. 2) are formed between the slit forming portions 15. The slit forming portions 15 of the adjacent die pieces 10 face each other in a state where a gap (slit vent 4) is formed, and the slit vent 4 is formed between the slit forming portions 15 of the adjacent die pieces 10.

The receiving portion 16 is a recess formed in the opposing portion 13 of the die plate 10, and receives a part of the holding member 20. The maintaining member 20 is sandwiched between the opposing portions 13 of the adjacent die pieces 10, and maintains the width of the slit vent 4 (the interval between the adjacent slit forming portions 15). Here, the holding member 20 is a cylindrical member (e.g., a pin), and the inner surface of the housing portion 16 is formed as a concave circular arc surface corresponding to the outer peripheral shape of the holding member 20. The plurality of accommodating portions 16 are formed at the opposing portion 13 of the die plate 10 at intervals, and the plurality of columnar holding members 20 are disposed in the accommodating portions 16, respectively.

The accommodating portion 16 is formed at a position closer to the back surface portion 12 than the slit forming portion 15 of the opposing portion 13 of the die sheet 10, and is opened at the back surface portion 12. The holding member 20 is accommodated in the accommodating portion 16 of the adjacent die sheet 10 and is sandwiched between the adjacent die sheet 10 at a position closer to the back surface portion 12 than the slit forming portion 15. The adjacent die pieces 10 are positioned by the holding member 20, so that the interval between the adjacent slit forming portions 15 is maintained. Thereby, the width of the slit vent 4 is maintained at a predetermined width.

The tire mold 1 includes a plurality of mold segments 10 in each of the plurality of mold segments 2. The plurality of mold pieces 10 are divided pieces, and are divided along the mold circumferential direction S of the tire mold 1. The opposing portion 13 is a divided portion of the die sheet 10. In the tire mold 1, a plurality of mold pieces 10 are arranged in a ring shape along the mold circumferential direction S. The method of manufacturing the tire mold 1 will be described below.

Fig. 6 to 13 are perspective views showing a process of manufacturing the tire mold 1 according to embodiment 1. Fig. 6 (a in fig. 6 and B in fig. 6) is a perspective view of the tire mold 1 as seen from the inner and outer circumferential sides.

As shown in the drawing, a mold material 30 including a plurality of mold pieces 10 is produced, and the mold material 30 is divided into a plurality of mold pieces 10. The tire mold 1 is manufactured by forming a plurality of mold pieces 10 from a mold blank 30. The die blank 30 is a sheet material that becomes a blank of the plurality of die pieces 10, and includes portions to be the plurality of die pieces 10 and a machining allowance of the die pieces 10. Here, the mold material 30 is a metal casting. The mold material 30 is cast to form the molded portion 11 including the protrusion 14 of the plurality of mold pieces 10 (see fig. 6). In addition, all the die pieces 10 included in the 1 die 2 are formed from the 1 die blank 30. Thus, the die blank 30 is a die material.

In forming the plurality of mold pieces 10, first, the back surface 31 of the mold material 30 is processed. The back surface 31 of the die blank 30 is a portion corresponding to the back surface 12 of the plurality of die pieces 10, and is located on the opposite side (back surface side) of the die blank 30 from the forming portion 11 (see fig. 7). The back surface 31 of the die blank 30 is machined so that the back surface 31 of the die blank 30 is formed into a shape corresponding to the back surface 12 of the die sheet 10. At this time, the back surface 31 of the die blank 30 is formed in a shape (a shape obtained by dividing the cylindrical surface in the circumferential direction) that becomes a part of the cylindrical surface. Thereby, the back surface 31 of the die blank 30 is formed into a curved surface having a predetermined curvature.

The die blank 30 is formed in a shape in which a plurality of die pieces 10 are continuous. Next, a plurality of blind holes 32 are formed in the back surface 31 side of the die blank 30 (see fig. 8). The blind hole 32 is a non-through hole of a circular shape for accommodating the holding member 20, and is not opened at the forming portion 11, but is opened only at the back surface portion 31. A plurality of blind holes 32 are formed at intervals along the respective dividing positions of the plurality of die pieces 10 in the die blank 30. The blind holes 32 are formed as portions (dividing positions) where the centers of the blind holes 32 in the radial direction are located between the adjacent die pieces 10.

Next, a plurality of dividing grooves 33 are formed on the back surface 31 side of the die blank 30 (see fig. 9). The dividing grooves 33 are concave grooves (grooves) formed at dividing positions of the plurality of die pieces 10, open at the back surface portion 31, and are formed along the entire die width direction W of the die blank 30. The dividing groove 33 does not penetrate the molding portion 11 of the die blank 30, and the bottom of the dividing groove 33 is located between the back surface 31 of the die blank 30 and the molding portion 11. The width of the dividing groove 33 is larger than the width of the slit vent 4 and smaller than the diameter of the blind hole 32. The depth of the dividing groove 33 is greater than the depth of the blind hole 32.

A dividing groove 33 wider than the slit vent 4 is formed along the dividing position of the plurality of die pieces 10 in the die blank 30. The plurality of dividing grooves 33 extend from one end of the die blank 30 in the die width direction W to the other end of the die blank 30 in the die width direction W, and are formed in parallel with each other. In addition, at each of the dividing positions of the plurality of die pieces 10, a dividing groove 33 is formed along the dividing position so as to pass through the plurality of blind holes 32. The dividing groove 33 passes through the center of the blind hole 32 in the radial direction so that the center of the dividing groove 33 in the width direction coincides with the center of the blind hole 32 in the radial direction.

A plurality of dividing grooves 33 are formed in the mold material 30 on the forming portion 11 side with the residual portion 34 left. The remaining portion 34 of the die blank 30 is an unprocessed portion remaining between the dividing groove 33 and the forming portion 11, and is located between the bottom of the dividing groove 33 and the forming portion 11. The thickness of the residual portion 34 is smaller than the depth of the dividing groove 33. At the entire dividing position of the plurality of die pieces 10, the entire portion of the die blank 30 on the forming portion 11 side remains as the residual portion 34 in the die blank 30.

Next, the die material 30 is cut at the bottoms of the plurality of dividing grooves 33 by a laser beam machine (laser cutter) (see fig. 10), and the die material 30 is divided in the die circumferential direction S at the laser cutting portion 35. The width of the dividing groove 33 is larger than the cutting width (the width of the laser cutting portion 35) of the die blank 30 by laser cutting. The die material 30 is cut at the center of the dividing groove 33 in the width direction, and the die material 30 is cut along the dividing groove 33 at the bottom of the dividing groove 33. The die blank 30 is cut and divided at the dividing positions of the plurality of die pieces 10 by laser cutting. The plurality of die pieces 10 are divided by laser cutting, and slit forming portions 15 are formed on the forming portion 11 side of the plurality of die pieces 10.

The portion (the residual portion 34) between the forming portion 11 of the die blank 30 and the bottom portion of the dividing groove 33 is cut by laser cutting (see fig. 11). The dividing groove 33 includes a 1 st groove portion 33A and a 2 nd groove portion 33B. The 1 st groove portion 33A is a portion of the dividing groove 33 closer to the back surface portion 31 of the die blank 30. The 2 nd groove portion 33B is a portion on the bottom side of the dividing groove 33 (the forming portion 11 side of the die blank 30), and is narrower than the 1 st groove portion 33A. The 1 st groove portion 33A and the 2 nd groove portion 33B are formed by, for example, cutting processing using an end mill, or by electric discharge machining. When the 2 nd groove portion 33B cannot be formed by the cutting process, the 1 st groove portion 33A is formed by the cutting process, and the 2 nd groove portion 33B is formed by the electric discharge process.

By cutting the die blank 30 with laser light, the concave space forming portions 17 are formed in the dividing grooves 33 of the divided die pieces 10. The space forming portion 17 is formed at the opposing portion 13 of the die sheet 10. The plurality of mold pieces 10 form a discharge space 18 for discharging air between the adjacent space forming portions 17. The slit forming portion 15 is a portion of the die blank 30 cut by the laser (laser cutting portion 35 of the residual portion 34), and is formed between the forming portion 11 and the bottom of the dividing groove 33. In addition, the slit forming portion 15 is formed along the surface of the forming portion 11 including the protrusion 14.

When the mold material 30 is cast, the base end portion of the sipe blade is joined to the molding portion 11 side of the mold material 30 by insert casting (japanese: cast-in-place) in the mold, the entire base end portion of the sipe blade is located in the portion of the residual portion 34 (slit forming portion 15) and the 2 nd groove portion 33B at the opposing portion 13 of the mold sheet 10. That is, the widths of the residual portion 34 and the 2 nd groove portion 33B are larger than the length of the base end portion of the sipe blade at the opposing portion 13 of the mold sheet 10. For example, when the length of the base end portion of the sipe blade is 5mm, the widths of the remaining portion 34 and the 2 nd groove portion 33B are 6mm to 7mm. By such arrangement, the engagement strength of the sipe blade can be ensured.

The thickness of the residual portion 34 is a thickness that can be cut by a laser processing machine at one time, and is set in accordance with the width of the slit exhaust port 4. For example, when the width of the slit vent 4 is 0.04mm to 0.06mm, the thickness of the residual portion 34 is about several mm. The blind hole 32 is formed shallower than the dividing groove 33 and has a diameter larger than the width of the dividing groove 33. The die blank 30 is cut by a laser at the bottom of the plurality of dividing grooves 33, thereby dividing the blind hole 32. Thereby, the accommodating portion 16 is formed at the blind hole 32 portion of the plurality of divided mold pieces 10. Thus, the receiving portion 16 is part of the blind bore 32.

A part of the holding member 20 is accommodated in the accommodating portion 16 of the mold sheet 10 by each accommodating portion 16 (see fig. 12) of the plurality of accommodating portions 16, and the holding member 20 is fixed to the mold sheet 10 by fixing means (e.g., brazing, joining, adhesion, welding, bolts, pins). The holding member 20 is accommodated in the accommodating portion 16 of the adjacent mold piece 10, and the holding member 20 is sandwiched between the adjacent mold pieces 10 (see fig. 13). Thereby, the plurality of mold pieces 10 are combined in a state where the slit vent 4 is formed between the slit forming portions 15 of each other. Next, the plurality of mold pieces 10 are held by the holder 3 to form the mold die 2 (see fig. 2 and 3). All the mold segments 2 of the tire mold 1 are formed by the same process, and the tire mold 1 is manufactured (see fig. 1).

The width of the slit vent 4 is maintained to be the same as the cutting width by laser cutting by the maintaining member 20. When the width of the slit vent 4 is to be different from the cutting width by laser cutting, another holding member 20 having a different size is used. Thereby, the dimension of the maintaining member 20 in the width direction of the slit exhaust port 4 is increased or decreased, and the width of the slit exhaust port 4 is changed. The width of the slit exhaust port 4 is a width corresponding to the size of the maintaining member 20, and is maintained by the maintaining member 20. The width of the slit vent 4 is adjusted by changing the width of the slit vent 4. In this state, a plurality of mold pieces 10 are combined. When the width of the slit vent 4 is 0.005mm to 0.05mm, the entry of rubber into the slit vent 4 can be more reliably suppressed during the formation of the tire.

The width of the slit exhaust port 4 can also be adjusted by an adjusting member (not shown). The width of the slit vent 4 is adjusted by sandwiching an adjustment member between the adjacent die pieces 10 together with the holding member 20. The adjustment member is, for example, a plate-like member formed to have a predetermined thickness, and is sandwiched between the holding member 20 and the die plate 10. In this state, the holding member 20 is fixed to the die plate 10. The width of the slit exhaust port 4 can be changed in accordance with the thickness of the adjustment member. For example, it is assumed that the width of the slit vent 4 is maintained at a cutting width (0.04 mm) by laser cutting by the maintaining member 20 (size: 10 mm). When the width of the slit vent 4 is to be changed to 0.06mm, an adjusting member (thickness: 0.02 mm) is sandwiched between the holding member 20 and the die plate 10.

As described above, when forming the die 10, the plurality of dividing grooves 33 are formed on the back surface 31 side of the die blank 30, and the portion to be cut by laser cutting (the residual portion 34) can be made thinner. In addition, the die blank 30 can be easily cut by laser light, and the slit forming portion 15 can be easily formed in the die sheet 10. The laser cutting can accurately divide the plurality of die pieces 10, and the cutting width of the die blank 30 can be made narrower. The machining allowance of the die sheet 10 in the die blank 30 can be reduced. Thus, a plurality of mold pieces 10 can be easily formed, and the manufacturing efficiency of the tire mold 1 can be improved. The accuracy of the dimensions of the die plate 10 can also be improved.

In the tire mold 1, the width of the slit vent 4 can be easily maintained by the maintaining member 20, and the slit vent 4 can be accurately formed. By accommodating the holding member 20 in the accommodating portion 16, the holding member 20 can be easily and accurately sandwiched between the adjacent mold pieces 10. The accommodating portion 16 can be easily formed in the die 10 by laser cutting.

The width of the slit exhaust port 4 can be easily changed by increasing or decreasing the size of the maintaining member 20. The width of the slit exhaust port 4 can be easily adjusted by the adjusting member. Depending on the shape of the opposing portion 13 of the die 10, the width of the slit vent 4 may vary or be adjusted, thereby varying the width of the slit vent 4. In this case, the width of the slit vent 4 is changed or adjusted according to the average value of the widths in the slit vent 4.

The width of the slit vent 4 may also be adjusted by utilizing the difference in the amount of thermal expansion between the die plate 10 and the retaining member 20. In this case, the maintaining member 20 having a thermal expansion coefficient different from that of the mold pieces 10 is sandwiched between the adjacent mold pieces 10. Upon vulcanization of the tire, with heating, the mold sheet 10 and the holding member 20 expand by a thermal expansion amount corresponding to the respective thermal expansion rates (for example, linear expansion rates). The width of the slit vent 4 at the time of tire vulcanization changes from the width before heating in accordance with the difference in the amount of thermal expansion between the die plate 10 and the holding member 20. Thereby, the width of the slit exhaust port 4 at the time of tire vulcanization is adjusted.

For example, the die sheet 10 is made of an aluminum alloy (wire-expandedExpansion ratio: 23X 10 ^－6 (1/K)), the maintenance member 20 (diameter: 10 mm) is made of steel (linear expansion coefficient: 11×10 ^－6 (1/K)). In addition, the mold blank 30 is processed at room temperature (25 ℃) and, at the time of tire vulcanization, the mold sheet 10 and the holding member 20 are heated to the vulcanization temperature (160 ℃). In this case, the calculation formula ((23-11) ×10) based on the difference in the thermal expansion amounts ^－6 X (160-25) ×10), the difference in thermal expansion amount between the die sheet 10 and the holding member 20 was 0.016mm. As a result, the width of the slit vent 4 was narrowed by 0.016mm at the time of tire vulcanization.

The holding member 20 may be formed in a shape other than a cylindrical shape (for example, a square column shape, a block shape, or a plate shape). The die blank may be a ring-shaped blank (for example, a ring-shaped casting). The annular mold material is divided in the mold circumferential direction S to form all the mold pieces 10 of the tire mold 1.

(embodiment 2)

Next, a method for manufacturing the tire mold 1 according to embodiment 2 will be described. The method for manufacturing the tire mold 1 according to embodiment 2 will not be described in detail with respect to the same matters as those of the method for manufacturing the tire mold 1 according to embodiment 1. Note that, in the structure of embodiment 2, the same names as those of the structure of embodiment 1 are used for the structure corresponding to the structure of embodiment 1.

Fig. 14 is a perspective view showing die 2 according to embodiment 2, and shows the structure of die 2 in perspective. Fig. 15 is a perspective view showing die 2 according to embodiment 2 after being disassembled. Fig. 16 is a perspective view showing the die sheet 10 of embodiment 2, and shows a part of the die sheet 10 among the plurality of die sheets 10 provided in the die segment 2. Fig. 17 is a perspective view showing a plurality of mold segments 10 provided in mold die 2 according to embodiment 2. Fig. 16 (a in fig. 16 and B in fig. 16) and 17 (a in fig. 17 and B in fig. 17) each show a perspective view of the tire mold 1 as seen from the inner peripheral side and the outer peripheral side.

As shown in the drawing, the die sheet 10 has a slit forming portion 15 and a concave receiving portion 19 (see fig. 16) in the opposing portion 13. The receiving portion 19 is formed in the opposing portion 13 of the die sheet 10 in the entire die width direction W, and receives a part of the holding member 40. Here, the holding member 40 is a plate-like member, and the surface of the housing portion 19 is formed as a flat surface corresponding to the surface shape of the holding member 40. Further, 1 accommodation portion 19 is formed on the back surface portion 12 side of the opposing portion 13, and 1 plate-like holding member 40 is disposed in the accommodation portion 19.

Fig. 18 to 22 are perspective views showing a process of manufacturing the tire mold 1 according to embodiment 2. Fig. 21 (a in fig. 21 and B in fig. 21) is a perspective view of the tire mold 1 as seen from the inner peripheral side and the outer peripheral side.

As shown in the drawing, when forming a plurality of mold pieces 10, first, the back surface 31 of the mold material 30 is processed (see fig. 18). Next, a plurality of dividing grooves 33 are formed on the back surface 31 side of the die blank 30. A plurality of dividing grooves 33 are formed along dividing positions of the plurality of die pieces 10 in the die blank 30. Next, the die material 30 is cut by a laser at the bottom of the plurality of dividing grooves 33 (see fig. 19). The plurality of die pieces 10 are divided by laser cutting, and slit forming portions 15 are formed on the forming portion 11 side of the plurality of die pieces 10 (see a of fig. 20).

The die blank 30 is cut by a laser at the bottom of the plurality of dividing grooves 33, thereby dividing the dividing grooves 33 partially. Thereby, the accommodating portion 19 is formed at the dividing groove 33 portion of the divided plurality of die pieces 10. Thus, the accommodating portion 19 is a part of the dividing groove 33. The holding member 40 has a plurality of discharge grooves 41 for discharging air (see B in fig. 20 and 21). A part of the holding member 40 is accommodated in the accommodating portion 19 of the mold sheet 10, and the holding member 40 is fixed to the mold sheet 10. The holding member 40 is accommodated in the accommodating portion 19 of the adjacent mold piece 10, and the holding member 40 is sandwiched between the adjacent mold pieces 10 (see fig. 22). Thereby, the plurality of mold pieces 10 are combined in a state where the slit vent 4 is formed between the slit forming portions 15 of each other. Next, the plurality of mold pieces 10 are held by the holder 3 to form the mold die 2 (see fig. 14 and 15).

As described above, the accommodating portion 19 can be easily formed in the die 10 by laser cutting. In addition, the use of the dividing groove 33 as the accommodating portion 19 can improve the forming efficiency of the die plate 10.

Description of the reference numerals

1. A tire mold; 2. mold die; 3. a holder; 4. a slit exhaust port; 10. a die sheet; 11. a forming part; 12. a back surface portion; 13. an opposing portion; 14. a protrusion; 15. a slit forming portion; 16. a housing part; 17. a space forming part; 18. a discharge space; 19. a housing part; 20. a maintenance member; 30. a die blank; 31. a back surface portion; 32. a blind hole; 33. a dividing groove; 34. a residual part; 35. a laser cutting section; 40. a maintenance member; 41. and a discharge groove.

Claims

1. A method for manufacturing a mold for a tire, in which a plurality of mold pieces are formed by a mold blank, the plurality of mold pieces forming a tire by a forming portion in a state in which slit exhaust ports are formed between slit forming portions of each other,

the method for manufacturing the tire mold comprises the following steps:

forming a plurality of dividing grooves wider than the slit exhaust ports along dividing positions of the plurality of die pieces on the back surface side of the die blank; and

cutting the die blank by laser at the bottoms of the plurality of dividing grooves to divide the plurality of die pieces and integrally forming convex slit forming portions at the laser cutting portions of the opposed portions of the plurality of die pieces on the forming portion side,

the thickness of the part of the dividing groove which remains between the dividing groove and the forming part is a thickness which can be cut by a laser processing machine by one cutting,

a plurality of mold pieces are combined in such a manner that a maintaining member maintaining the width of the slit vent is sandwiched between the adjacent mold pieces,

a plurality of blind holes are formed on the back side of the die blank at intervals along the dividing positions of the plurality of die pieces,

forming a dividing groove along the dividing position in a manner of penetrating through the plurality of blind holes at each dividing position of the plurality of die pieces,

cutting the die blank at the bottoms of the plurality of dividing grooves by laser, thereby forming accommodating portions at blind hole portions of the divided plurality of die pieces,

the holding member is accommodated in the accommodating portion so as to be sandwiched between the adjacent mold pieces.

2. The method for manufacturing a mold for tires according to claim 1, wherein,

the width of the slit vent is adjusted by the adjusting member by sandwiching the adjusting member together with the holding member between the adjacent mold pieces.

3. The method for manufacturing a mold for tires according to claim 1 or 2, wherein,

the dimension of the maintaining member in the width direction of the slit exhaust port is increased or decreased, thereby changing the width of the slit exhaust port.

4. The method for manufacturing a mold for tires according to claim 1 or 2, wherein,

a maintaining member having a thermal expansion coefficient different from that of the mold pieces is sandwiched between the adjacent mold pieces.

5. The method for manufacturing a mold for tires according to claim 3, wherein,