Method for manufacturing a mold, method for manufacturing a tire, and tire mold

Abstract

The present invention provides a method for manufacturing a mold, a method for manufacturing a tire, and a tire mold, which can achieve good machining accuracy and high strength. The method for manufacturing the mold of the present invention includes the following steps: (A) a step of separating the insert from a mold integrated with the insert and a metal bar, and exposing a groove corresponding to the insert on the surface of the mold; and (B) a step of flowing a molding material into the mold and curing it to obtain a formed mold having a rib corresponding to the groove. In the integrated mold in the step (A), the insert extends inward from an end surface of the mold, the metal bar extends continuously with the insert from an inner end of the insert, and a protrusion is embedded in a hole provided on a surface of the insert in contact with the metal bar, and the protrusion is provided on a surface of the metal bar in contact with the insert.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a mold, a method for manufacturing a tire, and a tire mold. Background Art

[0002] A mold for a tire includes a plurality of forming dies. For example, the mold has a combination mold, side plates, bead rings, etc. On the cavity surface of the combination mold, ribs for forming grooves on the tread of the tire are usually provided.

[0003] The forming die is usually made by a casting method. For example, a plaster mold for forming a combination mold is prepared. Grooves for forming the ribs of the combination mold are engraved on the surface of the mold. A molding material made of a metal such as aluminum alloy is poured into the mold and cured. The mold is removed to obtain a base mold for the combination mold. In order to precisely machine the end face to a desired size with high precision, the end face of the base mold is machined by cutting. Thus, a combination mold with high dimensional accuracy is obtained. Research on a method for manufacturing a mold based on the casting method is reported in Japanese Patent Application Laid-Open No. 2007-331132.

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-331132 Summary of the Invention

[0005] There is a tire having a groove (undercut-shaped groove) on the tread, and a portion where the width inside the groove is wider than the width on the surface. In order to form this groove, the combination mold for this tire needs to have a rib (undercut-shaped rib) whose width at the end side is wider than that at the root. The base mold for the combination mold also has an undercut-shaped rib. However, it is not easy to form a rib of this shape by a casting method. As a countermeasure, the following method is considered: an undercut-shaped rib is made of another metal part (metal bar), and it is integrated with the main body formed by the casting method to make a base mold. In the base mold formed by this method, the main body is formed by curing a molding material, and the undercut-shaped rib is realized by the above-mentioned metal bar.

[0006] In order for the rib to have sufficient strength, a hard metal bar needs to be used. The undercut-shaped rib sometimes reaches the end face of the base mold. In this case, the hard metal bar will interfere with the machining of the end face. The machining of the end face becomes difficult. This hinders the achievement of good machining accuracy of the forming die.

[0007] An object of the present invention is to provide a method for manufacturing a mold that can achieve good machining accuracy and high strength even in a forming die having an undercut-shaped rib.

[0008] The method for manufacturing a mold of the present invention includes the following steps:

[0009] (A) process of separating the insert from the mold integrated with the insert and the metal strip, exposing a groove corresponding to the insert on the surface of the mold; and

[0010] (B) process of flowing a molding material into the above-mentioned mold and curing it to obtain a molded die having a protrusion corresponding to the above-mentioned groove,

[0011] In the integrated mold in the above-mentioned (A) process, the insert extends inward from the end face of the mold, the metal strip extends continuously with the insert from the inner end of the insert, and a protrusion is embedded in a hole provided on the surface of the insert in contact with the metal strip, and the protrusion is provided on the surface of the metal strip in contact with the insert.

[0012] Preferably, the length of the above-mentioned protrusion is 0.5 times or more of the length of the insert.

[0013] Preferably, the above-mentioned (B) process includes the following processes:

[0014] (B1) process of flowing a molding material into the above-mentioned mold and curing it to obtain a base die having a protrusion corresponding to the above-mentioned groove and the above-mentioned metal strip; and

[0015] (B2) process of machining the end face of the above-mentioned base die to obtain a molded die.

[0016] Before the above-mentioned (A) process, it includes the following processes:

[0017] (C1) process of obtaining a master model having a convex portion on its transfer surface;

[0018] (C2) process of forming a rubber mold having a cavity surface with a shape reverse to the shape of the above-mentioned transfer surface and an end face extending from the end of the cavity surface, and having a concave portion corresponding to the above-mentioned convex portion and extending from the above-mentioned end face on the cavity surface;

[0019] (C3) process of installing, on the above-mentioned rubber mold, an insert extending inward from the above-mentioned end face and protruding from the above-mentioned cavity surface and a metal strip extending continuously with the insert and protruding from the above-mentioned cavity surface by using the above-mentioned concave portion; and

[0020] (C4) process of flowing a mold material into the above-mentioned rubber mold and curing it to obtain a mold integrated with the above-mentioned insert and the above-mentioned metal strip.

[0021] Preferably, the above-mentioned groove has an undercut shape.

[0022] Preferably, the above-mentioned insert has a core portion and a cover covering the core portion,

[0023] The above-mentioned (A) process includes the following processes:

[0024] (A1) step of pulling out the core from the above-mentioned mold; and

[0025] (A2) step of removing the cover from the above-mentioned mold.

[0026] Preferably, the core and the cover are formed of resin.

[0027] Preferably, the cover is softer than the core.

[0028] Preferably, the hardness of the core is 80 or more.

[0029] Preferably, the hardness of the cover is 20 or more and 40 or less.

[0030] Preferably, the thickness of the cover is 0.2 mm or more and 1.0 mm or less.

[0031] Preferably, the portion of the metal bar embedded in the mold has an undercut shape.

[0032] Preferably, the metal bar is harder than the protrusion formed by curing the above-mentioned molding material.

[0033] Preferably, the material of the metal bar is steel and the material of the protrusion is aluminum alloy.

[0034] Preferably, the length of the insert is 8 mm or more and 20 mm or less.

[0035] The method for manufacturing a tire of the present invention includes the following steps:

[0036] Manufacturing a mold by the above method; and

[0037] Pressurizing and heating a green tire in the above-mentioned mold.

[0038] The mold for a tire of the present invention has a molding die, and the molding die has a cavity surface and an end surface extending from an end of the cavity surface. The molding die has a main body and protrusions protruding from the main body in the cavity surface. The protrusions have side portions extending inward from the end surface and central portions continuously extending from the side portions. The side portions have holes in the surfaces in contact with the central portions, and the central portions have protrusions in the surfaces in contact with the side portions, and the protrusions are embedded in the holes. The side portions and the main body are integrally formed of the same material. The central portions are formed of a metal harder than the side portions.

[0039] The manufacturing method of the mold of the present invention includes the following steps: separating the insert from the mold integrated with the insert extending from the end face and the metal strip continuously extending from the insert, so that the surface of the mold exposes the groove corresponding to the insert. In the base mold formed by the casting method using this mold, the rib has a part formed by the above groove (side part) and a part formed by the metal strip (central part). The side part is made of the same material as the main body and extends inward from the end face. The central part extends continuously with the side part and is separated from the end face. The end face is formed by the main body and the side part made of the same material. The machining of the end face is easy. By machining this base mold, a molding die with high dimensional accuracy can be obtained.

[0040] In this manufacturing method, since the central part formed by the metal strip is separated from the end face, even if the metal strip is hard, the metal strip does not interfere with the machining of the end face. A hard metal strip can be used without affecting the dimensional accuracy. By using a hard metal strip, a higher strength can be achieved in the central part of the rib.

[0041] In this manufacturing method, the metal strip has protrusions on the surface in contact with the insert, and the protrusions are embedded in the holes of the insert. By flowing the molding material into the groove after the insert is separated and curing it, the side part is formed. In this base mold, the protrusions of the metal strip are structured to be embedded in the holes of the side part. This effectively contributes to the improvement of the strength of the side part. A higher strength can be achieved in the side part of the rib. In this manufacturing method, the defect of the side part during the machining of the end face of the base mold can be prevented.

[0042] In this manufacturing method, by making the insert and the metal strip have an undercut shape, an undercut-shaped rib can be realized in the molding die. In this manufacturing method, even if the molding die has an undercut-shaped rib, a molding die with good machining accuracy and high strength can be manufactured. Description of the Drawings

[0043] Figure 1 is a perspective view showing the tread of a tire manufactured using the mold manufactured by the manufacturing method of the present invention.

[0044] Figure 2 is showing Figure 1 a cross-sectional view of the groove of the tire.

[0045] Figure 3 is a top view showing an example of the mold manufactured by the manufacturing method of the present invention.

[0046] Figure 4 is along Figure 3 the cross-sectional view of the combined mold of the IV-IV line.

[0047] Figure 5 is showing for manufacturing Figure 3Stereogram of the master model of the combined mold.

[0048] Figure 6 It is a stereogram showing the rubber mold, inserts, and metal strips of the combined mold used for manufacturing Figure 3 together.

[0049] Figure 7 (a) of Figure 6 is a stereogram of the insert of Figure 7 (b) of Figure 7 is a cross-sectional view along line VII(b)-VII(b) of (a) of Figure 7 (c) of Figure 7 is a rear view of the insert of (a) of Figure 7 (d) of Figure 7 is a stereogram showing the state where the core part of the insert of (a) of

[0050] Figure 8 is Figure 6 a stereogram of the metal strip of

[0051] Figure 9 It is a stereogram showing the casting mold formed by the rubber mold of Figure 6 together with the inserts and metal strips.

[0052] Figure 10 It is a stereogram showing the situation where the core part of the insert of Figure 9 is pulled out.

[0053] Figure 11 It is a stereogram showing the situation where the cover of the insert of Figure 9 is removed.

[0054] Figure 12 It is a stereogram showing the base mold formed by the casting mold of Figure 9 together.

[0055] Reference numeral description

[0056] 2: Tire; 4: Tread; 6: Groove; 8: Siping; 10: Mold; 12: Forming Mold; 14: Composite Mold; 16: Side Plate; 18: Bead Ring; 20: Mold Cavity Surface; 21: Main Body of Composite Mold; 22: Rib; 24: Blade; 26: Master Model; 28: Transfer Surface; 30: Substrate Main Body; 32: Plate; 34: Main Groove; 36: Main Siping; 38: Protrusion; 40: Rubber Mold; 41: Main Body of Rubber Mold; 42: Recess; 44: Metal Strip; 46: Insert; 48: Mold Cavity Surface of Rubber Mold; 50: End Face of Rubber Mold; 52: Inner End of Insert; 54: Groove Forming Portion of Insert; 56: Platform Portion of Insert; 58: Core; 60: Cover; 61: Hole of Insert; 62: End; 64: Groove Forming Portion of Metal Strip; 66: Platform Portion of Metal Strip; 67: Protrusion of Metal Strip; 68: Casting Mold; 72: Casting Mold Intermediate; 74: End Face of Casting Mold; 76: Groove; 78: Base Mold; 80: Main Body of Base Mold; 82: Rib; 82a: Side Portion; 82b: Central Portion; 84: End Face of Base Mold. Detailed Description of the Invention

[0057] Hereinafter, the present invention will be described in detail according to preferred embodiments with appropriate reference to the accompanying drawings.

[0058] Figure 1 is a perspective view showing a part of the tread 4 of the tire 2. In Figure 1 , the radial direction of the tire 2 is indicated by the arrow X, the axial direction of the tire 2 is indicated by the arrow Y, and the circumferential direction of the tire 2 is indicated by the arrow A. As shown in the figure, grooves 6 extending in the circumferential direction are engraved on the tread 4 of the tire 2. In this figure, three grooves 6, namely the first groove 6a, the second groove 6b, and the third groove 6c, are shown in order from the front. And, a plurality of sipings 8 are engraved on the tread 4. Each sipping 8 extends substantially in the axial direction. The sipping 8 is serrated.

[0059] Figure 2 is a cross-sectional view showing Figure 1 the second groove 6b. In this figure, a cross-section perpendicular to the circumferential direction is shown. As shown in the figure, in the second groove 6b, there is a portion where the width inside is wider than the width on the surface. The groove 6 having this shape is called a "undercut-shaped groove". Or, this groove 6 is called "having an undercut shape". In the tire 2 of this embodiment, the second groove 6b has an undercut shape. The first groove 6a and the third groove 6c do not have an undercut shape.

[0060] Figure 3 is a top view showing the mold 10 for manufacturing the tire 2 shown in Figure 1 and Figure 2 . In Figure 3 , the radial direction is indicated by the arrow X, the circumferential direction is indicated by the arrow A, and the direction perpendicular to the paper surface is the axial direction. As Figure 3As shown, the mold 10 includes a plurality of forming dies 12. In Figure 3 the embodiment, the mold 10 has an arc-shaped combined die 14, an annular side plate 16, and an annular bead ring 18. Figure 3 The solid line in Figure 3 represents the closed state of the mold 10. Although not shown, in this state, a green tire is received in the space (mold cavity) surrounded by the combined die 14, the side plate 16, and the bead ring 18. In

[0061] Figure 4 shows the cross-section of the combined die 14 along the IV-IV line in Figure 3 . In Figure 4 , the radial direction is indicated by arrow X, the axial direction is indicated by arrow Y, and the direction perpendicular to the paper surface is the circumferential direction.

[0062] The combined die 14 has a cavity surface 20 that contacts the tread of the green tire. The combined die 14 has a main body 21, a plurality of ridges 22 for forming grooves 6 on the tread 4, and a plurality of blades 24 for forming sipes 8.

[0063] As Figure 4 shown, in this embodiment, there are five ridges 22, namely, a first ridge 22a, a second ridge 22b, a third ridge 22c, a fourth ridge 22d, and a fifth ridge 22e, in sequence from below the paper surface to above. Each ridge 22 is located on the cavity surface 20. The ridges 22 extend in the circumferential direction. In this embodiment, the ridges 22 extend from one end surface in the circumferential direction of the cavity surface 20 of the combined die 14 to the other end surface. The ridges 22 extend from one end surface in the circumferential direction of the combined die 14 to the other end surface. The ridges 22 are formed integrally with the main body 21.

[0064] The ridge 22 for forming a groove with an undercut shape has a shape where the width of the end side is wider than that of the root. The ridge 22 having this shape is called an "undercut-shaped ridge". Or, this ridge 22 is called "having an undercut shape". In this embodiment, the second ridge 22b and the fourth ridge 22d are undercut-shaped ridges.

[0065] Each blade 24 is located on the cavity surface 20. Although not shown in Figure 4 , as described later, the blade 24 is serrated corresponding to the shape of the sipe 8. The blade 24 is usually made of metal. A typical material of the blade 24 is steel.

[0066] In the manufacturing method of the mold 10 of the present invention, the combined die 14 is formed by a casting method. The process of forming the combined die 14 includes:

[0067] (1) The process of preparing a master model;

[0068] (2) Process of forming a rubber mold;

[0069] (3) Process of installing metal strips and inserts on the rubber mold;

[0070] (4) Process of obtaining a casting mold integrated with the metal strips and inserts;

[0071] (5) Process of separating the insert from the casting mold; and

[0072] (6) Process of obtaining a combined mold.

[0073] In the process of (1) above, a master model 26 for the combined mold 14 is prepared. Figure 5 It is shown in Figure 5 . In

[0074] , the radial direction is indicated by arrow X, the axial direction is indicated by arrow Y, and the circumferential direction is indicated by arrow A. The outer surface 28 (transfer surface 28) of the master model 26 corresponds to the cavity surface 20 of the combined mold 14. This transfer surface 28 has the same size as the cavity surface 20 of the combined mold 14. When viewed from the axial direction, the transfer surface 28 is arc-shaped. In this figure, a part of the circumferential end of the master model 26 is shown. The master model 26 includes a base body 30, a plate 32, and a plurality of blades 24. Figure 5 It is shown in Figure 1 three main grooves 34 corresponding to the three grooves 6 of Figure 5 . These main grooves 34 are successively called the first groove 34a, the second groove 34b, and the third groove 34c starting from near the front of Figure 5 . The second groove 34b corresponds to the second groove 6 in the tire 2 that has an undercut shape. However, in the base body 30, the second groove 34b does not have an undercut shape. There is no groove with an undercut shape in the base body 30. Each main groove 34 extends in the circumferential direction. The main groove 34 extends from one circumferential end of the outer surface of the base body 30 to the other end. In the

[0075] embodiment of Figure 5In the embodiment, the plate 32 is embedded in the second groove 34b. A part of the plate 32 is embedded in the second groove 34b, and the remaining part protrudes from the outer surface of the base body 30. Through this protrusion, a convex portion 38 is formed on the transfer surface 28 of the master model 26. The convex portion 38 extends from one circumferential end to the other end of the transfer surface 28. The plate 32 is typically made of resin. The plate 32 is formed by a 3D printer, for example.

[0076] As Figure 5 shown, each blade 24 is serrated. A part of the blade 24 is embedded in the main blade groove 36, and the remaining part protrudes from the outer surface of the base body 30.

[0077] In the process of (2) above, a liquid rubber material is flowed into the master model 26 and cured. The base body 30 and the plate 32 are removed from the composition of the master model 26 and the cured rubber material to obtain a rubber mold 40. In Figure 6 which, the rubber mold 40 is shown. The rubber mold 40 has a main body 41 and blades 24. In Figure 6 which, the metal strip 44 and the insert 46 to be installed in the next process are also shown. The surface (cavity surface 48) of the rubber mold 40 has a shape that is the reverse of the shape of the transfer surface 28. A concave portion 42 corresponding to the convex portion 38 of the transfer surface 28 is provided on the cavity surface 48. The concave portion 42 extends in the circumferential direction. The concave portion 42 extends from one circumferential end to the other end of the cavity surface 48.

[0078] In the process of (3) above, the metal strip 44 and the insert 46 are installed on the rubber mold 40 by using the concave portion 42 of the rubber mold 40. In Figure 6 which, the rubber mold 40 with the metal strip 44 and the insert 46 installed is shown. The insert 46 is installed at the end of the concave portion 42. The insert 46 extends inward from the end face 50 on the cavity surface 48. The insert 46 protrudes from the cavity surface 48. The metal strip 44 extends from the inner end 52 of the insert 46 on the cavity surface 48. The metal strip 44 extends continuously with the insert 46. The metal strip 44 protrudes from the cavity surface 48.

[0079] Figure 7 The (a) of Figure 6 and Figure 7 shows a perspective view of the insert 46. As Figure 6 and

[0080] Figure 7 The (b) of Figure 7Cross-sectional view taken along line VII(b)-VII(b) of (a). As Figure 7 As shown in (b), the insert 46 has a core portion 58 and a cover 60. The core portion 58 extends along the direction in which the insert 46 extends, inside the groove forming portion 54. The core portion 58 penetrates through the cover 60. The cover 60 covers the outer side of the core portion 58. The cover 60 extends along the direction in which the insert 46 extends. The core portion 58 and the cover 60 are formed of resin. In this embodiment, the cover 60 is softer than the core portion 58. The insert 46 is formed by a 3D printer, for example.

[0081] Figure 7 (c) is a rear view of the insert 46. As Figure 7 in (a) and Figure 7 as shown in (c), the insert 46 has a hole 61 on one end face. The insert 46 has a hole 61 on the face that contacts the metal strip 44 when the insert 46 is installed in the rubber mold 40. As Figure 7 shown in (c), the hole 61 is provided in the core portion 58. As Figure 7 shown in (a), the hole 61 extends along the direction in which the insert 46 extends.

[0082] In this embodiment, the insert 46 has an end portion 62 at the end on the side opposite to the face having the hole 61. The end portion 62 is made of the same material as the core portion 58. As Figure 7 shown in (d), the end portion 62 and the core portion 58 are integrally formed. As shown in this figure, by pulling the end portion 62, the core portion 58 can be pulled out from the cover 60. Alternatively, the insert 46 may not have the end portion 62.

[0083] Figure 8 is a perspective view showing the metal strip 44. As Figure 8 shown, the metal strip 44 has a groove forming portion 64 and a table portion 66. The groove forming portion 64 has the same shape as the groove forming portion 54 of the insert 46. The groove forming portion 64 has an undercut shape. The table portion 66 has a shape corresponding to the concave portion 42. The metal strip 44 has a protrusion 67 on one end face. Although not shown, the metal strip 44 also has a protrusion 67 on the other end face. The metal strip 44 has a protrusion 67 on the face that contacts the insert 46.

[0084] As Figure 6 shown, in this embodiment, the metal strip 44 is installed in the rubber mold 40 by fitting the table portion 66 into the concave portion 42. At this time, the protrusion 67 of the metal strip 44 is fitted into the hole 61 of the insert 46. The groove forming portion 64 protrudes from the cavity surface 48 of the rubber mold 40.

[0085] In the process of (4) above, the casting material is caused to flow into the rubber mold 40 in which the insert 46 and the metal strip 44 are installed and is cured. Typically, the casting material is gypsum. The rubber mold 40 is removed from the combination of the rubber mold 40 and the cured casting material. Thus, asFigure 9 As shown, a mold intermediate 72 is obtained that integrates the mold 68, the blade 24, the insert 46, and the metal strip 44. In Figure 9 A part of the surface of the mold intermediate 72 is shown. In this figure, a part of the circumferential end of the mold intermediate 72 is shown.

[0086] In the mold intermediate 72, the insert 46 extends inward from the end face 74 of the mold 68. The table portion 56 of the insert 46 protrudes from the surface of the mold 68, and the groove forming portion 54 of the insert 46 is buried in the mold 68. At this time, the outer surface of the cover 60 contacts the mold 68. The metal strip 44 extends from the inner end portion 52 of the insert 46. The metal strip 44 extends continuously with the insert 46. The protrusion 67 of the metal strip 44 is inserted into the hole 61 of the insert 46. The metal strip 44 is located at a position away from the end face 74 of the mold 68. The table portion 66 of the metal strip 44 protrudes from the surface of the mold 68, and the groove forming portion 64 of the metal strip 44 is buried in the mold 68.

[0087] In the above step (5), the insert 46 is separated from the mold 68. Thus, a mold 68 with the blade 24 and the metal strip 44 installed is obtained. This step includes:

[0088] (5-1) The step of pulling out the core portion 58; and

[0089] (5-2) The step of removing the cover 60.

[0090] Figure 10 is a perspective view showing the situation of the above step (5-1). In this figure, the core portion 58 is pulled out from the mold intermediate 72 of Figure 9 . As shown, the core portion 58 is pulled out from the circumferential end face 74 of the mold 68. At this time, the protrusion 67 of the metal strip 44 is pulled out from the hole 61 of the core portion 58. In this embodiment, by grasping the end portion 62 and pulling it circumferentially, the core portion 58 is pulled out together with the end portion 62.

[0091] Figure 11 is a perspective view showing the situation of the above step (5-2). As shown, in this step, the cover 60 is removed from the mold 68. By grasping the table portion 56 and pulling, the cover 60 is removed. Thus, a mold 68 with the blade 24 and the metal strip 44 installed is obtained. A groove 76 having an undercut shape corresponding to the shape of the groove forming portion 54 of the insert 46 is exposed on the surface of the mold 68. The groove 76 extends from the end face 74 of the mold 68 to the end of the metal strip 44.

[0092] The above step (6) includes:

[0093] (6-1) The step of obtaining the base mold of the combined mold; and

[0094] (6-2) Process of obtaining the combined mold.

[0095] In the process of (6-1) above, the liquid molding material is made to flow into the mold 68 equipped with the blade 24 and the metal strip 44 and solidifies. The mold 68 is removed from the composition of the mold 68 and the solidified molding material. Thus, the base mold 78 is obtained. Figure 12 The base mold 78 is shown in. The base mold 78 has a main body 80, a rib 82, and a blade 24. The rib 82 has a side portion 82a formed by solidifying the molding material that enters the groove 76 and a central portion 82b formed by the groove forming portion 64 of the metal strip 44.

[0096] The main body 80 and the side portion 82a are made of the same material and are formed integrally. The side portion 82a extends inward from the end face 84 of the base mold 78. The central portion 82b formed by the metal strip 44 extends from the inner end 52 of the side portion 82a. The central portion 82b extends continuously with the side portion 82a. The side portion 82a is formed so as to cover the protrusion 67 of the metal strip 44. That is, a hole is formed in the surface of the side portion 82a that contacts the metal strip 44, and the protrusion 67 is embedded in the hole. Both the side portion 82a and the central portion 82b have an undercut shape.

[0097] The metal strip 44 is harder than the side portion 82a and the main body 80. That is, the Vickers hardness of the metal strip 44 is greater than the Vickers hardness of the side portion 82a and the main body 80. The metal strip 44 is typically made of steel. In this embodiment, the metal strip 44 is made of stainless steel. The side portion 82a and the main body 80 are typically made of aluminum alloy.

[0098] In addition, in the present invention, the Vickers hardness is measured in accordance with JIS Z 2244 using a testing machine HM-200 manufactured by Mitutoyo Corporation. The test force F is set to 4.9 N.

[0099] In the process of (6-2) above, the end face 84 of the base mold 78 is processed to obtain the combined mold 14. Specifically, the end face 84 of the base mold 78 is cut with a cutting tool. The portions of the main body 80 and the side portion 82a on the side of the end face 84 are cut. Thus, the combined mold 14 is obtained. In the main body 80 of the base mold 78, the portion that is not cut and remains becomes the main body of the combined mold 14. In the side portion 82a of the base mold 78, the portion that is not cut and remains becomes the side portion of the rib of the combined mold 14. The central portion 82b of the base mold 78 becomes the central portion of the rib of the combined mold 14. The blade 24 of the base mold 78 becomes the blade 24 of the combined mold 14.

[0100] In the manufacture of this mold, other molding dies for the combined mold 14 are prepared. When all the components are ready, the manufacture of this mold is completed.

[0101] The manufacturing method of the tire of the present invention includes the following steps:

[0102] Manufacturing a mold; and

[0103] Pressurizing and heating a green tire.

[0104] In the step of manufacturing the mold, the mold is manufactured by the above method.

[0105] In the step of pressurizing and heating the green tire, the green tire of the tire is put into the mold. The green tire is pressed against the cavity surface of the mold and pressurized. At the same time, the green tire is heated. The rubber composition is caused to flow by pressurization and heating. The rubber is crosslinked by heating to obtain Tire 2. At this time, the undercut-shaped groove 6 of Tire 2 is formed by the undercut-shaped rib of the combined mold 14. The sipes 8 of Tire 2 are formed by the blades 24 of the combined mold 14.

[0106] Hereinafter, the effects of the present invention will be described.

[0107] In the manufacturing method of this embodiment, a base mold 78 having a main body 80, side portions 82a, and a metal strip 44 is formed, and the end face 84 of the base mold 78 is machined. The side portions 82a and the main body 80 are integrally formed of the same material. The side portions 82a extend inward from the end face 84. The metal strip 44 is separated from the end face 84. In the machining of the end face 84 of the base mold 78, the main body 80 and the side portions 82a formed of the same material are cut. The metal strip 44 is not cut. The machining of this end face 84 is easy. This helps to improve the dimensional accuracy of the forming mold. In this manufacturing method, a mold with high dimensional accuracy can be obtained.

[0108] In this manufacturing method, the central portion 82b formed of the metal strip 44 does not reach the end face 84. Even if the metal strip 44 is harder than the main body 80 and the side portions 82a, the metal strip 44 does not interfere with the machining of the end face 84. A hard metal strip 44 can be used without affecting the dimensional accuracy. By using a hard metal strip 44, a higher strength can be achieved at the central portion 82b of the rib 82.

[0109] In this manufacturing method, since the central portion 82b formed of the metal strip 44 does not reach the end face 84, even if the metal strip 44 is harder than the main body 80 and the side portions 82a, damage to the cutter during machining of the end face 84 can be suppressed.

[0110] In this manufacturing method, the metal strip 44 has a protrusion 67 on the surface in contact with the insert 46, and this protrusion 67 is inserted into the hole 61 of the insert 46. By flowing the molding material into the groove after separating the insert 46 and curing it, the side portion 82a of the rib 82 is formed. In this base mold 78, the protrusion 67 of the metal strip 44 is configured to be inserted into the hole 61 of the side portion 82a. This effectively improves the strength of the side portion 82a. A relatively high strength is achieved in the side portion 82a of this rib 82. It is possible to prevent the defect of the side portion 82a when machining the end face 84.

[0111] In this manufacturing method, by making the insert 46 and the metal strip 44 have an undercut shape, it is possible to form an undercut-shaped rib 82 in the base mold 78. By machining the end face 84 of this base mold 78, it is possible to fabricate a combined mold 14 with high dimensional accuracy. In this manufacturing method, even if the combined mold 14 has an undercut-shaped rib, it is possible to manufacture a combined mold 14 with good machining accuracy and relatively high strength.

[0112] In this manufacturing method, in the portion on the end face side of the combined mold 14, the main body and the side portion are integrally formed of the same material. The portion on the end face side of the combined mold 14 is formed of a single material. The portion on the end face side of the combined mold 14 adjacent to this combined mold 14 is also formed of the same single material. Thus, at the position (division position) where the end faces of these combined molds 14 are in contact with each other, it is possible to make the thermal expansion of the two combined molds 14 equal. As a result, compared with the combined mold 14 in which the rib and the main body are formed of different metals, it is possible to suppress the generation of a gap at the division position during vulcanization. The overflow of the rubber at the division position during vulcanization is suppressed.

[0113] In Figure 7 (a), the double-headed arrow L represents the length of the insert 46. The length L is preferably 8 mm or more. By making the length L 8 mm or more, a side portion 82a with a sufficient length for machining the end face 84 is formed in the base mold 78. When machining the end face 84, it is possible to prevent the entire side portion 82a from being machined and the metal strip 44 from being exposed. Also, by making the length L 8 mm or more, the handling of this insert 46 is easy. This helps to effectively manufacture the mold. From this perspective, the length L is more preferably 10 mm or more.

[0114] The length L is preferably 20 mm or less. By making the length L 20 mm or less, it is possible to increase the length of the metal strip 44 extending from the inner end portion 52 of the insert 46. By increasing the length of the hard metal strip 44, it is possible to achieve good manufacturing accuracy of the mold. In this manufacturing method, it is possible to manufacture the mold with high precision. From this perspective, the length L is more preferably 15 mm or less.

[0115] In Figure 8In this case, the double-headed arrow M represents the length of the protrusion 67 of the metal strip 44. The ratio of the length M to the length L (M / L) is preferably 0.5 or more. By making the ratio (M / L) 0.5 or more, the protrusion 67 effectively improves the strength of the side portion 82a. Thereby, it is possible to effectively prevent the occurrence of defects in the side portion 82a. Further, the protrusion 67 effectively contributes to improving the strength at the connection position between the central portion 82b and the side portion 82a. From this viewpoint, the ratio (M / L) is more preferably 0.6 or more.

[0116] The insert 46 has a core portion 58 and a cover 60 covering the core portion 58. In the process of separating the insert 46 from the mold 68, it is preferable to first pull out the core portion 58 and then remove the cover 60. In the mold intermediate 72, the cover 60 contacts the mold 68, and the core portion 58 does not contact the mold 68. Therefore, when the core portion 58 is pulled out, breakage of the mold 68 is suppressed. Further, since the cover 60 after the core portion 58 is pulled out has a cavity in the central portion, it is easily deformed toward the center. By deforming the cover 60 toward the center, the frictional force between the cover 60 and the mold 68 when the cover 60 is removed can be reduced. When the cover 60 is removed, breakage of the mold 68 is prevented. In this manufacturing method, breakage of the mold 68 when the insert 46 is separated from the mold 68 is suppressed.

[0117] Preferably, the core portion 58 and the cover 60 are formed of resin. Thereby, the frictional force between the core portion 58 and the cover 60 can be suppressed to a low level. This makes it easy to pull out the core portion 58. In this method, breakage of the mold 68 when the core portion 58 is pulled out is suppressed. Further, the cover 60 made of resin can be easily deformed after the core portion 58 is pulled out. Thereby, breakage of the mold 68 when the cover 60 is removed can be prevented. In this manufacturing method, breakage of the mold 68 when the insert 46 is separated from the mold 68 is suppressed.

[0118] The cover 60 is preferably softer than the core portion 58. Deformation of the insert 46 during preparation of the mold intermediate 72 is suppressed by the hard core portion 58. Thereby, a groove having an undercut shape can be formed on the mold 68 with high precision. In this manufacturing method, excellent manufacturing accuracy of the combination mold 14 is achieved. Further, the soft cover 60 can be more easily deformed after the core portion 58 is pulled out. Thereby, breakage of the mold 68 when the cover 60 is removed can be prevented. In this manufacturing method, breakage of the mold 68 when the insert 46 is separated from the mold 68 is suppressed.

[0119] The hardness Hc of the core portion 58 is preferably 80 or more. By making the hardness Hc 80 or more, deformation of the insert 46 during preparation of the mold intermediate 72 is suppressed. Thereby, a groove having an undercut shape is formed on the mold 68 with high precision. In this method, excellent manufacturing accuracy of the combination mold 14 is achieved. From the viewpoint of being able to manufacture inexpensively and easily, the hardness Hc of the core portion 58 is preferably 100 or less.

[0120] The hardness Ho of the cover 60 is preferably 40 or less. By making the hardness Ho 40 or less, the cover 60 can be easily deformed after the core 58 is pulled out. Thereby, breakage of the mold 68 when the cover 60 is removed can be prevented. In this manufacturing method, breakage of the mold 68 when the insert 46 is separated from the mold 68 is suppressed. From this viewpoint, the hardness Ho of the cover 60 is more preferably 35 or less. The hardness Ho is preferably 20 or more. By making the hardness Ho 20 or more, the cover 60 has sufficient strength. Breakage of the cover 60 during the manufacturing process of the mold is prevented. From this viewpoint, the hardness Ho of the cover 60 is more preferably 25 or more.

[0121] In the present invention, both the hardness Hc and the hardness Ho are the shear A hardness. The hardness Hc and the hardness Ho are measured by a type A hardness tester based on the provisions of "JIS K7215". The hardness tester is pressed against Figure 7 the cross-section shown to measure the hardness. The measurement is carried out at a temperature of 23 °C.

[0122] The thickness T of the cover 60 is measured at the position where the core 58 exists in the groove forming portion 54. The thickness T of the cover 60 is the distance between the outer surface and the inner surface (the surface in contact with the core 58) of the cover 60 measured along the normal line of the outer surface of the cover 60 in the groove forming portion 54. In Figure 7 the embodiment of [], the thickness is substantially constant throughout the entire portion of the cover 60 in contact with the core 58 in the groove forming portion 54. The thickness may also vary depending on the location. In this case, the average thickness of the entire portion of the cover 60 in contact with the core 58 in the groove forming portion 54 is the thickness T.

[0123] The thickness T of the cover 60 is preferably 1.0 mm or less. By making the thickness T 1.0 mm or less, the cover 60 can be easily deformed after the core 58 is pulled out. Thereby, breakage of the mold 68 when the cover 60 is removed can be prevented. In this manufacturing method, breakage of the mold 68 when the insert 46 is separated from the mold 68 is suppressed. From this viewpoint, the thickness T is more preferably 0.8 mm or less. The thickness T is preferably 0.2 mm or more. By making the thickness T 0.2 mm or more, the cover 60 has sufficient strength. Breakage of the cover 60 during the manufacturing process of the mold is prevented. From this viewpoint, the thickness T is more preferably 0.4 mm or more.

[0124] In this method, by providing the convex portion 38 on the base body 30, forming the concave portion 42 on the rubber mold 40, installing the insert 46 and the metal strip 44 on the concave portion 42 and flowing the mold material therein, a mold intermediate 72 in which the mold 68, the insert 46 and the metal strip 44 are integrated is obtained. This method is simple. In this method, the mold intermediate 72 can be easily prepared. This helps to improve the productivity of the mold 10.

[0125] In the embodiment described above, the combined mold 14 has a rib with an undercut shape. The present invention can also be applied to the manufacture of a mold having a rib with an undercut shape that is not a combined mold.

[0126] As described above, according to the present invention, even in a mold having a rib with an undercut shape, the mold can be easily and inexpensively manufactured. Thus, the advantages of the present invention are obvious.

[0127] Industrial applicability

[0128] The method described above can also be applied to the manufacture of various molds for tires.

Claims

1. A manufacturing method of a mold, which comprises the following processes: Process A, separating the insert from the mold integrated with the insert and the metal strip, so that the surface of the mold exposes a groove corresponding to the insert; and Process B, flowing a molding material into the above mold and curing it to obtain a molded die having a rib corresponding to the above groove, In the integrated mold in the above Process A, the insert extends inward from the end face of the mold, the metal strip extends continuously with the insert from the inner end of the insert, and a protrusion is embedded in a hole provided on the surface of the insert in contact with the metal strip, and the protrusion is provided on the surface of the metal strip in contact with the insert.

2. The manufacturing method of the mold according to claim 1, wherein, the length of the above protrusion is 0.5 times or more of the length of the above insert.

3. The manufacturing method of the mold according to claim 1 or 2, wherein, the above Process B comprises the following processes: Process B1, flowing a molding material into the above mold and curing it to obtain a base die having a rib corresponding to the above groove and the above metal strip; and Process B2, machining the end face of the above base die to obtain a molded die.

4. The manufacturing method of the mold according to claim 1 or 2, wherein, before the above Process A, the following process is further included: Process C1, obtaining a master model, which has a convex portion on its transfer surface; Process C2, forming a rubber mold, which has a cavity surface with a shape reverse to that of the above transfer surface and an end face extending from the end of the cavity surface, and has a concave portion corresponding to the above convex portion and extending from the above end face on the cavity surface; Process C3, using the above concave portion to install an insert and a metal strip on the above rubber mold, the insert extends inward from the above end face and protrudes from the above cavity surface, and the metal strip extends continuously from the insert and protrudes from the above cavity surface; and Process C4, flowing a mold material into the above rubber mold and curing it to obtain a mold integrated with the above insert and the above metal strip.

5. The manufacturing method of the mold according to claim 1 or 2, wherein, the above groove has an undercut shape.

6. The manufacturing method of the mold according to claim 1 or 2, wherein, the above insert has a core part and a cover covering the core part, the above Process A comprises the following processes: Process A1, pulling out the above core part from the above mold; and Process A2, removing the above cover from the above mold.

7. The manufacturing method of the mold according to claim 6, wherein, the above core part and the cover are formed of resin.

8. The manufacturing method of the mold according to claim 6, wherein, the above cover is softer than the above core part.

9. The manufacturing method of the mold according to claim 8, wherein, the hardness of the above core part measured by a type A durometer based on the provisions of "JIS K7215" is 80 or more.

10. The manufacturing method of the mold according to claim 8, wherein, the hardness of the above cover measured by a type A durometer based on the provisions of "JIS K7215" is 20 or more and 40 or less.

11. The manufacturing method of the mold according to claim 6, wherein, The thickness of the above-mentioned cover is 0.2 mm or more and 1.0 mm or less.

12. The method for manufacturing a mold according to claim 1 or 2, wherein, the above-mentioned metal strip has an undercut shape.

13. The method for manufacturing a mold according to claim 1 or 2, wherein, the above-mentioned metal strip is harder than the rib formed by curing the above-mentioned molding material.

14. The method for manufacturing a mold according to claim 13, wherein, the material of the above-mentioned metal strip is steel, and the material of the above-mentioned rib is aluminum alloy.

15. The method for manufacturing a mold according to claim 1 or 2, wherein, the length of the above-mentioned insert is 8 mm or more and 20 mm or less.

16. A method for manufacturing a tire, which comprises the following steps: manufacturing a mold by the method for manufacturing a mold according to any one of claims 1 to 15; and pressing and heating a green tire in the above-mentioned mold.

17. A tire mold, wherein, the tire mold has a forming mold, the forming mold has a cavity surface and an end surface extending from an end of the cavity surface, the above-mentioned forming mold has a main body and ribs protruding from the main body in the above-mentioned cavity surface, the above-mentioned rib has a side portion extending inward from the above-mentioned end surface and a central portion continuously extending from the side portion, the side portion has a hole in the surface in contact with the central portion, and the central portion has a protrusion in the surface in contact with the side portion, and the protrusion is embedded in the hole, the side portion and the main body are integrally formed of the same material, the central portion is formed of a metal harder than the side portion.

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