Mold for tire manufacturing

Abstract

Provided is a mold for tire manufacturing that can reduce the release resistance of a void molded member. A mold for tire manufacturing (22) includes a mold main body (40) for molding a tread surface, and a void molded member (42) made of a material different from the mold main body (40) and for molding a void such as a sipe in the tread surface. The void molded member (42) is made by metal molding based on a 3D printer, and the upper portion of a protrusion (48) in the unevenness of a surface (46) formed by the metal molding is flattened to form a flat top surface (48A).

Description

Technical Field

[0001] Embodiments of the present invention relate to molds for tire manufacturing. Background Technology

[0002] There exists a type of tire with sipes and other gaps on its tread surface. In the mold used to manufacture the tread surface of the tire with such gaps, the gap forming part used to form the gaps is made of a different material than the mold body. For example, for lightweight purposes, the mold body is made of a soft metal such as aluminum, while from the viewpoint of strength, the gap forming part is made of an ferrous metal.

[0003] Patent Document 1 describes a method for forming specific uneven surfaces on the surface of a cutting tool with serrated patterns to improve the rigidity of the block. Patent Document 1 also describes a method for manufacturing this cutting tool using a layering molding process.

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-185901 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Due to the increasing performance requirements of tires, there is a growing trend towards complex groove shapes in tire manufacturing molds. Among the elements constituting tread design, particularly for cavitation molded parts used to form groove patterns with a thickness of 2 mm or less, there are molded parts obtained by stamping ferrous metals. In addition, as cavitation molded parts, there are also molded parts that utilize a layering molding method, i.e., a 3D printer, as described in Patent Document 1 above.

[0009] In tire manufacturing using such void-formed parts, the unevenness of the void-formed part's surface can increase the demolding resistance of the vulcanized void-formed part from the tire. Especially in void-formed parts used to form dart patterns with complex shapes, the increased demolding resistance leading to poor tire demolding becomes a major cause of reduced productivity.

[0010] In view of the above problems, the purpose of the embodiments of the present invention is to provide a mold for tire manufacturing that can reduce the demolding resistance of void-formed parts.

[0011] Methods for solving problems

[0012] The present invention includes the embodiments shown below.

[0013] [1] A tire manufacturing mold comprises: a mold body for forming a tire tread surface; and a void forming component made of a material different from the mold body and used for forming voids on the tire tread surface, wherein...

[0014] The void-shaped part is made by metal molding based on a 3D printer, and the upper part of the protrusion in the surface formed by the metal molding is flattened to form a flat top surface.

[0015] [2] According to the tire manufacturing mold described in [1], the surface formed by the metal forming has an arithmetic mean roughness Ra of 3.0 to 7.0 μm and a skewness Rsk > 0, and the skewness is set to Rsk < 0 by the planarization.

[0016] [3] According to the tire manufacturing mold described in [1] or [2], a flat top surface is formed by cutting off the upper part of the protrusion formed by the metal shaping.

[0017] [4] A tire manufacturing mold according to any one of [1] to [3], wherein the void forming member has a narrow portion between the protruding flat top surface and the recessed bottom.

[0018] [5] According to the tire manufacturing mold of [4], the narrow portion is formed by applying pressure to the upper part of the protrusion formed by the metal forming to reduce its height, thereby forming the narrow portion, and then the flat top surface is formed by cutting off the upper part of the protrusion while retaining the narrow portion.

[0019] [6] According to the tire manufacturing mold of [4] or [5], the narrow portion is provided in the depth direction of the recess at a position closer to the opening side of the recess than half the depth.

[0020] [7] A tire manufacturing mold according to any one of [1] to [6], wherein the void forming part is made of stainless steel.

[0021] [8] A tire manufacturing mold according to any one of [1] to [7], wherein the surface of the void forming part is formed by the flat top surface of the truncated protrusion and the recess.

[0022] [9] A tire manufacturing mold according to any one of [1] to [8], wherein the recess on the surface of the void forming part has an elongated opening shape in which the long dimension of its opening face is 2 to 10 times the short dimension.

[0023]

[10] A tire manufacturing mold according to any one of [1] to [9], wherein the interval between the recesses on the surface of the void forming part is 0.2 to 1.5 mm.

[0024] Invention Effects

[0025] If implemented according to the present invention, the demolding resistance of the void molded part can be reduced, and the poor demolding of the vulcanized tire can be reduced. Attached Figure Description

[0026] Figure 1 This is a half-section view of a tire vulcanizing unit.

[0027] Figure 2 A cross-sectional view of a tire manufacturing mold according to an embodiment (and) Figure 3 (The sectional view corresponding to line II-II).

[0028] Figure 3 This is a partial top view of the tire tread according to one embodiment.

[0029] Figure 4 This is a side view of a void-formed part according to one embodiment.

[0030] Figure 5 This is a schematic diagram showing the cross-sectional shape of the surface of the void-formed part according to the first embodiment.

[0031] Figure 6 It is a schematic diagram showing the concave and convex cross-sectional shape formed by metal shaping.

[0032] Figure 7 It is an enlarged image showing the surface of a hollow molded part before it is planarized, created by metal shaping.

[0033] Figure 8 This is a top view showing the surface of the void-formed part according to the first embodiment.

[0034] Figure 9 This is a schematic diagram showing the cross-sectional shape of the surface of the void-formed part according to the second embodiment.

[0035] Figure 10 This is a schematic diagram showing the cross-sectional shape during the stage of stamping the surface of the void-formed part produced by metal forming in the second embodiment. Detailed Implementation

[0036] The inventors focused on the surface properties of the void-formed parts in order to reduce the demolding resistance of the void-formed parts. Moreover, the inventors found that a surface with a moderately uneven shape, resembling pits, is preferred over a smooth surface obtained by stamping rolled steel with an arithmetic mean roughness Ra of 1.0 μm.

[0037] In detail, on the smooth surface obtained by stamping rolled steel, unvulcanized rubber is vulcanized in a close-packed state over the entire surface, resulting in a large contact area between the vulcanized rubber and the void-formed part. Therefore, the demolding resistance is high. To reduce demolding resistance, it is preferable to reduce the contact area; for this purpose, it is advisable to provide minute irregularities on the surface of the void-formed part.

[0038] When creating void-shaped parts using metal molding based on a 3D printer, tiny bumps and depressions are formed on the surface of the void-shaped part based on the metal molding. However, if the void-shaped part with such bumps and depressions is directly used for vulcanization molding, the unvulcanized rubber enters the depressions and solidifies, thus increasing the demolding resistance.

[0039] Therefore, a countermeasure is adopted to flatten the upper part of the protrusions in the aforementioned surface irregularities. As a result, the surface of the void molded part is formed by the flattened top surface of the protrusions and the recesses. In this case, during the initial stage of vulcanization, when the unvulcanized rubber flows on the surface of the void molded part, the heating at the flat top surface of the protrusions promotes the vulcanization of the outermost part of the unvulcanized rubber. This reduces the adhesiveness of the unvulcanized rubber, making it difficult for it to penetrate into the recesses. Therefore, the adhesion force in the recessed area is reduced, thus lowering the demolding resistance.

[0040] Hereinafter, one embodiment will be described with reference to the accompanying drawings.

[0041] Figure 1 An example of a tire vulcanizing apparatus 10 for vulcanizing an inflatable tire is shown. The tire vulcanizing apparatus 10 includes a vulcanizing mold 12, a container 14 for mounting the vulcanizing mold 12, and an air bladder 16, which vulcanizes an unvulcanized tire while molding it into a given shape.

[0042] The vulcanizing mold 12 has a pair of upper and lower side plates 18 and 20, multiple sector blocks 22 divided circumferentially, and a pair of upper and lower bead rings 24 and 26, forming the outer surface of the tire T. The sector blocks 22 are molds used to form the tread surface T1 of the tire T. The sector blocks 22 are divided into multiple segments along the tire circumference and are configured to expand and contract along the tire radius.

[0043] The container 14 includes: a plurality of sector segments 28 holding the sector block 22; a collar 30 for moving the sector segments 28 along the tire radius; and a pair of upper and lower mounting plates 32, 34. The collar 30 moves the sector segments 28 along the tire radius by moving them up and down relative to each other. Thus, the sector block 22 is configured to expand and contract in the tire radius. The upper mounting plate 32 is configured to move up and down relative to the lower mounting plate 34 via a lifting device (not shown).

[0044] The airbag 16 is made of annular expandable rubber elastomer. The airbag 16 is disposed on the inner side of the tire T and inflates by the supply of pressurized gas, thereby pressurizing the tire T from the inside.

[0045] The following description will focus on the sector block 22, which serves as a mold for forming the tread surface T1 (i.e., the design surface of the tread) of a tire T. In the following description, the sector block 22 will be referred to as "tire manufacturing mold 22" or simply "mold 22".

[0046] like Figure 2 As shown, mold 22 includes: a mold body 40 for forming the tread surface T1; and a void forming element 42 for forming voids on the tread surface T1. Typically, multiple void forming elements 42 are embedded in the mold body 40. That is, mold 22 is manufactured by embedding the void forming elements 42 into the mold body 40. Embedding generally refers to the process of flowing molten metal around a dissimilar component to obtain a casting integrated with the main body. Here, embedding refers to obtaining mold 22 where the void forming elements 42 are integrated with the mold body 40 by flowing molten metal in, using them as inserts.

[0047] The mold body 40 is made of soft metals such as aluminum or aluminum alloy. The mold body 40 has a tread forming surface 40A for forming the tread surface T1. On the tread forming surface 40A, there are ribs 44 that form the main groove (i.e., the circumferential groove) on the tread surface T1. The ribs 44 are protrusions from the tread forming surface 40A and extend along the circumference of the tire, and are integrally formed with the mold body 40.

[0048] The void forming part 42 is made of a different material than the mold body 40. From the viewpoint of strength, it is preferable to be made of an ferrous metal. More preferably, the void forming part 42 is made of stainless steel. Stainless steel has excellent rust resistance compared to iron, and the adhesion to the vulcanized rubber can also be reduced compared to iron. More preferably, the void forming part 42 is made of stainless steel with a nickel (Ni) content of 8% by mass or less (more preferably 5% by mass or less). By reducing the nickel content, the adhesion to the vulcanized rubber can be further reduced.

[0049] Examples of the gaps formed by the gap forming part 42 include various recesses provided on the tread surface T1, but groove-shaped recesses are preferred, such as sipes and grooves. Here, a sipe is a notch with a width of 2 mm or less, also called a cut. A groove is a groove with a width narrower than the main groove, for example, a groove with a width of 5 mm or less. Sipes and grooves can extend along the tire circumference or along the tire width direction.

[0050] Figure 3 This is a top view showing an example of a tread surface T1 formed by mold 22. Multiple main grooves T2 are provided on the tread surface T1. On the tread surface T1, on the ribs T3 extending circumferentially and divided by the main grooves T2, multiple dart patterns T4 extending in the tire width direction are also provided. In one embodiment, a void forming element 42 is used to form the dart patterns T4. Figure 2 as well as Figure 3 In the diagram, the symbol CL represents the equatorial plane of the tire.

[0051] Furthermore, the void-formed part 42, when in the case of a groove-shaped recess, takes the form of a plate. During molding... Figure 3 In the case of the groove pattern T4 shown, the void forming part 42 is a flat plate with curved portions at both ends in the long side direction. The shape of the void forming part 42 is not limited to this. For example, if the formed recess is straight in plan view (opening shape), the entire long side of the void forming part 42 can be flat. Furthermore, if the formed recess is a curved line in plan view, the void forming part 42 can also be a curved plate. If the formed recess is a line with curved portions in plan view, the void forming part 42 can also be a plate with curved portions. If the formed recess is wavy in plan view, the void forming part 42 can also be a corrugated plate.

[0052] Figure 4 This diagram shows an example of a void-forming part 42. The portion of the void-forming part 42 that protrudes from the mold body 40 to form the void is called the forming part 42A, and the portion embedded in the mold body 40 is called the embedding part 42B. Figure 4 In the diagram, the embedded part 42B is shown by adding a shaded line.

[0053] In this embodiment, the void-shaped part 42 is manufactured using 3D printer-based metal molding (also known as metal lamination molding). Metal molding refers to a technique that creates a three-dimensional shape by fusing and stacking metal powder layer by layer. Examples of metal molding techniques include SLS (Selective Laser Sintering) and SLM (Selective Laser Melting). In these metal molding techniques, metal powder is selectively sintered or melted by irradiating a support plate with a laser beam, thereby shaping the object layer by layer according to the desired shape.

[0054] On the surface 46 of the void-formed part 42 produced in this manner, tiny irregularities are formed by the metal shaping. That is, as... Figure 6 As schematically shown, the surface 46 of the void forming part 42 is formed as a convex-concave surface including a plurality of protrusions 48 and a plurality of recesses 50. Figure 7 This is an image showing the surface 46 of the void-shaped part 42 formed by metal shaping. The whiter the color, the higher it is, i.e., raised, and the lower it is, i.e., recessed, as the color becomes darker.

[0055] In this embodiment, the upper part (i.e., the top) of the protrusion 48 in the unevenness of the surface 46 formed by the above-described metal shaping is as follows: Figure 5 The surface is planarized to form a flat top surface 48A. That is, the top surface 48A of the protrusion 48 is formed as a flat surface (smooth surface). Thus, in this embodiment, the void-shaped part 42 is manufactured by metal molding based on a 3D printer, and the upper part of the protrusion 48 in the unevenness of the surface 46 formed by the metal molding is planarized to form a flat top surface 48A, thereby obtaining a void-shaped part 42 having a flat top surface 48A and a recess 50.

[0056] In the first embodiment, the upper part of the protrusion 48 is removed by shaping the uneven surface formed by metal forming, thereby flattening the upper part and forming a truncated protrusion 48 with a flat top surface 48A. Therefore, the surface 46 of the void forming part 42 is formed by the top surface 48A of the truncated protrusion 48 and the recess 50. As for the method of removing the upper part of the protrusion 48, there is no particular limitation as long as the upper part of the protrusion 48 can be removed to form a flat surface; it can be a cutting process or a grinding process. Figure 8 This is a top view showing an example of a flattened surface 46, with recesses 50 disposed between the top surfaces 48A of the truncated protrusions 48.

[0057] Therefore, in the initial stage of tire vulcanization, when the unvulcanized rubber flows on the surface 46 of the void molded part 42, the heating at the flat top surface 48A of the protrusion 48 promotes the vulcanization of the extreme surface portion of the unvulcanized rubber. As a result, the adhesiveness of the rubber decreases, making it difficult for the rubber to enter the recess 50. Consequently, the adhesion of the vulcanized rubber decreases, reducing demolding resistance.

[0058] Furthermore, the planarized surface 46 can be any surface of the molding part 42A (i.e., the two sides of the molding part 42A in the case of the plate-shaped void molding part 42). The surface of the embedded part 42B may or may not be planarized.

[0059] In one embodiment, the surface 46 of the metal forming after molding (before planarization) preferably has an arithmetic mean roughness Ra of 3.0 to 7.0 μm and a roughness parameter skewness Rsk of positive value (Rsk > 0). Furthermore, in the product shape of the void forming part 42, it is preferable to planarize the upper part of the protrusion 48 with a negative skewness Rsk (Rsk < 0). By setting the surface 46 to Rsk < 0, the ratio of the flat top surface 48A to the recess 50 becomes appropriate, which can more effectively reduce the demolding resistance of the void forming part 42. Additionally, the arithmetic mean roughness Ra of the top surface 48A of the protrusion 48 is not particularly limited, but is preferably 2.0 μm or less.

[0060] Here, the arithmetic mean roughness Ra and skewness Rsk are measured according to the 2001 edition of JIS B0601.

[0061] In the product shape of the void-formed part 42, the longer dimension 50B of the opening surface of each recess 50 is preferably 2 to 10 times the shorter dimension 50C. By making the opening shape of the recess 50 elongated, the intrusion of rubber into the recess 50 can be further reduced. Here, the longer dimension 50B of the recess 50 refers to... Figure 8 As shown, the contour of the opening surface of the recess 50 is detected, and the longitudinal dimension of the rectangle 52 is determined when the contour is fitted to the inscribed rectangle 52. The so-called short dimension value 50C refers to the lateral dimension of the rectangle 52.

[0062] Furthermore, in the product shape of the void-formed part 42, the spacing G of the recesses 50 is not particularly limited, for example, preferably 0.2 to 1.5 mm, more preferably 0.5 to 1.0 mm. By setting the spacing G of the recesses 50 to such a range, low-density contact areas formed by the recesses 50 are arranged at appropriate intervals between the top surfaces 48A with high adhesion to the vulcanized rubber. Therefore, a further reduction in demolding resistance can be achieved. Here, the spacing G of the recesses 50 is the arrangement spacing of the recesses 50, such as... Figure 6 As shown, this is the center-to-center distance between adjacent depressions 50 and 50.

[0063] Figure 9 This is a schematic diagram showing the cross-sectional shape of the surface 46 of the void-formed part 42X according to the second embodiment. In the second embodiment, a narrow portion 54 is provided between the flat top surface 48A of the protrusion 48 and the bottom 50A of the recess 50, which is different from the first embodiment.

[0064] The so-called narrow portion 54 refers to the narrow portion from the bottom 50A of the recess 50 to the top surface 48A, in which the shape of the recess 50 is temporarily expanded and then narrowed. The narrow portion 54 is as follows... Figure 9 As shown, the narrow portion 54 is preferably located near the opening surface (i.e., top surface 48A) of the recess 50. That is, the narrow portion 54 is preferably located in the depth direction of the recess 50 at a position closer to the opening surface than half its depth. By providing the narrow portion 54 in the void molded part 42X in this way, the intrusion of rubber into the recess 50 can be more effectively suppressed.

[0065] The void-formed part 42X having the aforementioned narrow portion 54 can be manufactured as follows: The narrow portion 54 is formed by plastically deforming the upper part of the protrusion 48, which is formed by metal forming, in a manner that reduces its height. A flat top surface 48A is then formed by cutting away the upper part of the protrusion 48 while retaining the narrow portion 54. This plastic deformation can be achieved by stamping or shot peening the uneven surface 46 formed by metal forming.

[0066] In detail, when... Figure 6 When the shaped metal surface 46 is stamped, pressure is applied to the upper part of the protrusion 48 in a manner that reduces its height. As a result, the upper part of the protrusion 48 is compressed and plastically deformed, thus expanding in an eaves-like shape, as... Figure 10 As shown, a narrow portion 54 is formed on the upper part of the protrusion 48. Similarly, for shot peening, pressure is applied to the upper part of the protrusion 48 in a manner that reduces its height by causing numerous spheres to collide at high speed (the instantaneous pressing force generated by the collision of numerous spheres). As a result, the upper part of the protrusion 48 plastically deforms and expands in an eave-like shape, forming the narrow portion 54.

[0067] Next, while retaining the narrow portion 54, its upper part is flatly removed by cutting or grinding, thereby achieving the desired result. Figure 9 The top surface 48A is formed as shown. In this way, after plastic deformation by stamping or the like, the upper part is removed by cutting or the like, thereby easily obtaining a void-formed part 42X with a narrow part 54.

[0068] Regarding the second embodiment, the other structures are the same as those in the first embodiment, and the description is omitted.

[0069] In this embodiment, when manufacturing the void-formed parts 42 and 42X, it is preferable to perform solution heat treatment to reduce the hardness after forming the integral shape by metal forming. This allows for the improvement of FB223915JP-I.

[0070] The machinability is improved by the aforementioned stamping, shot peening, cutting, or grinding processes. Preferably, after the surface 46 of the void-formed part 42, 42X is formed into the desired shape by these processes, an age-hardening heat treatment is performed, thereby improving the strength of the uneven shape of the surface 46.

[0071] The above embodiments are provided as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the spirit of the invention.

[0072] Symbol Explanation

[0073] 22… mold for tire manufacturing; 40… mold body; 42, 42X… void forming part; 46… surface of void forming part; 48… protrusion; 48A… top surface; 50… recess; 54… narrow part.

Claims

1. A mold for tire manufacturing, comprising: A mold body for forming the tread surface; and a void forming component, made of a different material from the mold body, for forming voids on the tread surface, wherein... The void-shaped part is manufactured by metal molding based on a 3D printer. The upper part of the protrusions in the uneven surface formed by the metal molding is flattened to form a flat top surface. The surface of the void-formed part, which has an arithmetic mean roughness Ra of 3.0–7.0 μm and a skewness Rsk > 0 formed by the metal forming process, has its skewness set to Rsk < 0 by the planarization process. The void-shaped part has a narrow portion between the protruding, flat top surface and the recessed bottom surface.

2. The tire manufacturing mold according to claim 1, wherein, A flat top surface is formed by shaving off the upper part of the protrusion formed by the metal shaping.

3. The tire manufacturing mold according to claim 1, wherein, The narrow portion is formed by applying pressure to the upper part of the protrusion formed by the metal shaping in a way that reduces its height, thereby plastically deforming it, and then the flat top surface is formed by cutting off the upper part of the protrusion while retaining the narrow portion.

4. The tire manufacturing mold according to any one of claims 1 to 3, wherein, The narrow portion is positioned at a point on the opening side of the recess at a depth greater than half the depth in the direction of the recess.

5. The mold for tire manufacturing according to any one of claims 1 to 3, wherein, The void-formed part is made of stainless steel.

6. The tire manufacturing mold according to any one of claims 1 to 3, wherein, The surface of the void-shaped part is formed by the flat top surface of the truncated protrusion and the recess.

7. The tire manufacturing mold according to any one of claims 1 to 3, wherein, The recess on the surface of the void-formed part has an elongated opening shape in which the length of the opening face is 2 to 10 times the length of the short face.

8. The mold for tire manufacturing according to any one of claims 1 to 3, wherein, The interval between the depressions on the surface of the void-formed part is 0.2 to 1.5 mm.

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