Tire vulcanization mold and method of manufacturing pneumatic tire

Abstract

To provide a tire vulcanization mold that is capable of removing air between an outer surface of a bead part and a bead molding surface during tire vulcanization.SOLUTION: A tire vulcanization mold 1 is used to vulcanize and mold a pneumatic tire T having a bead part Tb. The tire vulcanization mold includes a bead ring 2 having a bead molding surface 5 for contacting an outer surface of the bead part Tb to mold the bead part Tb. At least a portion of the bead molding surface 5 includes a ventilation part 6 formed of a porous metal having air permeability.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a tire vulcanizing mold. [Background technology]

[0002] Patent Document 1 below describes a tire vulcanization mold for molding pneumatic tires. The tire vulcanization mold includes a bead ring having a bead molding surface that molds the outer surfaces of the bead portions of the tire. The bead ring is provided with a vent flow path that forms a vent hole with one end communicating with the outside of the mold and the other end opening at the bead molding surface, and a groove-like vent line that extends to the vent hole. During vulcanization, this tire vulcanization mold discharges air between the raw tire and the bead ring from the vent line to the vent flow path, thereby preventing molding defects in the outer surfaces of the bead portions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-209958 Summary of the Invention [Problem to be solved by the invention]

[0004] In tire vulcanizing molds having the above-described vent lines and vent holes, protrusions such as convex portions extending in the tire circumferential direction, which are the inverse patterns of the vent lines, and spews sucked into the vent flow paths are formed on the outer surfaces of the bead portions of pneumatic tires. Such protrusions reduce the adhesion between the bead portions of the pneumatic tire and the rim, and may cause rim slippage or air leakage.

[0005] The present invention was devised in view of the above problems, and its main objective is to provide a tire vulcanization mold that is capable of removing air between the outer surface of the bead portion and the bead molding surface during tire vulcanization, even without providing the above-mentioned vent holes or vent lines, or even with these significantly reduced. [Means for solving the problem]

[0006] The present invention is a tire vulcanization mold for vulcanizing and molding a pneumatic tire having a bead portion, comprising a bead ring having a bead molding surface for contacting the outer surface of the bead portion to mold the bead portion, and at least a portion of the bead molding surface includes a ventilation portion formed of a porous metal having air permeability. [Effects of the Invention]

[0007] By adopting the above-described configuration, the tire vulcanization mold of the present invention can remove air between the outer surface of the bead portion and the bead molding surface during tire vulcanization without providing vent holes or vent lines or even by significantly reducing these. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of a vulcanizing mold showing one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of a pneumatic tire manufactured in the vulcanization mold of FIG. 1. [Figure 3] FIG. 2 is an enlarged view of the bead ring of FIG. [Figure 4] FIG. 3 is a partial perspective view of the pneumatic tire of FIG. 2. [Figure 5] FIG. 4 is an exploded perspective view of the bead ring of FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described below with reference to the drawings. The drawings are intended to illustrate the features of the present invention, but may include exaggerated representations and representations that differ from the dimensional ratios of the actual structure to facilitate understanding of the present invention. Furthermore, identical or common elements are designated by the same reference numerals throughout the embodiments, and redundant explanations will be omitted. Furthermore, well-known configurations may be appropriately adopted for configurations not described in this specification.

[0010] FIG. 1 is a cross-sectional view of a tire vulcanization mold (hereinafter, sometimes simply referred to as a "vulcanization mold") 1 showing one embodiment of the present invention. FIG. 1 shows a cross section of a portion of the vulcanization mold 1. As shown in FIG. 1, the vulcanization mold 1 of this embodiment has, inside thereof, a molding surface 1a that molds the outer surface of a pneumatic tire (hereinafter, sometimes simply referred to as a "tire") T. A tire before vulcanization (hereinafter, sometimes referred to as a "raw tire") T is heated in the vulcanization mold 1 and is pressed (vulcanized) from the inner cavity side toward the molding surface 1a by an expanded bladder (not shown), thereby producing a tire (vulcanized) T.

[0011] In this specification, the tire axial direction when the tire T is mounted on the vulcanization mold 1 is referred to as the mold axial direction, the tire circumferential direction is referred to as the mold circumferential direction, and the tire radial direction is referred to as the mold radial direction. When the tire T is mounted on the vulcanization mold 1, the tire T is placed horizontally with its tire rotation axis (not shown) vertical.

[0012] Fig. 2 is a cross-sectional view of a tire T molded by the vulcanizing mold 1 of this embodiment. As shown in Fig. 2, the tire T is preferably for a motorcycle. However, the tire T molded by the vulcanizing mold 1 of this embodiment may also be for a passenger car or a heavy load.

[0013] As shown in Fig. 2, the tire T includes bead portions Tb. In this embodiment, the bead portions Tb are provided on both sides in the tire axial direction. Note that a bead core Tc is embedded in the bead portions Tb. The tire T also includes a pair of sidewall portions Ts connected to the outer sides of the pair of bead portions Tb in the tire radial direction, and a tread portion Ta connecting the pair of sidewall portions Ts.

[0014] 1, the vulcanizing mold 1 includes bead rings 2 that contact the outer surface of the bead portion Tb. The bead rings 2 are provided, for example, on both sides in the mold axial direction. The bead rings 2 include a lower bead ring 2A and an upper bead ring 2B that is disposed above the lower bead ring 2A.

[0015] In this embodiment, each bead ring 2A, 2B includes a bead molding surface 5 for molding the bead portion Tb. The bead molding surface 5 of the upper bead ring 2B has the same configuration as the bead molding surface 5 of the lower bead ring 2A. Therefore, in this specification, the configuration described for the bead molding surface 5 of the upper bead ring 2B also applies to the bead molding surface 5 of the lower bead ring 2A. Note that the configuration of the bead molding surface 5 of the lower bead ring 2A may be different from the configuration of the bead molding surface 5 of the upper bead ring 2B.

[0016] FIG. 3 is a partially enlarged view of the bead ring 2 (upper bead ring 2B) in FIG. 1. As shown in FIG. 3, at least a portion of the bead molding surface 5 includes a ventilation portion 6 formed of an air-permeable porous metal K1. As a result, during tire vulcanization, the ventilation portion 6 absorbs air between its surface and the outer surface of the bead portion Tb, thereby suppressing defects on the outer surface of the bead portion Tb. Furthermore, by providing the ventilation portion 6, the vulcanization mold 1 of the present invention does not require vent holes or vent lines, thereby preventing the formation of protrusions such as spews on the outer surface of the bead portion Tb. Therefore, the pneumatic tire T vulcanized using the vulcanization mold 1 of the present invention does not suffer from reduced adhesion to the standard rim R.

[0017] The "porous metal" is a metal material having a large number of pores (voids). The pores are preferably large enough to allow air to pass through but not allow unvulcanized rubber to pass through. The pores have an inner diameter of, for example, 1 to 10 μm. The porosity of the porous metal is preferably 10% to 90%. The porous metal can be obtained by, for example, sintering, etching, or dealloying of metal powder. Examples of metal powders that can be used include steel, aluminum alloys, stainless steel, and titanium alloys. The porous metal can be obtained by, for example, well-known methods.

[0018] FIG. 4 is a perspective cross-sectional view of a tire T after being vulcanized and molded using the vulcanization mold 1 of this embodiment. As shown in FIG. 4, the tire T has a first surface T1 formed with a pattern that is the inverse of the ventilation portion 6. The tire T also has a second surface T2 formed with a pattern that is the inverse of the main body 14, which will be described later. The first surface T1 has a surface roughness greater than that of the second surface T2. As described above, the ventilation portion 6 is provided in the bead ring 2. Therefore, the first surface T1 increases the frictional force with the rim R, improving adhesion between the tire T and the rim R and suppressing rim slippage and air leakage. The first surface T1 has a surface roughness Ra of 15 to 45 μm. The surface roughness is the ten-point average roughness Rz measured in accordance with JIS B 0601 (2001) and is measured using a known measuring instrument such as a stylus-type surface roughness measuring instrument. The first surface T1 has, for example, a different appearance (appearance) from the second surface T2.

[0019] As shown in Fig. 1, the vulcanizing mold 1 includes, for example, a tread mold 3 for forming the tread portion Ta and a side mold 4 for forming the sidewall portion Ts. In the vulcanizing mold 1 of this embodiment, the molding surface 1a is formed by the tread mold 3, the side mold 4, and the bead ring 2. The tread mold 3 and the side mold 4 have conventional structures.

[0020] FIG. 2 shows a cross section of a regular rim (hereinafter sometimes simply referred to as "rim") R on which a tire T is mounted. As shown in FIG. 2, the rim R includes a pair of rim flanges Rf and a pair of rim seats Rs. For example, each rim flange Rf is connected to each rim seat Rs and extends while smoothly curving outward in the tire radial direction and axial direction. The regular rim R means a rim defined in the standard on which the tire T is based. The regular rim is a "standard rim" in the RJATMA standard, a "design rim" in the TRA standard, and a "measuring rim" in the ETRTO standard.

[0021] The rim flange Rf has a height G in the tire radial direction from the rim diameter position K. The height G is the length in the tire radial direction from the rim diameter position K to the outer edge Re of the rim flange Rf in the tire radial direction. In this specification, the rim diameter position K is the height position in the tire radial direction that defines the rim diameter Da (see JATMA).

[0022] 3, the bead molding surface 5 includes a first position P1 corresponding to the rim diameter Da. The first position P1 is the position where the bead molding surface 5 intersects with a mold axial direction line Y that passes through the rim diameter position K (shown in FIG. 2) when the rim R is mounted on the tire T after vulcanization molding.

[0023] The ventilation portion 6 includes an outer edge 6e in the mold radial direction and an inner edge 6i in the mold radial direction. In this way, the ventilation portion 6 is formed to have a height in the mold radial direction. The ventilation portion 6 is continuous in the mold circumferential direction. However, the ventilation portion 6 may be interrupted in the mold circumferential direction.

[0024] The outer edge 6e is located, for example, outside the first position P1 in the mold radial direction. In this embodiment, the inner edge 6i is located inside the first position P1 in the mold radial direction. In this way, the ventilation portion 6 of this embodiment extends inward and outward in the mold radial direction, sandwiching the first position P1. This makes it possible to reliably absorb air near the first position P1, where air is relatively likely to stagnate, during vulcanization molding. Therefore, the tire T manufactured using the vulcanization mold 1 of this embodiment has even better adhesion to the rim R.

[0025] The height H of the outer edge 6e in the mold radial direction from the first position P1 is preferably 40% or more of the height G of the rim flange Rf, more preferably 45% or more, more preferably 80% or less, and even more preferably 75% or less. Because the height H is 40% or more of the height G, air between the surface of the ventilation portion 6 and the outer surface of the bead portion Tb can be smoothly absorbed, preventing defects on the outer surface of the bead portion Tb. Because the height H is 80% or less of the height G, the first surface T1 is covered by the rim flange Rf after vulcanization molding, and only the second surface T2 is visible, eliminating any sense of incongruity in the bead portion Tb of the tire T and maintaining its high appearance performance.

[0026] The thickness D of the porous metal K1 in the normal direction n of the bead molding surface 5 is preferably 1 mm or more, more preferably 5 mm or more. Such a thickness D allows the porous metal K1 to absorb more air. Furthermore, the thickness D of the porous metal K1 in the normal direction n of the bead molding surface 5 is preferably 50% or less, more preferably 40% or less, of the thickness W of the bead molding surface 5 in the normal direction n at the ventilation portion 6 of the bead ring 2. Such a thickness D can maintain high overall rigidity of the bead ring 2 and enable the unvulcanized tire T to be vulcanized with high precision. This further improves the adhesion between the bead portion Tb and the rim R. The thickness W is the shortest length of the bead ring 2 at the ventilation portion 6. Furthermore, the thickness D of the porous metal K1 is preferably 25 mm or less, more preferably 20 mm or less.

[0027] Fig. 5 is a partially exploded perspective view of the bead ring 2 of Fig. 3. As shown in Figs. 3 and 5, the bead ring 2 includes a main body 14 made of a non-porous metal K2. The non-porous metal K2 includes all metals except for the porous metal K1 that forms the ventilation portion 6. The non-porous metal K2 is, for example, a casting of a metal such as steel, aluminum alloy, stainless steel, or titanium alloy. In this embodiment, the main body 14 has the same structure as a conventional bead ring.

[0028] The main body 14 has a recess 15 formed on the bead molding surface 5 side. The recess 15 in this embodiment has a bottom surface 16 and a pair of wall surfaces 17 connecting the bottom surface 16 and the bead molding surface 5. The bottom surface 16 extends, for example, substantially parallel to the bead molding surface 5. The pair of wall surfaces 17 consists of a first wall surface 17a adjacent to the first position P1 (shown in FIG. 3) and a second wall surface 17b located radially outward of the first wall surface 17a.

[0029] An insert 19 is removably attached to the recess 15. The insert 19 is made of porous metal K1. In other words, the insert 19 constitutes the ventilation section 6. Such an insert 19 makes it easy to replace the ventilation section 6 that becomes clogged with rubber that flows in together with air during vulcanization molding, thereby extending the life of the bead ring 2 (main body 14).

[0030] The main body 14 is provided with exhaust holes 20 that communicate the bottom surface 16 with the outside of the mold. Such exhaust holes 20 can discharge the air absorbed by the porous metal K1 to the outside of the mold, further suppressing the formation of defects (bare) on the outer surface of the bead portion Tb and further improving the adhesion between the bead portion Tb and the rim R. The cross-sectional area A of the exhaust holes 20 is 0.1 mm 2 More than 0.25mm is desirable. 2 The above is even more desirable.

[0031] Thus, the ventilation portion 6 of this embodiment includes a first surface 6a that forms the bead molding surface 5 and a second surface 6b that faces (contacts) the bottom surface 16. The first surface 6a and the second surface 6b extend substantially parallel to each other.

[0032] It is desirable that the ventilation portion 6 does not have perforations on the surface (first surface) 6a that faces the bead molding surface 5. If the surface 6a does not have perforations, unvulcanized rubber will flow into the perforations during vulcanization molding, preventing the formation of protrusions such as spews. This maintains a high level of adhesion between the bead portion Tb and the rim R. In this specification, the perforations refer to holes formed with a drill or the like, with an inner diameter larger than that of a pore, for example, 1 mm or more, and extending from the first surface 6a toward the bottom surface 16.

[0033] Although a tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be modified and practiced in various aspects. [Example]

[0034] A pneumatic motorcycle tire of size 120 / 70R17 was prototyped using a vulcanization mold having the basic structure shown in Figure 1. This test tire was then tested for adhesion to the rim and for the appearance of the tire. The test method was as follows.

[0035] <Rim slippage resistance> Each test tire was mounted on the front wheel of the following test vehicle. The test vehicle was then run on a test course with a dry asphalt road surface, and the length of positional deviation between the tire and rim before and after the run was measured. The results were expressed by converting the positional deviation length into the following rating points. The larger the value, the better the rim slippage resistance and the better the adhesion between the bead portion and the rim. Test vehicle: 1000cc Position deviation length less than 1 mm: 5 points 1 to less than 4 mm: 4 points 4 to less than 11 mm: 3 points 11 to less than 15 mm: 2 points 15mm or more: 1 point

[0036] <Air leakage resistance> Each test tire was mounted on a standard rim and left at a constant temperature for six months. The amount of air pressure loss before and after leaving the tire was measured. The results were expressed as the following points: The higher the value, the better the air leakage resistance and the better the adhesion between the bead and the rim. Decrease of less than 6 kPa: 3 points 6 to less than 10 kPa: 2 points 10kPa or more: 1 point

[0037] <Bear resistance> The number of bare spots that occurred in the bead portion of each test tire was counted. The results were expressed by converting the number of bare spots (concave scratches) into the following score. The higher the score, the better the adhesion between the bead portion and the rim. Number of bears: 0: 3 points 1~3 pieces: 2 points 4 or more: 1 point

[0038] <Appearance performance> Each test tire was mounted on a regular rim, and it was confirmed whether the uneven pattern shown in Figure 4 was visible. The result was indicated as "present" if the first surface was visible, and "absent" if the first surface was not visible. The test results are shown in Table 1.

[0039] [Table 1]

[0040] As shown in Table 1, it can be seen that the vulcanizing mold of this embodiment improves the adhesion between the bead portion and the rim compared to the vulcanizing mold of the comparative example.

[0041] [Note] The present invention includes the following aspects.

[0042] [Invention 1] A tire vulcanization mold for vulcanizing and molding a pneumatic tire having a bead portion, a bead ring having a bead molding surface for contacting an outer surface of the bead portion to mold the bead portion, At least a portion of the bead molding surface includes a ventilation portion formed of a porous metal having air permeability. Tire vulcanization mold. [Invention 2] The tire vulcanizing mold according to the first aspect of the present invention, wherein the ventilation portion is continuous in an annular shape in the circumferential direction of the mold. [Invention 3] The pneumatic tire is mounted on a standard rim having a rim flange, The rim flange has a height G in the tire radial direction from the rim diameter position, the vent portion has an outer edge in the radial direction of the mold, the bead molding surface includes a first position corresponding to the rim diameter, 3. The tire vulcanizing mold according to claim 1 or 2, wherein a height H of the outer edge in the mold radial direction from the first position is 80% or less of the height G of the rim flange. [Invention 4] A tire vulcanizing mold according to Invention 3, wherein a height H of the outer edge in the mold radial direction from the first position is 40% or more of the height G of the rim flange. [Invention 5] the vent portion has an inner edge in the radial direction of the mold, 5. The tire vulcanization mold according to invention 3 or 4, wherein the inner edge is located more inward in the mold radial direction than the first position. [Invention 6] 6. A tire vulcanizing mold according to any one of Inventions 1 to 5, wherein the thickness of the porous metal in the normal direction to the bead molding surface is 1 mm or more. [Invention 7] A tire vulcanizing mold according to any one of the first to sixth aspects of the present invention, wherein the thickness of the porous metal in the normal direction to the bead molding surface is 50% or less of the thickness of the bead ring at the ventilation portion in the normal direction to the bead molding surface. [Invention 8] the bead ring includes a body made of a non-porous metal; The main body has a recess formed on the bead forming surface side, An insert is removably attached to the recess, 8. A tire vulcanizing mold according to any one of Inventions 1 to 7, wherein the insert is made of the porous metal. [Invention 9] The recess has a bottom surface, A tire vulcanizing mold according to invention 8, wherein the main body is provided with an exhaust hole that connects the bottom surface with the outside of the mold. [Invention 10] 10. The tire vulcanizing mold according to any one of Inventions 1 to 9, wherein the ventilation part does not have a perforated part on the surface that faces the bead molding surface. [Invention 11] 1. A method for manufacturing a pneumatic tire, comprising: The method includes a step of vulcanizing a pneumatic tire using a tire vulcanization mold according to any one of the present inventions 1 to 10. A method for manufacturing a pneumatic tire. [Explanation of symbols]

[0043] 1 Tire curing mold 2 bead rings 5 Bead forming surface 6 Ventilation section T Pneumatic tire Tb bead part

Claims

1. A tire vulcanization mold for vulcanizing and molding a pneumatic tire having a bead portion, a bead ring having a bead molding surface for contacting an outer surface of the bead portion to mold the bead portion, At least a portion of the bead molding surface includes a ventilation portion formed of a porous metal having air permeability. Tire vulcanization mold.

2. The tire vulcanization mold according to claim 1 , wherein the ventilation portion is continuous in an annular shape in the circumferential direction of the mold.

3. The pneumatic tire is mounted on a standard rim having a rim flange, The rim flange has a height G in the tire radial direction from the rim diameter position, the vent portion has an outer edge in the radial direction of the mold, the bead molding surface includes a first position corresponding to the rim diameter, The tire vulcanization mold according to claim 1 , wherein a height H of the outer edge in the mold radial direction from the first position is 80% or less of the height G of the rim flange.

4. The tire vulcanization mold according to claim 3 , wherein a height H of the outer edge in the mold radial direction from the first position is 40% or more of the height G of the rim flange.

5. the vent portion has an inner edge in the radial direction of the mold, The tire vulcanization mold according to claim 3 , wherein the inner edge is located radially inward of the first position.

6. 6. The tire vulcanization mold according to claim 1, wherein the thickness of said porous metal in the normal direction of said bead molding surface is 1 mm or more.

7. 6. The tire vulcanization mold according to claim 1, wherein a thickness of the porous metal in a normal direction to the bead molding surface is 50% or less of a thickness of the bead ring at the ventilation portion in the normal direction to the bead molding surface.

8. the bead ring includes a body made of a non-porous metal; The main body has a recess formed on the bead forming surface side, An insert is removably attached to the recess, The tire vulcanizing mold according to claim 1 , wherein the insert is made of the porous metal.

9. The recess has a bottom surface, The tire vulcanizing mold according to claim 8, wherein the main body is provided with an exhaust hole that connects the bottom surface to the outside of the mold.

10. The tire vulcanizing mold according to claim 1 , wherein the ventilation portion does not have a perforated portion on a surface facing the bead molding surface.

11. 1. A method for manufacturing a pneumatic tire, comprising: A step of vulcanizing a pneumatic tire using the tire vulcanizing mold according to any one of claims 1 to 5, A method for manufacturing a pneumatic tire.

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