Tire vulcanization mold

Abstract

To improve gas discharge performance from a tire vulcanizing mold.SOLUTION: A tire vulcanization mold 10 includes a molding surface 22, a recess 26, a vent hole 28, and a spring vent 50. The molding surface 22 molds the outer shape of the tire. The recessed portion 26 is formed in the molding surface 22. The recess 26 has a bottom. The vent hole 28 is formed in a part of the bottom side 26a of the recess 26. The spring vent 50 is attached to the vent hole 28. The spring vent 50 includes a cylindrical housing 51 and a stem 55. A through hole 52 is formed in the housing 51. The stem 55 is inserted into the through hole 52 of the housing 51. The depth h of the concave portion 26 is 1. 0mm or less. The distances r between the edge 52a of the through hole 52 and the edge 26a1 of the bottom 26a of the recess 26 are less than or equal to the diameters d of the through holes.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a tire vulcanization mold. [Background Art]

[0002] Japanese Unexamined Patent Publication No. 2017-113895 discloses a tire vulcanization mold comprising a molding surface, a recessed groove, a plug attachment hole, and a vent plug. The molding surface is a surface for molding the tire surface. The recessed groove is recessed relative to the molding surface. The plug attachment hole is provided in the recessed groove. The plug attachment hole communicates between the inside of the mold and the outside of the mold. The vent plug is fitted into the plug attachment hole. The vent plug includes a housing and a stem. The housing is cylindrical and has, on the inner diameter side thereof, a vent hole communicating from the inside of the recessed groove to the outside of the mold. The stem is inserted into the inner diameter side of the housing and opens and closes the vent hole. The inner end face of the housing on the inner side of the mold is located closer to the outside of the mold than the molding surface is. [Prior Art Literature] [Patent Literature]

[0003] [Patent Literature 1] Japanese Unexamined Patent Publication No. 2017-113895 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] When vulcanizing a tire using a tire provided with a spring vent, the present inventor desires to improve the gas discharge performance from the tire vulcanization mold. [Means for Solving the Problem]

[0005] The tire vulcanizing mold disclosed herein comprises a molding surface, a recess, a vent hole, and a spring vent. The molding surface is a surface for molding the outer shape of the tire. The recess is formed on the molding surface. The recess has a bottom. The vent hole is formed in part of the bottom of the recess. The spring vent is fitted into the vent hole. The spring vent comprises a cylindrical housing and a stem. The housing has a through hole formed therein. The stem is inserted through the through hole in the housing. The depth of the recess is 1.0 mm or less. The distance from the edge of the through hole to the edge of the bottom of the recess is less than or equal to the diameter of the through hole. [Effects of the Invention]

[0006] With this type of tire vulcanization mold, the gas discharge performance from the tire vulcanization mold is improved during tire vulcanization. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram of a tire vulcanizing machine 1. [Figure 2] Figure 2 is a cross-sectional view of the side mold 20. [Figure 3] Figure 3 is a cross-sectional view of the side mold 20. [Figure 4] Figure 4 is a plan view of the side mold 20. [Figure 5] Figure 5 is a plan view of the side mold 20A according to another embodiment. [Figure 6] Figure 6 is a plan view of the side mold 20B according to another embodiment. [Figure 7] Figure 7 is a plan view of the side mold 20C according to another embodiment. [Modes for carrying out the invention]

[0008] One embodiment of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following embodiments. Each drawing is schematic and does not necessarily reflect the actual object. Furthermore, each drawing is merely an example and does not limit the present invention unless specifically mentioned. Also, components and parts that perform the same function are appropriately denoted by the same reference numerals, and redundant explanations are omitted.

[0009] <Tire vulcanizing machine 1> Figure 1 is a schematic diagram of a tire vulcanizing machine 1. Figure 1 schematically shows a cross-section of the tire vulcanizing machine 1 during the vulcanization of the low cover 110. In Figure 1, the hatching of the low cover 110 and bladder 68 is omitted.

[0010] As shown in Figure 1, the tire vulcanizing machine 1 comprises a tire vulcanizing mold 10 and a bladder centering mechanism 60. The bladder centering mechanism 60 includes a bladder 68 located at the center of the tire vulcanizing machine 1. In the tire vulcanizing machine 1, a low cover 110 supported by the bladder 68 is pressed against the tire vulcanizing mold 10 and vulcanized to form the tire.

[0011] <Low Cover 110> The low cover 110 is an unvulcanized tire before vulcanization molding, and is also called a green tire. Although not shown in the diagram, the low cover 110 is a cylindrical member in which unvulcanized sidewall rubber and tread rubber are bonded to a base material such as bead wire, carcass, or belt. The low cover 110 has a tread portion 112 and a sidewall portion 114. The tread portion 112 is the part of the tire that comes into contact with the road surface after vulcanization. The sidewall portion 114 is the part of the tire that comes into contact with the side surface after vulcanization.

[0012] <Tire vulcanization mold 10> The tire vulcanization mold 10 comprises a plurality of molds 20, 30, and 40. The plurality of molds 20, 30, and 40 are arranged in a toroidal manner so as to surround the bladder 68. The tire vulcanization mold 10 comprises a plurality of molds 20, 30, and 40 arranged around the bladder 68. The material of the tire vulcanization mold 10 may be a metal such as aluminum or an aluminum alloy. The material of the tire vulcanization mold 10 is not particularly limited.

[0013] During tire vulcanization, the molds 20, 30, and 40 are heated by heaters (not shown). The molds 20, 30, and 40 have molding surfaces 22, 32, and 42 that form the outer shape of the tire. During tire vulcanization, the molding surfaces 22, 32, and 42 of the molds 20, 30, and 40 are continuous, forming a mold cavity 10a. The low cover 110 is heated and pressurized while being pressed against the molding surfaces 22, 32, and 42 in the mold cavity 10a, and is vulcanized.

[0014] The molding surfaces 22, 32, and 42 of molds 20, 30, and 40 are provided with irregularities that match the desired external shape of the tire. For example, the molding surfaces 22 and 32 of molds 20 and 30 may have irregularities formed to display tire information on the tire's sidewall. The molding surface 42 of mold 40 has irregularities formed to form a tread pattern, wear indicator, etc., on the tire's tread according to the desired function.

[0015] Molds 20 and 30 are also called side molds. The sidewall portion 114 of the low cover 110 is pressed against the molding surfaces 22 and 32 of molds 20 and 30. This vulcanizes the sidewall portion of the tire. Mold 40 is also called a tread mold. The tread portion 112 of the low cover 110 is pressed against the molding surface 42 of mold 40. This vulcanizes the tread portion of the tire.

[0016] The mold 20 is annular. The mold 20 is provided below the tire vulcanization mold 10. The mold 20 is attached to the mold base 12. The mold base 12 is attached to, for example, a press table (not shown). The mold 20 is provided with a bead ring 24 that holds the bead portion of the raw cover 110.

[0017] Similar to the mold 20, the mold 30 is annular. The mold 30 is provided above the tire vulcanization mold 10. The mold 30 faces the mold 20 in the vertical direction. The mold 30 is attached to the mold base 14. In this embodiment, the mold base 14 is attached to a press machine and configured to be movable up and down. The mold 30 is provided with a bead ring 34 that holds the bead portion of the raw cover 110. The molds 20 and 30 may be composed of a plurality of mold members.

[0018] The mold 40 is a mold member for molding the tread portion of a tire. The molding surface 42 of the mold 40 is a surface for molding the tread portion of the tire. The molding surface 42 is provided with protrusions 42a for forming recesses such as grooves, sipes and slits on the tread surface of the tire. The tire vulcanization mold 10 is provided with a plurality of molds 40 divided along the circumferential direction. The plurality of molds 40 are arranged at predetermined intervals in the circumferential direction.

[0019] The plurality of molds 40 are driven inward and outward in the radial direction by the mold opening / closing mechanism 16. The mold opening / closing mechanism 16 includes a slider 16a to which the mold 40 is attached, and a pusher 16b driven in the vertical direction. An inclined surface that widens outward as it goes downward is formed on the outer side surface of the slider 16a. The pusher 16b is formed with an inclined surface that widens outward as it goes downward so as to face the inclined surface of the slider 16a. The contact between the inclined surface of the pusher 16b and the inclined surface of the slider 16a causes the slider 16a to move inward and outward. Thereby, the mold 40 is opened and closed in the radial direction.

[0020] Although not shown in the diagram, before the tire is vulcanized, the molds 40 are positioned radially outward, separated from adjacent molds 40. At this time, mold 30 is held above the low cover 110. During tire vulcanization, the molds 40 move radially inward. The multiple molds 40 are continuous in the circumferential direction. Simultaneously, mold 30, which was held above the low cover 110, moves downward. As a result, the tire vulcanization mold 10 is closed, and molds 20, 30, and 40 become continuous. During tire vulcanization, with the tire vulcanization mold 10 closed, the low cover 110, supported by the bladder 68, is pressed against the molding surfaces 22, 32, and 42 of molds 20, 30, and 40.

[0021] <Bladder center mechanism 60> The bladder center mechanism 60 comprises a center post 62, clamp rings 64 and 66, and a bladder 68.

[0022] The bladder 68 is located in the mold space 10a. The bladder 68 is a component that is pressed against the inner surface of the low cover 110. The bladder 68 is a cylindrical elastic body made of rubber. As the bladder 68 expands, the low cover 110 is pressed against the molding surfaces 22, 32, and 42 of the molds 20, 30, and 40, and the outer shape of the tire is formed. The bladder 68 is located in the center between the vertically opposing molds 20 and 30. The bladder 68 is held with the center post 62 as its central axis.

[0023] The center post 62 is an axial member that extends along the direction in which the molds 20 and 30 face each other. The center post 62 penetrates the central part of the mold 20 that forms the lower sidewall portion 114. A pair of opposing clamp rings 64 and 66 are attached to the center post 62.

[0024] The clamp ring 66 is a disc-shaped member attached to the upper end of the center post 62. The clamp ring 66 is a member that grips the upper end of the bladder 68. Although not shown in the illustration, the clamp ring 66 may be, for example, a member that can be divided into upper and lower parts, and may have a structure that holds the peripheral edge on the upper end side of the bladder 68 by clamping it. The clamp ring 64 is a disc-shaped member attached to the upper surface of the bead ring 24. The clamp ring 64 may be attached to the center post 62. The clamp ring 64 is a member that grips the lower end of the bladder 68. The lower end of the bladder 68 may be held by being sandwiched between the clamp ring 64 and the bead ring 24.

[0025] A fluid (such as steam or nitrogen) is supplied from a fluid supply device (not shown) to the space surrounded by the clamp rings 64 and 66 and the bladder 68. Heat and pressure are applied to the low cover 110 from the inside in the mold space 10a of the tire vulcanization mold 10. As a result, the low cover 110 is heated while being pressed against the tire vulcanization mold 10, and the tire is vulcanized.

[0026] The configuration of the tire vulcanization mold 10 used in the tire vulcanization machine 1 will be explained below, using the side mold 20 as an example. Figure 2 is a cross-sectional view of the side mold 20.

[0027] The configuration described below is not limited to being provided on the side mold 20. For example, it may be provided on the side mold 30, on the bead rings 24 and 34 connected to the side molds 20 and 30, or on the tread mold 40.

[0028] <Side Mold 20> The side mold 20 (tire vulcanization mold 10) includes a molding surface 22, a recess 26, a vent hole 28, and a spring vent 50, as shown in Figure 2.

[0029] <Molding surface 22> The molding surface 22 is the surface that forms the outer shape of the tire. The molding surface 22 is the surface that forms the sidewall portion 114 of the low cover 110 during tire vulcanization (see Figure 1). The molding surface 22 is provided with a configuration for discharging gas generated between the low cover 110 and the side mold 20 during vulcanization. The molding surface 22 has vent holes 28 and vent lines 23 (see Figure 4) formed therein. The vent holes 28 are formed in recesses 26 of the molding surface 22.

[0030] <Recess 26> The recess 26 is formed in the molding surface 22. The recess 26 is recessed relative to the molding surface 22. Therefore, during tire vulcanization, the low cover 110 (see Figure 1) can flow into the recess 26 after being pressed against the molding surface 22 by the bladder 68 (see Figure 1). Depending on the dimensions of the recess 26, the portion that enters the recess 26 may protrude from the surrounding area in the sidewall portion of the tire after vulcanization. The planar shape of the recess 26 is not particularly limited. For example, when viewed perpendicular to the molding surface 22, the planar shape of the recess 26 may be circular, elliptical, or polygonal (for example, quadrilateral). In this embodiment, the planar shape of the recess 26 is circular (see Figure 4).

[0031] The recess 26 comprises a bottom portion 26a and a side circumferential portion 26b. The side circumferential portion 26b is connected to the bottom portion 26a and the molding surface 22. In the embodiment shown in Figure 2, the side circumferential portion 26b rises substantially vertically from the edge 26a1 of the bottom portion 26a. The side circumferential portion 26b may be inclined with respect to the bottom portion 26a. The bottom portion 26a is lower than the molding surface 22 of the recess 26. In this embodiment, the bottom portion 26a is circular in shape. The bottom portion 26a is substantially parallel to the molding surface 22. A vent hole 28 is formed in the center of the bottom portion 26a.

[0032] <Bent Hall 28> The vent hole 28 is formed in a part of the bottom of the recess 26. The vent hole 28 is a hole for releasing gas generated between the tire vulcanization mold 10 and the low cover 110 (see Figure 1) during vulcanization. Although not shown in detail, the vent hole 28 penetrates the side mold 20 and connects to the outside of the tire vulcanization mold 10. A spring vent 50 is fitted into the vent hole 28.

[0033] <Spring Bent 50> The spring vent 50 comprises a cylindrical housing 51 and a stem 55. An example of a spring vent 50 applicable to the tire vulcanization mold 10 disclosed herein is described below. However, the configuration of the spring vent 50 is not limited to that described below.

[0034] <Housing 51> The housing 51 has a shape that corresponds to the inner circumferential surface 28a of the vent hole 28. In this embodiment, the housing 51 is substantially cylindrical. The housing 51 comprises a front portion 51e and a rear portion 51f, which has a smaller diameter than the front portion 51e. When the housing 51 is attached to the side mold 20, the front portion 51e is positioned on the side facing the molding surface 22, and the rear portion 51f is positioned on the side farther from the molding surface 22. The outer diameter of the front portion 51e of the housing 51 attached to the side mold 20 is substantially the same as the inner diameter of the vent hole 28. Before being attached to the side mold 20, the outer diameter of the front portion 51e of the housing 51 may be formed to be slightly larger than the inner diameter of the vent hole 28. Therefore, the housing 51 can be press-fitted into the vent hole 28. As a result, the outer circumferential surface of the front portion 51e of the housing 51 can be held against the inner circumferential surface 28a of the vent hole 28. In the embodiment shown in Figure 2, the outer diameter of the rear portion 51f of the housing 51 is smaller than the inner diameter of the vent hole 28. When installing the housing 51 into the vent hole 28, the housing 51 is press-fitted into the vent hole 28 with the rear portion 51f inserted through it. This improves the workability when installing the spring vent 50. A through hole 52 is formed in the housing 51.

[0035] The through-hole 52 penetrates the housing 51 axially (in the direction in which the vent hole 28 extends). The cross-sectional shape of the through-hole 52 is approximately circular. The housing 51 comprises an opening 51a, a housing portion 51b, a reduced diameter portion 51c, and an end portion 51d. The through-hole 52 penetrates the opening 51a, the housing portion 51b, the reduced diameter portion 51c, and the end portion 51d. The opening 51a, the housing portion 51b, the reduced diameter portion 51c, and the end portion 51d are arranged in order from the side facing the molded surface 22, along the direction in which the vent hole 28 extends when the housing 51 is fitted into the vent hole 28.

[0036] The opening 51a is provided at the end facing the molding surface 22. The opening 51a tapers so that its diameter increases towards the molding surface 22. The housing portion 51b opens with approximately the same diameter from the opening 51a toward the reduced diameter portion 51c. The housing portion 51b houses the spring 53, which will be described later. The reduced diameter portion 51c is a portion with a smaller inner diameter than the housing portion 51b and the end portion 51d. The end portion 51d has a larger diameter than the reduced diameter portion 51c and is an open portion at the end opposite to the molding surface 22. The stem 55 is inserted through the through hole 52 of the housing 51.

[0037] <Stem 55> The stem 55 is inserted through the through hole 52 of the housing 51. The stem 55 comprises a head portion 55a, a shaft portion 55b, and an end portion 55c. The head portion 55a, the shaft portion 55b, and the end portion 55c are arranged in order from the side facing the molding surface 22 along the direction in which the vent hole 28 extends. The head portion 55a is provided at the end facing the molding surface 22.

[0038] The head portion 55a is tapered so that its diameter increases towards the molding surface 22. The head portion 55a is longer than the opening 51a. The shaft portion 55b is approximately cylindrical in shape, extending from the head portion 55a to the end portion 55c with approximately the same diameter. The shaft portion 55b has an outer diameter smaller than the inner diameter of the reduced diameter portion 51c. The shaft portion 55b is inserted through the housing portion 51b and the reduced diameter portion 51c. The end portion 55c is housed in the end portion 51d of the housing 51. The end portion 55c has a larger diameter than the shaft portion 55b. Also, the end portion 55c has a larger diameter than the shaft portion 55b. As a result, the end portion 55c is located outside the reduced diameter portion 51c (on the opposite side from the molding surface 22). A spring (coil spring) 53 is interposed between the housing 51 and the stem 55.

[0039] <Spring 53> The spring 53 is housed in the housing portion 51b of the housing 51 with the shaft portion 55b of the stem 55 inserted through it. The spring 53 is housed in the housing 51 in a compressed state shorter than its natural length. One end of the spring 53 is in contact with the head portion 55a of the stem 55. The other end of the spring 53 is in contact with the step 51c1 of the housing 51 between the housing portion 51b and the reduced diameter portion 51c. The spring 53 biases the head portion 55a of the stem 55 toward the mold internal space 10a. When the spring 53 biases the head portion 55a, the end portion 55c of the stem 55 is in contact with the step 51c2 of the housing 51 between the reduced diameter portion 51c and the end portion 51d. As a result, the head portion 55a does not protrude from the molding surface 22 by a predetermined length.

[0040] Before the tire is vulcanized, the top 55a may protrude from the molded surface 22. At this time, a gap is formed between the opening 51a of the housing 51 and the top 55a of the stem 55. This gap connects the mold cavity 10a and the vent hole 28. During the vulcanization of the tire, the gas in the mold cavity 10a (gas generated between the low cover 110 and the tire vulcanization mold 10) flows through the gap between the opening 51a of the housing 51 and the top 55a of the stem 55 to the vent hole 28. The gas from inside the mold cavity 10a passes through the vent hole 28 and is discharged outside the tire vulcanization mold 10.

[0041] When the low cover 110 is vulcanized and the rubber of the low cover 110 (in this embodiment, the rubber of the sidewall portion 114) is pressed against the molded surface 22, the rubber is also pressed against the head 55a of the stem 55 of the spring vent 50. At this time, if the head 55a of the stem 55 is pressed with a force stronger than the biasing force of the spring 53, the head 55a of the stem 55 is pushed toward the housing 51. When the head 55a of the stem 55 comes into contact with the opening 51a of the housing 51, the gap between the head 55a of the stem 55 and the opening 51a of the housing 51 is closed.

[0042] Incidentally, the inventors have found that when a tire is vulcanized using a tire vulcanization mold equipped with a spring vent, there is a concern that rubber may enter the gap between the spring vent housing and the stem. If rubber enters the gap between the spring vent housing and the stem, the gas generated between the tire vulcanization mold and the low cover will have difficulty escaping from the spring vent. If the gas generated between the tire vulcanization mold and the low cover does not escape to the outside of the tire vulcanization mold, there is a concern that defects (such as voids) due to vulcanization defects will occur on the surface of the tire after vulcanization. Furthermore, the above-mentioned vulcanization defects will be more likely to occur during subsequent vulcanization.

[0043] In this embodiment, the vent hole 28 into which the spring vent 50 is attached is provided at the bottom of the recess 26.

[0044] Here, the depth h of the recess 26 is set to 1.0 mm or less. The depth h of the recess 26 may be set to 0.7 mm or less. The depth h of the recess 26 may be set to 0.1 mm or more, or to 0.25 mm or more. In this embodiment, the depth h of the recess 26 is set to 0.5 mm. Note that "depth h of the recess" is the distance between the plane perpendicular to the plane along the molding surface and the bottom of the recess. In other words, "depth h" is the distance from the opening of the recess along the molding surface to the bottom, and is the depth perpendicular to the molding surface. If the bottom is inclined with respect to the molding surface, "depth h" refers to the depth of the deepest part of that depth.

[0045] Furthermore, the distance r between the edge 52a of the through hole 52 of the housing 51 and the edge 26a1 of the bottom 26a of the recess 26 is set to be less than or equal to the diameter d of the through hole 52. The distance r may be set to 0.5 times or less the diameter d, or to 0.3 times or less. In this embodiment, the distance r is set to 0.25 times the diameter d. The distance r may be set to 0.1 times or more the diameter d. Although not particularly limited, the diameter d of the through hole 52 is 1 mm or more, or 1.5 mm or more. The diameter d of the through hole 52 is 10 mm or less, or 5 mm or less.

[0046] The "distance r between the edge of the through-hole and the edge of the bottom of the recess" (hereinafter also simply referred to as "distance r") is the distance from the edge of the through-hole to the edge of the bottom of the housing, along the outer diameter direction. If the bottom of the recess is inclined with respect to the molded surface, "distance r" refers to the distance between the deepest part of the bottom of the recess and the edge of the through-hole closest to that part. If the distance from the edge of the through-hole to the edge of the bottom of the housing is not constant (for example, if the shape of the bottom of the recess is not circular), "distance r" refers to the minimum distance among these. For example, if the through-hole of the housing is circular and the bottom of the recess is square, "distance r" is the distance from the edge of the circular through-hole to the closest point on the outer edge of the square bottom.

[0047] In the embodiment described above, the tire vulcanization mold 10 (in this embodiment, the side mold 20) comprises a molding surface 22, a recess 26, a vent hole 28, and a spring vent 50. The molding surface 22 forms the outer shape of the tire. The recess 26 is formed in the molding surface 22. The recess 26 has a bottom. The vent hole 28 is formed in a part of the bottom 26a of the recess 26. The spring vent 50 is fitted into the vent hole 28. The spring vent 50 comprises a cylindrical housing 51 and a stem 55. A through hole 52 is formed in the housing 51. The stem 55 is inserted through the through hole 52 of the housing 51. The depth h of the recess 26 is 1.0 mm or less. The distance r between the edge 52a of the through hole 52 and the edge 26a1 of the bottom 26a of the recess 26 is less than or equal to the diameter d of the through hole.

[0048] Here, a vent hole 28 into which the spring vent 50 is installed is formed in a part of the bottom 26a of the recess 26. This allows the rubber of the low cover 110 to contact the molded surface 22 before contacting the stem 55 of the spring vent 50 during vulcanization. Furthermore, the rubber of the low cover 110 is more likely to contact the stem 55 from the axial direction of the stem 55. This makes it easier to close the gap between the housing 51 and the stem 55 without pinching the rubber. For example, compared to the case where the spring vent is provided on the molded surface, it is less likely for rubber to flow between the housing 51 and the stem 55 from the radially outer side of the stem 55. As a result, problems caused by gas not being able to escape from the tire vulcanization mold 10 are less likely to occur. In addition, the gas generated during vulcanization flows from between the low cover 110 and the molded surface 22 into the recess 26 and is then easily discharged from the spring vent 50. In other words, before the low cover 110 hits the stem 55 and the gap in the spring vent 50 is sealed, the gas generated during vulcanization tends to collect in the recess 26. As a result, the gas generated during vulcanization is less likely to remain inside the tire vulcanization mold 10.

[0049] By having a depth h of 1.0 mm or less in the recess 26, the gas discharge performance of the tire vulcanization mold 10 is maintained while reducing the aforementioned vulcanization defects. In addition, after vulcanization, it is less likely that rubber will enter the recess 26, resulting in an appearance defect and increased air resistance. The distance r between the edge 52a of the through hole 52 and the edge 26a1 of the bottom 26a of the recess 26 is less than or equal to the diameter d of the through hole. This reduces the amount of rubber that can flow between the housing 51 and the stem 55 from the radially outer side of the stem 55. As a result, defects caused by rubber getting caught between the housing 51 and the stem 55 are reduced.

[0050] In the embodiment described above, the planar shape of the recess 26 is circular. This allows gas to flow uniformly into the space enclosed by the recess 26 in the circumferential direction of the recess 26. As a result, gas flows more uniformly into the spring vent 50, which can improve the gas discharge performance from the tire vulcanization mold 10. In addition, the timing of rubber flow into the recess 26 is more easily synchronized in the circumferential direction of the recess 26. As a result, the problem of rubber getting caught between the housing 51 and the stem 55 is more easily reduced.

[0051] In the embodiment described above, the vent hole 28 is formed in the center of the bottom 26a of the recess 26. With this configuration, the gas flowing into the recess 26 flows into the spring vent 50 in a balanced manner, which can improve the gas discharge performance from the vent hole 28.

[0052] In the embodiment described above, the recess 26 is substantially parallel to the molding surface 22. However, the embodiment is not limited to this configuration, and the recess may be inclined with respect to the molding surface.

[0053] Figure 3 is a cross-sectional view of the side mold 20. Figure 3 shows a cross-section of the side mold 20 near the boundary with other molds (e.g., tread mold 40, bead ring 24). Figure 3 shows a cross-section of the side mold 20 near the boundary with the bead ring 24.

[0054] As shown in Figure 3, the side mold 20 is provided with a recess 126. The recess 126 is located near the interface surface 20a of the side mold 20. The interface surface 20a is the surface that forms the boundary between the side mold 20 and other molds (e.g., tread mold, bead ring, etc.), and is also called the splitting position of the side mold 20. The angle between the interface surface 20a and the molding surface 22 is less than 90 degrees. Although not particularly limited, the angle between the interface surface 20a and the molding surface 22 may be between 45 degrees and less than 90 degrees (for example, between 60 degrees and 80 degrees).

[0055] The bottom 126a of the recess 126 is inclined with respect to the molding surface 22. The bottom 126a is connected to the molding surface 22 at the portion 122 furthest from the molding surface 22. Except for the portion 122 furthest from the molding surface 22, the bottom 126a is connected to the side circumference 126b. The side circumference 126b is connected to the molding surface 22 and is approximately perpendicular to the molding surface 22. When the bottom and the molding surface are connected, the angle of the bottom with respect to the molding surface is the angle with the connected portion (in this embodiment, the portion 122 furthest from the molding surface) as the apex. When the bottom and the molding surface are not connected, the angle of the bottom with respect to the molding surface is the angle with the bottom extended in the surface direction and the portion overlapping with the molding surface as the apex.

[0056] By inclining the bottom 126a of the recess 126 with respect to the molding surface 22, it is easier to adjust the direction in which the vent holes 28 extend from the bottom 126a. Although not particularly limited, by adjusting the angle of the bottom 126a with respect to the molding surface 22, the direction in which the vent holes 28 extend can be adjusted so that they do not reach the interface surface 20a. For example, by bringing the angle between the interface surface 20a and the surface extended from the bottom 126a in the surface direction closer to 90 degrees, the vent holes 28 may be less likely to approach the interface surface 20a.

[0057] While not particularly limited, the angle at which the bottom 126a is inclined with respect to the molding surface 22 can be set to approximately 45 degrees or less. By setting the angle at which the bottom 126a is inclined with respect to the molding surface 22 to approximately 45 degrees or less, the resistance to gas passing through the vent hole 28 is less affected.

[0058] Figure 4 is a plan view of the side mold 20. The recesses 26 (see Figure 2) and 126 (see Figure 3) described above may be connected to the vent line 23. The following describes the case where the recess 26 is connected to the vent line 23. The same configuration can be used when the recess 126 is connected to the vent line 23, so a detailed explanation will be omitted.

[0059] <Ventline 23> The vent line 23 is a groove formed in the molded surface 22, as shown in Figure 4. The vent line 23 is formed along the circumferential direction of the side mold 20 (the circumferential direction of the tire). The cross-sectional shape of the vent line 23 is not particularly limited. When viewed along the direction in which the vent line 23 extends, the cross-sectional shape of the vent line 23 may be, for example, substantially rectangular or substantially semicircular. The vent line 23 may be formed on each of the multiple side molds 20 so as to be continuous in an annular shape when multiple side molds 20 are arranged in a row. This allows the gas generated between the low cover 110 and the side mold 20 during tire vulcanization to flow through the vent line 23. This prevents the gas from accumulating locally between the low cover 110 and the side mold 20. The number of vent lines is not particularly limited; there may be one or two or more. Vent lines are not necessarily required.

[0060] In this embodiment, at least two vent lines 23a and 23b can be formed on the molded surface 22. When viewed from the axis center of the tire vulcanizing machine 1 (see Figure 1) (axis center of the center post 62), vent line 23a is located radially inward from vent line 23b. The molded surface 22 is provided with a recess 26 that connects to the two vent lines 23a and 23b. The recess 26 is located between the two vent lines 23a and 23b.

[0061] With this configuration, the gas that flows through the two vent lines 23a and 23b during vulcanization flows into the recess 26 from different directions. The gas can then be discharged from the spring vent 50. Because the gas that flows through the two vent lines 23a and 23b flows into the recess 26 from different directions, the gas that flows through both vent lines 23a and 23b is easily discharged from the spring vent 50 in a balanced manner. As a result, the efficiency of gas discharge to the outside of the tire vulcanization mold 10 can be improved. In addition, it is not necessary to provide a spring vent 50 for each vent line 23. Therefore, the number of spring vents 50 can be reduced. Furthermore, in the vulcanized tire, the portion that has entered the recess 26 is not formed outside the two vent lines 23a and 23b. As a result, the appearance quality of the vulcanized tire can be improved.

[0062] The depth of the vent line 23 can be set to be less than or equal to the depth of the recess 26. This makes it difficult for rubber to flow from the vent line 23 side (radially outward of the stem 55) between the housing 51 and the stem 55. In this embodiment, the depth of the vent line 23 is the same as the depth of the recess 26. This makes it difficult for rubber to flow between the housing 51 and the stem 55, and also reduces the height of the portion that protrudes from the surrounding area (rubber that has entered the recess 26) in the vulcanized tire. Note that the depth of the vent line 23 is not particularly limited.

[0063] In this embodiment, the circumferential portion 26b of the recess 26 is connected to the two vent lines 23a and 23b. As a result, the recess 26 is directly connected to the two vent lines 23a and 23b without the need for grooves or other inclined structures relative to the vent lines 23. In this embodiment, the planar shape of the recess 26 is approximately circular. The circumferential portion 26b is approximately semi-circular in plan view, except for the portion connected to the two vent lines 23a and 23b. With this configuration, the gas generated during vulcanization can easily flow quickly into the spring vent 50 through the vent lines 23a and 23b. As a result, the efficiency of gas discharge to the outside of the tire vulcanization mold 10 can be improved.

[0064] The connection between the recess 26 and the vent line 23 is not limited to the embodiments described above. Figure 5 is a plan view of a side mold 20A according to another embodiment. As shown in Figure 5, the side mold 20A has a substantially square recess 26A in plan view. A vent hole 28 is formed in the recess 26A. A spring vent 50 is fitted into the vent hole 28. Two opposing sides of the substantially square recess 26A are connected to two vent lines 23a and 23b. This widens the area where the substantially square recess 26A and the two vent lines 23a and 23b are connected, which can improve the efficiency of gas flow into the spring vent 50.

[0065] Figure 6 is a plan view of a side mold 20B according to another embodiment. As shown in Figure 6, the side mold 20B has a substantially square recess 26B in plan view. A vent hole 28 is formed in the recess 26B. A spring vent 50 is fitted into the vent hole 28. Here, the vent hole 28 is formed in a position that overlaps with one of the two vent lines 23a, 23b, vent line 23a. The spring vent 50 overlaps with vent line 23a. In this case as well, the efficiency of gas discharge to the outside of the tire vulcanization mold 10 can be improved. If there is a difference in gas flow rate between the two vent lines, the vent hole may be formed to overlap with or be close to the vent line with the higher gas flow rate. This allows the amount of gas flowing in from the two vent lines to be adjusted.

[0066] Figure 7 is a plan view of a side mold 20C according to another embodiment. As shown in Figure 7, the side mold 20C has a substantially circular recess 26C in plan view. A vent hole 28 is formed in the recess 26C. A spring vent 50 is fitted into the vent hole 28. Two vent lines 23a and 23b are connected via a groove 23c that is inclined with respect to the vent lines 23a and 23b. The angle between the two vent lines 23a and 23b and the groove 23c is not particularly limited. The recess 26C is provided so as to overlap with the groove 23c. In other words, the recess 26C is connected to the two vent lines 23a and 23b via the groove 23c. Even in this case, the efficiency of gas discharge to the outside of the tire vulcanization mold 10 can be improved.

[0067] The following describes embodiments relating to the present disclosure, but the present disclosure is not intended to be limited to those shown in these embodiments. Table 1 shows the results of evaluating tires after vulcanization using tire vulcanization molds with various modifications to the depth h of the recess, the relationship between the distance r and diameter d in the recess, the angle of the bottom of the recess relative to the molding surface, and the presence or absence of connection between the recess and the vent line. In this embodiment, the recess shown in Table 1 was provided in the side mold of the tire vulcanization mold, and the above evaluation was carried out. Multiple vent lines are formed along the circumferential direction in the tire vulcanization mold of each example. In the tire vulcanization molds except for Examples 6 and 7, a vent hole is formed at the bottom of the recess, and a spring vent is fitted in the vent hole. In Example 6, the tire vulcanization mold does not have the recess described above, but a vent hole is formed. In Example 7, the tire vulcanization mold is provided with a protrusion with a height of 0.5 mm instead of the recess described above. The protrusion is indicated as "-0.5" in Table 1.

[0068] This section evaluates the frequency of defects in tires after vulcanization and the aerodynamic performance of the tire vulcanization mold. In Table 1, the relationship between distance r and diameter d is expressed as distance r(r / d) relative to diameter d.

[0069] The evaluation method was as follows: 2000 evaluation tires of size 245 / 40R18 were vulcanized consecutively. Of these, the number of tires with delamination was examined from the 1900th to the 2000th evaluation tire. Evaluation tires without delamination were selected, mounted on a vehicle, and an aerodynamic evaluation test was conducted. In the aerodynamic evaluation test, the aerodynamic performance of the evaluation tire vulcanized using the tire vulcanization mold of Example 8 was set to 100, and each example was evaluated relatively. A higher numerical value indicates lower air resistance and better aerodynamic performance. The results are shown below.

[0070] [Table 1]

[0071] In Example 6, where no recess is provided in the tire vulcanization mold, more delamination occurs in the vulcanized tires compared to Examples 1-5. Similarly, in Example 7, where a protrusion is provided in the tire vulcanization mold, more delamination occurs in the vulcanized tires compared to Examples 1-5. From the above, it can be seen that providing a recess for a spring vent in the tire vulcanization mold reduces the occurrence of delamination.

[0072] A comparison of Examples 1-4 showed that the aerodynamic effect was good when the depth of the recess was 1.0 mm or less. Also, when the depth of the recess was greater than 0.1 mm, the occurrence of bare tire after vulcanization was suppressed. A comparison of Examples 5, 8-10 showed that setting the distance r to be less than or equal to the diameter d reduced the occurrence of bare tire after vulcanization. Examples 8-13 showed that even when the bottom of the recess was inclined relative to the molded surface, the occurrence of bare tire after vulcanization was suppressed. Examples 12 and 13 showed that when the vent line and the recess were connected, the occurrence of bare tire after vulcanization was suppressed even when the number of spring vents was reduced.

[0073] The technologies disclosed herein have been described in various ways. However, the technologies disclosed herein are not limited to the embodiments described above unless otherwise specified. Furthermore, the various configurations described can be combined as appropriate, provided that they do not interfere with one another. This specification includes the following disclosures, which are not limited to the embodiments described above.

[0074] The present invention (1) relates to a tire vulcanization mold. The tire vulcanization mold in the present invention (1) is A molding surface that forms the outer shape of the tire, A recess formed on the molded surface and having a bottom, A vent hole formed in a part of the bottom of the recess, The spring vent installed in the aforementioned vent hole and Equipped with, The spring vent comprises a cylindrical housing with a through hole formed therein, and a stem inserted through the through hole of the housing. The depth of the recess is 1.0 mm or less. The distance between the edge of the through hole and the edge of the bottom of the recess is less than or equal to the diameter of the through hole.

[0075] The present invention (2) is a tire vulcanization mold described in the present invention (1), At least two vent lines are formed on the molded surface. The recess is formed between the two vent lines and is connected to the two vent lines.

[0076] The present invention (3) is a tire vulcanization mold described in the present invention (2), The recess comprises the bottom portion and the side circumferential portion connected to the molded surface, The side circumference of the recess is connected to the two vent lines.

[0077] The present invention (4) is a tire vulcanizing mold described in any of the present inventions (1) to (3), The bottom of the recess is inclined with respect to the molded surface.

[0078] The present invention (5) is a tire vulcanization mold described in the present invention (4), The angle at which the bottom is inclined with respect to the molded surface is 45 degrees or less.

[0079] The present invention (6) is a tire vulcanizing mold described in any of the present inventions (1) to (5), The planar shape of the recess is circular.

[0080] The present invention (7) is a tire vulcanizing mold described in any of the present inventions (1) to (6), The vent hole is formed in the center of the bottom of the recess. [Explanation of Symbols]

[0081] 1. Vulcanizing machine for tires 10 Tire vulcanization molds 10a Mold internal space 12,14 mold base 16. Mold opening and closing mechanism 16a Slider 16b Pusher 20, 30, 20A, 20B, 20C Side mold 20a Interface 22,32,42 Molding surface 23, 23a, 23b vent lines 23c groove 24,34 beading 26, 26A, 26B, 26C recesses 26a bottom 26a1 Edge 26b Side circumference 28 Benthole 28a Inner surface 40 Tread Mold 42a protrusion 50 Spring Bend 51 Housing 51a opening 51b Storage area 51c Reduced diameter part 51c1, 51c2 Step 51d End part 51e front 51f Rear 52 Through hole 52a Edge 53 Spring 55 Stem 55a head 55b Shaft 55c end 60 Bladder center mechanism 62 Centerpost 64, 66 Clamp Rings 68 Brada 110 Low Cover 112 Tread section 114 Sidewall section 122 parts 126 recess 126a bottom 126b Side circumference

Claims

1. A molding surface that forms the outer shape of the tire, A recess formed on the molded surface and having a bottom, A vent hole formed in a part of the bottom of the recess, The spring vent installed in the aforementioned vent hole and Equipped with, The spring vent comprises a cylindrical housing with a through hole formed therein, and a stem inserted through the through hole of the housing. The depth of the recess is 1.0 mm or less. The distance between the edge of the through hole and the edge of the bottom of the recess is less than or equal to the diameter of the through hole. At least two vent lines are formed on the molded surface. The recess is formed between the two vent lines and is connected to the two vent lines. Tire vulcanization mold.

2. The recess comprises the bottom portion and the side circumferential portion connected to the molded surface, The tire vulcanizing mold according to claim 1, wherein the side circumference of the recess is connected to the two vent lines.

3. A molding surface that forms the outer shape of the tire, A recess formed on the molded surface and having a bottom, A vent hole formed in a part of the bottom of the recess, The spring vent installed in the aforementioned vent hole and Equipped with, The spring vent comprises a cylindrical housing with a through hole formed therein, and a stem inserted through the through hole of the housing. The depth of the recess is 1.0 mm or less. The distance between the edge of the through hole and the edge of the bottom of the recess is less than or equal to the diameter of the through hole. The bottom of the recess is inclined with respect to the molded surface. Tire vulcanization mold.

4. The tire vulcanizing mold according to claim 3, wherein the angle at which the bottom portion is inclined with respect to the molding surface is 45 degrees or less.

5. The tire vulcanizing mold according to any one of claims 1 to 4, wherein the planar shape of the recess is circular.

6. The tire vulcanizing mold according to any one of claims 1 to 4, wherein the vent hole is formed in the central part of the bottom of the recess.

7. The bottom of the recess is inclined with respect to the molding surface, as described in claim 1 or 2.

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