Tire molding mold and tire manufacturing method

Abstract

To provide a tire molding mold and a tire manufacturing method that can suppress a problem of marks not being clearly formed on a sidewall surface.SOLUTION: A tire molding mold for vulcanizing and molding a pneumatic tire 1 comprising: a sidewall 20 having a marking display part 60 that protrudes from a profile line PL toward a tire axially outward and includes a marking surface 70 on its protruding end surface; and the marking display part 60 including a colored rubber 61 and a cover rubber 65 that covers the colored rubber 61, includes: an outer surface forming part 121 that forms an outer surface 23 of the sidewall 20; an emblem display part forming part 122 that is continuous with the outer surface forming part 121 and includes a recess 122a that forms the emblem display part 60; a tire maximum width position forming point 129 that forms a tire maximum width position 23a; and a vent hole 125 that connects the emblem display forming part 122 to an outside. The vent holes 125 are arranged biased toward the tire maximum width position forming point 129 in a tire radial direction.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a tire molding die for vulcanizing and molding a pneumatic tire and a method for molding a tire using the tire molding die.

Background Art

[0002] Conventionally, for the purpose of improving appearance and the like, a pneumatic tire has been known in which a protruding portion corresponding to a logo is formed on a sidewall, and a logo display portion is provided by exposing colored rubber on the surface thereof. After the colored rubber is vulcanized and molded on the sidewall in a state where the surface is covered with a thin cover rubber, the cover rubber in the portion corresponding to the logo is removed by buffing or the like, so that the logo is formed by being exposed on the surface of the sidewall (see Patent Documents 1, 2, etc.).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a tire molding die for vulcanizing and molding a tire having the above-described logo display portion, there is a concave portion corresponding to the logo display portion, and a vent hole for air venting that communicates with the outside from the concave portion is provided. However, due to the presence of the vent hole, there has been a case where the colored rubber is not sufficiently filled in the logo area, and the logo is not clearly formed in a desired shape on the sidewall surface.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a tire molding die and a tire manufacturing method capable of suppressing a problem that a logo formed on the sidewall surface is not clearly formed.

Means for Solving the Problem

[0006] The tire molding die according to the present invention has an outer surface along a profile line, and includes a sidewall that protrudes outward in the tire axial direction from the profile line and has a logo display portion including a logo surface on its protruding end face. The logo display portion is a tire molding die for vulcanizing and molding a pneumatic tire including colored rubber and cover rubber covering the colored rubber, and includes an outer surface forming portion that forms the outer surface of the sidewall, a logo display portion forming portion that is continuous with the outer surface forming portion and includes a recess that forms the logo display portion, a tire maximum width position forming point that forms a tire maximum width position, and a vent hole that communicates the logo display portion forming portion with the outside. The vent hole is disposed offset toward the side of the tire maximum width position forming point in the tire radial direction.

[0007] The method for manufacturing a tire according to the present invention is a method for manufacturing a tire by molding a tire using the tire molding die of the present invention, and includes a step of molding the logo display portion by vulcanizing and molding a rubber layer including colored rubber and cover rubber outside the colored rubber in a state of contacting the logo display portion forming portion from the cover rubber side, and a step of grinding the cover rubber to expose the colored rubber.

Advantages of the Invention

[0008] According to the present invention, it is possible to provide a tire molding die and a method for manufacturing a tire that can suppress the problem that the logo formed on the sidewall surface is not clearly formed.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

MODE FOR CARRYING OUT THE INVENTION

[0010] Hereinafter, embodiments will be described with reference to the drawings. Although the present invention relates to a tire molding die and a method for manufacturing a tire, first, a pneumatic tire according to an embodiment manufactured by the tire molding die and the method for manufacturing a tire according to the embodiment will be described.

[0011] FIG. 1 is an overall side view of a pneumatic tire 1 according to an embodiment. FIG. 2 is a half cross-sectional view in the tire axial direction (tire meridian plane) of the tire 1, and is a half cross-sectional view corresponding to a portion along line II-II in FIG. 1. FIG. 3 is an enlarged view of part III in FIG. 2, and is a partially enlarged cross-sectional view of the sidewall 20 including the logo display portion 60 according to the embodiment. FIG. 4 is a diagram showing an example of the logo 60A of the logo display portion 60.

[0012] Note that the cross-sectional view in FIG. 2 is a cross-sectional view in the tire axial direction (tire meridian cross-section) of the tire 1 in an unloaded state where the tire 1 is mounted on a regular rim (not shown) and filled with the regular internal pressure. The regular rim is the rim defined for each tire in the standard system including the standard on which the tire is based. For example, it is the standard rim in JATMA, and "Measuring Rim" in TRA and ETRTO. The regular internal pressure is the air pressure defined for each tire in the standard system including the standard on which the tire is based. In the case of tires for trucks and buses and light trucks, in JATMA, it is the maximum air pressure, in TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in ETRTO, it is "INFLATION PRESSURE". In the case of passenger car tires, it is usually 180 kPa, but in the case of tires marked with Extra Load or Reinforced, it is 220 kPa.

[0013] The tire 1 according to the embodiment is a pneumatic tire for passenger cars including light automobiles, SUVs, etc. Note that the configuration of the tire 1 of the embodiment can also be applied to pneumatic tires for various vehicles such as light trucks, trucks, and buses.

[0014] The basic structure of the tire 1 is symmetric about the tire axial direction cross-section (tire meridian cross-section). FIG. 2 shows the cross-section of the right half of the tire 1, and the left half (not shown) has the same structure. In FIG. 2, the symbol S1 is the tire equatorial plane. The tire equatorial plane S1 is a plane perpendicular to the tire rotation axis and located at the center in the tire axial direction.

[0015] Here, the tire axial direction is the direction parallel to the tire rotation axis and is the left - right direction of the paper surface in FIG. 2. In FIG. 2, it is illustrated as the tire axial direction X. The inner side in the tire axial direction is the direction approaching the tire equatorial plane S1 and is the left side of the paper surface in FIG. 2. The outer side in the tire axial direction is the direction away from the tire equatorial plane S1 and is the right side of the paper surface in FIG. 2.

[0016] Also, the tire radial direction is the direction perpendicular to the tire rotation axis and is the up - down direction of the paper surface in FIG. 2. In FIG. 2, it is illustrated as the tire radial direction Y. The outer side in the tire radial direction is the direction away from the tire rotation axis and is the upper side of the paper surface in FIG. 2. The inner side in the tire radial direction is the direction approaching the tire rotation axis and is the lower side of the paper surface in FIG. 2.

[0017] Also, the tire circumferential direction is an arc line centered on the tire rotation axis and is the direction along the rotation direction of the tire 1, and is shown in the arc line Z direction in FIGS. 1 and 4.

[0018] As shown in FIGS. 1 and 2, the tire 1 according to the embodiment includes a pair of beads 10, a pair of sidewalls 20 extending radially outward from each of the pair of beads 10, and a tread 30 disposed between the pair of sidewalls 20. Also, as shown in FIG. 2, the tire 1 according to the embodiment includes a carcass ply 40 spanned and disposed between the pair of beads 10, and an inner liner 50 disposed on the tire inner cavity side of the carcass ply 40.

[0019] The pair of beads 10 are disposed at both ends in the tire axial direction and on the inner side in the tire radial direction. As shown in FIG. 2, the bead 10 has a bead core 11, a bead filler 12 extending radially outward from the bead core 11, a chafer 13, and a rim strip rubber 14.

[0020] The bead core 11 is an annular member in which a metal bead wire coated with rubber is wound a plurality of times in the tire circumferential direction. The bead core 11 is a member that serves to fix the air-filled tire 1 to the rim.

[0021] The bead filler 12 has a tapered shape in which the thickness decreases as it extends from the inner side in the tire radial direction to the outer side in the tire radial direction. The bead filler 12 is provided to increase the rigidity of the peripheral portion of the bead 10 and ensure high maneuverability and stability. The bead filler 12 is composed of, for example, rubber having a higher hardness than the surrounding rubber members. The inner surface in the tire radial direction of the bead filler 12 is joined to the outer surface in the tire radial direction of the bead core 11.

[0022] The chafer 13 further surrounds the outside of the carcass ply 40 that surrounds the bead core 11 and the bead filler 12.

[0023] The rim strip rubber 14 is disposed on the outer side in the tire axial direction of the chafer 13 and the carcass ply 40. The rim strip rubber 14 is a member that contacts the rim on which the tire 1 is mounted.

[0024] The sidewall 20 includes a sidewall rubber 21 disposed on the outer side in the tire axial direction of the carcass ply 40, a side block 22, and a logo display portion 60. The sidewall rubber 21, the side block 22, and the logo display portion 60 constitute the outer wall surface of the tire 1.

[0025] The sidewall rubber 21 surrounds the logo display portion 60 and is disposed on the outer and inner sides in the tire radial direction of the logo display portion 60 in FIG. 2. A rim line 21a is formed on the sidewall rubber 21 on the inner side in the tire radial direction.

[0026] The side block 22 is a portion formed in a block shape at the radially outer end of the sidewall 20 in the tire diameter direction, and protrudes outward in the tire axial direction from the profile line PL of the sidewall 20. The side block 22 of the embodiment extends from the radially outer end of the sidewall 20 in the tire diameter direction to the axially outer end of the tread 30 in the tire axial direction. The radially inner side is composed of the sidewall rubber 21, and the radially outer side is composed of a rubber 22a different from the sidewall rubber 21. The rubber 22a on the radially outer side of the side block 22 covers the axially outer end of the tread 30, and an annular line 22b made of rubber of a color different from the color of the rubber of the tire 1 is formed on the radially outer portion of this rubber 22a. As shown in FIG. 1, the annular line 22b is provided over the entire circumference in the tire circumferential direction.

[0027] The sidewall 20 has an outer surface 23 along the profile line PL. The outer surface 23 here does not include the logo display portion 60 protruding outward in the tire axial direction from the profile line PL and the outer surface of the side block 22. The outer surface 23 of the sidewall 20 includes the tire maximum width position 23a of the tire 1. The tire maximum width position 23a of the embodiment exists on the outer surface 23 of the sidewall 20 and is not the outermost portion in the tire axial direction of the logo display portion 60. Note that the tire maximum width position 23a of the embodiment is located radially outside the logo display portion 60 protruding outward in the tire axial direction from the profile line PL and is located on the surface of the cover rubber 65 along the profile line PL.

[0028] The sidewall 20 is the portion that bends the most when the tire 1 acts as a cushion. Therefore, usually, the sidewall rubber 21 of the sidewall 20 is made of a flexible rubber having fatigue resistance. Details of the logo display portion 60 will be described later.

[0029] The tread 30 has an endless belt 31, a cap ply 32, and a tread rubber 33.

[0030] The belt 31 is disposed on the outer side in the tire radial direction of the carcass ply 40. The cap ply 32 is disposed on the outer side in the tire radial direction of the belt 31.

[0031] The belt 31 is a member for reinforcing the tread 30. The belt 31 of the embodiment has a two-layer structure having an outer belt 311 and an inner belt 312 in the tire radial direction. Both the outer belt 311 and the inner belt 312 have a structure in which a plurality of cords such as steel cords are covered with rubber. Note that the belt 31 is not limited to a two-layer structure, and may have a single-layer or a three-layer or more structure.

[0032] The cap ply 32 is a member for reinforcing the tread 30 together with the belt 31. The cap ply 32 has a structure in which a plurality of insulating organic fiber cords such as polyamide fibers are covered with rubber. By providing the cap ply 32, it is possible to improve durability and reduce road noise during driving.

[0033] The tread rubber 33 is disposed on the outer side in the tire radial direction of the cap ply 32. The tread rubber 33 is a member constituting the tread surface 34 which is the outer surface of the tread 30.

[0034] The carcass ply 40 constitutes a ply that forms the skeleton of the tire 1. The carcass ply 40 is embedded in the tire 1 in a manner passing between a pair of beads 10 through a pair of sidewalls 20 and the tread 30. The carcass ply 40 includes a plurality of carcass cords (not shown) that form the skeleton of the tire 1. The plurality of carcass cords extend, for example, in the tire axial direction and are arranged side by side in the tire circumferential direction. The carcass cords are composed of insulating organic fiber cords such as polyester and polyamide. The plurality of carcass cords are covered with rubber to form the carcass ply 40.

[0035] The carcass ply 40 extends from one bead core 11 to the other bead core 11, and has a ply main body portion 40A that extends between the tread 30 and the bead 10, a pair of bent portions 40B that are folded back by the bead core 11 from the ply main body portion 40A, and a pair of folded-back portions 40C that extend radially outward of the tire from each of the bent portions 40B. The ply main body portion 40A, the bent portions 40B, and the folded-back portions 40C surround the bead filler 12 and the bead core 11. The folded-back portion 40C of the portion radially outside the tire of the bead filler 12 is overlapped with the ply main body portion 40A.

[0036] The carcass ply 40 of the embodiment has a two-layer structure including a first carcass ply 41 on the outer side in the tire radial direction and a second carcass ply 42 on the inner side in the tire radial direction in the tread 30 portion. The carcass ply 40 is not limited to such a two-layer structure, and may have a single-layer or a three-layer or more structure.

[0037] The chafer 13 of the bead 10 described above is provided so as to surround the inner end portion in the tire radial direction of the carcass ply 40 including the bent portion 40B. Further, the rim strip rubber 14 is disposed on the outer side in the tire axial direction of the chafer 13 and the folded-back portion 40C of the carcass ply 40. The outer side in the tire radial direction of the rim strip rubber 14 is covered with the sidewall rubber 21.

[0038] The inner liner 50 is a member that constitutes the inner surface of the tire 1, and covers the inner surface of the ply main body portion 40A of the carcass ply 40 and the inner surface of the chafer 13 of the pair of beads 10. The inner liner 50 is made of an air permeation resistant rubber, and prevents the air in the tire inner cavity from leaking to the outside. The inner liner 50 of the tire 1 of the embodiment is composed of two layers of an outer inner liner 51 and an inner inner liner 52, but the inner liner 50 may have a single-layer structure.

[0039] As shown in FIGS. 2 and 3, the logo display portion 60 protrudes outward in the tire axial direction from the profile line PL of the sidewall 20. The logo display portion 60 has a flat logo surface 70 on its protruding end face. As shown in FIG. 1, the logo display portions 60 are arranged at two locations that are 180° apart from each other in the tire circumferential direction. As shown in FIG. 2, the logo display portion 60 of the embodiment is arranged inside the tire in the radial direction at the tire maximum width position 23a.

[0040] The logo display portion 60 includes a rubber layer 69 having a colored rubber 61 and a cover rubber 65. The colored rubber 61 is arranged outside the carcass ply 40 in the tire axial direction. The cover rubber 65 is arranged outside the colored rubber 61 in the tire radial direction so as to cover the colored rubber 61. The logo display portion 60 is a portion where a "T" is artistically drawn and displayed as shown in FIG. 4 when the tire 1 is viewed from the side.

[0041] The color of the cover rubber 65 is preferably black, which is the same color as the tire 1. As the color of the colored rubber 61, white, which provides a clear contrast with black, is preferred, but it is not limited to this, and for example, yellow, green, red, etc. can also be selected.

[0042] As shown in FIGS. 3 and 4, the portion that is substantially visually recognized as the logo 60A in the logo display portion 60, that is, the portion visually recognized as the "T", is formed by an exposed portion 62 of the colored rubber 61 that protrudes from the surface of the sidewall 20 and is exposed on the side surface of the sidewall 20, and a border 66 formed by the cover rubber 65 arranged so as to surround the colored rubber 61. The surfaces of the exposed portion 62 of the colored rubber 61 and the border 66 of the cover rubber 65 form the same flat surface. That is, the logo 60A (the letter "T") is composed of a flat single surface.

[0043] As shown in FIG. 3, the cover rubber 65 is a relatively thin rubber film, which is arranged on the outer surface side of the colored rubber 61 in the tire and covers the portion other than the exposed portion 62 of the colored rubber 61.

[0044] The logo display portion 60 is formed so as to protrude outward in the tire axial direction from the profile line PL of the sidewall 20 at a part of the tire circumferential direction of the sidewall 20 when the tire 1 is vulcanized and molded. After the tire 1 is vulcanized and molded, the colored rubber 61 is entirely covered by the cover rubber 65, and the exposed portion 62 is not formed. After the vulcanization molding of the tire 1, the cover rubber 65 at the portion corresponding to the logo 60A is removed by means such as buffing, so that the colored rubber 61 is exposed, and the logo 60A composed of the exposed portion 62 formed by the colored rubber 61 and the border 66 formed by the cover rubber 65 is exposed. The ground surface of the logo display portion 60 constitutes the logo surface 70 which is a flat single surface of the logo 60A.

[0045] As shown in FIGS. 3 and 4, the logo display portion 60 further includes an outer corner portion 72 extending from the outer edge 71 forming the outermost contour of the logo surface 70 to the profile line PL along the outer surface 23 of the sidewall 20. The outer corner portion 72 is formed over the entire circumference of the outer shape of the logo 60A. As shown in FIG. 3, the outer corner portion 72 includes a curved surface 72a having a cross-sectional arc shape that is concave on the side of the logo surface 70 of the logo display portion 60.

[0046] The above is the configuration of the tire 1 according to the embodiment. Next, with reference to FIGS. 5 to 10, a tire molding die 100 for vulcanizing and molding the tire 1 and a manufacturing method for manufacturing the tire 1 using this tire molding die 100 will be described.

[0047] FIG. 5 schematically shows a state in which the tire 1 is vulcanized and molded by the tire molding die 100 according to the embodiment. FIG. 5 is a cross-sectional view along the tire axial direction (tire meridian plane). FIG. 6 is an enlarged view of the portion indicated by VI in FIG. 5. In FIG. 6, the illustration of the bladder 140 described later is omitted. In FIGS. 5 and 6, the hatching of the tire 1 is partially omitted.

[0048] Before vulcanization molding, the tire 1 is set in the tire molding die 100 with the tire axial direction along the vertical direction. In FIGS. 5 and 6, similar to FIG. 2, the tire axial direction of the tire 1 to be vulcanization molded is indicated by X, and the tire radial direction is indicated by Y. In the following description of the tire molding die 100, these tire axial direction and tire radial direction corresponding to the tire 1 to be vulcanization molded are applied. Note that the tire 1 when set in the tire molding die 100 is in a state called a so-called green tire before vulcanization and has substantially different characteristics from the tire 1 after vulcanization molding. Here, however, the description will proceed by referring to it as "the tire 1 before vulcanization molding".

[0049] The tire molding die 100 has a segmented mold structure and is housed in a container (not shown). As shown in FIG. 5, the tire molding die 100 includes a plurality of sector molds 110, a pair of upper and lower side plates 120, and a pair of upper and lower bead rings 130. The plurality of sector molds 110 mainly have the function of forming the tread 30 of the tire 1, the pair of side plates 120 mainly have the function of forming the sidewall 20 of the tire 1, and the pair of bead rings 130 mainly have the function of forming the bead 10 of the tire 1.

[0050] The plurality of sector molds 110 are provided so as to be expandable and contractible in the tire radial direction when the tire molding die 100 is opened and closed. For example, each sector mold 110 is separated radially in the mold open state and abuts against each other and is assembled annularly in the mold closed state. The tire molding die 100 further includes a drive device (not shown) that performs mold clamping and mold opening via the above container. In addition, the tire molding die 100 is attached with a bladder 140 that bulges the tire 1 from the inner cavity side during vulcanization molding and presses it against the molding surface that is the inner surface of the tire molding die 100.

[0051] As shown in FIG. 6, the logo display portion 60 of the tire 1 described above is formed by the molding surface 120A of the side plate 120. The molding surface 120A of the side plate 120 has an outer surface forming portion 121 that forms the outer surface 23 of the sidewall 20, a logo display portion forming portion 122 that is continuous with the outer surface forming portion 121 and forms the logo display portion 60, and a tire maximum width position forming point 129 that forms the tire maximum width position 23a. Further, the side plate 120 has a vent hole 125 that communicates the logo display portion forming portion 122 with the outside of the side plate 120. The side plate 120 shown in FIG. 6 is the upper side plate 120 in FIG. 5, but the lower side plate 120 also has the same molding surface 120A.

[0052] The outer surface forming portion 121 has a gentle concave shape corresponding to the outer surface 23 of the sidewall 20 along the profile line PL in the tire 1. The outer surface forming portion 121 is formed so as to surround the logo display portion forming portion 122, and is formed on both sides in the tire radial direction of the logo display portion forming portion 122 in FIG. 6. The tire maximum width position forming point 129 is located on the outer side in the tire radial direction of the logo display portion forming portion 122 that protrudes outward in the tire axial direction from the profile line PL and is close to the logo display portion forming portion 122.

[0053] FIG. 7 is a cross-sectional view of the side plate 120 showing the logo display portion forming portion 122, and shows a cross-section corresponding to a cross-sectional view in the tire axial direction. FIG. 8 is a view taken in the direction of arrow XIII in FIG. 7. As shown in FIGS. 7 and 8, the logo display portion forming portion 122 includes a concave portion 122a having a shape corresponding to the logo display portion 60. This concave portion 122a is a recess in the shape in which the "T", which is the logo 60A of the logo display portion 60 of the embodiment, is transferred, as shown in FIG. 8.

[0054] As shown in FIGS. 7 and 8, the emblem display portion forming portion 122 includes a first end portion 123 that is farthest from the tire maximum width position forming point 129 in the tire radial direction (vertical direction in FIGS. 7 and 8). A first groove portion 123a is formed as a first recess in this first end portion 123. The first groove portion 123a extends linearly in a direction generally along the tire circumferential direction.

[0055] Further, the emblem display portion forming portion 122 includes a second end portion 124 that is closest to the tire maximum width position forming point 129 in the tire radial direction as a second recess. A second groove portion 124a is formed as a second recess in this second end portion 124. The second groove portion 124a extends linearly in a direction generally along the tire circumferential direction.

[0056] Here, it is preferable that the depth of the first groove portion 123a is greater than the depth of the second groove portion 124a. In that case, the depth of the first groove portion 123a is preferably, for example, 2 times or more and 4 times or less the depth of the second groove portion 124a. Note that the depth of each of the groove portions 123a and 124a is not limited to this, and the depths may be the same, or conversely, the depth of the second groove portion 124a may be greater than the depth of the first groove portion 123a. Note that the depth of the first groove portion 123a is preferably greater than the thickness of the cover rubber 65. For example, for the cover rubber 65 having a thickness of about 0.65 mm, the depth of the first groove portion 123a is, for example, about 1.5 mm, but it is not limited to this.

[0057] As shown in FIG. 7, the emblem display portion forming portion 122 includes a first side wall surface 123b extending from the first groove portion 123a to the outer surface forming portion 121 on the inner side in the tire radial direction. This first side wall surface 123b has a first curved surface 123c that is convex toward the inside of the emblem display portion forming portion 122 and has a cross-sectional arc shape. The emblem display portion forming portion 122 includes a second side wall surface 124b extending from the second groove portion 124a to the outer surface forming portion 121 on the outer side in the tire radial direction. This second side wall surface 124b has a second curved surface 124c that is convex toward the inside of the emblem display portion forming portion 122 and has a cross-sectional arc shape.

[0058] As shown in FIGS. 6 and 7, the vent hole 125 is a thin hole that communicates the concave portion 122a included in the logo display portion forming portion 122 and the outside of the side plate 120 (the space on the right side of the side plate 120 in FIGS. 6 and 7). The vent hole 125 is formed to penetrate the side plate 120 so as to extend substantially parallel to the tire axis direction. The vent hole 125 is, for example, a round hole having a circular cross section, and its inner diameter is about 1.35 mm, but the cross-sectional shape and dimensions are not limited to this.

[0059] As shown in FIGS. 6 and 7, in the tire diameter direction, the vent hole 125 of the embodiment is disposed so as to be biased toward the side of the tire maximum width position forming point 129 within the region of the logo display portion forming portion 122. Specifically, the vent hole 125 is in the vicinity of the second groove portion 124a and is disposed inside the second groove portion 124a in the tire diameter direction. Note that the width of the second groove portion 124a may be larger or smaller than the inner diameter of the vent hole 125.

[0060] The number of vent holes 125 may be one, but a plurality of vent holes may be provided according to the shape of the logo 60A. For example, in the embodiment, as shown in FIG. 8, when one is disposed at each end of the line extending horizontally of the logo 60A, that is, "T", at both ends of the second groove portion 124a, the function of the vent hole 125 as air venting is preferably easily fulfilled sufficiently.

[0061] The above is the configuration of the tire molding die 100 according to the embodiment. To vulcanize and mold the tire 1 using this tire molding die 100, first, the tire 1 before vulcanization molding is placed on the lower side plate 120 and the bead ring 130 with its axial direction along the vertical direction in the tire molding die 100 in the open mold state. Next, air is supplied into the bladder 140 to expand it, and the inner cavity surface of the tire 1 before vulcanization molding is held on its outer peripheral surface. Subsequently, the tire molding die 100 is closed by a driving device (not shown), so that the outer surface of the tire 1 is pressed by the plurality of sector molds 110, the pair of side plates 120, and the pair of bead rings 130, and the inner cavity surface of the tire 1 is pressed by the bladder 140. That is, the tire 1 before vulcanization molding is press-molded by the tire molding die 100. Then, by heating to a predetermined vulcanization molding temperature (for example, 100° to 200°) and passing through a predetermined vulcanization molding time (for example, several hours to several tens of hours), the vulcanized and molded tire 1 is obtained.

[0062] During the press molding by closing the tire molding die 100, due to the expansion of the tire 1, the rubber layer 69 including the colored rubber 61 and the cover rubber 65 on the outer side in the tire diameter direction of the colored rubber 61 is filled into the concave portion 122a of the emblem display portion forming portion 122 from the cover rubber 65 side. Thereby, the emblem display portion 60 is formed. At this time, as shown in FIG. 6, the rubber layer 69 is filled into the first groove portion 123a of the emblem display portion forming portion 122 to form the first convex portion 67, and the rubber layer 69 is filled into the second groove portion 124a of the emblem display portion forming portion 122 to form the second convex portion 68.

[0063] When the rubber layer 69 is filled into the recess 122a of the logo display portion forming portion 122, the air to be enclosed in the recess 122a flows out from the vent hole 125 to the outside of the side plate 120, and the air is discharged, and the rubber layer 69 fills the recess 122a. The rubber layer 69 is filled into the vent hole 125 while pushing out the air, but the vent hole 125 is mainly filled with the colored rubber 61 by piercing through the thin cover rubber 65. Here, as shown in FIGS. 5 and 6, a protrusion 90, also called a spout, which protrudes outward in the tire axial direction from the logo display portion 60, is formed in the vent hole 125 by the filled rubber layer 69 (mainly the colored rubber 61).

[0064] FIG. 9 shows the logo display portion 60 of the tire 1 that has been vulcanized and molded as described above and demolded from the mold 100. As shown in FIGS. 6 and 9, in the logo display portion 60 of the tire 1 after vulcanization molding, almost the entire surface on the outer side in the tire axial direction is covered with the cover rubber 65, and the colored rubber 61 is in a state where it cannot be visually recognized. Two protrusions 90 made of the rubber layer 69 (mainly the colored rubber 61) filled in the vent hole 125 are formed on the inner side in the tire radial direction (lower side in FIG. 9) of the second convex portion 68.

[0065] Next, for the tire 1 after vulcanization molding, the surface layer of the protruding end face on the outer side in the tire axial direction of the logo display portion 60 is buffed, the cover rubber 65 of the portion corresponding to the logo 60A is removed, and the exposed portion 62 of the colored rubber 61 is exposed to process it into a state where the logo 60A is displayed.

[0066] FIG. 10 schematically shows a state in which the surface layer of the logo display portion 60 is buffed by the buffing machine 200. Similar to FIG. 2, FIG. 10 shows a half cross section in the tire axial direction. The buffing machine 200 is configured such that a buff 210 and a shoe 220, both having a cylindrical roller shape, are concentrically arranged and rotate about a rotation axis 230. The tire 1 is mounted on a rim (not shown) and is rotatably supported around the rotation axis.

[0067] The buffing machine 200 is disposed on the outer side in the tire axial direction of the emblem display portion 60 so as to be separable from and attachable to the emblem display portion 60, and grinds the emblem display portion 60 with the buff 210 by approaching it. The rotation axis 230 of the buff 210 extends so as to incline at a certain angle toward the outer side in the tire axial direction as it goes toward the outer side in the tire diameter direction within the cross-section in the tire axial direction. The shoe 220 has its outer peripheral surface in contact with the sidewall 20 of the tire 1, thereby regulating the grinding depth of the buff 210. While the buff 210 grinds the surface layer of the protruding end face of the emblem display portion 60, the tire 1 is rotated, and the emblem display portion 60 is buffed by the rotation of the tire 1 for the area of the emblem display portion 60. Although FIG. 10 shows the protrusion 90 by the rubber layer 69 filled in the vent hole 125, this protrusion 90 may be cut off and removed in advance when buffing.

[0068] By buffing, the surface layers of the cover rubber 65 and the color rubber 61 of the portion corresponding to the emblem 60A are removed. When the protrusion 90 remains, the protrusion 90 is also removed by buffing. At this time, the first convex portion 67 and the second convex portion 68 are also removed. As a result, as shown in FIGS. 3 and 4, a flat emblem surface 70 including the exposed portion 62 of the color rubber 61 and the border 66 by the cover rubber 65 is formed, and the emblem 60A (character "T") is displayed.

[0069] The curved surface 72a of the outer corner portion 72 on the inner side in the tire diameter direction in the emblem display portion 60 of the tire 1 shown in FIG. 3 is formed by the first side wall surface 123b having the first curved surface 123c of the side plate 120 of the tire molding die 100 shown in FIG. 7. The curved surface 72a of the outer corner portion 72 on the outer side in the tire diameter direction in the emblem display portion 60 of the tire 1 shown in FIG. 3 is formed by the second side wall surface 124b having the second curved surface 124c of the side plate 120 of the tire molding die 100 shown in FIG. 7.

[0070] As described above, in the tire molding die 100 of the embodiment, the vent hole 125 formed in the side plate 120 is located on the side of the tire maximum width position forming point 129 in the tire radial direction within the region of the emblem display portion forming portion 122 and near the second groove portion 124a. Thereby, the following effects can be obtained.

[0071] During vulcanization molding, the flow pressure of the rubber layer 69 (color rubber 61 and cover rubber 65) in the tire 1 is greater near the tire maximum width position 23a than at positions away from the tire maximum width position 23a in both radial directions of the tire due to the bulging action of the bladder 140. Therefore, the rubber layer 69 tends to be less likely to flow as it moves from the tire maximum width position 23a toward both sides in the tire radial direction. Due to this, if there is a vent hole at a position inside and / or outside the tire radial direction away from the tire maximum width position forming point 129 within the emblem display portion forming portion 122 in the tire molding die 100, the rubber layer 69 to be filled in the emblem display portion forming portion 122 near that position is likely to flow into the vent hole, and thus there may be a situation where the emblem display portion forming portion 122 near that position is not sufficiently filled with the rubber layer 69.

[0072] FIG. 11 shows a comparative example in which a vent hole 127 communicating the recess 122a of the emblem display portion forming portion 122 with the outside is added at a position outside the tire radial direction away from the tire maximum width position forming point 129 within the region of the emblem display portion forming portion 122 of the side plate 120. FIG. 12 shows the emblem display portion 60 formed by vulcanization using the tire molding die shown in FIG. 11.

[0073] The vent hole 127 shown in FIG. 11 is in the vicinity of the first groove portion 123a and is arranged on the inner side in the tire radial direction of the first groove portion 123a. When the vent hole 127 is formed at this position, in the tire 1, since the flow pressure of the rubber layer 69 at a position away from the tire maximum width position 23a in the tire radial direction is relatively low, the rubber layer 69 filled in the emblem display portion forming portion 122 is more likely to flow into the vent hole 127 than into the first groove portion 123a. In the vent hole 127, protrusions 91 are mainly formed by the colored rubber 61 of the rubber layer 69. For this reason, the rubber layer 69 that should be filled in the first groove portion 123a flows into the vent hole 127 and the first groove portion 123a is not sufficiently filled with the rubber layer 69. For example, a space 123f remains at the bottom of the first groove portion 123a, and due to the low filling pressure of the colored rubber 61, a thick portion 65a of the cover rubber 65 with a thicker cover rubber 65 than in the normal case may be formed. When the surface layer of the emblem display portion 60 is buffed as described above in this state, as shown in FIG. 12, the thick portion 65a of the cover rubber 65 enters the exposed portion 62 of the colored rubber 61, and a problem occurs that the emblem 60A is not clearly formed in the desired shape.

[0074] However, according to the tire molding die 100 of the embodiment, within the region of the emblem display portion forming portion 122 of the side plate 120, the vent hole 125 is arranged biased toward the side of the tire maximum width position forming point 129, and the vent hole 127 is not formed at a position away from the tire maximum width position forming point 129 on the outer side in the tire radial direction. As a result, the problem that the rubber layer 69 preferentially flows into the vent hole 127 and the first groove portion 123a is not sufficiently filled with the rubber layer 69, and the thick portion 65a of the cover rubber 65 is formed is unlikely to occur. Therefore, the first groove portion 123a is sufficiently filled with the rubber layer 69, and the emblem 60A in the desired shape is clearly formed.

[0075] The logo display portion 60 is formed by inflating and filling the recess 122a of the logo display portion forming portion 122 of the tire mold 100 with a rubber layer 69 including colored rubber 61 and cover rubber 65 during the vulcanization molding of the tire 1. Here, since the logo display portion forming portion 122 has a first groove portion 123a at a first end portion 123 that is farthest from the tire maximum width position forming point 129 in the tire radial direction, the rubber layer 69 of the logo display portion 60 is also filled in this first groove portion 123a. The rubber layer 69 filled in the first groove portion 123a is formed as a first convex portion 67 that further protrudes outward in the tire axial direction. Thereby, at the first end portion 123, a rubber layer 69 with a protruding height sufficient for the colored rubber 61 to be sufficiently exposed even after buffing can be filled. Thereby, for the tire 1 after buffing the logo display portion 60, the colored rubber 61 is clearly exposed even in the vicinity of the end portion farthest from the tire maximum width position 23a of the logo display portion 60, and blurring of the logo 60A is suppressed.

[0076] On the other hand, since the logo display portion forming portion 122 has a second groove portion 124a at a second end portion 124 that is closest to the tire maximum width position forming point 129, the rubber layer 69 of the logo display portion 60 is also filled in this second groove portion 124a. The rubber layer 69 filled in the second groove portion 124a is formed as a second convex portion 68 that further protrudes outward in the tire axial direction. Thereby, also at the second end portion 124, a rubber layer 69 with a protruding height sufficient for the colored rubber 61 to be sufficiently exposed after buffing can be filled. Thereby, for the tire 1 after buffing the logo display portion 60, the colored rubber 61 is clearly exposed even in the vicinity of the end portion closest to the tire maximum width position 23a of the logo display portion 60, and blurring of the logo 60A is suppressed.

[0077] In addition, in the logo display portion 60, as the distance from the tire maximum width position 23a to the outside in the tire radial direction increases, it may be difficult for the buff 210 to reach during buff grinding, and the colored rubber 61 may be difficult to be exposed. Therefore, by making the depth of the first groove portion 123a on the first end portion 123 side, which is the farthest from the tire maximum width position forming point 129, larger than the depth of the second groove portion 124a on the second end portion 124 side, which is the closest to the tire maximum width position forming point 129, the degree of protrusion of the first convex portion 67 after vulcanization molding becomes larger. For this reason, even in the vicinity of the end portion of the logo display portion 60 that is separated from the tire maximum width position 23a to the outside in the tire radial direction, the buff 210 can reach sufficiently during buff grinding, and the colored rubber 61 can be easily exposed on the logo surface 70.

[0078] According to the embodiment described above, the following effects can be obtained.

[0079] (1) The tire molding die 100 according to the embodiment has an outer surface 23 along the profile line PL, and includes a sidewall 20 that protrudes outward in the tire axial direction from the profile line PL and has a logo display portion 60 including a logo surface 70 on its protruding end surface. The logo display portion 60 includes a colored rubber 61 and a cover rubber 65 that covers the colored rubber 61, and is a tire molding die for vulcanization molding an inflated tire 1. It includes an outer surface forming portion 121 that forms the outer surface 23 of the sidewall 20, a logo display portion forming portion 122 that is continuous with the outer surface forming portion 121 and includes a recess 122a that forms the logo display portion 60, a tire maximum width position forming point 129 that forms the tire maximum width position 23a, and a vent hole 125 that communicates the logo display portion forming portion 122 with the outside. The vent hole 125 is disposed offset to the side of the tire maximum width position forming point 129 in the tire radial direction.

[0080] Within the region of the logo display portion forming portion 122 of the tire molding die 100, the vent hole 125 is disposed offset toward the side of the tire maximum width position forming point 129, and no vent hole is formed at a position radially outward of the tire maximum width position forming point 129 in the tire radial direction. As a result, the color rubber 61 and the cover rubber 65 are easily filled sufficiently throughout the logo display portion forming portion 122. Therefore, the tire 1 molded by the tire molding die 100 includes a logo display portion 60 in which a defect that the logo 60A formed on the outer surface 23 of the sidewall 20 is not clearly formed is suppressed.

[0081] (2) In the tire molding die 100 of (1) according to the embodiment, the logo display portion 60 of the tire 1 is disposed on at least one of the inner and outer sides in the tire radial direction of the tire maximum width position 23a, and the logo display portion 60 has a first convex portion 67 protruding outward in the tire axial direction and a second convex portion 68 disposed on the side of the tire maximum width position 23a with respect to the first convex portion 67 and protruding outward in the tire axial direction. The first convex portion 67 has a greater protruding height outward in the tire axial direction than the second convex portion 68. The logo display portion forming portion 122 of the tire molding die 100 has a first groove portion 123a as a first concave portion forming the first convex portion 67 and a second groove portion 124a as a second concave portion forming the second convex portion 68, and the vent hole 125 is disposed in the vicinity of the second groove portion 124a.

[0082] Since the first convex portion 67 located farther from the tire maximum width position 23a has a greater protruding height outward in the tire axial direction than the second convex portion 68 disposed on the side of the tire maximum width position 23a, the first groove portion 123a forming the first convex portion 67 has a greater depth than the second groove portion 124a forming the second convex portion 68. Here, since the vent hole 125 is disposed in the vicinity of the second groove portion 124a offset toward the side of the tire maximum width position forming point 129, the rubber layer 69 is sufficiently filled in the first groove portion 123a as described above. That is, the color rubber 61 and the cover rubber 65 are also sufficiently filled in the first groove portion 123a having a greater depth than the second groove portion 124a, and the logo 60A having a desired shape is clearly formed.

[0083] (3) The method for manufacturing a tire according to the embodiment is a method for manufacturing a tire by molding a tire using the tire molding die 100 according to the embodiment. The method includes a step of molding a logo display portion 60 by vulcanizing and molding a rubber layer 69 including a colored rubber 61 and a cover rubber 65 outside the colored rubber 61 in a state of being in contact with the logo display portion forming portion 122 from the cover rubber 65 side, and a step of grinding the cover rubber 65 to expose the colored rubber 61.

[0084] Thereby, it is possible to mold a tire provided with a logo display portion 60 that suppresses a defect in which a logo 60A formed on the outer surface 23 of the sidewall 20 is not clearly formed.

[0085] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments, and even if modifications, improvements, etc. are made within the range that can achieve the object of the present invention, they are included in the scope of the present invention.

[0086] In the above embodiment, the letter "T" in English characters is shown as an example of the logo display portion. However, for example, as English characters, a logo display portion 80 having a logo 80A of "S" shown in FIGS. 1 and 13 may be provided. As shown in FIG. 13, similar to the logo display portion 60 of the above embodiment, the logo display portion 80 has a flat logo surface 70 on its protruding end surface, and an exposed portion 62 made of the colored rubber 61 and a border 66 made of the cover rubber 65 arranged so as to surround the colored rubber 61 are formed on the logo surface 70.

[0087] In the case of the tire molding die 100, as shown in FIG. 14, on the molding surface 120A of the side plate 120 that forms the sidewall 20, a concave portion 122a having a shape in which the "S", which is the logo 80A of the logo display portion 80, is transferred is provided as the logo display portion forming portion 122. Also in this case, in the tire radial direction (the vertical direction in FIG. 14), the logo display portion forming portion 122 has a first groove portion 123a formed at a first end portion 123 that is farthest from the tire maximum width position forming point, and a second groove portion 124a formed at a second end portion 124 that is closest to the tire maximum width position forming point. And a vent hole 125 is disposed in the vicinity of the second groove portion 124a and on the inner side in the tire radial direction (the lower side in FIG. 14) of the second groove portion 124a. In this case, the vent holes 125 are disposed one by one at both ends of the upper horizontal extending line of the logo 80A, that is, "S", and at both ends of the second groove portion 124a.

[0088] The logo display portions 60 and 80 of the above-described embodiment are disposed on the inner side in the tire radial direction of the tire maximum width position 23a, but the logo display portions 60 and 80 may be disposed on the outer side in the tire radial direction of the tire maximum width position 23a. Also in this case, the vent holes formed in the tire molding die 100 are disposed so as to be biased toward the side of the tire maximum width position forming point 129 in the logo display portion forming portion 122.

Explanation of Reference Numerals

[0089] 1 Pneumatic tire 20 Sidewall 23 Outer surface of sidewall 60, 80 Logo display portion 61 Colored rubber 65 Cover rubber 67 First convex portion 68 Second convex portion 69 Rubber layer 70 Logo surface 100 Tire molding die 121 Outer surface forming portion 122 Logo display portion forming portion 122a Concave portion 123a First groove portion (first concave portion) 124a Second groove part (second recess) 125 Vent hole 129 Tire maximum width position forming point PL Profile line

Claims

1. A tire molding die for vulcanizing and molding a pneumatic tire having a sidewall with an outer surface along a profile line, protruding outward in the tire axial direction from the profile line, and having a logo display portion including a logo surface on the protruding end surface, the logo display portion including colored rubber and cover rubber covering the colored rubber, comprising: an outer surface forming portion forming the outer surface of the sidewall; a logo display portion forming portion continuous with the outer surface forming portion and including a recess forming the logo display portion; a tire maximum width position forming point forming a tire maximum width position; a vent hole communicating the logo display portion forming portion with the outside; and the vent hole is disposed offset toward the side of the tire maximum width position forming point in the tire radial direction, the tire molding die.

2. The logo display portion of the pneumatic tire is disposed on at least one of the inner and outer sides in the tire radial direction of the tire maximum width position, the logo display portion has a first convex portion protruding outward in the tire axial direction and a second convex portion disposed closer to the tire maximum width position than the first convex portion and protruding outward in the tire axial direction, the first convex portion has a greater protruding height outward in the tire axial direction than the second convex portion, the logo display portion forming portion of the tire molding die has a first recess forming the first convex portion and a second recess forming the second convex portion, the vent hole is disposed in the vicinity of the second recess, the tire molding die according to claim 1.

3. A method for manufacturing a pneumatic tire by molding a pneumatic tire using the tire molding die according to claim 1 or 2, comprising: a step of molding the logo display portion by vulcanizing and molding a rubber layer including colored rubber and cover rubber outside the colored rubber in a state of contacting the logo display portion forming portion from the cover rubber side; and a step of grinding the cover rubber to expose the colored rubber, the method for manufacturing a pneumatic tire.

Images