Tire vulcanizing mold, tire vulcanizing apparatus, and method for vulcanizing green tires

Abstract

To provide a tire vulcanization mold capable of suppressing over-vulcanization in the tire sidewall region.SOLUTION: This is a tire vulcanizing mold 1 for heating and vulcanizing raw tires. This tire vulcanizing mold 1 is equipped with: an upper side mold 11 equipped with an upper side molding surface 16a for forming the upper sidewall of a pair of sidewalls of a raw tire 3, which is placed horizontally with its tire axis 3s oriented nearly vertically; a lower side mold 12 equipped with a lower side molding surface 16b for forming the lower sidewall of the pair of sidewalls; and a tread mold 13 equipped with a tread forming surface 16c for forming the tread portion of the green tire 3. The overall thermal conductivity of the upper side mold 11 is lower than that of the lower side mold 12.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a tire vulcanizing mold, a tire vulcanizing apparatus, and a method for vulcanizing a raw tire. [Background technology]

[0002] Patent Document 1 listed below describes a tire vulcanizing mold that includes a mold body that heats the outside of a tire with heat from a heat source. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-091150 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, to vulcanize a green tire, steam is supplied to the cavity of the green tire placed horizontally inside a tire vulcanization mold. Part of this steam is cooled and condensed in the cavity of the green tire, and accumulates as a drain in the position of the lower sidewall of the pair of sidewalls of the green tire. This drain causes the lower sidewall to be at a lower temperature than the upper sidewall, which can easily result in insufficient vulcanization.

[0005] In the above cases, since the lower sidewall portion tends to be the rate-limiting portion of vulcanization, the vulcanization time is sometimes set so as not to under-vulcanize the lower sidewall portion. However, when the vulcanization time is set as described above, the upper sidewall portion, which is not affected by drain, may become over-vulcanized. Such over-vulcanization of the sidewall portion may have a negative impact on tire quality, particularly on the rolling resistance performance of the tire.

[0006] The present invention has been devised in view of the above circumstances, and its main object is to provide a tire vulcanization mold that can prevent over-vulcanization of the sidewall portion of a tire. [Means for solving the problem]

[0007] The present invention is a tire vulcanization mold for heating and vulcanizing a green tire, comprising: an upper side mold having an upper side molding surface for molding the upper of a pair of sidewall portions of a green tire placed horizontally with the tire axis oriented approximately vertically; a lower side mold having a lower side molding surface for molding the lower of the pair of sidewall portions; and a tread mold having a tread molding surface for molding the tread portion of the green tire, wherein the thermal conductivity of the upper side mold as a whole is lower than the thermal conductivity of the lower side mold as a whole. [Effects of the Invention]

[0008] By adopting the above-described configuration, the tire vulcanizing mold of the present invention can suppress over-vulcanization of the sidewall portion of the tire. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a tire vulcanizing apparatus including a tire vulcanizing mold. [Figure 2] FIG. 2 is a partially enlarged view of a tire vulcanization mold. [Figure 3] 1 is a flowchart showing an example of a processing procedure of a method for vulcanizing a raw tire. [Figure 4] 10 is a flowchart showing an example of a procedure for a vulcanization step. [Figure 5] FIG. 2 is a cross-sectional view showing an example of a tire vulcanizing apparatus during a vulcanization process. [Figure 6] FIG. 2 is a cross-sectional view showing a tire vulcanizing mold according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be understood that the drawings include exaggerated representations and representations that differ from the dimensional ratios of actual structures in order to facilitate understanding of the contents of the invention. Furthermore, identical or common elements are designated by the same reference numerals throughout the embodiments, and redundant explanations will be omitted. Furthermore, the specific configurations shown in the embodiments and drawings are for the purpose of understanding the contents of the present invention, and the present invention is not limited to the specific configurations shown in the drawings.

[0011] FIG. 1 is a cross-sectional view showing an example of a tire vulcanizing apparatus 2 including a tire vulcanizing mold 1. The tire vulcanizing mold 1 and the tire vulcanizing apparatus 2 of this embodiment are used in a method for vulcanizing a green tire 3 (hereinafter, sometimes referred to as a "vulcanizing method") described below. The green tire 3 is a tire in an unvulcanized state. Furthermore, "unvulcanized" includes all states that have not reached complete vulcanization, and a so-called semi-vulcanized state is included in this "unvulcanized". For example, a pneumatic tire is used as the tire.

[0012] In addition, the tire vulcanizing mold 1 and the tire vulcanizing apparatus 2 of this embodiment heat and vulcanize the green tire 3 that is placed horizontally so that the tire axis 3s is oriented almost vertically. Here, "almost vertical" includes a range in which the angle of the tire axis 3s with respect to a vertical line (not shown) is 10 degrees or less.

[0013] [Tire vulcanizing equipment] The tire vulcanizing apparatus 2 is configured to include a tire vulcanizing mold 1 and a steam supply device 4. Furthermore, the tire vulcanizing apparatus 2 of this embodiment, like the conventional one, also includes a pressurized medium supply device 5, a vacuum device 6, a bladder 7, and a center mechanism 8. Note that in the tire vulcanizing apparatus 2, when so-called bladderless vulcanization is performed in which the raw tire 3 is vulcanized without using the bladder 7, the bladder 7 and the like can be omitted.

[0014] [Tire curing mold] Fig. 2 is a partially enlarged view of the tire vulcanizing mold 1. As shown in Figs. 1 and 2, the tire vulcanizing mold 1 of this embodiment is configured to include an upper side mold 11, a lower side mold 12, and a tread mold 13. Furthermore, the tire vulcanizing mold 1 of this embodiment is configured to include an upper bead ring 14 and a lower bead ring 15. The upper side mold 11, the lower side mold 12, the tread mold 13, the upper bead ring 14, and the lower bead ring 15 are fitted together to form a molding surface 16 for molding the outer surface of the green tire 3. The molding surface 16 of this embodiment includes an upper side molding surface 16a, a lower side molding surface 16b, a tread molding surface 16c, an upper bead molding surface 16d, and a lower bead molding surface 16e.

[0015] [Upper side mold / Lower side mold] 2, the upper side mold 11 has an upper side molding surface 16a. This upper side molding surface 16a is used to mold the upper sidewall portion 3a of the pair of sidewall portions 3a, 3b of the green tire 3 placed horizontally.

[0016] The lower side mold 12 has a lower side molding surface 16b. This lower side molding surface 16b is used to mold the lower sidewall portion 3b of the pair of sidewall portions 3a, 3b of the green tire 3 placed horizontally.

[0017] In this embodiment, the entire upper side mold 11 is formed of a first material 17a, and the entire lower side mold 12 is formed of a third material 17c. The thermal conductivity of the first material 17a is set lower than that of the third material 17c. This makes the thermal conductivity of the entire upper side mold 11 lower than that of the entire lower side mold 12. Furthermore, in this embodiment, the thermal conductivity of the material (i.e., first material) 17a forming the upper side molding surface 16a is set lower than that of the material (i.e., third material) 17c forming the lower side molding surface 16b. Details of the first material 17a and the third material 17c will be described later.

[0018] Note that, as long as the thermal conductivity of the upper side mold 11 as a whole is lower than the thermal conductivity of the lower side mold 12 as a whole, the present invention is not limited to an embodiment in which the entire upper side mold 11 is made of the first material 17a and the entire lower side mold 12 is made of the third material 17c. For example, a portion of the upper side mold 11 may be made of a material other than the first material 17a. Also, a portion of the lower side mold 12 may be made of a material other than the third material 17c.

[0019] [Tread mold] The tread mold 13 has a tread molding surface 16c. This tread molding surface 16c is used to mold the tread portion 3c of the green tire 3 placed horizontally. The tread mold 13 of this embodiment is configured to include a plurality of segments 19 and a plurality of sector shoes 20.

[0020] The plurality of segments 19 are divided in the circumferential direction of the tread molding surface 16c (the tire circumferential direction of the raw tire 3). The tread molding surface 16c is formed on the inner circumferential surfaces of these segments 19. The plurality of segments 19 may be formed, for example, from an aluminum-based material (aluminum, aluminum alloy, etc.) in consideration of the processability of the tread molding surface 16c, as in the conventional case.

[0021] The multiple sector shoes 20 are for replaceably holding the multiple segments 19. The multiple sector shoes 20 are formed, for example, from an iron-based material (iron, steel, etc.) in consideration of strength and cost, as in the past.

[0022] The multiple sector shoes 20 are movable inward and outward in the radial direction of the tire, for example, via guide means (not shown), as in the conventional case. As these sector shoes 20 move, the multiple segments 19 can move inward and outward in the radial direction of the tire. This allows the tread mold 13 to expand and contract in diameter.

[0023] [Upper bead ring / lower bead ring] The upper bead ring 14 has an upper bead molding surface 16d. This upper bead molding surface 16d is used to mold the upper bead portion 3d of the pair of bead portions 3d, 3e of the green tire 3 placed horizontally. The upper bead ring 14 of this embodiment is fixed to the upper side mold 11.

[0024] The lower bead ring 15 has a lower bead molding surface 16e. This lower bead molding surface 16e is used to mold the lower bead portion 3e of the pair of bead portions 3d, 3e of the green tire 3 placed horizontally. The lower bead ring 15 of this embodiment is fixed to the lower side mold 12.

[0025] The upper bead ring 14 and the lower bead ring 15 of this embodiment are formed of, for example, an iron-based material (iron, steel, etc.) in consideration of strength and cost, as in the conventional case.

[0026] [container] 1, the tire vulcanizing mold 1 of this embodiment is held by a container 21. The container 21 of this embodiment is formed, for example, from an iron-based material (iron, steel, etc.) in consideration of strength and cost, as in the conventional case.

[0027] The container 21 of this embodiment is configured to include an upper platen 22, a lower platen 23, and an actuator ring 24. The upper platen 22, the lower platen 23, and the actuator ring 24 have known structures.

[0028] The container 21 of this embodiment can expand the diameter of the tread mold 13 by raising the actuator ring 24. Furthermore, the container 21 can move the upper platen 22, the upper side mold 11, and the upper bead ring 14 upward. This allows the raw tire 3 to be placed horizontally inside the tire vulcanizing mold 1.

[0029] In addition, in the container 21 of this embodiment, the upper platen 22 and the upper side mold 11 are lowered together with the actuator ring 24. As a result, the tire vulcanizing mold 1 is closed (mold clamped).

[0030] [Heat source] The tire vulcanizing mold 1 of this embodiment includes a heat source 25. This heat source 25 is for heating the outer surface of the green tire 3 through the tire vulcanizing mold 1.

[0031] The heat source 25 is not particularly limited as long as it can heat the raw tire 3. In this embodiment, a known jacket to which a high-temperature thermal fluid such as steam is supplied is used as the heat source 25, but the heat source is not particularly limited and may be, for example, an electric heater. The thermal fluid is supplied by a thermal fluid supply means (not shown) such as a boiler. The temperature of the heat source can be set to, for example, 160 to 200°C.

[0032] The heat source 25 of this embodiment includes a first heat source 25a, a second heat source 25b, and a third heat source 25c. Note that the heat source 25 is not limited to this embodiment, and some of these may be omitted or other heat sources may be further added depending on the structure of the tire vulcanizing mold 1.

[0033] In this embodiment, the first heat source 25a, the second heat source 25b, and the third heat source 25c are connected to the same thermal fluid supply means (not shown), but this is not particularly limited. For example, the first heat source 25a, the second heat source 25b, and the third heat source 25c may be connected to different thermal fluid supply means.

[0034] The first heat source 25a is built into the actuator ring 24. As a result, heat from the first heat source 25a is transferred to the tread molding surface 16c via the sector shoe 20 and the segment 19. Therefore, the first heat source 25a can heat the outer surface of the tread portion 3c of the green tire 3 shown in FIG.

[0035] 1, the second heat source 25b is built into the upper platen 22. As a result, heat from the second heat source 25b is transferred to the upper side molding surface 16a and the upper bead molding surface 16d via the upper side mold 11 and the upper bead ring 14. Therefore, the second heat source 25b can heat the outer surfaces of the upper sidewall portion 3a and the upper bead portion 3d of the green tire 3 shown in FIG.

[0036] 1, the third heat source 25c is built into the lower platen 23. As a result, heat from the third heat source 25c is transferred to the lower side molding surface 16b and the lower bead molding surface 16e via the lower side mold 12 and the lower bead ring 15. Therefore, the third heat source 25c can heat the outer surfaces of the lower sidewall portion 3b and the lower bead portion 3e of the green tire 3 shown in FIG.

[0037] [Steam supply device] 1, the steam supplying device 4 is for indirectly or directly supplying steam to the inner cavity 3i of the green tire 3 in the tire vulcanizing mold 1. The steam in this embodiment is used to heat the inner surface of the green tire 3.

[0038] The steam supply device 4 of the present embodiment can be configured by a boiler, etc. Steam generated by the steam supply device 4 is supplied to the inner cavity 3i of the raw tire 3 via a supply / discharge passage 27 described later.

[0039] The temperature of the steam (temperature at the time of supply) can be set appropriately. The temperature of the steam in this embodiment can be set to 180 to 220°C (for example, 200°C), which is a temperature normally used in tire vulcanization. By supplying such high-temperature steam to the cavity 3i of the raw tire 3, the inner surface of the raw tire 3 can be heated.

[0040] [Pressurized medium supply device] The pressurized medium supply device 5 is for supplying a high-pressure pressurized medium. In this embodiment, after steam is supplied by the steam supply device 4, the pressurized medium is supplied from the pressurized medium supply device 5. The pressurized medium is composed of an inert gas or a mixed gas of an inert gas and steam. Nitrogen gas or the like is used as the inert gas.

[0041] [Vacuum device] The vacuum device 6 is for discharging the steam and pressurized medium supplied to the cavity 3i of the raw tire 3. The vacuum device 6 can be configured, for example, by a vacuum pump or the like.

[0042] [Bladder] The bladder 7 is used to press the green tire 3 against the tire vulcanizing mold 1. The bladder 7 of this embodiment is formed in a cylindrical shape and is open at an upper opening edge portion 7a and a lower opening edge portion 7b.

[0043] Bladder 7 can be made of a well-known elastic material such as rubber. Bladder 7 can be expanded and deformed by the supply of steam from steam supply device 4 and the supply of pressurized medium from pressurized medium supply device 5.

[0044] [Central mechanism] The central mechanism 8 is for holding the bladder 7. The central mechanism 8 of this embodiment includes a support cylinder 31 and a center shaft 32.

[0045] The support tube 31 stands upright and is concentric with the tire axis 3s. A disk-shaped lower clamp plate 33 is fixed to the upper end of the support tube 31. The lower clamp plate 33 holds the lower opening edge 7b of the bladder 7.

[0046] In this embodiment, a supply / discharge flow path 27 is provided inside the support cylinder 31. This supply / discharge flow path 27 is used to supply steam and a pressurized medium to the inside of the tire vulcanizing mold 1 and to discharge steam and the like from the inside of the tire vulcanizing mold 1.

[0047] In this embodiment, one end of the supply / discharge flow path 27 is connected to a steam supply device 4, a pressurized medium supply device 5, and a vacuum device 6. In this embodiment, a first switching valve 36 and a second switching valve 37 are capable of switching between supplying steam 26, supplying pressurized medium 28, and discharging steam 26 and pressurized medium 28.

[0048] The other end of the supply / discharge flow path 27 opens inside the tire vulcanizing mold 1 (inner cavity 3i of the raw tire 3). In this embodiment, the other end of the supply / discharge flow path 27 opens at the upper end side of the support cylinder 31.

[0049] The center shaft 32 is inserted into the center hole of the support cylinder 31 so as to be movable up and down. In this embodiment, a disk-shaped upper clamp plate 34 is fixed to the upper end of the center shaft 32. This upper clamp plate 34 holds the upper opening edge 7a of the bladder 7.

[0050] [Vulcanization method for raw tires] Next, a method for vulcanizing the raw tire 3 (hereinafter, sometimes referred to as the "vulcanization method") will be described. Fig. 3 is a flowchart showing an example of the processing procedure of the method for vulcanizing the raw tire.

[0051] As shown in Fig. 3, the vulcanization method of this embodiment includes a step S3 (hereinafter sometimes referred to as the "vulcanization step") of vulcanizing an unvulcanized raw tire 3 using the tire vulcanization mold 1 shown in Fig. 1. Furthermore, the vulcanization method of this embodiment includes, in addition to the vulcanization step S3, a loading step S1, a mold closing step S2, and a removal step S4.

[0052] [Feeding process] In the vulcanization method of the present embodiment, first, a loading step S1 is carried out. In the loading step S1 of the present embodiment, a raw tire 3 is loaded in a horizontally placed state into the tire vulcanization mold 1 shown in FIG. 1 based on the same procedure as in the conventional method.

[0053] In the loading step S1 of this embodiment, the actuator ring 24 is raised to expand the diameter of the tread mold 13. Furthermore, in the loading step S1, the upper platen 22, the upper side mold 11, and the upper bead ring 14 are moved upward. This causes the tire vulcanizing mold 1 to be opened, and the raw tire 3 can be loaded into the tire vulcanizing mold 1 in a horizontally placed state.

[0054] [Mold closing process] Next, in the vulcanization method of the present embodiment, a mold closing step S2 is carried out as shown in Fig. 3. In the mold closing step S2 of the present embodiment, the tire vulcanization mold 1 into which the green tire 3 has been charged is closed as shown in Fig. 1 based on the same procedure as in the conventional method.

[0055] In the mold closing step S2 of this embodiment, the upper platen 22 and the upper side mold 11 are lowered together with the actuator ring 24. As a result, the tire vulcanizing mold 1 is closed (mold clamped).

[0056] [Vulcanization process] Next, in the vulcanization method of the present embodiment, a vulcanization step S3 is carried out as shown in Fig. 3. In the vulcanization step S3 of the present embodiment, as in the conventional method, a green tire 3 is vulcanized using the tire vulcanization mold 1 shown in Fig. 1 and Fig. 2. Fig. 4 is a flowchart showing an example of the processing procedure of the vulcanization step S3.

[0057] The vulcanization step S3 of this embodiment includes an outer heating start step S31, an inner heating step S32, and a pressurizing step S33. In this embodiment, the pressurizing step S33 is carried out after the inner heating step S32 is carried out. The outer heating start step S31 and the inner heating step S32 may be started simultaneously. Fig. 5 is a cross-sectional view showing an example of a tire vulcanizing apparatus 2 carrying out the vulcanizing step S3.

[0058] [Outer heating start process] In the outside heating start step S31, heating of the outer surface of the green tire 3 is started using the heat source 25 provided in the tire vulcanizing mold 1 shown in Fig. 5. As described above, the heat source 25 in this embodiment includes the first heat source 25a, the second heat source 25b, and the third heat source 25c.

[0059] Heat H1 from the first heat source 25a is transferred to the tread molding surface 16c via the sector shoe 20 and the segment 19. Furthermore, heat H2 from the second heat source 25b is transferred to the upper side molding surface 16a and the upper bead molding surface 16d via the upper side mold 11 and the upper bead ring 14. Heat H3 from the third heat source 25c is transferred to the lower side molding surface 16b and the lower bead molding surface 16e via the lower side mold 12 and the lower bead ring 15. As a result, in the outer heating start step S31, the outer surface of the green tire 3 is heated via the molding surface 16.

[0060] [Inner heating process] In the inside heating step S32, the inner surface of the raw tire 3 is heated using the steam supplying device 4.

[0061] In the inside heating step S32 of this embodiment, first, the steam supplying device 4 is connected to the interior of the tire vulcanizing mold 1 (the cavity 3i of the green tire 3) via the first switching valve 36, the second switching valve 37, and the supply / discharge flow path 27. Then, steam 26 is supplied indirectly or directly to the cavity 3i of the green tire 3 by the steam supplying device 4. In this embodiment, the steam 26 is indirectly supplied to the cavity 3i of the green tire 3 via the bladder 7. As a result, the inner surface of the green tire 3 is heated.

[0062] [Pressure process] In the pressurizing step S33, the green tire 3 is pressed firmly against the molding surface 16 of the tire vulcanizing mold 1 using the pressurizing medium supply device 5. In this embodiment, the pressurizing step S33 is carried out after the inside heating step S32 is carried out.

[0063] In the pressurizing step S33 of this embodiment, the pressurizing medium supply device 5 is connected to the interior of the tire vulcanizing mold 1 (the cavity 3i of the green tire 3) via the first selector valve 36, the second selector valve 37, and the supply / discharge flow path 27. Then, the pressurizing medium supply device 5 indirectly or directly supplies a high-pressure pressurizing medium 28 to the cavity 3i of the green tire 3. In this embodiment, the pressurizing medium 28 is indirectly supplied to the cavity 3i of the green tire 3 via the bladder 7. As a result, the green tire 3 is pressed strongly against the molding surface 16 of the tire vulcanizing mold 1.

[0064] In the vulcanization step S3 of this embodiment, an outer heating start step S31, an inner heating step S32, and a pressurizing step S33 are performed, whereby the molding surface 16 of the tire vulcanization mold 1 and the outer surface of the green tire 3 are brought into direct contact with each other, and heat and pressure are applied to the green tire 3. In this way, the green tire 3 can be vulcanized and molded.

[0065] In the vulcanization step S3, part of the steam 26 supplied in the inner heating step S32 is cooled and condensed in the cavity 3i on the green tire 3 side. As a result, a drain 38 accumulates at the position of the lower sidewall portion 3b of the pair of sidewall portions 3a, 3b of the green tire 3. Due to this drain 38, the lower sidewall portion 3b has a lower temperature than the upper sidewall portion 3a, which tends to result in insufficient vulcanization. Therefore, since the lower sidewall portion 3b tends to be the rate-limiting portion of vulcanization, the vulcanization time may be set so as to prevent insufficient vulcanization of the lower sidewall portion 3b.

[0066] However, when the vulcanization time is set as described above, the upper sidewall portion 3a, which is not affected by the drain 38, may be over-vulcanized. Such over-vulcanization of the upper sidewall portion 3a may adversely affect tire quality, particularly the rolling resistance performance of the tire.

[0067] In the tire vulcanizing mold 1 of this embodiment, the thermal conductivity of the upper side mold 11 as a whole is set to be smaller than the thermal conductivity of the lower side mold 12 as a whole. This makes it possible for the upper side mold 11 to transfer heat H2 less easily to the green tire 3 than the lower side mold 12. Therefore, the tire vulcanizing mold 1 of this embodiment (vulcanization step S3) can prevent over-vulcanization of the upper sidewall portion 3a, even if the vulcanization time is set so that the lower sidewall portion 3b is not under-vulcanized. This allows for a uniform amount of vulcanization of the pair of sidewall portions 3a, 3b of the green tire 3. Furthermore, in this embodiment, the thermal conductivity of the first material 17a forming the upper side molding surface 16a is set to be smaller than the thermal conductivity of the third material 17c forming the lower side molding surface 16b, thereby effectively preventing over-vulcanization of the upper sidewall portion 3a molded with the first material 17a.

[0068] Furthermore, in this embodiment, since over-vulcanization of the upper sidewall portion 3a is prevented, there is no need to, for example, lower the temperature of the tire vulcanization mold 1 (heat source 25) compared to conventional methods to equalize the amount of vulcanization of the sidewall portions 3a, 3b of the green tire 3. Therefore, the vulcanization method (tire vulcanization mold 1) of this embodiment also makes it possible to shorten the vulcanization time. Also, since there is no need for, for example, complex temperature control of the second heat source 25b and the third heat source 25c to prevent insufficient vulcanization of the lower sidewall portion 3b and over-vulcanization of the upper sidewall portion 3a, the manufacturing costs of the tire vulcanization apparatus 2 can be reduced.

[0069] The thermal conductivity of the first material 17a (in this example, the material forming the upper side mold 11, including the upper side molding surface 16a) is preferably set to 20% to 60% of the thermal conductivity of the third material 17c (in this example, the material forming the lower side mold 12, including the lower side molding surface 16b). By setting the thermal conductivity of the first material 17a to 60% or less of the thermal conductivity of the third material 17c, the upper side mold 11 (upper side molding surface 16a) is less likely to transfer heat H2 to the green tire 3 than the lower side mold 12 (lower side molding surface 16b). This can prevent over-vulcanization of the upper sidewall portion 3a. On the other hand, by setting the thermal conductivity of the first material 17a to 20% or more of the thermal conductivity of the third material 17c, it can prevent the transfer of heat H2 from the upper side molding surface 16a to the green tire 3 (upper sidewall portion 3a) from becoming less than necessary. This can prevent insufficient vulcanization of the upper sidewall portion 3a. From this viewpoint, the thermal conductivity of the first material 17a is preferably 50% or less of the thermal conductivity of the third material 17c, and is preferably 30% or more of the thermal conductivity of the third material 17c.

[0070] The thermal conductivity of the first material 17a (in this example, the material forming the upper side mold 11 including the upper side molding surface 16a) is preferably set to 5 to 50 (W / m·K). Setting the thermal conductivity to 50 (W / m·K) or less reduces the transfer of heat H2 from the upper side mold 11 (upper side molding surface 16a) to the green tire 3, thereby preventing over-vulcanization of the upper sidewall portion 3a. On the other hand, setting the thermal conductivity to 5 (W / m·K) or more prevents the transfer of heat H2 from the upper side mold 11 (upper side molding surface 16a) to the green tire 3 from becoming less than necessary. This prevents the upper sidewall portion 3a from being under-vulcanized. From this perspective, the thermal conductivity of the first material 17a is preferably 40 (W / m·K) or less and preferably 10 (W / m·K) or more.

[0071] The first material 17a and the third material 17c are not particularly limited as long as the thermal conductivity of the first material 17a is lower than that of the third material 17c. In this embodiment, the first material 17a is stainless steel, and the third material 17c is iron. Stainless steel has a lower thermal conductivity than iron. Therefore, the thermal conductivity of the first material 17a is lower than that of the third material 17c, and over-vulcanization of the upper sidewall portion 3a can be prevented.

[0072] [Removal process] Next, in the vulcanization method of the present embodiment, a removal step S4 is carried out after the vulcanization step S3, as shown in Fig. 3. In the removal step S4 of the present embodiment, the vulcanized tire 40 is removed from the tire vulcanization mold 1 shown in Fig. 5, as in the conventional method.

[0073] In the removal step S4 of this embodiment, first, the vacuum device 6 is connected to the inside of the tire vulcanizing mold 1 (the cavity 3i of the vulcanized tire 40) via the first switching valve 36 and the supply / discharge flow path 27. Then, the steam 26 and the pressurized medium 28 supplied to the cavity 3i are discharged using the vacuum device 6.

[0074] Next, in the removal step S4 of this embodiment, the actuator ring 24 is raised to expand the diameter of the tread mold 13. Furthermore, in the removal step S4, the upper platen 22, the upper side mold 11, and the upper bead ring 14 are moved upward. This opens the tire vulcanizing mold 1. Then, the vulcanized tire 40 is removed from the tire vulcanizing mold 1. This allows the tire 40 to be manufactured.

[0075] As described above, in the vulcanization method of this embodiment, the green tire 3 is vulcanized using a tire vulcanization mold 1 in which the thermal conductivity of the first material (in this example, the material forming the upper side mold 11 including the upper side molding surface 16a) 17a is set to be lower than the thermal conductivity of the third material (in this example, the material forming the lower side mold 12 including the lower side molding surface 16b) 17c. This prevents over-vulcanization of the upper sidewall portion 3a, and ensures a uniform amount of vulcanization of the sidewall portions 3a, 3b of the green tire 3. Therefore, the vulcanization method can produce a tire 40 with good tire quality, particularly good rolling resistance performance.

[0076] Furthermore, in this embodiment, for example, it is not necessary to lower the temperature of the heat source 25 (e.g., the second heat source 25b and the third heat source 25c) of the tire vulcanizing mold 1 compared to conventional methods in order to equalize the amount of vulcanization of the sidewall portions 3a, 3b of the green tire 3. Therefore, the vulcanization method (tire vulcanizing mold 1) of this embodiment also makes it possible to shorten the vulcanization time.

[0077] [Tire vulcanization mold (second embodiment)] In the embodiments described above, the upper side mold 11 is made of only the first material 17a as shown in Fig. 2, but the present invention is not limited to this as long as the thermal conductivity of the upper side mold 11 as a whole is lower than the thermal conductivity of the lower side mold 12 as a whole. Fig. 6 is a cross-sectional view showing a tire vulcanizing mold 1 according to another embodiment of the present invention.

[0078] The upper side mold 11 of this embodiment includes a first portion 41 that forms the upper side molding surface 16a, and a second portion 42 that is overlapped on the first portion 41 so as to be located above the first portion 41. In this upper side mold 11, heat H2 from a second heat source 25b (shown in FIG. 5) is transferred to the green tire 3 via the second portion 42, the first portion 41, and the upper side molding surface 16a.

[0079] The first portion 41 is made of the first material 17a. On the other hand, the second portion 42 is made of the second material 17b. The thermal conductivity of the first material 17a is set to be smaller than the thermal conductivity of the second material 17b. This makes it more difficult for heat H2 transferred from the second heat source 25b (shown in FIG. 5) to be transferred to the green tire 3, compared to when the entire upper side mold 11 (the first portion 41 and the second portion 42) is made of the second material 17b. This prevents over-vulcanization of the upper sidewall portion 3a.

[0080] The thermal conductivity of the first material 17a (the material of the first portion 41) is preferably set to 20% to 60% of the thermal conductivity of the second material 17b (the material of the second portion 42). By setting the thermal conductivity of the first material 17a to 60% or less of the thermal conductivity of the second material 17b, it is possible to make it difficult for heat H2 transferred from the second heat source 25b (shown in FIG. 5) to the second portion 42 to be transferred to the green tire 3 via the first portion 41 and the upper side molding surface 16a. This can prevent over-vulcanization of the upper sidewall portion 3a. On the other hand, by setting the thermal conductivity of the first material 17a to 20% or more of the thermal conductivity of the second material 17b, it is possible to prevent heat H2 transferred from the second heat source 25b to the second portion 42 from being transferred to the green tire 3 via the first portion 41 and the upper side molding surface 16a more difficult than necessary. This can prevent insufficient vulcanization of the upper sidewall portion 3a. From this perspective, the thermal conductivity of the first material 17a is preferably 50% or less of the thermal conductivity of the second material 17b, and is preferably 30% or more of the thermal conductivity of the third material 17c.

[0081] Furthermore, the thermal conductivity of the first material 17a is preferably set to 5 to 50 (W / m·K), as in the previous embodiments.

[0082] The first material 17a and the second material 17b are not particularly limited as long as the thermal conductivity of the first material 17a is lower than that of the second material 17b. The first material 17a in this embodiment is stainless steel, as in the previous embodiments. Meanwhile, the second material 17b in this embodiment is iron. As described above, stainless steel has a lower thermal conductivity than iron. Therefore, the thermal conductivity of the first material 17a is lower than that of the second material 17b, which can prevent over-vulcanization of the upper sidewall portion 3a.

[0083] Furthermore, stainless steel is more expensive than iron. For this reason, the upper side mold 11 of this embodiment is composed of not only the first material 17a made of expensive stainless steel, but also the second material 17b made of relatively inexpensive iron. Therefore, the upper side mold 11 of this embodiment can be manufactured at a lower cost than, for example, an upper side mold 11 composed only of the first material 17a.

[0084] The volume of the first portion 41 is preferably set to 30% to 70% of the total volume of the upper side mold 11. Here, when the upper side mold 11 is composed of the first portion 41 and the second portion 42, the "total volume" is specified as the sum of the volumes of the first portion 41 and the second portion 42.

[0085] Setting the volume of the first portion 41 to 30% or more of the total volume of the upper side mold 11 makes it difficult for heat H2 transferred from the second heat source 25b (shown in FIG. 5) to the second portion 42 to be transferred to the green tire 3 via the first portion 41 and the upper side molding surface 16a. On the other hand, setting the volume of the first portion 41 to 70% or less of the total volume of the upper side mold 11 prevents the volume of the first material 17a, which is made of expensive stainless steel, from increasing, and can prevent an increase in the manufacturing cost of the upper side mold 11. From this perspective, the volume of the first portion 41 is preferably 40% or more of the total volume of the upper side mold 11, and preferably 60% or less of the total volume of the upper side mold 11.

[0086] [Tire vulcanization mold (third embodiment)] As shown in FIG. 2, in the tire vulcanization mold 1 of the previous embodiment, the upper bead ring 14 and the lower bead ring 15 are formed from the same material (iron-based material), but this is not limited to this. For example, if the lower bead portion 3e is the rate-limiting portion of vulcanization, as with the lower sidewall portion 3b, the thermal conductivity of the material forming the upper bead molding surface 16d may be set to be lower than the thermal conductivity of the material forming the lower bead molding surface 16e. As a result, as shown in FIG. 5, the upper bead molding surface 16d is less likely to transfer heat H2 to the green tire 3 than the lower bead molding surface 16e, thereby preventing over-vulcanization of the upper bead portion 3d shown in FIG. 2 and ultimately helping to suppress deterioration of tire performance.

[0087] The material forming the upper bead molding surface 16d is preferably the same as the first material 17a forming the upper side molding surface 16a (e.g., stainless steel), and the material forming the lower bead molding surface 16e is preferably the same as the second material 17b forming the lower side molding surface 16b (e.g., iron).

[0088] [Tire vulcanization mold (fourth embodiment)] The tire vulcanizing mold 1 in the embodiments described above includes an upper bead ring 14 and a lower bead ring 15 as shown in Fig. 2, but is not limited to this. For example, the upper bead ring 14 may be omitted, and the upper bead molding surface 16d may be formed on the upper side mold 11. Furthermore, the lower bead ring 15 may be omitted, and the lower bead molding surface 16e may be formed on the lower side mold 12. This simplifies the configuration of the tire vulcanizing mold 1, enabling the tire vulcanizing mold 1 to be manufactured at low cost.

[0089] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment and can be modified and implemented in various ways. [Example]

[0090] A process of vulcanizing a green tire using the tire vulcanization mold shown in Fig. 1 was simulated using a computer (Example). In the Example, a tire vulcanization mold model in which the tire vulcanization mold was modeled using a finite number of elements was input into the computer. Creation of this tire vulcanization mold model and simulation using the tire vulcanization mold model were performed based on conventional procedures (for example, the procedures described in JP 2018-122527 A).

[0091] The tire curing mold model includes an upper side mold model that models the upper side mold, a lower side mold model that models the lower side mold, and a tread mold model that models the tread mold.

[0092] In the example, the thermal conductivity of stainless steel was set for each element of the upper side mold model, and the thermal conductivity of iron was set for each element of the lower side mold model, so that the thermal conductivity of the entire upper side mold model including the upper side molding surface was set to be smaller than the thermal conductivity of the entire lower side mold model including the lower side molding surface.

[0093] In the example, the temperatures of the first heat source, the second heat source, and the third heat source were set based on the information in Table 1. Then, in the example, the vulcanization time and vulcanization amount ratio of the raw tire were obtained.

[0094] For comparison, a tire curing mold model in which the thermal conductivity of iron was set for each element of the upper side mold model of the example was input into a computer (Comparative Example). In this Comparative Example, the thermal conductivity of the entire upper side mold model was set to be the same as the thermal conductivity of the entire lower side mold model.

[0095] In the comparative example, the temperatures of the first, second, and third heat sources were set based on the information in Table 1. In this comparative example, the temperatures of the second and third heat sources were set lower than those of the examples in order to prevent over-vulcanization of the upper sidewall portion. In the comparative example, the vulcanization time and vulcanization ratio of the raw tire were obtained. The common specifications and test methods are as follows: <Common specifications> Stainless steel (SUS303): Thermal conductivity: 17 (W / m K) Iron (SS400): Thermal conductivity: 51 (W / m K) Tread mold model: Material: Aluminum alloy (A5052)

[0096] <Vulcanization time> The time required for each part of the tire to reach the required vulcanization amount was obtained through the above simulation. The results were expressed as an index, with the vulcanization time of the comparative example set at 100. The smaller the index, the shorter the vulcanization time and the better the productivity.

[0097] <Vulcanization ratio> The vulcanization amount Q1 of the upper sidewall and the vulcanization amount Q2 of the lower sidewall were obtained by the above simulation, and the ratio of these vulcanization amounts, or the vulcanization amount ratio (Q1 / Q2), was compared. The closer the vulcanization amount ratio (Q1 / Q2) is to 1, the more the over-vulcanization of the upper sidewall and the under-vulcanization of the lower sidewall are suppressed, and the more uniform the vulcanization is.

[0098] [Table 1]

[0099] As a result of the test, in the comparative example, by lowering the temperatures of the second and third heat sources, over-vulcanization of the upper sidewall portion was prevented, but compared to the examples, the vulcanization amount ratio (Q1 / Q2) deviated from 1. Therefore, in the examples, over-vulcanization and under-vulcanization of the sidewall portion were suppressed compared to the comparative example, and vulcanization was achieved uniformly.

[0100] Furthermore, in the examples, over-vulcanization of the upper sidewall portion was preferably prevented without lowering the temperatures of the second and third heat sources as in the comparative examples, thereby enabling the vulcanization time to be shortened.

[0101] [Note] The present invention includes the following aspects.

[0102] [Invention 1] A tire vulcanization mold for heating and vulcanizing a raw tire, an upper side mold having an upper side molding surface for molding an upper sidewall portion of a pair of sidewall portions of a green tire that is laid horizontally with the tire axis oriented substantially vertically; a lower side mold having a lower side molding surface for molding the lower sidewall portion of the pair of sidewall portions; a tread mold having a tread molding surface for molding a tread portion of the green tire, the thermal conductivity of the upper side mold as a whole is lower than the thermal conductivity of the lower side mold as a whole; Tire vulcanization mold. [Invention 2] A tire vulcanizing mold according to Invention 1, wherein the thermal conductivity of the material forming the upper side molding surface is lower than the thermal conductivity of the material forming the lower side molding surface. [Invention 3] 3. The tire vulcanizing mold according to claim 2, wherein the thermal conductivity of the material of the upper side molding surface is 5 to 50 (W / m·K). [Invention 4] the upper side mold includes a first portion made of a first material that forms the upper side molding surface, and a second portion made of a second material that is overlapped on the first portion so as to be positioned above the first portion, 4. The tire vulcanizing mold according to invention 2 or 3, wherein the thermal conductivity of the first material is lower than the thermal conductivity of the second material. [Invention 5] A tire vulcanizing mold according to invention 4, wherein the first material is stainless steel and the second material is iron. [Invention 6] A tire vulcanizing mold according to any one of the present inventions 1 to 5; a steam supplying device that indirectly or directly supplies steam to the cavity of the green tire in the tire vulcanizing mold, Tire vulcanizing equipment. [Invention 7] A method for manufacturing a tire vulcanizing mold for a tire according to any one of claims 1 to 5, comprising: A method for vulcanizing raw tires. [Explanation of symbols]

[0103] 1 Tire curing mold 3 Raw tires 3s Tire axis 11 Upper side mold 12 Lower side mold 13 Tread mold 16a Upper side molding surface 16b Lower side molding surface 16c tread molding surface

Claims

1. A tire vulcanization mold for heating and vulcanizing a raw tire, an upper side mold having an upper side molding surface for molding an upper sidewall portion of a pair of sidewall portions of a green tire that is laid horizontally with the tire axis oriented substantially vertically; a lower side mold having a lower side molding surface for molding the lower sidewall portion of the pair of sidewall portions; a tread mold having a tread molding surface for molding a tread portion of the green tire, the thermal conductivity of the upper side mold as a whole is lower than the thermal conductivity of the lower side mold as a whole; Tire vulcanization mold.

2. 2. The tire vulcanization mold according to claim 1, wherein the thermal conductivity of the material forming said upper side molding surface is lower than the thermal conductivity of the material forming said lower side molding surface.

3. 3. The tire vulcanizing mold according to claim 2, wherein the material of the upper side molding surface has a thermal conductivity of 5 to 50 (W / m·K).

4. the upper side mold includes a first portion made of a first material that forms the upper side molding surface, and a second portion made of a second material that is overlapped on the first portion so as to be positioned above the first portion, The tire vulcanizing mold according to claim 2 , wherein the thermal conductivity of the first material is lower than the thermal conductivity of the second material.

5. 5. The tire curing mold according to claim 4, wherein said first material is stainless steel and said second material is iron.

6. A tire vulcanizing mold according to any one of claims 1 to 5; a steam supplying device that indirectly or directly supplies steam to the cavity of the green tire in the tire vulcanizing mold, Tire vulcanizing equipment.

7. A method for producing a tire vulcanization mold according to claim 1, comprising the step of vulcanizing a green tire using the tire vulcanization mold according to any one of claims 1 to 5. A method for vulcanizing raw tires.

Images