Method for manufacturing solid tire

Abstract

To provide a method for manufacturing a solid tire 52 capable of improving the quality and productivity of the solid tire 52.SOLUTION: The method for manufacturing the solid tire 52 includes a step of preparing a green tire 68. The step of preparing green tire 68 includes a step of forming base portion 56. The step of molding the base portion 56 includes a first molding step of molding the first base main body 62 using the first base sheet 76 on the drum 72 on which the plurality of beads 66 are set. In an assembly 56A of the plurality of beads 66 and the first base body 62, two beads 66 located on the outermost side in the axial direction among the plurality of beads 66 are reference beads BB, and axial distances D from the respective reference beads BB to a side surface of the first base body 62 of the assembly 56A are equal to or less than 30mm.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a solid tire. [Background technology]

[0002] Solid tires have a solid structure. Solid tires do not require internal pressure adjustment and are puncture-resistant. Solid tires are used, for example, as tires for industrial vehicles such as forklifts. Solid tires are divided into two types: those with built-in beads and those without built-in beads. The built-in bead type is less productive than the non-built-in bead type. Regarding the built-in bead type, studies are being conducted to improve productivity. Patent Document 1 describes a manufacturing method that can suppress a decrease in productivity due to the incorporation of beads. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6686550 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a method for manufacturing a solid tire that can achieve improvements in the quality and productivity of solid tires. [Means for solving the problem]

[0005] The present invention provides a method for manufacturing a solid tire, the solid tire comprising a tread portion that contacts the road surface and a base portion located radially inward of the tread portion, the base portion comprising a base body and a plurality of beads embedded in the base body and arranged axially, the base body comprising a first base body and a second base body located radially inward of the first base body, the plurality of beads being located between the first base body and the second base body. The manufacturing method includes the steps of preparing a green tire for the solid tire and vulcanizing the green tire in a mold. The green tire preparation step includes the steps of molding the base portion and molding the tread portion. The base portion molding step includes a first molding step of molding the first base body using a first base sheet on a drum on which the plurality of beads are set, and a second molding step of molding the second base body by attaching a second base sheet to the inner circumferential surface of the assembly of the plurality of beads and the first base body obtained in the first molding step. In the assembly, the two axially outermost beads among the plurality of beads are reference beads, and the axial distance from each reference bead to the side of the first base body of the assembly is 30 mm or less. [Effects of the Invention]

[0006] According to the present invention, a method for manufacturing a solid tire can be obtained that can achieve improvements in the quality and productivity of solid tires. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view showing a portion of a conventional solid tire. [Figure 2] 1 is a cross-sectional view illustrating a method for manufacturing a solid tire. [Figure 3] FIG. 10 is a schematic diagram for explaining a preparation step. [Figure 4] FIG. 10 is a schematic diagram for explaining a preparation step. [Figure 5] FIG. 10 is a schematic diagram for explaining a preparation step. [Figure 6] FIG. 2 is a schematic diagram for explaining a vulcanization process. [Figure 7] 1 is a cross-sectional view showing a portion of a solid tire manufactured by a method for manufacturing a solid tire according to one embodiment of the present invention. [Figure 8] 1 is a cross-sectional view illustrating a method for manufacturing a solid tire according to an embodiment of the present invention. [Figure 9] FIG. 10 is a schematic diagram for explaining a preparation step. [Figure 10] FIG. 10 is a schematic diagram for explaining a preparation step. [Figure 11] FIG. 4 is a schematic diagram for explaining the arrangement of beads. [Figure 12] 10A and 10B are schematic diagrams for explaining the effect of changing the arrangement of beads. [Figure 13] 10A and 10B are schematic diagrams for explaining the effect of changing the material of the second base sheet. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, the present invention will be described in detail based on preferred embodiments, with appropriate reference to the drawings.

[0009] In the present invention, the crosslinked rubber refers to a crosslinked product of a rubber composition obtained by pressurizing and heating the rubber composition. The rubber composition is a material obtained by mixing a rubber component and chemicals in a kneader such as a Banbury mixer.

[0010] Examples of rubber components include natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene rubber (IR), ethylene propylene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), and butyl rubber (IIR). Examples of chemicals include reinforcing agents such as carbon black and silica, plasticizers such as aromatic oil, fillers such as zinc oxide, lubricants such as stearic acid, short fibers, antioxidants, processing aids, sulfur, and vulcanization accelerators. The selection of rubber components and chemicals, the content of the selected chemicals, etc. are determined appropriately depending on the specifications of the tire components to which the rubber composition is applied.

[0011] [Findings that form the basis of the present invention] Fig. 1 shows an example of a solid tire 2 (hereinafter referred to as tire 2) manufactured by a conventional manufacturing method. The dashed-dotted line EL represents the equatorial plane of the tire 2. The tire 2 includes a tread portion 4, a base portion 6, and a side portion 8. In the tire 2, the tread portion 4, the base portion 6, and the side portion 8 are integral with each other. The tread portion 4 forms a tread surface 10. The tread portion 4 comes into contact with the road surface at the tread surface 10. The tread portion 4 is made of cross-linked rubber in consideration of wear resistance and grip performance. Grooves 12 are cut into the tread portion 4. The base portion 6 is located radially inward of the tread portion 4. The base portion 6 includes a base body 14 and beads 16. The base body 14 is usually made of cross-linked rubber containing short fibers. The short fibers are made of organic fibers. Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers. The beads 16 are embedded in the base body 14. The beads 16 extend in the circumferential direction. Although not shown, the beads 16 include a steel wire wound in the circumferential direction. The base portion 6 of this tire 2 includes two beads 16. The two beads 16 are arranged side by side in the axial direction. The side portions 8 form side surfaces 18. The side portions 8 are made of soft crosslinked rubber. The tire 2 has a pair of side portions 8. Each side portion 8 is located axially outward of the tread portion 4 and the base portion 6.

[0012] As shown in FIG. 2, the tire 2 is obtained by vulcanizing a prepared green tire 20 in a mold 22 .

[0013] The mold 22 includes an upper mold 24 and a lower mold 26. The mold 22 is a two-piece mold. Although not described in detail, the upper mold 24 is movable up and down relative to the lower mold 26. A cavity surface 28 is formed by combining the upper mold 24 and the lower mold 26. The shape of the tire 2 is reflected in the cavity surface 28. The cavity surface 28 includes a tread forming portion 28t that forms the tread surface 10, a side surface forming portion 28s that forms the side surface 18, and a bottom forming portion 28b that forms the inner circumferential surface 2n of the tire 2.

[0014] In the vulcanization process, the raw tire 20 is placed in the mold 22 adjusted to a predetermined temperature. At this time, the upper mold 24 is moved upward relative to the lower mold 26, and the mold 22 is opened. After the raw tire 20 is placed, the upper mold 24 is moved downward, and the mold 22 is closed. As a result, the raw tire 20 comes into contact with the cavity surface 28. Specifically, the outer peripheral surface 20g of the raw tire 20 comes into contact with the tread forming portion 28t, the side surface 20s of the raw tire 20 comes into contact with the side surface forming portion 28s, and the inner peripheral surface 20n of the raw tire 20 comes into contact with the bottom forming portion 28b.

[0015] The raw tire 20 is pressurized and heated in the mold 22. By pressurizing and heating the raw tire 20 for a predetermined time, the rubber composition of the raw tire 20 is vulcanized, and a tire 2, which is a cross-linked product of the raw tire 20, is obtained.

[0016] The raw tire 20 is obtained by forming a base portion 6 by embedding beads 16 in a base body 14, and combining the tread portion 4 and side portions 8 with this base portion 6. In the preparation process of the green tire 20, as shown in FIG. 3, a portion of the base portion 6 is constructed using a molding machine 30. A fitting groove 34 is carved into the outer peripheral surface of a drum 32 of the molding machine 30. The beads 16 are set in this fitting groove 34. A base sheet 36 made of a rubber composition for the base portion 6 is wound around the base body 14 to form a portion of the base body 14 (hereinafter referred to as the first base body 14A). This results in an assembly of the beads 16 and the first base body 14A (hereinafter referred to as the first base portion 6A). The first base portion 6A is removed from the drum 32. As shown in FIG. 4, a base sheet 36 is further attached to the inner peripheral surface of the first base portion 6A to form a second base body 14B, which is another portion of the base body 14. This forms an unvulcanized base portion 6 having the beads 16 built into the base body 14. Then, the tread portion 4 is molded on the outer peripheral surface of the base portion 6, thereby forming an assembly of the tread portion 4 and the base portion 6. Side portions 8 are attached to both sides of this assembly, and an unvulcanized tire 2, that is, a green tire 20, is obtained as shown in FIG.

[0017] Air is likely to be trapped between the bead 16 and the base body 14. In the vulcanization process, when the raw tire 20 is placed in the mold 22, a bumping process is performed in which the mold 22 is repeatedly opened and closed to expel air contained in the raw tire 20. In order to promote the expulsion of air by the bumping process, a preheating process is sometimes performed on the base portion 6, which is an intermediate product, or the raw tire 20 before the vulcanization process. The preheating is performed at a temperature at which the vulcanization of the rubber composition does not proceed.

[0018] When carrying out the preheating treatment, the present inventors confirmed the influence of preheating on the base portion 6. As a result, it was found that the influence of preheating on the base portion 6 not only increased the flexibility of the rubber composition of the base portion 6, which was an expected phenomenon, but also caused the base portion 6 to deform so that its inner diameter became smaller, which was an unexpected phenomenon. In the areas where the beads 16 are provided, the beads 16 hinder the flow of the rubber composition. This prevents the inner diameter from being reduced. However, the inner diameter is reduced in the areas between adjacent beads 16 and in the axially outer portions of the beads 16 closest to the side surfaces 18. The change in the inner diameter in the axially outer portions is particularly large, and as shown in FIG. 6 , the base portion 6 is deformed so that the inner end KP of the green tire 20 protrudes radially inward. Therefore, if no countermeasures are taken, when the green tire 20 is inserted into the mold 22, the inner end KP may climb onto the lower mold 26 before the green tire 20 is seated therein, preventing the green tire 20 from being properly set on the lower mold 26. In this case, production of the tire 2 must be stopped and recovery measures must be implemented.

[0019] Increasing the inner diameter of the bead 16, that is, moving the radial position of the bead 16 outward, would create a space between the inner circumferential surface 20n of the green tire 20 and the bottom-forming portion 28b of the cavity surface 28, potentially preventing the inner end KP from climbing up. However, as described above, the green tire 20 is pressurized and heated in the mold 22 during the vulcanization process. This causes the rubber composition of the green tire 20 to flow. If there is a space between the inner circumferential surface 20n of the green tire 20 and the bottom-forming portion 28b of the cavity surface 28, the bead 16 may move along with the flow of the rubber composition, potentially causing a disturbance in the position of the bead 16. Moving the radial position of the bead 16 outward to prevent the inner end KP from climbing up would affect the quality of the tire 2.

[0020] Conventional manufacturing methods have room for improvement in terms of quality and productivity. To improve the quality and productivity of solid tires, a technology is needed that can set a green tire in a mold in the correct condition and at the correct position. Therefore, the present inventors have conducted extensive research to establish a method for manufacturing a solid tire that can achieve improvements in the quality and productivity of solid tires, and have completed the present invention, which will be described below.

[0021] [Outline of the embodiment of the present invention] The present invention provides a method for manufacturing a solid tire comprising a tread portion that contacts a road surface and a base portion located radially inward of the tread portion, the base portion comprising a base body and a plurality of beads embedded in the base body and aligned in the axial direction, the base body comprising a first base body and a second base body located radially inward of the first base body, the plurality of beads being located between the first base body and the second base body, the method comprising the steps of: preparing a green tire for the solid tire; and vulcanizing the green tire in a mold, the green tire preparation step comprising: molding the base portion; and vulcanizing the green tire in a mold to form the tread portion. and a molding process for molding the base portion, the molding process for the base portion including a first molding process for molding the first base body using a first base sheet on a drum on which a plurality of the beads are set, and a second molding process for molding the second base body by attaching a second base sheet to the inner surface of the assembly of the plurality of beads and the first base body obtained in the first molding process, wherein in the assembly, the two beads located axially outermost among the plurality of beads are reference beads, and the axial distance from each of the reference beads to the side of the first base body of the assembly is 30 mm or less.

[0022] The method for manufacturing a solid tire of the present invention can achieve improvements in the quality and productivity of solid tires. The mechanism by which this effect is achieved has not been clarified, but is presumed to be as follows.

[0023] In an assembly of multiple beads and a first base body, the axial distance from the reference bead to the side surface of the first base body of the assembly, which exceeded 30 mm in conventional manufacturing methods, is set to 30 mm or less. In this manufacturing method, the reference bead is positioned closer to the side surface of the base portion than in conventional manufacturing methods. Because the volume of the axially outer portion of the reference bead is reduced, even if the flexibility of the rubber composition is increased, for example, by performing a preheating process, radial inward protrusion of the inner end of the green tire is suppressed. The risk of the inner end of the green tire riding up on the mold is reduced. Since the green tire can be set in the mold in the correct position in the correct condition, the quality and productivity of solid tires are improved. Since there is no need to move the radial position of the bead outward to prevent the inner end from climbing up, disturbance in the position of the bead in the solid tire is also suppressed. This method for manufacturing a solid tire can achieve improvements in the quality and productivity of solid tires.

[0024] Preferably, the method further includes a size determination step of determining the size of the second base sheet based on the positions of the plurality of beads in the solid tire. In this case, it is possible to set the size of the second base sheet so as to reduce the space between the inner circumferential surface of the green tire and the mold. Since changes due to flow of the rubber composition are suppressed, a solid tire with stable quality as a whole can be obtained. This solid tire manufacturing method can further improve the quality and productivity of solid tires.

[0025] As described above, in this manufacturing method, the reference bead is positioned closer to the side of the base portion than in conventional manufacturing methods. Because the area where the second base sheet can contact the first base body is smaller axially outside the reference bead, there is a risk that the edge of the second base sheet may not be able to be tightly attached to the first base body. If the green tire is placed in the mold with the edge of the second base sheet peeled off from the first base body, it is expected that the edge of the second base sheet will interfere with the mold. This interference will prevent the green tire from being set in the mold in the correct condition. Therefore, the following points are preferably taken into consideration in this manufacturing method.

[0026] Preferably, the second base sheet has high adhesion to the first base sheet. As a result, even if the area where the second base sheet can contact the first base body is small, when the second base sheet contacts the first base body, the second base sheet adheres to the first base body. Since the green tire is placed into the mold with the end of the second base sheet in close contact with the first base body, the end of the second base sheet does not interfere with the mold, and the green tire is set in the mold in the correct state. This solid tire manufacturing method can further improve the quality and productivity of solid tires.

[0027] Preferably, in the vulcanization step, the green tire having the preheated base portion is placed in the mold. In this case, air present in the green tire is sufficiently expelled in the vulcanization step. This manufacturing method can stably manufacture high-quality tires. This manufacturing method can further improve tire quality and productivity.

[0028] Thus, the present invention provides a method for manufacturing a solid tire that can achieve improved quality and productivity of the solid tire, as will be described in detail below.

[0029] [Details of the embodiment of the present invention] 7 shows a portion of a solid tire 52 (hereinafter referred to as tire 52) manufactured by a manufacturing method according to one embodiment of the present invention. The tire 52 is mounted on an industrial vehicle such as a forklift. The tire 52 is mounted on a rim R. The tire 52 is also called a pneumatic cushion tire. The rim R is a regular rim.

[0030] A genuine rim is a rim specified in the standard on which the tire is based. The "standard rim" in the JATMA standard, the "design rim" in the TRA standard, and the "measuring rim" in the ETRTO standard are all genuine rims.

[0031] 7 shows a portion of a cross section (hereinafter referred to as a meridian cross section) of the tire 52 taken along a plane including the rotation axis of the tire 52. The direction indicated by the double arrow AD is the axial direction of the tire 52. The axial direction of the tire 52 means the direction parallel to the rotation axis of the tire 52. The direction indicated by the double arrow RD is the radial direction of the tire 52. The direction perpendicular to the plane of the paper is the circumferential direction of the tire 52.

[0032] In the axial direction, the direction away from the equatorial plane is the axially outer side of the tire 52, and the direction approaching the equatorial plane is the axially inner side of the tire 52. The direction indicated by arrow RD1 is the radially outer side of the tire 52, and the direction indicated by arrow RD2 is the radially inner side of the tire 52.

[0033] The tire 52 includes a tread portion 54, a base portion 56, and a pair of side portions 58. The tread portion 54 comes into contact with the road surface. The base portion 56 is located radially inward of the tread portion 54. The pair of side portions 58 are located axially outward of the tread portion 54 and the base portion 56, respectively. The tread portion 54 and the side portions 58 have the same configuration as the tread portion 4 and the side portions 8 of the tire 2 shown in FIG. 1. A description of the tread portion 54 and the side portions 58 will be omitted.

[0034] The base portion 56 includes a base body 60. The base body 60 is made of cross-linked rubber. The base body 60 includes a first base body 62 and a second base body 64. The second base body 64 is located radially inside the first base body 62. The first base body 62 and the second base body 64 are integral with each other.

[0035] The first base body 62 and the second base body 64 are each made of cross-linked rubber. The second base body 64 may be made of the same cross-linked rubber as the first base body 62, or the second base body 64 may be made of a different cross-linked rubber from the cross-linked rubber of the first base body 62.

[0036] The first base body 62 includes short fibers. The short fibers are made of organic fibers. Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers. The crosslinked rubber of the second base body 64 of this tire 52 is the same as the crosslinked rubber of the first base body 62. The second base body 64 also contains the same short fibers as the short fibers of the first base body 62.

[0037] The base portion 56 further includes a plurality of beads 66 aligned in the axial direction. The plurality of beads 66 are arranged symmetrically with respect to the equatorial plane. The base portion 56 of this tire 52 includes two beads 66. The base portion 56 may include three or more beads 66. The number of beads 66 included in the base portion 56 is determined appropriately, taking into consideration the specifications of the tire 52. The configuration of the beads 66 is the same as the configuration of the beads 16 of the tire 2 shown in FIG. 1.

[0038] Two beads 66 provided on the base portion 56 of this tire 52 are embedded in the base body 60. As shown in FIG. 7, the two beads 66 are located between the first base body 62 and the second base body 64.

[0039] In the present invention, among a plurality of beads aligned in the axial direction, the two beads positioned at the outermost positions in the axial direction are called reference beads. As described above, two beads 66 are embedded in the base body 60 of the tire 2. Therefore, each of the two beads 66 is a reference bead BB.

[0040] Next, a description will be given of a method for manufacturing this tire 52. This tire 52 is also manufactured in the same manner as the tire 2 shown in Fig. 1. The mold used to manufacture this tire 52 is the same as the mold 22 used to manufacture the tire 2 shown in Fig. 1. This tire 52 is obtained by vulcanizing a prepared green tire 68 in a mold 22 as shown in FIG. The manufacturing method includes the steps of providing a green tire 68 for tire 52 and vulcanizing green tire 68 in mold 22 .

[0041] Like the raw tire 20 of the tire 2, the raw tire 68 of the tire 52 is obtained by embedding beads 66 in a base body 60 to form a base portion 56, and combining the tread portion 54 and side portions 58 with the base portion 56.

[0042] In the preparation process for the green tire 68, first, the unvulcanized base portion 56 is molded. Then, the unvulcanized tread portion 54 is molded on the outer peripheral surface 56g of this base portion 56. In this way, an assembly of the tread portion 54 and the base portion 56 is obtained. Then, unvulcanized side portions 58 are molded on both side surfaces of this assembly. In this way, the green tire 68 is obtained. This preparation process includes a step of molding the base portion 56, a step of molding the tread portion 54, and a step of molding the side portions 58.

[0043] As described above, the beads 66 are embedded in the base body 60 of the base portion 56. To embed the beads 66, an assembly of the beads 66 and the first base body 62 (hereinafter referred to as the first base portion 56A) is molded using a molding machine 70, similar to the molding process of the base portion 6 of the tire 2 shown in Fig. 1. Then, the second base body 64 is molded on the inner circumferential surface of the first base portion 56A.

[0044] As shown in FIG. 9 , a molding machine 70 used to mold the first base portion 56A has a drum 72 with a mating groove 74 engraved on its outer circumferential surface. Beads 66 are set in the mating grooves 74 of the drum 72. Two beads 66 are embedded in the base body 60 of the tire 52. Two mating grooves 74 are engraved on the outer circumferential surface of the drum 72, and two beads 66 are set in each mating groove 74. After the beads 66 are set in the mating grooves 74, a first base sheet 76 made of a rubber composition for the first base body 62 is wound around the drum 72 to form the first base body 62. This results in the first base portion 56A, which is an assembly of the two beads 66 and the first base body 62. The first base portion 56A is removed from the drum 72. Then, as shown in FIG. 10 , a second base sheet 78 made of a rubber composition for the second base body 64 is further attached to the inner circumferential surface of the first base portion 56A. As a result, the second base body 64 is formed radially inside the first base portion 56A, and the base portion 56 having the two beads 66 embedded in the base body 60 is obtained.

[0045] The molding process of the base portion 56 includes a first molding process in which a first base body 62 is molded using a first base sheet 76 on a drum 72 on which a plurality of beads 66 are set, and a second molding process in which a second base body 64 is molded by attaching a second base sheet 78 to the inner surface of the assembly of the plurality of beads 66 and the first base body 62 obtained in the first molding process. The base portion 56 thus obtained is combined with the tread portion 54 and the side portion 58 to obtain a green tire 68 for the tire 52. In the vulcanization step, the green tire 68 is pressurized and heated in the mold 22, whereby the rubber composition of the green tire 68 is vulcanized, and the tire 52 shown in FIG. 7 is obtained. There are no particular limitations on the vulcanization conditions, such as temperature, pressure, and time, for vulcanizing and molding the green tire 68 in the mold 22, and general vulcanization conditions may be used.

[0046] Fig. 11 is a schematic diagram for explaining the arrangement of the beads 66 in the first base portion 56A. The length indicated by the double-headed arrow D in Fig. 11 is the axial distance from the reference bead BB to the side surface of the first base body 62 of the first base portion 56A (i.e., the assembly of the plurality of beads 66 and the first base body 62). In Fig. 11, the two-dot chain ellipse indicated by the symbol CB represents the bead 16 in the conventional manufacturing method. The axial distance D is expressed as the axial distance from the reference point BP, which is the center of the reference bead BB, to the side surface of the first base body 62. The center of the circumscribing circle of the reference bead BB is used as the center of the reference bead BB.

[0047] In this manufacturing method, in the first base portion 56A obtained in the first molding step, the axial distance D from the reference bead BB to the side surface 62s of the first base body 62 is 30 mm or less.

[0048] In the conventional manufacturing method, the axial distance D from the reference bead BB to the side surface of the first base body 62 of the first base portion 56A exceeded 30 mm. In this manufacturing method, the reference bead BB is thereby positioned closer to the side surface of the base portion 56 than in the conventional manufacturing method. Because the volume of the axially outer portion of the reference bead BB is reduced, even if the flexibility of the rubber composition is increased, for example, by performing a preheating process, the radially inward protrusion of the inner end portion of the green tire 68 is suppressed. The risk of the inner end portion of the green tire 68 riding up on the mold is reduced. Because the green tire 68 can be set in the mold in the appropriate position in the appropriate condition, the quality and productivity of the tire 2 are improved. Since there is no need to move the radial position of the bead 66 outward to prevent the inner end from riding up, the occurrence of disturbance in the position of the bead 66 in the tire 2 is also suppressed. This method for manufacturing the tire 2 can achieve improvements in the quality and productivity of the tire 2.

[0049] This manufacturing method allows the green tire 68 to be set in the mold 22 in an appropriate position in an appropriate state, so the radial positions of the beads 66 in the green tire 68 can be set according to the specifications of the tire 52 to be manufactured. For example, by adjusting the thickness of the second base sheet 78, it is possible to control the space created between the inner circumferential surface 68n of the green tire 68 and the bottom-forming portion 28b of the cavity surface 28 of the mold 22. In other words, it is possible to set the size of the second base sheet 78 so as to reduce the space created between the inner circumferential surface 68n of the green tire 68 and the mold 22. Since changes due to the flow of the rubber composition are suppressed, a solid tire 52 with stable quality as a whole can be obtained. This manufacturing method for a solid tire 52 can further improve the quality and productivity of the solid tire 52. From this perspective, this manufacturing method preferably further includes a size determination step of determining the size of the second base sheet 78 based on the positions of the plurality of beads 66 in the solid tire 52.

[0050] As described above, in this manufacturing method, the reference bead BB is positioned closer to the side surface of the base body 60 than in conventional manufacturing methods. Because the area in which the second base sheet 78 can contact the first base body 62 is smaller axially outward of the reference bead BB, the end 78e of the second base sheet 78 cannot be brought into close contact with the first base body 62, and there is a risk that the end 78e of the second base sheet 78 will peel off from the first base body 62. As shown in FIG. 12 , if the green tire 68 is placed in the mold 22 with the end 78e of the second base sheet 78 peeled off from the first base body 62, it is expected that the end 78e of the second base sheet 78 will interfere with the mold 22. This interference will prevent the green tire 68 from being properly set in the mold 22.

[0051] In this manufacturing method, in the first base portion 56A obtained in the first molding step, the axial distance D from the reference bead BB to the side surface 62s of the first base body 62 is preferably 10 mm or more. This ensures that an area for closely contacting the end 78e of the second base sheet 78 with the first base body 62 is secured axially outward from the reference bead BB. This promotes close contact of the second base sheet 78 with the first base body 62, and suppresses peeling of the end 78e of the second base sheet 78 from the first base body 62. From this viewpoint, it is more preferable that the axial distance D be 15 mm or more.

[0052] In this manufacturing method, the adhesion of the second base sheet 78 is preferably taken into consideration. Specifically, the second base sheet 78 is preferably configured to have high adhesion to the first base sheet 76. In other words, the second base sheet 78 preferably has high adhesion to the first base sheet 76. As a result, even if the area where the second base sheet 78 can contact the first base main body 62 is small, when the second base sheet 78 contacts the first base main body 62, the second base sheet 78 can effectively adhere to the first base main body 62. As shown in FIG. 13 , the green tire 68 is loaded into the mold 22 with the end portion 78e of the second base sheet 78 in close contact with the first base main body 62. Therefore, the end portion 78e of the second base sheet 78 does not interfere with the mold 22, and the green tire 68 is set in the mold 22 in an appropriate state. This manufacturing method for a solid tire 52 can further improve the quality and productivity of solid tires 52. From this viewpoint, it is more preferable that the axial distance D is 10 mm or more, and the second base sheet 78 has high adhesion to the first base sheet 76 .

[0053] In the present invention, the second base sheet 78 having high adhesion to the first base sheet 76 means that when the second base sheet 78 is brought into contact and pressed against the first base sheet 76, the two adhere to each other to the extent that the second base sheet 78 cannot be peeled off from the first base sheet 76 without changing the shape of the second base sheet 78.

[0054] As described above, the cross-linked rubber of the second base body 64 of this tire 52 is the same as the cross-linked rubber of the first base body 62, and the second base body 64 also contains the same short fibers as the short fibers of the first base body 62. The first base sheet 76 and the second base sheet 78 are made of a rubber composition in which short fibers are mixed with a rubber component.

[0055] The short fibers reduce the adhesiveness of the rubber. The inclusion of short fibers increases the risk that the end portion 78e of the second base sheet 78 will peel off from the first base body 62 in the green tire 68.

[0056] The smaller the amount of short fibers contained in the rubber composition, the better the adhesion of the rubber. From the viewpoint that the second base sheet 78 can be sufficiently adhered to the first base body 62 when it comes into contact with the first base body 62 even if the area where the second base sheet 78 can come into contact with the first base body 62 is small, it is preferable that the first base sheet 76 and the second base sheet 78 are made of different rubber compositions, and that the content of short fibers in the rubber composition of the second base sheet 78 is lower than the content of short fibers in the rubber composition of the first base sheet 76.

[0057] From the viewpoint of effectively improving the adhesion of the second base sheet 78, the rubber composition of the second base sheet 78 contains a rubber component and short fibers, and the content of the short fibers in the rubber composition of the second base sheet 78 is preferably 50 parts by mass or less, and more preferably 30 parts by mass or less, per 100 parts by mass of the rubber component. It is particularly preferable that the content of the short fibers in the rubber composition of the second base sheet 78 is 0 parts by mass per 100 parts by mass of the rubber component. In other words, it is particularly preferable that the rubber composition of the second base sheet 78 does not contain short fibers.

[0058] In this manufacturing method, it is preferable that a green tire 68 having a preheated base portion 56 is placed in the mold 22 in the vulcanization step. This allows air present in the green tire 68 to be sufficiently expelled in the vulcanization step. This manufacturing method can stably manufacture a high-quality tire 2. This manufacturing method can further improve the quality and productivity of the tire 2. In this case, from the viewpoint of being able to preheat the base portion 56 without advancing the vulcanization of the rubber composition, it is preferable that the preheat temperature of the base portion 56 be 85°C or higher and 90°C or lower.

[0059] In this manufacturing method, the raw tire 68 may be left standing in a preheating chamber (not shown) adjusted to a predetermined temperature to preheat the entire raw tire 68, and the preheated raw tire 68 may be placed in the mold 22 to undergo the vulcanization process. The raw tire 68 may be formed by attaching the side portions 58 to an assembly of the base portion 56 and the tread portion 54 obtained by molding the tread portion 54 while preheating the base portion 56, and then the formed raw tire 68 may be placed directly in the mold 22 to undergo the vulcanization process.

[0060] As is clear from the above description, the present invention provides a method for manufacturing a solid tire that can achieve improvements in the quality and productivity of solid tires. [Industrial Applicability]

[0061] The techniques described above that can achieve improvements in the quality and productivity of solid tires can be applied to various solid tire manufacturing methods.

[0062] [Note] The present invention includes the following aspects.

[0063] [1] A method for manufacturing a solid tire comprising a tread portion in contact with a road surface and a base portion located radially inward of the tread portion, the base portion comprising a base body and a plurality of beads embedded in the base body and arranged in an axial direction, the base body comprising a first base body and a second base body located radially inward of the first base body, the plurality of beads being located between the first base body and the second base body, the method comprising: preparing a green tire for the solid tire; and vulcanizing the green tire in a mold. a second molding step of molding the second base body by attaching a second base sheet to an inner peripheral surface of an assembly of the plurality of beads and the first base body obtained in the first molding step, wherein the two beads positioned axially outermost among the plurality of beads in the assembly are reference beads, and the axial distance from each of the reference beads to a side surface of the first base body of the assembly is 30 mm or less. [2] The method for manufacturing a solid tire according to the above-mentioned [1], further comprising a size determination step of determining the size of the second base sheet based on the positions of the plurality of beads in the solid tire. [3] The method for manufacturing a solid tire according to the above [1] or [2], wherein the second base sheet has high adhesion to the first base sheet. [4] The method for manufacturing a solid tire according to any one of [1] to [3] above, wherein in the vulcanization step, the raw tire having the preheated base portion is placed into the mold. [Explanation of symbols]

[0064] 2.52···Solid tire (tire) 4, 54 Tread section 6, 6A, 56, 56A... Base 10. Tread surface 14, 60... Base body 14A···First base body 14B Second base body 16, 66... ​​beads 20, 68... Raw tires 22. Mold 24...upper mold 26...lower mold 36···Base sheet 62 First base body 62s: Side surface of the first base body 62 64 Second base body 70...Molding machine 72...Drums 74···Mating groove 76 First base sheet 78 Second base sheet 78e End of second base sheet 78

Claims

1. A method for manufacturing a solid tire comprising: a tread portion in contact with a road surface; and a base portion located radially inward of the tread portion; the base portion comprising a base body and a plurality of beads embedded in the base body and aligned in an axial direction; the base body comprising a first base body and a second base body located radially inward of the first base body; and the plurality of beads located between the first base body and the second base body, providing a green tire for the solid tire; vulcanizing the green tire in a mold; Including, The raw tire preparation step includes: molding the base portion; and forming the tread portion, The base portion molding step includes: a first molding step of molding the first base body using a first base sheet on a drum on which a plurality of the beads are set; a second molding step of attaching a second base sheet to an inner peripheral surface of the assembly of the plurality of beads and the first base body obtained in the first molding step to mold the second base body, In the assembly, two beads located axially outermost among the plurality of beads are reference beads, an axial distance from each of the reference beads to a side surface of the first base body of the assembly is 30 mm or less; A method for manufacturing solid tires.

2. a size determining step of determining a size of the second base sheet based on positions of the plurality of beads in the solid tire, The method for manufacturing the solid tire according to claim 1.

3. the second base sheet has high adhesion to the first base sheet; The method for manufacturing the solid tire according to claim 1.

4. In the vulcanization step, the green tire having the preheated base portion is placed into the mold. A method for manufacturing a solid tire according to any one of claims 1 to 3.

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