Tire manufacturing method

Abstract

To provide a tire manufacturing method for obtaining a tire in which a sipe width is difficult to change.SOLUTION: There is provided a tire manufacturing method that is for obtaining a tire 10 comprising a tire body section 11 and a tread rubber section 12. The method comprises: a base tire preparation step S101 of preparing a base tire 1 which is a tire body section of a used tire and which becomes the tire body section 11; a molded tire assembly step S102 of assembling a molded tire 4 by attaching a tread rubber 2 that becomes the tread rubber section 12 to an outer circumferential side of the prepared base tire 1; a molded tire vulcanization step S103 of vulcanizing the assembled molded tire 4; and a sipe formation step S104 of forming a sipe 16 on a tread surface 5 of the vulcanized molded tire 4.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] BACKGROUND ART It has been known in the past to form sipes (thin cuts) on the tread surface of a vulcanized tire using a knife or the like (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 60-240507 Summary of the Invention [Problem to be solved by the invention]

[0004] However, it has been found that when sipes are formed on a new tire, the sipe width widens as the tire diameter grows during driving, which can result in the sipes not being able to fully demonstrate their effectiveness, such as improving wear resistance, or can make the bottom of the sipes more susceptible to cracks.

[0005] Therefore, an object of the present invention is to provide a tire manufacturing method for obtaining a tire in which the sipe width is less likely to change. [Means for solving the problem]

[0006] The above problems can be solved by the following means.

[0007] (1) The method for manufacturing a tire of the present invention comprises: A tire manufacturing method for obtaining a tire having a tire main body portion and a tread rubber portion, comprising: a tire casing preparation step of preparing a tire casing that is a tire main body portion of a used tire and that will become the tire main body portion; a molded tire assembling process for assembling a molded tire by attaching tread rubber that becomes the tread rubber portion to an outer peripheral side of the prepared base tire; a molded tire vulcanization step of vulcanizing the assembled molded tire; a sipe forming step of forming sipes on a tread surface of the vulcanized molded tire; The present invention is characterized by having the following. According to the tire manufacturing method of the present invention, a tire in which the sipe width is less likely to change can be obtained.

[0008] (2) In the tire manufacturing method described in (1) above, In the molded tire assembling step, the vulcanized tread rubber may be wound and attached to the outer peripheral surface of the base tire via an unvulcanized cushion rubber. In this case, tires can be manufactured on a compact line.

[0009] (3) In the tire manufacturing method described in (1) above, In the molded tire assembling step, the unvulcanized tread rubber may be wound and attached to an outer peripheral surface of the base tire. In this case, the appearance of the manufactured tire tends to be better.

[0010] (4) In any one of the tire manufacturing methods (1) to (3) above, In the sipe forming step, it is preferable that the sipes are formed so as to avoid joint portions in the tire circumferential direction of the tread rubber of the molded tire. In this case, failures caused by sipes are less likely to occur.

[0011] (5) In any one of the tire manufacturing methods (1) to (4) above, In the sipe forming step, it is preferable that the sipes are formed linearly in a direction inclined with respect to the circumferential direction of the tire molded tire. In this case, the formation of the sipes becomes easier.

[0012] (6) In any one of the tire manufacturing methods (1) to (5) above, In the sipe forming step, it is preferable that the sipes are formed so that the depth of the sipes increases toward the center of the molded tire in the tire width direction. In this case, the formation of the sipes becomes easier.

[0013] (7) In any one of the tire manufacturing methods (1) to (6) above, Preferably, in the sipe forming step, a plurality of sipes are formed at intervals from one another in the tire circumferential direction of the molded tire. In this case, the effect of the sipes is more effectively exhibited. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a tire manufacturing method for obtaining a tire in which the sipe width is less likely to change. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 2 is a development view of a tread surface showing an example of a tread pattern of a tire that can be obtained by a tire manufacturing method according to any embodiment of the present invention. [Figure 2] FIG. 2 is a development view of a tread surface showing another example of a tread pattern of a tire that can be obtained by a tire manufacturing method according to any embodiment of the present invention. [Figure 3] 1 is a flowchart illustrating a method for manufacturing a tire according to one embodiment of the present invention. [Figure 4] 1A and 1B are diagrams for explaining a tire manufacturing method according to one embodiment of the present invention, in which (a) is a diagram showing a base tire prepared in a base tire preparation process, (b) is a diagram showing a molded tire assembled in a molded tire assembly process, (c) is a diagram showing the molded tire vulcanization process, and (d) is a diagram showing the sipe formation process. DETAILED DESCRIPTION OF THE INVENTION

[0016] The tire manufacturing method according to the present invention can be suitably used as a manufacturing method for any type of pneumatic tire, for example, TB tires (tires for trucks and buses), LT tires (tires for vans and light trucks, tires for light trucks and buses), OR tires (tires for construction and mining vehicles), etc., and is particularly preferably used as a manufacturing method for TB tires or LT tires.

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a tire manufacturing method according to the present invention will be described with reference to the drawings. In each drawing, the same members and parts are designated by the same reference numerals. In this specification, the "tire circumferential direction" refers to the direction in which the tire rotates around the tire's rotation axis, the "tire radial direction" refers to the direction perpendicular to the tire's rotation axis, and the "tire width direction" refers to the direction parallel to the tire's rotation axis. In some drawings, the tire circumferential direction is indicated by the symbol "CD," the tire radial direction is indicated by the symbol "RD," and the tire width direction is indicated by the symbol "WD." In this specification, the side closer to the tire equatorial plane CL along the tire width direction is referred to as the "inner side in the tire width direction," and the side farther from the tire equatorial plane CL along the tire width direction is referred to as the "outer side in the tire width direction." Furthermore, in this specification, "extending in the tire circumferential direction" means extending with at least a tire circumferential component. That is, "extending in the tire circumferential direction" means that it may extend in a direction along the tire circumferential direction (i.e., at an angle of 0° with respect to the tire circumferential direction, and not inclined with respect to the tire circumferential direction), or it may extend inclined at an angle other than 90° with respect to the tire circumferential direction (i.e., inclined with respect to the tire circumferential direction, at an inclination angle greater than 0° and other than 90° with respect to the tire circumferential direction). Furthermore, in this specification, "extending in the tire width direction" means extending with at least a tire width direction component. That is, "extending in the tire width direction" means that it may extend in a direction along the tire width direction (i.e., at an angle of 0° with respect to the tire width direction, and not inclined with respect to the tire width direction), or it may extend inclined at an angle other than 90° with respect to the tire width direction (i.e., inclined with respect to the tire width direction, at an inclination angle greater than 0° and other than 90° with respect to the tire width direction).

[0018] Unless otherwise specified, the positional relationship and dimensions of each element are measured under standard conditions in which the tire is mounted on an applicable rim, inflated to a specified internal pressure, and unloaded. Furthermore, the outer peripheral surface of the tire that comes into contact with the road surface when the tire is mounted on an applicable rim, inflated to a specified internal pressure, and under maximum load is referred to as the "tread surface," and the edge of the tread surface in the tire width direction is referred to as the "tread edge." Furthermore, in this specification, the "developed view of the tread surface" refers to the planar view of the tread surface when the tread surface is developed on a plane.

[0019] In this specification, the term "applicable rim" refers to the standard rim (Measuring Rim in the ETRTO Standards Manual and Design Rim in the TRA Year Book) for the applicable size, which is an industrial standard valid in the region where the tire is produced and used, and which is described or will be described in the future, such as the JATMA Year Book of the Japan Automobile Tire Manufacturers Association (JATMA) in Japan, the European Tyre and Rim Technical Organization (ETRTO) Standards Manual in Europe, and the Tire and Rim Association, Inc. (TRA) Year Book in the United States. However, for sizes not described in these industrial standards, it refers to a rim with a width corresponding to the bead width of a pneumatic tire. "Applicable rim" includes not only current sizes but also sizes that will be described in the aforementioned industrial standards in the future. An example of a "size to be described in the future" is the size described as "FUTURE DEVELOPMENTS" in the 2013 edition of the ETRTO Standards.

[0020] In this specification, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel for the applicable size and ply rating as set forth in the aforementioned industrial standards, such as the JATMA Yearbook, or, in the case of a size not set forth in the aforementioned industrial standards, refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is to be mounted. Furthermore, in this specification, "maximum load" refers to the load corresponding to the maximum load capacity of the tire for the applicable size as set forth in the aforementioned industrial standards, or, in the case of a size not set forth in the aforementioned industrial standards, the load corresponding to the maximum load capacity specified for each vehicle on which the tire is to be mounted.

[0021] <Tires> First, with reference to FIGS. 1 and 2, examples of tread patterns of a tire that can be obtained by a tire manufacturing method according to any embodiment of the present invention will be described. 1 and 2 are developments of tread surfaces showing examples of tread patterns of a tire that can be obtained by a tire manufacturing method according to any embodiment of the present invention.

[0022] FIG. 1 shows an example of a tread pattern of a tire that can be obtained by a tire manufacturing method according to any embodiment of the present invention. 1, the tire 10 has a rib pattern on the tread surface 15. That is, the tire 10 of this example has, on the tread surface 15, a plurality of land portions 14 (six in the example shown) that are partitioned in the tire width direction by a plurality of main grooves 13 (five in the example shown) extending in the tire circumferential direction, and each land portion 14 is a rib-like land portion that extends continuously in the tire circumferential direction. As shown in FIG. 1 , the tire 10 of this example has sipes 16 provided in land portions 14 for the purpose of improving wear resistance, wet performance, ice performance, and the like. More specifically, in the example of FIG. 1 , each land portion 14 has a plurality of sipes 16 provided at intervals in the tire circumferential direction. In this example, the sipes 16, more specifically, the plurality of sipes 16, are provided so as to avoid joint portions 2a (shown by dotted lines in FIG. 1 because they may be difficult to see) of a tread rubber 2 (see FIGS. 4(b) to 4(d)) described below (i.e., so as not to overlap with the joint portions 2a in a developed view of the tread surface). Also, in this example, as shown in FIG. 1 , the sipes 16, more specifically, the plurality of sipes 16, are provided linearly in a direction inclined with respect to the tire circumferential direction (i.e., at an angle of more than 0° with respect to the tire circumferential direction in a developed view of the tread surface) (more specifically, in this example, in a direction inclined with respect to the tire width direction as well). Furthermore, in this example, the sipes 16, more specifically, each of the multiple sipes 16, may be arranged so that the depth of the sipe 16 increases as it moves from at least one or both tread edges TE toward the tire equatorial plane CL (not shown). 1, each sipe 16 is provided so as to cross each land portion 14 (i.e., continuously from one end of each land portion 14 in the tire width direction to the other end). Furthermore, in this example, as shown in FIG. 1, each sipe 16 is provided so as to extend in a straight line from one tread edge TE to the other tread edge TE, between each land portion 14, straddling each main groove 13 (i.e., interrupted by each main groove 13).

[0023] However, the tread pattern of a tire that can be obtained by the tire manufacturing method according to any embodiment of the present invention is not limited to the rib pattern described above. The tread pattern may be a block pattern as described later with reference to Fig. 2 or any other tread pattern, as long as it has sipes 16.

[0024] In this specification, "sipe" refers to a thin cut made in the tread surface, and more specifically, refers to a sipe whose width is 1.0 mm or less over an area of ​​50% or more of the sipe depth in the aforementioned standard condition. Here, "sipe depth" is measured in a direction perpendicular to the tread surface in the standard condition, and "sipe width" is measured in a direction parallel to the tread surface in a cross section perpendicular to the extension direction of the sipe on the tread surface in the standard condition. The sipe width may be constant or may vary in the direction perpendicular to the tread surface.

[0025] The tire 10 obtainable by the tire manufacturing method according to any embodiment of the present invention comprises a tire main body portion 11 (see FIG. 4(d)) formed from a base tire 1 (see FIG. 4) described later (in other words, using the base tire 1 as the material), and a tread rubber portion 12 (see FIGS. 1 to 2, 4(d)) formed from a tread rubber 2 (see FIG. 4) described later (in other words, using the tread rubber 2 as the material). The tire main body 11 may include, for example, general tire components other than tread rubber, such as left and right bead portions, a carcass consisting of one or more carcass plies spanning between them, a belt consisting of one or more belt layers arranged radially outside the carcass, sidewall rubber, etc. The tread rubber portion 12 includes at least tread rubber, which is a tire component other than the tire main body portion.

[0026] FIG. 2 shows another example of a tire tread pattern that can be obtained by the tire manufacturing method according to any embodiment of the present invention. 2, the tire 10 has a block pattern on the tread surface 15. That is, the tire 10 of this example has, on the tread surface 15, a plurality of land portions 14 (four in the example shown) that are partitioned in the tire width direction by a plurality of main grooves 13 (three in the example shown) extending in the tire circumferential direction, and each land portion 14 is a block-shaped land portion having a plurality of blocks 14b that are partitioned in the tire circumferential direction by lateral grooves 14a extending in the tire width direction. As shown in Fig. 2, the tire 10 of this example also has sipes 16 provided in the land portions 14 for the purpose of improving wear resistance, wet performance, ice performance, and the like. More specifically, in the example of Fig. 2, each land portion 14 has a plurality of sipes 16 provided at intervals from one another in the tire circumferential direction. In this example as well, the sipes 16, more specifically, the plurality of sipes 16, are provided so as to avoid joint portions 2a (shown by dotted lines in Fig. 2 because they may be difficult to see) of the tread rubber 2 (see Figs. 4(b) to (d)) described below (i.e., so as not to overlap with the joint portions 2a in a developed view of the tread surface). 2, the sipes 16, more specifically, the plurality of sipes 16, are also provided linearly in a direction inclined with respect to the tire circumferential direction (i.e., at an angle of more than 0° with respect to the tire circumferential direction in a developed view of the tread surface) (more specifically, in this example, along the tire width direction, i.e., at an angle of 90° with respect to the tire circumferential direction and 0° with respect to the tire width direction). Furthermore, in this example, the sipes 16, more specifically, the plurality of sipes 16, may also be provided so that the depth of the sipes 16 increases from at least one or both tread edges TE toward the tire equatorial plane CL (not shown). 2, in the present example, in the two land portions 14 on the inner side in the tire width direction near the tire equatorial plane CL, the sipes 16 are provided so as to traverse each land portion 14 (i.e., continuously from one end of each land portion 14 in the tire width direction to the other end), while in the two land portions 14 on both outer sides in the tire width direction near the tread edge TE, the sipes 16 are provided so as to open into the main grooves 13 but not reach the tread edge TE but terminate within each land portion 14. Furthermore, in the present example, as shown in FIG. 2, the sipes 16 are provided so as to extend in a straight line between each land portion 14, straddling each main groove 13 (i.e., interrupted by each main groove 13).

[0027] <Tire manufacturing method> A method for manufacturing a tire according to one embodiment of the present invention will be described below with reference to FIGS. Fig. 3 is a flowchart illustrating a tire manufacturing method according to one embodiment of the present invention. Fig. 4 is a diagram illustrating a tire manufacturing method according to one embodiment of the present invention, in which (a) is a diagram showing a base tire prepared in a base tire preparation step, (b) is a diagram showing a molded tire assembled in a molded tire assembly step, (c) is a diagram showing a molded tire vulcanization step, and (d) is a diagram showing a sipe formation step. Figs. 4(a) to (d) are shown as schematic cross-sectional views in the tire width direction.

[0028] The tire manufacturing method according to one embodiment of the present invention is a so-called retread tire manufacturing method, and therefore the tire obtained by the tire manufacturing method according to one embodiment of the present invention is a retread tire. Generally, there are two methods for manufacturing retread tires: the COLD method (also called the precure method, etc.) and the HOT method (also called the remolding method, etc.). The tire manufacturing method according to the present invention can be used for either the COLD method or the HOT method. The COLD method involves winding a vulcanized precured tread around the crown portion of a base tire via unvulcanized cushion rubber to form a molded tire, and then vulcanizing the precured tread to the base tire at a relatively low temperature in a vulcanizer or the like. The HOT method involves winding unvulcanized tread rubber around the crown portion of a base tire and then vulcanizing the tread rubber to the base tire at a relatively high temperature in a mold. The example shown in FIG. 4 is an example of a COLD method manufacturing method.

[0029] The tire manufacturing method according to one embodiment of the present invention is for obtaining a tire having a tire main body portion 11 (see Figure 4(d)) and a tread rubber portion 12 (see Figures 1 to 2 and Figure 4(d)). As shown in FIG. 3, the tire manufacturing method according to one embodiment of the present invention includes, in this order, a base tire preparation step (step S101), a molded tire assembly step (step S102), a molded tire vulcanization step (step S103), and a sipe formation step (step S104).

[0030] (Tire base preparation process) First, in the tire casing preparation step, a tire casing 1, which is a tire main body portion of a used tire and will become the tire main body portion 11, is prepared (step S101). As shown in Figure 4(a), the base tire 1 is the part that was the tire main body of a used tire (not shown) from which the worn tread rubber portion has been removed, and is a component that will become the tire main body portion 11 (see Figure 4(d)) of the tire obtained by the tire manufacturing method of this embodiment. The base tire preparation process may include an incoming inspection process in which the tire body excluding the tread rubber portion of a used tire received from a market or the like is inspected to determine whether it can be reused, and a tread rubber portion removal process in which the tread rubber portion is removed from the used tire.

[0031] (Molded tire assembly process) After the base tire preparation process, in the molded tire assembling process, a molded tire 4 is assembled by attaching tread rubber 2 that becomes the tread rubber portion 12 to the outer periphery of the base tire 1 prepared in the base tire preparation process (step S102). The tread rubber 2 is a member that will become the tread rubber portion 12 (see FIGS. 1 to 2 and 4(d)) of the tire obtained by the tire manufacturing method of this embodiment. The tread rubber 2 may have a length equivalent to one circumference of the tire.

[0032] As mentioned above, the example shown in Fig. 4 shows an example of the COLD method, which is one of the common methods for manufacturing retread tires. That is, in the example of Fig. 4, in the molded tire assembling process, vulcanized tread rubber 2 (generally also called precured tread) is wound and attached to the outer surface of base tire 1 via unvulcanized cushion rubber 3 (see Fig. 4(b)). In other words, in the example of Fig. 4, the molded tire 4 assembled in the molded tire assembling process is one in which vulcanized tread rubber 2 is wound and attached (more specifically, attached) to the outer surface of base tire 1 via unvulcanized cushion rubber 3. The unvulcanized cushion rubber 3 may have a length equivalent to one circumference of the tire. In this example, the vulcanized tread rubber 2 used in the molded tire assembling process is flat before being attached to the base tire 1, and at least a tread pattern other than the sipes 16 (for example, a tread pattern such as that illustrated in FIGS. 1 and 2 excluding the sipes 16) is formed in advance on the surface of the vulcanized tread rubber 2. In this example, in the molded tire assembling process, after the unvulcanized cushion rubber 3 is wound around and attached (more specifically, attached) to the outer surface of the base tire 1, the vulcanized tread rubber 2 may be further wound around and attached (more specifically, attached) to the outer surface of the unvulcanized cushion rubber 3, or the unvulcanized cushion rubber 3 and the vulcanized tread rubber 2 may be bonded together in advance, and the composite may be wound around and attached (more specifically, attached) to the outer surface of the base tire 1. In this example, in the molded tire assembling process, an adhesive may be further interposed between at least one of the base tire 1, the unvulcanized cushion rubber 3, and the vulcanized tread rubber 2. As in the above example, when vulcanized tread rubber 2 is wrapped around and attached to the outer surface of base tire 1 via unvulcanized cushion rubber 3 during the molded tire assembly process, large equipment such as a normal vulcanization mold is not required, particularly during the subsequent molded tire vulcanization process, making it possible to manufacture tires on a compact line.

[0033] However, the manufacturing method of the tire according to the present embodiment is not limited to the example shown in FIG. 4 , and may be a HOT method among general manufacturing methods for retread tires. That is, although not shown, in the molded tire assembling process, the unvulcanized tread rubber 2 may be wound and attached to the outer surface of the base tire 1 without the unvulcanized cushion rubber 3 or the like. In other words, the molded tire 4 assembled in the molded tire assembling process may be one in which the unvulcanized tread rubber 2 is wound and attached (more specifically, attached) to the outer surface of the base tire 1 without the unvulcanized cushion rubber 3 or the like. In this case, a tread pattern does not need to be formed in advance on the surface of the unvulcanized tread rubber 2 used in the molded tire assembling process. Furthermore, in this case, an adhesive may be interposed between the base tire 1 and the unvulcanized tread rubber 2 in the molded tire assembling process. As in the above example, when unvulcanized tread rubber 2 is wrapped around and attached to the outer surface of base tire 1 in the molded tire assembly process, in the subsequent molded tire vulcanization process, as described below, the molded tire 4 is sealed in a normal tread patterned vulcanization mold and vulcanized. Therefore, when the tread rubber 2 is wrapped around and attached to the outer peripheral surface of the base tire 1, joint portions 2a and the like in the circumferential direction of the tread rubber 2 are less noticeable, and the appearance of the manufactured tire is likely to be better.

[0034] (Formed tire vulcanization process) After the molded tire assembling process, in the molded tire vulcanizing process, as shown in FIG. 4(c), the molded tire assembled in the molded tire assembling process is vulcanized (step S103) (see FIG. 4(c)). The vulcanization may be performed by a predetermined vulcanizing device 6.

[0035] In the example shown in Figure 4 (i.e., the case of the aforementioned COLD method in which vulcanized tread rubber 2 is wrapped around and attached to the outer surface of base tire 1 via unvulcanized cushion rubber 3 in the molded tire assembly process), a tread pattern, excluding at least sipes 16, is already formed on the surface of the vulcanized tread rubber 2 used in the molded tire assembly process, so vulcanization in the molded tire vulcanization process does not need to be carried out in a normal vulcanization mold with a tread pattern. Instead, a small vulcanization can CG as schematically shown in Figure 4(c) can be used as the vulcanization device 6, and the molded tire 4 can be sealed in the vulcanization can CG and heated and pressurized at a relatively low temperature, thereby vulcanizing the unvulcanized cushion rubber 3 and ultimately vulcanizing and adhering the vulcanized tread rubber 2 (precured tread) to the base tire 1.

[0036] On the other hand, in the case of the above-mentioned HOT method in which unvulcanized tread rubber 2 is wound and attached to the outer surface of base tire 1 in the molded tire assembly process, vulcanization in the molded tire vulcanization process uses, for example, a tread patterned vulcanization mold (not shown) engraved with at least a tread pattern excluding sipes 16 (for example, a tread pattern as exemplified in Figures 1 and 2 , excluding sipes 16, with the concaves and convulsions reversed), as vulcanization device 6, and the molded tire 4 is sealed inside the vulcanization mold and subjected to a heating and pressure treatment at a relatively high temperature, thereby vulcanizing and adhering the unvulcanized tread rubber 2 to the base tire 1.

[0037] However, the vulcanization method and vulcanization device used in the molded tire vulcanization process are not particularly limited to those described above, and may be any as long as at least a necessary tread pattern other than the sipes 16 is formed on the tread surface 5 (see FIG. 4(d)) of the molded tire 4 vulcanized in the molded tire vulcanization process. Note that one or more sipes 16 other than the sipes 16 formed in the sipe formation process described below may be formed on the tread surface 5 of the molded tire 4 vulcanized in the molded tire vulcanization process, as necessary.

[0038] (Sipe formation process) After the molded tire vulcanization step, in the sipe forming step, sipes 16 are formed on the tread surface 5 of the molded tire 4 vulcanized in the molded tire vulcanization step (step S104) (see FIG. 4(d)). The formation of the sipes 16 may be performed by a predetermined sipe forming device 7. The sipe forming process can form, for example, sipes 16 in the tread pattern as illustrated in Figures 1 and 2 on the tread surface 5 of the molded tire 4 after vulcanization through the molded tire vulcanization process (and thus on the tread surface 15 of the tire 10). Note that in Figure 4, the main grooves and the like formed on the surface (tread surface 5) of the tread rubber 2 are depicted for the sake of convenience of explanation, and do not strictly correspond to the configuration (number, etc.) of the main grooves 13 and the like in the tread patterns of Figures 1 and 2.

[0039] In the sipe forming step, the sipes 16 can be formed using a sipe forming device 7 such as a cutter (hot knife) or a laser. In the example shown in Fig. 4, in the sipe forming process, sipes 16 are formed using a guillotine cutter GC, as shown schematically in Fig. 4(d), as the sipe forming device 7. Here, the "guillotine cutter" refers to a device that, after inflating a tire to a low internal pressure (approximately 50 kPa) so that the tire fits the rim and mounting it on the rim, rotatably fixes the tire around its axis of rotation, and forms sipes while gradually rotating the tire using a blade (thin blade) that is movable in the tire radial direction. In Fig. 4(d), the downward white arrows indicate the movement of the guillotine cutter GC (more specifically, the blade of the guillotine cutter GC) radially inward toward the tread surface 5 of the vulcanized molded tire 4, attempting to form sipes. The guillotine cutter GC is suitable for forming a plurality of sipes on a tread surface 5 having a rib pattern in which the land portions 14 (see FIGS. 1 and 2) extend continuously in the tire circumferential direction, for example. The laser is also suitable for forming a plurality of sipes on a tread surface 5 having a block pattern in which the land portions 14 are discontinuous in the tire circumferential direction, for example. However, the sipe forming method and the sipe forming device used in the sipe forming process are not particularly limited to those described above, and may be any. A preferred sipe forming method in the sipe forming step will be described in further detail later.

[0040] Next, the effects of the tire manufacturing method according to the embodiment of the present invention will be described. First, in this embodiment, there are a base tire preparation process in which a base tire 1 is prepared, a molded tire assembly process in which a molded tire 4 is assembled by attaching tread rubber 2 to the outer periphery of the base tire 1, and a molded tire vulcanization process in which the molded tire 4 is vulcanized, so that a tire (particularly a retread tire) can be obtained as usual. Furthermore, according to this embodiment, in the molded tire assembling process, tread rubber 2 is attached to the outer periphery of a prepared base tire 1, and in the sipe forming process, sipes 16 are formed on the tread surface 5 of a vulcanized molded tire 4. That is, according to this embodiment, the base tire 1 that was the tire main body portion of a used tire is used as the tire main body portion 11, and sipes 16 are formed in the molded tire 4 after vulcanization. Here, it is known that new tires that are not retread tires (in other words, that do not use a base tire) obtained by a normal manufacturing method will grow in diameter as the tire is driven for a while after it has started to be used, and if the new tire has sipes, there is a risk that the sipe width will widen as the tire grows in diameter. In contrast, according to this embodiment, a base tire 1 whose diameter growth has already finished is used in the molded tire assembly process, and therefore the tire main body portion 11 of the manufactured tire is the base tire 1 whose diameter growth has already finished, so it is possible to obtain a tire in which the sipe width of the initially formed sipes is less likely to change compared to a normal new tire manufactured without using the base tire 1. Also, for example, in the above-mentioned cold-type manufacturing method, it is conceivable to carry out the molded tire assembly process using vulcanized tread rubber in which sipes have been formed in advance by forming sipes with a cutter or the like while the vulcanized tread rubber (precured tread) is placed on a flat plate, but in that case, there is also a risk that the sipe width will become wider when the vulcanized tread rubber 2 is wrapped around and attached to the outer peripheral surface of the base tire 1 in the molded tire assembly process. In contrast, according to the present embodiment, the sipes 16 are formed after the molded tire 4 is vulcanized in the sipe forming process, so it is possible to obtain a tire in which the initially formed sipe width is less likely to change compared to when a molded tire is assembled in the molded tire assembly process using vulcanized tread rubber in which sipes have been formed in advance. As described above, the tire manufacturing method according to this embodiment makes it possible to obtain a tire in which the sipe width is less likely to change, and thus to prevent the effects of the sipes, such as improved wear resistance, from being fully exerted due to an increase in the sipe width, or to prevent cracks from occurring more easily at the bottom of the sipes.

[0041] Furthermore, according to this embodiment, instead of forming sipes during vulcanization using a vulcanization mold equipped with a sipe-forming blade (for example, in the above-mentioned HOT method manufacturing method, it is also possible to form sipes during vulcanization using a vulcanization mold in the molded tire vulcanization process), sipes 16 are formed in the molded tire 4 after vulcanization in the sipe formation process using, for example, a cutter or laser, making it easy to customize the performance of each tire according to customer requests, etc.

[0042] Next, a preferred sipe forming method and the like in the above-mentioned sipe forming step will be further described. The arrangement, configuration, etc. of the sipes formed in the vulcanized molded tire 4 in the sipe forming step are substantially the same as the arrangement, configuration, etc. of the sipes in the tire 10 obtained by the manufacturing method. Therefore, for the sake of convenience, the following description will be given with reference to Figures 1 and 2, which explain an example of the tire 10, as appropriate.

[0043] First, in the sipe forming process, it is preferable that the sipes 16 are formed so as to avoid the joint portions 2a in the tire circumferential direction of the tread rubber 2 of the molded tire 4 that are generated when the tread rubber 2 is attached to the outer periphery of the base tire 1 in the molded tire assembling process, as shown in Figures 1 and 2 (so as not to overlap with the joint portions 2a when viewed in a developed view of the tread surface). In this case, failures caused by the sipes 16 are less likely to occur, and consequently, a decrease in the durability of the tire can be suppressed.

[0044] In the sipe forming step, it is preferable that the sipes 16 are formed linearly in a direction inclined with respect to the tire circumferential direction of the molded tire 4, as shown in FIGS. In this case, the sipes 16 can be easily formed by, for example, a guillotine cutter GC having a simple straight blade, so that the formation of the sipes 16 becomes easier.

[0045] Furthermore, although not shown, in the sipe forming process, it is preferable that the sipes 16 are formed so that the depth of the sipes 16 (sipe depth) becomes deeper as it approaches the center of the tire width direction of the molded tire 4 (i.e., the tire equatorial plane CL). In a vulcanized molded tire 4 that has undergone the molded tire vulcanization process, the surface of the tread rubber 2 (tread surface 5, and therefore tread contact surface 15) is usually formed in a slight arc shape with a convex R facing outward in the tire radial direction when viewed in cross section in the tire width direction. For this reason, in the above case, the formation of the sipes 16 can be easily performed using, for example, a guillotine cutter GC equipped with a blade whose cutting edge is linear in side view, making the formation of the sipes 16 easier.

[0046] In the sipe forming step, it is preferable that a plurality of sipes 16 are formed at intervals in the tire circumferential direction of the molded tire 4, as shown in FIGS. In this case, the effects of the sipes 16, such as improved wear resistance, are more effectively exhibited.

[0047] The width of the sipe 16 formed in the sipe forming process (sipe width) is preferably 0.7 mm or less, more preferably 0.5 mm or less, and even more preferably 0.4 mm or less, over an area of ​​50% or more of the sipe depth. Furthermore, the sipe width is preferably 0.2 mm or more over an area of ​​50% or more of the sipe depth. Furthermore, the sipe width is preferably 0.2 to 0.5 mm, and more preferably 0.2 to 0.4 mm, over an area of ​​50% or more of the sipe depth. The thinner the sipe width is, within the above 0.7 mm or less, the easier it is to achieve the effects of the sipe 16, such as improving wear resistance, and by making it 0.2 mm or more, it becomes easier to form the sipe using a cutter or the like.

[0048] In order to improve the wear resistance of the tire, it is preferable that in the sipe forming process, the sipes 16 are formed linearly in a direction inclined with respect to the tire circumferential direction of the molded tire 4, as shown in Figures 1 and 2, and that multiple sipes are formed at intervals from each other in the tire circumferential direction of the molded tire 4; in other words, when viewed in a developed view of the tread surface, multiple linear sipes 16 extending in the tire width direction are formed at intervals from each other in the tire circumferential direction. In this case, the circumferential spacing between adjacent sipes 16 in the tire circumferential direction (hereinafter simply referred to as the "circumferential spacing between (plural) sipes 16") is preferably 5 to 40 mm. If the spacing is 5 mm or more, the rigidity of the land portion 14 does not decrease excessively (i.e., it does not become too flexible), and if the spacing is 40 mm or less, the rigidity of the land portion 14 decreases appropriately (i.e., it becomes appropriately flexible), reducing the amount of slippage between the land portion 14 and the ground contact surface during tire rotation. In either case, wear resistance is more likely to be improved. From the same perspective, in the above case, the circumferential spacing between the sipes 16 is more preferably 10 to 30 mm. Furthermore, from the same perspective, in the above case, the sipe depth of the sipes 16 is preferably 40 to 100% of the depth of the main groove 13. Furthermore, when forming a plurality of linear sipes 16 extending in the tire width direction at intervals in the tire circumferential direction as described above, it is preferable that the intervals between the sipes 16 in the tire circumferential direction be uniform over the entire tire circumferential direction, in other words, that the plurality of sipes 16 be formed at equal intervals over the entire tire circumferential direction. In this case, the performance such as wear resistance exhibited by the sipes 16 can be made uniform over the entire tire circumferential direction.

[0049] A plurality of ribs (for example, as shown in FIG. 1, which will become rib-like land portions 14 in the manufactured tire 10) and / or a plurality of blocks (for example, as shown in FIG. 2, which will become blocks 14b in the manufactured tire 10) are defined and formed on the surface of the vulcanized tread rubber 2 (precured tread) used in the molded tire assembling process (in the case of the above-mentioned COLD method manufacturing method), or a plurality of ribs (for example, as shown in FIG. 1, which will become rib-like land portions 14 in the manufactured tire 10) and / or a plurality of blocks (for example, as shown in FIG. 2, which will become blocks 14b in the manufactured tire 10) are defined and formed on the surface of the tread rubber 2 in the molded tire vulcanization process (in the case of the above-mentioned HOT method manufacturing method), and at the same time, a plurality of sipes 16 may be formed on some or all of the plurality of ribs and / or multiple blocks in the sipe forming process so that the tire circumferential spacing, depth, and / or angle with respect to the tire circumferential direction are different for each of the plurality of ribs and / or multiple blocks. In this case, in the sipe forming process, for example, a guillotine cutter GC may be used to form sipes of a first type at intervals around the tire circumferential direction over a portion or the entire circumference of the tire, and then sipes of a second type different from the first type may be formed at intervals around the tire circumferential direction over a portion or the entire circumference of the tire, and further, the formation of the sipes may be repeated to form sipes of a third or subsequent type different from the types of sipes formed up to that point.

[0050] Furthermore, in the sipe forming process, the sipes 16 may be formed across the entire width of the molded tire 4 (and thus the tire 10) in the tire width direction (see, for example, the example in Figure 1), or may be formed only over a portion of the tire width direction (see, for example, the example in Figure 2). Furthermore, in the sipe forming process, the sipes 16 may be formed across the entire width of the tire in the tire width direction in each land portion 14 of the molded tire 4 (and ultimately the tire 10) that is partitioned in the tire width direction by main grooves 13 extending in the tire circumferential direction (see, for example, the example in Figure 1), or may be formed only in a portion of the tire width direction in at least some of the land portions 14 (see, for example, the example in Figure 2).

[0051] The above describes preferred sipe formation methods and the like in the sipe formation process, but the method of forming sipes in the sipe formation process is not particularly limited to the above-mentioned embodiments and may be any method as long as it forms sipes 16 on the tread surface 5 of the molded tire 4 vulcanized in the molded tire vulcanization process.

[0052] According to the tire manufacturing method of one embodiment of the present invention described above, for example, a tire 10 using a base tire 1 that was the tire main body portion of a used tire as the tire main body portion 11 and having a tread pattern as illustrated and described with reference to Figures 1 and 2 can be obtained by forming sipes 16 in a vulcanized molded tire 4 in a sipe forming step so that the sipes 16 are arranged and configured in the tire 10.

[0053] Furthermore, according to a tire manufacturing method according to one embodiment of the present invention, for example, by using a regular guillotine cutter or the like in the sipe forming step, which has a blade thickness that is constant in the depth direction of the sipes 16 to be formed, it is possible to obtain, for example, a tire 10 having a tire main body 11 and a tread rubber 12, where the tire main body 11 is made from a base tire 1 that was the tire main body of a used tire, and where a plurality of sipes 16 are formed on the surface of the tread rubber 12, and the width of each of the plurality of sipes 16 is substantially constant in the depth direction. In this tire 10, the width of the sipes 16 is unlikely to change.

[0054] The foregoing describes exemplary embodiments of the present invention, and various modifications can be made without departing from the scope of the claims. For example, in the present invention, when the vulcanized tread rubber 2 is wound and attached to the outer peripheral surface of the base tire 1 via the unvulcanized cushion rubber 3 in the molded tire assembling step (i.e., in the case of the above-mentioned COLD manufacturing method), an envelope step of wrapping the molded tire 4 in a rubber bag may be further included between the molded tire assembling step and the molded tire vulcanization step. Also, for example, in the present invention, an inspection step or the like may be further included after the molded tire vulcanization step and / or the sipe forming step, of inspecting whether there are any abnormalities in the vulcanized molded tire 4 and / or the tire 10 after the sipe formation. [Industrial Applicability]

[0055] The tire manufacturing method according to the present invention can be suitably used as a manufacturing method for any type of pneumatic tire, for example, TB tires (tires for trucks and buses), LT tires (tires for vans and light trucks, tires for light trucks and buses), OR tires (tires for construction and mining vehicles), etc., and is particularly preferably used as a manufacturing method for TB tires or LT tires. [Explanation of symbols]

[0056] 1: Base tire, 2: Tread rubber, 2a: Joint part, 3: Cushion rubber, 4: molded tire; 5: tread surface; 6: vulcanizing device; 7: sipe forming device; 10: tire; 11: tire body; 12: tread rubber portion; 13: main groove; 14: land portion, 14a: lateral groove, 14b: block, 15: tread surface, 16: Sipe, CC: Vulcanization can, CD: Tire circumferential direction, CL: Tire equatorial plane, GC: Guillotine cutter, RD: Tire radial direction, WD: Tire width direction

Claims

1. A tire manufacturing method for obtaining a tire having a tire main body portion and a tread rubber portion, comprising: a tire casing preparation step of preparing a tire casing that is a tire main body portion of a used tire and that will become the tire main body portion; a molded tire assembling process for assembling a molded tire by attaching tread rubber that becomes the tread rubber portion to an outer peripheral side of the prepared base tire; a molded tire vulcanization step of vulcanizing the assembled molded tire; a sipe forming step of forming sipes on a tread surface of the vulcanized molded tire; and In the sipe forming step, the sipes are formed so as to avoid joint portions in the tire circumferential direction of the tread rubber of the molded tire.

2. The tire manufacturing method according to claim 1 , wherein in the molded tire assembling step, the vulcanized tread rubber is wound and attached to the outer peripheral surface of the base tire via an unvulcanized cushion rubber.

3. The tire manufacturing method according to claim 1 , wherein in the molded tire assembling step, the unvulcanized tread rubber is wound and attached to an outer peripheral surface of the base tire.

4. The tire manufacturing method according to any one of claims 1 to 3, wherein in the sipe forming step, the sipes are formed linearly in a direction inclined with respect to a tire circumferential direction of the molded tire.

5. 4. The tire manufacturing method according to claim 1, wherein in the sipe forming step, the sipes are formed so that a depth of the sipes increases toward a center of the molded tire in a tire width direction.

6. The tire manufacturing method according to any one of claims 1 to 3, wherein in the sipe forming step, a plurality of the sipes are formed at intervals from each other in the tire circumferential direction of the molded tire.

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