阅读说明：本技术 充气轮胎的制造方法和充气轮胎 (Pneumatic tire manufacturing method and pneumatic tire ) 是由 长谷川圭一 片山昌宏 于 2018-05-22 设计创作，主要内容包括：充气轮胎的制造方法包括在硫化模具内对未硫化轮胎进行硫化的硫化工序,未硫化轮胎(1’)的胎圈芯(60)具有胎圈线束(62)和由树脂材料构成的包覆层(65),在硫化工序中,胎圈芯的包覆层的轮胎径向内侧的面(651)与硫化模具的胎圈底部成形面(221)之间的轮胎径向距离(L1)在至少一部分的轮胎宽度方向区域随着向轮胎宽度方向内侧去而保持恒定或者逐渐减小。(A method for manufacturing a pneumatic tire includes a vulcanization step of vulcanizing an unvulcanized tire in a vulcanization mold, wherein a bead core (60) of the unvulcanized tire (1') has a bead bundle (62) and a covering layer (65) made of a resin material, and in the vulcanization step, a tire radial direction distance (L1) between a surface (651) of the covering layer of the bead core on the inner side in the tire radial direction and a bead bottom molding surface (221) of the vulcanization mold is kept constant or gradually reduced toward the inner side in the tire width direction in at least a part of a tire width direction region.)

1. A method for manufacturing a pneumatic tire, comprising a vulcanization step of vulcanizing an unvulcanized tire in a vulcanization mold,

with the unvulcanized tire, when the tire width direction section is observed, a bead core of the unvulcanized tire has a bead wire bundle and a covering layer which surrounds the periphery of the bead wire bundle and is composed of a resin material,

in the vulcanization step, a tire radial direction distance between a tire radial direction inner side surface of the covering layer of the bead core and a bead bottom portion molding surface of the vulcanization mold is kept constant or gradually decreased toward a tire width direction inner side in at least a part of a tire width direction region.

2. The manufacturing method of a pneumatic tire according to claim 1,

in the vulcanization step, a minimum value of the tire radial direction distance on the inner side in the tire width direction with respect to the tire width direction center of the bead core is equal to a minimum value of the tire radial direction distance on the outer side in the tire width direction with respect to the tire width direction center of the bead core, or is shorter than a minimum value of the tire radial direction distance on the outer side in the tire width direction with respect to the tire width direction center of the bead core.

3. The manufacturing method of a pneumatic tire according to claim 1 or 2,

in the vulcanization step, a surface of the bead core on the inner side in the tire radial direction of the covering layer and the bead bottom portion molding surface of the vulcanization mold gradually extend toward the inner side in the tire radial direction as going toward the inner side in the tire width direction.

4. The manufacturing method of a pneumatic tire according to claim 3,

with respect to the bead core of the unvulcanized tire, when a tire width direction cross section is observed, a corner portion of the covering layer which is an inner side in the tire width direction and an inner side in the tire radial direction has a rounded or chamfered shape.

5. A pneumatic tire, wherein,

the bead core has a bead wire bundle and a covering layer which surrounds the periphery of the bead wire bundle and is composed of a resin material when the tire width direction section is observed,

the tire radial direction distance between the tire radial direction inner side surface of the covering layer of the bead core and the bead bottom portion is kept constant or gradually reduced toward the tire width direction inner side in at least a part of the tire width direction region.

6. The pneumatic tire of claim 5,

a minimum value of the tire radial direction distance on the inner side in the tire width direction with respect to the tire width direction center of the bead core is equal to a minimum value of the tire radial direction distance on the outer side in the tire width direction with respect to the tire width direction center of the bead core, or is shorter than a minimum value of the tire radial direction distance on the outer side in the tire width direction with respect to the tire width direction center of the bead core.

7. The pneumatic tire according to claim 5 or 6,

the bead core has a surface on the inner side in the tire radial direction of the covering layer and a bead bottom portion each extending gradually toward the inner side in the tire radial direction as going inward in the tire width direction.

8. The pneumatic tire of claim 7,

with the bead core, when a tire width direction cross section is observed, a corner portion of the covering layer which is inside in the tire width direction and inside in the tire radial direction has a rounded or chamfered shape.

Technical Field

The present invention relates to a method of manufacturing a pneumatic tire and a pneumatic tire.

The present application claims priority based on application No. 2017-119975 filed in japan on 19/6/2017, the contents of which are incorporated herein in their entirety.

Background

Conventionally, in a typical pneumatic tire, the tire radial distance between the inner surface of the bead core in the tire radial direction and the bead bottom portion, and further the thickness of rubber between the inner surface of the bead core in the tire radial direction and the bead bottom portion in the tire radial direction gradually increases toward the inner side in the tire width direction (for example, patent document 1).

Disclosure of Invention

Problems to be solved by the invention

In the pneumatic tire as described above, in a state where the tire is assembled to the rim, there is a possibility that the compression rate of rubber between the surface on the inner side in the tire radial direction of the bead core and the bead seat of the rim, and further, the fitting force between the bead portion of the tire and the rim becomes weak mainly on the inner side in the tire width direction. The fitting force between the bead portion and the rim of the tire, and hence the adhesiveness, affects the running performance and the liquid-tightness of the tire. Therefore, there is room for further improvement in terms of the fitting force between the bead portion and the rim of the tire, and further, the moving performance and liquid tightness of the tire.

The present invention has been made to solve the above problems, and an object thereof is to provide a method for manufacturing a pneumatic tire for obtaining a pneumatic tire capable of improving a fitting force between a bead portion and a rim of the tire, and a pneumatic tire capable of improving a fitting force between a bead portion and a rim of the tire.

Means for solving the problems

The method for manufacturing a pneumatic tire according to the present invention includes a vulcanization step of vulcanizing an unvulcanized tire in a vulcanization mold, wherein, in the unvulcanized tire, when a tire width direction cross section is observed, a bead core of the unvulcanized tire has a bead bundle and a covering layer which surrounds the bead bundle and is made of a resin material, and in the vulcanization step, a tire radial direction distance between a surface on the inner side in the tire radial direction of the covering layer of the bead core and a bead bottom molding surface of the vulcanization mold is kept constant or gradually reduced toward the inner side in the tire width direction in at least a part of a tire width direction region.

The tire radial distance is measured in a direction perpendicular to the tire width direction in a cross section in the tire width direction.

In The present specification, "Rim" means an industrial standard effective in a region where a Tire is produced and used, including JATMA YEAR BOOK of JATMA (japan automobile Tire society), STANDARDS MANUAL of ETRTO (European Tire and Rim Technical organization, The European style and Rim Technical organization) of japan, STANDARDS MANUAL of TRA (american Tire and Rim Association, Inc.) of The usa, or a standard Rim of an application size described in The FUTURE (Measuring Rim of STANDARDS MANUAL of etro, and Design Rim of TRA) (that is, The above-mentioned "Rim" includes a size that may be included in The above-mentioned industrial standard in The FUTURE in addition to an existing size), but an opsize described as "FUTURE-described size" of "FUTURE-described" of The ETRTO STANDARDS MANUAL 2013 n edition of etro is cited as "full equipment" of The YEAR version, when the dimension is not described in the above-mentioned industrial standards, the dimension refers to a rim having a width corresponding to the bead width of the tire.

In the pneumatic tire of the present invention, when the tire width direction cross section is observed, the bead core has a bead bundle and a covering layer which surrounds the bead bundle and is composed of a resin material, and a tire radial direction distance between a surface on the inner side of the covering layer of the bead core in the tire radial direction and the bead bottom portion is kept constant or gradually reduced toward the inner side of the tire width direction in at least a part of the tire width direction area.

The distance in the tire radial direction between the surface of the bead core covering on the inner side in the tire radial direction and the bead bottom is measured in a state where the tire is not mounted on the rim.

The tire radial distance is measured in a direction perpendicular to the tire width direction in a cross section in the tire width direction.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a method of manufacturing a pneumatic tire for obtaining a pneumatic tire capable of improving a fitting force between a bead portion and a rim of the tire, and a pneumatic tire capable of improving a fitting force between a bead portion and a rim of the tire.

Drawings

Fig. 1 is a diagram for explaining a method of manufacturing a pneumatic tire according to an embodiment of the present invention, and is a diagram showing a state in which an unvulcanized tire is accommodated in a vulcanizing mold in a vulcanizing step, by using a tire width direction cross section of a tire half.

Fig. 2A is an enlarged view of a main portion of fig. 1.

Fig. 2B is a cross-sectional view in the tire width direction, which is an enlarged view of a main portion of the pneumatic tire according to the embodiment of the present invention obtained in the vulcanization step shown in fig. 2A.

Fig. 3 is a tire width direction cross-sectional view showing a tire half of the pneumatic tire of fig. 2B in a state of being assembled to a rim.

Fig. 4A is a diagram for explaining a method of manufacturing a pneumatic tire according to modification 1 of the present invention, and is a cross-sectional view in the tire width direction showing a state where an unvulcanized tire is accommodated in a vulcanizing mold in a vulcanizing step, with main parts being enlarged.

Fig. 4B is a cross-sectional view in the tire width direction, which is an enlarged view of a main portion of a pneumatic tire according to modification 1 of the present invention obtained in the vulcanization step shown in fig. 4A.

Fig. 5A is a diagram for explaining a method of manufacturing a pneumatic tire according to modification 2 of the present invention, and is a cross-sectional view in the tire width direction showing a state where an unvulcanized tire is housed in a vulcanizing mold in a vulcanizing step with main parts enlarged.

Fig. 5B is a cross-sectional view in the tire width direction, showing an enlarged view of a main portion of a pneumatic tire according to modification 2 of the present invention obtained in the vulcanization step shown in fig. 5A.

Fig. 6A is a diagram for explaining a method of manufacturing a pneumatic tire according to modification 3 of the present invention, and is a cross-sectional view in the tire width direction showing a state where an unvulcanized tire is accommodated in a vulcanizing mold in a vulcanizing step, with main parts being enlarged.

Fig. 6B is a cross-sectional view in the tire width direction, showing an enlarged view of a main portion of a pneumatic tire according to modification 3 of the present invention obtained in the vulcanization step shown in fig. 6A.

Fig. 7A is a view for explaining a method of manufacturing the bead core and the bead filler of fig. 1, and is a view showing a state in which the annular body is housed in the injection mold in the injection molding step, with an axial cross section of the annular body.

Fig. 7B is a view showing a bead core and a bead filler obtained by the injection molding step shown in fig. 7A, with an axial cross section of the annular body.

Detailed Description

Hereinafter, a method for manufacturing a pneumatic tire and an embodiment of a pneumatic tire according to the present invention will be described by way of example with reference to the accompanying drawings.

The method for manufacturing a pneumatic tire and the pneumatic tire according to the present invention can be used for any type of pneumatic tire such as a passenger vehicle pneumatic tire.

The method of manufacturing a pneumatic tire according to the present embodiment includes a vulcanization step of vulcanizing the unvulcanized tire 1' in the vulcanization mold 200. The unvulcanized tire 1' is manufactured in an unvulcanized tire manufacturing process before the vulcanizing process.

In the present specification, "unvulcanized tire" and "pneumatic tire" are also simply referred to as "tire".

Fig. 1 to 3 are drawings for explaining a pneumatic tire manufacturing method and a pneumatic tire according to the present embodiment. Fig. 1 is a view showing a state in which an unvulcanized tire 1' is housed in a vulcanizing mold 200 in a vulcanizing step in the method for manufacturing a pneumatic tire according to the present embodiment, with a cross section of a tire half in a tire width direction. Fig. 2A is an enlarged view of the vicinity of the bead portion 12 'of the unvulcanized tire 1' in fig. 1. Fig. 2B is a cross-sectional view in the tire width direction showing an enlarged vicinity of the bead portion 12 of the pneumatic tire 1 of the present embodiment obtained through the vulcanization step shown in fig. 1 and 2A. Fig. 3 is a cross-sectional view in the tire width direction showing the tire half of the pneumatic tire 1 of fig. 2B in a state assembled to a rim R.

The structure of the tires 1', 1 may be symmetrical or asymmetrical with respect to the tire equatorial plane CL. However, the structure of the tires 1', 1 preferably satisfies various structures described later on both sides with respect to the tire equatorial plane CL.

The unvulcanized tire manufacturing process performed before the vulcanizing process includes: a bead core manufacturing step of manufacturing a bead core 60; and an assembling and molding step of assembling the bead core 60 obtained in the bead core manufacturing step with other tire constituting members to obtain an unvulcanized tire 1' (fig. 1).

In this example, in the bead core manufacturing process, the core/filler member 50 is manufactured by integrally molding the bead core 60 and the bead filler 70. However, in the bead core manufacturing process, only the bead core 60 may be manufactured. In this case, the bead filler 70 may be manufactured separately by the bead filler manufacturing process.

The bead core manufacturing process is described in further detail later with reference to fig. 7A and 7B.

In the assembling and molding step, for example, the bead core 60 produced in the bead core production step, the unvulcanized rubber 40 ', and other tire constituting members (in this example, the carcass ply 20, the belt 30, and the like) are assembled and molded on a molding drum (not shown), and the unvulcanized tire 1' is obtained. In this example, in the assembly molding step, a cylindrical unvulcanized tire casing (not shown) composed of a part or all of the tire constituent members is expanded by the bladder 230.

As shown in fig. 1, an unvulcanized tire 1' obtained by the assembly molding process includes: a tread portion 10'; a pair of side portions 11 'extending inward in the tire radial direction from both ends in the tire width direction of the tread portion 10', respectively; and a pair of bead portions 12 'that are continuous from the sidewall portion 11' toward the inner side in the tire radial direction, respectively. The tread portion 10 ', the sidewall portion 11', and the bead portion 12 'of the unvulcanized tire 1' become the tread portion 10, the sidewall portion 11, and the bead portion 12, respectively, of the vulcanized tire 1 (fig. 3) after the vulcanization process.

In the example of fig. 1, the unvulcanized tire 1 'includes unvulcanized rubber 40', a bead core 60, a bead filler 70 located on the tire radial direction outer side of the bead core 60, a carcass 20, and a belt 30.

In the bead portion 12 ' of the unvulcanized tire 1 ', a bead core 60 and a bead filler 70 are embedded in an unvulcanized rubber 40 '. As described above, in the present example, the bead core 60 and the bead filler 70 constitute the core/filler member 50 integrally configured. However, the bead core 60 and the bead filler 70 may be separate bodies.

In the example of fig. 1, between a pair of bead cores 60 located on both sides with respect to the tire equatorial plane CL, a carcass 20 including at least one (1 in the example of the figure) carcass ply extends annularly. The carcass ply of the carcass 20 has a structure in which a cord made of steel, organic fiber, or the like is covered with rubber, for example. In the illustrated example, the carcass 20 includes: a main body 20a extending annularly between the pair of bead cores 60; and a pair of folded portions 20b folded back from the tire radial direction innermost end of the main portion 20a around the bead core 60 toward the tire widthwise outer side, respectively on both sides with respect to the tire equatorial plane CL. A belt 30 composed of at least one (3 in the example of the figure) belt layer is disposed on the tread portion 10' at a position on the outer side in the tire radial direction than the crown region of the carcass 20.

However, the unvulcanized tire 1 ' used in the method for manufacturing a pneumatic tire according to the present embodiment is not limited to the example shown in fig. 1, and may have any other structure as long as it includes at least the bead core 60 disposed in the bead portion 12 ' and the unvulcanized rubber 40 ' disposed on the inner side of the bead core 60 in the tire radial direction.

As shown in fig. 2A, the bead core 60 of the unvulcanized tire 1' has, when the tire width direction cross section is viewed, a bead bundle 62 and a covering 65 which surrounds the periphery of the bead bundle 62 and is composed of a resin material.

The bead wire bundle 62 of the bead core 60 is simply a structure in which a plurality of bead wires 62a constituting the bead core 60 appear in cross section when the tire width direction cross section is observed, and the actual number of the bead wires 62a constituting the bead core 60 may be 1 or a plurality of. That is, the bead wire harness 62 may be configured by winding 1 bead wire 62a in the tire circumferential direction by a plurality of turns, or may be configured by winding a plurality of bead wires 62a in the tire circumferential direction by 1 turn or a plurality of turns, respectively.

The bead wire 62a can use any known material, and for example, a steel cord can be used. The steel cord may be formed of, for example, steel monofilament or steel strand. In addition, organic fibers, carbon fibers, and the like can also be used.

The coating 65 of the bead core 60 continuously extends in the tire circumferential direction, and is configured in a ring shape so as to surround the bead bundle 62 of the bead core 60 over the entire circumference when the tire width direction cross section is observed in at least a part of the tire circumferential direction. The coating layer 65 may not be annular when viewed in a cross section in the tire width direction in a part in the tire circumferential direction, and may be, for example, C-shaped.

In this example, when the tire is viewed in a cross section in the tire width direction, each bead wire 62a is covered with a covering resin 63 made of a resin material on the inner side of the ring shape formed by the covering layer 65. In other words, the gap region between the coating layer 65 and each bead wire 62a is filled with the coating resin 63.

In this example, the resin material constituting the coating resin 63 is different from the resin material constituting the coating layer 65. However, the resin material constituting the coating resin 63 may be the same as the resin material constituting the coating layer 65.

Not limited to this example, each bead wire 62a may be covered with a covering rubber made of rubber instead of the covering resin 63 inside the ring shape formed by the covering layer 65 when the tire width direction cross section is viewed. In other words, the gap region between the covering layer 65 and each bead wire 62a may be filled with the covering rubber.

In this example, the bead filler 70 located on the outer side of the covering 65 of the bead core 60 in the tire radial direction is also made of a resin material, and more specifically, is made of the same resin material as the covering 65 integrally with the covering 65. However, the resin material constituting the bead filler 70 may be different from the coating 65 of the bead core 60. Further, the resin material constituting the bead filler 70 may be different for each portion of the bead filler 70. Alternatively, a part or the whole of the bead filler 70 may be made of rubber.

In the present specification, the "resin material" constituting the covering layer 65, the covering resin 63, the bead filler 70, and the like means a material different from rubber (an organic polymer substance exhibiting rubber elasticity at normal temperature). The "resin material" is a material that does not soften at all but can substantially (preferably completely) maintain its shape even at a high temperature used in the vulcanization step. The "resin material" is much harder (for example, one hundred times to several hundred times) than the rubber 40 constituting the tire 1 at normal temperature and lighter than the rubber 40 constituting the tire 1.

Specifically, as the "resin material", for example, a thermoplastic elastomer or a thermoplastic resin can be used, and a resin crosslinked by heat or an electron beam or a resin hardened by thermal transformation can be used. In view of the elasticity required for running, it is desirable to use a thermoplastic elastomer.

Examples of the thermoplastic elastomer include a polyolefin thermoplastic elastomer (TPO), a polystyrene thermoplastic elastomer (TPS), a polyamide thermoplastic elastomer (TPA), a polyurethane thermoplastic elastomer (TPU), a polyester thermoplastic elastomer (TPC), and a dynamically crosslinked thermoplastic elastomer (TPV).

Examples of the thermoplastic resin include a polyurethane resin, a polyolefin resin, a vinyl chloride resin, and a polyamide resin.

The "resin material" may be, for example, a material having a deflection temperature under load (under a load of 0.45 MPa) of 78 ℃ or higher as defined in ISO75-2 or ASTM D648, a tensile yield strength of 10MPa or higher as defined in JIS K7113, and a tensile elongation at break (JIS K7113) of 50% or higher as defined in JIS K7113. The tensile modulus of elasticity (defined in JIS K7113: 1995) of the "resin material" is preferably 50MPa or more, and more preferably 1000MPa or less. The softening point of the "resin material" is preferably higher than a predetermined vulcanization temperature used in the vulcanization process.

In the vulcanization step, the unvulcanized tire 1' obtained in the assembly molding step is vulcanized in a vulcanization mold 200.

As shown in fig. 1, the inner surface of the vulcanizing mold 200 forms a tire outer surface molding surface 220 configured to mold the outer surface of the tire 1. More specifically, the vulcanizing mold 200 includes a plurality of vulcanizing mold portions 210, 211, 212, and the inner surfaces of the respective vulcanizing mold portions 210, 211, 212 constitute a part of the tire outer surface forming surface 220. In the illustrated example, the vulcanizing mold 200 has: a tread vulcanizing mold portion 210 configured to shape an outer surface of the tread portion 10 of the tire 1; a sidewall vulcanizing mold portion 211 configured to mold an outer surface of the sidewall portion 11 and an outer surface of a part of the bead portion 12 of the tire 1; and a bead vulcanization mold portion 212 configured to shape an outer surface of a remaining portion of the bead portion 12 of the tire 1. However, the vulcanizing mold 200 is not limited to the illustrated example, and may be formed of any plurality of vulcanizing mold sections. In a state where the vulcanizing mold portions 210, 211, 212 are closed to each other, the tire outer surface forming surface 220 divides the cavity C200.

The tire outer surface forming surface 220 includes, at the innermost side in the tire radial direction, a bead bottom forming surface 221 configured to form the bead bottom 121 of the tire 1. In the illustrated example, the bead vulcanization mold portion 212 has a bead bottom forming surface 221.

As shown in fig. 3, the bead bottom portion 121 of the tire 1 is a surface facing the tire radial direction inner side, which is located on the tire radial direction innermost side, of the outer surface of the tire 1. The bead bottom portion 121 of the tire 1 is a portion that comes into contact with the bead seat Rbs of the rim R in a state where the tire 1 is assembled to the rim R.

As shown in fig. 1 and 2A, during the vulcanization step, the unvulcanized tire 1 'is disposed in the cavity C200 of the vulcanization mold 200, and vulcanization and molding are performed at a predetermined temperature while being pressed against the tire outer surface molding surface 220 by the bladder 230 disposed on the tire inner cavity side of the unvulcanized tire 1'.

During the vulcanization process, the tire constituent member made of the resin material (in this example, the covering 65 and the covering resin 63 of the bead core 60, and the bead filler 70) is hardly (preferably completely) deformed and moved, but substantially (preferably completely) maintains the shape and position. On the other hand, during the vulcanization step, the unvulcanized rubber 40' flows in the cavity C200, and thereafter, is vulcanized while forming the tire outer surface by the tire outer surface forming surface 220.

After the vulcanization step, the vulcanized pneumatic tire 1 is obtained (fig. 2B and 3).

In the method of manufacturing a pneumatic tire according to the present embodiment, as shown in fig. 2A, in the vulcanization step, the positional relationship between the inner surface 651 in the tire radial direction of the bead core 60 and the bead bottom molding surface 221 is maintained such that the tire radial direction distance L1 (hereinafter, also referred to as "1 st distance L1") between the inner surface 651 in the tire radial direction of the covering layer 65 of the bead core 60 and the bead bottom molding surface 221 of the vulcanization mold 200 is kept constant or gradually decreased toward the inner side in the tire width direction in at least a part of the tire width direction region.

As shown in fig. 2B, in the pneumatic tire 1 of the present embodiment obtained through the vulcanization step, the positional relationship between the inner surface 651 of the bead core 60 in the tire radial direction and the bead bottom portion 121 is set so that the tire radial direction distance L2 (hereinafter, also referred to as "2 nd distance L2") between the inner surface 651 of the covering layer 65 of the bead core 60 in the tire radial direction and the bead bottom portion 121 is constant or gradually decreased toward the inner side in the tire width direction in at least a part of the tire width direction region. The positional relationship between the tire radial direction inner side surface 651 of the bead core 60 and the bead bottom portion molding surface 221 in the vulcanization step and the positional relationship between the tire radial direction inner side surface 651 of the covering 65 and the bead bottom portion 121 in the tire 1 obtained after the vulcanization step are substantially (preferably completely) the same. Meanwhile, the thickness of the rubber 40 in the tire radial direction between the surface 651 on the tire radial direction inner side of the covering 65 of the bead core 60 and the bead bottom portion 121 is kept constant or gradually reduced toward the tire width direction inner side in at least a part of the tire width direction area.

According to the present embodiment, in a state (fig. 3) where the tire 1 obtained after manufacturing is assembled to the rim R, the compression ratio of the rubber 40 between the surface 651 on the inner side in the tire radial direction of the bead core 60 and the bead seat Rbs of the rim R can be improved mainly more than in the conventional case on the inner side in the tire width direction, and further the fitting force between the bead portion 12 of the tire 1 and the rim R can be improved, and the fitting force can be improved as a whole. This improves the adhesion between the bead portion 12 of the tire 1 and the rim R, and improves the tire running performance and the fluid tightness.

Further, according to the present example, since the covering layer 65 of the bead core 60 surrounding the bead bundle 62 is made of a resin material which hardly softens even in the vulcanization step, it is possible to significantly suppress the change in the shape of the bead core 60 in the vulcanization step and maintain the positional relationship between the surface 651 of the bead core 60 on the inner side in the tire radial direction and the bead bottom molding surface 221 in a desired positional relationship, compared to a case where the bead core 60 is not made of a resin material and the bead bundle 62 is covered with only rubber, for example. Thus, the positional relationship between the surface 651 of the bead core 60 on the inner side in the tire radial direction and the bead bottom portion 121 can be set to a desired positional relationship with respect to the tire 1 obtained after manufacture.

Further, according to the present example, since the covering layer 65 of the bead core 60 surrounding the periphery of the bead bundle 62 is made of a resin material that is much harder than rubber and less likely to deteriorate than rubber, it is possible to significantly suppress the collapse of the shape of the bead core 60 due to the carcass 20 being pulled outward in the tire radial direction by the action of the bladder 230 during manufacture, as compared to a case where the bead core 60 is not made of a resin material and the bead bundle 62 is covered with only rubber, for example. Thereby, the positional relationship between the inner surface 651 of the bead core 60 in the tire radial direction and the bead bottom molding surface 221 can be maintained at a desired positional relationship. In addition, it is also possible to significantly suppress the collapse of the shape of the bead core 60 due to long-term use of the tire 1 obtained after manufacture. As a result, even after long-term use, the tire 1 can maintain high adhesion between the bead portion 12 and the rim R, and can maintain good tire running performance and liquid tightness. Alternatively, the bead core 60 can be miniaturized while maintaining the durability of the bead core 60 at the same level as in the conventional art.

Further, according to the present example, since a part of the bead core 60 is made of a resin material lighter than rubber, for example, as compared with a case where the bead core 60 is not made of a resin material and the bead bundle 62 is covered with only rubber, it is possible to achieve weight reduction of the tire 1, and further, reduction in rolling resistance and fuel consumption.

Further, according to the present example, since the respective bead wires 62a are covered with the covering resin 63 on the inner side of the covering layer 65 of the bead core 60, for example, compared with the case where the respective bead wires 62a are covered with the covering rubber on the inner side of the covering layer 65 of the bead core 60, the shape of the bead core 60 can be more reliably maintained at the time of manufacture and use, the durability of the bead core 60 can be further improved, and the weight reduction and the size reduction of the tire 1 can be further achieved.

In addition, in this example, since the bead filler 70 is also made of a resin material, durability of the tire 1 can be further improved and weight reduction and size reduction of the tire 1 can be further achieved as compared with a case where the bead filler 70 is made of rubber.

In the example shown in fig. 2A and 2B, when the tire width direction cross section is viewed, the corner portions 65a, 65B of the covering layer 65 located on the inner side in the tire radial direction on both sides in the tire width direction have a rounded shape (curved shape), respectively.

As described above, when the tire width direction cross section is viewed, at least one of the corner portions 65a, 65b of the covering layer 65 located on the inner side in the tire radial direction on both sides in the tire width direction preferably has a rounded shape or a chamfered shape.

If the corners 65a, 65b are not rounded or chamfered but have angular shapes, tire components (the carcass 20, rubber) in the vicinity of the corners 65a, 65b on the inner side in the tire radial direction of the coating layer 65 may be damaged by sharp tips of the corners 65a, 65b when the carcass 20 is pulled outward in the tire radial direction by the bladder 230 during tire manufacturing, when a load is applied to the tire 1 during use of the tire 1, or the like. At least one of the corner portions 65a, 65b has a rounded shape or a chamfered shape, and thus damage to the tire constituent member in the vicinity of the corner portions 65a, 65b due to the corner portions 65a, 65b can be effectively suppressed. This can improve the durability of the tire 1.

However, the corners 65a, 65b of the covering layer 65 located on the inner side in the tire radial direction on both sides in the tire width direction may have an angular shape.

Here, as described above, when at least one of the corners 65a, 65b of the covering layer 65 located on the tire radial direction inner side on both sides in the tire width direction has the rounded shape or the chamfered shape when viewing the tire width direction cross section, in the present specification, the "surface 651 of the covering layer 65 on the tire radial direction inner side" does not include the corners 65a, 65b having the rounded or chamfered shape, that is, the tire radial direction innermost ends of the corners 65a, 65b having the rounded or chamfered shape are set as the ends of the "surface 651 of the covering layer 65 on the tire radial direction inner side" in the tire width direction.

For example, in the example of fig. 2A and 2B, the "surface 651 on the inner side of the covering layer 65 in the tire radial direction" is a surface between the innermost ends of the corner portions 65a, 65B on both sides in the tire width direction, which have a rounded shape, in the tire radial direction.

In the example shown in fig. 2A, in the vulcanization step, the surface 651 on the inner side in the tire radial direction of the covering 65 of the bead core 60 and the bead bottom molding surface 221 of the vulcanization mold 200 gradually extend inward in the tire radial direction as they go inward in the tire width direction.

In the tire 1 of the example of fig. 2B obtained through the above-described vulcanization step, the surface 651 on the inner side in the tire radial direction of the covering 65 of the bead core 60 and the bead bottom portion 121 each gradually extend inward in the tire radial direction toward the inner side in the tire width direction.

This can further improve the fitting force between the bead portion 12 and the rim R of the tire 1.

However, the present invention is not limited to this example, and the surface 651 on the inner side in the tire radial direction of the covering 65 of the bead core 60, the bead bottom molding surface 221 of the vulcanizing mold 200, and the bead bottom 121 of the tire 1 may extend in any direction toward the inner side in the tire width direction.

In the example of fig. 2A, the surface 651 on the inner side in the tire radial direction of the covering 65 of the bead core 60 gradually extends inward in the tire radial direction as it goes inward in the tire width direction. In this case, if it is assumed that the corner portion 65a on the inner side in the tire width direction and on the inner side in the tire radial direction in the coating layer 65 does not have a rounded or chamfered shape, the tip of the corner portion 65a may be excessively sharp. Therefore, at least the corner portion 65a of the coating layer 65 that is the tire width direction inner side and the tire radial direction inner side preferably has a rounded shape or a chamfered shape.

Thus, for example, when a load is applied to the tire, damage to the tire constituent member in the vicinity of the corner portion 65a of the coating layer 65 due to the corner portion 65a can be effectively suppressed.

In the example shown in fig. 2A, in the vulcanization step, when the tire width direction cross section is viewed, the surface 651 of the covering layer 65 on the inner side in the tire radial direction and the bead bottom molding surface 221 of the vulcanization mold 200 extend linearly in parallel with each other. The 1 st distance L1 is constant over the entire tire width direction area of the surface 651 of the cover 65 on the inner side in the tire radial direction, toward the inner side in the tire width direction.

In the tire 1 of the example of fig. 2B obtained through the vulcanization step, when the tire width direction cross section is viewed, the surface 651 on the inner side in the tire radial direction of the covering layer 65 and the bead bottom portion 121 extend linearly in parallel to each other. The 2 nd distance L2 is kept constant toward the inner side in the tire width direction over the entire tire width direction area of the surface 651 on the inner side in the tire radial direction of the cover 65. Meanwhile, the thickness of the rubber 40 in the tire radial direction between the tire radial direction inner side face 651 of the covering 65 of the bead core 60 and the bead bottom portion 121 is kept constant toward the tire width direction inner side over the entire region in the tire width direction of the tire radial direction inner side face 651 of the covering 65.

In the case of the example of fig. 2A and 2B, since the 2 nd distance L2 is kept constant over the entire region in the tire width direction of the surface 651 on the inner side in the tire radial direction of the cover 65 of the tire 1 after manufacture, the fitting force between the bead portion 12 and the rim R can be made substantially uniform in the tire width direction in the state where the tire 1 is assembled to the rim R. This can improve the fitting force between the bead portion 12 and the rim R.

However, the present invention is not limited to this example, and the surface 651 on the inner side in the tire radial direction of the covering 65 of the bead core 60, the bead bottom molding surface 221 of the vulcanizing mold 200, and the bead bottom 121 of the tire 1 may each extend along any non-linear shape when the tire width direction cross section is viewed, and may extend along a curved shape, a wavy shape, a bent shape that is bent at 1 or more portions, or the like. When the tire width direction cross section is observed, the shape of the surface 651 on the inner side in the tire radial direction of the covering 65 of the bead core 60, the shape of the bead bottom molding surface 221, and the shape of the bead bottom 121 may be different from each other.

Fig. 4A and 4B show a 1 st modification of the present invention, and correspond to fig. 2A and 2B, respectively.

In the example shown in fig. 4A, in the vulcanization step, when the tire width direction cross section is viewed, the inclination angle θ c of the surface 651 on the tire radial direction inner side of the covering layer 65 with respect to the tire radial direction (where θ c ≦ 90 °) is smaller than the inclination angle θ m of the bead bottom portion molding surface 221 with respect to the tire radial direction (where θ m ≦ 90 °) (that is, θ c < θ m). The 1 st distance L1 gradually decreases toward the tire width direction inner side over the entire tire width direction area of the surface 651 of the cover 65 on the tire radial direction inner side. The other structure is the same as the example of fig. 2A.

In the tire 1 of the example of fig. 4B obtained through the vulcanization step, when the tire width direction cross section is viewed, the inclination angle θ c of the surface 651 on the inner side of the covering layer 65 in the tire radial direction with respect to the tire radial direction is smaller than the inclination angle θ r of the bead bottom portion 121 with respect to the tire radial direction (where θ r is less than or equal to 90 °) (that is, θ c < θ r). The 2 nd distance L2 gradually decreases toward the tire width direction inner side over the entire tire width direction area of the surface 651 of the cover 65 on the tire radial direction inner side. Meanwhile, the thickness of the rubber 40 in the tire radial direction between the tire radial direction inner side surface 651 of the covering 65 of the bead core 60 and the bead bottom portion 121 is gradually reduced toward the tire width direction inner side over the entire region in the tire width direction of the tire radial direction inner side surface 651 of the covering 65. The other structure is the same as the example of fig. 2B.

In the case of the 1 st modification of fig. 4A and 4B, since the 2 nd distance L2 gradually decreases toward the tire width direction inner side over the entire tire width direction region of the surface 651 on the tire radial direction inner side of the cover 65 in the tire 1 after manufacture, the fitting force between the bead portion 12 and the rim R can be increased particularly on the tire width direction inner side as compared with the tire width direction outer side in a state where the tire 1 is assembled to the rim R, and the fitting force between the bead portion 12 and the rim R can be further increased.

In this example, as shown in the drawing, it is particularly preferable that at least a corner portion 65a on the inner side in the tire width direction and the inner side in the tire radial direction in the coating layer 65 has a rounded shape or a chamfered shape.

Fig. 5A and 5B show a 2 nd modification of the present invention, and correspond to fig. 2A and 2B, respectively.

In the 2 nd modification shown in fig. 5A and 5B, as in the example of fig. 2A and 2B, the surface 651 on the inner side in the tire radial direction of the covering 65 of the bead core 60 gradually extends inward in the tire radial direction as it goes inward in the tire width direction. In this case, if it is assumed that the corner portion 65a on the inner side in the tire width direction and on the inner side in the tire radial direction in the coating layer 65 does not have a rounded or chamfered shape, the tip of the corner portion 65a may be excessively sharp. Therefore, in this example, when the tire width direction cross section is observed, the radius of curvature of the rounded shape (curved shape) formed by the corner portion 65a of the covering layer 65 on the tire width direction inner side and the tire radial direction inner side is larger than the radius of curvature of the rounded shape formed by the corner portion 65b on the tire width direction outer side and the tire radial direction inner side. The other structure is the same as the example of fig. 2A and 2B. In the example of fig. 2A and 2B, when the tire width direction cross section is viewed, the radius of curvature of the rounded shape formed by the corner 65a of the coating layer 65 on the inner side in the tire width direction and on the inner side in the tire radial direction is the same as or smaller than the radius of curvature of the rounded shape formed by the corner 65B on the outer side in the tire width direction and on the inner side in the tire radial direction.

In the case of the 2 nd modification example of fig. 5A and 5B, it is possible to more effectively suppress damage to the tire constituent member in the vicinity of the corner portion 65A of the covering layer 65 due to the corner portion 65A, for example, when a load is applied to the tire, as compared with the example of fig. 2A and 2B.

Fig. 6A and 6B show a 3 rd modification of the present invention, and correspond to fig. 2A and 2B, respectively.

In the modification 3 shown in fig. 6A, in the vulcanization step, when the tire width direction cross section is viewed, the surface 651 on the inner side in the tire radial direction of the covering layer 65 and the bead bottom molding surface 221 of the vulcanization mold 200 extend along curved shapes that are convex inward in the tire radial direction, respectively. The 1 st distance L1 is constant over the entire tire width direction area of the surface 651 of the cover 65 on the inner side in the tire radial direction, toward the inner side in the tire width direction.

In the tire 1 of the example of fig. 6B obtained through the vulcanization step, when the tire width direction cross section is viewed, the surface 651 on the inner side in the tire radial direction of the covering layer 65 and the bead bottom portion 121 each extend along a curved shape that is convex inward in the tire radial direction. The 2 nd distance L2 is kept constant toward the inner side in the tire width direction over the entire tire width direction area of the surface 651 on the inner side in the tire radial direction of the cover 65. Meanwhile, the thickness of the rubber 40 in the tire radial direction between the tire radial direction inner side face 651 of the covering 65 of the bead core 60 and the bead bottom portion 121 is kept constant toward the tire width direction inner side over the entire region in the tire width direction of the tire radial direction inner side face 651 of the covering 65.

In the case of the 3 rd modification of fig. 6A and 6B as well, the fitting force between the bead portion 12 and the rim R can be made substantially uniform in the tire width direction, as in the case of the example of fig. 2A and 2B. This can improve the fitting force between the bead portion 12 and the rim R.

In the vulcanization step, the 1 st distance L1 may be constant or gradually decreased toward the tire width direction inner side only in a part of the tire width direction region, without being limited to the examples described above. The 2 nd distance L2 of the pneumatic tire 1 may be constant or gradually decreased toward the inner side in the tire width direction only in a part of the tire width direction region. In this case as well, the fitting force between the bead portion 12 and the rim R of the tire 1 can be improved more than in the conventional case.

However, in this case, as in the above-described examples, it is preferable that the 1 st distance L1 be constant or gradually decreased toward the tire width direction inner side at least in the tire width direction region across the tire width direction center CCP of the bead core 60 in the vulcanization step. Similarly, as in the above-described examples, in the pneumatic tire 1 after manufacture, it is preferable that the 2 nd distance L2 be constant or gradually decreased toward the tire width direction inner side at least in the tire width direction region across the tire width direction center CCP of the bead core.

Here, the "tire width direction center CCP of the bead core 60" is a tire width direction position in the middle of the tire width direction innermost end and the tire width direction outermost end of the bead core 60 in the tire width direction cross section.

Accordingly, the fitting force between the bead portion 12 of the tire 1 and the rim R can be made equal to or greater than the tire width direction inner side of the bead core 60 and the tire width direction outer side of the bead core 60, and the fitting force can be effectively improved as a whole.

As in the example of fig. 2A, 4A, 5A, and 6A, in the vulcanization step, the minimum value of the 1 st distance L1 on the inner side in the tire width direction with respect to the tire width direction center CCP of the bead core 60 is preferably equal to (corresponding to the example of fig. 2A, 5A, and 6A) or shorter than (corresponding to the example of fig. 4A) the minimum value of the 1 st distance L1 on the outer side in the tire width direction with respect to the tire width direction center CCP of the bead core 60.

Similarly, in the pneumatic tire 1 after manufacture, the minimum value of the 2 nd distance L2 on the inner side in the tire width direction with respect to the tire width direction center CCP of the bead core 60 is equal to or shorter than the minimum value of the 2 nd distance L2 on the outer side in the tire width direction with respect to the tire width direction center CCP of the bead core 60 (equivalent to the example of fig. 2B, 5B, and 6B) (equivalent to the example of fig. 4B).

Accordingly, the fitting force between the bead portion 12 of the tire 1 and the rim R can be made equal to or greater than the tire width direction inner side of the bead core 60 and the tire width direction outer side of the bead core 60, and the fitting force can be effectively improved as a whole.

Here, a preferred example of the bead core manufacturing process for manufacturing the bead core 60 will be described in detail with reference to fig. 7A and 7B. The bead core manufacturing process of this example is used to manufacture the core filler member 50 shown in fig. 2A and 2B. However, in the present invention, the bead core 60 may be manufactured by a different bead core manufacturing process from the present example.

The manufacturing process of the bead core of the present example includes an annular body forming process, an injection molding process, and a cooling process. Fig. 7A shows a state of the injection molding process, and fig. 7B shows a core/filler member 50 obtained in the bead core manufacturing process.

Although not shown, in the annular body forming step, the band member 64 in which 1 or more bead wires 62a are coated with the coating resin 63 is wound to form the annular body 61. The annular body 61 shown in fig. 7A is formed by winding a strip member 64 in a spiral shape, for example, in which 1 or more (3 in the illustrated example) bead wires 62a are covered with a covering resin 63, and 3 layers of the strip member 64 having a substantially rectangular shape in a cross section in the axial direction of the annular body 61 are stacked in the radial direction of the annular body 61. Here, the "axial direction of the annular body 61" refers to a direction parallel to the central axis of a substantially circular ring shape (spiral shape) formed by the annular body 61. In this example, the number of bead wires 62a arranged in the axial direction of the annular body 61 is 3, but the present invention is not particularly limited thereto, and the number of bead wires 62a may be 1 or more.

In this example, in the annular body forming step, the band member 64 is formed by coating the molten coating resin 63 on the outer peripheral side of the bead wire 62a and solidifying the coating resin by cooling. The cross-sectional shape of the strip member 64 (the shape of the cross-section orthogonal to the extending direction of the bead wire 62 a) is substantially rectangular in this example, but is not limited to this example, and various shapes such as a substantially parallelogram shape can be adopted. The sectional shape of the strip member 64 can be formed into a desired shape using an extruder, for example. The annular body 61 can be formed by winding and laminating the strip members 64, and for example, the strip members 64 can be wound while melting the coating resin 63 by hot plate welding or the like, and the melted coating resin 63 can be solidified to bond the layers. Alternatively, the layers may be bonded to each other by using an adhesive or the like.

Next, in the annular body forming step, the annular body 61 formed in the annular body forming step is coated with a resin material in the injection molding step, thereby forming the covering layer 65 and the bead filler 70 integrated with the covering layer 65. Specifically, as shown in fig. 7A, the annular body 61 formed in the annular body forming step is disposed in the cavity C300 of the injection mold 300, and the injection resin melted by heating is injected from a gate (not shown) into the cavity C300. During this time, the ring body 61 can be fixed to a predetermined position in the cavity C300 by a jig not shown.

In this example, the inner surface of the injection mold 300 forms a molding surface 320 configured to mold the outer surface of the core/underfill member 50. More specifically, the injection mold 300 includes a plurality of injection mold portions 310 and 311, and the inner surfaces of the injection mold portions 310 and 311 constitute a part of the molding surface 320. The molding surface 320 of the injection mold 300 has a cover molding surface 321 configured to mold the outer surface of the cover 65 of the bead core 60 and a filler molding surface 322 configured to mold the outer surface of the bead filler 70.

Next, in the injection molding step, the coating layer 65 and the bead filler 70 are solidified by cooling. After the cooling step, the completed core/underfill member 50 is taken out of the injection mold 300. As shown in fig. 7B, the bead core 60 of the core/filler member 50 is configured such that the annular body 61 is covered with a covering layer 65 obtained by solidifying the periphery of the annular body 61. Further, the bead filler 70 is integrally formed with the covering layer 65 at the radially outer side of the covering layer 65.

According to the method for manufacturing a bead core of the present example, the laminated annular body 61 receives a force of thermal shrinkage caused by the clad 65 injected around the laminated annular body in the cooling step. This enables the annular body 61 to be fastened by the surrounding covering 65. The bead core 60 is configured such that the periphery of the annular body 61 is covered with the cured coating 65. Therefore, the peripheral cured coating layer 65 can protect the annular body 61 against external force such as lateral force of the tire, and in addition, can be fastened by the peripheral cured coating layer 65, thereby suppressing collapse of the shape of the annular body 61. Thereby, the bead core 60 having high durability can be obtained.

In addition, in this example, since the bead filler 70 is molded together with the covering 65, a manufacturing process for separately providing the bead filler 70 is not required, and the bead core 60 and the bead filler 70 can be handled as one component in an assembling process for assembling with other tire constituent members, so that the manufacturability can be improved.

However, as described above, the bead filler 70 may not be manufactured in the bead core manufacturing step, and in this case, the injection mold 300 used in the injection molding step may be configured to omit the filler molding surface 322. In this case, the bead filler 70 made of a resin material may be manufactured by injection molding and bonded to the covering 65 of the bead core 60 by welding, an adhesive, or the like.

From the viewpoint of more easily obtaining the bead core 60 having high durability, the covering layer 65 is preferably made of the same resin material as the covering resin 63. This is because the coating layer 65 and the coating resin 63 are easily welded or bonded.

On the other hand, from the viewpoint of easy adjustment of the hardness of the bead core 60, the coating layer 65 is preferably made of a resin material different from the coating resin 63. Here, as described above, the "resin material" in the present specification has a hardness greater than that of the rubber 40. Therefore, in order to be able to alleviate the difference in rigidity between the bead core 60 and the surrounding rubber 40, the coating layer 65 directly adjacent to the rubber 40 is preferably lower in hardness than the coating resin 63 (closer to the hardness of the rubber 40).

On the other hand, in order to further obtain the effect of heat shrinkage, the hardness of the coating layer 65 is preferably higher than that of the coating resin 63.

Alternatively, the coating layer 65 is preferably made of a resin material having high adhesiveness to the rubber 40.

Industrial applicability

The method for manufacturing a pneumatic tire and the pneumatic tire according to the present invention can be used for any type of pneumatic tire such as a passenger vehicle pneumatic tire.

Description of the reference numerals

1': unvulcanized tire (tire), 1: pneumatic tire (tire), 10', 10: tread portion, 11', 11: sidewall portions, 12', 12: bead portion, 20: carcass, 20 a: body portion, 20 b: folded-back portion, 30: belt, 40': unvulcanized rubber, 40: rubber, 50: core-filler member, 60: bead core, 61: annular body, 62 a: bead wire, 62: bead wire harness, 63: coating resin, 64: strip member, 65: coating layer, 65a, 65 b: corner, 70: bead filler, 121: bead bottom, 200: vulcanization mold, 210, 211, 212: vulcanization mold portion, 220: tire outer surface molding surface, 221: bead bottom molding surface, 230: an air bag, 300: injection molding die, 310, 311: injection molding mold portion, 320: molding surface, 321: coating layer forming surface, 322: molding surface with filling, 651: surface of the coating layer on the inner side in the tire radial direction, C200, C300: mold cavity, CCP: tire width direction center of bead core, CL: tire equatorial plane, L1: tire radial distance (1 st distance), L2: tire radial distance (2 nd distance), R: rim, Rbs: and a bead seat.