JP2016049664A - Rigidity strengthening ring, and tire vulcanization method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire vulcanization method by bladderless vulcanization for improving productivity, while improving the inner surface shape of a pneumatic tire and heightening dimensional accuracy.SOLUTION: In a bladderless vulcanization method in which a green tire T is set in a metal mold 1, and a heating medium M is press-fitted to the inside of the green tire T and pressed to the outside in the tire radial direction, the heating medium M is press-fitted in the state where a rigidity strengthening ring 2 is arranged on the whole area on the inside surface of a region corresponding to a range from a tread part T1 to a bead part T3 of the green tire T.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an annular member used for bladderless vulcanization of a pneumatic tire and a tire vulcanization method using the same.

  As a method for vulcanization molding of a pneumatic tire, a vulcanization molding method in which a heating medium is press-fitted inside the green tire after setting a green tire inside a mold, so-called bladderless vulcanization is known (for example, (See Patent Documents 1 and 2).

  However, in bladderless vulcanization, in the region where the thickness of the green tire is thick, sufficient pressure on the mold cannot be obtained, so the applicable tire shape is limited, and the inner surface shape and dimensional accuracy of the vulcanized tire There was a problem of shortage. For this reason, there has been a demand for a vulcanization method for bladderless vulcanizing a pneumatic tire so as not to deteriorate the inner shape and dimensional accuracy of the vulcanized tire while ensuring excellent productivity of the bladderless vulcanization.

JP 2001-260135 A JP 2009-208394 A

  An object of the present invention is to provide a tire vulcanization method by bladderless vulcanization which improves the productivity while improving the inner surface shape of a pneumatic tire and improving the dimensional accuracy.

  The rigidity-enhanced ring of the present invention that achieves the above object is characterized in that when a green tire is set in a mold, a heating medium is press-fitted inside the green tire and pressed outwardly in the tire radial direction to perform bladderless vulcanization. The ring is arranged so as to contact the entire inner surface of the region corresponding to the bead portion from the tread portion of the tire, and is required to cause a predetermined amount of tensile deformation in the circumferential direction in the tread portion and the bead portion of the ring. The stress is greater than the stress required to cause a predetermined amount of compressive deformation in the circumferential direction.

  The tire vulcanization method of the present invention is a bladderless vulcanization method in which a green tire is set in a mold, a heating medium is press-fitted inside the green tire, and is pressed outward in the tire radial direction. The heating medium is press-fitted in a state where the above-described rigidity reinforcing ring is arranged over the entire inner surface of the region corresponding to the bead portion from the tread portion.

  According to the rigidity-enhanced ring of the present invention and the tire vulcanizing method using the same, the tensile stress in the circumferential direction is applied in the circumferential direction so as to contact the entire inner surface of the region corresponding to the bead portion from the green tire tread portion. Since the rigidity-enhanced ring larger than the compressive stress is disposed and bladderless vulcanized, the rigidity-enhanced ring improves the tire inner surface shape and increases the dimensional accuracy. Further, since it is only necessary to dispose the rigidity reinforcing ring on the inner peripheral surface of the green tire, it is possible to maintain good productivity of the bladderless vulcanization.

  The rigid reinforcing ring may be a ring obtained by covering a reinforcing body in which a reinforcing wire having a twisted structure is wound at least in the tire circumferential direction at the tread portion and the bead portion with an unvulcanized rubber and vulcanizing the reinforcing body. This increases the tensile stress in the circumferential direction of the rigid reinforcing ring, reduces the compressive stress in the circumferential direction, and allows the rigid reinforcing ring to be easily removed from the vulcanized molded pneumatic tire for repeated use in bladderless vulcanization. be able to.

  In the bead portion, a plurality of reinforcing wires that are the same as or different from the reinforcing wire having the twisted structure may be arranged at intervals in the tire circumferential direction so as to extend in the tire radial direction. it can. Thereby, shaping to the bead portion can be stabilized, and the inner surface shape and dimensional stability of the tire can be further improved.

  In the tire vulcanizing method of the present invention, a green tire assembly is produced by integrally assembling the components of the green tire on the outer periphery of the rigidity reinforcing ring, and the green tire assembly is set in a mold, and the innermost The heating medium can be press-fitted inside the rigid reinforcing ring. The green tire assembly may be set inside a mold that can be divided into a plurality of parts.

  The tire vulcanization method of the present invention can produce a high-quality pneumatic tire stably and at low cost with high dimensional accuracy by bladderless vulcanization of a green tire using the above-described rigid reinforcing ring.

It is explanatory drawing which shows typically an example of embodiment of the bladderless vulcanization | cure of the tire which uses the rigidity reinforcement ring of this invention in a meridian direction cross section. (A) (b) is explanatory drawing which shows typically an example of embodiment of the rigidity reinforcement ring of this invention, (a) is a perspective view of a rigidity reinforcement ring, (b) is the rigidity reinforcement of (a). It is a perspective view which removes and shows a part of surface of a ring. It is explanatory drawing equivalent to FIG.2 (b) which shows in another example of embodiment of the rigidity reinforcement ring of this invention.

  Hereinafter, the rigid reinforcement ring of this invention is demonstrated based on embodiment shown in the figure.

  FIG. 1 is an explanatory view schematically showing a mold 1, a rigid reinforcing ring 2 and a green tire T during bladderless vulcanization. FIG. 1 shows a state in which the green tire T is pressed against the inner surface of the mold 1 by press-fitting the heating medium M. The green tire T includes a tread portion T1, a side portion T2, and a bead portion T3.

  In the present invention, the green tire T is formed in a shape close to the shape of the tire after vulcanization, and the rigidity is enhanced so as to contact the entire inner surface of the region corresponding to the bead portion T2 from the tread portion T1 of the green tire T. Ring 2 is arranged. In the tread portion and the bead portion, the rigidity reinforcing ring 2 has a stress required to cause a predetermined amount of tensile deformation in the circumferential direction larger than a stress required to cause a predetermined amount of compressive deformation in the circumferential direction. That is, the rigidity reinforcing ring 2 has a property that it is difficult to extend in the tire circumferential direction and is easily compressed. The rigidity reinforcing ring 2 is airtight under high temperature and high pressure, and vulcanizes the green tire by pressing it against the inner surface of the mold on the outer side in the tire radial direction by a heating medium press-fitted at the time of bladderless vulcanization.

  By arranging the rigid reinforcing ring 2 during the bladderless vulcanization, the shape inside the tire can be improved. Moreover, the dimensional accuracy of the tire in the area | region corresponded from a tread part to a bead part can be made high.

  The rigidity reinforcing ring 2 has a feature that a circumferential compressive stress is small in addition to a large tensile stress in the circumferential direction. In the initial stage of tire vulcanization molding, vulcanization of rubber such as carcass and belt layer close to the tire inner surface proceeds, and vulcanization of the entire tire cross section including the inside of the tire proceeds after the next intermediate stage. As the vulcanization of the unvulcanized rubber proceeds, the volume of the rubber increases due to thermal expansion. For this reason, when vulcanization of the entire tire cross section proceeds after the middle stage, the vulcanized rubber close to the tire inner surface where vulcanization has progressed in the initial stage due to thermal expansion, the circumference of the tire lumen shrinks, Deforms radially inward. Therefore, the rigidity-enhanced ring 2 whose circumference has been enlarged at the initial stage of vulcanization molding needs to have a circumference reduced after the middle stage. Since the rigidity-enhanced ring 2 of the present invention has a small circumferential compressive stress, it can follow the behavior of the vulcanized rubber after the middle stage and can prevent failure such as buckling.

  The shape of the rigidity reinforcing ring 2 of the present invention is not particularly limited as long as it is a ring that contacts the entire inner surface of the region corresponding to the bead portion from the tread portion of the green tire. Preferably, it is a cylindrical ring in the region that contacts the inside of the tread portion T1, and a hollow frustoconical ring that opens on both sides in the region that contacts the inside of the bead portion T2 from the side portion T2.

  2 (a) and 2 (b) are explanatory views schematically showing an example of an embodiment of the rigid reinforcing ring 2 of the present invention. As shown in FIG. 2, the rigidity-enhanced ring 2 has a shape in which a ring having a reduced diameter on both sides of a cylindrical shape, that is, a cylindrical ring and a hollow frustoconical ring connected to both sides thereof are combined. Although the dimension of the rigidity reinforcement ring 2 is not specifically limited, It is good that the outer diameter is substantially equivalent to the internal diameter of the vulcanized tire. Thereby, the shape inside the radial direction of the area | region corresponded to a bead part from the tread part of a tire can be adjusted.

  2A illustrates the cylindrical rigid reinforcing ring 2 in which the outer diameter of the region corresponding to the tread portion is constant in the tire width direction, the outer diameter of the tread portion of the rigid reinforcing ring 2 is illustrated. It is not limited to examples. For example, when manufacturing a pneumatic tire in which the inner peripheral edge of the tread portion is linear, the rigid reinforcing ring 2 illustrated in FIG. 2A can be used as it is. On the other hand, when manufacturing a pneumatic tire in which the inner peripheral edge of the tread portion is designed in an arc shape, the outer diameter of the rigidity reinforcing ring 2 can be changed in the tire width direction along the designed arc. The same can be applied to the region from the side portion to the bead portion. In other words, the shape of the rigidity reinforcing ring 2 may be determined according to the cross-sectional shape of the designed tire. Thereby, the design freedom of a tire can be made higher.

  The structure of the rigid reinforcing ring 2 is not particularly limited as long as the tensile stress in the circumferential direction is larger than the compressive stress. As the rigidity reinforcing ring 2, for example, as shown in FIG. 2B, a reinforcing body in which a reinforcing wire 3 having a twisted structure is wound at least in the tire circumferential direction in the tread portion T1 and the bead portion T3 is unvulcanized. A ring coated with rubber 4 and vulcanized is preferred. By making the rigidity reinforcing ring 2 a structure in which the reinforcing wire 3 is embedded in the tread portion T1 and the bead portion T3, the tensile stress in the circumferential direction can be increased and the compressive stress in the circumferential direction can be reduced. Further, since the rigid reinforcing ring 2 is a ring made of vulcanized rubber, it does not adhere to the unvulcanized rubber or the vulcanized rubber, so that it is easily peeled off from the inside of the vulcanized tire taken out from the mold 1 and taken out. be able to.

  The reinforcing body is formed by spirally winding in the tire circumferential direction while applying an appropriate tension to the reinforcing wire 3 in a region corresponding to the tread portion T1 and the bead portion T3. The driving density of the reinforcing wire 3 can be determined according to the tensile stress in the circumferential direction, and the driving density may be the same or different between the tread portion T1 and the bead portion T3.

  As illustrated in FIG. 3, in the rigidity reinforcing ring 2, a plurality of reinforcing wires 5 extending in the tire radial direction may be arranged at intervals in the tire circumferential direction in a region corresponding to the bead portion T <b> 3. That is, an unvulcanized rubber sheet in which the reinforcing wire 5 is stretched and rubberized may be laminated so that the reinforcing wire 5 extends in the tire radial direction, or the reinforcing wire 5 having a woven structure is attached to the bead portion T3. It may be buried. When the reinforcing wire 5 extended in the radial direction is arranged together with the reinforcing wire 3 wound in the circumferential direction in this way, the rigidity of the bead portion T5 of the rigidity reinforcing ring 2 is increased and the bladderless vulcanization is performed. In addition to making the pressing of the bead portion of the green tire more effective, it is possible to increase the durability of the rigidity reinforcing ring 2 that is required accordingly. The driving density of the reinforcing wire 5 can be appropriately determined according to the durability required for the bead portion. The types and structures of the reinforcing wire 3 wound in the circumferential direction and the reinforcing wire 5 extended in the radial direction may be the same or different.

  Examples of the reinforcing wire 3 and the reinforcing wire 5 constituting the rigidity reinforcing ring 2 include organic fiber cords and steel cords. Examples of organic fiber cords include polyester fiber cords, polyamide fiber cords, rayon fiber cords, aramid fiber cords, polyethylene naphthalate fiber cords, polyolefin ketone fiber cords, and acrylic fiber cords. The twisted structure of these fiber cords can be appropriately determined so that predetermined tensile stress and compressive stress or required durability can be obtained when the rigid reinforcing ring 2 is used. The tensile stress in the circumferential direction of the rigid reinforcing ring 2 can be adjusted by the twisted structure of the reinforcing wire 3 and the tension when spirally wound in the circumferential direction.

  The rigid reinforcing ring 2 is obtained by covering and vulcanizing a reinforcing body composed of the above-described reinforcing wire rods 3 and 5 by sandwiching it with a sheet of unvulcanized rubber 4. As a method of coating with the unvulcanized rubber 4, a rubber strap in which the reinforcing wire 3 is coated with unvulcanized rubber in advance is prepared, and this may be wound spirally in the tire circumferential direction.

  Moreover, the rubber component which comprises the rigidity reinforcement ring 2 is not specifically limited, What is necessary is just a rubber component which usually comprises the rubber composition for tires. Examples of the rubber component include natural rubber, isoprene rubber, butadiene rubber, styrene butadiene rubber, and the like.

  The thickness of the rigidity reinforcing ring 2 is not particularly limited, but is preferably 1 to 10 mm, and more preferably 2 to 5 mm. If the thickness of the rigid reinforcing ring 2 is less than 1 mm, there is a possibility that the effect of adjusting the shape of the tire inner peripheral surface at the time of vulcanization molding cannot be obtained sufficiently. On the other hand, if the thickness of the rigid reinforcing ring 2 exceeds 10 mm, there is a possibility that the effect of reducing the peripheral length after the middle stage of vulcanization molding cannot be obtained sufficiently.

  Hereinafter, a method for vulcanizing a pneumatic tire using the rigid reinforcing ring 2 will be described. In the tire vulcanizing method of the present invention, the above-described rigidity reinforcing ring 2 is disposed on the entire inner surface of the region corresponding to the bead portion T3 from the tread portion T1 of the green tire T set in the mold 1. Bladderless vulcanization is performed by press-fitting a heating medium. By bladderless vulcanization using the rigid reinforcing ring 2, the inner shape of the vulcanized tire can be improved and the dimensional accuracy can be increased. Moreover, since it is only necessary to arrange the rigidity reinforcing ring 2 on the inner peripheral surface of the green tire, it is possible to maintain good productivity of bladderless vulcanization.

  In the vulcanization method of the present invention, a green tire assembly in which the constituent members of the green tire T are integrally assembled on the outer periphery of the rigidity reinforcing ring 2 is manufactured, and the obtained green tire assembly is set in the mold 1 Then, it is better to vulcanize. Thereby, the rigidity reinforcement ring 2 can be reliably arrange | positioned on the internal peripheral surface of the area | region equivalent to the bead part T3 from the tread part T1 of the green tire T. FIG.

  As a mold for setting the obtained green tire assembly, a mold that can be divided into a plurality of parts can be preferably used. By using the mold 1 that can be divided into a plurality of parts, it becomes easy to set a green tire assembly having approximately the same diameter as that of the vulcanized tire in the mold 1. The number of divisions of such a sectional mold can be determined according to the tire shape and tire size.

  Since the pneumatic tire obtained by the tire vulcanizing method of the present invention has a tire shape and dimensional accuracy close to the designed values, the intended tire performance can be achieved more reliably. For example, a pneumatic tire vulcanized and molded using the rigidity-enhanced ring illustrated in FIG. 2A can make the tread portion flat and have a substantially uniform thickness, and can have a good inner surface shape. Thereby, the rolling resistance of the pneumatic tire can be further reduced.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

  When green tires having the same specifications (tire size 205 / 55R16) were produced, bladderless vulcanization was performed using a rigid reinforcing ring in Example 1, and no rigid reinforcing ring was used in Comparative Example 1. In addition, as the rigid reinforcement ring, polyester fiber cord (corresponding to a total fineness of 2200 dtex, twisted structure of 46 × 46 (double twisted)) is spirally wound in the tire circumferential direction with a number of ends of 50/50 mm. A coated and vulcanized cylindrical ring (diameter 570 mm, thickness 2.3 mm) was used.

  The inner surface shape of the pneumatic tire obtained by bladderless vulcanization in Example 1 and Comparative Example 1 was visually observed. The pneumatic tire obtained in Example 1 had a good shape on the inner surface of the tire, and the shape of grooves and sipes in the tread portion were also good. On the other hand, in the pneumatic tire obtained in Comparative Example 1, the shape of the inner surface of the tire was uneven because the shape of the inner surface of the pneumatic tire was pressed with a mold, and the grooves in the tread portion and the shape of the sipe were defective. The shape of the part was uneven and was uneven.

1 Mold 2 Stiffening ring 3 Reinforcement wire 4 Unvulcanized rubber 5 Reinforcement wire T Green tire T1 Tread part T2 Side part T3 Bead part

Claims (7)

  When a green tire is set in a mold, a heating medium is press-fitted inside the green tire, and pressed against the outer side in the tire radial direction to perform bladderless vulcanization, the inside of the area corresponding to the bead portion from the tread portion of the green tire A ring arranged so as to abut on the entire surface, and the stress required to cause a predetermined amount of tensile deformation in the circumferential direction at the tread portion and bead portion of the ring causes a predetermined amount of compressive deformation in the circumferential direction. The rigidity-enhanced ring is characterized by being larger than the stress required for it.   In the tread portion and the bead portion of the ring, a reinforcing body in which a reinforcing wire having a twisted structure is wound at least in the tire circumferential direction is covered with an unvulcanized rubber and is made of a vulcanized ring. The rigidity reinforcing ring according to claim 1.   In the bead portion of the ring, a plurality of reinforcing wires that are the same as or different from the reinforcing wires having the twisted structure are arranged so as to extend in the tire radial direction and at intervals in the tire circumferential direction. The rigidity reinforcing ring according to claim 2.   A bladderless vulcanization method in which a green tire is set in a mold, a heating medium is press-fitted inside the green tire, and pressed outward in the tire radial direction, in a region corresponding to the bead portion from the tread portion of the green tire. A tire vulcanizing method, wherein the heating medium is press-fitted in a state in which the rigidity reinforcing ring according to any one of claims 1 to 3 is disposed over the entire inner surface.   A green tire assembly is produced by integrally assembling the components of the green tire on the outer periphery of the rigid reinforcing ring according to any one of claims 1 to 3, and the green tire assembly is set in the mold. The tire vulcanizing method according to claim 4.   The tire vulcanizing method according to claim 5, wherein the green tire assembly is set inside a mold that can be divided into a plurality of parts.   A pneumatic tire obtained by the tire vulcanizing method according to claim 4.

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