JP2008114491A - Mold for annular member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold for an annular member hard to cause burrs in an outer region in a diametric direction when the annular member like a bead member is injection-molded. <P>SOLUTION: The mold for the annular member is equipped with a lower mold 7 wherein an annular recessed part 9 for molding the bead member is formed and an upper mold 8 constituted relatively movable with respect to the lower mold 7 between a mold clamping position where the annular recessed part 9 is closed to form a cavity 11 and a mold opening position where the annular recessed part 9 is opened and an annular stepped part D is formed on the mold matching surfaces 7a, 8a, 7b and 8b of the lower and upper molds 7 and 8 in the outer region in the diametric direction of the annular recessed part 9. The mold matching surfaces 7a and 8a of the lower and upper molds 7 and 8 are brought into contact with each other in the inner region in the diametric direction of the annular stepped part D and the mold matching surfaces 7b and 8b of the upper and lower molds 7 and 8 are constituted so as to form a slight gap in the outer region in the diametric direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention provides a first mold in which an annular recess for forming an annular member is formed, a mold clamping position in which the annular recess is closed to form a cavity, and a mold opening position in which the annular recess is opened. The present invention relates to an annular member forming die provided with a second die configured to be relatively displaceable with respect to the first die.

  An example of such an annular member is a bead member which is a constituent member of a pneumatic tire. As shown in FIG. 5, the pneumatic tire is configured by combining a plurality of rubber members such as a sidewall rubber 2, a tread rubber 3, and an inner liner rubber 5. The carcass ply 4 has a plurality of parallelly arranged carcass cords covered with rubber, and is arranged so as to be bridged between a pair of annular bead portions 1 so that the end portions in the width direction sandwich the bead member 10. Has been rolled up. As shown in FIG. 6, the bead member 10 has a bead filler 1b made of hard rubber having a substantially triangular cross section extending in the radial direction, and a bead core 1a bonded to the inner periphery of the bead filler 1b. The bead core 1a is composed of, for example, a steel wire converging body.

  In general, an extrusion method is used for forming such a bead member. Specifically, an unvulcanized rubber composition is extruded in a predetermined cross-sectional shape using an extruder, the rubber extrudate is cut at a predetermined length, ends are joined to each other, an annular shape is formed, and a bead core is formed. Adhere to the outer periphery of However, in such a method, there is a problem in that a portion that is locally thick is formed by closely contacting the end portions to be joined, resulting in a decrease in uniformity. In addition, since a process such as cutting and joining of the rubber extruded product is required, there is a problem that man-hours increase.

  On the other hand, for example, as disclosed in Patent Document 1 below, a method of forming a bead member using an injection molding method is known. According to this method, the unvulcanized rubber composition is molded by injection injection into the cavity of the mold that is heated and held, and good uniformity can be secured.

Japanese National Patent Publication No. 11-513324

  According to such an injection molding method, the material injected and injected to the outside in the radial direction of the bead member enters into a state of being integrated with the bead member as a burr by the molding pressure. In particular, the tip of the bead filler of the bead member has a sharp shape and tends to cause burrs. When such burrs are generated, post-processing for removing the burrs is necessary and complicated.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a molding die for an annular member in which burrs are unlikely to occur in the radially outer region when an annular member such as a bead member is injection molded. It is.

In order to solve the above problems, a molding die for an annular member according to the present invention is:
A first mold having an annular recess for forming the annular member;
A mold clamping position for closing the annular recess to form a cavity, and a second mold configured to be relatively displaceable with respect to the first mold between a mold opening position for opening the annular recess. ,
An annular step portion is formed on the die-mating surfaces of the first die and the second die in the radially outer region of the annular recess.

  The operation and effect of the mold for forming the annular member having such a configuration will be described. In the present invention, the annular member is formed by injection molding, and after a predetermined material is injected and injected into a cavity to form the annular member, the mold is opened and demolding is performed. The mold matching surfaces of the first mold and the second mold are not entirely in the same horizontal plane, and an annular step portion is formed in the radially outer region of the annular recess. By forming such an annular stepped portion, even if burrs are generated, it is possible to prevent the range from expanding. Further, by providing the annular stepped portion, it becomes easy to separate the burrs from the product by shearing force when the mold is opened. As a result, when an annular member such as a bead member is injection-molded, it is possible to provide a molding die for the annular member in which burrs are unlikely to occur in the radially outer region.

  In the radially inner region of the annular stepped portion according to the present invention, the first and second mold matching surfaces are brought into contact with each other, and the first and second mold matching surfaces in the radially outer region. Is preferably configured to have a slight gap.

  In the case of providing the annular stepped portion, it is possible to suppress the occurrence of burrs along the die matching surface by bringing the die matching surfaces of the first die and the second die into contact with each other in the radially inner region. Can do. In addition, the first and second mold matching surfaces in the radially outer region are configured so that a slight gap is generated, so that the first and second molds are aligned in the radially inner region. It can be set as the state which contact | abutted the surface reliably.

  The annular member according to the present invention is preferably a bead member constituting a tire. Thereby, the bead member can be injection-molded in a form in which the generation of burrs is suppressed, and the production efficiency can be increased.

  A preferred embodiment of a mold for forming a bead member according to the present invention will be described with reference to the drawings. It is a perspective view which shows the (a) clamping state and (b) mold open state of the shaping | molding die (metal mold | die) which concern on this invention. FIG. 2 is a longitudinal sectional view of the molding die in the clamped state, and corresponds to the AA section of FIG. This mold 6 is used for injection molding the bead member 10 shown in FIG.

  The molding die 6 includes a lower die 7 (corresponding to the first die) having an annular groove 9 formed on the upper surface, and an upper die 8 (above the second die) disposed above the lower die 7. Corresponding). The upper mold 8 has a mold clamping position (see FIGS. 1A and 2) that closes the annular groove 9 to form an annular cavity 11, and a mold opening position that opens the annular groove 9 (FIG. 1B). Between the lower mold 7 and the lower mold 7. As will be described in detail later, an annular step portion D is formed in the radially outer region of the annular recess 9 of the mold 6.

  The upper die 8 includes a sprue 12 extending downward from the center of its upper surface, a runner 13 extending from the sprue 12 to both sides in the width direction, and a cavity extending from the end of the runner 13 with a reduced cross-sectional area. 11 is formed. An unvulcanized rubber composition is supplied to the sprue 12 from an injection mechanism (not shown), and the supplied unvulcanized rubber composition is injected and injected into the cavity 11 through the runner 13 and the gate 14.

  Here, the unvulcanized rubber composition refers to a material prepared by blending a raw material rubber with a compounding material such as a vulcanizing agent by a conventional method and capable of heat crosslinking. There is no restriction | limiting in particular as raw material rubber, General-purpose rubbers, such as natural rubber, styrene-butadiene rubber (SBR), butadiene rubber (BR), and isoprene rubber (IR), can be used.

  In addition, a gas passage A communicating with the cavity 11 is formed in the upper mold 8. In the present embodiment, air is supplied to each of the two gas passages A. However, the present invention is not limited to this, and other gases such as nitrogen, argon, and oxygen may be used (the same applies to the gas passage B described later). .) Although a vent valve is provided at the downstream end of the gas passage A, the gas passage A is closed in a mold-clamping state, so that air pressure is not applied to the bead filler formed in the cavity 11, and the mold opening operation is performed. The closed state is released in conjunction with each other so that air can pass through at the same time as the mold is opened.

  FIG. 3 is an enlarged view showing the periphery of the cavity, FIG. 3A is a view showing a state where a bead member is formed, and FIG. 3B is a view showing only the lower die 7 and the upper die 8. The annular groove 9 has a cross-sectional shape corresponding to the bead member 10, and an annular bead core 1a is disposed on the radially inner portion thereof as shown in an enlarged view in FIG. The radially outer space of the arranged bead core 1a becomes a cavity 11 in a state where the annular groove 9 is closed by the upper mold 8, and an unvulcanized rubber composition for molding the bead filler 1b is supplied. . Similarly to the upper mold 8, the lower mold 7 is provided with a gas passage B.

  The region where the bead cores 1 a of the lower die 7 and the upper die 8 are disposed is a region on the inner diameter side of the annular recess 9. The bead core 1a has a structure in which a bead wire 1c is wound in an annular shape. The bead core 1a has a cross-sectional structure in which a rubber material is filled between bead wires 1c. The bead core 1 a is fixed so as not to move with respect to the lower mold 7 and the upper mold 8 while being sandwiched between the lower mold 7 and the upper mold 8.

  In FIG. 3, the structure of the annular step portion D is shown as an enlarged view. The annular step portion D is formed in the radially outer region of the annular recess 9, and the annular step portion D is also formed in an annular shape. The lower mold 7 is formed with a first mold mating surface 7a and a second mold mating surface 7b, which are connected by a vertical wall surface 7c. The first and second mold matching surfaces 7a and 7b are both horizontal surfaces. The upper mold 8 is also provided with a first mold mating surface 8a and a second mold mating surface 8b, which are connected by a vertical wall surface 8c. The first and second mold matching surfaces 8a and 8b are also horizontal surfaces.

  In FIG. 3, the second mold matching surfaces 7b and 8b are configured to be lower than the first mold matching surfaces 7a and 8a, but the first mold matching surfaces 7a and 8a are configured to be lower. May be. Further, the vertical wall surfaces 7c and 8c may be formed of inclined surfaces instead of 90 ° wall surfaces.

  In the mold closed state, the first mold matching surfaces 7a and 8a of the upper and lower molds 7 and 8 are configured to contact each other, and the second mold matching surfaces 7b and 8b are configured to have a slight gap therebetween. The gap amount may be about 0.5 mm. Thereby, at the time of mold clamping, the 1st type | mold matching surfaces 7a and 8a can be contact | abutted reliably, and the structure which a burr | flash is hard to generate | occur | produce can be provided. In the case of a mold in which the annular step portion D is not formed, the area of the mold matching surface becomes large, and it is difficult to bring the mold matching surface into contact with each other due to the accuracy of flatness. On the other hand, in the case of the present invention, the area of the first mold matching surfaces 7a, 8a is an annular region formed around the annular recess 9, and the area does not have to be so large. The surfaces can be brought into close contact with each other with accuracy. Therefore, it can be set as the type | mold structure which cannot produce a burr | flash easily.

  Although not shown, the mold 6 is provided with a temperature control mechanism. Such a temperature control mechanism has a function of supplying hot water or cold water to a flow path provided in a mold, for example, and is configured to be able to control its temperature, flow rate, supply timing, and the like. Alternatively, a heater or a cooling element may be embedded in the mold 6 and temperature control thereof may be performed based on the detection result of the temperature sensor.

  The material of the mold 6 is not particularly limited, but a mold made of iron or a steel material mainly composed of iron is preferably used. Moreover, the material generally used for injection molding, such as aluminum, an aluminum alloy, and a zinc alloy, may be used.

<Bead member forming process>
Next, a method for forming the bead member will be described. FIG. 4 is a longitudinal sectional view of a forming die showing a forming procedure of the bead member. First, in the mold open state, as shown in FIG. 4A, the bead core 1 a is disposed in the annular groove 9 of the lower mold 7. The bead core 1 a is fixed to a predetermined portion of the lower mold 7. Next, the upper mold 8 is displaced to the mold clamping position and crimped to the lower mold 7 to perform mold clamping. As a result, the annular concave groove 9 is closed by the upper mold 8, and a cavity 11 communicating with the gate 14 is formed at the interface between the lower mold 7 and the upper mold 8. Further, by clamping the mold, the first mold mating surfaces 7a, 8a of the lower mold 7 and the upper mold 8 are brought into close contact with each other.

  After mold clamping, the unvulcanized rubber composition is injected and injected into the cavity 11 as shown in FIG. 4B. The mold 6 at this stage is heated and held at a temperature at which the fluidity of the unvulcanized rubber composition is ensured. This temperature may be lower than the vulcanization temperature, or may be the vulcanization temperature as in conventional injection molding. The injected unvulcanized rubber composition is filled in the cavity 11, and an annular bead filler 1b in which the bead core 1a is integrated on the inner periphery, that is, the bead member 10 is formed.

  In the mold clamping state, air is supplied to the gas passages A and B of the lower mold 7 and the upper mold 8. The supplied air is prevented from passing through the gas passages A and B by the action of a vent valve or the like. The air pressure to be supplied is not limited as long as the bead filler 1b can be appropriately peeled off in a process described later, but a preferable injection pressure is 0.6 MPa or more. The air may be supplied before the unvulcanized rubber composition is injected and injected into the cavity 11.

  As shown in FIG. 4C, mold opening is started while the molded bead filler 1b is in an unvulcanized state. Simultaneously with this mold opening, in the upper mold 8, the closed state of the gas passage A is released, and air is ejected to the upper surface of the bead filler 1b. Further, in the lower mold 7, the closed state of the gas passage B is released simultaneously with the mold opening, and air is ejected to the lower surface of the bead filler 1 b. In the lower mold 7, air is ejected so as to act evenly in the circumferential direction of the bead filler 1b. Thereby, the bead filler 1b can be easily released.

  The mold 6 is opened by displacing the upper mold 8 to the mold opening position. When the mold opening is started, a minute gap is provided between the lower mold 7 and the upper mold 8. Stop mold opening. In this state, air is continuously blown out to the interface between the mold 6 and the bead filler 1 b so that the bead filler 1 b is peeled from the mold 6. The connecting portion between the rubber remaining in the gate 14 and the bead filler 1b is more reliably cut by this process.

  The blown air spreads over the entire circumference of the bead filler 1 b and smoothly peels the bead filler 1 b from the mold 6. Further, by blowing out air at the same time as opening the mold and continuing to blow out air in a state where a minute gap is provided, it is possible to prevent the part peeled off from the bead filler 1b from locally rising from the mold 6. The bead filler 1b can be peeled smoothly without air leaking out. Further, the time for temporarily stopping the mold opening and continuing to supply the air only needs to be such that the bead filler 1b can be smoothly peeled off, but is preferably 1 to 5 seconds from the viewpoint of productivity.

  It is preferable to perform mold opening after injecting and injecting the unvulcanized rubber composition into the cavity 11 and then cooling the bead filler 1b, thereby reliably holding the bead filler 1b in an unvulcanized state. can do. Such cooling of the bead filler 1b can be performed by the temperature control mechanism described above. When demoldability of the bead member 10 is ensured, it is not necessary to perform sufficient cooling to increase the rigidity of the bead filler 1b. Thereafter, the upper mold 8 is displaced to the mold opening position, the mold 6 is fully opened, and the bead member 10 is removed by an appropriate method.

  Since the annular step portion D is provided, burrs are unlikely to occur in the radially outer region of the bead member 10, and it is assumed that the burrs have progressed to the positions of the vertical wall surfaces 7c and 8c of the annular step portion D. However, the burr can be easily separated from the bead member 10 by the shearing action when the mold is opened. Thereby, even if a burr | flash generate | occur | produces, a post process can be eliminated or simplified.

<Another embodiment>
The present invention is not limited to the embodiment described above, and various improvements and modifications can be made without departing from the spirit of the present invention. The lower mold 7 and the upper mold 8 can be configured by combining a plurality of parts, instead of a single part, in order to exhibit a desired function. In this case, it is possible to appropriately determine the shape of the parts to be divided and how to fasten each part. Moreover, also about the formation procedure of a bead member, FIG. 4 shows an example and is not limited to this procedure. In the present invention, the shape of the annular recess is not limited to a specific shape.

  In the present embodiment, the mold configuration in the case of molding the bead member has been described, but the present invention can also be applied to the molding of a tire component other than the bead member.

The perspective view which shows the (a) clamping state and (b) mold open state of the shaping | molding die which concern on this invention Longitudinal sectional view of the mold in the clamped state Longitudinal sectional view showing the cavity periphery Longitudinal section of the mold showing the procedure for forming the bead member Longitudinal section of the mold showing the procedure for forming the bead member Longitudinal section of the mold showing the procedure for forming the bead member Sectional drawing which shows an example of a pneumatic tire Perspective view showing a partially broken bead member

Explanation of symbols

1a Bead core 1b Bead filler 1c Bead wire 6 Mold 7 Lower mold (first mold)
7a First mold mating surface 7b Second mold mating surface 7c Vertical wall surface 8 Upper mold (second mold)
8a First mold mating surface 8b Second mold mating surface 8c Vertical wall surface 9 Annular groove 10 Bead member 11 Cavity D Annular step

Claims (3)

A first mold having an annular recess for forming the annular member;
A mold clamping position for closing the annular recess to form a cavity, and a second mold configured to be relatively displaceable with respect to the first mold between a mold opening position for opening the annular recess. ,
A molding die for an annular member, characterized in that an annular step portion is formed on the die joining surfaces of the first die and the second die in the radially outer region of the annular recess.   In the radially inner region of the annular step portion, the first and second mold matching surfaces are brought into contact with each other, and in the radially outer region, the first and second mold matching surfaces are slightly different. 2. The mold for forming an annular member according to claim 1, wherein the mold is configured so that a gap is formed.   The said annular member is a bead member which comprises a tire, The shaping | molding die of the annular member of Claim 1 or 2 characterized by the above-mentioned.

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