JP2008114492A - Mold for annular member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold for an annular member capable of precisely performing the centering of a core part with respect to a mold body part which constitutes the mold for injection-molding the annular member. <P>SOLUTION: The mold for the annular member is equipped with a lower mold 7 formed with an annular recessed part 9 for molding a bead member 10 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. The upper mold 8 is composed of an annular gate 14 for injecting a material in the cavity 11, a mold body part 80 arranged at a position outer than that in the diametric direction in order to form the annular gate 14 and a core part 81 arranged at a position inner than that in the diametric direction in order to form the annular gate 14. A large number of projections 81a protruded from the outer peripheral part of the core part 81 to come into contact with inner peripheral part 80a of the mold body part 80 are arranged as a positioning mechanism for performing the centering of the center of the core part 81 with respect to the mold body part 80. <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. And a second die configured to be relatively displaceable with respect to the first die, and an annular member forming 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, the 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

  When an annular member such as a bead member is injection-molded, it is preferable that the gate portion for injecting and injecting the material is also formed in an annular shape. Accordingly, the material can be uniformly injected, the molded bead member can be made into a homogeneous material, and the uniformity of the manufactured tire can be improved. When the annular gate portion is provided, it is necessary to divide the die into a die main body portion located on the radially outer side of the annular gate portion and a core portion located on the radially inner side. That is, an annular gate portion is formed between the inner peripheral portion of the mold main body portion and the outer peripheral portion of the core portion.

  This annular gate part needs to have the same gate width dimension over the entire circumference in the circumferential direction, but when attached to the mold body part with the center position of the core part deviating from a predetermined position, The gate width dimension of the annular gate portion is not the same and bias occurs. As a result, since the material is not injected into the cavity in a uniform state, the material may also be biased.

  This invention is made | formed in view of the said situation, The subject is the annular member which can perform the centering of the core part with respect to the type | mold main-body part which comprises the type | mold for injection-molding an annular member accurately. It is to provide a mold.

In order to solve the above-mentioned problem,
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 mold for the annular member,
The second mold is
An annular gate for injecting material into the cavity;
In order to form an annular gate portion, a mold body portion located on the outer side in the radial direction,
In order to form an annular gate portion, a core portion located on the radially inner side,
A positioning mechanism for centering the core part with respect to the mold body part,
As this positioning mechanism, a plurality of projecting portions that protrude from the outer peripheral portion of the core portion and abut against the inner peripheral portion of the die main body portion are arranged along the circumferential direction.

  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. An annular gate for injecting material into the cavity for forming the annular member is provided. By the annular gate portion, the material can be injected and injected uniformly into the annular recess. In order to form the annular gate portion, the mold main body portion is disposed on the radially outer side of the annular gate portion, and the core portion is disposed on the radially inner side of the annular gate portion. An annular gate portion is formed between the outer peripheral portion of the core portion and the inner peripheral portion of the mold main body portion. Furthermore, a plurality of projecting portions are formed along the circumferential direction from the outer peripheral portion of the core portion, and by configuring the projecting portions to contact the inner peripheral portion of the mold main body portion, the core The part can be accurately centered with respect to the mold body part. As a result, it is possible to provide a molding die for the annular member that can accurately center the core portion with respect to the die main body constituting the die for injection molding the annular member.

In order to solve the above problems, another annular member molding die 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. A mold for the annular member,
The second mold is
An annular gate for injecting material into the cavity;
In order to form an annular gate portion, a mold body portion located on the outer side in the radial direction,
In order to form an annular gate portion, a core portion located on the radially inner side,
A positioning mechanism for centering the core part with respect to the mold body part,
As this positioning mechanism, a plurality of projecting portions that protrude from the inner peripheral portion of the die main body portion and abut against the outer peripheral portion of the core portion are arranged along the circumferential direction. In the above description, a configuration example in which a plurality of projecting portions are formed in the core portion has been described. However, a plurality of projecting portions may be arranged on the inner peripheral portion of the mold main body portion. The core portion can be accurately centered with respect to the mold main body portion by bringing the protruding portion into contact with the outer peripheral portion of the core portion. As a result, it is possible to provide a molding die for the annular member that can accurately center the core portion with respect to the die main body constituting the die for injection molding the annular member.

  An example of the annular member according to the present invention is a tire bead member. Thereby, a bead member can be formed with a uniform material and the uniformity of a tire can also be made favorable.

  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.

  The upper die 8 includes a sprue 12 extending downward from the center of the 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 (corresponding to an annular gate portion) communicating with the gate 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.

  The gate 14 is formed in an annular shape, and the upper mold 8 can be divided into a mold main body portion 80 located on the radially outer side of the gate 14 and a core portion 81 located on the radially inner side of the gate 14. Since the gate 14 is annular, the outer peripheral surface of the core portion 81 is configured based on a cylindrical surface. The inner peripheral surface of the mold main body 80 is also configured based on a cylindrical inner surface.

  As shown in FIG. 3, a large number of protrusions 81 a (corresponding to protrusions) are formed on the outer peripheral portion of the core portion 81 along the circumferential direction. The protrusion 81 a may be formed integrally with the core portion 81, or another member may be coupled to the core portion 81. The protrusion 81 a is formed so as to contact the inner peripheral surface 80 a of the mold main body 80. Although the gate 14 is configured in the form of a slit formed on the outer peripheral surface of the core portion 81, the width dimension thereof needs to be the same over the entire periphery. This is because the material can be injected and injected uniformly into the cavity. For this purpose, it is necessary to accurately position the core portion 81 with respect to the mold main body portion 80. That is, it is necessary to center the core portion 81 with high accuracy. Therefore, the protrusion 81a is provided as described above and brought into contact with the inner peripheral surface of the mold main body 80, whereby the centering can be accurately performed.

  The number of the protrusions 81a can be set as appropriate. The same applies to the arrangement interval when arranged along the circumferential direction and the shape of the protrusion 81a. The material cannot be injected and injected from the location where the protrusion 81a is present, but it is formed in an annular shape when viewed from the gate 14 as a whole. The position of the gate 14 can be set as appropriate according to the shape and size of the bead member 10.

  The core portion 81 can be coupled to the die body portion 80 by a mechanical fastening means such as a bolt. Although the gate 14 exists over the entire circumference in the circumferential direction, the runner 13 does not exist over the entire circumference, so that both can be fastened using that portion.

  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.

  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 mold matching surfaces 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 unvulcanized rubber composition injected and injected 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. 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.

<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. For example, as a specific configuration of the positioning mechanism, in the present embodiment, the protrusion is formed on the core portion 81, but a number of protrusions (projections) along the circumferential direction of the inner peripheral surface of the mold main body portion 80. May be formed. In this case, the arrangement interval, shape, size, and the like of the protrusions can be the same as in the case of forming the core portion 81.

  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. This also applies to the core part 81 and the mold body part 80. 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 6 Mold 7 Lower mold (first mold)
8 Upper mold (second mold)
9 annular groove 10 bead member 11 cavity 13 runner 14 gate 80 mold body 80a inner peripheral surface 81 core 81a protrusion

Claims (3)

A first mold having an annular recess for forming the annular member;
And a second mold configured to be relatively displaceable with respect to the first mold between a mold clamping position for closing the annular recess to form a cavity and a mold opening position for opening the annular recess. A mold for the annular member,
The second mold is
An annular gate for injecting material into the cavity;
In order to form an annular gate portion, a mold body portion located on the outer side in the radial direction,
In order to form an annular gate portion, a core portion located on the radially inner side,
A positioning mechanism for centering the core part with respect to the mold body part,
As the positioning mechanism, an annular member forming die characterized in that a plurality of protruding portions that protrude from the outer peripheral portion of the core portion and contact the inner peripheral portion of the die main body portion are arranged along the circumferential direction. 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 mold for the annular member,
The second mold is
An annular gate for injecting material into the cavity;
In order to form an annular gate portion, a mold body portion located on the outer side in the radial direction,
In order to form an annular gate portion, a core portion located on the radially inner side,
A positioning mechanism for centering the core part with respect to the mold body part,
As this positioning mechanism, an annular member forming die characterized in that a plurality of protruding portions protruding from the inner peripheral portion of the die main body portion and contacting the outer peripheral portion of the core portion are arranged along the circumferential direction.   The said annular member is a bead member of a tire, The shaping | molding die of the annular member of Claim 1 or 2 characterized by the above-mentioned.

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