JP2009137035A - Method of manufacturing bead core assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately form a bead core assembly without causing eccentricity of a bead core even while forming a bead apex rubber by injection molding. <P>SOLUTION: The bead apex rubber is partitioned into inner and outer apex parts 3A, 3B by an oblique side. The manufacturing method includes molding steps K1, K2 for forming the apex parts 3A, 3B with injection molding molds 20, 21, and a joining step K3 for integrally joining the apex parts 3A, 3B by pushing them. Respective injection molding molds 20, 21 is composed of inner and outer mold separation parts 23-26 in a tire axial direction of a bead core 2, and one side mold separation parts 23, 25 are dismounted after being injection molded. Respective apex parts 3A, 3B are held by other mold separation parts 24, 26, the other mold separation parts 24, 26 are moved to close each other, and the apex parts 3A, 3B and the bead core 2 are integrally joined by pressing to each other between the mold separation parts 24, 26 and a bead core support instrument 22. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a bead core assembly that can form a bead core assembly in which a bead apex rubber is bonded to a bead core with high quality and can improve tire uniformity.

  In general, in a pneumatic tire, as shown in FIG. 5, in order to reinforce the bead part a and improve steering stability and bead durability, the bead part a is radially outward from the radial outer surface of the bead core b. A bead apex rubber c having a triangular cross-section extending is provided. When manufacturing such a tire, an annular bead core assembly d in which the bead core b and the bead apex rubber c are integrally joined is formed in a separate process, and this bead core assembly d is used as a raw tire production line. It is thrown into.

  On the other hand, the bead core assembly d is conventionally formed by extruding a band-shaped rubber member having a triangular cross section using a rubber extruder, and winding the band-shaped rubber member once on the outer surface of the bead core. This is done by butting both ends together.

  However, such a forming method may cause unevenness in rigidity and strength, such as deviation between end portions in the joint portion, and may cause a decrease in tire uniformity.

  Therefore, in recent years, it has been proposed to form the bead apex rubber c in an annular shape by injection molding. In this forming method, as shown in FIG. 6A, the bead core b and the bead apex rubber are set by setting the bead core b in the molding chamber e1 of the injection mold e and injecting a rubber material into the remaining space. A bead core assembly d integrally formed with c can be formed.

  However, the bead core b is formed of a core body b1 in which a bead wire having a circular cross section is wound a plurality of times, and a wrapping layer b2 made of, for example, rubber-equipped campus cloth or the like. Therefore, there is some variation in the cross-sectional shape of the bead core b. Therefore, when the bead core b is set in the injection mold e, a gap is inevitably generated between the mold surface and the bead core b. As a result, at the time of injection molding, the rubber material enters the gap and causes a problem that the bead core b is eccentric. When the bead apex rubber c is formed by two rubber portions Ya and Yb having different rubber hardnesses as shown in FIG. 5, it is difficult to adopt the injection molding method.

  It may be proposed that only the bead apex rubber c is separately formed by injection molding, and then the injection-molded bead apex rubber c is joined to the bead core b. However, as shown in FIG. 6B, the bead apex rubber c protrudes radially inward beyond the outermost point b1 on both sides in the tire axial direction of the radially outermost point b1 of the bead core b. When the portions c1 and c2 are provided, the one protruding portion c1 (or c2) becomes an obstacle, and the bead apex rubber c cannot be joined to the bead core b. For this reason, it is necessary to cut off one of the protruding portions c1, which causes a defective air remaining during vulcanization molding.

  Therefore, the present invention has been made in view of such a situation, and while forming a bead apex rubber by injection molding, a bead core assembly can be accurately formed without incurring the eccentricity of the bead core. It is an object of the present invention to provide a method for manufacturing a bead core assembly, which can be applied to the case where the two rubber portions are included and the case where the bead apex rubber has the protruding portion.

JP 2006-248037 A

In order to achieve the above object, the invention of claim 1 of the present application is directed to a bead core, a bottom side that is in contact with a radially outer surface of the bead core, an inner bottom point of the inner end in the tire axial direction of the bottom side, an outer side of the outer end in the tire axial direction. A bead core assembly manufacturing method for forming a bead core assembly in which a bead apex rubber having a triangular cross-section surrounded by an inner inclined side and an outer inclined side that cross each other from the bottom point in the radial direction is joined,
The bead apex rubber has a divided oblique side extending from a dividing point on the bottom side to an intermediate point on one of the inner or outer inclined sides, and a first inner side in the tire axial direction from the divided inclined side. It is divided into an apex portion and a second apex portion on the outer side in the tire axial direction,
A first molding step of forming the first apex portion using a first injection mold;
A second molding step of forming the second apex portion using a second injection mold;
The first apex formed in the first molding step and the second formed in the second molding step from both sides in the tire axial direction of the bead core whose radial inner surface is supported using the bead core support. A joining step of pressing and joining the bead core and the first and second apex portions together by pressing the two apex portions together,
Moreover, the first injection mold includes a first outer split mold part on the outer side in the tire axial direction having a molding concave part for molding the first apex part, and the molding concave part is closed and the inner inclined side is formed. A first inner mold part on the inner side in the tire axial direction having an inner inclined side molding surface to be formed;
The second injection mold includes a second inner mold part on the inner side in the tire axial direction having a molding recess for molding the second apex part, the molding recess and the outer inclined side. A second outer split mold portion on the outer side in the tire axial direction having an outer inclined side molding surface to be formed;
The joining step includes
After the first molding step, the first outer split mold part is removed, and a holding step of holding the molded first apex part on the inner inclined side molding surface of the first inner split mold part;
After the second molding step, the second inner mold part is removed, and a holding step of holding the molded second apex part on the outer inclined side molding surface of the second outer mold part,
The first inner mold part and the second outer mold part are brought close to each other, and the first inner mold part, the second outer mold part, and the bead core support are disposed between the first inner mold part and the second outer mold part. And a joining step of joining the apex part, the second apex part, and the bead core together by pressing them together.

  According to a second aspect of the present invention, the inner diameter of the first apex portion and the inner diameter of the second apex portion are smaller than the outer diameter of the bead core, respectively.

  In the invention of claim 3, the base has an outermost point located on the radially outermost side between the inner base point and the outer base point, and the outermost point is the division point. It is characterized by that.

  Further, the invention of claim 4 is characterized in that the first apex portion and the second apex portion have different rubber physical properties after vulcanization.

  In the present invention, the bead apex rubber is divided into two apex portions as described above, and each apex portion is formed by injection molding using an injection mold. Therefore, a bead apex rubber uniform in the circumferential direction without a joint portion can be formed.

  In addition, each injection mold is constituted by a split mold part inside and outside in the tire axial direction, and after injection molding, one split mold part is removed and each apex part is held by the other split mold part. The split mold parts are brought close to each other, and the two apex parts and the bead core are pressed against each other and integrally joined between the other split mold part and the bead core support that supports the bead core. That is, since the other split mold part is also used as a jig for joining the apex part as it is, the apex part and the bead core can be accurately aligned at the time of joining. Therefore, for example, a bead core assembly can be formed with high accuracy without incurring eccentricity of the bead core.

  In addition, since each apex portion is separately injection-molded, the case where the bead apex rubber is formed by two rubber portions having different rubber physical properties can be dealt with. In addition, since each apex portion is joined close to both sides in the tire axial direction, it can be joined even when the bead apex rubber has protruding portions on both sides in the tire axial direction at the radially outermost point of the bead core. A solid can be formed.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an unvulcanized bead core assembly 1 formed by the manufacturing method of the present invention.

  As shown in FIG. 1, a bead core assembly 1 according to this embodiment is formed of a bead core 2 and a bead apex rubber 3 having a triangular cross section joined to a radially outer surface SU of the bead core 2.

  The bead core 2 includes at least an annular core body 4 in which a bead wire 2s having a circular cross section is wound a plurality of times. In this example, the bead core 2 and the periphery of the bead wire 2s are prevented by being wound around the core body 4. For example, the one formed from a wrapping layer 5 made of a campus cloth with rubber or the like is illustrated. As the core body 4, in this example, a cross-sectional polygonal body, particularly a flat horizontally long hexagonal body is illustrated, but the present invention is not limited to this. For example, a regular hexagonal body, a quadrangular body, Or the thing of a circular body is also employable suitably. As the wrapping layer 5, a conventional material such as a rubber sheet and a cord ply in which a wrapping cord is embedded in rubber can be used as appropriate, in addition to a campus cloth with rubber.

  Further, in this specification, the radially outer surface SU of the bead core 2 means a surface exposed to the outside in the radial direction, and specifically, as shown in FIG. 2, the innermost point Pi of the bead core 2 in the tire axial direction. The outer surface SU is defined as a radially outer surface between a radial line Xi passing through and a radial line Xo passing through the outermost point Po in the tire axial direction. A radially inner surface between the radial lines Xi and Xo is defined as a radially inner surface SL of the bead core 2.

  The bead apex rubber 3 includes a base 10 in contact with the radial outer surface SU of the bead core 2, an inner bottom point 10a at the inner end in the tire axial direction of the base 10 and an outer base point 10b at the outer end in the tire axial direction. Each of them forms a triangular cross section surrounded by an inner inclined side 11 and an outer inclined side 12 that intersect at the apex Q radially outward.

  Further, the bead apex rubber 3 is divided by the divided oblique side 13 extending from the dividing point 10m on the base 10 to the intermediate point M on one of the inner or outer inclined sides 11 and 12, or the intermediate point M on the inclined side 11 or 12. It is divided into a first apex portion 3A on the inner side in the tire axial direction from the oblique side 13 and a second apex portion 3B on the outer side in the tire axial direction. The first apex portion 3A is composed of a hard rubber member G1 having a rubber hardness Hs1 in the range of 70 to 95 after vulcanization molding, and the second apex portion 3B is formed after vulcanization molding. The rubber hardness Hs2 is smaller than the rubber hardness Hs1, for example, a soft rubber member G2 having a range of 50 to 65. In this example, the divided oblique side 13 is illustrated as extending from the dividing point 10 m to the intermediate point M on the inner inclined side 11, thereby contacting the outer inclined side 12 of the bead apex rubber 3. The carcass folding portion t (shown in FIG. 5) can be prevented from peeling from the bead apex rubber 3.

  The inner diameter Da of the first apex portion 3A and the inner diameter Db of the second apex portion 3B are smaller than the outer diameter D0 of the bead core 2, respectively. Therefore, the first and second apex portions 3A and 3B include protruding portions 3Aa and 3Ba extending inward in the radial direction beyond the radially outermost point J of the bead core 2, respectively. The inner diameters Da and Db mean the diameter at the radially innermost point of the bottom 10 of the first and second apex portions 3A and 3B, and the outer diameter D0 of the bead core 2 is the outermost radial direction. It means the diameter at point J.

  Further, the base 10 of the bead apex rubber 3 has an outermost point j located on the outermost side in the radial direction between the inner base point 10a and the outer base point 10b, and the outermost point j is divided. The divided oblique side 13 is formed as a point 10m. The outermost point J of the bead core 2 coincides with the outermost point j of the bottom side 10 of the bead apex rubber 3.

Next, a method for manufacturing the bead core assembly 1 will be described. The production method of the present invention comprises:
A first molding step K1 (shown in FIG. 3) for forming the first apex portion 3A using the first injection mold 20;
A second molding step K2 (shown in FIG. 3) for forming the second apex portion 3B using the second injection mold 21;
The first apex portion 3A formed in the first molding step K1 and the second molding step from both sides in the tire axial direction of the bead core 2 on which the radial inner surface SL is supported using the bead core support 22 A joining step K3 (shown in FIG. 4) in which the second apex portion 3B formed by K2 is pressed against and the bead core 2 and the first and second apex portions 3A, 3B are pressed and joined together. And including.

  Here, as shown in FIG. 3, the first injection mold 20 includes a first outer mold part 23 on the outer side in the tire axial direction and a first inner mold part 24 on the inner side in the tire axial direction. The first outer mold part 23 and the inner mold part 24 are held so as to be relatively movable in the tire axial direction.

  Among these, the first outer split mold portion 23 is provided with a molding recess 23a for molding the first apex portion 3A. Further, the first inner mold part 24 is provided with an inner inclined side molding surface 24a for closing the molding recess 23a and forming the inner inclined side 11. In the closed state of the mold, the first injection mold 20 is surrounded by the molding recess 23a and the inner inclined side molding surface 24a, thereby forming a molding chamber H1 having the same shape as the first apex portion 3A. In addition, the first apex portion 3A can be injection-molded by injecting the rubber member G1 into the molding chamber H1 (first molding step K1).

  Further, in the first injection mold 20, the first outer split mold part 23 and the inner split mold part 24 are separated inward and outward in the tire axial direction by the relative movement, and the first outer split mold part 23 is inward. By removing from the split mold part 24, the mold is opened, and the molded first apex part 3A is taken out. At this time, it is important that the first apex portion 3A is adhered and held on the inner inclined side molding surface 24a of the first inner split mold portion 24. Therefore, it is necessary to provide a difference between the mold release property of the inner surface of the molding recess 23a and the mold release property of the inner inclined side molding surface 24a. By performing a mold release process such as applying an agent, the first apex portion 3A can be adhered to the inner inclined side molding surface 24a and held by the first inner mold portion 24.

  In this example, the case where the first outer split mold portion 23 is relatively removed from the inner split mold portion 24 by moving the first inner split mold portion 24 inward in the tire axial direction is illustrated. However, it is also possible to move the first outer split mold part 23 or both in the tire axial direction.

  Next, as shown in the figure, the second injection mold 21 includes a second inner split mold portion 25 on the inner side in the tire axial direction and a second outer split mold portion 26 on the outer side in the tire axial direction. The second inner mold part 25 and the outer mold part 26 are formed so as to be relatively movable in the tire axial direction.

  Among these, the second inner mold part 25 is provided with a molding recess 25a for molding the second apex part 3B. Further, the second outer split mold portion 26 is provided with an outer inclined side molding surface 26a that closes the molding concave portion 25a and forms the outer inclined side 12. The second injection mold 21 has a molding chamber H2 having the same shape as the second apex portion 3B by being surrounded by the molding recess 25a and the outer inclined side molding surface 26a in the mold closed state. In addition, the second apex portion 3B can be injection-molded by injecting the rubber member G2 into the molding chamber H2 (second molding step K2).

  In the second injection mold 21, as in the case of the first injection mold 20, the second inner mold part 25 and the outer mold part 26 are separated from each other in the tire axial direction by the relative movement. When the second inner mold part 25 is removed from the outer mold part 26, the mold is opened, and the molded second apex part 3B is taken out. At this time, it is important that the second apex portion 3B is adhered and held on the outer inclined side molding surface 26a of the second outer split mold portion 26. Therefore, as in the case of the first injection mold 20, in this example, for example, by applying a mold release treatment such as applying a mold release agent to the inner surface of the molding recess 25 a, a difference in mold release properties is achieved. Provided.

  In this example, the case where the first outer split mold part 23 and the second inner split mold part 25 are integrally formed is illustrated, but they can also be formed independently.

Next, in the joining step K3, as described above,
After the first molding step K1, the first outer mold part 23 is removed from the inner mold part 24, and the molded first apex part 3A is used as the inner inclined side of the first inner mold part 24. Holding step K3a held by the molding surface 24a;
After the second molding step K2, the second inner mold part 25 is removed from the outer mold part 26, and the molded second apex part 3B is removed from the outer inclined side of the second outer mold part 26. And holding step K3b held by the molding surface 26a.

  Further, in the joining step K3, as shown in FIG. 4, the first inner split mold part 24 holding the first apex part 3A and the second outer split mold part 26 holding the second apex part 3B. Between the first inner split mold part 24, the second outer split mold part 26 and the bead core support 22, the first apex part 3A, the second apex part 3B and the bead core 2 And a joining step K3c for joining them together.

  Here, the bead core support 22 has a ring shape that can be expanded and contracted, and includes a receiving surface 22S that receives the radially inner surface SL of the bead core 2 at the radially outer end thereof, so that the bead core 2 can be freely attached and detached. Can support. In this example, the first inner split mold portion 24 and the second outer split mold portion 26 are positioned on both sides of the bead core support 22 in the tire axial direction while holding the apex portions 3A and 3B, respectively. In other words, the case of moving in the tire axial direction toward the bead core support 22 is illustrated. However, for example, the first outer split mold part 23, the second inner split mold part 25, and the bead core support 22 can be configured to be replaceable.

  Thus, in the present invention, the bead apex rubber 3 is divided into two apex portions 3A and 3B, and each apex portion 3A and 3B is formed by injection molding. Therefore, the bead apex rubber 3 uniform in the circumferential direction without the joint portion can be formed.

  Each injection mold 20 and 21 is constituted by split mold parts 23 to 26 in the tire axial direction. After injection molding, one split mold part 23 and 25 is removed and the other split mold parts 24 and 26 are separated. The apex portions 3A and 3B are held by the other, and the other split mold portions 24 and 26 are brought close to each other, and two apex portions are provided between the other split mold portions 24 and 26 and the bead core support 22. 3A, 3B and the bead core 2 are pressed together and joined together. That is, since the other split mold parts 24 and 26 are used as they are as jigs for joining the apex parts 3A and 3B as they are, alignment at the time of joining can be performed accurately. Therefore, for example, the bead core assembly 1 can be accurately formed without incurring the eccentricity of the bead core 2.

  Further, the case where the bead apex rubber 3 is formed of two rubber portions having different rubber properties can be dealt with. Further, since the apex portions 3A and 3B are joined close to both sides in the tire axial direction, the bead apex rubber 3 can be joined even when the protruding portions 3Aa and 3Ba are provided, and the bead core assembly 1 is formed. Yes.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  A radial tire for a passenger car having a tire size of 195 / 65R15 was manufactured using the bead core assembly formed by the manufacturing method of the present invention, and the uniformity of the prototype tire was measured and compared with each other.

In Table 1, in Comparative Example 1, a bead core assembly is formed by winding a strip-shaped rubber member having a triangular cross-section extruded by a rubber extruder along the outer surface of the bead core. In Comparative Example 2, a bead core assembly is formed by setting a bead core in an injection mold and injecting a rubber material into the remaining space.
In Comparative Example 3, only the bead apex rubber is separately formed by injection molding, and then the bead apex rubber is fitted into the bead core to form a bead core assembly.

  <Uniformity>

  RFV is measured in accordance with JASO C607 automobile tire uniformity test method, RFV of sample tires (100 tires each) is measured, average value of the primary component (RFV primary), and standard deviation (σ ).

  It can be confirmed that the uniformity of the tire of Example 1 is greatly improved as compared with Comparative Example 1 using the extruded rubber band member. In Comparative Example 2, although it is injection molding, the effect of improving uniformity is insufficient, such as the rubber material entering the gap between the mold surface and the bead core to cause eccentricity of the bead core. In Comparative Example 3, when the bead apex rubber has a protruding portion, the protruding portion becomes a hindrance and it is difficult to attach the bead core. Accordingly, it is necessary to cut off one of the protruding portions, and therefore, there is a tendency that air remains in the bead portion.

It is sectional drawing which shows the bead core assembly formed by the manufacturing method of this invention. It is sectional drawing explaining the radial direction outer surface of a bead core. It is sectional drawing which shows the 1st, 2nd shaping | molding process with an injection mold. It is sectional drawing which shows a joining process. It is sectional drawing which shows the bead part of a pneumatic tire. (A), (B) is explanatory drawing which shows the problem in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead core assembly 2 Bead core 3 Bead apex rubber | gum 3A 1st apex part 3B 2nd apex part 10 Base 10a Inner base point 10b Outer base point 10m Inclined side 12 in dividing point 11 Outer inclined side 13 Divided inclined side 20 First 1 injection mold 21 second injection mold 22 bead core support 23 first outer mold part 23a molding recess 24 first inner mold part 24a inner inclined side molding surface 25 second inner mold Part 25a Molding concave part 26 Second outer split mold part 26a Outer inclined side molding surface J Outermost point K1 First molding process K2 Second molding process K3 Joining process K3a, K3b Holding step K3c Joining step M Intermediate point Q Vertex SL Radial inner surface SU Radial outer surface

Claims (4)

The bead core has a bottom that is in contact with the outer surface in the radial direction of the bead core, an inner bottom point at the inner end of the tire axial direction on the bottom side, and an outer bottom point at the outer end in the tire axial direction. A bead core assembly manufacturing method for forming a bead core assembly in which a bead apex rubber having a triangular cross section surrounded by an inclined side and an outer inclined side is joined,
The bead apex rubber has a divided oblique side extending from a dividing point on the bottom side to an intermediate point on one of the inner or outer inclined sides, and a first inner side in the tire axial direction from the divided inclined side. It is divided into an apex portion and a second apex portion on the outer side in the tire axial direction,
A first molding step of forming the first apex portion using a first injection mold;
A second molding step of forming the second apex portion using a second injection mold;
The first apex formed in the first molding step and the second formed in the second molding step from both sides in the tire axial direction of the bead core whose radial inner surface is supported using the bead core support. A joining step of pressing and joining the bead core and the first and second apex parts together by pressing the two apex parts together,
Moreover, the first injection mold includes a first outer split mold part on the outer side in the tire axial direction having a molding concave part for molding the first apex part, and the molding concave part is closed and the inner inclined side is formed. A first inner mold part on the inner side in the tire axial direction having an inner inclined side molding surface to be formed;
The second injection mold includes a second inner mold part on the inner side in the tire axial direction having a molding recess for molding the second apex part, the molding recess and the outer inclined side. A second outer split mold portion on the outer side in the tire axial direction having an outer inclined side molding surface to be formed;
The joining step includes
After the first molding step, the first outer split mold part is removed, and a holding step of holding the molded first apex part on the inner inclined side molding surface of the first inner split mold part;
After the second molding step, the second inner mold part is removed, and a holding step of holding the molded second apex part on the outer inclined side molding surface of the second outer mold part,
The first inner mold part and the second outer mold part are brought close to each other, and the first inner mold part, the second outer mold part, and the bead core support member A method of manufacturing a bead core assembly, comprising: a joining step of joining the apex portion, the second apex portion, and the bead core together by pressing them together.   The bead core assembly manufacturing method according to claim 1, wherein an inner diameter of the first apex portion and an inner diameter of the second apex portion are smaller than an outer diameter of the bead core.   2. The base has an outermost point located on an outermost radial direction between the inner base point and the outer base point, and the outermost point is set as the division point. Or the manufacturing method of the bead core assembly of 2.   The bead core assembly manufacturing method according to any one of claims 1 to 3, wherein the first apex portion and the second apex portion are different in rubber physical properties after vulcanization.

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