JP2014144552A - Molding method of preset bead - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding method of a preset bead having a little step and protrusion split stiffener bead shape in a circumferential direction.SOLUTION: A molding method of a preset bead B includes: a first process of arranging an annular first rubber body 31 which is un-vulcanized on a rotation center and a concentric circle of a workbench 11A on the workbench 11A which is supported rotatably; a second process of attaching by pressure an annular bead core 6 to the inner side of a radial direction of the first rubber body 31; and a third process of molding a stiffener 7 such that the ribbon-like rubber material R is wound in a circumferential direction of the bead core 6 and a space 7A is formed in between the outer circumferential surface of the radial direction of the bead core so as to be unified with the first rubber body 31.

Description

  The present invention relates to a method for forming a preset bead in which a gap is provided between a bead core and a stiffener.

  Conventionally, there is a so-called WIND bead structure in which a slit is provided between a bead core and a stiffener and both ends of a carcass band are inserted into the slit to prevent stress concentration on the folded portion.

JP 2005-111786 A

  However, in the conventional manufacturing method, when the stiffener constituting the WIND bead structure is integrated with the bead core, a stiffener formed using a bead filler rubber formed in advance by a rubber extruder is used. There is a possibility that a step or unevenness may occur at the joint portion between the circumferential ends. That is, when the molded bead filler rubber is bonded at both ends to form a ring shape, the bonded portion becomes uneven and the thickness changes, so that the tire uniformity may change at that location.

  In addition, due to local unevenness at the location, a gap may be generated between the preset bead and the adjacent member in the tire molding process, leading to product defects.

  In view of the above facts, an object of the present invention is to provide a method for forming a preset bead, that is, a so-called split stiffener bead, in which a gap is provided between a bead core and a stiffener having few steps or irregularities in the circumferential direction.

According to the first aspect of the present invention, there is provided a first step of disposing an unvulcanized annular rubber body concentrically with a rotation center of the work table on a work table rotatably supported, and an annular bead core as the annular rubber. A second step of pressure bonding inside the body in the radial direction, and winding the ribbon-shaped rubber material in the circumferential direction of the bead core so as to be integral with the annular rubber body with a gap between the outer circumferential surface of the bead core in the radial direction And a third step of forming the stiffener.
In the method of forming a preset bead according to claim 1, the stiffener is formed by using an integrally formed bead filler rubber by winding a ribbon-shaped rubber material on the work table with a gap on the outside in the radial direction of the bead core. Compared to the method of forming, the stiffener has no joint, and the step can be reduced.

According to a second aspect of the present invention, there is provided the preset bead molding method according to the first aspect, wherein an annular jig that is in contact with a radial outer peripheral surface of the bead core and a radial inner side surface of the stiffener and can be divided in the circumferential direction is provided. A preparation step of disposing the bead core on the outer peripheral surface in the radial direction, and a winding step of forming the stiffener by winding the ribbon-shaped rubber material in the peripheral direction of the bead core so as to be in contact with the outer peripheral surface of the annular jig in the radial direction. And a removing step of dividing the annular jig after the forming step and removing it from the bead core.
In the preset bead forming method according to the second aspect, the gap between the bead core and the stiffener is formed with an annular jig, so that the surface of the stiffener in the gap portion can be formed smoothly.

According to a third aspect of the present invention, in the method for molding a preset bead according to the first or second aspect, the annular rubber body is molded in advance.
In the preset bead molding method according to the third aspect, the bead core positioning accuracy can be improved and the first step can be shortened by press-bonding the bead core to the annular rubber member molded in advance.

  As described above, according to the preset bead molding method of the present invention, a preset bead molding method having a split stiffener bead structure with few steps and irregularities in the circumferential direction can be obtained.

It is sectional drawing which shows the structural example of the tire created by embodiment of this invention. It is sectional drawing which shows the positional relationship of the bead core on a shaping | molding apparatus, and a stiffener in the shaping | molding method of the preset bead which concerns on embodiment of this invention. FIG. 5 is an enlarged cross-sectional view showing a positional relationship between a bead core, a stiffener, and an annular jig on a molding device in a preset bead molding method according to an embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 2 are diagrams for explaining an embodiment of the present invention.

  A pneumatic tire 1 mainly composed of rubber shown in FIG. 1 is formed by vulcanizing a preset bead B (see FIG. 2) molded by a molding method according to an embodiment of the present invention in a vulcanization process. A bead core 6 and a stiffener 7 are provided.

  The tire 1 includes a pair of bead portions 2 that are fitted to a rim 8 of a wheel, a tread portion 3 that is in contact with a road surface, and extends from the bead portions 2 outward in the radial direction of the tire 1 to be connected to the tread portion 3. And a pair of sidewall portions 4. The toroidal carcass 5 is provided so as to wrap around the bead core 6 from the inner side of the stiffener 7 from the inner side to the outer side through the tread part 3 and the sidewall part 4.

  As shown in FIG. 1A, an annular bead core 6 for fixing the tire 1 to the rim 8 and an annular stiffener 7 made of rubber are in close contact with each other and integrated with a gap 7A on the outer side in the tire width direction. Is provided. The folded portion 5A of the carcass 5 is inserted into the gap 7A so as to wind the bead core 6. The cross-sectional shape of the bead core 6 is a hexagon in this embodiment, but may be a polygon other than a hexagon such as a quadrangle, or a circle including a perfect circle or an ellipse.

Hereinafter, a method for forming the preset bead B will be described.
As shown in FIGS. 2A and 2B, the molding apparatus 10 for molding the preset bead B includes a support member 11 that supports a bead core 6 as an annular bead and an unvulcanized stiffener 7 as an annular rubber body. Then, a servo motor 12 as a drive device that rotates the support member 11 around its rotation axis L1 via a drive system (not shown), and an unvulcanized stiffener 7 are formed on the support member 11 and the bead core 6. For this purpose, a rubber material supply device 20 for supplying an unvulcanized ribbon-shaped rubber material R is provided.

  The support member 11 includes an annular work table 11A that rotates integrally with a turntable 13 that is driven to rotate by a servo motor 12, and a support rim 11B that supports the bead core 6 from the inside in the radial direction and can rotate together with the work table 11A. With. The substantially cylindrical support rim 11B includes a plurality of arc-shaped bead chucks 11C divided in the circumferential direction. The bead chuck 11C is movable in the radial direction of the work table 11A. That is, as shown in FIG. 2B, the bead chuck 11C is driven by the actuator 14 and the link mechanism 14A and is supported so as to be movable in the radial direction.

  The bead core 6 is supported by the support rim 11B so as to rotate integrally with the work table 11A around the rotation axis L1. Actuator 14 is actuated as indicated by arrow 100, and bead chuck 11C is moved radially inward as indicated by arrow 102 by link mechanism 14A (indicated by a two-dot chain line in FIG. 2A). Support from the radially inner side to the bead core 6 is released.

  The rubber material supply device 20 forms an extruder 21 that extrudes unvulcanized rubber having high fluidity, and a rubber that is continuously extruded from the extruder 21 into a ribbon-shaped rubber material R that is a long rubber material. The head part 22 to discharge | emit, the flexible conduit | pipe 23 which guides the rubber | gum from the extruder 21 to the head part 22, and the operation part 24 which changes the position of the head part 22 with respect to the supporting member 11 are provided.

  The head unit 22 is connected to a conduit 23 and continuously discharges unvulcanized rubber, and the rubber discharged from the discharge unit 22A is formed into a ribbon-shaped rubber material R, and the bead core 6 and the work table 11A are formed. It is comprised from the affixing roller 22B as an affixing part affixed on. The affixing roller 22B is composed of a pair of rollers that are rotationally driven by a driving means (not shown) such as a motor provided in the head unit 22, for example, and passes through an opening formed by the pair of rollers. A rubber material R having a cross-sectional shape determined by the opening is molded. The cross-sectional shape of the rubber material R may be any shape such as a polygon, a circle including a perfect circle or an ellipse.

  The operation unit 24 includes an arm 24A that supports the head unit 22 so as to be swingable about a swing center line L3 on a plane orthogonal to the rotation axis L1, and an arm 24A in the axial direction (on the rotation axis L1 of the support member 11). A cylinder 24B that reciprocates in parallel (in a parallel direction), and a support base 24C that supports the cylinder 24B so as to be movable in the radial direction of the rotation axis L1.

  The head portion 22 is driven by an actuator (not shown) provided on the arm 24A and swings to change the orientation of the head portion 22 with respect to the work table 11A, and the cylinder 24B moves the arm 24A to move the work table 11A. The position of the head portion 22 in the axial direction with respect to is changed, and the position of the head portion 22 in the radial direction with respect to the work table 11A is changed by moving the cylinder 24B on the support base 24. Operations of the servo motor 12, the head unit 22, the operation unit 24, and the like are controlled by a control device (not shown).

<First step, preparation step>
Below, each process for shape | molding the preset bead B is demonstrated.
First, as a first step, a first rubber body 31 that is an already molded annular rubber member is attached to a predetermined position on the molding surface K of the work table 11A. Alternatively, the first rubber body 31 may be molded on the work table 11A with the rubber material R instead of the molded annular rubber member.

  When the first rubber body 31 that is an already molded annular rubber member is attached on the molding surface K of the work table 11A, the gap between the bead core 6 and the molding surface K is filled with the first rubber body 31. The positional accuracy of the bead core 6 on the molding surface K is improved.

  When molding the first rubber body 31 with the rubber material R, in the first step, at a predetermined position on the molding surface K of the work table 11A that is driven and rotated by the servo motor 12 (see FIG. 2B), The rubber material R supplied from the affixing roller 22B (see FIG. 2A) of the head portion 22 is sequentially laminated in the direction of the rotation axis L1 while being wound a plurality of times in a spiral shape for each layer. An annular first rubber body 31 is attached to the molding surface K and molded.

At this time, since the bead core 6 (see FIG. 2A) is not supported by the support rim 11B, the movement of the head portion 22 in the radial direction and the axial direction is not restricted by the presence of the bead core 6.
The axial direction is the direction of the rotation axis L1. In the embodiment, the rotation axis L1 coincides with the center axis L2 of the preset bead B and the center axis (not shown) of the tire 1. Moreover, a cross section is a cross section in the plane containing the rotating shaft L1.

  Subsequently, after the first step, a preparation step in which the annular jig 16 is fitted from the outer peripheral side of the bead core 6 is performed. The annular jig 16 has a substantially donut shape that is a set of jig pieces 16A divided in the circumferential direction, and the outer side in the radial direction is an outer peripheral surface 16C in contact with a second rubber body 32 described later. Further, the inner side in the radial direction is an inner peripheral surface 16B having a shape fitted to the outer peripheral surface of the bead core 6, and is in close contact with the bead core 6 supported by the support rim 11B.

  When the jig piece 16A is fitted to the outer peripheral surface of the bead core 6, a gap may be formed between the jig pieces 16A forming the annular jig 16. That is, in the second molding process described later, if the gap (gap 7A) can be provided between the bead core 6 and the second rubber body 32, the annular jig 16 does not need to be annular during the second molding process. .

<Second step>
Further, the bead core 6 supported in a fixed state on the expanded support rim 11B is pressed against the first rubber body 31 attached to the work table 11A. At this time, a part of the annular jig 16 is in close contact with the first rubber body 31 and is also in close contact with a part of the outer peripheral surface of the bead core 6, and a predetermined gap (between the bead core 6 and the first rubber body 31 ( It becomes a spacer for providing the interval 7A).

By this second step (pressing step), the first rubber body 31 adheres to a part of the outer peripheral surface of the bead core 6, and an integration step of integrating the bead core 6 with the first rubber body 31 is performed. As a result, the bead core 6 is positioned with respect to the first rubber body 31.
As shown in FIG. 3 (A), the attachment portion of the stiffener 7 in the bead core 6 is a part of the first rubber body 31, and finally the gap between the stiffener 7 and the bead core 6 is as shown in FIG. 3 (C). The gap 7A shown is formed. At this time, the outer peripheral surface 16C of the annular jig 16 forms a surface on which the rubber material R discharged from the head part 22 is actually wound.

<Third step, removal step>
After the second step, as shown in FIGS. 3A to 3C, the rubber material R discharged from the head portion 22 is placed on the bead core 6 and the first rubber body 31 held by the support member 11. Then, a second molding step is performed in which the annular second rubber body 32 is molded by being laminated in the direction of the rotation axis L1 while being wound in a spiral shape many times per layer. At the same time, a third step (winding step) in which the second rubber body 32 adheres to the first rubber body 31 in the molding process of the second rubber body 32 is performed.

Further, the second rubber body 32 adheres to the entire surface of the remaining portion other than the portion to which the first rubber body 31 is adhered on the outer peripheral surface 16 </ b> C of the annular jig 16, and adheres to the first rubber body 31.
Thus, the rubber material R is wound around the first rubber body 31 on the outer peripheral side of the annular jig 16 according to the shape of the outer peripheral surface 16 </ b> C, thereby forming the second rubber body 32. At this time, due to the presence of the annular jig 16, the rubber material R is naturally wound around the outer peripheral surface 6B of the bead core 6 at a predetermined interval.

  For this reason, when the rubber material R is laminated in the direction of the rotation axis L1 and the annular second rubber body 32 is formed in the winding end stage of the rubber material R shown in FIG. An SSB (split stiffener bead) shape in which a gap 7A is formed between the first rubber body 31 and the second rubber body 32 is formed. A so-called wind bead structure can be formed by inserting the tip of the carcass 5 into the gap 7 when processing the green tire described later.

  When the second rubber body 32 is formed, the head portion 22 may be tilted with respect to the rotation axis L1 and wound so that the ribbon-like rubber material R is laminated obliquely on the work table 11A. That is, since the surface of the first rubber body 31 having a substantially triangular cross section is inclined with respect to the work table 11A, the second rubber body 32 may be formed by winding the ribbon-shaped rubber body R obliquely along this. .

  After the second rubber body 32 is formed, a removal step of removing the annular jig 16 from the bead core 6 is performed. At this time, the outer peripheral side of the annular jig 16 is in close contact with the second rubber body 32, and the lower end of the annular jig 16 is more than the outermost peripheral end of the bead core 6 as shown in FIGS. Even if it enters the radial inner side, it can be removed without any problem by dividing the jig piece 16A.

  If necessary, it is softer than the first rubber body 31 and the second rubber body 32 with respect to the bead core 6, the first rubber body 31 and the second rubber body 32 integrated on the support member 11 in the third step. A ribbon-shaped rubber material R2 (not shown) made of the above rubber is wound in a spiral shape for each layer, and is laminated in the axial direction to form an annular third rubber body 33 (not shown). The 4th process shape | molded without forming a space | gap between the 1st rubber body 31 and the 2nd rubber body 32 may be performed.

  In the fourth step, since the rubber material R having a property different from that of the rubber material R used for molding the first rubber body 31 and the second rubber body 32 is used, the first and second molding steps are used. It is necessary that the extruder 21 and the head unit 22 used in the above are replaced.

  Further, if necessary, between the third step and the fourth step, or after the fourth step, after the fourth step, the pressure-bonding step in which the first to third rubber bodies 31, 32, 33 are more closely adhered to each other by the pressure roller. A shaping step of shaping the second rubber body 32 and the third rubber body 33 with a shaping roller (for example, flattening the surfaces of the second rubber body 32 and the third rubber body 33) may be performed.

  Through these series of steps, the unvulcanized stiffener 7 including the first to third rubber bodies 31, 32, 33 and the bead core 6 are integrated and a gap 7A is formed therebetween. A bead B is formed.

  Thereafter, the preset bead B is set at both ends of the unvulcanized carcass 5 located on both sides of the forming drum, and the folded portion 5A of the carcass 5 is inserted into the gap 7A to form a wind bead structure. Processed into tires. Thereafter, the green tire is vulcanized in a vulcanization process.

<Effect>
Next, operations and effects of the embodiment configured as described above will be described.
That is, when integrating the stiffener 7 constituting the SSB structure with the bead core 6, compared to a conventional manufacturing method using a stiffener formed using a bead filler rubber previously formed by an extruder 21, It has the following excellent features.
In the preset bead molding method according to the present embodiment, the second rubber body 32 is formed by winding the ribbon-shaped rubber material R around the outer periphery of the first rubber body 31 and the annular jig 16 on the support member 11. There is no risk of unevenness or unevenness at the joint part between the end parts of the bead filler rubber, and the joint part becomes uneven when joining the molded bead filler rubber at both ends and making it into a ring shape, Since the thickness changes, there is no possibility that the uniformity of the tire will change at that location. Further, since the unevenness of the joint portion is eliminated, there is no possibility that a gap is generated between the preset bead and the adjacent member in the tire molding process, and there is no possibility of product failure due to product air entering due to the joint portion.

  In the experiments by the inventors, when the stiffener 7 having a hypotenuse length of about 45 mm / base length of about 15 mm is formed using a ribbon-shaped rubber material R having a width of 10 mm / gauge (thickness) of 1.5 mm, In the joint portion, the incidence of air entering due to the joint was reduced from 2% to 0% compared to the conventional method (using extruded bead filler rubber). Similarly, the uniformity of the tire 1 decreased by an average of 5N in RFV (circumferential stiffness distribution).

  If the gap 7A is formed using the annular jig 16 as in the present embodiment, the ribbon-like rubber material R is laminated to form the stiffener 7. It is easy to make the surface of the gap 7A smooth, and there is no possibility that the folded portion 5A may be inserted when the folded portion 5A of the carcass 5 is inserted into the gap 7A to form a wind bead structure.

Second Embodiment
In the first embodiment, the annular jig 16 is provided on the outer periphery of the bead core 6, and the second rubber body 32 is formed by winding the ribbon-shaped rubber material R around the outer peripheral surface 16C. However, the present invention is not limited to this. Alternatively, the second rubber body 32 may be formed without using the annular jig 16.
That is, after the bead core 6 is pressed and integrated with the first rubber body 31, the ribbon-shaped rubber material R may be wound around the support member 11 at a predetermined position on the molding surface K of the work table 11A to form the second rubber body 32. . In this case, the process of forming the first rubber body 31 with the ribbon-shaped rubber material R is repeated as it is to form the second rubber body 32.
In this method, since the second rubber body 32 is formed by laminating the ribbon-shaped rubber material R as it is, it is difficult to smooth the surface of the gap 7A. Can be reduced.

  The embodiments of the present invention have been described with reference to the examples. However, the above embodiments are merely examples, and various modifications can be made without departing from the scope of the invention. Needless to say, the scope of rights of the present invention is not limited to the above embodiment.

6 bead core, 7 stiffener, 7A gap, 11 support member, 11A, work table, 11C bead chuck, 16 annular jig, 16A jig piece, 16B inner peripheral surface, 31 first rubber body (annular rubber body), 32 2 rubber body, B preset bead, K molded surface, R ribbon rubber material

Claims (3)

A first step of disposing an unvulcanized annular rubber body concentrically with a rotation center of the work table on a work table rotatably supported;
A second step of crimping the annular bead core to the radially inner side of the annular rubber body;
A third step of winding a ribbon-shaped rubber material in the circumferential direction of the bead core, and forming a stiffener so as to be integrated with the annular rubber body with a gap between the bead core and a radially outer peripheral surface;
A method for forming a preset bead including: A preparatory step of disposing an annular jig that is in contact with the radially outer peripheral surface of the bead core and the radially inner side surface of the stiffener and can be divided in the circumferential direction on the radially outer peripheral surface of the bead core;
A winding step of forming the stiffener by winding the ribbon-shaped rubber material in the circumferential direction of the bead core so as to be in contact with the radially outer peripheral surface of the annular jig;
The method for forming a preset bead according to claim 1, further comprising: a step of separating the annular jig after the forming step and removing it from the bead core.   The preset bead molding method according to claim 1 or 2, wherein the annular rubber body is molded in advance.

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