JP2012081659A - Vulcanizing mold and method of manufacturing pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vulcanizing mold and a method of manufacturing a pneumatic tire by which gas sealed in a cavity is constantly discharged smoothly from a vent hole by preventing a spew from remaining on the vent hole formed on a molded surface, and deterioration of quality of a manufactured tire can be prevented by suppressing variation of shapes or the like of vent spews protruded from an outer surface of a product tire after released from a mold.SOLUTION: The vulcanizing mold 1 contributes to partition a cavity 6 to vulcanize and mold a raw tire. The vent holes 7, 17 for discharging the gas sealed in the cavity 6 are formed on the molded surfaces 2a, 3a, 4a facing to the cavity 6. Spiral grooves 7a, 17a are formed on inner circumferential surfaces of the vent holes 7, 17.

Description

  The present invention relates to a vulcanization mold that contributes to vulcanization molding of a raw tire and a method for manufacturing a pneumatic tire, and in particular, vulcanization molding of a raw tire in a cavity that is partitioned by the vulcanization mold. At this time, by improving the vent hole that controls the discharge of the sealed gas to the outside of the cavity, the spue formed on the outer surface of the tire after vulcanization is prevented from adhering to the vent hole and remaining, and the product tire It proposes a technology that enhances quality.

A so-called full mold type or split mold type vulcanizing mold for vulcanizing a raw tire is an expansion of the raw tire placed in a cavity defined inside, for example, due to bulging deformation of the vulcanizing bladder. Based on the radial deformation, the raw tire is pressed against the molding surface, and the raw tire is vulcanized from the inner surface side to produce a vulcanized product tire.
In such a vulcanization mold, the raw tire is sufficiently pressed against the molding surface having a profile corresponding to the outer surface shape of the manufactured tire, and the mold profile is surely imparted to the vulcanized tire. The mold forming surface is provided with a vent hole that allows the cavity to communicate with the outside of the mold. By this vent hole, the gas sealed in the cavity is caused to expand along with the expansion of the raw tire when the raw tire is vulcanized. It is supposed to be discharged outside the mold.

  By the way, in the vulcanization mold, for example, as described in Patent Document 1, as a conventional technique, when the green tire is pressed against the molding surface, the gas sealed in the cavity is discharged from the vent hole and the green tire is discharged. The unvulcanized rubber part on the surface will be sucked into the vent hole, and this causes multiple vent spews to protrude from the tire surface in the vent hole after the vulcanization process. A part of the vent spew may be cut in the vent hole when the vulcanized product tire is released from the mold and may remain in the vent hole.

In this way, when the next raw tire is vulcanized with the vulcanization mold while the spew remains in the vent hole, the exhaust gas discharge performance due to the vent hole is greatly reduced. After being released from the mold due to the presence of spews in multiple vent holes on the molding surface, in addition to the risk of forming so-called bears on the crown of the manufactured tire, etc. Variations in the shape and length of the spew protruding from the outer surface of the tires, and even if the vent spew is cut off with a trimming cutter, etc., it may affect the quality of the product tire, such as poor appearance and reduced performance. It was.
Therefore, when replacing the mold itself, every time the mold is removed from the upper and lower platens, etc., or periodically, the spew remaining in the vent hole is removed. There was another problem of significant degradation.

  On the other hand, Patent Document 2 states that “a mold for tire vulcanization molding in which a chamfering process is performed on an inlet of a vent hole, and the chamfered part and the vent hole parallel part are connected to each other with a convex curved surface inside. According to this “mold for tire vulcanization molding”, “the connection portion between the chamfered portion of the vent hole and the parallel portion is formed into a convex curved surface on the inside. The stress concentration on the spew is no longer incurred, thereby eliminating the spew cut. ”

JP 63-78709 A Japanese Utility Model Publication No. 63-92707

  However, in the “tire vulcanization molding die” described in Patent Document 2, when the raw tire is vulcanized, the unvulcanized rubber portion on the outer surface of the raw tire is perpendicular to the molding surface. In this case, an elongated spew is formed in the vent hole because it is sucked into the vent hole provided on the molding surface, and when the product tire is released after the vulcanization process is finished, the tire The above-mentioned elongated spew on the outer surface is affected by the force in the axial direction of the vent hole, so that spout is cut and the cut spew still remains in the vent hole. Such a problem may occur.

  An object of the present invention is to solve such problems of the prior art, and the object of the present invention is to prevent spew from remaining in a vent hole provided on a molding surface. The exhaust of the gas enclosed in the cavity by the vent hole is always made smooth and the variation of the shape of the vent spew protruding from the outer surface of the product tire after mold release is suppressed, so that the quality of the manufactured tire can be improved. It is in providing the vulcanization mold which can prevent a fall, and the manufacturing method of a pneumatic tire.

  The vulcanization mold according to the present invention contributes to a cavity section for vulcanization molding of a raw tire, and a vent hole is provided on the molding surface facing the cavity to control the discharge of sealed gas to the cavity. In addition, a spiral groove is formed on the inner peripheral surface of the vent hole.

  Further, in the method for producing a pneumatic tire according to the present invention, a green tire molded on a molding drum is placed in a mold for vulcanization in a mold opening posture, the mold is clamped, and then the interior is defined inside. In the production of a pneumatic tire by vulcanizing and molding the green tire in an annular cavity formed, the mold is provided on the tire molding surface facing the cavity, and the inner peripheral surface has a spiral shape. The gas enclosed in the cavity is discharged from the vent hole formed with the groove toward the axial direction of the vent hole under the generation of a rotating air flow around the vent hole axis by the spiral groove. The green tire is pressed against the tire molding surface and vulcanized.

According to the vulcanization mold of the present invention, the spiral groove is formed on the inner peripheral surface of the vent hole on the molding surface, so that when the raw tire is vulcanized in the vulcanization mold, The unvulcanized rubber part of the surface of the green tire to be pressed is sucked into the vent hole with a rotational force around the axis of the vent hole along the spiral groove, so-called Based on the gyro effect, the fluidity in the axial direction of the vent hole of the unvulcanized rubber part sucked into the vent hole is increased, so that, for example, on the tire outer surface in the cavity after the vulcanization process, As a result of the formation of a bent spew with a stable shape that does not have a constricted portion with a small diameter, the spew breaks in the vent hole when the product tire is released from the mold. It is possible to effectively prevent the residual spew to Le.
For this reason, during the subsequent vulcanization molding of raw tires, there is no variation in the shape and length of the vent spew on the outer surface of the tire due to the remaining spew in the vent hole, and the quality of the product tire It is possible to surely remove the risk of deterioration.

  Also, in this vulcanization mold, as the raw tire expands and deforms during vulcanization molding, the gas enclosed in the cavity is subjected to a vent hole under the generation of a rotating air flow along the spiral groove on the inner peripheral surface of the vent hole. As a result, the energy loss caused by this discharge is reduced, and the exhausted gas by the vent hole is increased. As a result, the so-called bear to the manufactured tire is reduced. Occurrence can be further prevented.

  Further, according to the pneumatic tire manufacturing method of the present invention, when the green tire is vulcanized, the gas enclosed in the cavity is rotated from the vent hole formed with the spiral groove to the rotating airflow around the axis of the vent hole. As described above, a vent spew with a stable shape is formed on the outer surface of the tire in the cavity and the gas enclosed in the cavity is discharged. The smooth discharge from the vent hole can effectively prevent the occurrence of so-called bears on the manufactured tire, so that a high quality tire can be manufactured.

It is a principal part longitudinal cross-sectional view which shows one Embodiment of the vulcanization mold of this invention with a container which accommodates it with a mold-clamping attitude | position. It is sectional drawing which expands and shows the vent hole of the vulcanization mold shown in FIG. 1, and its modification. It is sectional drawing which shows the mold opening process of the mold shown in FIG.

Embodiments of the present invention will be described below with reference to the drawings.
A split mold type vulcanization mold 1 illustrated in FIG. 1 is arranged in an annular lower side mold 2 and at a predetermined interval from the lower side mold 2, and is also arranged in an annular shape. A plurality of sectors divided in the circumferential direction that are in cylindrical contact with each other in the mold clamping posture of the illustrated mold on the outer peripheral side (left side in the figure) of the upper side mold 3 and the upper and lower side molds 2, 3. The piece 4 includes a plurality of circumferentially divided back segments 5 which are disposed so as to surround the sector pieces 4 and form a hollow frustum shape in a clamping posture.
As a matter of course, the configuration of the present invention can also be adopted in a full mold type vulcanization mold.

  Here, in the clamping position of the mold 1 as shown in FIG. 1, the lower side mold 2, the upper side mold 3, and the plurality of sector pieces 4, in combination with the vulcanization bladder shown in phantom lines in the figure, An annular cavity 6 in which the raw tire is disposed is defined inside, and surfaces facing this cavity 6, that is, surfaces 2 a and 3 a facing each other of the lower side mold 2 and the upper side mold 3, and a cylinder A profile corresponding to the outer surface shape of the manufactured tire is applied to the inner peripheral surface 4a (the right side surface in the figure) of the plurality of sector pieces 4 having a shape, and these surfaces are desired on the outer surface of the raw tire. It is made to function as a molding surface which gives the profile.

  Then, as shown in the figure, the vent surface 7a of the sector piece 4 is provided with two vent holes 7 extending linearly, for example, for communicating the cavity 6 to the outside of the mold 1 through an exhaust passage (not shown), As shown in FIG. 2 (a) in an enlarged manner on the inner peripheral surface of each vent hole 7, the vent hole 7 extends from the opening on one end side (not shown) of the vent hole 7 to the opening on the other end side. A plurality of spiral grooves 7a extending around the axis line of is formed.

In FIG. 2A, a plurality of spiral grooves 7a are formed on the inner peripheral surface of the vent hole 7. However, as shown in FIG. 2B, for example, only one spiral groove is formed. It is also possible to form 17a by increasing the number of turns around the axis line from the opening at one end of the vent hole 17 to the opening at the other end.
Here, of course, the groove depth, groove width, etc. of the spiral groove can be appropriately selected as required.
The vent holes 7 can be provided in the lower side mold 2 and the upper side mold 3, and the number of the vent holes 7 can be appropriately increased or decreased according to the size and shape of the tire to be manufactured.

By the way, as shown in FIG. 1, the mold 1 is housed in a container 8 that contributes to mold clamping and mold opening of the mold 1 for use.
Here, the illustrated container 8 is attached to the lower platen 9 that supports the mold 1 by contacting the lower surfaces of the lower side mold 2 and the back segment 5 and the upper surface of the upper side mold 3, and can be displaced in the vertical direction. In the figure, the upper platen 10 formed by stacking and fixing two plate-shaped members and a plurality of back segments 5 having a hollow truncated cone shape in a reduced diameter posture are disposed so as to surround the upper platen 10. The container ring 11 is connected to the lower surface.
Here, the inner peripheral surface of the container ring 11 is a tapered surface 11a that is aligned with the tapered outer peripheral surfaces of the plurality of back segments 5 having a hollow truncated cone shape, and the tapered surface 11a is engaged with the back segment 5 (not shown). Provide a part.

  According to such a container 8, when the raw tire is placed in the cavity 6 or when the tire after vulcanization molding is taken out from the mold cavity, as shown in FIG. The plurality of back segments 5 and the plurality of back segments 5 that are in contact with each other in the circumferential direction as the upper side mold 3 attached to the upper platen 10 and the container ring 11 are raised by pulling up the platen 10 as indicated by arrows in the drawing. Each sector piece 4 is lifted after being separated in the circumferential direction based on the action of the engaging portion formed on the tapered surface of the container ring 11 and expanded in the direction indicated by the white arrow in the figure. Thus, the mold 1 can be opened.

  Further, in order to clamp the mold 1 thus opened in order to vulcanize the green tire, the upper side mold 3 and the container ring 11 are lowered by lowering the upper platen 10 pulled up as described above. As the taper descends, the plurality of back segments 5 and sector pieces 4 in a posture separated in the circumferential direction are reduced in diameter based on the sliding contact of the tapered surfaces of the container ring 11 with the tapered side surfaces of the plurality of back segments 5. They are displaced and brought into contact with each other in the circumferential direction.

  When the raw tire is vulcanized with the mold 1 shown in FIG. 1, the mold 1 is opened by operating the container 8 on the molding drum (not shown) and operating the container 8 as described above. After being placed inside, the mold 1 is clamped.

  Next, on the inner peripheral side of the molding cavity 6, steam or the like is supplied to the inside of the vulcanization bladder indicated by the phantom line in the figure to bulge and deform the vulcanization bladder, thereby expanding the raw tire in the cavity 6. The outer surface of the raw tire is pressed against the molding surfaces 2a, 3a and 4a by being deformed in diameter, and the unvulcanized rubber member constituting the raw tire is crosslinked by supplying heat from the molding surface and the vulcanization bladder. Allow the reaction to proceed.

  At this time, the air existing between the raw tire to be expanded and deformed and the molding surfaces 2a, 3a, 4a, the gas generated by the progress of vulcanization of the raw tire, etc. In the figure, it is discharged from the vent hole 7 opened on the molding surface 4a of the sector piece 4, but in the present invention, based on the generation of a rotating air flow along the spiral groove 7a formed on the inner peripheral surface of the vent hole 7, Since the filled gas or the like is smoothly discharged in the axial direction of the vent hole 7, the discharge property of the filled gas by the vent hole 7 can be improved.

  Further, when the unvulcanized rubber portion on the outer surface of the raw tire is sucked into the vent hole 7 provided on the molding surface 4a in accordance with the pressing to the molding surface, here the molding surface 4a of the sector piece 4 Further, the rubber part flows in the vent hole 7 while being given a rotational force around the axis of the vent hole 7 by the spiral groove 7a in the vent hole 7, so that the unvulcanized rubber is based on the so-called gyro effect. The flowability of the portion in the axial direction of the vent hole 7 is increased, so that a spew having a stable shape protruding from the outer surface of the tire is formed in the vent hole 7.

Finally, the tire after the crosslinking reaction of the rubber member is released from the mold 1 opened as described above.
Here, since the vent spew having a stable shape is formed on the outer surface of the tire, the spew is difficult to be cut in the vent hole 7 when the product tire is released. Spew residue can be effectively prevented.
As a result, the shape of the bent spew protruding from the outer surface of the tire that has been vulcanized and molded in the mold 1 will be stabilized, so that the quality of the product tire caused by variations in the shape of the bent spew, etc. The risk of decline is eliminated.

  Next, since the vulcanization mold of this invention was manufactured and the performance was evaluated, it demonstrates below.

The mold of the embodiment is a split mold type having the structure shown in FIG. 1, and reaches a vent hole having a diameter of 2.0 mm and a length of 22.0 mm provided on the molding surface from one opening to the other opening. Until then, one spiral groove rotating 7.3 times around the axis of the vent hole was formed.
The groove width of the spiral groove was 3.0 mm, and the groove depth was 0.5 mm.
The mold of the conventional example has the same structure as the mold of the example except that the spiral groove is not formed on the inner peripheral surface of the vent hole.

Each of these molds is used to vulcanize green tires, and the amount of sealed gas discharged from the vent hole during the vulcanization molding and the outer surface of the tire formed in the vent hole after vulcanization molding. Each of the spew volumes to be studied was examined.
As a result, in the mold of the example, a result that both the discharge amount of the enclosed gas and the volume of the vent spew were increased by about 7% as compared with the mold of the conventional example.
Moreover, when the vulcanization molding of the green tire was performed 20 times with each mold, the result of the example mold was that the shape of the bent spew formed on the outer surface of the tire was more stable than the mold of the conventional example. Obtained.

  From the above, according to the vulcanization mold of the present invention, it is possible to prevent variations in the shape and length of the bent spew formed on the outer surface of the tire and the so-called bear generation on the product tire. As a result, it was found that the risk of product quality deterioration could be eliminated.

DESCRIPTION OF SYMBOLS 1 Vulcanization mold 2 Lower side mold 3 Upper side mold 4 Sector piece 5 Back segment 2a, 3a, 4a Molding surface 6 Molding cavity 7, 17 Vent hole 7a, 17a Spiral groove 8 Container 9 Lower platen 10 Upper platen 11 Container ring 11a Tapered surface

Claims (2)

A vulcanization mold that contributes to a cavity section for vulcanization molding of a raw tire,
A vulcanization mold in which a vent hole for controlling discharge of an enclosed gas to the cavity is provided on a molding surface facing the cavity, and a spiral groove is formed on an inner peripheral surface of the vent hole. The green tire molded on the molding drum is placed in a mold for vulcanization in an open mold position, the mold is clamped, and then the green tire is placed in an annular cavity defined inside. In vulcanizing and manufacturing pneumatic tires,
Provided on the molding surface of the tire facing the cavity of the mold, the gas enclosed in the cavity from the vent hole formed with a spiral groove on the inner peripheral surface of the vent hole is formed by the spiral groove. A method for producing a pneumatic tire in which a green tire is pressed against the tire molding surface and vulcanized while being discharged toward the axial direction of the vent hole under generation of a rotating airflow around the axis.

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