JP3774517B2 - Pneumatic tire mold - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mold for forming a pneumatic tire having a bead ring, and more particularly, to prevent a failure in a bead portion regardless of a change in specifications around the bead and an error in the amount of rubber involved. The present invention relates to a molding die for a pneumatic tire that enables the above.
[0002]
[Prior art]
Conventional molds for pneumatic tires, in the case of a sectional type, are sectors for forming the tread and shoulder, upper and lower molds for forming the sidewall and bead of the tire, and bead sheets attached to the upper and lower molds, respectively. It is comprised from the bead ring which shape | molds a part. In the case of the upper and lower halves, the upper and lower molds each form a tread portion, a sidewall portion, and a bead portion in half, and bead rings that respectively form bead sheet portions attached to the upper and lower molds. In either case, an unvulcanized green tire is inserted into the inside of the molding die configured as described above, and vulcanization molding is performed while applying pressure from the inside of the tire by a bladder. The contact surface of the bead ring with the bladder usually extends parallel to the tire radial direction, and the bead portion is formed so as to be sandwiched between the bladder and the bead ring.
[0003]
However, since it is difficult to keep the amount of rim cushion rubber involved around the bead constant at the time of molding the tire, failures such as pinch beads, narrow beads, or soft beads after vulcanization of the tire are caused by bead failure. May occur in some parts. That is, when the amount of rubber involved around the bead is small, as shown in FIG. 8 (a), the rubber flows due to the pressure of the bladder, and the bead portion B is thinner than the designed shape (broken line) of the tire T. Will be molded. On the other hand, when the amount of rubber involved around the bead is large, the rubber flows out between the bladder and the contact surface 12 between the bladder of the bead ring 11 as shown in FIG.
[0004]
In addition, when molding tires that have the same tire size and tread pattern but differ only in the specifications around the bead (bead capacity) due to the different number of laminated carcass layers and reinforcing layers, the same bead ring should be used. When used, the bead failure becomes more prominent. Therefore, it is necessary to use a bead ring having a ring width corresponding to the volume around the bead. For this reason, there has been a problem that tire productivity is significantly hindered by troublesome bead ring replacement work.
[0005]
[Problems to be solved by the invention]
The object of the present invention is to reduce the occurrence of failure in the bead part regardless of the change in the specifications around the bead and the error of the rubber entrainment amount, and to improve productivity by molding with the same bead ring It is to provide a molding die.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a molding die for a pneumatic tire according to the present invention is provided with a bead ring for molding a tire bead portion, and an air in which a bladder capable of expanding and contracting is provided inside the bead ring toward the inside of the tire. In a mold for entering tires, a region where the contact surface with the bead ring bladder is inclined toward the outside of the tire from a position corresponding to the bead toe of the bead portion, and the contact surface with the bead ring bladder is inclined. The length L of the tire in the radial direction of the tire is such that L ≧ 1.5 G with respect to the thickness G of the bladder, and the cross-sectional shape of the contact surface with the bladder of the bead ring is straight, The inclination angle α with respect to the radial direction is 5 ° to 35 °.
[0007]
In this way, by inclining the contact surface of the bead ring with the bladder from the position corresponding to the bead toe of the bead portion toward the outside of the tire, the bladder is inflated inside the bead portion according to the inclination angle of the contact surface during vulcanization. Led to. By providing this inclination angle, it is possible to prevent the bead portion from being compressed by the bladder when the amount of rubber involved around the bead is small, and conversely, when the amount of rubber involved is large, the rubber Since it can prevent flowing out between a bladder and a bead ring, generation | occurrence | production of the failure in a bead part can be reduced.
[0008]
Also, the tire mold and the tread pattern are the same, but the molding die of the present invention is the same even when molding tires with different capacities around the beads due to different numbers of laminated carcass layers and reinforcing layers. Since it is possible to adapt to changes in the capacity around the bead while using the bead ring, it is not necessary to use a different bead ring with a ring width corresponding to the volume around the bead. Therefore, when continuously manufacturing tires having the above conditions, the bead ring replacement work can be omitted, and the productivity of the tires can be remarkably improved.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
In the figure, M is a molding die, T is an unvulcanized pneumatic tire, and B is a bead portion of the tire T. The bead ring 1 constitutes a part of the molding die M so as to contact the sheet of the bead portion B. The bead ring 1 has a contact surface 2 that comes into contact with the bladder 3 during vulcanization, and the contact surface 2 is inclined toward the tire outer side from a position corresponding to the bead toe of the bead portion B with respect to the tire radial direction R. Yes.
[0010]
That is, the bead ring 1 has an overhanging shape so that the contact portion with the bead portion B protrudes toward the inside of the tire. The overhang-shaped protruding end portion is formed in an arc shape so as not to damage the bladder 3. Further, the contact surface 2 of the bead ring 1 with the bladder 3 is a flat surface as shown in FIGS. 1 and 2, but the contact surface 2a is convexly curved as shown in FIG. As shown in 3 (b), the contact surface 2b curved in a concave shape is not used .
[0011]
As described above, when the contact surface 2 of the bead ring 1 with the bladder 3 is inclined to the outside of the tire from the position corresponding to the bead toe of the bead portion B, the bladder 3 is connected to the contact surface 2 during vulcanization. Depending on the inclination angle with respect to the tire radial direction R, the bead portion B is guided inside the tire so as to wrap. For this reason, even when the amount of rubber around the bead of the unvulcanized green tire is small, as shown in FIG. 4A, the bead portion B can be prevented from being pressed and thinly formed by the bladder 3. . On the other hand, when the amount of rubber involved around the bead is large, the rubber does not easily flow out between the bladder 3 and the contact surface 2 of the bead ring 1 as shown in FIG. Therefore, even if an error occurs in the amount of rubber around the bead when the tire is molded, a failure in the bead portion B can be prevented.
[0012]
Also, when molding tires T that have the same tire size and tread pattern but differ only in the specifications (capacity) around the bead, it is possible to respond to changes in the capacity around the bead as described above. Therefore, it is not necessary to use different bead rings 1 having ring widths corresponding to. Therefore, when such tires are continuously manufactured, the same mold can be used without replacing the bead ring 1, thereby eliminating the bead ring replacement time and significantly improving the productivity of the tire. Can do.
[0013]
In the present invention, as shown in FIG. 5, the inclination angle α of the contact surface 2 with the bladder 3 of the bead ring 1 with respect to the tire radial direction R is preferably 5 ° to 35 °. Further, the length L in the tire radial direction of the sloped region on the contact surface 2 of the bead ring 1 with the bladder 3 is such that L ≧ 1.5G, preferably L ≧ 2G, with respect to the thickness G of the bladder 3. It is preferable to do. The thickness of the bladder 3 is preferably 5 to 13 mm.
[0014]
FIG. 6 shows the measurement results of the failure rate around the bead and the life of the bladder when a pneumatic tire was molded under the same conditions except that the inclination angle α of the bead ring 1 was changed. In the figure, the failure occurrence rate (•) around the bead is indicated by an index with the failure occurrence rate when α = 0 ° being 100, and the failure occurrence rate is higher as the index value is larger. Further, the lifetime of the bladder (▲) is indicated by an index with the lifetime when α = 0 ° being 100, and the greater the index value, the longer the lifetime of the bladder.
[0015]
As apparent from FIG. 6, when the inclination angle α is in the range of 5 ° to 40 °, the failure occurrence rate around the bead is remarkably reduced, and when the inclination angle α is 35 ° or less, The life of the bladder is good because the overhang shape does not damage the bladder. Therefore, the inclination angle α is preferably in the range of 5 ° to 35 °.
[0016]
FIG. 7 shows that a failure occurs around a bead when a pneumatic tire is molded under the same conditions except that the inclination angle α is 20 ° and the length L of the region where the contact surface 2 of the bead ring 1 is inclined is changed. The result of measuring the rate is shown. In the figure, the failure occurrence rate (•) around the bead is indicated by an index with the failure occurrence rate when L = 0 being 100, and the failure occurrence rate is higher as the index value is larger. The length L is a ratio to the thickness G of the bladder.
[0017]
As apparent from FIG. 7, the failure occurrence rate around the bead is remarkably reduced when the length L is 1.5 G or more, more preferably 2.0 G or more.
[0018]
【The invention's effect】
As described above, according to the present invention, in a molding die for a pneumatic tire provided with a bead ring for forming a tire bead portion, the contact surface with the bladder of the bead ring is positioned from the position corresponding to the bead toe of the bead portion. Since it is inclined outward, it is possible to reduce the occurrence of failure in the bead portion regardless of changes in specifications around the bead and errors in the amount of rubber involved. In addition, when forming tires that differ only in the specifications around the bead, there is no need to use different bead rings, so the productivity of the tire can be significantly improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a molding die for a pneumatic tire according to an embodiment of the present invention.
FIG. 2 is an enlarged view of a portion A in FIG.
FIGS. 3A and 3B are sectional views showing a molding die for a pneumatic tire according to a comparative example of the present invention.
4A and 4B are cross-sectional views showing a tire bead portion formed using a pneumatic tire molding die according to an embodiment of the present invention.
FIG. 5 is a sectional view showing a molding die for a pneumatic tire according to an embodiment of the present invention.
FIG. 6 is a graph showing the relationship between the inclination angle α, the failure occurrence rate around the bead, and the life of the bladder.
FIG. 7 is a graph showing a relationship between a length L of a region to be inclined and a failure occurrence rate around a bead.
8A and 8B are cross-sectional views showing a tire bead portion formed using a conventional molding die.
[Explanation of symbols]
1 Bead ring 2 Contact surface with bladder 3 Bladder T Pneumatic tire B Bead part M Mold

Claims (2)

In a molding die for a pneumatic tire provided with a bead ring for forming a tire bead portion and provided with a bladder that can expand and contract toward the inside of the tire inside the bead ring, the contact surface of the bead ring with the bladder is Inclined toward the outside of the tire from the position corresponding to the bead toe of the bead portion, and the length L in the tire radial direction of the region where the bead ring is inclined at the contact surface with the bladder is L with respect to the thickness G of the bladder. Forming a pneumatic tire having a relationship of ≧ 1.5G, a cross-sectional shape of the contact surface with the bladder of the bead ring being a straight line, and an inclination angle α of the contact surface with respect to the tire radial direction being 5 ° to 35 ° Mold.   The molding die for a pneumatic tire according to claim 1, wherein the thickness G of the bladder is 5 to 13 mm.

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