JP2004130605A - Mold for molding tire and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the crack caused from the stepped parts formed to the groove walls of a main groove due to the shift between split molds. <P>SOLUTION: A split mold 3 divided into a plurality of components in the peripheral direction of a tire are attached in the annular state and the main groove molding bones 4 formed to the inner surfaces of these split molds 3 are mutually connected between the split molds. In this mold for molding the tire, the side wall edges (e) provided on the end surfaces of the joints of the main groove molding bones 4 are chamfered and the edge parts in the tire peripheral direction of the chamfered parts 5 are tangentially joined to the side walls 4s of the main groove molding bones 4. Further, the penumatic tire molded by the mold for molding the tire is provided. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a tire mold and a pneumatic tire obtained from the mold, and more particularly to a tire mold capable of preventing a crack generated from a step formed in a groove wall of a main groove due to a deviation between split molds. The present invention relates to a mold and a pneumatic tire obtained from the mold.
[0002]
[Prior art]
A mold for vulcanizing a tire includes a split mold in which a tread forming part is separated on the right and left in an equatorial plane, and a plurality of tread forming parts are arranged at predetermined intervals in a tire circumferential direction as described in Patent Document 1. There is a divided sectional type.
[0003]
In the above-mentioned sectional mold, a plurality of split molds are assembled into a vulcanizer in a ring shape. When assembled in this manner, a gap (particularly a gap in the width direction) is generated at a joint between adjacent split molds. May occur. When the seam between the split molds is displaced in this way, a radial step 82 is formed in the molded tire at a location corresponding to the seam 80 of the groove wall of the main groove 81 as shown in FIG. Is done. However, when such a step 82 is formed on the groove wall, stress concentrates on the groove portion of the step 82 during running of the tire, and a crack 83 originating from the step 82 may occur.
[0004]
However, it is very difficult to assemble a plurality of split molds annularly assembled in a vulcanizer so that there is no level difference for a long time. That is, even if it is assembled so that there is no step at the initial stage, the rattling occurs while the mold is used repeatedly, and the occurrence of the step is inevitable.
[0005]
Therefore, in the conventional tire forming operation, a regular maintenance operation is frequently performed in order to manufacture a tire having no step on the inner wall of the main groove, which causes a decrease in productivity.
[0006]
[Patent Document 1]
JP-A-1-208206
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a tire molding mold and a mold for the tire, which solve the conventional problems described above and can prevent a crack generated from a step formed in a groove wall of a main groove due to a shift between divided molds. It is to provide a pneumatic tire.
[0008]
[Means for Solving the Problems]
The tire molding die of the present invention that achieves the above object is a tire molding in which a plurality of divided molds divided in the tire circumferential direction are assembled in an annular shape, and main groove forming bones on the inner surfaces of the divided molds are connected to each other between the divided molds. In the mold for use, a side wall edge at a joint end face of the main groove forming bone is chamfered, and a circumferential edge of the chamfered portion is tangentially connected to a side wall of the main groove forming bone. It is.
[0009]
Further, in the pneumatic tire of the present invention, the tread portion is formed by a split mold divided into a plurality in the tire circumferential direction, and a groove wall of a main groove provided in the tread portion covers a joint between the split molds. A protrusion is formed as described above, and an edge of the protrusion in the tire circumferential direction is tangentially connected to the groove wall.
[0010]
According to the tire molding die, since the groove wall edge is chamfered at the joint end face of the main groove forming bone, the formed pneumatic tire has a convex portion corresponding to the joint between the split molds of the groove wall of the main groove. And the peripheral edge of the tire in the tire circumferential direction is tangentially connected to the groove wall of the main groove. Concentration does not occur and cracks do not occur. In addition, since such an effect of suppressing cracks can be obtained regardless of whether or not a deviation occurs between the split molds of the tire molding die, frequent maintenance work is not required, and productivity is improved. be able to.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a cross-sectional view showing a main part of a sectional tire mold according to an embodiment of the present invention.
[0012]
1 is an upper mold, 2 is a lower mold, and 3 is a split mold. The upper mold 1 and the lower mold 2 are each formed in a ring shape so as to make one turn in the tire circumferential direction, and form left and right side portions Ts, Ts of the pneumatic tire T. The split mold 3 is divided at equal intervals in the tire circumferential direction as a molding portion of the tread portion Tt, and is formed as a single unit as shown in FIG. A plurality of the divided molds 3 (generally 9 to 12) are assembled in the circumferential direction of the unvulcanized tire into a ring shape in a molding machine.
[0013]
The split mold 3 forms one or a plurality of main groove forming bones 4 on the inner surface (forming surface) in the circumferential direction of the tire, and connects the end faces of the main groove forming bones 4 between the joint surfaces of the split molds 3 and 3. To connect with each other. The shape of the main groove forming bone 4 is not particularly limited, and is formed, for example, in a straight shape, a zigzag shape, a curved shape, an inclined shape, or another bent shape.
[0014]
A chamfered portion 5 is formed on the joint end face 3c of the main groove forming bone 4 by chamfering an edge e where the joint end face 3c intersects with the side wall 4s. The chamfered portion 5 is provided over substantially the entire length in the height direction, leaving only the top of the main groove forming bone 4. In addition, the end of the chamfered portion 5 in the tire circumferential direction is formed in a convex curved surface, and is tangentially connected to the side wall 4s of the main groove forming bone 4 (see FIGS. 3B and 4B). ).
[0015]
As shown in FIG. 3 (A), when the seam end face 3c is viewed from the tire circumferential direction, the boundary L1 between the chamfer part 5 and the seam end face 3c is in the normal direction L0 of the tread. By making β = α with respect to the angle α formed by the side wall 4s of the main groove forming bone 4 with respect to the normal direction L0 of the tread, the width h is made constant in the height direction. Alternatively, as shown in FIG. 4 (A), by making the angle β such that β <α with respect to the angle α, the width h gradually decreases toward the top of the main groove forming bone 4. It is preferable to do so.
[0016]
When the relationship between the angles β and α is β ≦ α as described above, the chamfered portion 5 is not formed at the top of the main groove forming bone 4, but can be formed at an edge other than the top. However, if β> α, the chamfered portion 5 is also formed at the top of the main groove molding bone 4 due to the magnitude relationship between β and α, and as a result, the main groove 24 of the tire after molding is formed. A protrusion 25 (see FIGS. 5 and 6) is formed at the bottom of the groove so as to straddle both groove walls 24s, 24s. On the other hand, since the main groove 24 during rotation of the tire repeats the movement of narrowing the interval between the two groove walls 24s, 24s every time the tire touches the ground, the tearing force repeatedly acts on the convex portion 25 at the groove bottom, so that cracks are easily generated. Become. However, if the relationship of β ≦ α is satisfied as described above, the projection 25 is not formed at the groove bottom, so that cracks are not generated.
[0017]
When an unvulcanized tire is vulcanized and molded by the tire molding die of the present invention having the above-described structure, the pneumatic tire T after molding has land portions such as main grooves and ribs and blocks in a tread portion Tt of FIG. Or it is formed as shown in FIG.
[0018]
FIGS. 5A and 5B show a case where the seam 27 (split position) between the split molds has shifted in the tire width direction, and FIG. 6 shows a normal case where no shift has occurred. In any case, the main groove 24 is formed by the main groove forming bone 4, and the land portion 26 is formed adjacent to the main groove 24.
[0019]
Further, at the joint 27 between the split molds, a convex portion 25 is formed corresponding to the chamfered portion 5 of the main groove forming bone 4, and the convex portion 25 covers the joint 27 between the two split molds. ing. In addition, the convex portion 25 is formed in a concave curved surface in the tire circumferential direction, and is tangentially connected to the groove wall 24s of the main groove 24. Since the convex portions 25 are connected tangentially on the concave curved surface, there is no place where stress concentrates, so that cracks do not occur.
[0020]
As described above, the convex portion 25 is formed so as to cover the joint 27 between the two split molds, and the edge of the convex portion 25 in the tire circumferential direction is connected to the groove wall 24s of the main groove 24 as a smooth concave curved surface. The structure can be achieved by using the tire molding die having the above structure. In addition, this operation and effect can be obtained in the same manner regardless of whether the seam between the split molds is displaced in the tire width direction as shown in FIG. 5 or the normal case where there is no dislocation as shown in FIG. I can do it. Therefore, no crack occurs due to concentration of stress when the tire is used in any of the tires.
[0021]
Further, as described above, in the tire molding die, the angle β formed by the boundary line L1 between the chamfered portion 5 and the seam end face 3c and the angle α formed by the side wall 4s of the main groove forming bone 4 satisfy β ≦ α. Preferably, the relationship is maintained, but this relationship is maintained in the tire after molding. That is, in the tire after molding, the angle formed by the top of the convex portion 25 with respect to the normal direction L0 of the tread is β, and the angle formed by the groove wall 24s of the main groove 24 with respect to the normal direction L0 of the tread. Becomes α, but it is preferable that these angles α and β satisfy the relation β ≦ α as in the case of the mold.
[0022]
By setting the angles α and β in the pneumatic tire in such a manner that β ≦ α, as described above, the protrusion 25 extending between the two groove walls 24 s and 24 s is not formed at the groove bottom. Cracks caused by tearing of the projections 25 can be avoided.
[0023]
【The invention's effect】
As described above, according to the tire molding die of the present invention, since the groove wall edge is chamfered at the joint surface of the main groove forming bone, the molded pneumatic tire is connected between the split molds of the groove walls of the main groove. Is covered by the convex part, and the peripheral edge of the convex part in the tire circumferential direction is connected tangentially to the groove wall of the main groove. No stress concentration occurs at a portion corresponding to the above, and no crack is generated. Further, such an effect of suppressing cracks can be obtained irrespective of whether or not a displacement occurs between the split molds of the tire molding die.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a main part of a tire molding die according to an embodiment of the present invention.
FIG. 2 is an enlarged perspective view showing a split mold of the tire molding die of FIG.
FIG. 3 (A) is an enlarged front view showing a portion of a main groove forming bone of a split mold in a tire molding die of the present invention, and FIG. 3 (B) is a view taken along the line XX of FIG. 3 (A).
FIG. 4A is an enlarged front view showing a portion of a main groove forming bone of a split mold of a tire forming mold according to another embodiment of the present invention, and FIG. 4B is a YY arrow of FIG. FIG.
5A and 5B show a main part of a tire molded by the tire molding die of the present invention, wherein FIG. 5A is a plan view and FIG. 5B is a perspective view.
FIG. 6 is a plan view showing a main part of a tire according to another embodiment, which is molded by the tire molding die of the present invention.
7 (A) to 7 (C) are plan views each showing a main part of a tire according to still another embodiment formed by a tire molding die of the present invention.
FIG. 8 is a plan view showing a main part of a tire molded by a conventional tire molding die.
[Explanation of symbols]
Reference Signs List 1 upper mold 2 lower mold 3 split mold 3c joint end face 4 main groove forming bone 4s side wall 5 chamfered portion e edge 24 main groove 24s groove wall 25 convex portion 26 land portion 27 joint T tire Tt tread portion Ts side portion

Claims (4)

In a tire molding die in which a plurality of divided molds divided in the tire circumferential direction are assembled in an annular shape and the main groove forming bones on the inner surfaces of the divided molds are connected to each other between the divided molds, a side wall at a joint end face of the main groove forming bone is provided. A tire molding die in which an edge is chamfered, and an edge of the chamfered portion in a tire circumferential direction is tangentially connected to a side wall of the main groove forming bone. An angle β formed by a boundary line L1 of a portion where the chamfered portion is connected to a joint end face of the main groove forming bone with respect to a normal direction L0 ° of the tread, and a side wall of the main groove forming bone relative to a normal direction L0 ° of the tread. 2. The tire molding die according to claim 1, wherein a relation of {β ≦ α} is established with respect to the angle α formed. The tread portion is formed by a split mold divided into a plurality in the tire circumferential direction, and a convex portion is formed on a groove wall of a main groove provided in the tread portion so as to cover a joint between the split molds. A pneumatic tire in which a circumferential edge of a tire portion is tangentially connected to the groove wall. The angle β formed by the top of the convex portion with respect to the normal direction L0 of the tread and the angle α formed by the groove wall of the main groove with respect to the normal direction L0 of the tread have the relationship of {β ≦ α}. Item 7. A pneumatic tire according to item 3.

Images