JP5653749B2 - Tire vulcanization molds and motorcycle tires - Google Patents

Description

  The present invention relates to a tire vulcanization mold for manufacturing a motorcycle tire and a motorcycle tire.

  Tire vulcanization molds include two-piece molds that are divided into two parts and multi-part molds that are divided into three or more parts. It is divided into a side plate (for example, Patent Document 1).

  When adopting a structure with a jointless band (JLB), a high modulus cord cut breaker, etc. in order to reduce the outer diameter change when vulcanizing the raw tire, the amount of change in the outer diameter of the tire is It becomes smaller than the groove depth. For this reason, when it manufactures using a 2 piece type metal mold | die, since a green tire will contact the convex part of a mold side tread surface at the time of a mold closing, a multi-part type metal mold | die is used.

  On the other hand, motorcycle tires for running on rough terrain represented by motocross tires are generally manufactured with a two-piece mold because tires with a bias structure that do not have a breaker or the like are the mainstream. .

  However, in recent years, a structure with high breaker rigidity aimed at improving performance such as traction and grip has been studied also for motorcycle tires for running on rough terrain.

  Therefore, in the production of motorcycle tires for running on rough terrain, it is necessary to use a multi-part mold.

JP-A-8-216620

  When manufacturing an on-road motorcycle tire using a multi-part mold, the split position of the mold is set at the shoulder edge portion.

  However, since motorcycle tires for running on rough terrain are configured with blocks having shoulder portions that are discontinuous, when the block portion is formed of a tread segment, as shown in FIG. The lower end has a sharp shape (Y portion surrounded by a circle in FIG. 4B). For this reason, there is a problem that the segment strength is insufficient, and the segment strength is lost during transportation or vulcanization.

  Therefore, as shown in FIG. 5, it is conceivable to prevent a decrease in mold strength by setting a tread segment so as to cover the entire block portion of a motorcycle tire for traveling on rough terrain.

  However, in such a case, since the split position of the mold is located at the base of the shoulder block, the minute step line generated in the tire due to the presence of the split position is at the base of the shoulder block where a large force is applied during traveling. As a result, there is a problem that cracks are more likely to occur in the vicinity of the base of the shoulder portion and in the sidewall portion when it is greatly deformed during traveling. In FIG. 4, 4 is a vulcanizing mold, 41 is a tread segment, 42 is a side plate, 43 is a groove for forming a block provided in the block portion, 44 is a pointed portion at the lower end of the tread segment 41, T Is a tire to be vulcanized. In FIG. 5, 5 is a vulcanization mold, 51 is a tread segment, 52 is a side plate, and 53 is a groove for forming a block provided in the block portion.

  In view of the above problems, the present invention provides a vulcanization mold for a tire and a motorcycle that does not decrease the mold strength and can suppress the occurrence of cracks in the vicinity of the shoulder base and the side wall. It is an object to provide a tire.

The invention described in claim 1
A tire vulcanization mold divided into a tread segment and a pair of side plates for manufacturing a motorcycle tire,
The motorcycle tire has a convex built-up portion that is formed between shoulder blocks and that connects the shoulder blocks.
The depth of the groove for forming the build-up portion provided on the mold cavity surface is set to be shallower than the virtual groove bottom line on the tire side extending along the bottom surface of the build-up portion,
The split position between the tread segment and the side plate is set so as to be positioned between the apex of the build-up portion and the base point of the shoulder block in the tire radial direction, excluding the base point of the shoulder block. The tire vulcanization mold is characterized.

The invention described in claim 2
The split position is located within a range of 25% of the distance between the apex and the base point from the midpoint between the apex of the built-up portion and the base point of the shoulder block in the tire radial direction. The tire vulcanization mold according to claim 1.

The invention according to claim 3
A motorcycle tire manufactured by the tire vulcanization mold according to claim 1 or 2,
The motorcycle tire is characterized in that a minute step line generated by the presence of the split position of the tire vulcanizing mold is located between the top of the build-up portion and the base point of the shoulder block.

The invention according to claim 4
The two-wheeled vehicle tire according to claim 3, wherein one or a plurality of layers of breakers are provided.

The invention described in claim 5
The motorcycle tire according to claim 4, wherein the breaker is made of a non-stretchable material.

The invention described in claim 6
The motorcycle tire according to claim 4 or 5, wherein the breaker has a jointless band structure.

The invention described in claim 7
The motorcycle tire according to any one of claims 3 to 6, wherein the shoulder block has a height of 8 to 19 mm.

  According to the present invention, there are provided a vulcanization mold for a tire and a tire for a motorcycle, in which the mold strength does not decrease and the occurrence of cracks in the vicinity of the shoulder base and the side wall can be suppressed. be able to.

1 is a cross-sectional view schematically showing a tire vulcanization mold according to an embodiment of the present invention. It is sectional drawing for demonstrating the split position of the vulcanization die for tires concerning an embodiment of the invention. It is a fragmentary sectional view of a vulcanization mold showing typically a split position of a vulcanization mold of a comparative example. It is sectional drawing which shows the conventional tire vulcanization metal mold | die (comparative example), Comprising: (a) is sectional drawing of the location with the groove | channel for block formation, (b) does not have the groove | channel for block formation It is sectional drawing of a location. It is sectional drawing which shows typically the other conventional vulcanization mold for tires (comparative example).

  Hereinafter, the present invention will be described with reference to the drawings based on embodiments.

1. FIG. 1 is a cross-sectional view schematically showing a tire vulcanization mold according to the present embodiment, and FIG. 2 is a plan view of the tire vulcanization mold according to the present embodiment. It is sectional drawing for demonstrating a position.

  As shown in FIGS. 1 and 2, the tire vulcanization mold is a multi-part mold for manufacturing a motorcycle tire for a motocross, and includes a tread segment 11 and upper and lower side plates 12. I have.

  As shown in FIG. 1 and FIG. 2, the motorcycle tire T for motocross has a convex built-up portion 14 formed between the shoulder blocks 13 to make the shoulder blocks 13 continuous.

  A first groove 14 a is formed on the cavity surface of the tread segment 11, and a second groove 14 b continuous with the first groove 14 a is formed on the cavity surface of the upper and lower side plates 12. 14a and the second groove 14b coincide with each other to form a built-up portion forming groove 14c.

  Further, the depth of the deepest portion of the groove 14 c is set to be shallower than the virtual groove bottom line L on the tire T side extending along the bottom surface of the built-up portion 14.

  1 and 2, A is a shoulder edge, B is an apex of the built-up portion, C is a shoulder block base point (root), X is a split position, and 13 a is a cavity surface of the tread segment 11. It is a groove | channel for shoulder block 13 formation formed in this.

  The split position X between the tread segment 11 and the side plate 12 is set to an intermediate position between the vertex and the base point C excluding the vertex B of the built-up portion 14 and the base point C of the shoulder block 13 in the tire radial direction.

  Thus, the tire vulcanization mold according to the present embodiment is adjacent to the shoulder block forming groove 13a (the rightmost groove in the figure) along the tire circumferential direction (perpendicular to the paper surface). The built-up portion 14 is provided between the shoulder block forming groove 13a and the shoulder block forming groove 13a, and the depth of the groove in the built-up portion 14 is shallower than the virtual groove bottom line L. The split position X is set so as to be positioned between the apex B of the built-up portion 14 and the base point C of the shoulder block.

  Next, a preferable position of the split position X will be described. In FIG. 2, 15 is a breaker or belt, x is the distance in the radial direction of the tire between the apex B of the built-up portion and the base point C of the shoulder block, and y is the base point of the apex B of the build-up portion 14 and the base point of the shoulder block. This is the distance between the midpoint of C and the split position X, and the other symbols are the same as in FIG.

  The split position X is such that the radial distance y between the apex B of the built-up portion and the base point C of the shoulder block and the base point C of the shoulder block is y ≦ 1 / 4x. Is preferably set such that y ≦ 1 / 5x. Thus, by setting the split position X at a position sufficiently away from both the apex B of the built-up portion and the base point C of the shoulder block, it is possible to manufacture a motorcycle tire in which cracks are more reliably suppressed. it can. In FIG. 2, the split position X is located on the upper side by the distance y from the middle point, but may be located on the lower side by the distance y from the middle point.

2. Motorcycle Tire Next, a motorcycle tire manufactured by the tire vulcanization mold according to the present embodiment will be described.

  As described above, the motorcycle tire T has the convex built-up portion 14 formed between the shoulder blocks 13 to make the shoulder blocks 13 continuous with each other, and the split position of the tire vulcanization mold The minute step line generated due to the presence of is located between the apex of the built-up portion and the base point of the shoulder block.

  Regarding the height of the shoulder block, since the occurrence of cracks is suppressed even when a circumferential force is applied to the shoulder block, the height of the shoulder block can be set to a sufficient height. Specifically, it is preferably set to 8 to 19 mm.

  By setting the height of the shoulder block to 8 mm or more, the soil can be sufficiently scraped when traveling on rough terrain. For this reason, lack of traction and grip are not caused. Further, by setting the height of the shoulder block to 19 mm or less, the block rigidity is not lowered.

  In the case of a bias structure, the motorcycle tire preferably employs a single-layer or multiple-layer breaker (cut breaker). The breaker cord is preferably made of a material that is difficult to stretch, such as steel or polyamide resin. Further, in the case of a radial structure, the motorcycle tire preferably employs JLB.

(Basic effects of the present embodiment)
(1) Since the motorcycle tire according to the present embodiment has a convex built-up portion that is formed between shoulder blocks and makes the shoulder blocks continuous, a particularly large external force acts on the tread block. The shoulder block can be reinforced. And since the minute step line generated by the presence of the split position of the tire vulcanization mold is located between the top of the built-up part and the base point of the shoulder block, there is a crack near the base of the shoulder part and the side wall part. Can be prevented from occurring.

(2) In the tire vulcanization mold according to the present embodiment, the split position between the tread segment and the side plate is located between the apex of the built-up portion and the base point of the shoulder block in the tire radial direction. Therefore, a sharp point with low strength is not formed at the tip of the tread segment. For this reason, the mold strength does not decrease.

  Further, since the tire vulcanization mold according to the present embodiment is divided into multiple parts, when vulcanizing a raw tire equipped with a JLB having a small outer diameter change during vulcanization, a high modulus cut breaker, or the like, The mold can be closed without contacting the tire with the convex portion of the tread surface. Therefore, it is suitable for vulcanization molding of tires with improved traction performance and grip performance.

(Examples 1-4, Comparative Examples 1-4)
Examples 1 to 4 and Comparative Examples 1 to 4 are examples in which motorcycle tires for motocross were produced using different tire vulcanization molds. The size of the motorcycle tire is 120 / 80-19.

1. Used Mold Examples 1 to 4 used the mold of the present embodiment described above shown in FIGS. 1 and 2.
Comparative Example 1 uses a two-piece mold, Comparative Example 2 uses the mold shown in FIG. 4, Comparative Example 3 uses the mold shown in FIG. 5, and Comparative Example 4 uses FIG. The mold shown was used. The mold shown in FIG. 3 is obtained by matching the split position X with the apex B of the built-up portion.

2. Details of evaluation The mold strength of the shoulder block, the mold insertion of the raw tire having a breaker, and the crack durability at the split position were evaluated.

  The mold strength of the shoulder block portion was determined by the degree of occurrence of deformation and breakage during mold transportation and manufacturing.

  The mold insertability of the raw tire having a breaker was determined by a tire defect generated by contact between the raw tire and the mold tread portion when the mold was closed.

  The test method for crack durability is a motorcycle that runs on a dry road surface for 60 minutes using a motocross bike (displacement of 450 cc) on a circuit (motocross course) of about 2 minutes for one lap. The cracks that occurred at the split position of the tire were examined.

4). Evaluation Results Table 1 shows the evaluation results of the examples and comparative examples together with the configuration of the vulcanization mold. In addition, the evaluation result was represented by a score. The higher the score, the better.

4). Consideration From Table 1, Comparative Example 2 is inferior to Examples 1 to 4 in terms of the mold strength of the shoulder block portion, and Comparative Example 1 is in Examples 1 to 4 with respect to the mold insertability of a raw tire having a breaker. It is understood that Comparative Examples 3 and 4 are inferior to Examples 1 to 4 in terms of crack durability at the split position.

  From this, it can be seen that Examples 1 to 4 have high scores in all evaluations and are good in all points.

  While the present invention has been described based on the embodiments, the present invention is not limited to the above embodiments. Various modifications can be made to the above-described embodiment within the same and equivalent scope as the present invention.

1, 4, 5 Vulcanizing mold 11, 41, 51 Tread segment 12, 42, 52 Side plate 13 Shoulder block 13a Groove 14 for shoulder block formation Overlaying portion 14a First groove 14b Second groove 14c Groove 15 Breaker 32 Side wall portion 43 Groove 44 for block formation Pointed portion 53 at the lower end of the tread segment A groove for block formation A Shoulder edge B Overlay portion apex C Shoulder block base point L Virtual groove bottom line T Tire X Split position x Overlay portion The distance y in the tire radial direction between the apex of the shoulder block and the base point of the shoulder block
Distance of

Claims (7)

A tire vulcanization mold divided into a tread segment and a pair of side plates for manufacturing a motorcycle tire,
The motorcycle tire has a convex built-up portion that is formed between shoulder blocks and that connects the shoulder blocks.
The depth of the groove for forming the build-up portion provided on the mold cavity surface is set to be shallower than the virtual groove bottom line on the tire side extending along the bottom surface of the build-up portion,
The split position between the tread segment and the side plate is set so as to be positioned between the apex of the build-up portion and the base point of the shoulder block in the tire radial direction, excluding the base point of the shoulder block. Characteristic tire vulcanization mold.   The split position is located within a range of 25% of the distance between the apex and the base point from the midpoint between the apex of the built-up portion and the base point of the shoulder block in the tire radial direction. The tire vulcanization mold according to claim 1. A motorcycle tire manufactured by the tire vulcanization mold according to claim 1 or 2,
A tire for a motorcycle, wherein a minute step line generated by the presence of a split position of the tire vulcanization mold is located between a top of the build-up portion and a base point of the shoulder block.   The tire for a motorcycle according to claim 3, wherein one or a plurality of breakers are provided.   The motorcycle tire according to claim 4, wherein the breaker is made of a non-stretchable material.   The motorcycle tire according to claim 4 or 5, wherein the breaker has a jointless band structure.   The motorcycle tire according to any one of claims 3 to 6, wherein a height of the shoulder block is 8 to 19 mm.

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