JP6159235B2 - Tire vulcanization mold and tire manufacturing method - Google Patents

Description

  The present invention relates to a tire vulcanization mold in which a plurality of vent holes are provided on a tread molding surface in contact with a tread portion of a tire, and a tire manufacturing method using the same.

  Conventionally, in a tire vulcanization mold used for vulcanization molding of a pneumatic tire, for example, as described in Patent Documents 1 to 3, a plurality of vent holes are provided on a tread molding surface in contact with a tread portion of the tire. ing. According to such a configuration, excess air between the tire and the tread molding surface is discharged to the outside of the mold, preventing the occurrence of air accumulation that causes rubber deficiency called lightness and bear, and good tire appearance Can be formed.

  By the way, the tread part of the unvulcanized tire set in the tire vulcanization mold is not in contact with the tread molding surface all at once. It contacts in order toward the part. For this reason, in the shoulder region near the ground contact end, it tends to take time until the required amount of rubber is filled, compared with the center region near the tire equator. As a result, in the shoulder region, the rubber flow is reduced and air accumulation tends to occur, and there is a possibility that the appearance of the tire may be deteriorated due to the rubber deficiency caused by the rubber flow.

JP-A-8-267457 JP 7-88846 A JP 63-78709 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a tire vulcanization mold capable of suppressing the occurrence of air accumulation and a tire manufacturing method using the same.

  The above object can be achieved by the present invention as described below. That is, the tire vulcanization mold according to the present invention is a tire vulcanization mold in which a plurality of vent holes are provided in a tread molding surface in contact with a tread portion of the tire, and the tread molding surface is on the center side in the tire width direction. Compared with the diameter of the vent hole provided in the center region, the diameter of the vent hole provided in the shoulder region on the tire width direction end side of the tread molding surface is set larger.

  According to such a configuration, in the shoulder region of the tread molding surface, the rubber during the vulcanization molding is actively drawn, and the time until the required amount of rubber is filled can be shortened. As a result, in the shoulder region, the rubber flow is promoted to disperse the air, so that the occurrence of air accumulation is suppressed. Further, in the center region where the diameter of the vent hole is relatively small, the above-described effect of accelerating the filling of the rubber into the shoulder region can be ensured without wastefully drawing the rubber.

  In the present invention, when a position that is 2/3 of the ground contact half-width from the tire equator toward the outer side in the tire width direction is a boundary between the center region and the shoulder region, the vent provided in the inner portion in the tire width direction in the center region Compared to the diameter of the hole, the diameter of the vent hole provided on the outer side in the tire width direction in the center region is set larger, and compared to the diameter of the vent hole provided on the inner side in the tire width direction in the shoulder region. The diameter of the vent hole provided on the outer side in the tire width direction in the shoulder region may be set large.

  Thereby, in each of the center region and the shoulder region, an effect of promoting the rubber flow based on the difference in the diameter of the vent hole can be obtained, and the occurrence of air accumulation can be suppressed. Here, the ground contact half width refers to half of the ground contact width that is the distance in the tire width direction between the ground contact ends. In the case of a tire shape employing a so-called round shoulder in which the outer surface of the tread portion and the outer surface of the sidewall portion are connected via an arc, the position of the ground contact end on the tread molding surface is determined by the midpoint of the arc. In the case of a tire shape that employs a so-called square shoulder where the outer surface of the tread portion and the outer surface of the sidewall portion intersect each other at an angular edge, the position of the ground contact end is determined by the edge.

  Further, in the above case, the diameter of the vent hole provided in the tire width direction inner portion in the shoulder region is set larger than the diameter of the vent hole provided in the tire width direction outer portion in the center region. It is preferable that According to such a configuration, the diameter of the vent hole gradually increases from the tire equator toward the ground contact edge, and as the tire width direction goes outward, the pulling of rubber during vulcanization molding increases and the rubber flow is promoted. Therefore, the effect of suppressing air accumulation is exhibited well.

  An annular protrusion for forming a main groove extending along the tire circumferential direction is provided on the tread molding surface, and is provided in an inner area in the tire width direction with respect to an area adjacent to the tire width direction across the protrusion. The diameter of the vent hole provided in the outer region in the tire width direction may be set larger than the diameter of the vent hole. As described above, with respect to the pattern in which the tread portion of the tire is divided in the tire width direction by the main groove, it is conceivable that the diameter of the vent hole is changed according to the division.

  The diameter of the vent hole is larger than the dimension formed by incrementing the diameter of the vent hole closest to the tire outermost point by 0.1 mm every time the distance in the tire radial direction with respect to the tire outermost point exceeds 2 mm. It is preferable to set it large. According to such a configuration, as the distance in the tire radial direction with respect to the tire outermost point (so-called drop amount) increases, the rubber flow at the time of vulcanization molding increases and the rubber flow is promoted. The effect of suppressing air accumulation is exhibited well.

  The tire manufacturing method according to the present invention includes the steps of setting an unvulcanized tire in the cavity of the tire vulcanization mold described above, and performing vulcanization by applying heat and pressure to the unvulcanized tire. According to this method, as described above, the rubber flow can be promoted to prevent the occurrence of air accumulation, so that a good tire appearance can be formed.

1 is a longitudinal sectional view schematically showing an example of a tire vulcanizing mold according to the present invention. Fig. 1 is an enlarged view of a main part showing the tread molding surface of Fig. 1. Schematic diagram for explaining drop amount

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

  In the tire vulcanization mold 10 shown in FIG. 1, an unvulcanized tire T whose outline is indicated by a broken line is set with the tire shaft up and down. That is, in FIG. 1, the vertical direction is the tire width direction, and the horizontal direction is the tire radial direction. The tire vulcanization mold 10 includes a tread molding surface 1 that is in contact with the tread portion of the tire T set in the cavity 30. The tread molding surface 1 has a plurality of vent holes that allow the inside (cavity 30) and the outside of the mold 10 to communicate with each other in order to discharge excess air between the tire T and the tread molding surface 1 during vulcanization molding. 11 is provided.

  The tire vulcanization mold 10 includes side plates 91 and 92 for forming the sidewall portion of the tire T, and an annular tread ring 93 for forming the tread portion of the tire T. The tread molding surface 1 is formed on the inner surface of the tread ring 93 and has a profile formed by smoothly connecting a plurality of arcs having different curvature radii. Although not shown in FIG. 1, the tread molding surface 1 is provided with a concavo-convex pattern corresponding to the tread pattern, and a groove portion is formed by a protrusion 2 (see FIG. 2) protruding from the tread molding surface 1. The land portion is formed by the recess 3 (see FIG. 2) divided by the projection 2.

  The mold 10 is a so-called segmented mold, and a tread ring 93 is constituted by a plurality of sectors divided in the tire circumferential direction. When the mold is opened, the side plate 92 and the tread ring 93 are lifted, and the sectors are displaced radially outward so that each sector spreads radially, so that the tire can be taken in and out. When the molds are clamped, the tread ring 93 continues in an annular shape by gathering the sectors, and the tread molding surface 1 can be brought into close contact with the outer surface of the tread portion of the tire T as shown in FIG.

  In the tread molding surface 1, the diameter of the vent hole 11 provided in the shoulder region Sh on the end side in the tire width direction is larger than the diameter of the vent hole 11 provided in the center region Ce on the center side in the tire width direction. Is set to large. For example, as shown in an enlarged view in FIG. 2, the vent closest to the ground contact CE is larger than the diameter φ11 a of the vent hole 11 a closest to the tire equator TE among the plurality of vent holes 11 opened on the tread molding surface 1. A diameter φ11d of the hole 11d is set to be large (that is, φ11a <φ11d).

  In this mold 10, the rubber at the time of vulcanization molding is actively drawn in the shoulder region Sh based on the diameter difference of the vent hole 11 as described above until the required amount of rubber is filled in the recess 3. You can speed up the time. As a result, the rubber flow in the recess 3 is promoted and the air is dispersed, and the occurrence of air accumulation in the recess 3 can be suppressed. Further, in the center region Ce where the diameter of the vent hole 11 is relatively small, the rubber is not drawn unnecessarily, and the effect of accelerating the rubber filling in the shoulder region Sh can be secured, and the rubber filling speed between both the regions can be ensured. Can be made uniform.

  In this way, the structure in which the diameter of the vent hole 11 is different focuses on the action of drawing the rubber and promoting the rubber flow in the recess 3 rather than the original action of releasing excess air. The air in the recess 3 is dispersed by actively moving the rubber. By appropriately dispersing the air in the recess 3, the occurrence of air accumulation is suppressed, and as a result, it is possible to prevent a rubber deficiency in a land portion in a tread portion such as a block or a rib and obtain a good tire appearance.

  The vent hole 11 is opened at the bottom surface of the recess 3. As described above, the vent hole 11 promotes the rubber flow in the recess 3 by pulling in the rubber. Therefore, even if the air pool is likely to occur at the corner of the recess 3, It is not necessary to set the vent hole 11 at the corner. Of course, the vent hole 11 may be set at the corner of the recess 3.

  The diameters φ11a to φ11d of the vent hole 11 are preferably 0.6 mm or more in order to ensure the exhaust performance of the vent hole 11. The diameter φ11d of the largest vent hole 11d is preferably 0.8 mm or more in order to secure the effect of promoting rubber flow in the recess 3 by pulling in rubber. Further, the diameters φ11a to φ11d of the vent hole 11 are preferably 2.2 mm or less, and more preferably 2.0 mm or less, in order to avoid complication of the rubber projection trimming operation called spew. The spew is formed on the surface of the tread portion of the tire after vulcanization molding by the rubber flowing into the vent hole 11.

  In the present embodiment, the center region Ce and the shoulder region Sh have a boundary at a position that is 2/3 of the contact half width from the tire equator TE toward the outer side in the tire width direction (right direction in FIG. 2). That is, the distance in the tire width direction from the tire equator TE to the boundary is 2/3 of the distance in the tire width direction from the tire equator TE to the ground contact CE. Since the tire shape of the present embodiment is a so-called round shoulder, the ground contact end CE is determined by the midpoint SP of an arc interposed between the outer surface of the tread portion and the outer surface of the sidewall portion.

  The inner portion Cei and the outer portion Ceo are regions when the center region Ce is equally divided in the tire width direction in the half width of the tread molding surface 1 shown in FIG. 2, and the inner portion Shi and the outer portion Sho are the same. This is a region when the shoulder region Sh is divided into two equal parts in the tire width direction. The diameter φ11a of the vent hole 11a provided in the inner part Cei may be the same as the diameter φ11b of the vent hole 11b provided in the outer part Ceo, but in this embodiment, the diameter φ11b is set larger than the diameter φ11a. (That is, φ11a <φ11b).

  Further, the diameter φ11c of the vent hole 11c provided in the inner part Shi may be the same as the diameter φ11d of the vent hole 11d provided in the outer part Sho, but in this embodiment, the diameter φ11d is larger than the diameter 11c. It is set (that is, φ11c <φ11d). Further, in the present embodiment, the diameter φ11c of the vent hole 11c provided in the inner portion Shi is set larger than the diameter φ11b of the vent hole 11b provided in the outer portion Ceo (that is, φ11b <φ11c). ). In FIG. 2, one vent hole 11 is provided in each of the inner part Cei, the outer part Ceo, the inner part Shi, and the outer part Sho, but the present invention is not limited to this.

  According to such a configuration, each of the center region Ce and the shoulder region Sh has an effect of promoting rubber flow based on the difference in diameter of the vent holes 11 and can suppress the occurrence of air accumulation. In addition, the diameter of the vent hole 11 increases stepwise from the tire equator TE toward the ground contact edge CE, and as the rubber width increases toward the outer side in the tire width direction, the rubber flow at the time of vulcanization molding increases and the rubber flow is promoted. In addition, the effect of suppressing air accumulation is exhibited well. A large number of the vent holes 11 are arranged at intervals in the tire circumferential direction, and it is desirable that the above-described relationship between the diameter dimensions satisfies the average value of the diameters of the vent holes 11 provided in each region.

  The diameter of the vent hole 11 is equal to the diameter of the vent hole 11 closest to the tire outermost point MP every time the distance in the tire radial direction (so-called drop amount) with respect to the tire outermost point MP exceeds 2 mm. In the present embodiment, it is preferable that the dimension is set to be larger than the dimension obtained by incrementing φ11a) by 0.1 mm. For example, the diameter φ11d of the vent hole 11d in the schematic diagram of FIG. 3 is preferably φ11a + 0.1 mm or more when the drop amount D is 2 mm or more and less than 4 mm, and is preferably φ11a + 0.2 mm or more when the drop amount D is 4 mm or more and less than 6 mm. When D is 6 mm or more and less than 8 mm, φ11a + 0.3 mm or more is preferable.

  The tire T formed by the mold 10 may have a tire shape employing a so-called square shoulder, and in this case, the ground contact CE is formed by an angular edge where the outer surface of the tread portion and the outer surface of the sidewall portion intersect. Is determined. Further, the tread pattern of the tire T is not particularly limited, and therefore the uneven pattern provided on the tread molding surface 1 is not limited. In the case of a pattern in which the tread portion is not completely divided in the tire width direction by the main groove (for example, a pattern in which the main groove extends in a V shape with respect to the tire circumferential direction), A boundary with the shoulder region can be defined.

  When an annular protrusion for forming a main groove extending along the tire circumferential direction is provided on the tread molding surface 1, that is, when the protrusion 2 forms an annular shape along the tire circumferential direction, the tread of the tire T The portion is a pattern that is completely divided in the tire width direction by the main groove. In such a case, the vent provided in the outer region in the tire width direction compared to the diameter of the vent hole 11 provided in the inner region in the tire width direction with respect to the region adjacent in the tire width direction with the protrusion 2 therebetween. The diameter of the hole 11 may be set to be large.

  Even in the other half width of the tread molding surface 1 not shown in FIG. 2, a plurality of vent holes 11 can be provided as described above. Although FIG. 2 shows four types of vent holes having different diameters, the present invention is not limited to this. Therefore, for example, while satisfying the relationship of φ11a <φ11d in FIG. 2, φ11a = φ11b and φ11c = φ11d is established, or φ11a = φ11b = φ11c is established, or φ11b = φ11c = φ11d is established. It may be a thing. These vent holes 11 do not have to appear in the same tire meridian cross section.

  In the above-described embodiment, an example in which the vent hole is a round hole having a constant diameter has been described. However, the present invention is not limited to this. In this case, the diameter of the vent hole is measured not at the counterbore, but at the main body of the venthole (part from the counterbore). The diameter of the counterbore is considered to have little effect on the action of pulling rubber during vulcanization molding to promote the rubber flow in the recess.

  The method for manufacturing a tire using the mold 10 includes a step of setting the unvulcanized tire T in the cavity 30 of the mold 10 and performing vulcanization by applying heat and pressure to the unvulcanized tire T. According to this mold 10, it is possible to prevent the occurrence of air accumulation in the recess 3 as described above, and therefore it is possible to manufacture a pneumatic tire having a good tire appearance with no rubber deficiency in the land portion of the tread portion.

  The tire vulcanization mold according to the present invention is the same as a normal tire vulcanization mold except that the vent hole provided on the tread molding surface is configured as described above, and has a conventionally known shape, material, mechanism, etc. Can be employed in the present invention.

  The present invention is not limited to the embodiment described above, and various improvements and modifications can be made without departing from the spirit of the present invention. Therefore, for example, in the above-described embodiment, the tire vulcanization mold is a segmented mold. However, the present invention is not limited thereto, and may be a so-called two-piece mold that is divided into two at the center of the tread portion. .

  In order to specifically show the configuration and effects of the present invention, vulcanization molding of tires was performed to confirm the occurrence of air accumulation. The tire vulcanization mold used for the evaluation was provided with the tread molding surface shown in FIG. In the molded tire, if there is a rubber deficiency in the tread part, it is evaluated as `` x '' as air retention occurred during vulcanization molding, and if there is no rubber deficiency and a good tire appearance is obtained, vulcanization It was evaluated as “◯” because no air accumulation occurred during molding.

  As shown in Table 1, the air pool was generated in Comparative Examples 1 and 2, whereas the occurrence of the air pool was suppressed in Examples 1 and 2, and the rubber flow was improved by the configuration of the vent hole as described above. It is thought that it was done.

DESCRIPTION OF SYMBOLS 1 Tread molding surface 2 Protrusion 3 Recess 10 Tire vulcanization mold 11 Vent hole 30 Cavity Ce Center area Sh Shoulder area

Claims (6)

  In a tire vulcanization mold in which a plurality of vent holes are provided on a tread molding surface in contact with a tread portion of the tire, compared to a diameter of a vent hole provided in a center region on the center side in the tire width direction of the tread molding surface. A tire vulcanization mold, wherein a diameter of a vent hole provided in a shoulder region on the tire width direction end portion side of the tread molding surface is set to be large. When the position that is 2/3 of the ground contact half width from the tire equator toward the outer side in the tire width direction is the boundary between the center region and the shoulder region,
Compared to the diameter of the vent hole provided at the inner side in the tire width direction in the center region, the diameter of the vent hole provided at the outer side in the tire width direction within the center region is set large.
The diameter of the vent hole provided in the outer side in the tire width direction in the shoulder region is set larger than the diameter of the vent hole provided in the inner side in the tire width direction in the shoulder region. Tire vulcanization mold.   The diameter of the vent hole provided in the tire width direction inner side part in the shoulder region is set larger than the diameter of the vent hole provided in the tire width direction outer side part in the center region. Tire vulcanization mold. An annular projection for forming a main groove extending along the tire circumferential direction is provided on the tread molding surface,
Regarding the region adjacent to the tire width direction across the protrusion, the diameter of the vent hole provided in the outer region in the tire width direction is set larger than the diameter of the vent hole provided in the inner region in the tire width direction. The tire vulcanization mold according to any one of claims 1 to 3.   The diameter of the vent hole is larger than the dimension formed by incrementing the diameter of the vent hole closest to the tire outermost point by 0.1 mm every time the distance in the tire radial direction with respect to the tire outermost point exceeds 2 mm. The tire vulcanization mold according to any one of claims 1 to 4, which is set to a large size.   Manufacturing a tire including a step of setting an unvulcanized tire in a cavity of the tire vulcanization mold according to any one of claims 1 to 5 and subjecting the unvulcanized tire to heating and pressurization to perform vulcanization. Method.

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