JP2021053927A - Vulcanization mold for producing tire and method for producing pneumatic tire using the same - Google Patents

Abstract

To provide a vulcanization mold for producing a tire capable of effectively suppressing poor appearance caused by air remaining and to provide a method for producing a pneumatic tire using the same.SOLUTION: There is provided a vulcanization mold M for producing a pneumatic tire T, which has a molding surface S for molding the outer surface of a pneumatic tire T, wherein the molding surface S includes a rough surface region X arranged at a part corresponding to an end position of a constituent member of the pneumatic tire T and a smooth region Y arranged at a part other than the rough surface region X and the rough surface region X is made rougher than the smooth region Y.SELECTED DRAWING: Figure 3

Description

The present invention relates to a vulcanization mold for tire production and a method for producing a pneumatic tire using the vulcanization mold for tire production. More specifically, the present invention makes it possible to effectively suppress appearance defects due to air residue. The present invention relates to a vulcanization mold and a method for manufacturing a pneumatic tire using the vulcanization mold.

When manufacturing a pneumatic tire, an unvulcanized pneumatic tire is put into a vulcanization mold, and the pneumatic tire is vulcanized while the pneumatic tire is pressurized by a bladder from the inside. In such a vulcanization step, if air remains between the pneumatic tire and the vulcanization die, there is a problem that an appearance defect occurs, scrap tires are generated, and repair is required. In particular, air tends to remain at the end positions of the tire constituent members (for example, the position of the winding end portion of the carcass layer and the position of the upper end portion of the bead filler), and the appearance is likely to be poor.

As a countermeasure, vent holes are added at places where air pools are likely to occur (see, for example, Patent Documents 1 to 3), but in that case, the man-hours for cutting the spew formed by the vent holes increase. However, there is an inconvenience that the appearance of the product tire is deteriorated due to the increase in spew. Therefore, it is required to suppress appearance defects caused by air residue without increasing the number of vent holes.

Japanese Unexamined Patent Publication No. 2-88310 Japanese Unexamined Patent Publication No. 8-235364 Japanese Unexamined Patent Publication No. 8-47929

An object of the present invention is to provide a vulcanization die for manufacturing a tire capable of effectively suppressing an appearance defect caused by air residue, and a method for manufacturing a pneumatic tire using the vulcanization die.

The vulcanization die for manufacturing a tire of the present invention for achieving the above object has a molding surface for molding the outer surface of the pneumatic tire in the vulcanization die for manufacturing a pneumatic tire. The molded surface includes a rough surface region arranged at a portion corresponding to an end position of a component member of the pneumatic tire and a smooth region arranged at a portion other than the rough surface region. It is characterized in that it is made coarser than the smooth region.

In the method for producing a pneumatic tire of the present invention for achieving the above object, an unvulcanized pneumatic tire is put into the above-mentioned vulcanization mold for tire production, and the pneumatic tire is added from the inside by a bladder. It is characterized in that the pneumatic tire is vulcanized in a pressurized state.

In the tire manufacturing vulcanization die according to the present invention, the rough surface region is arranged at a portion where the molded surface corresponds to the end position of the component member of the pneumatic tire, and the smoothing surface is arranged at a portion other than the rough surface region. The rough surface region is rougher than the smooth region, including the region. The flow of unvulcanized rubber during vulcanization tends to be slower when the molding surface of the vulcanization die is smooth, and faster when the molding surface is rough. In the present invention, by utilizing this characteristic, the surface roughness of the molded surface of the vulcanization die is locally determined in the portion where the appearance defect is likely to occur (the portion corresponding to the end position of the component member of the pneumatic tire). By making the roughness, it is possible to improve the rubber flow of the portion and effectively suppress the retention of air. Further, in the portion where the surface roughness is locally roughened, a gap is formed between the unvulcanized rubber and the molded surface of the vulcanized mold, and air can easily pass through the gap. As a result, it is possible to effectively suppress appearance defects due to air residue while minimizing the number of installed air discharge parts such as vent holes.

In the present invention, the surface roughness of the rough surface region is preferably 1.2 times to 5.0 times the surface roughness of the smooth region. As a result, it is possible to effectively suppress the retention of air and prevent the appearance of the product tire after vulcanization from being deteriorated.

It is preferable that the rough surface region extends in an annular shape along the tire circumferential direction, and the width of the rough surface region in the tire radial direction is in the range of 6 mm to 10 mm. As a result, the retention of air can be effectively suppressed.

The surface roughness of the rough surface region is preferably in the range of 5 μm to 25 μm. As a result, it is possible to effectively suppress the retention of air and prevent the appearance of the product tire after vulcanization from being deteriorated.

The rough surface region preferably has a plurality of regions in which the surface roughness gradually becomes rough from the end portion adjacent to the smooth region toward the central portion. As a result, a smooth rubber flow can be generated. In this case, it is preferable that the rate of change in the surface roughness of the plurality of areas increases as it approaches the central portion. That is, by arranging the arrangement so that the surface roughness increases at an accelerating rate as it approaches the central portion, a smoother rubber flow can be generated. However, it is preferable that the rate of change in the surface roughness of the adjacent compartments of the plurality of compartments is less than twice. If the rate of change in surface roughness of a plurality of compartments is excessive, smooth rubber flow may be hindered at the boundaries of the compartments.

Alternatively, it is preferable that the surface roughness of the rough surface region is continuously and gradually roughened from the end portion adjacent to the smooth region toward the central portion. As a result, a smooth rubber flow can be generated.

According to the present invention, an unvulcanized pneumatic tire is put into the above-mentioned tire manufacturing vulcanization mold, and the pneumatic tire is vulcanized with the pneumatic tire pressed from the inside by a bladder. By doing so, it is possible to manufacture a pneumatic tire while effectively suppressing appearance defects caused by air residue.

In the present invention, the surface roughness is the maximum height roughness Rz defined in JIS-B0601: 2013. In addition, the evaluation method and procedure and the characteristics of the measuring instrument conform to the provisions of JIS-B0633: 2001 and JIS-B0651: 2001.

It is a meridian cross-sectional view which shows an example of the vulcanization die for tire manufacturing used in this invention. It is a meridian semi-cross-sectional view which shows an example of the pneumatic tire manufactured by this invention. It is a top view which shows the side plate of the vulcanization die for tire manufacturing of FIG. It is a top view which shows the specific example of the rough surface region in FIG. FIG. 3 is a plan view showing another specific example of the rough surface region in FIG.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a tire manufacturing vulcanization mold M used in the present invention, FIG. 2 shows an example of a pneumatic tire manufactured in the present invention, and FIG. 3 shows a side of a tire manufacturing vulcanization mold M. The plate is shown, and FIGS. 4 and 5 show specific examples of the rough surface region, respectively. In FIG. 2, CL is the tire center line.

As shown in FIG. 1, in this tire manufacturing vulcanization die M, a pair of side plates 1 and 1 for forming a sidewall portion of a pneumatic tire T and a pair of pair of side plates 1 and 1 for forming a bead portion of the pneumatic tire T are formed. It is composed of bead rings 2 and 2 and a plurality of sectors 3 for forming the tread portion of the pneumatic tire T. In a state where the pair of side plates 1, 1 and the pair of bead rings 2, 2 and the plurality of sectors 3 are combined, the vulcanization die M for tire manufacturing has a tread portion and a sidewall portion of the pneumatic tire T. And a molding surface S for molding the outer surface of the bead portion is formed.

As shown in FIG. 2, the pneumatic tire T includes a tread portion 11 extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions 12 and 12 arranged on both sides of the tread portion 11, and these. It includes a pair of bead portions 13 and 13 arranged inside the sidewall portion 12 in the tire radial direction.

A carcass layer 14 is mounted between the pair of bead portions 13, 13. The carcass layer 14 includes a plurality of carcass cords extending in the tire radial direction, and is wound around the bead core 15 arranged in each bead portion 13 from the inside to the outside of the tire. A bead filler 16 made of a rubber composition having a triangular cross section is arranged on the outer periphery of the bead core 15. On the other hand, a plurality of belt layers 17 are embedded on the outer peripheral side of the carcass layer 14 in the tread portion 11. These belt layers 17 include a plurality of belt cords that are inclined with respect to the tire circumferential direction, and are arranged so that the belt cords intersect each other between the layers.

In the pneumatic tire T having such a configuration, at the time of vulcanization, the position of the end portion in the tire radial direction of the tire component member (for example, the position of the winding end portion 14e of the carcass layer 14 and the upper end portion 16e of the bead filler 16). Air tends to remain in the position), and poor appearance tends to occur in that part. That is, at the position of the winding end portion 14e of the carcass layer 14 and the position of the upper end portion 16e of the bead filler 16, bending and wrinkles are likely to be formed due to the difference in rigidity, and the step due to the member end position is an unvulcanized tire. It easily appears on the surface, and air tends to stay in that part. Examples of the end position of the tire component member in which air tends to remain include the end position of the bead portion reinforcing layer and the side portion reinforcing layer, the splice position of the sidewall rubber layer, and the like.

In view of such a situation, in the above-mentioned vulcanization die M for tire manufacturing, as shown in FIG. 3, a rough surface is formed on the formed surface S at a portion corresponding to the end position of the tire component member in the tire radial direction. Region X is formed. More specifically, when the position where the perpendicular line from the end position of the tire component to the molding surface S intersects the molding surface S is defined as the A portion (see FIG. 1), the rough surface region includes the A portion. It is desirable that X be placed. In FIG. 3, the rough surface region X is formed at a portion corresponding to the position of the winding end portion 14e of the carcass layer 14. Such a rough surface region X extends in an annular shape along the tire circumferential direction. The rough surface region X is preferably continuous along the tire circumferential direction, but may be formed intermittently along the tire circumferential direction. The portion of the molding surface S other than the rough surface region X is the smooth region Y. The rough surface region X is coarser than the smooth region Y.

In the above-mentioned vulcanization die M for manufacturing tires, a rough surface region X is formed at a portion corresponding to the end position of a tire component member on the molded surface S, and a smooth region Y is formed at a portion other than the rough surface region X. At the same time, since the rough surface region X is coarser than the smooth region Y, the rubber flow in the portion where the appearance defect is likely to occur (the portion corresponding to the end position of the tire component member) is improved, and the air stays. Can be effectively suppressed. Further, in the rough surface region X in which the surface roughness is locally roughened, a gap is formed between the unvulcanized rubber and the molding surface S of the vulcanized mold M, and air can easily pass through the gap. As a result, it is possible to effectively suppress appearance defects due to air residue while minimizing the number of installed air discharge parts such as vent holes.

In the tire manufacturing vulcanization die M, the surface roughness (maximum height roughness Rz) of the rough surface region X is 1.2 times to 5. times the surface roughness (maximum height roughness Rz) of the smooth region. It is good that it is 0 times. As a result, it is possible to effectively suppress the retention of air and prevent the appearance of the product tire after vulcanization from being deteriorated. If this magnification is less than 1.2 times, the effect of improving the rubber flow is reduced, and if it is more than 5.0 times, the difference between the rough surface region X and the smooth region Y is too large and the appearance of the product tire is become worse.

In the tire manufacturing vulcanization die M, it is preferable that the rough surface region X extends in an annular shape along the tire circumferential direction, and the width W of the rough surface region X in the tire radial direction is in the range of 6 mm to 10 mm. As a result, the retention of air can be effectively suppressed. Here, if the width W of the rough surface region X is as small as 6 mm, the rough surface region X deviates from the portion where air retention is likely to occur, so that the effect of improving the rubber flow is reduced. The effect of improving rubber flow is reduced. When the position where the perpendicular line from the end position of the tire component to the molding surface S intersects the molding surface S is defined as the A portion, the rough surface region X is within a range of ± 3 mm in the tire radial direction centering on the A portion. Is desirable to be placed.

In the vulcanization die M for manufacturing tires, the surface roughness of the rough surface region X is preferably in the range of 5 μm to 25 μm. As a result, it is possible to effectively suppress the retention of air and prevent the appearance of the product tire after vulcanization from being deteriorated. Here, if the surface roughness of the rough surface region X is less than 5 μm, the effect of improving the rubber flow is lowered, and if it is more than 25 μm, the outer surface of the product tire after vulcanization becomes rough and the appearance is deteriorated. The surface roughness of the flat angle region Y may be 10 μm or less.

The rough surface region X may have a uniform surface roughness over the entire area, but it is also possible to give a gradient to the surface roughness. In FIG. 4, the surface roughness of the rough surface region X gradually becomes rougher from the end portion adjacent to the smooth region Y toward the central portion (that is, the central portion in the width direction of the rough surface region X). It has a plurality of areas X1, X2, X3. In this case, a smooth rubber flow can be generated. In particular, it is preferable that the rate of change in the surface roughness of the plurality of areas X1 to X3 increases as it approaches the central portion. That is, it is preferable that the rate of change in surface roughness between adjacent regions increases as it approaches the central portion. More specifically, for example, the surface roughness of the smooth region Y is Rz (a), the surface roughness of the area X1 of the rough surface region X is Rz (b), and the surface roughness of the area X2 of the rough surface region X is rough. When the surface roughness of the area X3 of the rough surface region X is Rz (d), Rz (b) / Rz (a) <Rz (c) / Rz (b) <Rz ( It is desirable to satisfy a relationship such as d) / Rz (c). By arranging the arrangement so that the surface roughness increases at an accelerating rate as it approaches the central portion of the rough surface region X in this way, a smoother rubber flow can be generated. However, it is preferable that the rate of change in the surface roughness of the adjacent compartments of the plurality of compartments X1 to X3 is less than twice. That is, it is preferable that Rz (b) / Rz (a) <Rz (c) / Rz (b) <Rz (d) / Rz (c) <2.0. If the rate of change in surface roughness of the plurality of compartments X1 to X3 is excessive, smooth rubber flow may be hindered at the boundary between the compartments X1 to X3.

In FIG. 5, the surface roughness of the rough surface region X gradually becomes coarser continuously from the end portion adjacent to the smooth surface region Y toward the central portion (that is, the central portion in the width direction of the rough surface region X). ing. In this case as well, a smooth rubber flow can be generated.

When the pneumatic tire T is manufactured using the tire manufacturing vulcanization die M configured as described above, the unvulcanized pneumatic tire T is charged into the vulcanization die M. Next, the pneumatic tire T is vulcanized by heating the pneumatic tire T from the inside and outside while the pneumatic tire T is pressurized by the bladder B from the inside. At that time, since the rough surface region X is arranged at an appropriate position on the molding surface S of the vulcanization die M for manufacturing the tire, the pneumatic tire T is provided while effectively suppressing the appearance defect caused by the air residue. Can be manufactured.

In the above-described embodiment, an example of a sectional type vulcanization die for tire production is shown, but the present invention can be applied to various vulcanization dies for tire production including a two-piece type.

In manufacturing a pneumatic tire having a tire size of 245 / 40R18, the structure of the vulcanization die for tire manufacturing was made different (Conventional Examples 1 and 2 and Examples 1 to 5). That is, in Conventional Examples 1 and 2 and Examples 1 to 5, the position where the perpendicular line from the bead filler top position toward the molding surface S intersects the molding surface S is defined as the A portion, and the width is 2 mm centered on the A portion. A strip-shaped region a extending in an annular shape in the tire circumferential direction on the molded surface S, a strip-shaped region b having a width of 2 mm adjacent to both outer sides in the width direction, and a strip-shaped region c having a width of 2 mm adjacent to both outer sides in the width direction. When the above is specified, the surface roughness Rz (a) to Rz (c) of these strip-shaped regions a to c are set as shown in Table 1. Further, in the conventional example 2, a plurality of vent holes are provided in the A portion corresponding to the bead filler top position, and in the conventional example 1 and the first to fifth embodiments, a vent hole is provided in the A portion corresponding to the bead filler top position. I didn't install it.

Pneumatic tires are vulcanized using the tire manufacturing vulcanization dies of Conventional Examples 1 and 2 and Examples 1 to 5, and the occurrence rate of appearance defects and the appearance are evaluated by the following evaluation methods. The results are also shown in Table 1.

Incidence of appearance defects:
200 tires were vulcanized by each vulcanization die, and the number of tires having poor appearance due to air residue was measured in the tread portion of the obtained tire to determine the occurrence rate of poor appearance.

Beautiful appearance:
The appearance of the tread portion of the obtained tire was evaluated by 10 panelists, and the total value of the evaluation points was calculated. The evaluation result is shown by an index with Conventional Example 1 as 100. The larger this index value is, the more beautiful the appearance is.

As can be seen from Table 1, in Examples 1 to 5, the incidence of poor appearance was significantly reduced as compared with Conventional Example 1. In Conventional Example 2, although the effect of suppressing poor appearance can be obtained, the appearance of the obtained tire is impaired.

1 Side plate 2 Bead ring 3 Sector M Vulcanization die for tire manufacturing S Molded surface T Pneumatic tire X Rough surface area Y Smooth area

Claims (9)

In a vulcanization die for manufacturing a pneumatic tire, the vulcanization die has a molding surface for molding the outer surface of the pneumatic tire, and the molding surface corresponds to an end position of a component of the pneumatic tire. A vulcanization mold for tire manufacturing, which includes a rough surface region arranged in a portion and a smooth region arranged in a portion other than the rough surface region, and the rough surface region is made rougher than the smooth region. .. The vulcanization die for tire manufacturing according to claim 1, wherein the surface roughness of the rough surface region is 1.2 times to 5.0 times the surface roughness of the smooth region. The tire manufacturing according to claim 1 or 2, wherein the rough surface region extends in an annular shape along the tire circumferential direction, and the width of the rough surface region in the tire radial direction is in the range of 6 mm to 10 mm. Vulcanization mold for. The vulcanization die for tire production according to any one of claims 1 to 3, wherein the surface roughness of the rough surface region is in the range of 5 μm to 25 μm. Any of claims 1 to 4, wherein the rough surface region has a plurality of regions in which the surface roughness gradually becomes rough from the end portion adjacent to the smooth region to the central portion. Vulcanization die for tire manufacturing described in. The vulcanization die for tire manufacturing according to claim 5, wherein the rate of change in surface roughness of the plurality of areas increases as the surface roughness approaches the central portion. The vulcanization die for tire manufacturing according to claim 5 or 6, wherein the rate of change in surface roughness of adjacent sections of the plurality of sections is less than twice. The tire manufacturing according to any one of claims 1 to 4, wherein the rough surface region continuously and gradually becomes roughened from the end portion adjacent to the smoothing region toward the central portion. Vulcanization mold for. The unvulcanized pneumatic tire is put into the tire manufacturing vulcanization mold according to any one of claims 1 to 8, and the pneumatic tire is pressed from the inside by a bladder. A method for manufacturing a pneumatic tire, which comprises performing vulcanization.

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