JP2018149782A - Tire mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire mold which has excellent gas exhaust property and suppressed spewing.SOLUTION: The invention relates to a mold 2 for producing a tire having grooves on a tread surface. The mold 2 contains a plurality of pieces 12. By arranging the pieces 12, a cavity surface for forming the tread surface is formed. On the cavity surface, projections 18 for forming the grooves are formed. At least one of the projections 18 extends along the border of the pieces 12 and its side face has small protrusions 20. The small protrusions 20 extend from one end toward the other end of the projection 18 in the extension direction of the projection 18.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a mold for manufacturing a tire. More specifically, the present invention relates to a mold for manufacturing a tire having grooves on its tread surface.

  In the tire vulcanization process, the raw cover is heated while being pressurized in a cavity surrounded by a mold and a bladder or a rigid core. The rubber composition of the raw cover flows in the cavity by pressurization and heating. At this time, if air remains between the cavity surface of the mold and the raw cover, a bear is formed on the surface of the tire. There is a need for a mold that prevents the air from remaining.

  In order to prevent air from remaining, there is a mold having a plurality of pieces. In the vulcanization process, the inner surface of the piece comes into contact with the tread surface of the raw cover. In this mold, a cavity surface for forming a tread surface is formed by arranging pieces. A gap (referred to herein as an exhaust slit) is provided between this piece and an adjacent piece or another adjacent mold component. The air between the low cover and the cavity surface moves to the exhaust slit and is exhausted from the exhaust slit. The examination about the mold provided with a plurality of pieces is indicated by JP, 2007-237708, A.

JP 2007-237708 A

  When the tread of the tire has a groove, a protrusion for forming the groove is provided on the cavity surface in the mold for manufacturing the tire. The protrusion can prevent air between the raw cover and the cavity surface from moving to the exhaust slit. In order to promote the movement of air, a hole (cross vent) penetrating the ridge may be provided at the base of the ridge. In this mold, the rubber composition may enter the hole and spew may be formed on the tire. From the viewpoint of better appearance and drainage, it is required to suppress spewing.

  An object of the present invention is to provide a mold for a tire that has excellent exhaust performance and suppresses the occurrence of spew.

  The present invention relates to a mold for manufacturing a tire having grooves on a tread surface. The mold includes a plurality of pieces. A cavity surface for forming the tread surface is formed by arranging the pieces. A protrusion for forming the groove is provided on the cavity surface. At least one of the ridges extends along the boundary of the piece and has a small protrusion on its side. The small protrusion extends in the extending direction of the protrusion from one end of the protrusion to the other end.

  In a tire mold in which a ring-shaped main groove extending in the circumferential direction and a sub-groove extending inclined with respect to the circumferential direction are engraved on the tread surface, preferably, at least one of the sub-grooves is formed. The ridge extends along the boundary of the piece and includes the small protrusion on the side surface.

  Preferably, a protrusion for forming all the sub-grooves extends along the boundary of the piece and includes the small protrusion on a side surface thereof.

  Preferably, the protrusion extending along the boundary of the piece, including the small protrusion on a side surface thereof, and the protrusion for forming the sub groove is in contact with the protrusion for forming the main groove or Do not cross.

  Preferably, the width W of the small protrusion is 0.4 mm or greater and 1.0 mm or less.

  Preferably, the height T of the small protrusion is not less than 0.2 mm and not more than 0.6 mm.

  Preferably, a plurality of the small protrusions are provided in parallel at an equal pitch on the side surface of the protrusion.

  Preferably, the distance L from the root of the ridge to the small protrusion positioned closest to the root is 2 mm or less.

  Preferably, in the cross section perpendicular to the extending direction of the protrusion, the shape of the small protrusion is a polygon, a rectangle, or a semicircle whose width is narrowed in the height direction.

  The present invention relates to a method for manufacturing a tire having a groove on a tread surface. This manufacturing method includes a step of obtaining a raw cover and a step of vulcanizing the raw cover. In the step of vulcanizing the raw cover, a plurality of pieces are provided, a cavity surface for forming a tread surface is formed by arranging these pieces, and a protrusion for forming the groove on the cavity surface is formed. At least one protrusion extending along the boundary of the piece and provided with a small protrusion on a side surface of the protrusion, the small protrusion extending from one end to the other end of the protrusion. In the mold extending in the extending direction, the raw cover is pressurized and heated.

  In the tire mold according to the present invention, a cavity surface for forming a tread surface is formed by arranging pieces. In the vulcanization process, the air between the raw cover and the cavity surface moves to the exhaust slit and is exhausted from the exhaust slit. In this mold, among the ridges for forming grooves on the tread surface, at least one ridge extends along the boundary of the pieces and has small projections on the side surfaces thereof. The small protrusion extends in the extending direction of the protrusion from one end of the protrusion to the other end. The air remaining inside this ridge (opposite the boundary of the piece) moves to the end of the ridge through the gap between this small protrusion and the raw cover, and further to the exhaust slit located at this boundary. Can move. In this mold, this protrusion is unlikely to obstruct air movement. In this mold, the remaining of air is suppressed. This mold is excellent in exhaustability. In this mold, it is not necessary to provide a cross vent at the base of the protrusion. In this mold, the generation of spew is suppressed.

FIG. 1 is a plan view illustrating a part of a tire mold according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a perspective view showing a segment of the mold of FIG. FIG. 4 is a view of the segment of FIG. 3 as viewed from the inside in the radial direction. FIG. 5 is an enlarged view of a part of FIG. FIG. 6 is a cross-sectional view in which a part of the cross section taken along the line VI-VI in FIG. 5 is enlarged. 7 is a cross-sectional perspective view of the cross section of FIG. FIG. 8 is an enlarged cross-sectional view of a part of FIG.

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

  FIG. 1 shows a tire mold 2. In FIG. 1, the direction perpendicular to the paper surface is the axial direction. The direction indicated by the double arrow A is the circumferential direction. FIG. 2 is a cross-sectional view taken along line II-II in FIG. In FIG. 2, the direction indicated by the arrow X is the radial direction, the direction indicated by the arrow Y is the axial direction, and the direction perpendicular to the paper surface is the circumferential direction. FIG. 2 also shows a raw cover R (unvulcanized tire).

  The mold 2 includes a large number of segments 4, a pair of side plates 6, and a pair of bead rings 8. The planar shape of the segment 4 is substantially arcuate. A large number of segments 4 are arranged in a ring shape. A minute gap is provided between the segments 4 adjacent to each other. The number of segments 4 is usually 3 or more and 20 or less. The side plate 6 and the bead ring 8 are substantially ring-shaped.

  FIG. 3 is a perspective view showing the segment 4 of the mold 2 of FIG. In FIG. 3, the direction indicated by the arrow X is the radial direction, and the direction indicated by the arrow Y is the axial direction. The direction indicated by the double arrow A is the circumferential direction. The segment 4 includes a holder 10 and a large number of pieces 12. A large number of pieces 12 arranged in the circumferential direction are mounted on the holder 10. In the vulcanization process, the inner surface 14 of each piece 12 comes into contact with the tread surface of the raw cover. The inner surface 14 of the piece 12 forms part of the cavity surface. In the mold 2, a cavity surface for forming a tread surface is formed by arranging the pieces 12. The holder 10 is made of steel or aluminum alloy. The piece 12 is made of steel or an aluminum alloy.

  FIG. 4 is a view of the segment 4 of FIG. 3 as viewed from the inside in the radial direction. In this view, the inner surface 14 of the paralleled pieces 12 is shown. In FIG. 4, the direction indicated by the double arrow A is the circumferential direction, the direction indicated by the arrow Y is the axial direction, and the direction perpendicular to the paper surface is the radial direction.

  As shown in FIG. 4, each piece 12 extends in the axial direction. The axial length of the piece 12 is longer than the circumferential width. In this mold 2, a plurality of pieces 12 extending in the axial direction are arranged in the circumferential direction. A gap is provided between the pieces 12 adjacent to each other. Although not shown in the drawings, a gap is also provided between the piece 12 and the components of the other mold 2 (in this embodiment, the side plate 6) located outside the piece 12 in the axial direction. These gaps are referred to herein as exhaust slits 16. The exhaust slit 16 surrounds the periphery of the piece 12. The exhaust slit 16 is located at the boundary of the piece 12.

  Although not shown, the tread surface of the tire manufactured with this mold 2 has a ring-shaped main groove extending in the circumferential direction and a sub-groove (also referred to as lug groove) extending inclined with respect to the circumferential direction. It is carved. Specifically, the sub-groove refers to a groove whose extending direction is inclined by 30 ° or more with respect to the circumferential direction and whose width is 3 mm or more. The length of the minor groove is typically 2 cm or more. The mold 2 is for a tire having a main groove and a sub groove. As shown in FIG. 4, on the cavity surface, a protrusion 18 for forming a main groove (referred to as a main protrusion 18a) and a protrusion 18 for forming a sub groove (a sub protrusion 18b) And a protrusion 18c for forming other narrow grooves. The main protrusion 18 a is divided at the boundary of the pieces 12. In each piece 12, a part of the main protrusion 18a is located.

  FIG. 5 shows an enlarged part of FIG. In this figure, the vicinity of the auxiliary protrusion 18b is shown. As shown in the figure, the secondary protrusion 18 b extends along the boundary of the piece 12. The auxiliary protrusion 18 b extends along one circumferential end of the piece 12. In other words, the position of the boundary between the piece 12 and the piece 12 is determined so that the boundary is along the auxiliary protrusion 18b. The auxiliary protrusion 18b has a rod shape extending in the axial direction. The length of the auxiliary protrusion 18b is typically 2 cm or more. In this embodiment, the auxiliary protrusion 18b does not contact the main protrusion 18a and does not intersect. In other words, in this tire, the minor groove does not contact and intersect with the main groove.

  FIG. 6 shows an enlarged part of a cross section taken along line VI-VI in FIG. This is a cross-sectional view taken along a plane perpendicular to the extending direction of the auxiliary protrusion 18b. In FIG. 6, the direction indicated by the arrow A is the circumferential direction, the direction indicated by the arrow X is the radial direction, and the direction perpendicular to the paper surface is the axial direction. 7 is a cross-sectional perspective view of the cross section of FIG.

  As shown in FIGS. 6 and 7, a small protrusion 20 is provided on the side surface of the auxiliary protrusion 18 b. A plurality of small protrusions 20 are juxtaposed on the side surface of the auxiliary protrusion 18b. In this cross section, the shape of the small protrusion 20 is a trapezoid. This trapezoid has a narrow width in the height direction. Each small protrusion 20 extends in the extending direction of the auxiliary protrusion 18b. The small protrusion 20 extends from one end of the auxiliary protrusion 18b to the other end.

  As described above, in this embodiment, the cavity surfaces for forming the tread surface are configured by arranging the pieces 12 in a line in the circumferential direction. A plurality of pieces arranged in the axial direction may be arranged in the circumferential direction to form a cavity surface. For example, the cavity surface may be configured by arranging two pieces arranged in the axial direction in the circumferential direction. The cavity surface may be configured by arranging three or more pieces arranged in the axial direction in the circumferential direction.

  The tire manufacturing method using the mold 2 includes a step of obtaining the raw cover R and a step of vulcanizing the raw cover R. In the process of obtaining the low cover R, tire components such as a carcass, a belt, and a tread are laminated on the outer surface of the former drum. Thereby, the raw cover R is obtained. In the process of vulcanizing the raw cover R, the raw cover R is put into the mold 2. The raw cover R is pressed against the cavity surface of the mold 2 by a bladder and pressurized. At the same time, the raw cover R is heated. The rubber composition flows by pressurization and heating. The rubber causes a crosslinking reaction by heating, and a tire is obtained. Instead of the bladder, a rigid core may be used.

  Hereinafter, the operation effect of the present invention will be described.

  In the tire mold 2 according to the present invention, a cavity surface for forming a tread surface is formed by arranging pieces 12. In the vulcanization process, the air between the raw cover and the cavity surface moves to the exhaust slit 16 and is discharged from the exhaust slit 16. In the mold 2, at least one of the protrusions 18 for forming a groove on the tread surface extends along the boundary of the piece 12, and includes a small protrusion 20 on the side surface. The small protrusion 20 extends in the extending direction of the protrusion 18 from one end of the protrusion 18 to the other end. The air remaining on the inner side of the protrusion 18 (opposite the boundary of the piece 12) moves to the end of the protrusion 18 through the gap between the small protrusion 20 and the raw cover, and is further located at this boundary. It can move to the exhaust slit 16. In the mold 2, the protrusion 18 is unlikely to obstruct air movement. In the mold 2, the remaining of air is suppressed. This mold 2 is excellent in exhaustability. In the mold 2, it is not necessary to provide a cross vent at the base of the protrusion 18. In this mold 2, the generation of spew is suppressed.

  As shown in FIG. 4, it is preferable that the boundaries of the pieces 12 are determined such that all the sub-projections 18 b are along the boundaries of the pieces 12, and the small projections 20 are provided on these sub-projections 18 b. As described above, the sub-groove typically has a length of 2 cm or more. The length of the minor groove is long. The auxiliary protrusion 18b tends to be an obstacle to air movement. By making all these sub-projections 18b along the boundaries of the pieces 12 and providing the sub-projections 20 on the sub-projections 18b, air can be effectively moved to the exhaust slit 16. This mold 2 is excellent in exhaustability.

  The number N of small protrusions 20 formed on the side surface of one protrusion 18 is preferably 2 or more. By setting the number N of the small protrusions 20 to 2 or more, the small protrusions 20 effectively contribute to air movement. Air can be effectively discharged by these small protrusions 20. In this respect, the number N is more preferably 3 or more. The number N of the small protrusions 20 is preferably 10 or less. By setting the number N of the small protrusions 20 to 10 or less, the cost required for processing the small protrusions 20 is suppressed. In this mold 2, an appropriate cost is maintained.

  As FIG. 4 shows, it is preferable that the sub protrusion 18b does not contact or cross | intersect the main protrusion 18a. In the auxiliary protrusion 18b, the air moved by the small protrusion 20 is not prevented from further movement by the main protrusion 18a that contacts or intersects with the auxiliary protrusion 18b. In this mold 2, air is effectively discharged.

  In FIG. 6, the double-headed arrow D is the distance between the exhaust slit 16 located at the boundary of the piece 12 and the protrusion 18 extending along this boundary. The distance D is preferably 2.0 mm or less. By setting the distance D to 2.0 mm or less, the air that has moved to the end of the protrusion 18 through the gap between the small protrusion 20 and the raw cover inside the protrusion 18 is exhausted at this boundary. It can easily move to the slit 16 for use. This ridge 18 is unlikely to obstruct air movement. In the mold 2, the remaining of air is suppressed. In this respect, the distance D is more preferably 1.0 mm or less.

  In FIG. 6, a double-headed arrow L is a distance from the base of the protrusion 18 to the small protrusion 20 positioned closest to the base. The distance L is measured along the normal of the inner surface 14 of the piece 12 at the position of the protrusion 18 when the protrusion 18 is not present. This distance L is the height from the root of the protrusion 18 to the middle point in the width direction of the small protrusion 20 along the normal. The distance L is preferably 2 mm or less. By setting the distance L to 2 mm or less, the small protrusions 20 effectively contribute to air discharge.

  FIG. 8 is an enlarged view of the vicinity of the small protrusion 20 of FIG. In FIG. 8, the direction indicated by the double arrow A is the circumferential direction, and the direction indicated by the arrow X is the radial direction. When a plurality of small protrusions 20 are located on the side surface of one protrusion 18, it is preferable that these small protrusions 20 are arranged at an equal pitch. In FIG. 8, the double arrow P represents the pitch between the small protrusions 20 at this time. The pitch P is preferably 0.6 mm or more, and preferably 1.2 mm or less. By doing in this way, these small protrusion 20 contributes effectively to discharge | emission of air.

  In FIG. 8, the double arrow W represents the width at the base of the small protrusion 20. The width W is preferably 0.4 mm or more. By setting the width W to 0.4 mm or more, the small protrusions 20 effectively contribute to air movement. Air can be effectively discharged by the small protrusions 20. In this respect, the width W is more preferably equal to or greater than 0.5 mm. The width W is preferably 1.0 mm or less. By setting the width W to 1.0 mm or less, the recess formed in the tire groove by the small protrusions 20 is hardly noticeable. This tire maintains an excellent appearance. In this respect, the width W is more preferably equal to or less than 0.8 mm.

  In FIG. 8, the double arrow H represents the height of the small protrusion 20. The height H is measured along the normal of the side surface of the ridge 18 when there is no small protrusion 20. The height H is preferably 0.2 mm or more. By setting the height H to 0.2 mm or more, the small protrusions 20 effectively contribute to air movement. Air can be effectively discharged by the small protrusions 20. In this respect, the height H is more preferably equal to or greater than 0.3 mm. The height H is preferably 0.6 mm or less. By setting the height H to 0.6 mm or less, the cost required for processing the small protrusions 20 is suppressed. In this mold 2, an appropriate cost is maintained. In this respect, the height H is more preferably equal to or less than 0.5 mm.

  From the viewpoint of effectively contributing to air discharge, the cross-sectional shape of the small protrusion 20 is preferably a polygon, a rectangle, or a semicircle whose width is narrowed in the height direction. From this point of view, the cross-sectional shape of the small protrusion 20 is more preferably a trapezoid as shown in FIGS.

  In FIG. 8, symbol θ represents an angle formed by two legs in the cross section of the trapezoidal small protrusion 20. From the viewpoint of effectively contributing to the discharge of air, the angle θ is preferably 30 ° or more, and preferably 80 ° or less.

  In the above-described embodiment, in the segment 4, the plurality of pieces 12 extending in the axial direction are arranged in the circumferential direction. In the segment, a plurality of pieces extending in the circumferential direction may be arranged in the axial direction. Even in this case, the small protrusion is provided on the protrusion extending along the boundary of the piece. By doing so, this protrusion is unlikely to obstruct air movement. In this mold, the remaining of air is suppressed. This mold is excellent in exhaustability. In this mold, it is not necessary to provide a cross vent at the base of the ridge. In this mold, the generation of spew is suppressed.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
The mold shown in FIGS. 1-7 was manufactured. The specifications of this mold are shown in Table 1. This mold is for a 155 / 65R14 size tire. This tire includes a main groove and a sub-groove on the tread surface. In this mold, all the secondary ridges are along the boundaries of the pieces. All sub-projections were provided with small protrusions. This secondary protrusion does not contact or intersect with the main protrusion. This is indicated as “None” in the “Contact with main ridge” column of the table. The secondary protrusion of this mold has eight small protrusions on its side surface. The distance L from the root of the ridge to the small protrusion located closest to the root was 1 mm. The other seven small protrusions were arranged at an equal pitch from the small protrusion toward the tip of the ridge. This pitch P was set to 0.8 mm. The width W of each small protrusion was 0.4 mm. The cross-sectional shape of each small protrusion was an isosceles trapezoid. The angle θ formed by the two trapezoidal legs was 60 °.

[Comparative Example 1]
A mold of Comparative Example 1 was manufactured in the same manner as Example 1 except that the sub-projections did not have small protrusions.

[Comparative Example 2]
The mold of Comparative Example 2 was manufactured in the same manner as in Example 1 except that the secondary protrusion did not have a small protrusion and a cross vent was provided at the base of the auxiliary protrusion. The presence of a cross vent on the secondary protrusion is shown as “present” in the “cross vent presence / absence” column of the table.

[Example 2-3]
A mold of Example 2-3 was manufactured in the same manner as in Example 1 except that the number N of small protrusions was changed to the value shown in Table 1. In changing the number N of small protrusions, the distance L and the pitch P are not changed.

[Example 4-7]
A mold of Example 4-7 was manufactured in the same manner as Example 1 except that the height H of the small protrusion was changed to the value shown in Table 2.

[Example 8]
A mold of Example 8 was manufactured in the same manner as in Example 1 except that the auxiliary protrusions were extended to contact with the main protrusions. The fact that the secondary ridge is in contact with the main ridge is indicated as “present” in the “contact with the main ridge” column of the table.

[Air exhaustability]
A tire was prototyped using the produced mold. With each mold, five tires were prototyped, and the amount of bear generated in the tire was visually confirmed for the fifth tire. The reason why only the fifth tire was used for the evaluation was to evaluate the performance of a tire manufactured with a stable temperature during vulcanization. The result is shown as an index in Table 1-2. The larger the value, the less the occurrence of bears, that is, the better the air discharge. Larger values are preferred.

[Presence / absence of spew]
The tires that confirmed the air exhaustability were also checked for the presence or absence of spew in the secondary groove. The results are shown in Table 1-2.

  As shown in Table 1-2, the mold of the example has a higher evaluation than the mold of the comparative example. From this evaluation result, the superiority of the present invention is clear.

  The mold described above can be applied to the manufacture of various tires.

2 ... mold 4 ... segment 6 ... side plate 8 ... bead ring 10 ... holder 12 ... piece 14 ... cavity surface 16 ... exhaust slit 18 ... projection Article 18a ... Main projection 18b ... Sub projection 20 ... Small projection

Claims (10)

A mold for manufacturing a tire with grooves on the tread surface,
With multiple pieces,
A cavity surface for forming the tread surface is formed by arranging the pieces,
A protrusion for forming the groove is provided on the cavity surface,
At least one of the ridges extends along the boundary of the piece and has a small projection on its side;
The tire mold in which the small protrusion extends in the extending direction of the protrusion from one end of the protrusion to the other end. A mold for manufacturing a tire in which a ring-shaped main groove extending in the circumferential direction and a secondary groove extending obliquely with respect to the circumferential direction are engraved on the tread surface,
2. The tire mold according to claim 1, wherein a protrusion for forming at least one sub-groove extends along the boundary of the piece and includes the small protrusion on a side surface thereof.   The tire mold according to claim 2, wherein a protrusion for forming all the sub-grooves extends along a boundary of the piece and includes the small protrusion on a side surface thereof.   Claim that extends along the boundary of the piece, includes the small protrusion on the side surface thereof, and the protrusion for forming the secondary groove does not contact or intersect with the protrusion for forming the main groove Item 2. A tire mold according to Item 2 or 3.   The tire mold according to any one of claims 1 to 4, wherein a width W of the small protrusion is 0.4 mm or greater and 1.0 mm or less.   The tire mold according to any one of claims 1 to 5, wherein a height H of the small protrusion is 0.2 mm or greater and 0.6 mm or less.   The tire mold according to any one of claims 1 to 6, wherein a plurality of the small protrusions are provided in parallel at an equal pitch on a side surface of the protrusion.   The tire mold according to any one of claims 1 to 7, wherein a distance L from a root of the ridge to the small protrusion positioned closest to the root is 2 mm or less.   The cross section perpendicular to the extending direction of the ridge, the shape of the small protrusion is a polygon, a rectangle, or a semicircle whose width is narrowed in the height direction. The mold for tires described in 1. A method of manufacturing a tire with grooves on the tread surface,
Process to obtain raw cover,
And a step of vulcanizing the raw cover,
In the step of vulcanizing the raw cover, a plurality of pieces are provided, a cavity surface for forming a tread surface is formed by arranging these pieces, and a protrusion for forming the groove on the cavity surface is formed. At least one protrusion extending along the boundary of the piece and provided with a small protrusion on a side surface of the protrusion, the small protrusion extending from one end to the other end of the protrusion. A method for manufacturing a tire, wherein the raw cover is pressurized and heated in a mold extending in an extending direction.

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