JP6804953B2 - Manufacturing method of tire vulcanization mold and pneumatic tire - Google Patents

Description

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

A tire vulcanization mold used for vulcanization molding of pneumatic tires, in which a concave groove is formed on the inner surface side of the mold, which is recessed from the molding surface extending in the tire circumferential direction, the tire radial direction, etc., and the location of the concave groove. Is provided with a pilot hole for communicating the inside of the mold and the outside of the mold, and there is a pilot hole in which a vent plug is fitted. The vent plug discharges the air inside the mold to the outside of the mold, and the concave groove allows the air inside the mold to flow toward the vent plug. Conventionally, as described in Patent Document 1 and Patent Document 2, it has been proposed to provide a pilot hole or a vent plug at the intersection of the concave grooves.

By the way, as described in Patent Document 3, traces of the vent plug of the tire vulcanization molding die remain on the surface of the pneumatic tire, which is not preferable in appearance. In addition, there may be a problem that the vent plug comes off from the prepared hole. Further, if the number of vent plugs is large, the manufacturing cost of the tire vulcanization molding die is high. For these reasons, it is preferable that the number of vent plugs provided in the tire vulcanization mold is small.

However, if the number of vent plugs is small, the air inside the mold is not sufficiently discharged during vulcanization molding. As a result, rubber is chipped on the surface of the pneumatic tire after vulcanization and molding.

Japanese Unexamined Patent Publication No. 2015-71251 Japanese Unexamined Patent Publication No. 2013-60181 Japanese Unexamined Patent Publication No. 2013-107451

The present invention has been made in view of the above circumstances, and uses a tire vulcanization mold having a small number of vent plugs and capable of sufficiently discharging air inside the mold during vulcanization molding. An object of the present invention is to provide a method for manufacturing a pneumatic tire.

The tire vulcanization molding die of the embodiment has a molding surface for molding the tire surface, a plurality of recessed grooves recessed from the molding surface, a pilot hole for communicating the inside of the mold and the outside of the mold, and the pilot hole. In a tire vulcanization molding die provided with a vent plug provided inside the tire, the prepared hole and the vent plug straddle the concave groove arranged in parallel with a gap, or one of the concaves. It is characterized in that it is provided so as to straddle the corner portion of the groove and the straight portion of the other concave groove .

The method for manufacturing a pneumatic tire according to the embodiment is a step of setting an unvulcanized tire inside the tire vulcanization molding die and heating and pressurizing the unvulcanized tire to perform vulcanization molding. It is characterized by including.

In the tire vulcanization mold of the embodiment, since the vent plug is provided so as to straddle a plurality of adjacent concave grooves with a gap, the number of vent plugs can be reduced, and the gold is vulcanized during molding. The air inside the mold can be sufficiently discharged.

Further, since the above-mentioned tire vulcanization molding die is used in the method for manufacturing a pneumatic tire of the embodiment, the air inside the mold can be sufficiently discharged with a small number of vent plugs during vulcanization molding.

A half cross-sectional view of the tire vulcanization die 10 of the embodiment in the axial direction. The figure which looked at the molding surface 18 of the side plate 14 from the inside of a mold. An enlarged view of part A surrounded by a square in FIG. FIG. 3 is a cross-sectional view of the tire vulcanization molding die 10 at the position BB in FIG. An enlarged view of the location a in FIG. (A) An example of how the spring vent 30 and the concave groove overlap. (B) Another example of how the spring vent 30 and the concave groove overlap. An enlarged view of location c in FIG. An enlarged view of location d in FIG. A cross-sectional view of the spring vent 30 provided in the prepared hole 20 in the axial direction.

This embodiment will be described with reference to the drawings. It should be noted that the present embodiment is merely an example, and those which have been appropriately modified without departing from the spirit of the present invention shall be included in the scope of the present invention. Further, for convenience of explanation, the drawings may be drawn with exaggerated length, shape, etc., or may be drawn schematically. However, such drawings are merely examples and do not limit the interpretation of the present invention.

FIG. 1 shows the tire vulcanization molding die 10 of the present embodiment. The tire vulcanization mold 10 includes a plurality of sectors 12 arranged on the circumference, a pair of side plates 14 provided on both sides of the circumference formed by the plurality of sectors 12 in the axial direction, and an inner diameter of the side plates 14. It is provided with a pair of bead rings 16 provided on the side. At the time of vulcanization molding, the unvulcanized tire is set in the tire vulcanization molding die 10. The sector 12, the side plate 14, and the bead ring 16 are molding members for molding a pneumatic tire, and the inner surface of these molds is a molding surface 18 for molding the tire surface. The plurality of sectors 12 mainly form the tread portion of the pneumatic tire, the pair of side plates 14 form the side portion of the pneumatic tire, and the pair of bead rings 16 form the bead portion of the pneumatic tire. The material of the sector 12 is not limited, but is, for example, aluminum or an aluminum alloy (for example, an Al—Cu-based, Al—Mg-based, Al—Mn-based, or Al—Si-based alloy). The material of the side plate 14 and the bead ring 16 is not limited, but is, for example, a steel material such as a rolled steel material for general structure (for example, SS400). The material of the side plate 14 and the material of the bead ring 16 may be the same or different.

All or part of the side plate 14 of this embodiment is illustrated in FIGS. 2 to 8. FIG. 2 is a view of the molding surface 18 of the side plate 14 as viewed from the inside of the mold. FIG. 3 is an enlarged view of part A surrounded by a square in FIG.

As shown in FIG. 3, a first recess 22 and a second recess 24 for forming a convex portion on the side portion of the pneumatic tire are provided at a location near the outer diameter end of the molded surface 18 of the side plate 14. ing. The first recess 22 and the second recess 24 have different shapes. The portion indicated by reference numeral 26 in the second concave portion 24 is a convex portion for forming a fine groove in the convex portion of the side portion of the pneumatic tire.

Inside the mold of the side plate 14, a plurality of concave grooves recessed from the molding surface 18 are provided. Normally, the concave groove is provided in a place where air tends to remain until the end during vulcanization molding. In the case of the present embodiment, the first concave groove 61 surrounding the first concave portion 22, the second concave groove 62 on the inner diameter side of the side plate from the first concave groove 61, the third concave groove 63 passing through the first concave portion 22, and the first A fourth concave groove 64 surrounding the two concave grooves 24, a fifth concave groove 65 on the inner diameter side of the side plate from the fourth concave groove 64, and the like are provided. The width of these concave grooves is, for example, 0.3 mm or more and 1.0 mm or less. The depth of these concave grooves is, for example, 0.3 mm or more and 1.0 mm or less. These grooves form ridges on the surface of the pneumatic tire.

As shown in FIG. 3, the first concave groove 61 and the second concave groove 62 are close to each other with a gap on the inner diameter side of the side plate from the first concave portion 22. The first concave groove 61 and the second concave groove 62 are parallel to each other in the vicinity of the adjacent places. Further, the fourth concave groove 64 forms the corner portions 66 and 67 by following the shape of the second concave groove 24. These corner portions 66, 67 and the fifth concave groove 65 are close to each other with a gap.

As shown in FIG. 4, the side plate 14 is provided with a plurality of prepared holes 20. The pilot hole 20 has a circular cross section and extends from the inside of the mold to the outside of the mold. The prepared hole 20 is open to the molding surface 18 of the side plate 14 and the outer surface of the mold. Therefore, the inside of the mold and the outside of the mold are communicated with each other by the prepared hole 20. A vent plug is fitted inside the prepared hole 20 without a gap. The vent plug discharges the air inside the mold to the outside of the mold. In this embodiment, it is assumed that a spring vent 30 described later is provided as a vent plug.

In FIG. 3, the place where the prepared hole 20 and the spring vent 30 are provided overlaps the place a where the first concave groove 61 and the second concave groove 62 are close to each other with a gap, and the third concave groove 63. Place b, place c where the corner 66 and the fifth concave groove 65 are close to each other with a gap, place d where the corner 67 and the fifth concave groove 65 are close to each other with a gap d, the second recess The locations e, f, and g in 24.

At locations a, c, and d where the two concave grooves are close to each other with a gap, the pilot hole 20 and the spring vent 30 are provided so as to straddle the concave grooves. As shown in FIG. 5, at the place a where the first concave groove 61 and the second concave groove 62 are arranged in parallel, the spring vent 30 straddles the first concave groove 61 and the second concave groove 62. It is provided. As a straddling method, there are a form shown in FIG. 5A, a form shown in FIG. 5B, and the like. In FIG. 5A, the spring vent 30 overlaps the first concave groove 61 and the second concave groove 62, and protrudes on both sides in the width direction of the first concave groove 61 and both sides in the width direction of the second concave groove 62. There is. In FIG. 5B, the spring vent 30 overlaps the first concave groove 61 and the second concave groove 62, and is contained in the region sandwiched between the first concave groove 61 and the second concave groove 62. .. There are various straddling methods other than these, but in each case, the overlapping width of the spring vent 30 and the first concave groove 61 is 1/4 or more of the width of the first concave groove 61, and the spring vent. It is desirable that the overlapping width of 30 and the second concave groove 62 is 1/4 or more of the width of the second concave groove 62.

Further, as shown in FIG. 6, at the place c, the spring vent 30 is provided so as to straddle the corner portion 66 and the fifth concave groove 65 of the fourth concave groove 64. Further, as shown in FIG. 7, at the place d, the spring vent 30 is provided so as to straddle the corner portion 67 of the fourth concave groove 64 and the fifth concave groove 65. In these cases as well, the overlapping width of the spring vent 30 and the fourth concave groove 64 is 1/4 or more of the width of the fourth concave groove 64, and the overlapping width of the spring vent 30 and the fifth concave groove 65 is the fifth. It is desirable that it is 1/4 or more of the width of the groove 65.

As shown in FIG. 8, the spring vent 30 includes a housing 40 that is tubular and has a ventilation hole 32 on the inner diameter side, and a stem 50 that is inserted into the inner diameter side of the housing 40 and opens and closes the ventilation hole 32. In FIG. 8, the upper side is the inside of the mold and the lower side is the outside of the mold.

The ventilation hole 32 of the housing 40 extends in the same direction as the prepared hole 20 and communicates the inside of the mold with the outside of the mold. Of the inner diameter surface of the housing 40, that is, the surface forming the ventilation hole 32, the surface continuous from the inner end surface 42 of the mold of the housing 40 toward the depth of the housing 40 (that is, to the outside of the mold) is toward the outside of the mold. It has a tapered surface so that the diameter becomes smaller. This tapered surface is a contact surface 44 that comes into contact with the stem 50 when the ventilation hole 32 is closed. Further, among the inner diameter surfaces of the housing 40, the surface continuous from the contact surface 44 to the outside of the mold (referred to as the intermediate inner diameter surface 45) has a constant diameter. Further, near the outer end of the mold of the housing 40, a small inner diameter portion 46 having an inner diameter smaller than that of the intermediate inner diameter surface 45 is provided.

The stem 50 includes a head 54 having an inner end surface 52 of the mold, a first body portion 56 continuous from the head 54 to the outside of the mold, and a second body portion continuous from the first body portion 56 to the outside of the mold. A portion 57 and a tip portion 58 continuous from the second body portion 57 are provided. The outer diameter surface 53 of the head 54 is tapered so that the diameter decreases toward the outside of the mold. The outer diameter surface 53 is a surface that comes into contact with the contact surface 44 of the housing 40 when the ventilation hole 32 is closed.

The outer diameters of the first body portion 56 and the second body portion 57 are smaller than the inner diameter of the intermediate inner diameter surface 45 of the housing 40, and the outer diameter surfaces of the first body portion 56 and the second body portion 57 and the intermediate inner diameter surface 45 of the housing 40. There is a gap between and. The outer diameter of the second body portion 57 is smaller than that of the first body portion 56, and a part of the second body portion 57 is located on the inner diameter side of the small inner diameter portion 46 of the housing 40. There is a ventilation portion between the second body portion 57 and the small inner diameter portion 46. Due to such a structure, the air that has entered between the outer diameter surface 53 of the head 54 of the stem 50 and the contact surface 44 of the housing 40 is with the outer diameter surfaces of the first body portion 56 and the second body portion 57. It passes between the intermediate inner diameter surface 45, further passes through the ventilation portion between the second body portion 57 and the small inner diameter portion 46, and is discharged from the spring vent 30 to the outside of the mold.

The tip 58 of the stem 50 has a larger outer diameter than the small inner diameter 46 of the housing 40. Since the tip 58 is outside the mold from the small inner diameter 46 of the housing 40, it cannot move inside the mold from the small inner diameter 46. This prevents the stem 50 from falling out of the housing 40 into the mold.

A spring 34 is provided as a part of the spring vent 30 between the small inner diameter portion 46 of the housing 40 and the first body portion 56 of the stem 50. The spring 34 urges the stem 50 toward the inside of the mold. Therefore, the mold inner end surface 52 of the head 54 of the stem 50 always protrudes inward of the mold from the mold inner end surface 42 of the housing 40, and the contact surface 44 of the housing 40 and the outer diameter of the head 54 of the stem 50 A gap is formed between the surface 53 and the ventilation hole 32, and the ventilation hole 32 is open. In the open state of the ventilation holes 32, the air inside the mold passes through the ventilation holes 32 and is discharged to the outside of the mold.

On the other hand, when the stem 50 is pushed to the outside of the mold against the urging force of the spring 34, the contact surface 44 of the housing 40 and the outer diameter surface 53 of the head 54 of the stem 50 come into contact with each other and a gap between them. Is closed, and the ventilation hole 32 is closed. Then, the air inside the mold is not discharged to the outside of the mold.

In a place where the spring vent 30 is provided so as to straddle a plurality of concave grooves or a place where the spring vent 30 is provided so as to overlap one of the concave grooves, the mold inner end surface 42 of the housing 40 of the spring vent 30 is shown in FIG. As shown in 8, it may coincide with the groove bottom 68 of the concave groove, or may protrude from the groove bottom 68 of the concave groove to the inside of the mold (upper side in FIG. 8).

When the pneumatic tire is vulcanized with the tire vulcanization mold 10 having the above structure, the unvulcanized tire is set inside the tire vulcanization mold 10 and the molding member such as the side plate 14 is set. Is maintained at the vulcanization molding temperature. Then, a bladder (not shown) arranged inside the set unvulcanized tire expands, and the surface of the unvulcanized tire is pressed against the molded surface 18. Then, the air remaining inside the tire vulcanization mold 10 is pushed into the plurality of concave grooves and flows in the concave grooves in the direction of the spring vent 30. The air that has reached the periphery of the spring vent 30 exceeds the housing 40 and is discharged from the spring vent 30 to the outside of the mold.

Here, in a place where one spring vent 30 is provided so as to straddle the two concave grooves, the air flowing through the two concave grooves is discharged from the one spring vent 30. For example, at the above location a, the air flowing in the first concave groove 61 and the air flowing in the second concave groove 62 are discharged from the spring vent 30 straddling them. Further, at the above-mentioned places c and d, the air flowing in the fourth concave groove 64 and the air flowing in the fifth concave groove 65 are discharged from the spring vent 30 straddling them. ..

As the air in the mold decreases, the rubber of the unvulcanized tire flows toward the spring vent 30, and finally pushes the stem 50 of the spring vent 30 to the outside of the mold. Then, the ventilation hole 32 is closed, and the air is discharged to the outside of the mold. Then, the unvulcanized tire is heated and pressurized for a predetermined time.

In the tire vulcanization die 10 of the present embodiment, since the spring vent 30 is provided straddling the two adjacent concave grooves with a gap, the spring vent 30 is provided in each of the two concave grooves. The total number of spring vents 30 can be reduced as compared with the case where the spring vents 30 are provided. Therefore, the trace of the spring vent 30 formed on the surface of the pneumatic tire is reduced, and the trouble that the vent plug comes off from the prepared hole is also reduced. Further, the manufacturing cost of the tire vulcanization molding die 10 can be suppressed.

Further, since the air flowing through the two concave grooves can be discharged from the spring vent 30 to the outside of the mold, the air inside the mold can be sufficiently discharged during vulcanization molding. Therefore, it becomes difficult for rubber to be chipped on the surface of the pneumatic tire after vulcanization molding.

Further, according to the tire manufacturing method using the tire vulcanization die 10 of the present embodiment, the trace of the spring vent 30 formed on the surface of the pneumatic tire can be reduced, and the vent plug falls out from the prepared hole. Trouble can be reduced. Further, it is possible to reduce the loss of rubber on the surface of the pneumatic tire after vulcanization molding.

If the overlapping width of the spring vent 30 and the concave groove is 1/4 or more of the width of the concave groove, the air inside the mold can be sufficiently discharged, and the above effect is enhanced.

Various changes can be made to the above embodiment without departing from the spirit of the invention. For example, one spring vent may be provided so as to straddle three or more recessed grooves that are close to each other with a gap. Further, in the sector 12, a spring vent may be provided across a plurality of recessed grooves that are close to each other with a gap as in the above embodiment. Further, the vent plug may be any as long as it can discharge the air inside the mold to the outside of the mold, and is not limited to the spring vent 30 having the structure of the above embodiment. However, it is desirable that the vent plug does not leave a large trace (for example, a whisker-like protrusion called a spew) on the surface of the pneumatic tire.

10 ... Tire vulcanization mold, 12 ... Sector, 14 ... Side plate, 16 ... Bead ring, 18 ... Molding surface, 20 ... Pilot hole, 22 ... 1st concave part, 24 ... 2nd concave part, 26 ... Convex part, 30 ... Spring vent, 32 ... Vent, 34 ... Spring, 40 ... Housing, 42 ... Mold inner end face, 44 ... Contact surface, 45 ... Intermediate inner diameter surface, 46 ... Small inner diameter part, 50 ... Stem, 52 ... Mold Inner end face, 53 ... outer diameter surface, 54 ... head, 56 ... first body, 57 ... second body, 58 ... tip, 61 ... first recess, 62 ... second recess, 63 ... 3 concave grooves, 64 ... 4th concave groove, 65 ... 5th concave groove, 66 ... corner, 67 ... corner, 68 ... groove bottom

Claims (5)

It is provided with a molding surface for molding the tire surface, a plurality of concave grooves recessed from the molding surface, a pilot hole for communicating the inside of the mold and the outside of the mold, and a vent plug provided inside the pilot hole. In tire vulcanization molding dies
The prepared hole and the vent plug are provided so as to straddle the concave grooves arranged in parallel with a gap, or straddle a corner portion of the concave groove on one side and a straight portion of the concave groove on the other side. Tire vulcanization molding die. A plurality of sectors for molding the tread portion of the tire, a pair of side plates for molding the side portion of the tire, and a pair of bead rings for molding the bead portion of the tire are provided, and the prepared hole and the vent plug are at least said. The tire vulcanization molding die according to claim 1, which is provided on the side plate. A plurality of sectors for molding the tread portion of the tire, a pair of side plates for molding the side portion of the tire, and a pair of bead rings for molding the bead portion of the tire are provided, and the prepared hole and the vent plug are at least said. The tire vulcanization molding die according to claim 1, which is provided in the sector. The tire vulcanization molding die according to any one of claims 1 to 3, wherein the overlapping width of the vent plug and the concave groove is 1/4 or more of the width of the concave groove. A step of setting an unvulcanized tire inside the tire vulcanization molding mold according to any one of claims 1 to 4 and heating and pressurizing the unvulcanized tire to perform vulcanization molding. Tire manufacturing method including.

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