JP2018030279A - Mold for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold 22 for a tire capable of exhausting air sufficiently while suppressing a formation of a spew.SOLUTION: A mold 22 includes a cavity surface 24 that forms an external surface of a tire. The mold 22 includes a main body 32 and a columnar vent piece 34. The main body 32 includes a hole 36 penetrating the main body 32. The vent piece 34 is inserted into the hole 36. The vent piece 34 includes an end surface 42 and a groove 52 extending from the end surface 42 in a lengthwise direction of the vent piece 34. The end surface 42 is part of the cavity surface 24.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a tire mold.

  The mold includes a cavity surface that forms the outer surface of the tire. In manufacturing the tire, the outer surface of the raw cover (unvulcanized tire) is pressed against the cavity surface. Air existing between the raw cover and the cavity surface and air remaining in the raw cover are discharged to the outside of the mold. If the air is insufficiently discharged, the appearance quality and durability of the tire may be impaired.

  In order to sufficiently discharge air, a hole (also referred to as a vent hole) may be provided in the mold. In this case, the exhaust of air is urged through the hole, but the rubber of the raw cover flows into the hole and a spew is formed. For this reason, the process for removing this spew is required for manufacture of a tire. From the viewpoint of appearance quality, the smaller the number of spews formed, the better.

  Various studies have been made on molds in order to sufficiently discharge air while suppressing spew formation. An example of this study is disclosed in Japanese Patent Application Laid-Open No. 2015-071251. In this publication, a vent piece is considered as a component for sufficiently discharging air while suppressing spew formation.

  As a vent piece, a vent piece utilizing the characteristics of a spring for opening and closing a valve, that is, a spring vent is known. The spring vent has a large outer diameter because of its structure, and there is a restriction on the location where the spring belt can be placed in the mold. The structure of the spring vent is complicated, and the maintenance of the spring vent is not easy.

  FIG. 8 shows the vent piece 2 described in the above publication. The vent piece 2 is not provided with a spring. In the vent piece 2, a vent line 8 is provided between the head 4 and the body portion 6. The body portion 6 is provided with a saw cut 10 extending in the length direction of the vent piece 2. In the vent piece 2, the air that has passed around the head 4 is guided to the saw cut 10 via the vent line 8.

JP2015-071251A

  There is room for consideration regarding techniques for sufficiently discharging air while suppressing spew formation.

  An object of the present invention is to provide a tire mold that can sufficiently discharge air while suppressing spew formation.

  The tire mold according to the present invention includes a cavity surface that forms the outer surface of the tire. This mold includes a main body and a columnar vent piece. The main body includes a hole penetrating the main body. The vent piece is passed through the hole. The vent piece includes an end face and a groove extending from the end face in the length direction of the vent piece. The end surface is a part of the cavity surface.

  Preferably, in the tire mold, the width of the groove is not less than 0.2 mm and not more than 0.4 mm, and the depth of the groove is not less than 0.02 mm and not more than 0.04 mm.

  Preferably, in the tire mold, the vent piece includes 6 or more and 8 or less grooves. These grooves are spaced around the vent piece.

  Preferably, in the tire mold, the vent piece includes a first grip portion, an intermediate portion, and a second grip portion arranged in the length direction of the vent piece from the end face side. The intermediate portion is thinner than the first grip portion and the second grip portion.

  Preferably, in the tire mold, the thickness of the intermediate portion is not less than ½ and not more than 2/3 of the thickness of the first gripping portion.

  Preferably, in the tire mold, the length of the intermediate portion is not less than 1/3 and not more than 1/2 of the length of the vent piece.

  Preferably, in the tire mold, the ratio of the apparent sectional area of the groove to the sectional area of the hole is 0.5% or less.

The tire manufacturing method according to the present invention includes:
(1) a step of preparing a raw cover;
(2) a step of putting the raw cover into a mold having a cavity surface forming the outer surface of the tire and a vent hole extending outward from the cavity surface; and (3) pressurizing the raw cover in the mold. And a step of heating. In this manufacturing method, the mold includes a main body and a columnar vent piece. The main body has a hole penetrating the main body, and the vent piece is passed through the hole. The vent piece includes an end face and a groove extending from the end face in the length direction of the vent piece. The end surface is a part of the cavity surface.

  In the tire mold according to the present invention, the end surface of the vent piece is a part of the cavity surface. The groove of the vent piece extends from the end face in the length direction of the vent piece. In this mold, a space corresponding to the groove of the vent piece, that is, a vent hole extends from the cavity surface in the length direction of the vent piece. In this mold, air is sufficiently discharged. In addition, in this mold, the rubber of the low cover does not easily flow into the vent hole. In this mold, air is sufficiently discharged while suppressing spew formation. The appearance of tires manufactured with this mold is of high quality. ADVANTAGE OF THE INVENTION According to this invention, the mold for tires which can fully discharge | emit air is obtained, suppressing formation of a spew.

FIG. 1 is a plan view showing 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. 3A is a plan view of the vent piece, and FIG. 3B is a front view of the vent piece. FIG. 4 is an enlarged view showing a part of the vent piece shown in FIG. 3. FIG. 5 is a perspective view of segments constituting the mold of FIG. FIG. 6 is an external view showing a part of the cavity surface of the mold. 7 is a cross-sectional view taken along line VII-VII in FIG. FIG. 8 is a front view showing a conventional vent piece.

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

  A part of the tire mold 22 is shown in FIGS. In FIG. 1, the direction perpendicular to the paper surface is the axial direction of the mold 22. The direction indicated by the double arrow A is the circumferential direction of the mold 22. In FIG. 2, the vertical direction is the axial direction of the mold 22, and the horizontal direction is the radial direction of the mold 22. The direction perpendicular to the paper surface is the circumferential direction of the mold 22. The axial direction of the mold 22 corresponds to the axial direction of the tire, the circumferential direction of the mold 22 corresponds to the circumferential direction of the tire, and the radial direction of the mold 22 corresponds to the radial direction of the tire.

  In FIG. 2, what is indicated by R is a raw cover. The raw cover R is a tire before vulcanization. The raw cover R is in an uncrosslinked state. The tire is composed of a plurality of rubber members such as treads, sidewalls, and beads. In manufacturing the tire, a plurality of rubber members are assembled, and the raw cover R is prepared.

  In manufacturing the tire, the raw cover R is put into the mold 22. In FIG. 2, the raw cover R is located inside the mold 22. Although not shown, a bladder (or a rigid core) is located further inside the raw cover R. The raw cover R put into the mold 22 is placed in the space between the mold 22 and the bladder (or rigid core), that is, in the cavity.

  In manufacturing the tire, the raw cover R is pressurized and heated in the mold 22. The rubber composition of the raw cover R flows by pressurization and heating. The rubber causes a crosslinking reaction by heating, and a tire is obtained. The outer surface of the raw cover R contacts the mold 22. Thereby, the outer surface of the tire is shaped. Of the inner surface of the mold 22, the portion 24 that contacts the raw cover R is particularly referred to as a cavity surface. The cavity surface 24 forms the outer surface of the tire. The mold 22 includes a cavity surface 24 that forms the outer surface of the tire. By using the mold 22 having an uneven pattern on the cavity surface 24, an uneven pattern is formed on the outer surface of the tire. The inner surface of the raw cover R is in contact with the bladder (or rigid core). Thereby, the inner surface of the tire is shaped.

The manufacturing method of this tire is:
(1) a step of preparing a raw cover R;
(2) including a step of putting the raw cover R into the mold 22 and (3) a step of pressing and heating the raw cover R in the mold 22

  As described above, the mold 22 shown in FIGS. 1 and 2 is used for manufacturing a tire. The mold 22 includes a large number of tread segments 6, a pair of upper and lower side plates 28, and a pair of upper and lower bead rings 30. The mold 22 is configured by combining a large number of tread segments 6, a pair of side plates 28, and a pair of bead rings 30. This mold 22 is a so-called “split mold”.

  The mold 22 includes a main body 32 and a vent piece 34. The main body 32 includes a hole 36. The hole 36 passes through the main body 32. The vent piece 34 is columnar. In the mold 22, the vent piece 34 is passed through the hole 36 of the main body 32. Thereby, the mold 22 is configured. The cavity surface 24 of the mold 22 is constituted by an inner surface 38 of the main body 32 and an end surface 40 of the vent piece 34.

  In the mold 22 shown in FIG. 2, a single vent piece 34 is shown. In the mold 22, the number of vent pieces 34 is not limited to one. The mold 22 can be provided with a large number of vent pieces 34. In this case, the number of holes 36 equal to the number of the vent pieces 34 is provided in the main body 32 of the mold 22.

  In the mold 22 shown in FIG. 2, a hole 36 is provided in the segment 26 of the main body 32. In the mold 22, the vent piece 34 is not limited to the segment 26. The vent piece 34 may be provided in the portion of the side plate 28, or the vent piece 34 may be provided in the portion of the bead ring 30. The number, position, and the like of the vent pieces 34 provided in the mold 22 are appropriately determined according to the specifications of the tire manufactured by the mold 22.

  In FIG. 3, the vent piece 34 is shown. FIG. 3A is a plan view of the vent piece 34. FIG. 3A shows one end face 42 (hereinafter referred to as a first end face) of the vent piece 34. In FIG. 3A, the direction perpendicular to the paper surface is the length direction of the vent piece 34. FIG. 3B is a front view of the vent piece 34. In FIG. 3 (b), the vertical direction is the length direction of the vent piece 34. In FIG. 3, an alternate long and short dash line CL is a center line of the vent piece 34.

  In the mold 22, the contour of the cross section of the vent piece 34 has a substantially circular shape. The vent piece 34 is a round bar. The vent piece 34 may be configured such that its cross-sectional outline has an elliptical shape. The vent piece 34 may be configured such that its cross-sectional outline has a rectangular shape, or may have a triangular shape. The vent piece 34 may be configured such that the outline of its cross section has a polygonal shape.

  In the mold 22, the vent piece 34 includes a first grip portion 44, a second grip portion 46, and an intermediate portion 48. In the vent piece 34, an intermediate portion 48 is located between the first grip portion 44 and the second grip portion 46 in the length direction. In this mold 22, the center line of the first grip 44 matches the center line CL of the vent piece 34. The center line of the second grip 46 coincides with the center line CL of the vent piece 34. The center line of the intermediate part 48 coincides with the center line CL of the vent piece 34.

  The first grip 44 includes a first end surface 42 of the vent piece 34. The first grip 44 includes a side surface 50 extending from the first end surface 42 in the length direction of the vent piece 34. A groove 52 (hereinafter referred to as a first groove) is carved on the side surface 50. As shown in FIG. 3, the first groove 52 extends in the length direction of the vent piece 34. The first grip 44 includes a first end surface 42 and a first groove 52 extending from the first end surface 42 in the length direction of the vent piece 34.

  FIG. 4 shows the state of the first groove 52 in the first end face 42. As is apparent from FIG. 4, the first groove 52 is a depression. In the mold 22, the contour of the first groove 52 has a shape protruding inward from the side surface 50. In particular, the outline of the first groove 52 is an arc. In the mold 22, the first groove 52 only needs to be recessed from the side surface 50, and the contour of the first groove 52 is not particularly limited. From the viewpoint of easy maintenance, the contour of the first groove 52 is preferably an arc.

  The second grip 46 includes the other end surface 54 of the vent piece 34 (hereinafter referred to as a second end surface). The second gripping portion 46 includes a side surface 56 that extends from the second end surface 54 in the length direction of the vent piece 34. A groove 58 (hereinafter referred to as a second groove) is carved on the side surface 56. As shown in FIG. 3, the second groove 58 extends in the length direction of the vent piece 34. The second grip 46 includes a second end surface 54 and a second groove 58 extending from the second end surface 54 in the length direction of the vent piece 34. Although not shown, the second groove 58 is a depression like the first groove 52. The outline of the second groove 58 is an arc like the outline of the first groove 52. In the mold 22, the second groove 58 only needs to be recessed from the side surface 56, and the contour of the second groove 58 is not particularly limited. From the viewpoint of easy maintenance, the contour of the second groove 58 is preferably an arc.

  In the mold 22, the second gripping portion 46 has a thickness equivalent to the thickness of the first gripping portion 44. In the mold 22, the vent piece 34 may be configured so that the second grip 46 is thinner than the first grip 44. The vent piece 34 may be configured such that the second grip 46 is thicker than the first grip 44. From the viewpoint of easy processing, it is preferable that the second gripping portion 46 has a thickness equivalent to the thickness of the first gripping portion 44.

  As described above, the intermediate portion 48 is located between the first grip portion 44 and the second grip portion 46. As apparent from FIG. 3B, in this mold 22, the intermediate portion 48 is thinner than the first grip portion 44 and the second grip portion 46.

  In the mold 22, a portion 60 between the first gripping portion 44 and the intermediate portion 48 is tapered. In the mold 22, this tapered portion 60 is referred to as a first transition portion. In the mold 22, a portion 62 between the second gripping portion 46 and the intermediate portion 48 is also tapered. In the mold 22, this tapered portion 62 is referred to as a second transition portion. In the mold 22, the vent piece 34 includes a first transition portion 60 and a second transition portion 62 in addition to the first grip portion 44, the second grip portion 46, and the intermediate portion 48. In particular, the vent piece 34 includes a first grip portion 44, a second grip portion 46 and an intermediate portion 48, and a first transition portion 60 and a second transition portion 62.

  In the mold 22, the main body 32 and the vent piece 34 are combined through the vent piece 34 through the hole 36 of the main body 32. As shown in FIG. 5, when the vent piece 34 is passed from the outside of the main body 32 through the hole 36 of the main body 32, the first grip 44 of the vent piece 34 faces the main body 32. The vent piece 34 is passed through the hole 36. Although not shown, when the vent piece 34 is passed through the hole 36 of the main body 32 from the inside of the main body 32, the vent piece 34 is arranged with the second grip 46 of the vent piece 34 facing the main body 32. Is passed through hole 36.

  FIG. 6 shows a part of the cavity surface 24 of the mold 22. FIG. 7 shows a cross section of the mold 22 taken along the line VII-VII in FIG. In FIG. 7, the right side of the paper surface is the cavity surface 24 side of the mold 22.

  In the mold 22, the contour of the side surface 50 of the first grip 44 matches the contour of the hole 36. Since the vent piece 34 is passed through the hole 36, some clearance is taken into consideration, but the size (diameter) of the first grip 44 is substantially equal to the size (diameter) of the hole 36. The side surface 50 of the first grip 44 is in contact with the hole 36. As described above, the first grip 44 includes the first groove 52 that extends from the first end surface 42 in the length direction of the vent piece 34. For this reason, as shown in FIGS. 6 and 7, a space corresponding to the first groove 52 is formed between the first grip 44 and the hole 36.

  In the mold 22, the contour of the side surface 56 of the second grip 46 matches the contour of the hole 36. Since the vent piece 34 is passed through the hole 36, some clearance is taken into consideration, but the size (diameter) of the second grip 46 is substantially the same as the size (diameter) of the hole 36. The side surface 56 of the second grip 46 is in contact with the hole 36. As described above, the second grip 46 includes the second groove 58 extending from the second end surface 54 in the length direction of the vent piece 34. Therefore, as shown in FIG. 7, a space corresponding to the second groove 58 is formed between the second gripping portion 46 and the hole 36.

  As described above, in the mold 22, the intermediate portion 48 is located between the first grip portion 44 and the second grip portion 46 and is thinner than the first grip portion 44 and the second grip portion 46. Since the intermediate portion 48 does not contact the hole 36, a space is formed between the intermediate portion 48 and the hole 36. This space is considerably larger than the space formed between the first grip 44 and the hole 36. The space formed between the intermediate portion 48 and the hole 36 is considerably larger than the space formed between the second gripping portion 46 and the hole 36.

  As described above, in the mold 22, the first transition portion 60 is tapered. The first transition part 60 is thicker than the intermediate part 48 but thinner than the first grip part 44. Since the first transition portion 60 does not contact the hole 36, a space is formed between the first transition portion 60 and the hole 36. This space is larger than the space formed between the first grip 44 and the hole 36. This space communicates with the space corresponding to the first groove 52, and also communicates with the space corresponding to the intermediate portion 48.

  As described above, in this mold 22, the second transition portion 62 is tapered. The second transition part 62 is thicker than the intermediate part 48 but thinner than the second gripping part 46. Since the second transition portion 62 does not contact the hole 36, a space is formed between the second transition portion 62 and the hole 36. This space is larger than the space formed between the second gripping portion 46 and the hole 36. This space communicates with the space corresponding to the second groove 58 and also communicates with the space corresponding to the intermediate portion 48.

  In the mold 22, the first gripping portion 44, the first transition portion 60, the intermediate portion 48, the second transition portion 62, and the second gripping portion 46 are arranged in this order from the first end face 42 side of the vent piece 34. The pieces 34 are arranged in the length direction. In other words, the vent piece 34 is arranged in the length direction of the vent piece 34 from the side of the first end face 42, and the first grip portion 44, the first transition portion 60, the intermediate portion 48, the second transition portion 62, and the like. A second grip 46 is provided.

  As described above, the first end surface 42 of the vent piece 34 is a part of the cavity surface 24. The first groove 52 of the first grip 44 extends from the first end surface 42 of the vent piece 34 in the length direction of the vent piece 34. The second groove 58 of the second grip 46 extends from the second end face 54 of the vent piece 34 in the length direction of the vent piece 34. The first transition part 60, the intermediate part 48 and the second transition part 62 are thinner than the first grip part 44 and the second grip part 46. For this reason, in the vent piece 34, the first groove 52 and the second groove 58 are substantially in communication. In other words, the vent piece 34 includes a groove 64 extending from the first end surface 42 forming a part of the cavity surface 24 in the length direction of the vent piece 34.

  In the mold 22, a space corresponding to the groove 64 of the vent piece 34, that is, a vent hole 66 is formed. The vent hole 66 extends from the cavity surface 24 in the length direction of the vent piece 34. The groove 64 of the vent piece 34 bridges the first end surface 42 and the second end surface 54. In the mold 22, the vent hole 66 penetrates the mold 22. In the mold 22, the air existing between the raw cover R and the cavity surface 24 and the air remaining in the raw cover R are sufficiently discharged to the outside of the mold 22 through the vent hole 66. In this mold 22, air hardly remains in the cavity. According to this mold 22, generation | occurrence | production of a bear is prevented. Since air hardly remains, the mold 22 can also suppress the influence of the remaining air on the durability of the tire.

  As shown in FIG. 6, a gap 68 is formed between the first groove 52 and the hole 36 in the cavity surface 24 of the mold 22. This gap 68 is the mouth of the vent hole 66. In the mold 22, the air in the cavity flows into the vent hole 66 through the gap 68. In the mold 22, the size of the gap 68 is quite small. For this reason, the rubber of the raw cover R is unlikely to flow into the vent hole 66.

  In this mold 22, rubber does not easily flow into the vent hole 66, and the vent hole 66 effectively contributes to the discharge of air. In the mold 22, air is sufficiently discharged while suppressing spew formation. The appearance of the tire manufactured with this mold 22 is of high quality. According to the present invention, it is possible to obtain a tire mold 22 that can sufficiently discharge air while suppressing spew formation. This mold 22 contributes to the manufacture of high-quality tires.

  In the mold 22, in the direction along the periphery of the vent piece 34, that is, in the circumferential direction of the vent hole 20, the position of the first groove 52 provided in the first holding part 44 and the second provided in the second holding part 46. The position of the groove 58 coincides. For this reason, the flow of air passing through the vent hole 66 is smooth. In the mold 22, the air existing between the raw cover R and the cavity surface 24 and the air remaining in the raw cover R are sufficiently discharged through the vent hole 66. In this mold 22, air hardly remains in the cavity. From this viewpoint, in the mold 22, the position of the first groove 52 provided in the first grip portion 44 and the position of the second groove 58 provided in the second grip portion 46 are the same in the circumferential direction of the vent piece 34. It is preferable to do it.

  As described above, in the mold 22, the first transition portion 60, the intermediate portion 48, and the second transition portion 62 are thinner than the first grip portion 44 and the second grip portion 46. In other words, in the mold 22, the vent piece 34 is constricted at a substantially central portion in the length direction. The constriction of the vent piece 34 contributes to the volume of the vent hole. The vent hole 66 penetrates the mold 22 and has a large volume. In the mold 22, air is sufficiently discharged through the vent hole 66. In this mold 22, air hardly remains in the cavity. Moreover, even if rubber flows into the vent hole 66 and the rubber adheres to the vent piece 34, the vent piece 34 has a constriction, so that the attached rubber can be easily removed. Maintenance of the mold 22 is easy. From this point of view, in this mold 22, the portion between the first gripping portion 44 and the second gripping portion 46, specifically, the first transition portion 60, the intermediate portion 48, and the second transition portion 62 are each The vent piece 34 is preferably configured so as to be thinner than the one grip portion 44 and the second grip portion 46.

  In FIG. 3, the double arrow DG <b> 1 is the outer diameter of the first grip 44. The outer diameter DG1 is the thickness of the first grip 44. The outer diameter DG1 is specified based on the contour of the first grip 44 obtained on the assumption that the first groove 52 is not present. A double-pointed arrow DG2 is the outer diameter of the second gripping portion 46. The outer diameter DG2 is the thickness of the second grip 46. The outer diameter DG2 is specified based on the contour of the second gripping portion 46 obtained on the assumption that the second groove 58 is not present. A double arrow DC is an outer diameter of the intermediate portion 48. The outer diameter DC is the thickness of the intermediate portion 48.

  In the mold 22, the thickness DC of the intermediate portion 48 is preferably ½ or more and 2/3 or less of the thickness DG1 of the first gripping portion 44. In other words, the ratio of the thickness DC of the intermediate portion 48 to the thickness DG1 of the first gripping portion 44 is preferably 1/2 or more, and preferably 2/3 or less. In this mold 22, the strength of the vent piece 34 is appropriately maintained by setting this ratio to ½ or more. The vent piece 34 is not easily broken. Moreover, since the volume of the space corresponding to the constriction of the vent piece 34 is appropriately maintained, the inflow of rubber into the vent hole 66 is effectively suppressed. In this mold 22, by setting this ratio to 2/3 or less, the intermediate portion 48 of the vent piece 34 effectively contributes to securing the volume of the vent hole 66. In the mold 22, air is sufficiently discharged. In the mold 22, the thickness DG <b> 2 of the second grip portion 46 is equal to the thickness DG <b> 1 of the first grip portion 44. Therefore, in the mold 22, the thickness DC of the intermediate portion 48 is preferably 1/2 or more and 2/3 or less of the thickness DG2 of the second gripping portion 46.

  In FIG. 3, the double arrow LA is the length of the vent piece 34. A double arrow LG1 is the length of the first grip 44. A double arrow LT1 is the length of the first transition part 60. A double arrow LC indicates the length of the intermediate portion 48. The double arrow LT2 is the length of the second transition part 62. A double arrow LG <b> 2 is the length of the second grip 46. In this mold 22, the length LA of the vent piece 34 includes the length LG 1 of the first grip 44, the length LT 1 of the first transition portion 60, the length LC of the intermediate portion 48, and the length of the second transition portion 62. It is equal to the sum of LT2 and the length LG2 of the second gripping portion 46. In this mold 22, the ratio of the length LT1 of the first transition portion 60 to the length LA of the vent piece 34 is preferably 0 (zero) or more, and preferably 1/12 or less. That this ratio is 0 represents that the first transition part 60 is not provided in the vent piece 34. The ratio of the length LT2 of the second transition portion 62 to the length LA of the vent piece 34 is preferably 0 or more, and preferably 1/12 or less. That this ratio is 0 represents that the second transition part 62 is not provided in the vent piece 34.

  In the mold 22, the length LC of the intermediate portion 48 is preferably 1/3 or more and 1/2 or less of the length LA of the vent piece 34. In other words, the ratio of the length LC of the intermediate portion 48 to the length LA of the vent piece 34 is preferably 1/3 or more, and more preferably 1/2 or less. In the mold 22, the ratio is set to 1/3 or more, so that the intermediate portion 48 of the vent piece 34 effectively contributes to securing the volume of the vent hole 66. In the mold 22, air is sufficiently discharged. In this mold 22, the strength of the vent piece 34 is appropriately maintained by setting this ratio to ½ or less. The vent piece 34 is not easily broken. Moreover, since the volume of the space corresponding to the constriction of the vent piece 34 is appropriately maintained, the inflow of rubber into the vent hole 66 is effectively suppressed.

  In this mold 22, the ratio of the length LG1 of the first grip 44 to the length LA of the vent piece 34 is preferably 1/12 or more, and preferably 1/4 or less. By setting this ratio to 1/12 or more, the strength of the vent piece 34 is appropriately maintained. The vent piece 34 is not easily broken. Moreover, since the space corresponding to the first groove acts as a resistance against the inflow of rubber, the inflow of rubber into the vent hole 66 is effectively suppressed. By setting this ratio to ¼ or less, the first grip 44 effectively contributes to securing the volume of the vent hole 66. In the mold 22, air is sufficiently discharged.

  In FIG. 4, the symbol PG is the bottom of the first groove 52. The two-dot chain line SL is a virtual side surface of the first grip 44 obtained on the assumption that there is no first groove 52. A double-headed arrow D1 is a distance from the virtual side surface to the bottom PG. In the present invention, this distance D 1 is the depth of the first groove 52. A double-headed arrow W1 is the width of the first groove 52. The width W1 is represented by the distance from one edge of the first groove 52 to the other edge. Although not shown, the width W2 of the second groove 58 and the depth D2 of the second groove 58 are defined for the second groove 58 of the second gripping portion 46 in the same manner as the first groove 52 described above. Is done.

  In this mold 22, the width W1 of the first groove 52 is preferably 0.2 mm or more from the viewpoint that the first groove 52 contributing to air discharge is obtained. The width W1 is preferably 0.4 mm or less from the viewpoint that the strength of the first grip 44 is appropriately maintained and the first groove 52 in which rubber does not easily flow is obtained.

  In the mold 22, the width W <b> 2 of the second groove 58 is preferably 0.2 mm or more from the viewpoint that air discharge is promoted. The width W2 is preferably equal to or less than 0.4 mm from the viewpoint that the strength of the second grip 46 is appropriately maintained and the inflow of rubber is suppressed.

  In this mold 22, the depth D1 of the first groove 52 is preferably 0.02 mm or more from the viewpoint that the first groove 52 contributing to air discharge is obtained. The depth D1 is preferably 0.04 mm or less from the viewpoint that the strength of the first gripping portion 44 is appropriately maintained and the first groove 52 in which rubber does not easily flow is obtained.

  In the mold 22, the depth D2 of the second groove 58 is preferably 0.02 mm or more from the viewpoint that air discharge is promoted. The depth D2 is preferably 0.04 mm or less from the viewpoint that the strength of the second gripping portion 46 is appropriately maintained and the inflow of rubber is suppressed.

  In the mold 22, the first grip 44 has one or more first grooves 52. In the mold 22, when the first grip portion 44 includes a plurality of first grooves 52, the first grooves 52 are spaced along the periphery of the first grip portion 44. Be placed. From the viewpoint of smooth discharge of air, in the first grip portion 44, the plurality of first grooves 52 are preferably arranged at equal intervals along the periphery of the first grip portion 44. From the viewpoint that the vent hole 66 effectively contributes to the discharge of air, the number of the first grooves 52 provided in the first grip 44 is preferably 6 or more. The number of the first grooves 52 is preferably 8 or less from the viewpoint that the vent hole 66 is excellent in durability and hardly inflow of rubber.

  In the mold 22, the second gripping portion 46 includes one or more second grooves 58. In the mold 22, when the second gripping portion 46 includes a plurality of second grooves 58, the second grooves 58 are spaced along the periphery of the second gripping portion 46. Be placed. From the viewpoint of smooth discharge of air, in the second grip portion 46, the plurality of second grooves 58 are preferably arranged at equal intervals along the periphery of the second grip portion 46. From the viewpoint that the vent hole 66 effectively contributes to the discharge of air, the number of the second grooves 58 provided in the second grip portion 46 is preferably six or more. The number of the second grooves 58 is preferably eight or less from the viewpoint that the vent hole 66 is formed which has excellent durability and is difficult for rubber to flow into.

  Half of the product of the width W1 of the first groove 52 and its depth D1, that is, W1 × D1 / 2 gives the apparent sectional area of one first groove 52. In the mold 22, since one or more first grooves 52 are provided in the first grip 44, when the number of the first grooves 52 provided in the first grip 44 is n (n is a natural number) The apparent sectional area of the entire first groove 52 provided in the first grip 44 is represented by n × W1 × D1 / 2. This is a measure of the size of the space between the first grip 44 and the hole 36 (or the mouth of the vent hole 66). In the present invention, the apparent sectional area of the entire first groove 52 represented by n × W1 × D1 / 2 is referred to as the apparent sectional area of the first groove 52.

  In the mold 22, the ratio of the apparent sectional area of the first groove 52 to the sectional area of the hole 36 is preferably 0.5% or less. In the mold 22, the size of the first groove 52 is appropriately maintained. In the mold 22, the rubber of the raw cover R hardly flows into the vent hole 66. In this mold 22, spew formation is suppressed.

  In this mold 22, the ratio of the apparent sectional area of the first groove 52 to the sectional area of the hole 36 is preferably 0.2% or more. In the mold 22, the first groove 52 effectively contributes to air discharge. According to this mold 22, a tire having a good appearance and durability can be obtained.

  In the mold 22, the number of the second grooves 58 provided in the second gripping portion 46 is set to m (m is a natural number) in the same manner as the first groove 52 with respect to the second groove 58 of the second gripping portion 46. ) Using the width W2 of the second groove 58 and the depth D2 of the second groove 58, the apparent cross-sectional area of the second groove 58 is represented by m × W2 × D2 / 2.

  In this mold 22, the ratio of the apparent sectional area of the second groove 58 to the sectional area of the hole 36 is 0.5% or less from the viewpoint of preventing the inflow of rubber into the vent hole 66 and suppressing the formation of spew. preferable. From the viewpoint that air discharge through the vent hole 66 is promoted and a tire having a good appearance and durability can be obtained, this ratio is preferably 0.2% or more.

  In the mold 22, the material of the main body 32 and the vent piece 34 is metal. Examples of the metal include steel, aluminum alloy, stainless steel, and titanium alloy.

  In the mold 22, it is preferable that a metal having a thermal expansion coefficient larger than that of the metal constituting the main body 32 is selected for the vent piece 34. As a result, in the mold 22, the vent piece 34 expands more than the main body 32 during the heating. The vent piece 34 that has greatly expanded is difficult to move with respect to the main body 32. In the mold 22, the vent piece 34 can be stably held by the main body 32. When the mold 22 is cooled, the vent piece 34 contracts more than the main body 32. The contraction of the vent piece 34 contributes to the removal of the vent piece 34 from the main body 32. In the mold 22, the vent piece 34 can be easily replaced. From this viewpoint, a combination of a vent piece 34 made of an aluminum alloy and a main body 32 made of stainless steel is preferable.

  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 FIG. 1-2 was prepared. A vent piece having the configuration shown in FIG. 3 was used for this mold. This is represented as “FIG. 3” in the column of the configuration in Table 1.

  In Example 1, the number of grooves, that is, the number of first grooves and the number of second grooves was set to six. The width of the groove, that is, the width W1 of the first groove and the width W2 of the second groove were set to 0.3 mm. The depth of the groove, that is, the depth D1 of the first groove and the depth D2 of the second groove were set to 0.03 mm.

  In Example 1, the thickness DC of the middle part of the vent piece was set to 2.0 mm. The length LC of this intermediate part was set to 4.0 mm. In Example 1, the vent piece length LA was 12 mm. The length LT1 of the first transition part was 1.0 mm. The length LT2 of the second transition part was 1.0 mm. The length LG2 of the second grip portion was 4.0 mm. The thickness of the vent piece, that is, the thickness DG1 of the first gripping part and the thickness DG2 of the second gripping part were 3.0 mm.

[Comparative Example 1]
Comparative Example 1 is a conventional mold. In Comparative Example 1, a conventional cylindrical vent piece was used. This is represented as “C” in the configuration column of Table 1.

  In Comparative Example 1, the outer diameter of the vent piece was 3.0 mm. The inner diameter of this vent piece was 0.2 mm. There is no groove on the side of the vent piece. This vent piece is not provided with an intermediate portion.

[Comparative Example 2]
Comparative Example 2 is a conventional mold. In Comparative Example 2, a spring vent was used as the vent piece. This is represented as “S” in the configuration column of Table 1.

[Comparative Example 3]
Comparative Example 3 is a conventional mold. In Comparative Example 3, the vent piece shown in FIG. 8 was used. This is represented as “FIG. 8” in the column of the configuration in Table 1.

[Example 2-4]
A mold of Example 2-4 was prepared in the same manner as in Example 1 except that the number of grooves, that is, the number of first grooves and the number of second grooves was as shown in Table 2 below.

[Example 5]
A mold of Example 5 was prepared in the same manner as Example 1 except that the length LC of the intermediate part was as shown in Table 2 below.

[Example 6-7]
A mold of Example 6-7 was prepared in the same manner as Example 1 except that the thickness DC of the intermediate part was as shown in Table 3 below.

[Example 8-10]
The width of the groove, that is, the width W1 of the first groove and the width W2 of the second groove, and the depth of the groove, that is, the depth D1 of the first groove and the depth D2 of the second groove are shown in Table 3 below. A mold of Example 8-10 was prepared in the same manner as Example 1 except that it was as shown.

[Evaluation of mold]
One thousand tires (size = 205 / 45R17) were manufactured using the prototype mold. Checked spew, bear, and vent piece damage. Regarding spew, “N” indicates that spew has not been confirmed, “Y” indicates occurrence of spew that needs to be cut in a later process, and cut is not necessary but is minute. The case where the occurrence of spew is confirmed is indicated by “S”. For bears and damage, the occurrence is indicated by an index. It is preferable that the numerical value is closer to “0 (zero)”.

  As shown in Table 1-3, 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 technology relating to the vent piece described above can also be applied to molds for various types of tires.

2, 34 ... Vent piece 4 ... Head 6 ... Body 8 ... Vent line 10 ... Saw cut 22 ... Mold 24 ... Cavity surface 26 ... Tread segment 28 ..Side plate 30 ... Bead ring 32 ... Main body 36 ... Hole 42 ... One end face of vent piece 34 (first end face)
44 ... first gripping portion 46 ... second gripping portion 48 ... intermediate portion 52 ... groove (first groove)
54 ... The other end surface (second end surface) of the vent piece 34
58 ... groove (second groove)
66 ... Vent hole

Claims (8)

A mold having a cavity surface that forms the outer surface of a tire,
This mold includes a main body and a columnar vent piece,
The main body has a hole penetrating the main body, and the vent piece is passed through the hole,
The vent piece includes an end surface and a groove extending from the end surface in the length direction of the vent piece,
A tire mold, wherein the end surface is a part of the cavity surface.   The tire mold according to claim 1, wherein a width of the groove is 0.2 mm or more and 0.4 mm or less, and a depth of the groove is 0.02 mm or more and 0.04 mm or less.   The tire mold according to claim 1 or 2, wherein the vent piece includes 6 or more and 8 or less grooves, and the grooves are arranged around the vent piece with a space therebetween. The vent piece includes a first gripping portion, an intermediate portion, and a second gripping portion, which are arranged in the length direction of the vent piece from the end face side,
The tire mold according to any one of claims 1 to 3, wherein the intermediate portion is thinner than the first grip portion and the second grip portion.   The tire mold according to claim 4, wherein the thickness of the intermediate portion is not less than ½ and not more than 2/3 of the thickness of the first gripping portion.   The tire mold according to claim 4 or 5, wherein a length of the intermediate portion is 1/3 or more and 1/2 or less of a length of the vent piece.   The tire mold according to any one of claims 1 to 6, wherein a ratio of the apparent sectional area of the groove to a sectional area of the hole is 0.5% or less. Preparing the raw cover;
A step of introducing the raw cover into a mold having a cavity surface that forms the outer surface of the tire;
And pressurizing and heating the raw cover in the mold,
The mold includes a main body and a columnar vent piece,
The main body has a hole penetrating the main body, and the vent piece is passed through the hole,
The vent piece includes an end surface and a groove extending from the end surface in the length direction of the vent piece,
A method for manufacturing a tire, wherein the end surface is a part of the cavity surface.

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