JP6309325B2 - Mold and pneumatic tire manufacturing method - Google Patents

Description

  The present invention relates to a mold and a method for manufacturing a pneumatic tire, and more particularly, a mold having a vent hole for exhausting air accumulated between a molding material such as an unvulcanized tire and the mold. And a method of manufacturing a pneumatic tire using the mold.

  A mold used for molding a rubber product or the like is provided with a vent hole for exhausting air inside the mold. For example, a tire vulcanization mold is formed with a large number of thin exhaust holes called vent holes in order to exhaust air existing between an unvulcanized tire and a mold. In these vent holes, a rubber material flows in during vulcanization molding to form hook-like projections called spews, so that a separate removal step is required. Therefore, in order to suppress the inflow of the rubber material while enabling exhaust from the vent hole, it has been proposed to incorporate a valve member that opens and closes the vent hole opening (that is, the exhaust port) into the vent hole (for example, Patent Documents 1 and 2).

  In a vent hole equipped with such a valve member, a molding material such as rubber enters between the exhaust port and the valve member, causing malfunction of the valve member. It is required to do. Therefore, for example, in Patent Document 1, it is proposed that the valve member is disposed so that the front end surface (upper end surface) of the valve member recedes from the inner surface of the mold when the valve member is closed. Further, in Patent Document 2, a recess is provided on the inner surface of the mold, a vent hole exhaust port is provided on the bottom surface of the recess, and a valve body (valve member) for opening and closing the exhaust port is provided in the recess. It is disclosed that the molding material is prevented from wrapping around the back surface side of the valve body by providing the valve body at a position retracted from the inner surface of the mold.

  In the configurations disclosed in these Patent Documents 1 and 2, since the tip end surface of the valve member is retracted from the inner surface of the mold and the concave portion is formed in the closed state, the convex portion is formed on the tire surface after vulcanization molding. This will adversely affect the noise performance and rolling resistance performance of the tire.

International Publication No. 2006/070411 JP 2004-291615 A

  The present invention has been made in view of the above points, and an object of the present invention is to prevent a molding material from entering between an exhaust port of a vent hole and a valve member.

A mold according to the present invention includes a vent hole provided with an exhaust port that opens on the inner surface of the mold, and a valve member that opens and closes the exhaust port, and is a valve member that is pressed by a molding material from an open state to be closed. a tire vulcanizing mold which Ru with a recess for the land portion formed provided in the tread molding surface, said vent hole is provided at a corner portion of the recess, the valve member around the exhaust port An encircling peripheral wall is provided, and the peripheral wall protrudes from the inner surface of the mold and is formed higher than the tip position of the valve member in the open state, and is axially directed to the peripheral wall for the vent hole provided in the corner portion The ventilation slit is provided at a position where the slit is opened toward the top of the corner .

  The method for producing a pneumatic tire according to the present invention includes setting an unvulcanized tire in the mold and unvulcanizing the air accumulated between the unvulcanized tire and the mold through the vent hole. The tire is vulcanized.

  According to the present invention, by providing the peripheral wall, the intrusion of the molding material from the side of the valve member is blocked, and the intrusion of the molding material between the exhaust port and the valve member can be prevented. In addition, since the peripheral wall is provided so as to protrude from the inner surface of the mold, a convex portion due to the peripheral wall is not formed on the molded product. Therefore, for example, when used for tire vulcanization molding, noise performance and rolling resistance performance are reduced. The adverse effect of can be suppressed.

It is sectional drawing of the metal mold | die for tire vulcanization | cure which concerns on one Embodiment. It is sectional drawing which shows the exhaust structure of the metal mold | die. It is a principal part expanded sectional view in the valve member open state of the same exhaust structure. It is a principal part expanded sectional view in the valve member closed state of the same exhaust structure. It is a principal part expanded sectional view which shows the exhaust structure in the curved-surface-shaped metal mold | die inner surface position. It is a perspective view which shows the surrounding wall of the same exhaust structure. It is a top view of the recessed part for land part formation of the metal mold | die. It is sectional drawing which shows the exhaust structure of the metal mold | die which concerns on other embodiment. It is sectional drawing which shows the exhaust structure of the metal mold | die which concerns on other embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view of a tire vulcanization mold 10 according to an embodiment. The mold 10 includes an annular tread mold portion 12 for forming a tire tread portion, and a pair of upper and lower side mold portions 14 and 14 for forming a sidewall portion of the tire. The cavity 11 which is a molding space of the pneumatic tire is formed together with the above. A tread molding surface 13 which is an inner peripheral surface of the tread mold portion 12 is provided with a vertical rib 16 and a horizontal rib 18 for forming a vertical groove and a horizontal groove of the tread portion, and is defined by the vertical rib 16 and the horizontal rib 18. The formed area is a land portion forming recess 20 for forming a land portion such as a block in the tread portion.

  The inner surface 22 of the mold including the tread molding surface 13 is provided with a vent hole 24 for venting air that communicates with the outside of the mold 10. A plurality of vent holes 24 are provided not only on the inner peripheral surface of the tread mold part 12 but also on the side wall molding surface 15 of the side mold part 14.

  As shown in FIG. 2, the exhaust structure of the embodiment includes a vent hole 24 having an exhaust port 26 that opens to the inner surface 22 of the mold, and a valve member 28 that opens and closes the exhaust port 26. The exhaust port 26 is an opening for discharging the air in the cavity 11, and corresponds to an inlet for introducing air into the vent hole 24.

  The valve member 28 is urged toward the inside of the mold 10 (upward in FIG. 2) to open the exhaust port 26, and the rubber material of the unvulcanized tire during tire vulcanization molding As a result, the front end surface 29 (that is, the upper end surface) is pressed toward the outside of the mold 10 (downward in FIG. 2) against the urging force, thereby closing the exhaust port 26. In this example, the tip surface 29 is a tip position of the valve member 28 in the open state, and is a pressed surface that is pressed by the molding material in the closed state.

  In this example, the exhaust structure includes an insertion hole 30 provided at an end of the vent hole 24 on the mold inner surface 22 side, and a plug 32 mounted in the insertion hole 30. The insertion hole 30 is a cylindrical surface-shaped hole that opens in the mold inner surface 22 provided in the mold 10. The plug 32 includes a cylindrical holder 34 that is fitted in the insertion hole 30, a valve member 28 that is slidably attached in the holder 34, and a coil spring 36 that is an elastic member housed in the holder 34. Prepare.

  The holder 34 has a cylindrical shape, and the hollow portion 38 forms a part of the vent hole 24, and the opening end portion of the hollow portion 38 toward the cavity 11 is the exhaust port 26. An inverted tapered valve seat 40 whose opening area gradually increases toward the cavity 11 side is provided at the opening end. Further, a locking portion 42 that protrudes inward is provided at the end opposite to the exhaust port 26 side, and an exhaust path is secured inside thereof.

  The valve member 28 has a structure in which a head portion 44 and a locking projection 46 are provided at both ends of a shaft member (stem). The head portion 44 is provided with a reverse taper 48 that gradually increases in diameter toward the tip so that the head portion 44 can be fitted into the reverse tapered valve seat 40 of the holder 34 and close the exhaust port 26, and the tip surface 29 facing the cavity 11. Is formed in a planar shape. The locking projection 46 is a convex portion that prevents the valve member 28 penetrating through the inside of the locking portion 42 of the holder 34. The valve member 28 is attached to the holder 34 such that the coil spring 36 is sandwiched between the head portion 44 and the locking portion 42 while being inserted inside the coil spring 36. 28 is mounted via a coil spring 36 so as to be capable of reciprocating in the axial direction. The valve member 28 is biased toward the cavity 11 side by the elastic force of the coil spring 36 until the locking projection 46 is locked to the locking portion 42 of the holder 34, as shown in FIG. In a normal state, a gap 50 is formed between the taper 48 of the head portion 44 and the valve seat 40 of the holder 34.

  In the exhaust structure as described above, according to the present embodiment, as shown in FIGS. 2 and 3, a peripheral wall 52 surrounding the valve member 28 is provided around the exhaust port 26. The peripheral wall 52 is a thin plate-like wall portion that forms a cylindrical shape surrounding the head portion 44 of the valve member 28, and rubber from the side toward the gap 50 formed between the exhaust port 26 and the valve member 28. Block material ingress. In order to effectively prevent the intrusion of the rubber material from the side into the gap 50 while enabling the exhaust from the exhaust port 26, the peripheral wall 52 allows the head portion 44 of the valve member 28 to be provided with a gap 54 for ventilation. Enclose. The peripheral wall 52 is formed so as to protrude into the cavity 11 from the inner surface 22 of the mold, and the upper end 52A thereof is higher than the front end surface (that is, the front end position) 29 of the valve member 28 in the open state (that is, the mold). The distance from the inner surface 22 is large). In this example, the peripheral wall 52 is integrally provided at the end of the holder 34 on the exhaust port 26 side.

  The protruding height of the peripheral wall 52 is not particularly limited, but the height H from the distal end surface 29 of the valve member 28 is preferably 0.1 to 0.5 mm, and more preferably, the height H is 0.1 mm. 3 to 0.5 mm. Further, the thickness T of the peripheral wall 52 is not particularly limited, but is preferably 0.1 to 0.3 mm. If set in such a range, the peripheral wall 52 is formed by a fine circular cut formed on the tire surface. Insufficient rigidity of the peripheral wall 52 can be avoided while reducing the influence on tire performance and appearance.

  As shown in FIG. 4, the tip surface 29 of the valve member 28 in the closed state (that is, the pressed surface by the unvulcanized tire 100) 29 is set flush with the mold inner surface 22. That is, in a state where the head portion 44 of the valve member 28 closes the exhaust port 26, the front end surface 29 which is the upper surface of the head portion 44 is located on the same plane as the mold inner surface 22 around it. The tip surface 29 being flush with the mold inner surface 22 means that when the vent hole 24 is provided in the planar mold inner surface 22, it is located on the same plane as described above. It is as follows in the position which shape | molds the curved tire surface like a shoulder part. That is, as shown in FIG. 5, when the vent hole 24 is provided in the curved mold inner surface 22, the virtual surface 22A of the mold inner surface 22 within the range where the exhaust port 26 is formed is considered, and the highest of the virtual surface 22A is considered. When the tip surface 29 is located between the point 56 and the lowest point 58, the tip surface 29 is said to be flush with the mold inner surface 22. Such aspect is also included in the “level” in the present invention.

  As shown in FIGS. 3 and 6, the peripheral wall 52 is provided with a ventilation notch 60 extending in the axial direction. By providing the notch 60, the exhaust performance at the vent hole 24 can be improved and the bear caused by residual air can be reduced while the peripheral wall 52 is provided. In this example, the cuts 60 are provided at one place in the circumferential direction of the peripheral wall 52, but may be provided at two or more places. Further, the height of the notch 60 is preferably provided in the entire height of the peripheral wall 52 from the viewpoint of exhaustability by the vent hole 24, but may be provided only on the upper side of the peripheral wall 52. The width W of the notch 60 is not particularly limited, but is preferably 0.1 mm or less, for example 0.05 to 0.1 mm, in order to suppress the intrusion of the rubber material.

  The formation position of the cut 60 in the circumferential direction of the peripheral wall 52 is not particularly limited. For example, when the vent hole 24 is provided in the land portion forming recess 20, the vent hole 24 is provided in each corner 62 of the recess 20 as shown in FIG. 7. When the cut 60 is provided in the peripheral wall 52 for the vent hole 24 provided in the corner portion 62, the cut 60 is preferably provided at a position that opens toward the top portion 62A of each corner portion 62. In this case, since the rubber material is filled from the center of the recess 20 toward each corner 62 during vulcanization molding, exhaust using the cut 60 is possible until the final stage of filling while preventing the rubber material from entering. It becomes.

  When manufacturing a pneumatic tire using the mold 10 having the above-described configuration, an unvulcanized tire (green tire) is set in the mold 10 and the mold is closed, and then a bladder (not shown) disposed inside is used. The unvulcanized tire is vulcanized and molded by pressing the unvulcanized tire against the inner surface 22 of the mold and keeping it heated.

  At this time, in this embodiment, the unvulcanized tire is vulcanized while exhausting air accumulated between the unvulcanized tire and the mold 10 through the vent hole 24. Specifically, when the unvulcanized tire is pressed against the inner surface 22 of the mold, the valve member 28 is in an open position with respect to the exhaust port 26 as shown in FIG. The air in the cavity 11 flows into the vent hole 24 through the gap 50 with the air 40 and is exhausted to the outside of the mold 10. Thereafter, when the unvulcanized tire reaches the inner surface 22 of the mold, as shown in FIG. 4, the unvulcanized tire 100 presses the front end surface 29 of the valve member 28, so that the valve member 28 is pushed into the gap. 50 is eliminated and the exhaust port 26 is closed, so that the rubber material is prevented from entering the vent hole 24.

  At this time, in the present embodiment, the vent hole 24 is provided with the peripheral wall 52 surrounding the valve member 28, so that the intrusion of the rubber material from the side of the valve member 28 is blocked. That is, the inflow direction is limited so that the rubber material flows only into the valve member 28 from above the tip surface 29, and the permeation from the side along the mold inner surface 22 is blocked by the peripheral wall 52. Therefore, intrusion of the molding material between the exhaust port 26 and the valve member 28 can be prevented, and malfunction of the valve member 28 due to intrusion can be reduced.

  In the present embodiment, since the peripheral wall 52 is provided so as to protrude from the inner surface 22 of the mold, a minute circular cut by the peripheral wall 52 is formed on the tire surface, but a convex portion is formed on the peripheral wall 52. Therefore, deterioration of noise performance and rolling resistance performance due to the convex portions formed on the tire surface can be suppressed.

  Further, in the present embodiment, since the front end surface 29 of the valve member 28 in the closed state is set flush with the inner surface 22 of the mold, no convex portion is formed on the tire surface by the vent hole 24, and noise performance is achieved. Further, deterioration of rolling resistance performance can be further suppressed. In this embodiment, the front end surface 29 of the valve member 28 in the closed state is flush with the inner surface 22 of the mold, but the front end surface 29 may be set at a position protruding from the inner surface 22 of the mold. Even at the protruding position, no convex portion is formed on the tire surface, so that an effect of suppressing deterioration of noise performance and rolling resistance performance can be obtained.

  In the above embodiment, the peripheral wall 52 is integrally provided at the end of the holder 34, but the peripheral wall 52 may be configured as a separate part from the holder 34.

  FIG. 8 shows an example thereof, and an outer cylinder member 64 that is externally fitted to the holder 34 is provided, and the peripheral wall 52 is configured by the end of the outer cylinder member 64. Specifically, one end surface of the holder 34 forming the exhaust port 26 is disposed flush with the mold inner surface 22. The outer cylinder member 64 has a cylindrical shape that is fitted on the upper end of the holder 34, and is clamped and fixed between the wall surface of the insertion hole 30 of the mold 10 and the holder 34. One end of the outer cylinder member 64 protrudes from the mold inner surface 22 into the cavity 11, and a peripheral wall 52 surrounding the valve member 29 is formed by the protruding end portion.

  By configuring the peripheral wall 52 as a separate part from the holder 34 as described above, a general-purpose product can be used without producing a dedicated product, compared to the case where the peripheral wall 52 is provided on the holder 34 itself. Further, when the peripheral wall 52 is configured by the outer cylindrical member 64 in this way, a C-shaped cylindrical body in which a slit extending in the axial direction is provided at one place in the circumferential direction is used as the outer cylindrical member 64. Thus, the slit 60 can be easily provided in the peripheral wall 52. With the outer cylinder member 64 having a C-shaped cross section, after the outer cylinder member 64 is inserted into the insertion hole 30 of the mold 10, the holder 34 is caulked into the inside thereof, thereby forming the vent hole 24 having the peripheral wall 52. Since it can form, the clearance gap around a holder main body can be filled up and a protrusion can be reduced.

  The peripheral wall 52 may also be formed on the mold 10 itself. For example, in the example shown in FIG. 9, the peripheral wall 52 protrudes integrally from the inner surface 22 of the mold at the opening peripheral edge of the insertion hole 30. When the peripheral wall 52 is provided on the holder 34 or the outer cylinder member 64 as in the above embodiment, when the peripheral wall 52 is mounted in the insertion hole 30 of the mold 10, the circumferential position of the notch 60 is accurately positioned and attached. It is not always easy, and the installation man-hour is large. On the other hand, when the peripheral wall 52 is formed on the mold 10 itself, the peripheral wall 52 having the notch 60 at a predetermined position in the circumferential direction may be formed when the mold 10 is manufactured. Can be reduced, so the number of mounting steps can be reduced.

  In the above embodiment, the valve member 28 is configured to reciprocate in the axial direction via the coil spring 36. However, the configuration of the valve member is not limited to this, and the exhaust port can be opened and closed. If it is, you may comprise by the disk-shaped valve body which can be elastically deformed.

  The mold is not limited to tire vulcanization, and may be a mold for various molded products such as a vibration-proof rubber member, and the molding material is not limited to the rubber material. Or a synthetic resin.

  The above embodiment is presented as an example and is not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 10 ... Mold, 11 ... Cavity, 20 ... Land part formation recessed part, 22 ... Mold inner surface, 24 ... Vent hole, 26 ... Exhaust port, 28 ... Valve member, 29 ... Tip surface, 52 ... Perimeter wall, 60 ... Notch 62 ... Corner, 62A ... Top, 100 ... Unvulcanized tire

Claims (5)

A vent hole provided with an exhaust port opening to the inner surface of the mold, the tire vulcanizing gold Ru and a valve member in the closed state is pressed by the molding material from a valve member for opening and closing the exhaust port opened Type ,
A concave portion for land formation is provided on the tread molding surface, and the vent hole is provided at a corner of the concave portion,
A peripheral wall surrounding the valve member is provided around the exhaust port, and the peripheral wall protrudes from the inner surface of the mold and is formed higher than a tip position of the valve member in the open state .
A vent cut extending in the axial direction is provided in the peripheral wall for the vent hole provided in the corner, and the cut is provided at a position opening toward the top side of the corner. Mold.   The mold according to claim 1, wherein a pressed surface of the valve member by the molding material in the closed state is flush with the inner surface of the mold or at a position protruding from the inner surface of the mold. The mold according to claim 1 or 2 , wherein the thickness of the peripheral wall is 0.1 to 0.3 mm. The vent hole includes an insertion hole provided at an end of the vent hole on the mold inner surface side, a cylindrical holder that has a hollow portion that forms the exhaust port, and is fitted into the insertion hole, An outer cylinder member that fits around the holder,
The peripheral wall is formed by the end of the outer cylinder member, and the outer cylinder member is a C-shaped cylinder having a slit extending in the axial direction at one place in the circumferential direction, and the slit for ventilation is formed by the slit. Formed,
The metal mold | die of any one of Claims 1-3. An unvulcanized tire is set in the mold according to any one of claims 1 to 4, and unvulcanized while exhausting air accumulated between the unvulcanized tire and the mold through the vent hole. A method for producing a pneumatic tire, comprising vulcanizing a tire.

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