JP2020131535A - Mold for tire vulcanization molding - Google Patents

Abstract

To prevent spews from being formed on a bead portion of a tire.SOLUTION: A mold for tire vulcanization molding is provided with a bead ring 5 having a bead molding surface 14 for molding a tire bead portion. The bead ring 5 is provided with a spring vent 25 capable of communicating between the bead molding surface 14 and the outside of the bead ring 5.SELECTED DRAWING: Figure 2

Description

The present invention relates to a tire vulcanization molding die.

Conventionally, a tire vulcanization molding die having a bead ring for forming a bead portion of a tire and having a vent hole formed in the bead ring is known (see, for example, Patent Document 1).

However, in the tire obtained by molding with the conventional mold, a whiskers-like rubber called a spew is formed on the bead portion. The spew formed on the bead portion hinders the rim assembly and is preferably removed, but it is difficult to remove the spew formed on the bead portion.

JP-A-2017-209858

An object of the present invention is to provide a tire vulcanization molding die capable of preventing a spew from being formed on a bead portion of a tire.

The present invention includes a bead ring having a bead forming surface for forming a bead portion of a tire as a means for solving the above-mentioned problem, and the bead ring can communicate between the bead forming surface and the outside of the bead ring. Provided is a tire vulcanization molding die provided with a spring vent.

With this configuration, gas can be discharged from the bead portion via the spring vent during vulcanization molding. Since it is a spring vent, a spew is not formed on the outer surface of the bead portion.

The opening position of the spring vent on the bead forming surface is preferably the deepest portion of the recess forming the bead forming surface.

With this configuration, gas can be positively discharged from the portion where gas is most likely to remain.

The recess forming the bead forming surface has a cross-sectional shape having a radius of curvature R, and the spring vent is ± 10 ° with respect to the reference line extending in the radial direction through the deepest portion with respect to the deepest portion. It preferably extends over an angular range.

With this configuration, it is possible to prevent the exhaust performance from fluctuating between the spring vents and obtain a desired air exhaust effect.

It is preferable that the bead ring is composed of a plurality of bead rings divided in the tire circumferential direction, and the spring vents formed in each bead ring have different inclination angles with respect to the reference line.

With this configuration, it is possible to intervene a spring vent that is less likely to cause rubber clogging due to the difference in the inclination angle with respect to the reference angle. Therefore, it is possible to prevent the occurrence of a problem that all the spring vents are clogged at the same time.

According to the present invention, since the spring vent that can communicate with the bead forming surface forming the bead portion is provided, it is possible to prevent the spew from being formed on the bead portion.

FIG. 3 is a cross-sectional view of a tire vulcanization molding die according to an embodiment of the present invention. FIG. 1 is a partially enlarged cross-sectional view of the bead ring shown in FIG. FIG. 2 is a partially enlarged view of the bead forming surface as viewed from the arrow X in FIG. FIG. 3 is a cross-sectional view taken along the line AA of FIG. A partially enlarged cross-sectional view of the bead ring according to another embodiment. A partially enlarged cross-sectional view of the bead ring according to another embodiment. Partial enlarged view of the bead molding surface of the bead ring according to another embodiment. Partial enlarged view of the bead molding surface of the bead ring according to another embodiment. Partial enlarged view of the bead molding surface of the bead ring according to another embodiment. Partial enlarged view of the bead molding surface of the bead ring according to another embodiment.

Hereinafter, embodiments according to the present invention will be described with reference to the accompanying drawings. It should be noted that the following description is essentially merely an example, and is not intended to limit the present invention, its application, or its use. Furthermore, the drawings are schematic, and the ratio of each dimension is different from the actual one.

FIG. 1 is a cross-sectional view showing an outline of a tire vulcanization molding die (hereinafter, simply referred to as “mold 1”) according to an embodiment of the present invention. In FIG. 1, only one side of the mold 1 in the tire radial direction is shown together with the vulcanized and molded pneumatic tire 2.

The mold 1 includes a sector mold 3, a side plate 4, and a bead ring 5 which are arranged in an annular shape about an axial center extending in the vertical direction. The space defined by the sector mold 3, the side plate 4 and the bead ring 5 is a cavity 6 in which a green tire is set and vulcanized, that is, a segmented mold.

The sector mold 3 is composed of a plurality of sectors 7. Each sector 7 moves in the radial direction about the axis of the mold 1 (indicated by RD in FIG. 1). Each sector 7 moves to the inner diameter side and is connected in an annular shape, and the connected inner wall surface becomes a tread forming surface 8 forming the outer surface of the tread portion of the pneumatic tire 2.

The side plate 4 is a pair of upper and lower annular plates located on the inner diameter side of the sector mold 3. The upper plate 9 moves in the axial direction of the mold 1 (indicated by AD in FIG. 1). The upper plate 9 approaches the lower plate 10, and the inner wall surface thereof becomes the sidewall molded surface 11 that forms the outer surface of the sidewall portion of the pneumatic tire 2.

The bead ring 5 is a pair of upper and lower annular rings integrated on the inner diameter side of the side plate 4. The upper ring 12 approaches the lower ring 13 together with the upper plate 9, and a part of the inner wall surface thereof becomes a bead forming surface 14 that forms the outer surface of the bead portion of the pneumatic tire 2.

As shown in FIG. 2, the bead forming surface 14 is formed by the first curved surface 15, the second curved surface 16, the third curved surface 17, the flat surface 18, and the tapered surface 19 from the upper side to the lower side in the axial direction AD. It is configured. The first curved surface 15 has an arcuate cross section with a radius of curvature R1 and has a center of curvature O1 on the bead ring 5 side, and is formed so as to bulge. The second curved surface 16 is a concave portion that is continuous with the first curved surface 15, has an arc shape with a radius of curvature R2, has a center of curvature O2 on the opposite side of the first curved surface 15, and is formed to be recessed. .. The third curved surface 17 has an arc shape with a radius of curvature R3, the center of curvature O3 is on the bead ring side, and is formed so as to bulge. The deepest portion 20 which is the deepest recessed position of the second curved surface 16 is located on the reference line SL which divides the second curved surface 16 into two in line symmetry. Here, the angle θ0 formed by the reference line SL and the straight line ADL extending in the axial direction of the mold 1 is set to 20 ° ≦ θ0 ≦ 65 °.

Groove-shaped saw cuts 21 are formed at a plurality of positions on the bead forming surface 14, as shown in FIG. 3 when FIG. 2 is viewed with a Y arrow. The saw cut 21 includes a circumferential saw cut 22 extending in the tire circumferential direction CR and a radial saw cut 23 extending in the tire radial direction RD. The circumferential saw cut 22 is located at the deepest portion 20.

A plurality of vent holes 24 are formed at the deepest portion 20 of the second curved surface 16 of the bead forming surface 14 at equal intervals in the circumferential direction about the axis (here, 18 places). Some vent holes 24 are located at the intersection of the circumferential saw cut 22 and the radial saw cut 23. The vent hole 24 extends along the reference line SL. Further, as shown in FIG. 7, the vent hole 24 extends from the axial center of the mold 1 toward the radial RD. A spring vent 25 is arranged in each vent hole 24. The vent hole 24 and the axis of the spring vent 25 are aligned with each other.

As shown in FIG. 4, the spring vent 25 includes a cylindrical housing 27 having an exhaust passage 26, a stem 28 inserted into the housing 27, and a coil spring 29 for urging the stem 28 toward the bead forming surface side. Be prepared.

A part of the outer peripheral surface (lower portion in FIG. 4) of the housing 27 is held in the vent hole 24 in a press-fitted state. The exhaust passage 26 is composed of an upper end opening 30, a communication portion 31, a spring accommodating portion 32, and a tapered portion 33 from the upper end to the lower end. The upper end opening 30 has a larger inner diameter than the communication portion 31, and a step portion 34 is formed therein. The spring accommodating portion 32 has a larger inner diameter than the communicating portion 31, and a reduced diameter portion 35 is formed at a boundary portion with the communicating portion 31. The tapered portion 33 is composed of an inner surface of a cone whose inner diameter gradually increases from the spring accommodating portion 32 toward the lower end.

The stem 28 includes a shaft portion 36, a stopper 37 formed at the upper end portion of the shaft portion 36, and a valve body 38 formed at the lower end portion. A large diameter portion 39 having an outer diameter larger than that on the upper side thereof is formed in the lower portion of the shaft portion 36. The valve body 38 is formed in a truncated cone shape whose diameter increases downward. The outer surface of the cone of the valve body 38 extends parallel to the inner surface of the cone of the tapered portion 33 of the housing 27, and both are in surface contact with each other.

The coil spring 29 is arranged around the shaft portion 36 and is housed in the spring accommodating portion 32 of the housing 27. The coil spring 29 is in a compressed state between the reduced diameter portion 35 and the large diameter portion 39. As a result, the stem 28 is urged downward. At this time, the stopper 37 comes into contact with the step portion 34 of the housing 27 and is prevented from coming off. However, a partial gap is formed between the stopper 37 and the step portion 34 in a contact state so that the gas can flow.

In the mold 1 having the above configuration, when the green tire is vulcanized, the gas between the bead portion of the green tire and the bead molding surface 14 of the bead ring 5 is discharged to the outside of the mold via the spring vent 25. Will be done. The spring vent 25 is formed in the deepest portion 20 of the second curved surface 16 which is the most recessed of the bead forming surfaces 14. In the spring vent 25, the stem 28 is pushed down by the urging force of the coil spring 29, and a gap is formed between the valve body 38 and the tapered portion 33. As a result, the gas in the mold 1 enters the spring accommodating portion 32 through this gap, and is discharged to the outside through the gap between the communication portion 31 and the shaft portion 36 through the gap between the stopper 37 and the step portion 34. .. The deepest part 20 is the place where gas loses its place and is most likely to gather. By providing the spring vent 25 at this location, it is possible to prevent burning and voids from being generated due to the residual gas.

When rubber flows on the bead molding surface 14 in the vulcanization molding of the green tire, the rubber pushes the stem 28 upward against the urging force of the coil spring 29. As a result, the outer surface of the cone of the valve body 38 and the inner surface of the cone of the tapered portion 33 of the housing 27 come into surface contact with each other and are closed. Therefore, the rubber does not flow into the housing 27.

A spew is not formed on the bead portion of the pneumatic tire 1 vulcanized in this way. Therefore, if this tire is assembled to the rim, the outer surface of the bead portion can be brought into close contact with the rim, and a good rim assembly state can be obtained.

The present invention is not limited to the configuration described in the above embodiment, and various modifications can be made.

In the above embodiment, the bead forming surface 14 having the shape shown in FIG. 2 has been described, but even if the bead forming surface has another shape, if the vent hole 24 is formed at the deepest portion, which is the deepest position, the same applies. You can get the effect of.

In the above embodiment, the bead ring 5 is formed with a vent hole 24 extending from the deepest portion 20 of the bead forming surface 14 on the reference line SL, but the range of ± 10 ° with respect to the reference line SL, preferably. , ± 5 ° may be tilted. For example, since the direction in which the rubber easily flows differs depending on the material of the bead portion of the green tire, the rubber easily flows so as to easily prevent the rubber from flowing into the spring vent 25 mounted on the vent hole 24. The vent hole 24 may be inclined with respect to the direction.

In FIG. 5, the vent hole 24 has a range of −10 ° with respect to the reference line SL, that is, the angle θ1 formed by the center of the vent hole 24 and the straight line ADL extending in the axial direction of the mold 1 is the reference line SL. It is tilted so as to be smaller than the angle θ0 formed with. As a result, the distance from the opening at the bead forming surface 14 to the outer surface of the bead ring 5 can be shortened. As a result, the residual gas on the bead forming surface 14 is easily discharged.

In FIG. 6, the vent hole 24 has a range of + 10 ° with respect to the reference line SL, that is, the angle θ2 formed by the center of the vent hole 24 and the straight line ADL extending in the axial direction of the mold 1 is the reference line SL. It is tilted so that it is larger than the angle θ0 formed. Within this range, the occurrence of rubber biting at least on the inner diameter side of the tire 1 does not pose a problem.

In this case, the inclination angles of the plurality of vent holes 24 may all be the same, but they may be different from each other. As a result, the conditions under which the rubber flowing toward the spring vent 25 acts on the valve body 38 can be made different in each vent hole 24. As a result, it is possible to prevent problems such as clogging of all spring vents 25 at about the same time.

In the above embodiment, when the bead ring 5 is viewed in a plan view (when viewed from the lower side in FIG. 2), the vent hole 24 is directed in the radial direction from the axial center of the mold 1 as shown in FIG. It was formed, but it may be different. According to this, it is possible to avoid interference between the bead ring 5 by making the inclination angle of the vent hole 24 which is likely to overlap with the mounting (screw) position of the bead ring 5 on the upper plate 9 different. As a result, the opening position of the vent hole 24 on the inner surface of the bead ring 5 can be freely set. As a result, the vent holes 24 can be uniformly opened in the circumferential direction to discharge air evenly.

In FIG. 8, three vent holes 24 adjacent to each other in the circumferential direction of the bead ring 5 are set as a set, and only one of them is a predetermined angle α (-20 ° ≦ α ≦) with respect to a straight line RDL extending in the radial direction of the bead ring 5. It is tilted at 20 °). Therefore, every other bent vent hole 24 is formed in the circumferential direction of the bead ring 5.

In FIG. 9, three vent holes 24 adjacent to each other in the circumferential direction of the bead ring 5 are set as a set, and the inclination directions of the vent holes 24 located on both sides are opposite to each other. That is, the first vent hole 24a inclined to one side in the circumferential direction with respect to the linear RDL extending in the radial direction of the bead ring 5, the second vent hole 24b located on the straight line RDL, and the circumference with respect to the straight line RDL. Third vent holes 24c that incline to the other side in the direction are arranged in order in the circumferential direction. According to this, the inclination angles of the second vent hole 24b and the third vent hole 24c do not necessarily have to be the same.

In FIG. 10, all of the three vent holes 24 are inclined at a predetermined angle α (−20 ° ≦ α ≦ 20 °) with respect to the straight line RDL extending in the tire radial direction.

In the above embodiment, one vent hole 24 is formed from the deepest portion 20 of the bead forming surface 14, but two vent holes 24 having different inclination angles can also be formed. For example, if one vent hole 24 is formed in a direction in which rubber easily flows with respect to the deepest portion 20, and the other vent hole 24 is formed in the other direction, the rubber is clogged in one vent hole 24. Even in this case, one bead ring 5 can be used for a long period of time because the gas can be vented through the other vent hole 24.

In the above-described embodiment, the segmented mold has been described as the mold 1, but the same effect can be obtained by adopting the spring vent 25 on the bead molding surface 14 even in the case of the upper and lower half split two-piece molds. it can.

1 ... Mold 2 ... Pneumatic tire 3 ... Sector mold 4 ... Side plate 5 ... Bead ring 6 ... Cavity 7 ... Sector 8 ... Tread molding surface 9 ... Upper plate 10 ... Lower plate 11 ... Sidewall molding surface 12 ... Upper ring 13 ... Lower ring 14 ... Bead forming surface 15 ... 1st curved surface 16 ... 2nd curved surface 17 ... 3rd curved surface 18 ... Flat surface 19 ... Tapered surface 20 ... Deepest part 21 ... Saw cut 22 ... Circumferential saw cut 23 ... Diameter Direction Saw cut 24 ... Vent hole 25 ... Spring vent 26 ... Exhaust passage 27 ... Housing 28 ... Stem 29 ... Coil spring 30 ... Upper end opening 31 ... Communication part 32 ... Spring accommodating part 33 ... Tapered part 34 ... Step part 35 ... Reduced diameter Part 36 ... Shaft 37 ... Stopper 38 ... Valve 39 ... Large diameter

Claims (4)

Equipped with a bead ring having a bead molding surface for molding the bead portion of the tire,
The bead ring is a tire vulcanization molding die provided with a plurality of spring vents capable of communicating the bead molding surface and the outside of the bead ring. The tire vulcanization molding die according to claim 1, wherein the opening position of the spring vent on the bead molding surface is the deepest portion of the recess constituting the bead molding surface. The recess forming the bead forming surface has a cross-sectional shape with a radius of curvature R.
The tire vulcanization molding die according to claim 2, wherein the spring vent extends in an angle range of ± 10 ° with respect to the reference line extending in the radial direction through the deepest portion with respect to the deepest portion. Type. The spring vents are formed at different positions in the circumferential direction about the axis of the mold.
The tire vulcanization molding die according to claim 3, wherein the plurality of spring vents have different inclination angles with respect to the reference line.

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