JP2020108934A - Tire mold and tire manufacturing method - Google Patents

Abstract

To improve an efficiency of a cutting process of cutting a tip of a bead part including a squeeze-out part of a groove line and to suppress an occurrence of defects due to the cutting process.SOLUTION: In a tire mold of the present invention, in a meridional section including a tire rotation axis of a bead ring 20, a bead heel molding surface appears as a bead heel contour line 11, a bead toe molding surface appears as a bead toe contour line 12, and a bladder contact surface appears as a bladder contour line 13. The bead toe contour line 12 includes a first curved part 14, a second curved part 15 and a third curved part 16 in order from a side closer to the bead heel. The first curved part 14 is connected to the bead heel contour line 11. The second curved part 15 is located inside the first curved part 14 in a tire radial direction. The third curved part 16 is connected to the bladder contour line 13 and is located further inside than the second curved part 15 in the tire radial direction.SELECTED DRAWING: Figure 2

Description

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

For vulcanization molding of pneumatic tires, set an unvulcanized tire in a tire mold, inflate a rubber bag called a bladder, press the unvulcanized tire from the tire inner surface toward the tire mold, and keep it at a high temperature. It is done by

Patent Document 1 discloses a bead ring which is one of the constituent members of a tire mold. The bead ring includes an upper bead ring and a lower bead ring which are arranged apart from each other in the vertical direction and contact a pair of bead portions of the tire from the outside in the tire width direction. It is disclosed to mold the bead portion of the.

Patent Document 2 discloses that the bead portion is a region fitted to the rim, and therefore the tip shape of the bead portion is precisely defined.

The shape of the conventional bead ring will be described with reference to FIG. In FIG. 3, a part of the bead ring 50, a bead part 30 in contact with the bead ring 50, a part of the bladder 6 inflated on the inner surface side of the tire, and a part of the lower side plate 8 include a tire rotation shaft. Shown in meridian section. The bead portion 30 includes a bead toe 31, a bead heel 32, and a bead core 33. The shapes of the bead toe 31 and the bead heel 32 are defined by the shape of the bead ring 50.

The bead ring 50 includes a bead heel molding surface and a bead toe molding surface that are in contact with the bead portion 30, and a bladder contact surface that is in contact with the bladder 6 that presses the tire from the inner surface side. In the meridional section including the tire rotation axis, the bead heel molding surface appears as the bead heel contour line 51, the bead toe molding surface appears as the bead toe contour line 52, and the bladder contact surface appears as the bladder contour line 53. The bead heel contour 51 is connected to the bead toe contour 52, and the bead toe contour 52 is connected to the bladder contour 53.

The bead toe contour line 52 has two curved portions including a curved portion 54 connected to the bead heel contour line 51 and a curved portion 55 connected to the bladder contour line 53.

By the way, the surface of the bladder 6 is provided with a groove called a bladder groove for allowing air remaining between the unvulcanized tire and the bladder 6 to escape to the outside. During the vulcanization molding, after the air is discharged to the outside through the groove 61, the rubber on the tire inner surface 34 enters the groove 61. As a result, linear ridges called groove lines are formed on the tire inner surface 34 after vulcanization molding.

FIG. 4A is a perspective view including a cross section (a meridional cross section including the tire rotation axis) of the bead portion 30 in the tire after vulcanization molding and the tire inner surface 34. In this figure, a bead core 33, a bead toe 31 and a bead heel 32 are shown in the cross section of the bead portion 30. A large number of groove lines 35 are formed on the tire inner surface 34. The groove line 35 reaches the tip of the bead toe 31. Although this figure shows a tire cross section for convenience of description, the tire as a product is, of course, an annular body having no cross section.

FIG. 4B shows a view seen from the direction A in FIG. 4A, that is, from the tire outer surface side. When viewed from the outer surface side of the tire, the groove line 35 reaching the tip of the bead toe 31 appears to protrude. The groove line 35 protruding from the tire outer surface side is referred to as a protruding portion 35a. The protruding portion 35a impairs the appearance of the tire.

Therefore, after the vulcanization molding, the operator cuts the protruding portion 35a together with the tip of the bead toe. For example, the cutting tool and the tire are relatively moved along the cutting line C1 shown in FIG. 4 to cut the bead toe tip side from the cutting line C1. Thereby, the protruding portion 35a of the groove line 35 is removed to improve the appearance.

However, the cutting line C1 is close to the tip of the bead toe 31, and cuts a thin rubber region in the tire width direction. Since the thin rubber region has low rigidity, the rubber easily bends and escapes from the cutting edge of the cutting tool. Then, the cutting edge may deviate from the cutting line C1 and the protruding portion 35a may be insufficiently cut, which complicates the cutting of the protruding portion 35a. On the other hand, if an attempt is made to cut the rubber so as not to bend it, and more is cut than desired, a defect will occur outside the specified dimensional range.

As described above, cutting the bead toe 31 while keeping the tip thereof within the prescribed size range has high technical difficulty and is an inefficient work that requires a lot of work time. Furthermore, there is a concern that defects may occur due to such a cutting process.

JP, 2008-089827, A Japanese Unexamined Patent Publication No. 9-020110

In order to solve the above problems, it is an object of the present invention to improve the efficiency of the cutting process for cutting the bead toe tip including the protruding portion of the groove line and to suppress the occurrence of defects due to the cutting process.

The tire mold of the present invention has the following features. That is, it is provided with an upper bead ring and a lower bead ring that are spaced apart in the vertical direction, the upper bead ring and the lower bead ring, respectively, a bead heel molding surface and a bead toe molding surface that are in contact with the bead portion of the tire. , A bladder contact surface for contacting a bladder that presses the tire from the inner surface side, and at least one of the upper bead ring and the lower bead ring, in a meridional section including a tire rotation axis, the bead heel molding surface is As a bead heel contour line, the bead toe molding surface appears as a bead toe contour line, and the bladder contact surface appears as a bladder contour line, respectively, and the bead toe contour line has a first curved portion and a second curved portion in order from the side closer to the bead heel. And a third curved portion, the first curved portion is connected to the bead heel contour line, the second curved portion is located on the inner side in the tire radial direction with respect to the first curved portion, and the third curved portion is It is connected to the contour line of the bladder and is located inward of the second curved portion in the tire radial direction.

According to the present invention having the above configuration, since the thickness of the rubber is secured at the cut portion of the bead toe tip including the protruding portion of the groove line, the technical difficulty of the cutting step is reduced, the work efficiency is improved, and the occurrence of defects occurs. Can be suppressed.

Further, in the tire mold, an angle formed between a first straight line portion connecting the second curved line portion and the third curved line portion and a straight line parallel to the tire rotation axis is 30 degrees or more and 60 degrees or less. May be provided.

Furthermore, in the tire mold, the curvature radius of the third curved portion may be smaller than the curvature radius of the second curved portion.

Furthermore, in the tire mold, the bead toe contour line includes one or more additional curved line portions between the second curved line portion and the third curved line portion, and the additional curved line portion corresponds to the bladder contour line. A configuration may be provided in which the closer the curved portion is, the inner portion is located in the tire radial direction.

The tire manufacturing method of the present invention arranges an unvulcanized tire on the inner surface side of the tire mold, presses the unvulcanized tire to the tire mold by the bladder to perform vulcanization molding, and after vulcanization molding A configuration is provided in which a protruding portion of a groove line formed on the tire inward in the tire radial direction is cut together with a tip of a bead toe of a bead portion.

Meridian half cross-sectional view showing an example of a tire mold according to the present invention (A) An enlarged view of part B in FIG. 1, (b) An enlarged view of part D in FIG. 2(a) A meridional sectional view showing a main part of a conventional tire mold (A) A perspective view showing the bead portion of the tire, (b) a view taken along arrow A of FIG. 4(a)

An example of a tire mold used during vulcanization molding will be described with reference to FIG. In FIG. 1, a meridional half cross-sectional view of the tire mold 1 is shown together with the bladder 6 and the tire 3. The tire mold 1 includes a tread ring 2 for molding a tread portion of a tire 3, an upper side plate 7 and a lower side plate 8 for molding a sidewall portion of the tire 3, and an upper bead ring for molding a bead portion of the tire 3. 9 and the lower bead ring 10. The upper bead ring 9 and the lower bead ring 10 are located inside the upper side plate 7 and the lower side plate 8 in the tire width direction, respectively, and are vertically spaced apart from each other. In FIG. 1, an unvulcanized tire 3 is arranged on the inner surface side of a tire mold 1, a bladder 6 arranged on the inner surface side of the tire 3 is inflated, and the tire 3 is pressed from the inner surface side to be vulcanized and molded. The situation is shown. The tread ring 2 is divided into a plurality of sectors along the tire radial direction.

FIG. 2A is an enlarged view of part B in FIG. 1. The shape of the lower bead ring 10 will be described with reference to FIG. In FIG. 2A, a part of the lower bead ring 10, a bead portion 20, a part of the bladder 6 inflated on the inner surface side of the tire, and a part of the lower side plate 8 include a tire rotation shaft. Shown in meridian section. The bead portion 20 includes a bead toe 21, a bead heel 22, and a bead core 23. The shapes of the bead toe 21 and the bead heel 22 are defined by the shape of the lower bead ring 10.

The lower bead ring 10 includes a bead heel molding surface and a bead toe molding surface that are in contact with the bead portion 20, and a bladder contact surface that is in contact with the bladder 6 that presses the tire 3 from the inner surface side. In the meridional section including the tire rotation axis, the bead heel molding surface appears as the bead heel contour line 11, the bead toe molding surface appears as the bead toe contour line 12, and the bladder contact surface appears as the bladder contour line 13. The bead heel contour line 11 is connected to the bead toe contour line 12, and the bead toe contour line 12 is connected to the bladder contour line 13.

FIG. 2B is an enlarged view of the portion D in FIG. In FIG. 2B, for convenience of explanation, oblique lines showing a cross section are omitted. In the present embodiment, the bead heel contour line 11 is formed by a line segment including an arc centered on the cavity side (the tire width direction inner side of the contour line). The bladder contour line 13 extends along the tire radial direction.

The bead toe contour line 12 has three curved portions. The curved portion represents a continuous arc on the contour line. In the present embodiment, each of the three curved portions is an arc having a unique curvature center and a curvature radius inside the tire radial direction with respect to the contour line. A first curved portion 14, a second curved portion 15, and a third curved portion 16 are provided in order from the side closer to the bead heel.

The first curved portion 14 is connected to the bead heel contour line 11 on one end side and is connected to the second curved portion 15 on the other end side. The radius of curvature RA of the first curved portion 14 is larger than the radius of curvature RB of the second curved portion 15 and the radius of curvature RC of the third curved portion 16.
The second curved portion 15 is located on the bead toe contour line 12 between the first curved portion 14 and the third curved portion 16, and is located further inside than the first curved portion 14 in the tire radial direction. The second curved line portion 15 is connected to the third curved line portion 16 via the first straight line portion 17. The 1st linear part 17 inclines toward the tire width direction inner side toward the tire radial direction inner side.
The third curved portion 16 is located at the other end of the bead toe contour line 12 and is connected to the bladder contour line 13. The second curved portion 15 is located inside the first curved portion 14 in the tire radial direction, and the third curved portion 16 is located inside the second curved portion 15 in the tire radial direction.

As a result, a space surrounded by the second curved portion 15, the third curved portion 16 and the bladder 6 is formed at the tip of the bead toe, which is not required in the originally required bead toe. When the rubber enters the space, a hem-shaped rubber portion that projects inward in the tire radial direction and continuously extends in the tire circumferential direction is formed at the tip of the bead toe.

The bead portion 20 after vulcanization molding has a protruding portion in which the groove line 25 reaching the tip of the bead toe 21 appears to protrude from the outside of the tire. Therefore, the protruding portion is cut together with the hem-shaped rubber portion. In the cutting step, the hem-shaped rubber is cut along the tire circumferential direction. The cut portion of the hem-shaped rubber is shown as a cutting line C2 in FIG. 2B, for example.

The cutting line C2 is an extension line of the first curved portion 14 extended from the other end side connected to the second curved portion 15 and forms an angle θ1 with a straight line parallel to the tire rotation axis. The angle θ1 is preferably 10 degrees or more and less than 30 degrees, more preferably 15 degrees or more and less than 20 degrees. Since the cutting line C2 is longer than the conventional cutting line C1, it is possible to secure a sufficient thickness of rubber at the cutting site. If the rubber at the cut portion is thick, the rigidity is high, so that the rubber bends from the cutting edge of the cutting tool and is hard to escape, and it is easy to cut into a desired shape. As a result, it is possible to reduce the technical difficulty of excision, shorten the work time, and improve the work efficiency. Furthermore, it is possible to suppress the occurrence of tire defects due to the cutting process.

The cutting line C2 shown above and shown in FIG. 2 is an example of a cutting site, and is not limited to this. The cut portion may be set to be longer than the cut line C1, the protruding portion of the bladder line is difficult to see from the tire outer surface side, and the tip of the bead toe after the cut can be kept within a specified size range. ..

The position and shape of the curved portion may be set so that the angle θ2 formed between the first straight line portion 17 and the straight line parallel to the tire rotation axis is 30 degrees or more and 60 degrees or less, and more preferably 45 degrees. It is good to set it to ±5 degrees. If the angle θ2 is too small, when the bladder 6 is inserted while inflated, the bladder 6 may be caught by the third curved portion 16 and rub against it to damage the bladder 6, which is not preferable. If the angle θ2 is too large, it is difficult to secure the thickness of the rubber at the cut portion.

As another embodiment, the bead toe contour 12 may include one or more additional curved portions between the second curved portion 15 and the third curved portion 16. Here, since the tip of the bead toe 21 has a shape in which the thickness in the tire width direction gradually decreases as it approaches the tip, the additional curved portion is located closer to the inside in the tire radial direction as the curved portion is closer to the bladder contour line 13. It is preferable to provide the additional curved portion in order to reduce the bending of the third curved portion and suppress damage to the bladder 6 while ensuring the thickness of the rubber at the cut portion.

When the radius of curvature RC of the third curved portion 16 is smaller than the radius of curvature RB of the second curved portion 15, it is easy to secure the thickness of the rubber at the cut portion.

In the above description, the lower bead ring 10 is taken up and described, but a contour shape similar to this can also be applied to the upper bead ring 9. The upper bead ring 9 may have the same shape as the lower bead ring 10 or may have a different shape.

The above-described embodiment shows a tread ring composed of a plurality of sectors, and a segmented type tire mold including a pair of upper and lower side plates contacting the tire width direction end portion of the tread ring. May be a so-called two-piece mold in which a pair of upper and lower back metals are incorporated inside in the tire radial direction.

The present invention is not limited to the above-described embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1... Tire mold 2... Tread ring 6... Bladder 7... Upper side plate 8... Lower side plate 9... Upper bead ring 10, 100... Lower bead ring 11, 51... Bead heel contour line 12, 52... Bead toe contour line 13 , 53... Bladder outline 14... First curved portion 15... Second curved portion 16... Third curved portion 17... First straight portion 20... Bead portion 21... Bead toe 22, 32... Bead heel 23, 33... Bead core 24, 34 ... tire inner surfaces 25, 35 ... groove line 35a ... protruding portion 61 ... groove

Claims (5)

Equipped with an upper bead ring and a lower bead ring that are arranged separately in the vertical direction,
The upper bead ring and the lower bead ring respectively include a bead heel molding surface and a bead toe molding surface that are in contact with a bead portion of a tire, and a bladder contact surface that is in contact with a bladder that presses the tire from the inner surface side,
In at least one of the upper bead ring and the lower bead ring, in a meridional section including a tire rotation axis, the bead heel molding surface is a bead heel contour line, the bead toe molding surface is a bead toe contour line, and the bladder contact surface is a bladder. Each appears as a contour line,
The bead toe contour line includes a first curved line portion, a second curved line portion, and a third curved line portion in order from the side closer to the bead heel,
The first curved portion is connected to the bead heel contour line,
The second curved portion is located on the inner side in the tire radial direction with respect to the first curved portion,
The tire mold, wherein the third curved portion is connected to the bladder contour line and is located on the inner side in the tire radial direction with respect to the second curved portion. The angle formed between the first straight line portion connecting the second curved line portion and the third curved line portion and a straight line parallel to the tire rotation axis is 30 degrees or more and 60 degrees or less. Tire mold. The bead toe contour line includes one or more additional curve portions between the second curve portion and the third curve portion, and the additional curve portion is closer to the bladder contour line, the tire is closer to the tire. The tire mold according to claim 1, which is located on the inner side in the radial direction. The tire mold according to any one of claims 1 to 3, wherein a radius of curvature of the third curved portion is smaller than a radius of curvature of the second curved portion. An unvulcanized tire is arranged on the tire mold according to any one of claims 1 to 4, and the unvulcanized tire is pressed against the tire mold by the bladder to perform vulcanization molding,
A method for manufacturing a tire, wherein a groove wire formed on a tire after vulcanization molding is cut out at a protruding portion inward in the tire radial direction together with a bead toe tip of the bead portion.

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