JP2012035535A - Studdable tire, its manufacturing method, tire mold and mold pin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a studdable tire which can inhibit the generation of a fissure in a stud embedding hole opened in the studdable tire, while securing the performance of the stud embedding hole to retain the stud, as well as a tire mold to be used for vulcanization treatment of the studdable tire.SOLUTION: When manufacturing the studdable tire with stud embedding holes formed in a tire tread, the tire mold is used which comprises a plurality of sector molds of the following configuration as a tire mold; that is, including a cylindrical part 14a positioned on the inner circumferential surface side of the sector mold and a bulged part 14b positioned inside the radial direction of the cylindrical part 14a. In addition, when viewed in the radial direction of the sector mold, the bulged part 14b assumes such a shape that it is configured of a mold pin which is elliptic in such a way that the diameter (a) is greater than the radius r of the cylindrical part and the major axis is directed in parallel with the width direction of the sector mold.

Description

  The present invention relates to a studded tire in which a stud embedding hole for embedding a stud in a tread of a tire is formed, a manufacturing method thereof, and a tire mold for manufacturing the studded tire.

Conventionally, as a winter tire, a stud tire in which a stud pin made of metal (hereinafter referred to as a stud) is driven into a land portion of a tread is known. One end of the stud protrudes from the tire tread surface, and the other end is buried deeper than the bottom of the groove formed in the tire tread. When a vehicle equipped with such a stud tire travels on a snowy road, the tip of the stud bites into the road surface, increasing the frictional force between the road surface and the tire, thus ensuring steering stability on the snowy road. Can do.
As a method of manufacturing a stud tire, a method of directly embedding a stud in a tire tread at the time of vulcanization of the tire (for example, refer to Patent Document 1) has been proposed, but for stud embedding for embedding a stud in a tire tread. In general, a studded tire having a hole formed therein is manufactured, and a stud is driven into the stud burying hole (see, for example, Patent Documents 2 and 3).

As shown in FIG. 6, the stud 50 has a body 51 having a larger diameter on the tire tread side than a diameter on the opposite side to the tire tread side, and a body 51 provided on the bottom side of the body 51 (opposite to the tire tread side). A flange 52 for preventing slipping having a diameter larger than the diameter of the tire 51 and a tip 53 protruding in the stud axial direction from the tire tread side end of the body 51 are provided.
On the other hand, as a hole for embedding a stud formed in the land portion of the tread 21, a straight hole 60A having no bulge from the tire tread side to the bottom as shown in the lower left of FIG. Such a flask-shaped hole 60B having a flange portion 60b bulging from the body portion 60a at the bottom.
The stud embedding hole 60A is formed using a tire mold having a plurality of sector molds 72A in which straight mold pins 71A are arranged on an arc-shaped inner peripheral surface as shown in FIG. 7A. The The stud embedding hole 60B is formed using a tire mold including a plurality of sector molds 72B on which flask-type mold pins 71B are arranged as shown in FIG. 7B.

JP 2001-38736 A JP 2010-70052 A JP 2010-111130 A

By the way, one of the important performances required for the holes for burying studs is the stud holding performance when the studs are buried.
When the hole for burying the stud is a straight hole 60A, the adhesion between the stud 50 and the hole 60A is lowered, so that the stud holding performance is lowered.
On the other hand, when the hole for burying the stud is a flask-shaped hole 60B, the adhesion between the stud 50 and the hole 60B is improved, but a crack is generated in the hole 60B when the pot is removed after vulcanization. There was a problem that “hole cracking” was likely to occur.

  The present invention has been made in view of conventional problems, and a studded tire capable of suppressing hole cracking while ensuring the retaining performance of a hole for embedding a stud provided in the studded tire, and a method for manufacturing the same, And it aims at providing the tire mold used for the vulcanization process of a studable tire.

As shown in FIG. 8, when pulling out the sector mold 72 from the tire after vulcanization, in the heart of the sector mold 72 are matched and the extension direction N _p withdrawal direction M and the mold pin 71P of the sector mold 72 but at the circumferential end portion side of the sector mold 72, a large angle difference to the extension direction N _q withdrawal direction M and the mold pin 71q pins sector mold 72 has occurred.
When the mold pin 71 is a straight mold pin 71A, even if there is an angle difference, the stress applied to the rubber around the hole 60A when pulled out from the tread 21 is small. However, in the case of the flask-shaped mold pin 71B, as shown in FIG. 6 (b), there is a flange portion 60b that swells more than the body portion 60a at the bottom of the body portion 60a. It is considered that the stress applied to the rubber around the hole 60B by the mold pin 71B is large, and as a result, the hole 60B is likely to be cracked.

  As a result of intensive studies, the inventor has a form in which the flange portion of the mold pin is linear in the tire circumferential direction and a flask shape in the tire width direction, that is, when viewed from the radial inside of the sector mold. If the ellipse is such that the major axis direction is parallel to the width direction of the sector mold and the minor axis direction is parallel to the circumferential direction, cracking of the hole for embedding the stud can be suppressed, and the stud The present inventors have found that the holding performance can be secured and have arrived at the present invention.

  That is, the present invention relates to a tire mold including a pair of side molds for forming a tire side portion and a plurality of sector molds provided with a plurality of protrusions for forming a tread pattern on the inner peripheral surface. The inner circumferential surface of the sector mold has a cylindrical portion located on the inner circumferential surface side of the sector mold and a bulge portion located radially inward of the cylindrical portion. A mold pin for projecting inward and forming a hole for embedding a stud in the land portion of the tire tread is disposed, and the shape of the bulge portion when viewed from the radial direction of the sector mold is such that the major axis a is the cylindrical portion The major axis is an ellipse whose major axis is parallel to the width direction of the sector mold.

Further, the present invention is characterized in that a ratio P = (a / b) of the major axis a to the minor axis b of the ellipse is in a range of 1.4 to 2.9.
Thereby, while being able to suppress a hole crack, the fall of stud holding performance can be prevented reliably.
The present invention is characterized in that the minor axis b of the ellipse is equal to the radius r.
Thereby, since the shape when the mold pin is viewed from the width direction is the same as that of the straight mold pin, it is possible to reliably suppress hole cracking.

Further, in the present invention, a stud embedding hole is formed in a land portion of a tire tread using a tire mold including a plurality of sector molds provided with a plurality of protrusions and mold pins on an inner peripheral surface. A studded tire manufacturing method for manufacturing a studded tire, wherein the sector mold includes a cylindrical portion protruding radially inward from an inner peripheral surface of the sector mold, and a bulge positioned radially inward of the cylindrical portion. And the shape of the bulge portion when viewed from the radial direction of the sector mold is such that the major axis a is larger than the radius r of the cylindrical portion, and the major axis direction is the width direction of the sector mold. A plurality of sector molds having mold pins which are parallel ellipses are used.
As a result, it is possible to manufacture a studded tire that has excellent stud holding performance and is greatly reduced in cracking of holes for burying studs.

Further, the present invention is provided in a tire mold having a pair of side molds and a plurality of sector molds so as to project radially inwardly on the inner peripheral surface of the sector mold, and to the land portion of the tire tread. A mold pin for forming a hole for embedding, wherein the mold pin includes a cylindrical portion located on an inner peripheral surface side of the sector mold, and a bulge portion located on a radially inner side of the cylindrical portion. The shape of the bulging part when viewed from the radial direction of the mold is such that the major axis a is larger than the radius r of the cylindrical part, and the major axis direction is an ellipse parallel to the width direction of the sector mold. Features.
Thereby, it is possible to form a stud embedding hole in the land portion of the tire tread that has excellent stud holding performance and in which hole cracking is significantly reduced.

Further, the present invention is a studded tire in which a stud embedding hole for embedding a stud is formed in a land portion of a tire tread, and the stud embedding hole is located on a tire tread side. A trunk portion and a bulge portion located on the inner side in the tire radial direction of the trunk portion, and the shape of the bulge portion when viewed from the tire radial direction has a major axis a larger than a radius r of the trunk portion, and The major axis direction is an ellipse parallel to the width direction of the sector mold.
Since the studded tire having such a stud embedding hole has few micro cracks remaining in the stud embedding hole, the stud holding performance can be reliably improved.
Further, the present invention is characterized in that a ratio P = (a / b) of the major axis a to the minor axis b of the ellipse is in a range of 1.4 to 2.9.
The present invention is characterized in that the minor axis b of the ellipse is equal to the radius r.
Thus, if the ratio P of the major axis a to the minor axis b of the ellipse and the relationship between the minor axis b and the radius r are set, the stud holding performance can be further improved.

  The summary of the invention does not list all necessary features of the present invention, and a sub-combination of these feature groups can also be an invention.

It is a figure which shows the structure of the mold pin which concerns on this Embodiment. It is principal part sectional drawing which shows the structure of the tire mold which concerns on this Embodiment. It is a figure which shows arrangement | positioning of the sector mold which concerns on this Embodiment. It is a figure which shows an example of the tread pattern of the studable tire vulcanized-molded with the tire mold of this invention. It is a figure which shows the stud hole formed using the mold pin by this invention. It is a figure which shows an example of a stud and a stud hole. It is a figure which shows the formation method of the conventional stud hole. It is a figure for demonstrating the drawing-out state of a mold pin.

  Hereinafter, the present invention will be described in detail through embodiments, but the following embodiments do not limit the invention according to the claims, and all combinations of features described in the embodiments are included. It is not necessarily essential for the solution of the invention.

FIG. 1 is a diagram showing a configuration of a mold pin 14 used in a tire mold according to the present embodiment, FIGS. 2A and 2B are diagrams showing a configuration of a tire mold 10, and FIG. 3 is an arrangement of sector molds 12. FIG. This example demonstrates the case where the stud mold tire which has a block pattern using the tire mold 10 is manufactured. The axial direction of the tire 20 to be vulcanized is hereinafter referred to as the up-down direction.
The tire mold 10 is placed between the upper and lower side molds 11A and 11B and the side molds 11A and 11B to form the side portion 22 of the tire 20 to be vulcanized, and is vulcanized. And a plurality of sector molds 12 for forming the tread 21 of the tire 20.
The sector mold 12 is obtained by dividing an annular mold into a plurality (9 in this example) along the circumferential direction. The sector mold 12 is annular so as to surround the outer side of the tire 20 to be vulcanized. To constitute a tread molding portion of the tire mold 10.
One or both of the upper and lower side molds 11A and 11B can move in the vertical direction, and each sector mold 12 can move in the radial direction indicated by the arrow in FIG.

A plurality of protrusions 13A and 13B and a plurality of mold pins 14 are provided on the inner peripheral surface 12a of each sector mold 12.
The protrusions 13 </ b> A and 13 </ b> B are provided so as to protrude radially inward from the inner peripheral surface 12 a of the sector mold 12, and form a groove in the tread 21. The protrusion 13 </ b> A extending in the circumferential direction forms a circumferential groove 23 as shown in FIG. 4, and the protrusion 13 </ b> B extending in the width direction forms a lug groove 24.
A block 25 which is a land portion of the tread 21 is partitioned by a circumferential groove 23 and a lug groove 24 formed by the protruding portions 13A and 13B. The heights of the protrusions 13A and 13B determine the groove depths of the circumferential groove 23 and the lug groove 24. The region surrounded by the protrusions 13A and 13B indicated by the symbol R in FIG. 2B is hereinafter referred to as a block formation region R.

As shown in FIG. 1, the mold pin 14 includes a cylindrical portion 14a protruding radially inward of the sector mold 12, a bulging portion 14b positioned radially inward of the cylindrical portion 14a, and the inside of the sector mold 12 of the cylindrical portion 14a. A pedestal forming portion 14c located on the peripheral surface 12a side, and a base portion 14d embedded in a pin installation hole 12b (see FIG. 2B) provided in the block forming region R of the inner peripheral surface 12a of the sector mold 12. Have The base forming portion 14c has a diameter that increases toward the inner peripheral surface 12a side of the sector mold 12, and forms a stud introducing portion 26c of a stud hole 26 described later.
In addition, in the sector mold of the type in which the mold pin 14 is not retrofitted, neither the pin installation hole 12b nor the base portion 14d is necessary.
The combined length of the cylindrical portion 14a, the bulging portion 14b, and the base forming portion 14c of the mold pin 14 is set to a value larger than the height of the protruding portions 13A and 13B.
As a result, holes 26 for embedding studs (hereinafter referred to as stud holes) deeper than the groove depths of the circumferential grooves 23 and lug grooves 24 are formed in the blocks 25 that are the land portions of the tread 21 as shown in FIGS. 4 and 5. Can be formed.
In the studded tire, a blade is provided in the block forming region R in addition to the mold pin 14 to form a sipe (not shown) in the block 25, but in this example, these blade and sipe are omitted. is doing.

Specifically, as shown in FIG. 1, the bulging portion 14 b of the mold pin 14 has an elliptical shape when viewed from the radial direction of the sector mold 12. The ellipse has a major axis direction parallel to the width direction of the sector mold 12 and a minor axis direction parallel to the circumferential direction.
In addition, when the major axis of the ellipse is a, the minor axis is b, and the radius of the cylindrical portion 14a is r, the major axis a of the bulged portion 14b of the mold pin 14 according to the present invention is set larger than the radius r of the cylindrical portion. Yes. This is to improve the stud holding performance of the stud hole 26 by making the ellipse major axis a larger than the radius of the cylindrical portion 14a and forming a bulge portion in the stud hole 26.
In this example, the ratio P = (a / b) of the major axis “a” to the minor axis “b” of the ellipse of the bulging portion 14 b is in the range of 1.4 to 2.9, so that the circumferential direction is linear. In addition to suppressing the deterioration of stud retention due to, hole cracking is alleviated. This is because when P <1.4, since the ellipse is close to a circle, the effect of providing the bulging portion 14b is reduced and the stud holding performance is lowered. On the other hand, when P> 2.9, the difference in diameter becomes large, so that the stress acting in the tire width direction of the stud hole 26 at the time of pulling out becomes large, and there is a possibility that a hole crack in the width direction may occur. .
In this example, the minor axis b and the radius r are set equal. Thus, when the mold pin 14 is viewed from the tire width direction, it is the same as the straight mold pin, so that occurrence of hole cracking is avoided even if there is an angle difference between the drawing direction of the sector mold 12 and the extending direction of the mold pin 14. be able to.

Next, the manufacturing method of the studable tire by this invention is demonstrated.
While lowering the upper side mold 11 </ b> A, the sector mold 12 is reduced in diameter and the molds 11 </ b> A, 11 </ b> B, 12 are combined to seal the vulcanized tire 20 in the tire mold 10.
Next, a bladder (not shown) is inflated inside the green tire, and the tire 20 is vulcanized while pressing the tire 20 against the inner surfaces of the molds 11A, 11B, and 12.
The protrusions 13A and 13B and the mold pin 14 provided on each sector mold 12 are pressed against the surface of the tire 20 raised to the vulcanization temperature and inserted into the tread 21.
After the vulcanization treatment, the sector mold 12 is expanded while the upper side mold 11A is raised, and the molds 11A, 11B, 12 are separated from the tire 20, and then the vulcanized tire 20 is tire molded. 4 and FIG. 5, a cylindrical trunk portion 26 a located on the tire tread surface side and a bulge portion 26 b located on the inner side in the tire radial direction of the trunk portion 26 a as shown in FIGS. When viewed from the side (tire radial direction), the shape of the bulging portion 26b is such that the long diameter a is larger than the radius r of the body portion 26a, and the stud hole 26 is an ellipse whose major axis direction is parallel to the tire width direction. The studded tire 20 in which is formed can be obtained. Moreover, since the mold pin 14 of this example has the base formation part 14c whose diameter becomes large as it goes to the inner peripheral surface 12a side of the sector mold 12, the surface of the stud hole 26 (the tire tread surface) side has a surface. It is possible to form a tapered stud introduction portion 26c whose side is larger than the radius r of the body portion 26a and whose radius decreases toward the back. This facilitates introduction of the stud.
In addition, the up-down direction of FIG. 4 is a tire circumferential direction, and the left-right direction is a tire width direction. Moreover, the thin dashed-dotted line shown with the code | symbol CL represents a center line.

  Thus, in the present embodiment, when manufacturing the studded tire 20 in which the stud hole 26 is formed in the tread 21, the cylindrical portion 14a positioned on the inner peripheral surface 12a side of the sector mold 12 is used as a tire mold. A bulging portion 14b positioned radially inward of the cylindrical portion 14a, and the shape of the bulging portion 14b when viewed from the radial direction of the sector mold 12 is such that the major axis a is larger than the radius r of the cylindrical portion and the major axis is Since the tire mold 10 including the plurality of sector molds 12 in which the mold pins 14 whose directions are ellipses parallel to the width direction of the sector mold 12 is used, the cracking of the stud hole 26 is greatly reduced. In addition, the studded tire 20 having the stud hole 26 having excellent stud holding performance can be manufactured.

In the above-described embodiment, a case where a studded tire having a block pattern is manufactured has been described, but the present invention is also applicable to a tire having another tread pattern such as a rib pattern.
Moreover, in the said example, although the short diameter b of the bulging part 14b and the radius r of the cylindrical part 14a were made equal, it is not restricted to this, The short diameter b may be larger than the radius r, and may be small. . However, when the minor axis b is smaller than the radius r, there is a higher possibility of hole cracking than when the minor axis b is equal to the radius r, while the minor axis b is larger than the radius r. In this case, since the stud retaining property of the formed stud hole 26 may be deteriorated, it is preferable that the short diameter b of the bulging portion 14b is substantially equal to the radius r of the cylindrical portion 14a.
The present invention is also applicable when the sector mold 12 is a piece mold in which a plurality of pieces divided into a plurality of pieces in the tire circumferential direction or the tire width direction are held in a holder.

表１に示すように、フラスコ型のモールドピンを配置して製造した比較例２のタイヤでは、全数穴割れが発生しているのに対し、本発明のタイヤでは穴割れの発生が見られなかった。また、スタッド保持性については、比較例２とほぼ同等であり、かつ、ストレート型のモールドピンを配置して製造した比較例１のタイヤに比較して著しく向上していることがわかる。
これにより、本発明のモールドピンを用いることにより、スタッド穴の穴割れを抑制することができるとともに、スタッド保持性能を確保することができることが確認された。 A studded tire (this invention) manufactured using a tire mold provided with a sector mold in which the mold pins (a = 2.0 mm, b = r = 1.0 mm) of the present invention are arranged, and a straight mold pin ( a = b = r = 1.0 mm) and a tire (Comparative Example 1) and a flask type mold pin (a = b = 2.0 mm, r = 1.0 mm). Ten tires (Comparative Example 2) were manufactured, and the results of examining “hole cracking” and “stud retention” are shown in Table 1 below.
The tire size was 195 / 65R15, and 110 stud holes were provided per tire.
In the tire of the present invention, 32 straight stud holes are provided.
Regarding "hole cracking", we investigated the number of failures caused by cracks in the tire stud holes after the vulcanizer was removed.
Further, the “stud retention” was evaluated by the number of studs removed after running a test vehicle equipped with each tire for 30,000 km. In addition, evaluation was made into the index display when the comparative example 1 was set to 100. FIG. The higher the number, the higher the stud retention.

As shown in Table 1, in the tire of Comparative Example 2 manufactured by arranging flask-shaped mold pins, all the holes cracked, whereas in the tire of the present invention, no hole cracking was observed. It was. In addition, it is understood that the stud retention is substantially the same as that of Comparative Example 2 and is significantly improved as compared with the tire of Comparative Example 1 manufactured by arranging straight mold pins.
Thereby, by using the mold pin of this invention, while being able to suppress the hole crack of a stud hole, it was confirmed that stud retention performance can be ensured.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the embodiment. It is apparent from the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  Thus, according to the present invention, it is possible to reliably suppress the cracking of the stud hole and to manufacture a tire excellent in stud holding performance.

10 tire mold, 11A, 11B side mold, 12 sector mold,
12a inner peripheral surface, 13A, 13B protrusion, 14 mold pin, 14a cylindrical portion,
14b swelling part, 14c pedestal forming part, 14d base part,
20 studable tires (tires), 21 treads, 22 side parts,
23 circumferential grooves, 24 lug grooves, 25 blocks,
26 Stud embedding hole (stud hole), 26a trunk, 26b bulge,
26c Stud introduction part.

Claims (8)

A pair of side molds for molding the tire side portions;
A tire mold including a plurality of sector molds provided with a plurality of protrusions for forming a tread pattern on an inner peripheral surface,
The inner peripheral surface of the sector mold has a cylindrical portion positioned on the inner peripheral surface side of the sector mold and a bulge portion positioned radially inward of the cylindrical portion, and protrudes radially inward of the sector mold. The mold pin for forming the hole for burying the stud in the land part of the tire tread is arranged,
The shape of the bulging part when viewed from the radial direction of the sector mold is an ellipse whose major axis a is larger than the radius r of the cylindrical part and whose major axis direction is parallel to the width direction of the sector mold. A tire mold characterized by that.   2. The tire mold according to claim 1, wherein a ratio P = (a / b) of the major axis a to the ellipse minor axis b is in a range of 1.4 to 2.9.   3. The tire mold according to claim 1, wherein a minor axis b of the ellipse is equal to the radius r. Using a tire mold having a plurality of sector molds provided with a plurality of protrusions and mold pins on the inner peripheral surface, a studded tire in which a hole for burying a stud is formed in a land portion of a tire tread is manufactured. When
As the sector mold,
A cylindrical portion protruding radially inward from the inner peripheral surface of the sector mold; and a bulging portion located radially inward of the cylindrical portion, and the shape of the bulging portion when viewed from the radial direction of the sector mold. Is characterized in that a plurality of sector molds having mold pins whose major axis a is larger than the radius r of the cylindrical part and whose major axis direction is an ellipse parallel to the width direction of the sector mold are used. A method for manufacturing a studded tire. A tire mold having a pair of side molds and a plurality of sector molds is provided on the inner peripheral surface of the sector mold so as to protrude radially inward to form a hole for embedding a stud in the land portion of the tire tread. A mold pin that
The mold pin comprises a cylindrical portion located on the inner peripheral surface side of the sector mold, and a bulge portion located on the radially inner side of the cylindrical portion,
The shape of the bulging part when viewed from the radial direction of the sector mold is an ellipse whose major axis a is larger than the radius r of the cylindrical part and whose major axis direction is parallel to the width direction of the sector mold. Mold pin characterized by that. A studded tire in which a stud embedding hole for embedding a stud in a land portion of a tire tread is formed,
The stud embedding hole has a cylindrical trunk portion located on the tire tread side and a bulge portion located on the inner side in the tire radial direction of the trunk portion,
The shape of the bulging portion when viewed from the tire radial direction is an ellipse in which the major axis a is larger than the radius r of the trunk and the major axis direction is parallel to the width direction of the sector mold. Studded tires.   The studded tire according to claim 6, wherein a ratio P = (a / b) of the major axis “a” to the minor axis “b” of the ellipse is in a range of 1.4 to 2.9. The studable tire according to claim 6 or 7, characterized in that the minor axis b of the ellipse is equal to the radius r.

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