JP2006289737A - Tire vulcanizing mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent rubber from being caught without deteriorating the drainage properties of a product tire when a green tire of a small expansion ratio set value during vulcanization is vulcanized by a tire vulcanizing mold in which protrusions for forming main grooves extending in the peripheral direction of a tread part in the inner surface of each of a plurality of segmented molds divided in the tire peripheral direction is formed to form the tread part. <P>SOLUTION: In the inner surface of the segmented mold, the protrusions 31 and 33 for forming the main grooves of the tread part are formed. In the protrusions 31 and 33, chamfering parts 31b and 33b are formed at the side and bottom edges of edge parts 31a and 33a in the end surface in the peripheral direction of the segmented mold. When the protrusions of the adjacent segmented molds are coming into contact with each other, the rubber put between the protrusions escapes to the chamfering parts 31b and 33b to be prevented from being caught. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tire vulcanization mold in which an annular tread mold for forming a tread portion of a tire is composed of a plurality of segment molds divided in the circumferential direction, and more specifically, an expansion rate setting at the time of vulcanization The present invention relates to a tire vulcanization mold that can prevent the biting of rubber without inhibiting the drainage of a product tire when vulcanizing a green tire having a small value.

  Some molds used for vulcanizing green tires are called split molds. This mold is an annular tread mold comprising a pair of upper and lower side molds for molding a sidewall portion of a tire and a plurality of arc-shaped segment molds that are divided in the tire circumferential direction and can be expanded and contracted in the tire radial direction. And have.

  In this divided mold, the upper side mold is opened, and the green tire is disposed on the lower side mold in a state where the plurality of segment molds are expanded and opened in the radial direction. Each segment mold then shrinks radially inward to form an annular tread mold, the upper side mold is closed, and the green tire is enclosed in the mold. Next, the green tire is heated and pressurized, and the inflatable bladder pushes the green tire into the inner surface of the mold while the tread portion and the sidewall portion are formed in the mold. When vulcanization is complete, the mold is opened and the vulcanized tire is removed.

  Here, when the green tire sealed in the mold is pushed into the inner surface of the mold by the bladder, the bias tire has a large expansion rate at the time of vulcanization due to the structure of the cord arrangement. Even if the outer diameter of the tire is smaller than the inner diameter of the main groove forming protrusion provided on the inner surface of the segment mold to form the main groove extending in the tire circumferential direction, the pressing force on the inner surface of the mold will not be insufficient. . However, in the case of aircraft tires, for example, high tension cords of aramid fiber cords are spirally wound in the circumferential direction for the purpose of improving high-speed durability, so the diameter expansion rate in the mold is almost 0%. There is extremely small. Therefore, in order to ensure a sufficient pressing force against the inner surface of the mold, it is necessary to make the outer diameter of the green tire arranged in the mold larger than the inner diameter of the main groove forming protrusion.

  However, when the outer diameter of the green tire and the inner diameter of the main groove forming protrusion have the above relationship, when the plurality of segment molds are contracted radially inward, the segment molds adjacent to each other There is a problem that the main groove forming protrusions bite the outer peripheral surface of the green tire at the circumferential end surfaces. Since such a bite rubber becomes irregular burrs and remains in the groove, the appearance of the product tire is impaired and the commercial value is lowered. Further, a part of the bitten rubber falls on the inner surface of the lower side mold and adheres to the surface of the green tire to be carried in next, causing a chronic appearance defect.

Therefore, in order to solve such problems, the main groove forming ridges of the segment mold are configured such that the upper surface (ridge top surface) is notched low at the end in contact with the adjacent segment mold. Then, when the adjacent main groove forming ridges try to contact each other, a mold has been proposed in which the rubber that has entered between them is allowed to escape into the notched portion (see Patent Document 1). .
Japanese Utility Model Publication No. 63-182109

  However, in the mold disclosed in Patent Document 1, the volume for releasing the rubber protruding from the outer peripheral surface of the green tire is configured by a notch of only the top surface of the ridge. The dimension of the notch tire circumferential direction or radial direction becomes large. For this reason, the tire vulcanized by the mold is formed with projections having a large length or height corresponding to the notches of the ridges at a plurality of locations on the bottom surface of the main groove of the tread portion. Drainage is hindered. It is possible to prevent the drainage from being deteriorated by cutting out the protrusions, but the productivity decreases due to the increase in the number of man-hours.

  The present invention has been made in order to solve such problems, and an object of the present invention is to provide an annular tread mold for forming a tread portion of a tire by a plurality of segment molds divided in the circumferential direction. A green tire having a small expansion rate set value at the time of vulcanization by a tire vulcanization mold having a protrusion for forming a main groove extending in the circumferential direction of the tread portion on the inner surface of the segment mold. This is to prevent the biting of rubber without damaging the drainage of the product tire when vulcanizing.

In the invention according to claim 1, the annular tread mold for forming the tread portion of the tire is constituted by a plurality of segment molds divided in the circumferential direction, and the circumferential direction of the inner surface of the segment mold is In the tire vulcanization mold provided with a protrusion for forming a main groove extending in the circumferential direction of the tread portion, the protrusion is chamfered on a side edge and a bottom edge on at least one end face in the circumferential direction of the tread mold. The tire vulcanization mold is characterized by the above.
The invention according to claim 2 is the tire vulcanizing mold according to claim 1, wherein the chamfered portion has a length in the tire meridian direction of 2.5 mm to 3.5 mm. It is a type.
The invention according to claim 3 is the tire vulcanizing mold according to claim 1, wherein the chamfered portion has a tire circumferential length of 0.78 mm or more and 0.80 mm or less. It is a type.

(Function)
According to the inventions according to claims 1 to 3, since the chamfered portions are formed on the side edge and the bottom edge of at least one end surface in the circumferential direction of the ridge, the rubber tire bites during vulcanization. Can be prevented. Compared with the conventional example in which long and high protrusions are formed in the main groove of the product tire by forming a chamfered portion for obtaining a volume for releasing rubber only at the bottom edge of the end of the protrusion, Since the height and length of the protrusions formed on the side and bottom surfaces of the main groove of the product tire are smaller than those of the conventional example, the drainage performance is reduced. Can be reduced as compared with the prior art.

  According to the present invention, the annular tread mold for forming the tread portion of the tire is constituted by a plurality of segment molds divided in the circumferential direction, and in the circumferential direction of the inner peripheral surface of the segment mold, Drainability of the product tire when vulcanizing a green tire with a small expansion rate set value during vulcanization by a tire vulcanization mold provided with a protrusion for forming a main groove extending in the circumferential direction of the tread part It is possible to prevent the biting of rubber without deteriorating.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 is a cross-sectional view of a tire vulcanization mold according to an embodiment of the present invention, FIG. 2 is a top view of an upper side mold and an upper segment mold in FIG. 1, and a bottom view of a lower side mold and a lower segment mold.

  As shown in FIGS. 1 and 2, the tire vulcanization mold according to the present embodiment includes an upper side mold 1, a lower side mold 2, an upper segment mold 3, a lower segment mold 4, an upper holder 5, and a lower holder 6. I have.

  The upper side mold 1 and the lower side mold 2 are annular. The upper segment mold 3 and the lower segment mold 4 are each composed of 10 segments, and are combined in the vertical and circumferential directions to form an annular tread mold having a mold molding surface corresponding to the tire outer surface of the tire tread portion. Form. Moreover, the upper side mold 1 and the lower side mold 2 have a mold molding surface corresponding to the sidewall portion of the tire. The upper holder 5 and the lower holder 6 move integrally with the upper segment mold 3 and the lower segment mold 4 in the tire radial direction, respectively, and are combined in the vertical and circumferential directions when the mold is closed, so that the outer peripheral surface of the mold is Constitute.

  On the inner surface of the upper segment mold 3 are provided protrusions 31, 32, 33 for forming three main grooves extending in the circumferential direction on one side of the equator of the tread portion of the tire. Further, on the inner surface of the lower segment mold 4, there are provided ridges 41, 42, 43 for forming three main grooves extending in the circumferential direction on the other side of the equator of the tread portion of the tire. Further, one end surface of each upper segment mold 3 in the tire circumferential direction, that is, one of the surfaces that come into contact with the adjacent upper segment mold 3 when combined in an annular shape (in the clockwise direction shown at the tip of the arrow in FIG. 3). The rear end face 3a) was chamfered. Similarly, chamfering was performed on one of the end surfaces on the tire circumferential direction side of each lower segment mold 4 (counterclockwise rear end surface 4a shown at the tip of the arrow in FIG. 4).

  FIG. 3 is a view showing a chamfered portion formed on the ridge 31 and a chamfered portion formed on the ridge 33. Here, (a) and (b) are views of the protrusions 31 and 33, respectively, viewed from the end surface side on the tire circumferential direction side, and (c) is the direction of arrows AA in (a) and (b). It is the figure seen from.

  As shown in (a) and (b) of this figure, the cross-sectional shape of the ridges 31 and 33 is a semi-circular shape at the distal end side, a substantially trapezoidal shape at the central portion, and a shape like a mountain hem at the proximal end side, It can be said that the shape is like a mountain as a whole. Further, the chamfered portion 31b was formed on the entire edge portion 31a (side edge and bottom edge) of the end surface of the protrusion 31 on the tire circumferential direction side. Thereby, the outline of the edge of the end face becomes 31c. In setting the shape and size of the chamfered portion 31b, consideration was given so that the effect of preventing rubber biting during vulcanization was exhibited and the drainage of the product tire was not deteriorated. Therefore, it does not perform rubber escape processing that clearly blocks the bottom of the main groove, but absorbs the amount of protrusion due to rubber biting by the main groove forming ridge, based on the shape linked to the main groove cross-sectional shape. The chamfered portion has a minimum width and depth so that the volume can be obtained. In the present embodiment, the chamfered portion 31b is symmetric with respect to the center line 31d in the tire radial direction, and as shown in (c) of this figure, the length in the tire meridian direction of the chamfered portion 31b is 2.5 mm or more and 3.5. The length in the tire circumferential direction is 0.78 mm or more and 0.80 mm or less. If the upper limit of these numerical ranges is exceeded, the height and circumferential length of the protrusions formed on the side surface and the bottom surface of the main groove of the tire become large, and the drainage performance deteriorates. If the lower limit is not reached, the effect of preventing rubber biting during vulcanization is reduced.

  The protrusion 31 has been described above, but the protrusion 32 has the same configuration. Further, the protrusion 33 located close to the upper side mold 1 is the same as the protrusion 31 except that the radius of curvature of the inner surface of the upper segment mold 3 is small, and the end surface on the tire circumferential side is the same. A chamfered portion 33b is formed with respect to the entire edge portion 33a, and the contour of the edge portion is 33c. Further, the chamfered portions formed on the ridges 41, 42, 43 of the lower segment mold 4 are the same as the chamfered portions formed on the ridges 31, 32, 33, respectively.

  According to the tire vulcanizing mold according to the present embodiment having the above-described configuration, the upper side mold 1 is moved upward by means not shown, and the upper segment mold 3 is opened in the tire radial direction by the upper holder 5. The green tire is arranged on the lower side mold 2 with the lower segment mold 4 expanded by the lower holder 6 in the tire radial direction and opened. This green tire is a tire having a small expansion rate set value during vulcanization in a mold, such as an aircraft tire, and has an outer diameter larger than the inner diameter of each protrusion. Next, the upper and lower segment molds 3, 4 are contracted radially inward in the reverse order of opening, the upper side mold 1 is closed, and the green tire is sealed in the mold. The inflatable bladder pushes the green tire into the inner surface of the mold while being heated and pressurized to form the tread and sidewall surfaces in the mold. When vulcanization is complete, the mold is opened and the vulcanized tire is removed.

  Here, the upper and lower segment molds 3 and 4 shrink radially inward, and when the adjacent main groove forming ridges try to contact each other, the rubber that has entered between them escapes into the chamfered portion, so that it is bitten. Disappear. According to the experiment, the appearance defect occurrence rate was reduced to about 1/10 compared with the case where the chamfered portion was not formed. In addition, the height and circumferential length of the protrusions formed on the side and bottom surfaces of the main groove of the tread portion of the product tire corresponding to the chamfering do not impair drainage, so the drainage of the product tire does not deteriorate. .

  In the above embodiment, the chamfered portion is formed only on one end surface of each protrusion in the tire circumferential direction, but the chamfered portion may be formed on both end surfaces. In this case, since the number of chamfered portions formed on each end surface can be smaller than when formed on only one end surface, the height or circumferential length of the protrusions formed on the side surface and bottom surface of the main groove corresponding to the chamfered portion is reduced. Therefore, the influence on drainage can be further reduced. Moreover, in the above embodiment, although the whole side edge of the circumferential direction end surface of each protrusion was chamfered, you may chamfer a part of side edge.

1 is a cross-sectional view of a tire vulcanization mold according to an embodiment of the present invention. FIG. 2 is a top view of the upper side mold and the upper segment mold in FIG. 1 and a bottom view of the lower side mold and the lower segment mold in FIG. 1. It is a figure which shows the chamfering formed in the protrusion of FIG.

Explanation of symbols

  3 ... Upper segment mold, 4 ... Lower segment mold, 31, 32, 33, 41, 42, 43 ... Projection, 31b, 33b ... Chamfer.

Claims (3)

An annular tread mold for forming a tread portion of a tire is composed of a plurality of segment molds divided in the circumferential direction, and extends in the circumferential direction of the inner surface of the segment mold in the circumferential direction of the tread portion. In the tire vulcanization mold provided with protrusions for forming grooves,
The tire vulcanization mold according to claim 1, wherein a side edge and a bottom edge of at least one end face in the circumferential direction of the tread mold are chamfered. In the tire vulcanization mold according to claim 1,
The tire vulcanization mold, wherein the chamfered portion has a length in a tire meridian direction of 2.5 mm to 3.5 mm. In the tire vulcanization mold according to claim 1,
The tire vulcanization mold, wherein the chamfered portion has a length in the tire circumferential direction of 0.78 mm or more and 0.80 mm or less.

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