JP3239078B2 - Tire mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for molding tires,
The present invention relates to a tire molding die capable of molding a tire having high dimensional accuracy and good appearance.

[0002]

2. Description of the Related Art FIG. 1 shows a conventional tire molding die.
There are known a vertically divided mold as shown in FIG. 1 and a radially divided mold as shown in FIG. 12, and in such a mold, a mold is used at the time of tire vulcanization molding. In order to discharge gas such as air sealed between the unvulcanized rubber and the outside of the mold, a large number of small holes called vent holes communicating with the inside and outside of the mold have been formed. However, there is a problem in that the operation of drilling such a vent hole requires skill and the number of drilling holes increases the number of steps, resulting in insufficient mold manufacturing efficiency. In addition, the vent hole generates hairy rubber called spew on the surface of the formed tire, and it must be removed. Even if it is removed, a trace is likely to remain on the tire surface, and this trace is likely to remain. However, there is a problem that the appearance of the tire is impaired or the initial running characteristics of the tire are impaired. Furthermore, when the molding of the tire is repeated using the mold as described above, the spew is cut and remains in the vent hole, or the vent hole may be clogged due to accumulation of dirt such as rubber, and the like. As a result, the air bleeding effect is reduced, causing a problem called an avatar-shaped bear on the tire surface. For this reason, it is necessary to remove the foreign matter in the vent hole and always keep the vent hole. Since the mold surface is contaminated with polymer carbon and other inorganic substances, it is necessary to periodically clean the mold.After this cleaning, all vent holes are manually exposed to foreign substances using a drill or the like. And the maintenance of the mold is complicated.

To solve such a problem, Japanese Patent Laid-Open Publication No.
In Japanese Patent Application Laid-Open No. 3108 and Japanese Patent Application Laid-Open No. 5-220753, a tread forming part 13 for applying a tread pattern to a tire is divided into a plurality of pieces 1 by using a segment type tire forming die as shown in FIG. Holder 15
By properly controlling the adjacent distance between the pieces during mold assembly to prevent the rubber component from being discharged and providing a gap for bleeding air, the number of vent holes can be reduced or eliminated. It is disclosed. Also, piece 1
To provide the air vent clearance by dividing
It is also described that the present invention is applicable to a mold as shown in FIG. However, even in a mold in which pieces are divided and arranged adjacently as described above, similarly to a normal tire molding mold, when the tire is molded several hundred to several thousand times, the mold surface becomes dirty, and the obtained tire has Since the appearance is impaired, dirt such as rubber accumulates in the vent holes and air vent gaps between the pieces, and bears are generated, it is necessary to periodically clean the mold several hundred to several thousand times every molding. is there. In the above-mentioned piece-parting mold, this cleaning for removing dirt such as rubber which has entered the air vent gap removes each piece from the holder,
This is performed by blast cleaning in which powder such as glass beads and iron powder is sprayed on each piece. FIG. 13 is a perspective view partially showing an example of a tire molding die. FIG.
2 shows a part of a segment type mold as shown in FIG. The piece 1 forms a tread pattern of the entire tire with all the pieces, and a convex pattern (bone portion and blade portion) for forming a tread pattern on the tire is formed on a molding surface 7 thereof ( Not shown.)

[0004]

The mold which is divided into pieces and arranged adjacent to each other can prevent the occurrence of spew and can prevent the clogging of the vent hole due to the cut of the spew, as compared with the conventional tire molding mold. However, there was a problem that the accumulation of dirt such as rubber between the pieces did not decrease, and the pieces had to be frequently separated and blasted. The present invention has been made in the context of such a situation, and its purpose is to suppress the accumulation of dirt such as rubber infrequently, to perform effective air bleeding, to easily perform maintenance, Another object of the present invention is to provide a mold for molding a tire which does not impair the appearance of the tire.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, there are provided a plurality of annularly shaped pieces for imparting a tread pattern to a product tire, and a plurality of circumferentially arranged pieces. In a tire molding die provided with a holder that can be mounted adjacent to the direction, the piece has a molding surface that provides a part of a tread pattern, and an adjacent surface that abuts or approaches another piece, A holder and a back surface in contact with or close to the holder, and at least one air vent slit between adjacent surfaces of the pieces;
The width of the opening of the slit is 10 μm to 200 μm, and the length of the opening of the slit is 5 mm or more.
And the surface roughness of the inner wall of the slit is Rmax 3 μm or less.
And wherein the lower der Rukoto. The width of the slit opening is 1
If it is 0 μm or less, it is difficult to effectively release air, and if the width of the opening of the slit exceeds 200 μm, the protruding height of rubber at the time of molding the tire becomes large, which is not preferable because the appearance of the product tire is impaired. The width of the slit from a point advanced from 0.3 to 5.0 mm from the opening of the slit as in the invention according to claim 2, in order to further reduce airflow resistance in the slit in order to effectively release air. And the plurality of slits may be 0.3 to 5.0 mm from the opening of the slit.
They can communicate with each other at advanced points.

On the other hand, in order to prevent the contamination of rubber or the like generated in the slit, the surface roughness of the inner wall of the front Symbol slits Rmax
It is preferably 10 μm or less, more preferably 3 μm or less. Also, as in the invention of claim 4, wherein, it is preferable to form at least one end of the slit at the base end of the projection (bone). Since the flow of gas such as air tends to accumulate at the base of the protruding portion in the closed area defined by the protruding portion (hereinafter referred to as a blocking block), a slit is provided in that portion to allow gas such as air to escape. Make it easier. Here, the convex portion refers to a bone portion for forming a tread pattern on the tire. Further, as in the invention according to claim 5 , the piece is made of an iron-based alloy or a copper-based alloy. Iron-based alloys are preferred because of their low reactivity with rubber components, and among iron-based alloys, considering castability and strength for accurately casting a molding surface, spheroidal graphite cast iron, or carbon steel cast steel, Is particularly preferred. Further, as a copper-based alloy, a BeCu alloy (particularly, 1.0 to 3.0% by weight)
Is excellent in castability, hardness and thermal conductivity, and is excellent.
When using this alloy, it is preferable to apply Ni and / or Cr plating to the surface of the alloy because of its reactivity with the rubber component. In the case of using cast carbon steel, in consideration of the castability (low melting point) and the improvement in hardness, a composition equivalent to S40C to S55C containing 0.4 to 0.6% by weight of carbon may be used. Preferred, but also Ni, Cr, Mo
It is more preferable to use one containing a hardenability improving component such as

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, FIGS. 1 and 2 are perspective views showing different embodiments of the slit opening length of each piece, and FIGS. 3 and 4 are embodiments in which the slit length on the back side of the piece is longer than the slit opening length. FIG. 5 is a perspective view showing an embodiment in which a plurality of slits are connected, and FIGS. 6 and 7 are partial perspective views showing a positional relationship between a slit end and a bone end, FIGS. 9 is a diagram showing a slit forming position viewed from a molding surface, and FIG. 10 is a cross-sectional view showing an embodiment in which the width of the slit on the back side of the piece is larger than the width of the slit opening. 1 and 2 show perspective views showing different embodiments of the slit opening length of each piece. In FIG. 1, the width of the opening of the slit is 20 μm, and the length of the opening of the slit is 5 mm.
The width of the opening of the slit was 20 μm, and the length of the opening of the slit was from a convex to a convex. in this case,
Since the ventilation resistance is determined by the area of the opening of the slit,
It is advantageous to increase the length of the opening of the slit and reduce the width of the opening of the slit, since the height of the spew can be reduced. However, the width of the slit opening is 10
If it is less than μm, clogging due to accumulation of dirt such as rubber is accelerated. In addition, the protruding rubber that has entered the slit is likely to be cut off during mold release and to remain easily, which may cause clogging. On the other hand, if the width of the opening of the slit exceeds 200 μm, the protruding height of the rubber component at the time of tire molding becomes large, and the appearance of the product tire is impaired. The length of the opening of the slit is preferably 5 mm or more from the viewpoint of ventilation resistance.
In addition, it is desirable that at least one slit is disposed at a portion forming a closed block in a tread portion of a product tire.

FIG. 3 is a perspective view showing an embodiment in which the slit length on the back side of the piece is longer than the length of the slit opening. The ventilation resistance can be reduced by increasing the slit length. The width of the slit opening is 20
μm, the length of the opening of the slit was 5 mm, and the length of the slit was 15 mm from a point 2.0 mm deep from the opening of the slit. Note that, besides increasing the slit length discontinuously (stepped) as shown in FIG. 3, it is also possible to increase the slit length continuously as shown in FIG. If the depth dimension is smaller than 0.3 mm, the protruding rubber height exceeds this, resulting in rubber breakage, and the cut rubber remains in the slit, which is not preferable.

FIG. 10B is a sectional view showing an embodiment in which the width of the slit on the back side of the piece is larger than the width of the slit opening. The ventilation resistance can be reduced by increasing the slit width. FIG. 10A is a cross-sectional view when the width of the slit opening is uniform.

FIG. 5 is a perspective view showing an embodiment in which a plurality of slits are connected. The width of the slit opening is 20μ
m, the length of the opening of the slit is 5 mm,
The slit was communicated with another slit at a depth of 2.0 mm from the opening of the slit. By connecting the slits, the airflow resistance can be reduced, and the air at locations where air pockets are likely to be generated can be efficiently removed.

FIGS. 6 and 7 are partial perspective views showing the positional relationship between the slit end and the bone end. FIG. 6 shows a piece in which one end of the slit is formed at the base end of the projection, and FIG.
Indicates a piece in which one end of the slit is slightly inside the root of the projection. The piece shown in FIG. 7 is easier to process. Conventionally, air traps tend to be easily generated in the blockage block, particularly at the base of the bone, but by applying the slit of the present embodiment, it is possible to prevent the occurrence of air traps.

FIG. 8 and FIG. 9 are views showing the formation position of the slit as viewed from the molding surface. In FIG. 8, a slit opening is formed by forming a groove in one adjacent surface of an adjacent piece, and in FIG. 9, a slit opening is formed by forming a groove in both adjacent pieces. did. Any can be selected as long as a predetermined opening area can be secured. FIG. 8 is preferable because the number of processing surfaces is small.

The material of the piece was an iron-based alloy or a copper-based alloy. The slits were machined. However, known techniques such as blasting, etching, and electric discharge machining can be appropriately applied.

In the present invention, the surface roughness of the slit is R _MAX 1
It was set to 0 μm. As a result of performing tire molding and analyzing components of dirt such as deposited rubber, Fe was detected from dirt collected from a conventional mold (surface roughness is generally 20 to 30 μm). No Fe component was detected from the embodiment. This shows that by reducing the surface roughness, dirt is not easily deposited and dirt can be easily removed.

[0015]

As described above, according to the present invention,
It is possible to perform effective air bleeding while keeping the accumulation of dirt such as rubber infrequently, easy maintenance,
Further, the present invention is extremely useful because it does not impair the appearance of the tire.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a slit of a piece.

FIG. 2 is a perspective view of a piece according to another embodiment.

FIG. 3 is a perspective view of a piece according to another embodiment.

FIG. 4 is a perspective view of a piece according to another embodiment.

FIG. 5 is a perspective view of a piece according to another embodiment.

FIG. 6 is a partial perspective view of a piece according to another embodiment.

FIG. 7 is a partial perspective view of a piece according to another embodiment.

FIG. 8 is a plan view of a piece according to another embodiment.

FIG. 9 is a plan view of a piece according to another embodiment.

FIG. 10 is a cross-sectional view of a piece according to another embodiment.

FIG. 11 is an exploded perspective view showing an example of a conventional tire molding die.

FIG. 12 is an exploded perspective view showing an example of a conventional tire molding die.

FIG. 13 is an enlarged perspective view of a part of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 piece 3 Slit 5 Convex part 7 Molding surface 9 Adjacent surface 11 Back 15 Holder 19 Segment

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI B29L 30:00 B29L 30:00

Claims (5)

(57) [Claims] 1. A tire molding die comprising: a plurality of generally annular pieces for imparting a tread pattern to a product tire; and a holder on which these pieces can be mounted adjacent to each other in a circumferential direction. A molding surface that provides a part of the tread pattern, an adjacent surface that abuts or approaches another piece, and a back surface that abuts or approaches the holder, between the adjacent surfaces of the pieces. at least provided with one air vent slit, a width of 10μm to 200μm of the opening of the slit state, and are the length of the opening is more than 5 mm of the slit, and the slit
Tire mold which surface roughness of the inner wall of characterized der Rukoto following Rmax3myuemu. 2. The method according to claim 1, wherein said slit has an opening of 0.3 to 5.
2. The tire molding die according to claim 1, wherein the width of the slit is increased from a point advanced by 0 mm. 3. The tire molding die according to claim 1, wherein the plurality of slits communicate with each other at a point advanced by 0.3 to 5.0 mm from an opening of the slit. 4. A tire mold according to any one of claims 1 to 3 one end of the at least one slit of said slit is formed in the convex portion base end. Wherein said piece, the tire mold according to any one of claims 1 to 4 made of an iron-based alloy or copper-based alloy.