JPH08238625A - Sipe for tire mold and tire mold - Google Patents

Abstract

PURPOSE: To obtain sipes having high strength and precise shape and a tire mold, on the tread part molding surface of which the sipes are equipped, by a method wherein the sipe has a planer shape consisting of branched or closed figure. CONSTITUTION: A casting mold 21 is obtained by casting ceramic casting mold material with a rubber mold 17 for molding a casting mold and then turning the resultant material upside down. After that by casting ferrous alloy in the obtained casting mold 21, a sipe 23 for tire mold is produced. In the casting, a part 21b due to the stand of a master model serves the function of the pouring cup of molten metal and riser. As a result, molten metal reaches the details of the casting mold 21, and it is possible to obtain a sipe 23, the planer shape of the necessary part 23a of which has a branched or closed figure or a sipe of closed figure may be formed. In the obtained sipe 23, vent holes 25 are provided when necessary so as to prevent bubbles from staying behind in a tire molding and bears from developing in a tire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sipe for imparting a tread pattern to a tire, a method for manufacturing the sipe, and a tire molding die provided with the sipe. More specifically, the present invention relates to a high strength, fine and precise shape. The present invention relates to a sipe having the sipe and a tire molding die including the sipe.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 1 (a), a tire molding die has a structure in which divided gypsum molds 1 are arranged in a circle, and the outside of the gypsum mold 1 is surrounded by an annular molding frame 2 to form a mold 1. It is generally manufactured by filling the molten aluminum alloy 3 with the casting frame 2 (see FIG. 1 (b)). By the way, in a studless tire or the like, since fine grooves are usually formed in addition to the rib groove and the lug groove of the tread portion, in order to form such fine grooves on the molding surface of the tire molding die, A blade-shaped convex portion called “sipe” is formed.
The sipe is formed by casting using an aluminum alloy in the above-described conventional method for manufacturing a tire molding die, but there is a problem that the mechanical strength of the sipe becomes insufficient.

To solve this problem, as shown in FIGS. 2 (a) to 2 (c), a sipe 4 having a predetermined shape is prepared by cutting, press bending, etc. an iron-based plate material such as stainless steel,
The required portion 4a of the sipe 4 is wrapped in a gypsum mold 6 using a rubber mold 5 (see FIG. 2 (b)), and then aluminum alloy casting is performed using the mold 6 to obtain the intended required portion 4a. By exposing (see FIG. 2 (c)), a method of forming a sipe in a tire molding die has been performed.

[0004]

However, in such a conventional sipe forming method, since the plate material is cut or press-bent to give a desired shape to the sipe, the necessary portion 4a is sharply bent. It is difficult to provide the portion, and there is a problem that a sipe having a fine precision shape cannot be formed. On the other hand, it is possible to provide a sharp bent portion by wire electric discharge machining, but this is not practical because the manufacturing cost per sipe is extremely high.

Further, as shown in FIGS. 3 (a) to 3 (d), the required portion 4a has a planar shape (the required portion 4a in the direction from the center of the annular tire molding die to the tread portion molding surface).
Shape) has a branch or forms a closed figure, the necessary part 4a of the sipe is wrapped in gypsum, so as shown in FIG. Was also difficult to remove.
The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a sipe having high strength and a precise shape, and a tire molding die including the sipe. To do.

[0006]

Means for Solving the Problems As a result of intensive research aimed at achieving the above-mentioned object, the present inventor has provided a specific buried portion which functions as a pouring port for molten metal, and uses this to perform pouring casting. As a result, they have found that the above object can be achieved, and completed the present invention. That is, the tire molding die sipe of the present invention is characterized by having a planar shape in which a branched and / or closed figure is formed. The tire molding die of the present invention is characterized in that the sipe is provided on the tread portion molding surface.

The present invention will be described in detail below with reference to the drawings. The sipe for tire molding die of the present invention is manufactured by the following method. That is, first, the master model 9 having the same shape as the final product shape as shown in FIG. 5A is created in consideration of the casting shrinkage rate (multiplication rate). Next, the base 11 is provided on the obtained master model 9 and the prototype 1
3 is created (see FIG. 5 (b)). In this case, the master model 9 is used to form a necessary portion for providing fine grooves in the tread portion of the product tire, and the base 11 is used to form an embedded portion of the finally obtained sipe. Become. The shape of the base 11 is not particularly limited, but it is preferable that the base 11 has a shape like a rectangular parallelepiped having a top surface 11a having a sufficient area for mounting the master model 9.

Next, the prototype 13 created as described above
Is inverted with silicone rubber 15 or the like (see FIG. 5 (c)), the obtained waste rubber mold 15 is again inverted with silicone rubber or the like (FIG. 5 (d)), and as shown in FIG. A rubber mold 17 for forming a mold having the same shape as the above is obtained. Note that FIG.
As shown in (a) and (b), in the rubber mold 17 for making a mold, in addition to the method described above, a negative master 19 having a shape in which a master model is inverted is created by machining or the like. It is also possible to directly produce by reversing the rubber using.

Using the rubber mold 17 for making a mold obtained as described above, as shown in FIG. 8 (a), a casting mold 21 is obtained by casting and inverting with a ceramics casting material 21. Thereafter, the iron-based alloy 23 is injected into the obtained casting mold 21 to manufacture a tire mold sipe (see FIG. 7 (b)).
At the time of this injection, the portion 21b caused by the above-mentioned base 11 is
Since the melt serves as a pouring port and a feeder for the molten metal, the molten metal spreads to the details of the mold 23. Therefore, even if the wall thickness is about 0.4 mm, a sipe having a precise shape can be obtained, and a necessary portion can be obtained. It is possible to create a plane shape of 23a having a branch (see FIG. 8 (c)) or a closed figure.

The obtained sipe 23 can be provided with a vent hole 25, if necessary, to prevent air bubbles from remaining during tire molding and to prevent bare tires from being formed in the tire. be able to. Further, it is also possible to appropriately separate the necessary portion 23a and the embedded portion 23b, and thereby it is possible to obtain a sipe composed only of the necessary portion 23a (see FIG. 8 (b)). The sipe of the present invention thus obtained has a branched shape and / or a closed figure in the plan view of a necessary portion, and is also excellent in mechanical strength.

The buried portion 23b is buried in the molding surface of the tread portion of the tire molding die in which the obtained sipe is disposed, and functions to improve the mechanical strength of the sipe. 9 (a) and (b) locking holes 27 and undercuts 29 shown in FIGS. 10 (a) and 10 (b).
When the sipe is cast on the molding surface of the tread portion, the aluminum alloy penetrates into the locking hole 27 and is solidified, so that the connection between the aluminum alloy mold body and the sipe is further strengthened. can do. Further, the buried portion 23b can be used as a reference surface or a gripping portion when the vent hole 25 and the locking hole 27 are bored in the sipe 23 as described above, thereby improving workability of post-processing of the sipe. It also has the advantage that it can be done.

Further, as shown in FIGS. 11 (a) and 11 (b),
The top surface 23t of the embedded portion 23b has a curved surface that matches the tread portion molding surface 32 of the tire molding die 30 (molding surface 3
2). If the top surface 23t is formed in this way, it is possible to prevent the plaster burr from adhering to the vicinity of the root of the necessary portion 23a when forming the plaster mold as described above, and to create a sipe of a complicated shape. In this case, since the sipe shape can be accurately transferred, it is possible to manufacture a tire molding die having a clean molding surface without transfer defects.

Next, the tire molding die of the present invention is a tire molding die having the above-mentioned sipes on the molding surface of the tread portion, and such sipes are cast in an aluminum alloy according to a conventional method. Can be manufactured by.

[0014]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. (Embodiment 1) A necessary portion 40 having dimensions shown in FIG.
A prototype formed by connecting the table 42 having the dimensions shown in FIG. The dimensional unit in the figure is (mm). Then
Using this prototype, it was inverted with an ethyl silicate binder-curable ceramics mold material, and spheroidal graphite cast iron (FCD600) was injected into the obtained mold to obtain a sipe 44 as shown in FIG. As shown in the figure, sound sipes were obtained without casting defects.

Comparative Example 1 Sipe 4 as shown in FIG.
4 is a stainless steel plate with a plate thickness of 0.4 mm (SUS304)
I tried to make it by cutting out and bending it, but I could not make it. This is because the planar shape of the necessary portion 40 is a closed figure (square), and the four corners of this square cannot be bent at an acute angle and are formed into curved surfaces.

Example 2 Sipe 4 created in Example 1
4 was used to make a gypsum mold, and then the obtained gypsum mold was used to perform aluminum alloy casting to manufacture a tire molding die 44 as shown in FIG. At this time, the curved surface shape of the molding surface 46a of the molding die 46 and the curved surface shape of the embedded portion top surface 44t of the sipe 44 are made to coincide with each other (FIG. 1).
3). FIG. 16 shows an enlarged cross section taken along the line X-X in FIG. As shown in the figure, a shape due to gypsum burr did not occur at the root of the necessary portion 44a of the sipe 44, and a sound tire molding die could be produced.

(Comparative Example 2) Required part 40 shown in FIG.
A sipe 48 having the same shape as the above was made from a stainless material by a wire cutting method. Using the obtained sipe 48, a tire molding die was prepared in the same manner as in Example 2. FIG. 17 shows a cross section similar to that of FIG. As shown in the figure, the root portion 48d of the sipe 48 was found to have a shape abnormality due to a plaster burr and a mold flaw generated when the gypsum burr was removed. In the obtained tire molding die, these shape abnormalities were tried to be corrected by machining, but it is difficult to correct the inner portion 48e of the sipe, and the sound tire molding die obtained in Example 2 is difficult. Couldn't get

Example 3 A sipe (thickness: 0.6 mm) as shown in FIG. 18 was prepared in order to measure the bending strength characteristics of the sipe in the vicinity of the division surface of the tire molding die. The dimensional unit in the figure is (mm). Also, reference numerals 49a and 4
9b shows a vent hole and a rocking hole, respectively, and the line segment YY shows the allowance for cast metal made of aluminum alloy. The sipe 50 thus obtained was arranged as shown in FIG. 19, and a mechanical strength (bending strength) was measured by applying a load P. In the figure, reference numeral 50 is a sipe, 52 is an aluminum alloy, 54 is a pedestal, and 1 is 1 to 5 mm. As the bending strength, the maximum bending stress value applied to the sipe on the assumption that the cantilever has a one-point load was used as a representative value. The results obtained are shown in Table 1. The strength of the sipe with the buried portion was measured in the same manner, and the obtained results are also shown in Table 1.

[0019]

[Table 1]

As shown in Table 1, when the sipe of the present invention is used, high strength can be maintained as compared with the conventional method even when the sipe is installed near the dividing surface of the aluminum alloy mold body. (D = 0.5, the conventional method 1.6-
A bending strength of 2.8 times is obtained. ). This is considered to be due to the fact that when the sipe is installed in the immediate vicinity of the dividing plane, the strength is determined by the remaining part (ligament) of the aluminum die body rather than the strength of the sipe itself in the conventional method.
Therefore, in the conventional method, the smaller the value of d, the smaller the bending strength. On the other hand, in the case of the present invention, the strength is determined by the embedded part that is an integral part of the iron-based material and is integrated with the necessary portion, so the bending strength does not change even if the value of d changes. is there. Therefore, it is considered that the sipe of the present invention exerts its effect particularly when it is installed in the immediate vicinity of the dividing surface.

[0021]

As described above, according to the present invention,
A sipe with a high strength and a precise shape, and a tire forming metal having the sipe, were provided because a molten metal pouring port and a specific buried portion that functions as a feeder were provided and casting casting was performed using this. A mold can be provided.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a conventional tire molding die.

FIG. 2 is a cross-sectional explanatory view showing a sipe making method in a conventional tire molding die.

FIG. 3 is a plan view showing the shape of a sipe.

FIG. 4 is a cross-sectional explanatory view showing a state in which burrs are attached to sipes.

FIG. 5 is an explanatory view showing a manufacturing process of the sipe of the present invention.

FIG. 6 is a perspective view showing an example of a rubber mold for making a mold according to the sipe of the present invention.

FIG. 7 is an explanatory view showing the manufacturing process of the sipe of the present invention.

FIG. 8 is an explanatory view showing the manufacturing process of the sipe of the present invention.

FIG. 9 is a side view showing an example of a locking hole.

FIG. 10 is a side view showing an example of undercut.

FIG. 11 is a perspective view showing another example of the sipe of the present invention.

FIG. 12 is an explanatory view showing a shape of a necessary portion of a prototype according to the sipe of the present invention.

FIG. 13 is an explanatory view showing the shape of a prototype base according to the sipe of the present invention.

FIG. 14 is a perspective view showing an example of the sipe of the present invention.

FIG. 15 is a partial cross-sectional view showing an example of the tire molding die of the present invention.

16 is an enlarged cross-sectional view taken along the line X-X in FIG.

FIG. 17 is a partial cross-sectional view of a tire molding die according to a conventional method.

FIG. 18 is a cross-sectional view showing a sipe shape.

FIG. 19 is an explanatory cross-sectional view showing a method for measuring mechanical strength.

[Explanation of symbols]

9 ... Master model, 11 ... Stand, 13 ... Prototype, 15 ...
..Disposal rubber mold, 17 ... Rubber mold for making mold, 19 ... Negative master, 21 ... Casting mold, 30 ... Tire molding mold, 40 ... Necessary part, 42 ... * Stand, 44 ... sipe, 4
6 ... tire molding die, 46a ... molding surface

Claims (4)

[Claims] 1. A sipe for a tire molding die, which has a planar shape in which a branched and / or closed figure is formed. 2. The sipe according to claim 1, further comprising a buried portion. 3. The sipe according to claim 2, wherein the top surface of the buried portion constitutes a part of the molding surface of the tire tread portion. 4. A tire molding die comprising the tread portion molding surface provided with the sipe according to any one of claims 1 to 3.