JP2015013315A - Device for casting metal mold for tire molding, and method for casting metal mold for tire molding using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a casting device for a metal mold for tire molding capable of preventing bubble defect without needing a complicated large equipment investment or expensive production cost, and to provide a casting method for the metal mold using the device.SOLUTION: A casting device for a metal mold for tire molding is provided with: a casting die 1 for casting the metal mold for tire molding; an annular frame body 2 disposed around the casting die; and a molten metal-pouring tool 4 detachably installed to one or multiple notched openings 3 provided on a part of the lower portion of the frame body 2. The molten metal-pouring tool 4 is composed of an upper casting port 5, a lower squeezing port 6, and a vertical flow path 7 therebetween. The sectional area of the squeezing port 6 is equal to or less than 1/20 of the sectional area of the vertical flow path 7, and a sprue 14 extends from the squeezing port 6 to the lower end face of a bottom of the molten metal-pouring tool 4.

Description

  The present invention relates to a tire molding die casting apparatus and a tire molding die casting method using the same, and more specifically, it is possible to prevent bubble defects without requiring complicated and large equipment investment and high manufacturing cost. The present invention relates to a tire molding die casting apparatus and a tire molding die casting method using the same.

  Tire molds are generally manufactured by casting methods because of the complexity of the design and the ability to cast thin plates (sipes, blades) made of different metal materials. The plaster casting method is widely adopted. The reasons are as follows: (1) Casting with melting point up to about aluminum alloy can be manufactured with high dimensional accuracy, (2) Easy cutting and assembly at the stage of gypsum mold, (3) Casting of sipes and blades And (4) a complicated design shape can be accurately transferred by casting inversion from a rubber mold.

  However, when casting tire molds by the gypsum casting method, casting defects often become a problem, and among them, `` bubble defects '' that occur when air is involved during pouring and air bubbles stick to the surface of the gypsum mold Is a problem that occurs most frequently. Various studies have been made on the countermeasure technology for the bubble defect. For example, Patent Document 1 relates to a molten metal pouring method using a low pressure casting method, and discloses a technique for minimizing entrainment of bubbles during pouring. Further, Patent Document 2 relates to a molten metal pouring method using a special chute for gravity casting, and a technique for avoiding bubble defects by floating and separating entrained air bubbles between the casting frame and the deflector. Is disclosed. Furthermore, Patent Document 3 relates to a molten metal pouring method using a runner surface plate that can be used repeatedly in gravity casting, and a technique for floating and separating entrained bubbles during pouring in a runner to avoid bubble defects. It is disclosed.

JP-A-57-58968 (Claims etc.) Japanese Patent No. 2796010 (Claims etc.) JP 2007-144480 A (Claims etc.)

  However, the method described in Patent Document 1 requires a complicated and large capital investment, increases the manufacturing cost, and is not suitable for a large tire. Further, the method described in Patent Document 2 cannot cope with a thin casting, and it is difficult to completely remove bubble defects. Furthermore, the technique described in Patent Document 3 increases the size of the pouring jig and widens the casting space. Thus, it cannot be said that the conventional countermeasure technique for bubble defects is sufficient, and further improvement has been demanded.

  Accordingly, an object of the present invention is to provide a tire molding die casting apparatus and a tire molding die casting method using the same, which can prevent bubble defects without requiring complicated and large capital investment and high manufacturing cost. There is to do.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that the above object can be achieved by adopting the following configuration, and has completed the present invention.

That is, a tire molding die casting apparatus according to the present invention includes a mold for casting a tire molding die, an annular frame disposed around the mold, and one piece provided at a part of the lower portion of the frame. Or, in a casting apparatus for a tire molding die, comprising a pouring jig detachably attached to a plurality of notch openings,
The pouring jig is composed of an upper casting port, a lower throttle port, and a vertical channel between them, and the sectional area of the throttle port is less than 1/20 of the sectional area of the vertical channel. And a sprue extends from the throttle port to the lower end surface of the bottom of the pouring jig.

  In the present invention, it is preferable that a channel cross-sectional diameter of the notch opening is the same as or smaller than the vertical channel cross-sectional diameter. Moreover, a wall part can be provided in the lower end surface of the bottom part of the said pouring jig, a hot water reservoir part can be formed, and a wall part can be suitably provided in the upper surface of the flow path to the said notch opening part of this hot water reservoir part. .

Further, the tire molding die casting method of the present invention is a method for casting a tire molding die using the tire molding die casting apparatus of the present invention,
After pouring the molten metal into the casting port on the upper part of the pouring jig and filling the molten metal between the mold and the annular frame disposed around the mold, solidifying the filled molten metal, The casting main body and the pouring jig are broken and separated at the notch of the frame.

  According to the present invention, with the above-described configuration, it is possible to provide a tire molding die casting apparatus that can prevent bubble defects without requiring complicated and large capital investment and high manufacturing cost. . Moreover, this casting apparatus is easy to reuse. Furthermore, the tire molding die cast using this casting apparatus has few bubble defects and has excellent quality.

1 is a cross-sectional view of one preferred embodiment of the present invention. It is XX sectional drawing of one suitable Example of this invention. It is a horizontal sectional view of other embodiments in the present invention. It is explanatory drawing of the behavior of the bubble in a vertical flow path. It is explanatory drawing showing the relationship between the fluid resistance Fr added to a bubble, and the buoyancy Ff. It is an expanded sectional view of the hot water sump part in other embodiments of the present invention. It is an expanded sectional view of the hot water sump part in other embodiments of the present invention. It is an expanded sectional view of the pouring jig connection part of a reference example. It is an expanded sectional view of the pouring jig connection part of Example 1 and a comparative example. FIG. 6 is an enlarged cross-sectional view of a pouring jig connecting portion of Example 2.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view of a tire molding die casting apparatus according to a preferred embodiment of the present invention, and FIG. 2 is an XX cross-sectional view. As shown in FIG. 1, the mold 1 and the frame 2 arranged in the periphery of the mold 1 are provided with one or a plurality of notch openings 3, and the molten alloy is filled from the outside of the frame 2. A pouring jig 4 detachable with screws or the like that can be attached is attached. By directly connecting the pouring jig 4 to the notch opening 3, the size can be made smaller than that of a conventional casting apparatus. Moreover, the pouring jig 4 is configured such that an upper casting port 5, a lower throttle port 6, and a vertical flow path 7 therebetween can be attached and detached with screws or the like. In the present invention, it is important that the cross-sectional area of the throttle port 6 is equal to or less than 1/20 of the cross-sectional area of the vertical flow path 7, and is preferably 1/70 to 1/25. By satisfying the above relationship, entrained bubbles generated between the casting port 5 and the throttle port 6 can be floated and separated, and a tire molding die with suppressed bubble defects can be manufactured. Moreover, it is preferable that the vertical flow path 7 is cylindrical so that the flow of the molten metal poured from the casting port 5 can maintain a laminar flow. In FIG. 2, there is one pouring jig 4 attached to the notch opening 3 of the frame 2, but two or more pouring jigs 4 may be attached. FIG. 3 is a horizontal sectional view when four pouring jigs 4 are arranged.

Next, the reason why the sectional area of the throttle port 6 is set to be 1/20 or less of the sectional area of the cylindrical vertical flow path 7 will be described in detail with reference to FIGS. 4 and 5.
FIG. 4 is an explanatory view of bubbles entrained in the molten metal flowing in the pouring jig, and FIG. 5 is an explanatory view showing buoyancy Ff and fluid resistance Fr applied to the bubbles. The molten metal poured into the pouring jig falls into the pouring port, where air is actively entrained and the bubbles 10 are taken into the molten metal. The bubble 10 receives both the fluid resistance Fr and the buoyancy Ff due to the flow velocity v of the vertical flow path 7 in the pouring jig (see FIG. 5). Fr and Ff are given by the following equations.
Fr = 6π · μ · R · v (1)
(Wherein μ is the viscosity coefficient of the molten metal, R is the bubble radius, and v is the molten metal flow velocity)
Ff = (4π / 3) · R ³ · ρ · g (2)
(Where ρ is the density of the molten metal and g is the acceleration of gravity)
As the molten metal flow velocity v increases, the force for pulling the bubbles downward (force for causing the bubbles to flow out to the product portion side) Fr increases, and as the bubble radius R increases, the force for floating and separating the bubbles ( The force (Ff) that attempts to eliminate the bubbles to the casting port side increases.

Here, in order to simplify the description, the diameter of the throttle port 6 of the pouring jig is α (mm), and the diameter of the cylindrical vertical channel 7 upstream of the throttle port 6 is β (mm) (see FIG. 4). ). The molten metal flow velocity v in the pouring jig is substantially constant between the straight cylindrical portions AB, and the flow velocity accelerates from B to C. Therefore, it is considered that the primary bubbles 10 entrained during pouring always flow out from the throttle port 6 when reaching the point B of the cylindrical vertical flow path 7. If this is expressed by the above-mentioned dynamic model, the bubble 10 flows out from the throttle port 6 when Fr> Ff. Therefore, the conditional expression of the radius R of the bubble 10 flowing out from the throttle port 6 is as follows from the expressions (1) and (2).
6π · μ · R · v> (4π / 3) · R ³ · ρ · g (3)
R <√ (4.5ν · v / g) (4)
Here, ν is a kinematic viscosity coefficient of the molten metal.
The molten metal flow velocity v in the cylindrical vertical flow path 7 is determined by the diameter α of the throttle port 6 and the pouring drop H (mm), and the flow velocity at the point C is represented by √ (2 gH). Therefore, the molten metal flow velocity v in the cylindrical vertical flow path 7 is given by the following equation (5).
v = {(α / 2) ² / (β / 2) ² } × √ ( ² gH) (5)
Here, when β = 100 mm, H = 600 mm, and ν = 0.5 mm ² / sec and the value of α is arbitrarily changed, the molten metal flow velocity vmm / sec in the cylindrical vertical flow path 7 is shown. The calculated values of the radius Rmm of the bubbles 10 flowing out from 6 are summarized in Tables 1 and 2 below.

Although the detailed reason is unknown, the value of α is set such that the outflow bubble radius R is 0.2 mm or less from the empirical fact that the amount of bubbles having a radius of 0.2 mm or less is small during the pouring operation. As a result, the bubbles 10 can be floated and separated. Therefore, as can be seen from the above table, when α is 22 mm or less, the outflow bubble radius R can be 0.2 mm or less. That is, the bubble 10 can be floated and separated by setting the cross-sectional area of the throttle port 6 to be equal to or smaller than 1/20 of the cross-sectional area of the cylindrical vertical flow path 7. The conclusion obtained from the above consideration is consistent with an empirical rule that a drawing ratio of about 0.05 (1/20) or less is an area where bubble defects can be minimized in a casting. In addition, although the kinematic viscosity coefficient of the molten metal is calculated as ν = 0.5 mm ² / sec, this is a molten metal with a sufficiently high temperature of the molten metal, and the kinematic viscosity coefficient increased ( It should be noted that the value of the outflow bubble radius R in Tables 1 and 2 above is a larger value in the flow of molten metal (with increased viscosity).

Next, other embodiments of the present invention will be described.
In the present invention, the cross-sectional diameter of the notch opening 3 is preferably the same as or smaller than the cross-sectional diameter of the vertical flow path 7. This makes it possible to further reduce bubble defects.

  Furthermore, a wall 11 is provided on the lower end surface of the bottom of the pouring jig 4 to form a hot water reservoir 12, and a wall 13 is provided on the upper surface of the flow path to the notch opening 3 of the hot water reservoir 12. preferable. FIG. 6 shows an enlarged view of the hot water reservoir 12. Bubbles generated by the molten metal dropped from the throttle port 6 by providing a hot water reservoir 12 at the bottom of the pouring jig 4 and providing a wall 13 on the upper surface of the flow path from the hot water reservoir 12 to the notch opening 3. Can be captured, and bubbles taken into the molten metal that has passed through the throttle port 6 can be removed.

  Moreover, in this invention, as shown in FIG. 7, it is preferable that the sprue 14 formed with the collapsible refractory material extends to the lower end surface of the bottom of the pouring jig 4. By providing a molten metal flow path 15 at a part of the lower end of the sprue 14, the poured molten metal fills the sprue 14 extending through the vertical flow path 7 to the hot water reservoir portion 12, and then the hot water reservoir portion. 12 will be satisfied. Therefore, unlike the case of falling from the throttle port 6, it is possible to obtain a molding die for a tire that does not involve outside air and has few bubble defects. Further, by producing the sprue 14 with a collapsible refractory material, the hot water reservoir 12 is gently connected from the throttle port 6 while accurately regulating the cross-sectional area of the throttle port 6, and the same part at the time of mold disassembly described later. It is possible to easily break the remaining material.

  Moreover, in this invention, it is preferable to affix a heat insulating material in the pouring jig 4. This is to prevent the heat of the pouring from being lost to the pouring jig 4 during pouring and reducing its fluidity.

Next, a method for casting a tire molding die using the casting apparatus of the present invention will be described.
First, the molten metal is poured into the casting port 5 at the top of the pouring jig 4 to fill the molten metal between the mold 1 and the annular frame 2 disposed around the casting mold 1. Next, after the filled molten metal is solidified, the casting body and the pouring jig 4 are broken and separated at the notch opening 3 of the frame body 2 to perform so-called mold breaking. The obtained casting body is processed into a predetermined shape in accordance with conventional usage.

  Further, the poured pouring jig 4 is further separated one by one, and the casting remaining material in the pouring tool 4 is broken and separated at the throttle port 6, and a hot water reservoir 12 provided as desired. The vertical flow path 7 is also divided, and the casting remaining material in the pouring jig 4 is taken out. Furthermore, by removing the heat insulating material on the inner surface of the pouring jig 4 and attaching a new heat insulating material, the pouring jig 4 can be reused and the manufacturing cost can be reduced.

Hereinafter, the present invention will be described based on examples.
Various materials used in this example are as follows.
Mold, pouring jig: G-1 foamed gypsum alloy manufactured by Noritake Jipsum (casting): AC4C (Si alloy: 7%, Mg: 0.4%, remaining A1 aluminum alloy)
Surface plate / pour tool: S45C
Cast frame: FC250
Insulating material: Nippon Steel Chemical Co., Ltd. SC paper 1260 2 mm thick product, inner diameter φ100 (mm), thickness 15 mm SC sleeve 1260

Moreover, the manufacturing conditions of the casting apparatus for each tire mold are as follows.
Mold and pouring jig: 750 g of water was prepared for 1 kg of gypsum powder, and the mixture was stirred at a foaming increase of 75%. A mold produced by casting, curing and reversing into a rubber mold was air-cooled and dried at 200 ° C. for 24 hours, assembled on a surface plate in a ring shape (outer diameter 600 mm, height 200 mm), and used for casting. In addition, the height of the feeder part was 300 mm, and the inner diameter was 100 mm. The inner surface of the pouring jig was covered with a heat insulating material.
Cast frame: The one preheated to 250 ° C. (inner diameter 600 mm) was used until just before casting.
Alloy (casting): After melting at 700 ° C., hydrogen degassing was performed with high-purity Ar gas. The pouring start temperature was 680 ° C.

(Reference example)
Under the above conditions, a tire molding die casting apparatus having a pouring jig connecting portion of the type shown in FIG. 8 was manufactured. This casting apparatus does not have a throttle port in the lower part of the pouring jig, and has a notch opening F (flow) provided in the lower part of the frame body from the vertical channel B (channel cross-sectional area 1969 mm ² : inner diameter 50 mm). It is configured such that the molten metal flows directly into the road cross-sectional area 600 mm ² : 60 × 10 mm. Using this casting apparatus, a tire molding die was manufactured under the above casting conditions. The casting defect occurrence status of the casting thus obtained is as shown in Table 3 below.

  Although some amount of bubble defects and oxide adhesion defects were confirmed, they were within the range where welding repair was possible.

Example 1
A tire molding die casting apparatus having the pouring jig connecting portion of the type shown in FIG. 9 was manufactured under the above conditions, and a tire molding die was manufactured under the above casting conditions. In addition, each flow-path cross-sectional area of this casting apparatus is as showing in following Table 4, and corresponding flow-path cross sections AF are shown in FIG.

このようにして得られた鋳物の鋳造欠陥発生状況は、下記の表５に示す通りである。

The casting defect occurrence status of the casting thus obtained is as shown in Table 5 below.

(Comparative example)
A casting apparatus similar to that in Example 1 was manufactured except that only the flow path cross-sectional area A in Example 1 was changed to φ26 mm (531 mm ² ), and a tire molding die was manufactured under the above casting conditions. The casting defect occurrence state of the casting thus obtained is as shown in Table 6 below.

(Example 2)
A tire molding die casting apparatus having a pouring jig connecting portion of the type shown in FIG. 10 was manufactured under the above conditions, and a tire molding die was manufactured under the above casting conditions. In addition, each flow-path cross-sectional area of this casting apparatus is as showing in following Table 7, and the casting defect generation | occurrence | production situation of casting is as showing in following Table 8. Corresponding channel cross sections A to G are shown in FIG.

  The reason why the oxide adhesion defects were almost zero in Examples 1 and 2 is considered to be that the oxide generated at the initial stage of pouring in the hot water reservoir part floated and separated completely.

  As described above, by using the present invention, it is possible to cast a tire molding die that can prevent bubble defects without requiring complicated and large capital investment and high manufacturing cost.

DESCRIPTION OF SYMBOLS 1 Mold 2 Frame 3 Notch opening 4 Pouring jig 5 Casting port 6 Throttle port 7 Vertical flow path 8 Hot water 9 Surface plate 10 Bubble 11 Wall part 12 Hot water storage part 13 Wall part 14 Sprue 15 Flow path

Claims (4)

A mold for casting a tire mold, an annular frame disposed around the mold, and a detachable attachment to one or a plurality of notch openings provided in a part of the lower portion of the frame In a casting apparatus for a tire molding die provided with a pouring jig,
The pouring jig is composed of an upper casting port, a lower throttle port, and a vertical channel between them, and the sectional area of the throttle port is less than 1/20 of the sectional area of the vertical channel. And a sprue extending from the throttle port to a lower end surface of the bottom portion of the pouring jig.   The tire molding die casting apparatus according to claim 1, wherein a channel cross-sectional diameter of the notch opening is equal to or smaller than the vertical channel cross-sectional diameter.   The wall part was provided in the lower end surface of the bottom part of the said pouring jig, the hot water reservoir part was formed, and the wall part was provided in the upper surface of the flow path to the said notch opening part of this hot water reservoir part. Tire molding mold casting equipment. In a method for casting a tire molding die using the tire molding die casting apparatus according to any one of claims 1 to 3,
After pouring the molten metal into the casting port on the upper part of the pouring jig and filling the molten metal between the mold and the annular frame disposed around the mold, solidifying the filled molten metal, A casting method for a tire molding die, wherein the casting body and the pouring jig are broken and separated at the notch of the frame.

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