JP2000176621A - Vacuum forming device for die casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent formation of casting blow hole by eliminating the entrapment of air at the injecting time of molten metal and also, to enable the continuos formation by always keeping a nozzle body under a prescribed pressure. SOLUTION: A vacuum forming device for die casting, assembled in a die 22, is provided with the nozzle body 11, a nozzle chip 21 fixed to this nozzle body 11 through a heat-insulating ring 12, a valve chip 45 arranged in the shiftable state in the nozzle body 11 and opening/closing the flowing passage of the molten metal formed in the nozzle body 11, a pressure chamber 26 formed between the nozzle body 11 and the valve chip 45 and also, communicated with a pressure source and energizing the valve chip 45 toward the direction closing the flowing passage of the molten metal by raise of the pressure in the inner part and an exhaust valve chip 36 for exhausting the molten metal leaked into this pressure chamber 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum molding apparatus for die casting for vacuum injection molding a molten metal such as a zinc alloy or a magnesium alloy.

[0002]

2. Description of the Related Art FIG. 18 is a sectional view showing the structure of a conventional die-casting molding apparatus. In FIG. 18, the machine nozzle 4 and the mold 7 of the die casting machine are about 10
And the molten metal injection part 4a of the mechanical nozzle 4 is disposed at a position higher than the height of the upper surface 9a of the molten metal 9 (molten metal) in the melting furnace 1. It has a structure to prevent dripping.

[0003] When a product is molded by this die-casting molding apparatus, first, the molten metal 9 melted in the melting furnace 1 is reciprocated in the sleeve 2 by the plunger 3.
And is passed through the mechanical nozzle 4 and injected into the mold 7. The mold 7 includes a fixed mold 7a and a movable mold 7b. The molten metal injected from the machine nozzle 4 passes through a sprue bush 6 of the fixed mold 7a, and a product forming section 8 formed by the fixed mold 7a and the movable mold 7b. 'Supplied to.

At this time, the inside of the mechanical nozzle 4, the inside of the sprue bush 6, and the inside of the product forming section 8 'are filled with air. For this reason, the filled molten metal advances while pushing out the air filled in the product forming portion 8 ′ from the gap of the mold 7. However, since the speed of the molten metal is very high, the molten metal may entrain the air. There is. The air entrained in the molten metal as described above is partially left in the molten metal filled in the product forming section 8 '.

Thereafter, the molten metal supplied to the product forming section 8 'as described above is cooled by the mold 7 and solidified. Then, the movable mold 7b is moved in the direction of arrow A to open the mold 7, and the product section 8a, the runner section 8b,
The molded product 8 integrated with the sprue portion 8c is taken out. The molded article 8 is formed by breaking off the runner section 8b together with the sprue section 8c at the gate section 8d. Here, in the case where the protrusion of the portion where the runner portion 8b is cut off is not allowed, or when high shape accuracy is required, the portion where the runner portion 8b is cut off is subjected to file processing, cutting processing, and the like. Is arranged.

As shown in FIGS. 18 and 20, the sprue bush 6 in the die casting apparatus is cooled by cooling water 31 circulating in the outer peripheral portion, and the sprue portion due to insufficient cooling when the mold 7 is opened. 8c was configured to prevent premature disconnection.

Further, the outer periphery of the mechanical nozzle 4 is heated by the mechanical nozzle heater 5 so that the molten metal does not solidify in the mechanical nozzle. Furthermore, the injection part 4a of this machine nozzle
Was set in a state of being pressed against the mechanical nozzle touch portion 6a of the sprue bush 6 so that the molten metal did not leak.

[0008]

As described above, since the molten metal is injected into the mold 7 at a high speed, air is inevitably entrained in the molten metal, and when a molded product is solidified, a cavity is formed therein. Let me do it. With such a cavity, when the runner portion 8b is cut off or cut as described above, the cavity is exposed on the surface and becomes a hole, and a correct shape cannot be obtained. In addition, when performing the surface treatment, there is a problem that the surface treatment cannot be performed to the depth of the hole. Also, when plating is performed, there is a problem that the plating solution remains in the holes and the corrosion resistance is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has a vacuum inside a mold to eliminate the entrapment of air during injection of molten metal and eliminate the occurrence of cavities. An apparatus is provided.

[0010]

A vacuum forming apparatus for die casting according to claim 1 of the present invention is a vacuum forming apparatus for die casting incorporated in a mold, comprising a nozzle body and an insulating ring mounted on the nozzle body. A nozzle tip fixed through the nozzle tip, a valve tip that is provided to be movable in the nozzle body, and opens and closes a flow path of a molten metal formed in the nozzle body, and between the nozzle body and the valve tip. A pressure chamber that is formed and communicates with a pressure source to urge the valve tip in a direction in which the flow path of the molten metal is closed by increasing the internal pressure; and a discharge valve tip that discharges the molten metal leaking into the pressure chamber. And characterized in that:

According to a second aspect of the present invention, there is provided a vacuum forming apparatus for die-casting, wherein the discharge valve tip is disposed so as to be movable in a nozzle body, and is normally urged by an elastic member to form a discharge passage for molten metal. On the other hand, when the pressure chamber becomes equal to or higher than a predetermined pressure, the discharge passage is opened against the urging pressure of the elastic member,
The molten metal in the pressure chamber is discharged.

According to a third aspect of the present invention, there is provided a vacuum forming apparatus for die-casting, wherein the valve tip and the discharge valve tip are movably supported by a valve guide constituting a part of a nozzle body. A pressure chamber is formed between the guide and the valve tip.

According to a fourth aspect of the present invention, there is provided a vacuum forming apparatus for die-casting, wherein a valve body portion of the discharge valve chip is formed in a conical or spherical shape.

According to a fifth aspect of the present invention, there is provided a vacuum forming apparatus for die casting, wherein a valve seat portion on which a valve body portion of the discharge valve chip is seated is formed in a conical or spherical shape. .

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the vacuum forming apparatus for die casting according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing a state in which a die-casting vacuum forming apparatus according to one embodiment of the present invention is incorporated in a mold 22 and is attached to a die-casting machine. FIG. 2 shows a configuration of the die-casting vacuum forming apparatus shown in FIG. FIG. 3 is an enlarged sectional view of a main part showing a configuration of a nozzle body. Also,
7 and 8 are side views of the vacuum forming apparatus for die casting as viewed from the molten metal outflow side and the molten metal inflow side.

As shown in FIGS. 1 to 3, a substantially cylindrical mounting hole 22d is provided in the fixed die 22a of the mold 22, and the nozzle body 11 is accommodated in the mounting hole 22d. Since the nozzle body 11 is supplied with heat by contact with the mechanical nozzle 4 and is insulated from the mold 22,
It becomes a hot nozzle and can maintain the molten metal in the nozzle body 11 in a molten state. In this embodiment, the nozzle body 11 is provided with a substantially cylindrical nozzle body 41, a nozzle base 42 provided at the end of the nozzle body 11 on the melt inflow side, and provided between the nozzle body 41 and the nozzle base 42. And a valve guide 50. The nozzle body 41 and the nozzle base 42 both have flange portions 41a and 42d on the outer periphery of the opposing portions, and are connected by set screws 44 so as to penetrate the flange portions 41a and 42d and the valve guide 50. A nozzle tip 21 is attached to the end of the nozzle body 41 on the molten metal outflow side. This nozzle tip 21
A flange-shaped tip 21a is formed on the outer periphery of the tip, and a screw 21b is formed on the outer circumference of the other end. The screw 21b is formed inside the end of the nozzle body 41 by a screw 41b. Screwed into the nozzle body 41
It is fixed to. As shown in FIG. 13, the slit groove 32 provided on the end face of the nozzle tip 21 in the molten metal inflow direction allows the nozzle tip 21 to be connected to the nozzle body 41.
This is for inserting a tool when screwing it into. The nozzle body 11 and the nozzle tip 21 having the above configuration are
It is made of heat-resistant steel or a tungsten alloy having a heat conductivity higher than that of the heat-resistant steel, for example, a heat conductivity of 0.3 cal / sec · cm · ° C. or more. A mechanical nozzle touch portion 42c is provided on the outer end surface of the nozzle base 42 on the molten metal inflow side, and an annular concave portion 41c adapted to a heat-resistant gasket described later is provided on the outer end surface of the nozzle body 41 on the molten metal outflow side. Is provided.

As shown in FIGS. 2, 3 and 9 to 12, a valve guide 50 constituting a part of the nozzle body 11 has a cylindrical portion 50a projecting inward of the nozzle body 41, A bottomed hole 50b formed from the end face on the melt inflow side toward the melt outflow direction, a connection hole 50d communicating from the outer peripheral surface to the hole 50b, and a plurality of flow paths 50e provided around the hole 50b. And a through hole 50f through which the aforementioned set screw 44 passes. This valve guide 50
The sliding portion 45b of the valve chip 45 that is movable along the direction in which the molten metal flows is slidably fitted in the hole 50b. A pressure chamber 26 is formed in the hole 50b by the valve tip 45 and the valve guide 50, and the pressure in the pressure chamber 26 causes the valve tip 4 to move.
5 slides toward the nozzle base 42. A conical contact portion 45a forming a valve body is provided at a portion of the end of the valve chip 45 facing the nozzle base 42. On the other hand, a portion of the nozzle base 42 facing the contact portion 45a of the valve chip 45 is provided with a conical contact portion 42a forming a valve seat. These contact portions 45a, 4
Reference numeral 2a denotes a close contact when the sliding portion 45b slides due to the pressure of the pressure chamber 26, and the close contact can shut off the flow path 42b of the nozzle base 42. on the other hand,
Compressed air is supplied to the pressure chamber 26 from a low-pressure source 28 or a high-pressure source 30 via a connection pipe 27, and the pressure inside the pressure chamber 26 is increased. The connection pipe 27 is fixed so as to communicate with the connection hole 50d of the valve guide 50, and a heat-resistant gasket 29 is provided between the valve guide 50 and the connection pipe 27 to prevent leakage of compressed air. ing.

On the other hand, as shown in FIG. 9, a partition wall 5 for partitioning the hole 50b of the valve guide 50 from the cylindrical portion 50a.
At 0k, a small through hole 50i is opened.
Is closed by a discharge valve tip 36 arranged in the cylindrical portion 50. The discharge valve chip 36 is normally pressed toward the through hole 50i by the coil spring 37, and the distal end portion 36a as a valve body formed in a conical shape has a through hole 50i.
Is in contact with a conical surface 50m forming a valve seat formed around the periphery of the valve seat. The coil spring 37 is compressed and accommodated in the cylindrical portion 50a by a spring receiving screw 38.

The nozzle tip 21 includes a heat insulating ring 12
And is fixed to the nozzle body 41 via. The heat insulating ring 12 is made of a material having good heat resistance and low thermal conductivity, such as ceramics, and a material having mechanical strength enough to withstand screwing and pressing. This insulation ring 12
The tip 21a of the nozzle tip 21
Is provided with an annular concave portion 12a. As shown in FIG. 2, the heat insulating ring 12
When the nozzle tip 21 penetrating through the nozzle body 41 is fixed to the nozzle body 41, the nozzle tip 21 is sandwiched and fixed between the front end portion 21 a and the end face of the nozzle body 41. This insulating ring 12
The outer diameter of the mounting hole 22d is such that it can be clearance-fitted into the heat insulating ring fitting portion 22ab at the end of the melt hole on the melt outflow side.

The heat-resistant gaskets 14, 43 and 25 are provided between the heat insulating ring 12 and the nozzle body 41, and the nozzle body 4 is provided.
1 and the valve guide 50, and between the valve guide 50 and the nozzle base 42, respectively, to prevent the molten metal from flowing out or the air from flowing in between them. The heat-resistant gaskets 14, 43, and 25 are made of a soft material such as gold or copper having some heat resistance, a metal O-ring, a metal C-ring, and a metal U-ring made of stainless steel, inconel, hastelloy, or the like. With the recess 41c of the nozzle body 41 and the valve guide 50
Are small enough to fit in the recesses 50g and 50h (FIG. 9), and are slightly pressed in a non-pressed state.
c, 50 g, and 50 h. This heat-resistant gasket 14, 43, 25
As described above, as described above, the heat insulating ring 12
1 and when the nozzle base 42 and the valve guide 50 are fixed to the nozzle body 41, respectively, compressed between them. The heat-resistant gaskets 14, 43, and 25 compressed as described above use the molten metal as the nozzle body 4.
It acts so as to prevent the gas from flowing out between the mold 22 and the nozzle body 11 through the gap between the heat sink 1 and the heat insulating ring 12 or the gap between the nozzle body 41 or the nozzle base 42 and the valve guide 50. Further, it also acts to maintain the airtightness in the nozzle body 11. Note that the heat-resistant gaskets 29 provided between the valve guide 50 and the connecting pipe 27 also include these heat-resistant gaskets 14, 43,
25 is made of the same material and configuration.

The O-ring 47 is made of a heat-resistant material such as fluorine rubber or silicon rubber, and is housed in an annular groove 22aa provided on the inner periphery of the heat insulating ring fitting portion 22ab of the fixed mold 22a. . This O-ring 47
It has mechanical elasticity in the radial direction and has a fixed mold 22.
a and the heat insulating ring 12 are compressed in the radial direction to prevent air from flowing into the gap between the fixed mold 22a and the heat insulating ring 12 therebetween.

The guide rings 23 and 24 have heat resistance,
The guide ring 23 is fitted on the nozzle main body 11 so as to sandwich the flange portions 41a and 42d, and is positioned by being locked to the step in the mounting hole 22d. This is to support the nozzle body 11 in contact with it and position the mechanical nozzle touch portion 42c at an appropriate position.

The back plate 15 is fixed to the end face of the fixed die 22a with screws 16 in order to prevent the nozzle body 11 and the guide rings 23 and 24 from dropping out of the mounting holes 22d. In this back plate 15,
A hole slightly larger than the outer diameter of the mechanical nozzle touch portion 42c of the nozzle base 42 is provided, and the mechanical nozzle touch portion 42c is set to slightly protrude from this hole.

The vacuum source 20 (FIG. 1) sucks air in the product forming portion 10 ′ of the mold 22 to reduce the pressure to make a vacuum or a state close to a vacuum. The movable mold 22b is provided with an air escape groove 22ba and air escape holes 22bb, 22bc communicating with the product forming section 10 '. The air escape groove 22ba and the air escape holes 22bb and 22bc are configured to allow air to flow therethrough. When the air escape hole 22bc is connected to the vacuum source 20, the air escape groove 22ba and the air escape holes 22bb The air in the product forming section 10 ′ is sucked by the vacuum source 20 through the 22 bc. Further, the movable die 22b is provided with a shut-off pin 48 for separating the product forming portion 10 'from the air escape groove 22ba. The shut-off pin 48 is slidable in the directions of arrows B and C in FIG. 1 (the left-right direction in FIG. 2). It can communicate with or block the groove 22ba.

In the die-casting vacuum forming apparatus having the above structure, when the die-casting is started, first, the mold 22 is closed, and the fixed mold 22a and the movable mold 22b are brought into close contact with each other, and the state shown in FIG. 4 is obtained. In this state, the shut-off pin 48 is drawn out of the air escape groove 22ba as shown in FIG. 4, so that when the air is sucked by the vacuum source 20, the inside of the nozzle body 11 and the mold 22 The product forming section 10 'is decompressed and almost in a vacuum state. Thereafter, when the blocking pin 48 moves in the direction of arrow B, as shown in FIG. 2 or 5, the air escape groove 22ba is blocked,
The inside of the nozzle body 11 and the product forming section 10 'of the mold 22 are kept in a vacuum state.

In the state shown in FIG.
The sealing when the pressure is reduced by the vacuum source 20 connected to the 2bc is performed by the O-ring 47 and the heat-resistant gaskets 14, 43, 2
5 and the valve tip 45 and the nozzle base 42 are kept in close contact. Although there is a slight flow of air from the sliding portion between the valve guide 50 and the valve tip 45, the degree of vacuum can be substantially maintained by making the gap in this portion minute.

At this time, the valve chip 45 is
When the pressure in the pressure chamber 26 is increased by the compressed air from the low pressure source 28, the pressure chamber 26 slides rightward in FIG. 4, and the contact portion 45 a comes into close contact with the contact portion 42 a of the nozzle base 42. 42, closing the flow path 42b. The pressure of the pressure chamber 26 is set to a magnitude that keeps the valve tip 45 in close contact with the nozzle base 42 without moving even when the inside of the nozzle main body 11 is in a vacuum state. When the air escape groove 22ba is shut off by the shut-off pin 48, the connecting pipe 27 and the low pressure source 2
The connection with the pressure chamber 8 is also released, and the pressure chamber 26 is connected to the atmosphere to be depressurized. For this reason, the pressing of the valve tip 45 in the direction of the nozzle base 42 is released. After the connection between the connection pipe 27 and the low-pressure source 28 is released, the connection pipe 27 may be connected to the vacuum source 20 to make the inside of the pressure chamber 26 vacuum.

In this state, when the molten metal is pressurized by the plunger 3 of the die casting machine, the molten metal is injected from the machine nozzle 4 to the nozzle body 11. The valve tip 45 is pressed by the injection pressure at this time and moves leftward in FIG. 5 to open the channel 42 b of the nozzle base 42. As a result, the molten metal flows into the nozzle body 11, flows through the flow path 50 e of the valve guide 50, and flows from the nozzle tip 21 into the product forming section 10 ′. At this time, since the inside of the nozzle body 11 and the product forming portion 10 'of the mold 22 are substantially in a vacuum state, the molten metal is filled into the product forming portion 10' without involving air. Further, since the nozzle body 11 is a hot nozzle, the molten metal in the nozzle body 11 can be kept in a molten state, and the temperature drop of the molten metal due to the sprue bush as in the related art is eliminated. As a result, mold 2
It becomes easy to fill the finely shaped portion and the extremely thin portion of the product forming portion 10 'with the molten metal, and the shortage of the filling is eliminated. further,
In this embodiment, a heat-resistant gasket or an O-ring is provided between the nozzle body 11 and the mold 22 to maintain airtightness and prevent the molten metal from leaking from the nozzle body 11 into the mold 22. From the nozzle body 11 to the mold 22
Heat leakage to the nozzle body 11 and the mold 22 are reliably insulated, and the nozzle body 11 can be maintained at a temperature suitable for die casting.

As described above, when the molten metal flows and the valve tip 45 moves leftward in FIG.
5c is in close contact with the contact portion 50c of the valve guide 50. Therefore, the molten metal flows between the contact portion 45a of the valve tip 45 and the contact portion 42a of the nozzle base 42 and flows into the valve guide 50.
Due to the close contact of 5 c and 50 c, there is no flow between the valve guide 50 and the sliding portion 45 b of the valve chip 45. Further, the discharge valve chip 36 is pressed by the coil spring 37 and closes the through hole 50i shown in FIG.

Thereafter, when the injection of the molten metal is stopped and the injection of the molten metal from the mechanical nozzle 4 is completed, the connecting pipe 27 is connected to the low pressure source 28 again, compressed air is sent into the pressure chamber 26 and the valve tip 45 Moves rightward in the figure as shown in FIG. Then, the contact portion 45a is again brought into close contact with the contact portion 42a of the nozzle base 42 to seal the flow passage 42a.
Close b.

On the other hand, the molten metal filled in the mold 22 is cooled and solidified there. As described above, since the molten metal does not flow in the vacuum and entrain the air, almost no cavities are generated inside the molded product. At this time,
The molten metal at the tip 21a of the nozzle tip 21 is also cooled and solidified. Thereafter, the movable die 22b moves in the direction of the arrow A (FIG. 1) to open the die 22, thereby integrating the product part 10a, the runner part 10b, and the gate part 10d as shown in FIGS. The molded article 10 is taken out. At this time, since the nozzle body 11 is heated by the heat from the mechanical nozzle, the sprue portion 8c is not formed as in the conventional molded article 8 as shown in FIG.

As described above, when the molded article 10 is taken out, the temperature of the tip 21a of the nozzle tip 21 is rapidly restored to an appropriate temperature at which molding is possible by the heat of the central part 11b of the nozzle body 11. If a material having good thermal conductivity is used for the nozzle body 11, it is possible to recover the temperature more rapidly.

At the time of the die casting, the molten metal tends to flow between the heat insulating ring 12 and the nozzle body 11.
The heat-resistant gasket 14 includes the heat insulating ring 12 and the nozzle body 11.
Is sealed between the nozzle body 11 and the fixed mold 22a, so that the molten metal does not flow between the nozzle body 11 and the fixed mold 22a.

The temperature of the fixed mold 22a is much lower than the temperature of the molten metal.
Gap 17 between insulating ring fitting portion 22ab of 2a (FIG. 2)
When is small, the molten metal solidifies before flowing into the interior, so that the molten metal does not flow. In the present embodiment, the product forming portion 10 ′ of the inside of the nozzle body 11 and the mold 22.
An O-ring 47 is provided between the heat insulating ring 12 and the fixed mold 22a to more surely maintain the vacuum state. Also,
The difference between the thermal expansion coefficient of the fixed die 22a and the thermal expansion coefficient of the nozzle main body 11 is that the heat insulating ring 12 has a heat insulating ring fitting portion 22a of the fixed die 22a.
It is absorbed by sliding with respect to b, but at this time, the sealed state is maintained by the O-ring 47.

After the molded article 10 is taken out, the connection of the connecting pipe 27 is switched from the low pressure source 28 to the high pressure source 30 as shown in FIG. The discharge valve 36 is pushed by this high pressure, and the through hole 50i of the partition wall 50k is formed.
Is opened, and the molten metal leaked into the pressure chamber 26 is discharged. This discharging operation does not need to be performed for each molding cycle.
It may be performed at a time when the molten metal fills the pressure chamber 26. Thereafter, the connection between the connecting pipe 27 and the high-pressure source 30 is released, and the connecting pipe 27 and the low-pressure source 28 are connected again to start the next molding cycle.

The gas supplied from the low-pressure source 28 and the high-pressure source 30 may be not only air but also a reducing gas or the like capable of preventing metal oxidation.

In the above-described die casting, when the molten metal is injected into the mold 22, the connection between the pressure source 28 and the connection pipe 27 is released, and the pressure chamber 26 is at atmospheric pressure. , Regardless of whether it is during molten metal injection,
The pressure chamber 26 may be pressurized while the pressure source 28 and the connection pipe 27 are always connected. In this case, even if the pressure in the pressure chamber 26 becomes a vacuum state in the nozzle body 11 and the product forming part 10 ′, the contact part 45 a
And the contact portion 42a of the nozzle base 42 can be kept in close contact with each other.
Is set to such a size that it can move to the left as shown in FIG. Further, in this case, when the injection of the molten metal is completed, the nozzle tip 45 moves rightward by the pressure of the pressure chamber 26, and the contact portion 45a and the nozzle base 4 are moved.
The second contact portions 42a are brought into close contact with each other to return to the initial state.

FIG. 16 shows a second embodiment of the present invention, which has the same structure as that of the previous embodiment except that the distal end portion 36a of the discharge valve chip 36 is formed in a spherical shape. Description is omitted. This tip portion 36a is a partition 5
The close contact with the curved surface 50m of the through hole 50i opened at 0k prevents outflow of air from the pressure chamber 26 into the nozzle body 11 when the connecting pipe 27 is connected to the low pressure source 28. By forming the distal end portion 36a of the discharge valve chip 36 into a spherical shape, the discharge valve chip 3
Even if the discharge valve chip 36 is in contact with the partition 50k in a state where the discharge valve tip 36 is inclined due to play in the sliding portion between the valve guide 6 and the valve guide 50, the through hole 50i of the partition 50k can be reliably closed.

FIG. 17 shows a third embodiment of the present invention. In this embodiment, the discharge valve chip 36 is replaced with a sphere, and the through hole 5
The periphery of 0i is formed as a spherical surface 50m. This spherical surface 50m
Is a spherical surface having a radius equal to or slightly larger than the radius of the spherical surface of the discharge valve chip 36, and ensures contact with the spherical discharge valve chip 36. In this embodiment, a metal C-ring 55 is provided instead of the O-ring fitted on the outer circumference of the heat insulating ring 12. The metal C ring 55 is made of stainless steel, Inconel, Hastelloy, or the like, and is positioned by a flange portion 12b provided on the outer periphery of the heat insulating ring 12. Since the metal C-ring 52 can further increase the heat resistance as compared with the O-ring 47 made of heat-resistant rubber or the like, even if the temperature of the molten metal is high and the temperature of the heat insulating ring 12 is high, the metal C-ring 52 can be reliably sealed. Things. Further, in this embodiment, a connecting spacer 54 made of a material having a low thermal conductivity such as ceramics is interposed between the valve guide 50 and the connecting pipe 27 to reduce heat outflow from the nozzle body 11 to the connecting pipe 27. I have. In this case, a further effect can be expected by setting the material of the connection pipe 27 to 18-8 stainless steel having a lower thermal conductivity than heat-resistant steel. In addition, the leakage of the compressed air is prevented by the heat-resistant gaskets 29 and 52 disposed before and after the connecting spacer 54.

[0040]

As described above, according to the vacuum forming apparatus for die casting according to the present invention, the product forming portion of the mold and the nozzle body can be sealed and brought into a vacuum state.
The inflowing molten metal does not entrain the air, thereby preventing the occurrence of cavities in the molded product. For this reason, it is possible to eliminate shape defects and surface treatment defects caused by the occurrence of cavities, and it is possible to significantly improve the quality of products. Also,
According to the present invention, the molten metal that has leaked into the pressure chamber of the nozzle body can be discharged during the molding cycle, so that the pressure chamber is always maintained at a predetermined pressure and continuous molding can be performed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state in which a vacuum molding apparatus for die casting according to the present invention is incorporated in a mold and attached to a die casting machine.

FIG. 2 is a sectional view showing a first embodiment of a vacuum forming apparatus for die casting.

FIG. 3 is an enlarged sectional view of a main part of the vacuum forming apparatus for die casting shown in FIG. 2;

FIG. 4 is a sectional view showing a state when the inside of the vacuum forming apparatus is evacuated.

FIG. 5 is a sectional view showing a state when a molten metal is injected into the vacuum forming apparatus.

FIG. 6 is a cross-sectional view of the vacuum forming apparatus showing a state when a discharge valve chip is operated.

FIG. 7 is a side view on the melt outflow side of the vacuum forming apparatus.

FIG. 8 is a side view of the melt forming side of the vacuum forming apparatus.

FIG. 9 is an enlarged sectional view of a valve guide of the vacuum forming apparatus.

FIG. 10 is a side view of the valve guide on the molten metal inflow side.

FIG. 11 is a plan view of a nozzle guide.

FIG. 12 is a side view of the nozzle guide on the molten metal injection side.

FIG. 13 is a side view of the nozzle tip on the molten metal inflow side.

FIG. 14 is a side view of a molded product using the vacuum molding device.

FIG. 15 is a front view of the molded product shown in FIG.

FIG. 16 is a sectional view of a vacuum forming apparatus for die casting according to a second embodiment of the present invention.

FIG. 17 is a sectional view of a vacuum forming apparatus for die casting according to a third embodiment of the present invention.

FIG. 18 is a sectional view showing an example of a conventional vacuum forming apparatus for die casting.

FIG. 19 is a side view of a molded article formed by a conventional vacuum forming apparatus.

FIG. 20 is a sectional view of a sprue bush used in a conventional vacuum forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Nozzle main body 12 Heat insulation ring 21 Nozzle tip 22 Mold 26 Pressure chamber 28 Low pressure source 30 High pressure source 36 Discharge valve tip 36a Tip part (valve body part) 37 Coil spring (elastic member) 42b Flow path 45 Valve tip 45a Contact part ( Valve part) 50 Valve guide 50i Through hole (discharge passage)

Claims (5)

[Claims] 1. A vacuum forming apparatus for die casting incorporated in a mold, comprising: a nozzle body; a nozzle tip fixed to the nozzle body via a heat insulating ring; A valve chip provided for opening and closing a flow path of the molten metal formed in the nozzle body; and a valve chip formed between the nozzle body and the valve chip and communicating with a pressure source to increase the internal pressure. A pressure chamber for urging the molten metal in a direction in which the flow path of the molten metal closes, and a discharge valve tip for discharging the molten metal leaking into the pressure chamber. 2. The discharge valve tip is movably disposed within the nozzle body, and is normally urged by an elastic member to close a discharge passage of the molten metal. The vacuum forming apparatus for die casting according to claim 1, wherein the discharge passage is opened against the urging pressure to discharge the molten metal in the pressure chamber. 3. The valve tip and the discharge valve tip are movably supported by a valve guide constituting a part of a nozzle body, and a pressure chamber is formed between the valve guide and the valve tip. The vacuum forming apparatus for die casting according to claim 1 or 2, wherein: 4. The vacuum forming apparatus for die-casting according to claim 1, wherein the valve body of the discharge valve tip is formed in a conical surface or a spherical shape. 5. The vacuum forming apparatus for die casting according to claim 1, wherein a valve seat portion on which a valve body portion of the discharge valve chip is seated is formed in a conical or spherical shape. .