JPH01313170A - Vacuum die casting machine - Google Patents

Abstract

PURPOSE:To inject molten metal into a casting cavity by the air permeated through the clearance between a plunger tip and a cylinder sleeve to prevent the quality of a die cast article from being deteriorated by providing the air- tight sealing member coming in close contact with the inner peripheral surface of the cylinder sleeve on the outer peripheral surface of the plunger tip for injecting the molten metal in a vacuum die casting machine. CONSTITUTION:The molten Al alloy, etc., in the cylinder sleeve 3 are cast under pressure through a runner 7 into the casting cavity 1 which is composed of a fixed die 2A and a movable die 2B and is provided with a vacuum vent 8. An annular groove 10A is provided on the outer peripheral surface of the end of the plunger tip 10 for extruding molten Al set on the tip of a piston 6 and a ringed air-tight sealing member 11 made of elastic material is fitted in the groove to keep the air-tightness between the inner peripheral surface of the injection cylinder sleeve 3 and the plunger tip. Since air does not come from the clearance between the plunger tip 10 and the cylinder sleeve 3, it is possible to prevent the deterioration of appearance and quality based on the injection of the molten Al alloy 3A into the cavity 1 and the generation of blow holes in the die cast article by permeation and expansion of the air.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a vacuum die casting device that performs die casting under a relatively high vacuum inside a cavity, and is capable of producing large quantities of precision castings of aluminum alloy. do,
For example, it is often used in the production of component parts for automobiles, motorcycles, etc.

[Conventional technology]

A vacuum die-casting apparatus that has been commonly used in the past will be explained with reference to FIG.

A cavity 1 is composed of a fixed mold 2A and a movable mold 2B. Reference numeral 3 denotes a cylindrical injection cylinder sleeve, one end (left side in the figure) is connected to the cavity I via a runner 7, and a pouring hole 4 is bored near the outer periphery of the other end.

Further, a plunger tip 5 is slidably disposed within the injection cylinder sleeve 3, and the plunger tip 5 is integrally connected to an injection cylinder (not shown) by a piston 6.

Further, a vacuum vent 8 is opened in the cavity 1, and the vacuum vent 8 is connected to a vacuum source such as a vacuum pump (not shown).

Then, with the plunger tip 5 opening the pouring hole 4, the molten metal is poured into the injection cylinder sleeve 3 through the pouring hole 4, and then the piston 6 pressed by the injection cylinder The molten metal in the injection cylinder sleeve 3 is injected into the cavity 1 at a low speed by the jar tip 5, and then injected at a high speed, and during such injection, the inside of the cavity 1 is evacuated by the vacuum pressure introduced into the cavity 1 from the vacuum vent 8. hold and cast,
After the molten metal solidifies in the cavity 1, the mold is opened and the product is taken out.

[Problem to be solved by the invention]

Such conventional vacuum die casting equipment has the following problems. The molten metal in the injection cylinder sleeve 3 is not yet injected into the cavity 1 during low-speed injection by the plunger tip 5, but instead fills the runner 7 including the injection cylinder sleeve 3. A phenomenon occurs in which the molten metal in the injection cylinder sleeve 3 is ejected into the cavity 1 before injection into the cavity 1 is started. (This jet is shown as A in Figure 1.)
According to this, in addition to creating hot spots in the product and impairing its appearance quality, the product was also dotted with numerous large and small blowholes, which deteriorated airtightness. In normal die casting that does not use vacuum die casting, this jetting phenomenon occurs due to causes such as excessive amount of hot water being supplied, slow setting of plunger tip speed, and slow setting of the high speed switching position, causing the molten metal to pass through the runner before high speed injection. Then, it slowly enters the cavity, and a part of it solidifies, creating a hot water barrier. It is completely different from the so-called "sagging phenomenon", and is a peculiar phenomenon in vacuum die casting, and is characterized by entering the cavity in the form of a violent jet or droplet with such force that it reaches the top of the cavity.

This jetting phenomenon becomes more likely to occur as the degree of vacuum in the cavity and injection cylinder sleeve increases, and to prevent this, the degree of vacuum is lowered, or the injection resistance at the runner gate section is increased to prevent casting. Sometimes.

However, these measures are unavoidable measures to prevent the ejection of water into the cavity, and they reduce the original effect of vacuum die casting.

[Means for Solving the Problems] [Operation] The vacuum die casting device of the present invention is capable of forming a cavity without reducing the degree of vacuum in the cavity and the injection cylinder sleeve, or without increasing the injection resistance at the runner gate. The purpose of the present invention is to provide a vacuum die-casting device that prevents the phenomenon of inward jetting.In order to achieve the above-mentioned purpose, an airtight sealing member is disposed in the gap between the plunger tip and the injection cylinder sleeve. This prevents air from flowing into the injection cylinder sleeve that stores the molten metal through the gap between the injection cylinder sleeve and the injection cylinder sleeve.

According to this, the force of the air flowing in from the gap and moving into the cavity with body expansion under reduced pressure in the injection cylinder sleeve causes the molten metal in the injection cylinder sleeve to be blown away from the runner into the cavity. This could have been prevented.

〔Example〕

First, the inventor conducted an experiment to clarify the mechanism by which an undesirable jetting phenomenon into the cavity occurs before high-speed injection in a vacuum die-casting device.

In the experiment, the cavity and injection cylinder sleeve were first evacuated and the pressure was varied from atmospheric pressure to 50 Torr. As a result, it was found that when the pressure in the cavity and the injection cylinder sleeve decreased below a certain level, a jet suddenly began to flow into the cavity, indicating that a jet flow limit pressure existed. Under pressure conditions below this critical pressure, a gushing phenomenon into the cavity always occurred, and under pressure conditions higher than this, no gushing phenomenon was observed, and the molten metal surface was quiet. This limit pressure varies depending on conditions such as the amount of hot water, the temperature of the hot water, the tip clearance between the plunger tip and the injection cylinder sleeve, the diameter of the injection cylinder sleeve, the shape of the runner, etc., but in this experiment it was 400 to 550 Torr.

Next, an experiment was conducted by placing an annular airtight seal member in the gap between the outer periphery of the plunger tip and the injection cylinder sleeve. As a result, even if the pressure in the cavity and the injection cylinder sleeve was changed from atmospheric pressure to 50 Torr, the molten metal in the injection cylinder sleeve did not spout out into the cavity.

That is, it has been found that by eliminating the gap between the plunger tip and the injection cylinder sleeve, the outflow phenomenon can be prevented from occurring.

From the above, the cause of the molten metal spouting into the cavity in the injection cylinder sleeve is the inside and outside of the injection cylinder sleeve (the runner side and the pouring side), which are divided by the plunger tip placed inside the injection cylinder sleeve. Due to the differential pressure between the injection cylinder sleeve and the plunger tip (generally, the gap between the plunger tip and the injection cylinder sleeve is about 50L), the injection into the chamber on the runner side of the injection cylinder sleeve. Air flows into the injection cylinder sleeve on the runner side, and under reduced pressure in the injection cylinder sleeve on the runner side, the air rapidly moves into the cavity with the vacuum vent without volume expansion.

It was discovered that the cause of this problem was that the force generated during such movement caused the molten metal filled in the injection cylinder sleeve to be blown up into the cavity at once.

This shows that by preventing air from flowing into the injection cylinder sleeve from the outside of the injection cylinder sleeve, the phenomenon of molten metal spouting into the cavity can be prevented.

Hereinafter, one embodiment of the vacuum die casting apparatus according to the present invention will be described with reference to FIG. Components having the same structure as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

lO is slidably disposed within the injection cylinder sleeve 3 and is attached to the piston 6 in the injection cylinder (not shown).
The plunger chip 10 is connected to the plunger chip 10 through a ring, and an annular groove 10A is carved on the outer circumference of the plunger chip 10. An airtight seal member 11 is disposed in this annular groove lOA, and the airtight seal member 11 airtightly seals the gap between the outer periphery of the plunger tip 10 and the inner periphery of the injection cylinder sleeve 3. It is something that will be done.

Next, its effect will be explained.

First, prior to injection, the plunger tip 10 is moved rightward in the figure by the piston 6 to bring the pouring hole 4 and the injection cylinder sleeve 3 into communication. According to this, molten metal is stored in the injection cylinder sleeve 3 from the pouring hole 4. The amount of molten metal stored must be set appropriately.

Next, the plunger tip 10 is moved to the left in the figure by the piston 6. According to this, the outer periphery of the plunger tip 10 closes the pouring hole 4, and the airtight seal member 11 closes the plunger tip 10. The gap between the outer periphery of the tip 10 and the inner periphery of the injection cylinder sleeve 3 is hermetically sealed.

The position where this plunger tip 10 closes the pouring hole 4 becomes the starting point for low-speed injection, and from then on, the plunger tip 1
The leftward movement of O by the piston 6 causes the end of low-speed injection and progresses to high-speed injection.Generally, at the end of low-speed injection, the injection cylinder sleeve 3 including the runner 7 is filled with molten metal. The cavity 1 is filled with molten metal by the next high-speed injection.

At least at the start of low-speed injection, vacuum pressure is introduced into the cavity 1 from the vacuum vent 8, and the interior of the cavity 1 is maintained at a vacuum pressure lower than atmospheric pressure.

According to the vacuum die casting apparatus of the present invention, when the plunger tip 10 moves at least inside the injection cylinder sleeve 3 for low-speed injection, the airtight seal member 11 seals the plunger tip 10 and the injection cylinder sleeve 3. Since the gap with the injection cylinder sleeve 3 is airtightly sealed, the molten metal inside the plunger tip IO (on the left side in the figure) can be stored through the gap.
Air does not flow into A (runner 7 side) from the outer injection cylinder sleeve 3B (molten metal pouring hole 4 side).

Therefore, as is clear from the above experimental results, the molten metal in the injection cylinder sleeve is blown up from the runner 7 into the cavity 1 by the force that moves into the cavity with the volume expansion of air under reduced pressure in the injection cylinder sleeve. This phenomenon was completely prevented for 1 hour.

Although the airtight sealing member in the above embodiment is arranged as a single piece, a plurality of annular grooves lOA are carved on the outer periphery of the plunger tip 10. If an airtight seal member is arranged in each annular groove 10A, the sealing effect can be further improved and air inflow prevention can be improved.

In addition, this airtight sealing member is desirably made of an i-type material in view of the insertion work into the annular groove 10A and the sealing effect. Since the temperature rises to a certain point, it is desirable to use a heat-resistant material, and the cross-sectional shape of the airtight seal member 11 may be either circular or rectangular.

Moreover, what is shown in FIG. 3 shows another embodiment of the airtight seal member. The airtight seal member includes a first seal member 20 and a second seal member 21, and the first seal member 20 is disposed between the outer periphery of the piston 6 and the inner periphery of the injection cylinder sleeve 3 near the right end.

The second sealing member 21 is for preventing air from flowing into the injection sleeve 3 from around the pouring hole 4 when the plunger tip 5 closes the pouring hole 4. Specifically, 22 is a cylindrical closing sleeve slidably disposed around the outer periphery of the injection cylinder sleeve 3;
This closing sleeve 22 is fixedly provided on the piston 6.
The clip 23 is backed up by a spring S.

Then, when the plunger tip 5 closes the pouring hole 4, the closing sleeve 22 closes the outer periphery of the pouring hole 4, and the plunger tip 5 is used for injection molding. Even if it moves to the left, the closing sleeve 22 comes into contact with a stop protrusion 3A protruding from the outer periphery of the injection cylinder sleeve 3 to prevent it from moving to the left.

Note that 24A and 24B are seal rings arranged between the outer periphery of the injection cylinder sleeve 3 before and after the injection hole 4 and the inner periphery of the closing sleeve 22.

According to such a closing seal member, the plunger tip 5
moves to the right to open the pouring hole 4, the closing sleeve 22 as the second sealing member 21 closes with the E clip 23.
It moves to the right synchronously with the piston 6 against the force of the spring S to open the pouring hole 4. Therefore, molten metal can be supplied into the injection cylinder sleeve 3 through the pouring hole 4.

Next, when the plunger tip 5 is moved to the left and the pouring hole 4 is closed by the plunger tip 5, the first closing sleeve 22 is also pressed leftward by the spring S and moved to the left synchronously with the plunger tip 5. to close the pouring hole 4. At this time, the seal rings 24A and 24B can completely block the inflow of air from the pouring hole 4 into the injection cylinder sleeve, and the gap between the piston 6 and the injection cylinder sleeve 3 is also closed by the first seal member 20. .

Next, the plunger tip 5 further starts to move to the left for low-speed injection, but as described above, in this state, the first seal member 20 and the second seal member 21 prevent air from flowing into the injection cylinder sleeve 3. This completely prevented the outflow phenomenon in the cavity 1 similar to that in the first embodiment.

Incidentally, the plunger tip 5 and the piston 6 move to the left after closing the pouring hole 4 for injection, but the second sealing member 2
1, the closing sleeve 22 has its tip 22A in contact with the stopping protrusion 3A, and after that the spring 24 contracts, so this problem does not arise and the pouring hole 4 can still be reliably kept closed.

〔Effect of the invention〕

As described above, according to the vacuum die-casting apparatus of the present invention, it is possible to elucidate the mechanism by which the phenomenon of molten metal spouting into the cavity in vacuum die-casting is caused by air flowing into the injection cylinder sleeve from the outside. This was the first of its kind to produce vacuum die casting, which has no inherent blowholes, has excellent airtightness, and has good casting surface quality, without lowering the degree of vacuum inside the cavity or increasing the injection resistance of the runner. This is completely unnecessary in normal die casting that does not use a vacuum, and is useful only in vacuum die casting, and its industrial effects are enormous.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the main parts of a conventional vacuum die-casting device.
FIG. 2 is a cross-sectional view of a main part showing a vacuum die-casting apparatus according to the present invention, and FIG. 3 is a cross-sectional view of a main part showing another embodiment of a vacuum die-casting apparatus according to the present invention. 1... Cavity 3, Injection cylinder sleeve 4, Molten pouring hole 6, Piston 7
91. Runner 8, Vacuum vent 1
0, , Plunger tip IOA , , Annular groove 11. ,,,hermetic sealing member 20, ,first sealing member 21. ,,,Second
Seal member 22, ..., occlusion sleeve 24. ,,,
In the spring? 1 B Procedural amendment August 1988 Display of 1m per day 1988 Patent application No. 144495 2 Title of invention Vacuum die casting device 3 Relationship to the case of the person making the amendment Patent applicant address Shinjuku-ku, Tokyo 4-3-17, Shinjuku Name: Keihin Seiki Seisakusho Co., Ltd. Representative: Takeo Iwai 4 Agent: 220 Address: 2-11-2-5 Takashima, Nishi-ku, Yokohama Date of amendment order: Issued by 6. Column 7 of "Detailed Description of the Invention" Contents of Amendment 1, "Goose sleeve inside, φ, fist lowered" in page 5, lines 12-13 of the specification has been changed to indicate the degree of vacuum in the goose sleeve. The higher the temperature, the more likely it is to occur, and in order to prevent this, the degree of vacuum must be lowered.'' 2. In the second line of page 6 of the specification, "Qi and...fist/decompression level is lowered" is corrected to "Qi and the vacuum level in the injection cylinder sleeve is lowered." 3. "Linder sleeve φ" on page 6, line 13 of the specification
...accompanied by a fist" is corrected to "accompanied by volume expansion and aggregation under vacuum in the cylinder sleeve." 4. In the 4th line of page 7 of the specification, "The inside of the leave is evacuated and the vacuum pressure is 50 degrees" to be corrected. 5. In the 6th line of page 7 of the specification, "Chee and ... pressure are constant" is corrected to "Chee and the vacuum pressure in the injection cylinder sleeve are constant." 6. In the specifications page 8, lines 18 to 19, "Rapidly to the exit cylinder φ, war, etc." is changed to "The molten metal in the sleeve chamber undergoes volume expansion and aggregation under vacuum in the exit cylinder sleeve." It gives a wave-forming phenomenon and rapidly enters the cavity with a vacuum vent.'' 7. On page 12 of the specification, line 2, “With Zhang...
"By force" is corrected to "by force that moves into the cavity with tension and gathering." 8. On page 15, line 20 of the specification, “It was written,
It was corrected to say, "The degree of vacuum inside the cavity was lowered."

Claims (6)

[Claims] (1) In a vacuum die casting machine that maintains a vacuum inside the cavity and injects the molten metal in the injection cylinder sleeve into the cavity with a plunger tip, the injection cylinder allows the molten metal to be stored from the injection cylinder sleeve on the pouring hole side. A vacuum die-casting device characterized in that an airtight seal member is arranged to prevent air from flowing into the sleeve. (2) The vacuum die-casting apparatus according to claim 1, wherein the airtight seal member is disposed between the outer periphery of the plunger tip and the inner periphery of the injection cylinder sleeve. (3) The vacuum die-casting apparatus according to claim 2, wherein the airtight seal member is ring-shaped and inserted into an annular groove provided on the outer periphery of the plunger tip. (4) The vacuum die-casting apparatus according to claim 2, wherein the airtight seal member is made of an elastic material having temperature resistance. (5) The vacuum die-casting apparatus according to claim 2, wherein the airtight seal member is ring-shaped and inserted into a plurality of grooves provided on the outer periphery of the plunger tip. (6) The airtight seal member includes a first seal member disposed between the outer periphery of the piston and the inner periphery of the injection cylinder sleeve, and a first seal member that closes the pouring hole when the plunger tip closes the pouring hole. 2. The vacuum die casting apparatus according to claim 1, comprising: two seal members.