JPH01313171A - Vacuum die casting machine - Google Patents

Abstract

PURPOSE:To inject molten metal into a casting cavity by the air coming in from the clearance between a plunger tip and a cylinder sleeve to prevent the quality of a die cast article from being deteriorated by providing an annular back pressure regulation room 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 injection cylinder sleeve 3 are cast under pressure through a runner 7 into a casting cavity 1 which is composed of a fixed die 2A and a movable die 2B and is provided with a vacuum vent 8. The annular back pressure regulation room P is provided on the outer peripheral surface of the plunger tip 10 for extruding the molten Al alloy set on the tip of the piston 6 and is connected with a vacuum introducing passage 11 to make the pressure in the back pressure regulation room P smaller than that in the injection cylinder sleeve 3. Since the air permeating through the clearance between the sleeve 3 and the plunger tip 10 is absorbed into back pressure regulation room P, the air is expanded in a sleeve room 3A and pressurizes the molten metal 3A and is injected into the cavity 1, the appearance and quality of the cast article obtained are prevented from being deteriorated by pin holes, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to vacuum die casting equipment that performs die casting under relatively high vacuum inside a cavity, and is capable of producing large quantities of precision castings of aluminum alloy. Produce,
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 1 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.

For ease of explanation, the inside of the injection cylinder sleeve 3 on the runner 7 side (left side in the figure) from the tip 5A of the plunger tip 5 will be referred to as the sleeve chamber 3B.

Further, a vacuum vent 8 is opened in the cavity I, 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 sleeve chamber 3A of the injection cylinder sleeve 3 through the pouring hole 4, and then the piston is pressed by the injection cylinder. 6, the plunger tip 5 injects the molten metal in the sleeve chamber 3A of the injection cylinder sleeve 3 into the cavity 1 at low speed.
During high-speed injection, the inside of the cavity 1 is kept in a vacuum with the vacuum pressure introduced into the re-cavite 1 from the vacuum vent 8 during such injection, and the mold is opened after waiting for the molten metal to solidify inside the cavity 1. This is for taking out the product.

[Problem to be solved by the invention]

Such conventional vacuum die casting equipment has the following problems. The molten metal in the sleeve chamber 3A of the injection cylinder sleeve 3 is not yet injected into the cavity 1 during low-speed injection by the plunger tip 5, but fills the runner 7 including the sleeve chamber 3A of the injection cylinder sleeve 3. However, a phenomenon occurs in which the molten metal in the sleeve chamber 3A of the injection cylinder sleeve 3 jets out into the cavity 1 before injection into the cavity 1 is started. (This jet stream is shown as A in Figure 1.) According to this, it creates a hot water barrier in the product, impairing its appearance quality, and it also causes countless large and small blowholes to be scattered throughout the product, deteriorating its airtightness. It was something to do. 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. This phenomenon is completely different from the so-called "sagging phenomenon" in which the liquid slowly enters the cavity and partially solidifies, creating a sag. It is characterized by the fact that it penetrates with such force that it reaches the top of the cavity.

This jet flow phenomenon becomes more likely to occur as the degree of vacuum in the cavity and the sleeve chamber of the injection cylinder sleeve increases, so to prevent this, the degree of vacuum should be lowered or the injection resistance at the runner gate section should be increased. May be cast.

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 Problem] [Operation] The vacuum die-casting apparatus according to the present invention can reduce the degree of vacuum in the sleeve chamber of the cavity and injection cylinder sleeve, or increase the injection resistance of the runner gate part. The purpose is to provide a vacuum die casting device that prevents the phenomenon of jetting out into the cavity.In order to achieve the above purpose, a back pressure adjustment chamber is provided on the outer periphery of the plunger tip that slides inside the injection cylinder sleeve. Vacuum pressure is introduced into the back pressure adjustment chamber during injection molding using a jar chip.

According to this, air does not flow into the sleeve chamber from the gap between the plunger tip and the injection cylinder sleeve, but is caused by the force of the injection cylinder sleeve moving into the cavity with volume expansion under reduced pressure in the sleeve chamber. This prevents the molten metal in the sleeve chamber of the injection cylinder sleeve from blowing up from the runner into the cavity.

〔Example〕

First, the inventor conducted an experiment to clarify the mechanism of occurrence of an undesirable jetting phenomenon into a cavity before high-speed injection in a vacuum die-casting machine.

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 sleeve chamber of 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 liquid surface was quiet. This critical pressure is the amount of hot water.

Although it varies depending on conditions such as water temperature, tip clearance between plunger tip and injection cylinder sleeve, injection cylinder sleeve diameter, runner shape, etc., in this experiment it was 400 to 5.
It was 50 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, the pressure in the cavity and the sleeve chamber of the injection cylinder sleeve is reduced by 50 To
Even when the temperature was changed to rr, the molten metal in the sleeve chamber 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 sleeve chamber of the injection cylinder sleeve is the sleeve chamber on the tenner side, which is divided by the plunger tip placed inside the injection cylinder sleeve, and the pouring hole side. Due to the differential pressure between the injection cylinder sleeve and the injection cylinder sleeve, the injection into the sleeve chamber through the gap between the injection cylinder sleeve and the plunger tip (generally, the gap between the plunger tip and the injection cylinder sleeve is about 50 mm). Air flows into the injection cylinder sleeve on the side of the hot water hole.

This inflowing air rapidly moves into the cavity where the vacuum vent is located without volume expansion under the reduced pressure in the sleeve chamber.

It was discovered that the cause of this problem was found to be due to the force generated during such movement, which caused the molten metal filling the sleeve chamber of the injection cylinder sleeve to be blown up into the cavity at once.

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

10 is slidably disposed within the injection cylinder sleeve 3, and a piston 6 is attached to the injection cylinder (not shown).
This plunger chip is connected via a ring-shaped groove on the outer circumference of the plunger chip 10! OA is engraved. In this annular groove 10A, a vacuum pressure introduction path 1 passing through the plunger tip 10 and the inside of the piston 6 is provided.
1 are connected, and the end of this vacuum pressure introduction path 11 is connected to a vacuum pressure source (not shown).

Therefore, the back pressure adjustment chamber P is formed in a state in which the vacuum pressure generated by the vacuum pressure source is introduced into the annular groove 10A of the plunger tip IO through the vacuum pressure introduction path 11.

Next, its effect will be explained.

First, prior to injection, the plunger tip IO is moved rightward in the figure by the piston 6, so that the pouring hole 4 and the injection cylinder sleeve 3 are brought 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 IO is moved to the left in the figure by the piston 6, so that the position where the plunger tip IO closes the pouring hole 4 becomes the starting point for low-speed injection. At the starting point of such low-speed injection,
Vacuum pressure is introduced into the cavity l from the vacuum vent 8, and the inside of the cavity l and the sleeve chamber 3A are maintained at a vacuum pressure lower than atmospheric pressure, while the back pressure adjustment chamber of the plunger tip lO Vacuum pressure is also introduced into P through the vacuum pressure introduction path 11, and the inside of the back pressure adjustment chamber P is maintained at vacuum pressure. The back pressure adjustment chamber pressure P2 acting within the back pressure adjustment chamber P is set to be greater than the sleeve chamber pressure P acting within the sleeve chamber 3A.
According to this, at the sleeve chamber pressure PL acting in the sleeve chamber 3A, air is not sucked from the outside into the sleeve chamber 3A through the gap between the plunger tip 10 and the injection cylinder sleeve 3, but the back pressure adjustment chamber Since the back pressure adjustment chamber pressure P2, which is greater than the sleeve chamber pressure P1, is acting on P, the air that is about to be sucked into the sleeve chamber 3A from the gap is sucked out and pulled back to the outside, and thus the sleeve chamber 3A This prevents air from flowing inside.

According to the experimental results by the present inventor, the critical pressure difference ΔP between the sleeve chamber 3A and the back pressure adjustment chamber P, which can suppress the ejection phenomenon from the sleeve chamber 3A to the cavity 1, is expressed by the following equation.

1) If the pressure inside the sleeve chamber 3A is 200 Torr or more.

Δp=p2−PH<70 Torr ΔP: Critical pressure difference that can suppress the outflow phenomenon P2: Back pressure adjustment chamber pressure PI = Sleeve chamber pressure 2) When the pressure inside the sleeve chamber 3A is 200 Torr or less.

ΔP==P2−p, <150 Torr Therefore, according to the vacuum die casting apparatus of the present invention, at least when the plunger tip 10 moves within the injection cylinder sleeve 3 for low-speed injection, the back pressure adjustment chamber P The vacuum pressure applied inside the cylinder prevents the flow of air from flowing into the sleeve chamber 3A through the gap between the plunger tip 10 and the injection cylinder sleeve 3, thereby preventing external air from flowing into the sleeve chamber 3A through the gap. There is no.

Therefore, as is clear from the above experimental results, the air in the sleeve chamber 3A of the injection cylinder sleeve 3 is moved into the cavity 1 by the force of air moving into the cavity 1 with volume expansion under reduced pressure in the sleeve chamber 3A of the injection cylinder sleeve 3. This completely prevents the molten metal from blowing up from the runner 7 into the cavity 1.

Further, the embodiment shown in FIG. 3 has a plunger tip l.
A plurality of annular grooves 10A and IOB are provided on the outer periphery of O.

10C, IOD is provided, and each annular groove is provided with a vacuum pressure introduction path 11A, 1 connected to a respective vacuum pressure source (not shown).
1B, IIC, and IID to provide a plurality of back pressure adjustment chambers FA, PB, PC, and PD. This improves the efficiency of preventing air from flowing into the sleeve chamber through the gap between the plunger tip and the injection cylinder sleeve.

〔Effect of the invention〕

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

■Since no mechanical seal is used in the gap between the plunger tip and the injection cylinder sleeve, there is no wear during sliding, making stable casting possible over a long period of time.

(2) By providing a plurality of back pressure adjustment chambers, it is possible to easily improve the efficiency of preventing air from flowing into the sleeve chamber.

(2) By providing a vacuum pressure introduction path in the piston for introducing vacuum pressure into the back pressure control chamber, the degree of freedom in designing the piping of the device can be increased.

[Brief explanation of the drawings] 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 3A.Sleeve chamber 4.Pouring hole 6. ,,,piston 7
, , Runner 8 , Vacuum vent 10 , Plunger tip 10A , Annular groove 11. , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , . Related Patent Applicant Address 4-3-17 Shinjuku, Shinjuku-ku, Tokyo Name Keihin Seiki Co., Ltd. Representative Takeo Iwai 4 Agent 220 Address 2-5 LF, 2-chome Takashima, Nishi-ku, Yokohama Date of Amendment Order Spontaneous 6 Column ``Claims'' and ``Detailed Description of the Invention'' of the specification subject to amendment 7 Contents of the amendment ``(1) The inside of the cavity is kept in a vacuum to drain the molten metal in the injection cylinder sleeve. In a vacuum die casting machine that performs injection molding into a cavity with a plunger tip, a back pressure adjustment chamber is provided on the outer periphery of the plunger tip that slides inside the injection cylinder sleeve.During injection molding with the plunger tip, a back pressure adjustment chamber is provided inside the back pressure adjustment chamber. Vacuum die casting equipment that introduces vacuum pressure. ■ Sleeve chamber and back pressure adjustment chamber that can suppress the difference between the vacuum pressure applied in the back pressure adjustment chamber and the vacuum pressure applied in the sleeve chamber from ejecting from the sleeve chamber to the cavity. The vacuum die-casting device according to claim 1, wherein the pressure difference is less than or equal to the critical pressure difference between the plunger chip and the plunger chip. 2. The vacuum die-casting device according to claim 1, wherein the back pressure adjustment chamber is annularly provided around the outer periphery of the plunger chip, and connected to a vacuum pressure source through a vacuum pressure introduction path that can be punctured inside the piston. The vacuum die-casting apparatus according to claim 1, wherein a plurality of control chambers are provided around the outer periphery of the plunger chip and are arranged in an annular shape.
"I'll call you A," he corrected. 3. Goo sleeve on page 5 of the specification, lines 12 and 13. The higher the degree of vacuum in the sleeve chamber of the goo sleeve, the more likely it is to occur. To prevent this, lower the vacuum level.'' 4. In the third line of page 6 of the specification, "degree of vacuum...Φ...at the runner gate" is corrected to "lower the degree of vacuum at or at the runner gate." 5. In the 14th line of page 6 of the specification, amend ``sleeve chamber summoning...accompanied by kyya'' to ``r, accompanied by volume expansion and aggregation under vacuum in the sleeve chamber''. 6. In the 5th line of page 7 of the specification, ``The inside of the reeve was evacuated. The vacuum pressure was 50 yen above atmospheric pressure.'' 7. On page 7, line 8 of the specification, "the pressure of the fist, the fist, the ban, the cavity" is corrected to "when the vacuum pressure of the device falls below a certain level, the cavity suddenly appears." 8. In the specification, page 8, lines 18 to 18, "this inflowing air into the cavity" is replaced with "this inflowing air expands and gathers in the sleeve chamber under the vacuum inside the sleeve chamber. It gives a wave-forming phenomenon to the molten metal inside, and corrects it as "in a cavity with a vacuum vent." 9. Write in R chamber 3A on page 11, lines 5 to 8 of the specification... plan'' is changed to ``vacuum pressure P in the sleeve chamber acting in chamber 3A and pressure in back pressure adjustment chamber P''. The difference in the back pressure adjustment chamber vacuum pressure P2 that acts is a pressure that does not exceed the critical pressure difference described later, and according to this.Sleeve chamber vacuum pressure PI that acts in the sleeve chamber 3A
The plan is corrected. 108 Specification, page 11, lines 11 to 16, ``It is something... Since most of the air is discharged through the vacuum pressure introduction path 11, the air is prevented from flowing into the sleeve chamber 3A, and the molten metal is prevented from flowing out into the cavity 1.'' 11. Change "P2: Back pressure adjustment chamber pressure" on page 12, line 5 of the specification to "P2: Back pressure adjustment chamber vacuum pressure (chorr)"
” he corrected. 12. "Pl Nisleeve chamber pressure" on page 11, page 5 of the specification is "Pl Nisleeve chamber vacuum pressure (Torr)"
and correct it. ``In addition, this critical pressure difference is determined by the amount of hot water, the hot water temperature, the tip clearance between the plunger tip and the injection cylinder sleeve,
This critical pressure difference must be set appropriately as it varies depending on conditions such as the injection cylinder sleeve diameter, runner shape, injection cylinder sleeve temperature, etc.'' 14. Specification, page 12, lines 15 to 17 "Air flow...-" is corrected to "Since the air flow is almost blocked, no molten metal will be ejected into the cavity 1." 15. On page 12, line 20 of the specification, "Under the air order...
- into the cavity 1'' is corrected to ``with the volumetric expansion and collection of air below, without causing a wave-forming phenomenon of the molten metal in the sleeve chamber 3B, and therefore into the cavity 1''. 1B, page 14, line 2 of the specification, ``degree of vacuum...''
``injection machine'' is corrected to ``lower the vacuum level of or runner injection machine.'' 1930 8JI24rl ↑, +1 revised by Fumitake Kawa, Director-General of the Agency, 1 ° 1 Indication of the matter 1986 Patent application No. 144496 2 Name of the invention Vacuum die casting device 3 Supplement 1 T, Maker/IS Relationship to the matter Patent applicant address: Shinjuku 4-chome, Shinjuku-ku, Tokyo [No. 13-17] Name: J Co., Ltd. (Hama Seiki Seisakusho Representative Director: Iwai
Taketo 4 Agent 220 Address 21TI Takashima, Nishi-ku, Yokohama City R number 25;5
Column 7 of the [Invention), +y, 4a explanation” of the hn city order. +li+lmi contents

Claims (5)

[Claims] (1) In a vacuum die casting machine that maintains a vacuum inside the cavity and injects the molten metal inside the injection cylinder sleeve into the cavity with a plunger tip, back pressure is applied to the outer periphery of the plunger tip that slides inside the injection cylinder sleeve. A vacuum die-casting device is provided with a control chamber, and a vacuum pressure is introduced into the back pressure control chamber during injection molding using a plunger tip. (2) The vacuum die casting apparatus according to claim 1, wherein the vacuum pressure applied to the back pressure adjustment chamber is greater than the vacuum pressure applied to the sleeve chamber. (3) The vacuum die-casting apparatus according to claim 1, wherein the back pressure adjustment chamber is provided in an annular shape around the outer periphery of the plunger chip. (4) The vacuum die-casting apparatus according to claim 1, wherein the back pressure adjustment chamber is provided in an annular shape around the outer periphery of the plunger tip, and is connected to a vacuum pressure source through a vacuum pressure introduction path bored inside the piston. . (5) The vacuum die casting apparatus according to claim 1, wherein a plurality of the back pressure adjustment chambers are provided in a ring shape around the outer periphery of the plunger chip.