JPH01313175A - Vacuum die casting machine - Google Patents

Abstract

PURPOSE:To spout molten metal for casting into a casting cavity by the expansion of the air permeated into a sleeve room to prevent the quality of a cast article from being deteriorated by equipping a back pressure regulation room on the outer periphery of a plunger tip in a vacuum die casting machine and further arranging an air-tight sealing member. CONSTITUTION:Molten metal of Al alloy, etc., in an injection cylinder sleeve 3 is forced out by the plunger tip 10 connected with a piston 11 and cast under pressure into the cavity made by dies 2A,2B. The back pressure regulation room P is provided on the outer periphery of the plunger tip 10 and connected with an exhaust vacuum device through a vacuum pressure introducing passage 11. An air-tight sealing member 12 is equipped annularly between the outer periphery of the plunger tip 10 and the inner periphery of the injection cylinder sleeve 3. Since the air permeating through the clearance between the plunger tip 10 and the injection cylinder sleeve 3 is discharged from the back pressure regulation room P through a vacuum pressure introducing passage 11, deterioration of the appearance and quality based on pin holes is prevented in the cast article obtained when the molten metal is injected by the expanded air force in the sleeve room 3A into the cavity.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a vacuum die-casting device that performs die-cast M production under a 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 conventionally used in a film 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 3A.

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 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 molten metal in the sleeve chamber 3A of the injection cylinder sleeve 3 is injected into the cavity 1 at a low speed by the plunger tip 5, and then injected at a high speed. The inside of the cavity 1 is kept in a vacuum under pressure and cast, and the mold is opened after the molten metal solidifies in the cavity 1 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 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, before the injection into the cavity 1 is started, a phenomenon occurs in which the molten metal in the sleeve chamber 3A of the injection cylinder sleeve 3 is ejected into the cavity 1. (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 of the present invention is to provide a vacuum die-casting device that prevents the phenomenon of jetting out into the cavity, and to achieve the above-mentioned purpose, a back pressure adjustment chamber is provided on the outer periphery of the plunger tip that slides inside the injection cylinder sleeve, and the above-mentioned An airtight seal member is arranged between the outer periphery of the plunger tip on the piston side of the back pressure adjustment chamber and the inner periphery of the injection cylinder sleeve, and vacuum pressure is introduced into the back pressure adjustment chamber during injection molding using the plunger tip. It is.

According to this, air does not flow into the sleeve chamber from the gap between the plunger tip and the injection cylinder sleeve, and the force moves into the cavity with body tension under reduced pressure in the sleeve chamber of the injection cylinder sleeve. 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 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 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 runner 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 pressure inside the sleeve chamber is Air in the injection cylinder sleeve on the pouring hole side flows into the 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 found that the cause of this problem was that the force generated during such movement 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.

lO is slidably disposed within the injection cylinder sleeve 3 and is attached to the piston 6 in the injection cylinder (not shown).
An annular groove 10A is carved on the outer circumference of the plunger chip 10. In this annular groove 10A, a vacuum pressure introduction path 1 passing through the plunger tip lO 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.

12 is an airtight sealing member disposed between the outer periphery of the plunger tip IO and the inner periphery of the injection cylinder sleeve 3, and more specifically, the airtight sealing member 12 is placed between the outer periphery of the plunger tip IO and the inner periphery of the injection cylinder sleeve 3. An annular groove 10B is provided on the outer periphery of the plunger tip 10, and an airtight sealing member 12 such as a piston ring is disposed within the annular groove 10B.

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, so that the position where the plunger tip 10 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 1 from the vacuum vent 8, and the interior of the cavity 1 and the sleeve chamber 3A are maintained at a vacuum pressure lower than atmospheric pressure, while the back pressure of the plunger chi 2 Vacuum pressure is also introduced into the control chamber P via the vacuum pressure introduction path 11, and the gap between the outer periphery of the plunger tip IO and the inner periphery of the injection cylinder sleeve 3 is maintained airtight by the airtight sealing member 12. The inside of the back pressure adjustment chamber P is maintained at a vacuum pressure. According to this, the back pressure adjustment chamber pressure P2 acting on the back pressure adjustment chamber P is greater than the sleeve chamber pressure P1 acting on the sleeve chamber 3A. At sleeve chamber pressure P1, the plunger tip l
Although an attempt is made to suck air from the outside into the sleeve chamber 3A through the gap between O and the injection cylinder sleeve 3, the sleeve chamber pressure P in the back pressure adjustment chamber P and the greater back pressure adjustment chamber pressure P2
Since this is in effect, the air which is being sucked into the sleeve chamber 3A through the gap is sucked out to the outside and pulled back, thereby preventing air from flowing into the sleeve chamber 3A.

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) When the pressure inside the sleeve chamber 3A is 200 Torr or more, ΔP = P2- P 1 <70 TorrΔP
: Critical pressure difference that can suppress the jet out phenomenon P2: Back pressure adjustment chamber pressure Pl Ni sleeve chamber pressure 2) When the pressure inside the sleeve chamber 3A is 200 Tart or less.

Δp=p2-PI<150 Torr Therefore, according to the vacuum die-casting apparatus of the present invention, when the plunger tip IO moves at least inside the injection cylinder sleeve 3 for low-speed injection, there is no pressure inside the back pressure adjustment chamber P. The applied vacuum pressure 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, so that no external air flows into the sleeve chamber 3A through the gap. .

Furthermore, since the airtight seal member 12 is disposed between the outer periphery of the plunger tip 10 on the side of the piston 6 from the back pressure adjustment chamber P and the inner periphery of the injection cylinder sleeve 3, the All vacuum pressures are from the back pressure adjustment chamber P.
It acts on the gap between the outer periphery of the plunger tip 10 and the injection cylinder sleeve 3 on the sleeve chamber 3A side, increasing the back pressure effect (vacuum pressure maintenance effect in the back pressure adjustment chamber). Pressure m! The vacuum pressure introduced into the i-chamber P can be reduced. (No large vacuum pressure is required) Therefore, as is clear from the above experimental results, injection is performed by the force of air moving into the cavity 1 with the volume expansion of the air under reduced pressure in the sleeve chamber 3A of the injection cylinder sleeve 3. This completely prevents the molten metal in the sleeve chamber 3A of the cylinder sleeve 3 from blowing up from the runner 7 into the cavity 1.

〔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.

■By placing an airtight seal member in the gap between the outer periphery of the plunger tip on the piston side of the back pressure adjustment chamber and the inner periphery of the injection cylinder sleeve, all the vacuum pressure introduced into the back pressure adjustment chamber is controlled by the back pressure. Back pressure m! acts on the gap between the outer periphery of the plunger tip and the inner periphery of the injection cylinder sleeve on the side of the sleeve chamber from the chamber. Since we were able to prevent air leakage from the gap between the outer periphery of the plunger tip on the piston side of the i-chamber and the inner periphery of the injection cylinder sleeve,
There is no need to increase the degree of vacuum pressure introduced into the back pressure adjustment chamber, the vacuum pump that generates the vacuum pressure introduced into the back pressure adjustment chamber can be downsized, and furthermore,
Even if the vacuum pump experiences a very temporary pressure drop (approaching atmospheric pressure), the gap between the plunger tip and injection cylinder can be maintained airtight with the airtight sealing member, increasing quality stability. This is what was created.

(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 drawing]

Figure 1 is a cross-sectional view of the main parts of a conventional vacuum die-casting device.
FIG. 2 is a sectional view of essential parts of the vacuum die-casting apparatus according to the present invention. 1 Cavity 3 Injection cylinder sleeve 3A Sleeve chamber 4 Molten pouring hole 6 Piston 7
, Runner 8 , Vacuum suction head 10 , Plunger tip + OA, Annular groove 11. , , , Vacuum pressure introduction path 12 , , Airtight sealing member P , Back pressure control chamber Procedure amendment August 1, 1988 Patent application No. 144500 2 Name of the invention Vacuum die casting device 3 Relationship with the case of the person making the amendment Patent Applicant Address 4-3-17 Shinjuku, Shinjuku-ku, Tokyo Name Keihin Seiki Co., Ltd. Representative Takeo Iwai 4 Agent 220 Address 2-11 Takashima, Nishi-ku, Yokohama No. 2, No. 5 Date of amendment order Initial issue 6 "Claims" column and "Detailed description of the invention" column 7 of the specification to be amended Contents of amendment 1, Claims column of the description Correct as follows. (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, A pressure adjustment chamber is provided, and an airtight seal member is arranged between the outer periphery of the plunger tip on the piston side of the back pressure adjustment chamber and the inner periphery of the injection cylinder sleeve. Vacuum die-casting equipment that introduces vacuum pressure into the sleeve chamber. ■The difference between the vacuum pressure applied to the back pressure adjustment chamber and the vacuum pressure applied to the sleeve chamber can be controlled by the sleeve chamber and back pressure adjustment, which can suppress the outflow from the sleeve chamber to the cavity. The vacuum die-casting apparatus according to claim 1, wherein the pressure difference between the back-pressure adjustment chamber and the plunger chip is less than or equal to a critical pressure difference between the plunger chip and the plunger chip. 2. The vacuum die-casting apparatus 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 bored inside the piston. 2. The vacuum die casting apparatus according to claim 1, wherein the sealing member is disposed in an annular groove provided on the outer periphery of the plunger tip.
``The more you raise your fist, the more you raise the degree of vacuum in the sleeve chamber of the goo sleeve.'' 3. In the 16th line of page 5 of the specification, "occurrence me...lower the degree of vacuum" is corrected to "this is likely to occur, so to prevent this, the degree of vacuum must be lowered". 4. In the 6th line of page 6 of the specification, "depressurization degree + 1@...gate section" is corrected to "lower the vacuum degree of, or runner gate section." 5. In the 20th line of page 6 of the specification, "sleeve chamber...accompanied by" is corrected to "accompanied by volume expansion and aggregation under vacuum in the sleeve chamber." 6. In the specification, page 7, line 11, ``The inside of the sleeve is evacuated to 50 degrees below atmospheric pressure.'' is corrected to ``The inside of the sleeve is evacuated.The vacuum pressure is 50 degrees.'' 7. In the 14th line of page 7 of the specification, ``the pressure of...cavity'' is amended to ``when the vacuum pressure of . 8. On page 9 of the specification, lines 4 and 5, “This inflow
9. In the specification, page 12, lines 1 to 4, "chamber pressure..."
・The difference between the vacuum pressure PL in the cylinder chamber and the vacuum pressure P2 in the back pressure adjustment chamber acting in the front pressure adjustment chamber P does not exceed the critical pressure difference described later. The plunger tip 10 and the injection shaft are corrected by the sleeve chamber vacuum pressure P1 acting in the chamber 3A. 10. In the specification, page 12, lines 7 to 11, "P is used to prevent the sleeve chamber..." from being replaced with "P is vented, so air is prevented from flowing into the sleeve chamber 3A." , which can prevent the molten metal from flowing out into the cavity 1.
and correct it. 11. Change "Pl: Back pressure adjustment chamber pressure" on page 12, line 20 of the specification to "Pl: Back pressure adjustment chamber vacuum pressure (7Br)"
Correct with J. 12. Change "Pl Nisleeve chamber pressure" in the first page of page 12 of the specification to "Pl Nisleeve chamber vacuum pressure (Torr) J
and correct it. add ``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 13, lines 10 to 12 "Air flow ψ... meets" is corrected to "Since the air flow is almost blocked, no molten metal spouts into the cavity I." 15. On page 14 of the specification, line 6, “Air below...”
"into the cavity 1" is corrected to "into the cavity 1, accompanied by the volumetric expansion and gathering of air below, without causing a wave-forming phenomenon of the molten metal in the sleeve chamber 3A." 1B, page 14, line 18 of the specification, ``degree of vacuum...''
・Correct "injection machine" to "lower the vacuum level of or runner injection machine".

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 regulating chamber is provided, and an airtight sealing member is arranged between the outer periphery of the plunger tip on the piston side of the back pressure regulating chamber and the inner periphery of the injection cylinder sleeve. Vacuum die casting equipment that introduces vacuum pressure. (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 the sealing member is disposed within an annular groove provided on the outer periphery of the plunger tip.