JPH0263665A - Vacuum die casting device - Google Patents

Abstract

PURPOSE:To inhibit a fact that a molten metal is brought to jet outflow into a cavity before an injection by connecting a back pressure control chamber and a vacuum source by a first vacuum leading-in passage, and also, connecting the back pressure control chamber and the cavity by a second vacuum leading-in passage. CONSTITUTION:At the time point when a plunger chip 5 closes a pouring hole 4, vacuum pressure is supplied through a first vacuum leading-in passage 8 from a vacuum source P. As a result, first of all, pressure in a back pressure control chamber 5B is reduced through a first vacuum leading-in passage 8, and thereafter, the inside of a cavity 1 is brought to pressure reduction to a vacuum through a second vacuum leading-in passage 9 connected to the back pressure control chamber 5B. Accordingly, the degree of vacuum of the back pressure control chamber 5B becomes larger temporarily than a degree of vacuum of the inside of the cavity 1. In such a way, it can be prevented entirely that the open air intrudes into a sleeve chamber 3A from a gap between the outer peripheral surface of the plunger chip 5 and the inner peripheral surface of an injection cylinder sleeve 3, therefore, it does not occur that a molten metal in the sleeve chamber 3A is brought to jet outflow into the cavity 1 before an injection.

Description

[Detailed Description of the Invention] [Field of Industrial Application] 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]

According to Japanese Patent Application No. 61-217052, it has been proposed to set a time difference between the start of evacuation of the sliding surface between the injection cylinder sleeve and the plunger tip and the start of vacuum evacuation inside the cavity. First, open the first solenoid valve to apply vacuum pressure in the vacuum source to the sliding surface between the injection cylinder sleeve and the plunger tip, and then
．． The second solenoid valve is opened with a time delay of about 1 to 1 second to apply vacuum pressure in the vacuum source to the cavity, thereby causing the sliding surface between the injection cylinder sleeve and the plunger tip to Intrusion of outside air into the sleeve chamber is blocked, thereby preventing molten metal from spouting out into the cavity before injection.

[Problem to be solved by the invention]

According to such a conventional vacuum die casting apparatus, it is difficult to provide an extremely short time difference between the start of evacuation of the sliding surface between the injection cylinder sleeve and the plunger tip and the start of evacuation of the inside of the cavity.

This is because the opening and closing of the vacuum passage is electrically or mechanically controlled using a solenoid valve or the like.

[Means to solve problems]

The vacuum die-casting device of the present invention has been developed in view of the above-mentioned problems, and does not require any electrical or mechanical control at all when the sliding surface between the injection cylinder sleeve and the plunger tip starts to be evacuated. , At the vacuum starting surface in the cavity, the degree of vacuum applied to the sliding surface is temporarily greater than the degree of vacuum applied to the cavity, and in order to achieve the above purpose, the inside of the cavity is maintained in a vacuum. In a vacuum die casting device that injects molten metal in an injection cylinder sleeve 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; The vacuum source is connected through a first vacuum introduction path, and the back pressure adjustment chamber and the cavity are connected through a second vacuum introduction path.

[Effect]

When vacuum pressure from a vacuum source is introduced into the first vacuum introduction path, the vacuum pressure first acts in the back pressure adjustment chamber with a high degree of vacuum, and then the vacuum pressure in the back pressure adjustment chamber is introduced into the second vacuum introduction path. This is achieved by introducing the vacuum pressure introduced into the back pressure adjustment chamber into the cavity through the second vacuum introduction path.

〔Example〕

An embodiment of the vacuum die-casting apparatus according to the present invention will be described below with reference to FIG.

2 is a cavity, which is composed of a fixed mold 2A and a movable mold 2B. 3 is 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.

An annular groove is bored in the outer circumference of the plunger tip 5 to form a back pressure adjustment chamber 5B. A first vacuum introduction path 8 passing through the plunger tip 5 and the piston 6 opens into this back pressure adjustment chamber 5B.
The end of the vacuum introduction path 8 is connected to a vacuum pressure source P.

On the other hand, a second vacuum introduction path 9 is opened in the cavity 1, and the end thereof is connected to the back pressure adjustment chamber 5B. Specifically, the plunger tip 5. A passage bored in the piston 6 constitutes a part of the second vacuum introduction passage 9.

Next, its effect will be explained.

First, before injection, insert the plunger tip 5 into the piston 6.
The injection cylinder sleeve 3 is moved to the right in the figure 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 through the pouring hole 4. The amount of molten metal stored must be set appropriately.

Next, the plunger tip 5 is moved to the left in the figure by the piston 6, whereby the position where the plunger tip 5 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 supplied from the vacuum source P via the first vacuum introduction path 8. (For example, by opening the valve ■) According to this, the pressure in the back pressure adjustment chamber 5B is first reduced through the first vacuum introduction path 8, and then the pressure in the back pressure adjustment chamber 5B is reduced.
The inside of the cavity 1 is evacuated to vacuum via the second vacuum introduction path 9 connected to.

What is particularly noteworthy at this time is that the back pressure control chamber 5 and the cavity 1 are simultaneously depressurized by the vacuum source P, but as mentioned above, vacuum pressure is introduced into the back pressure control chamber 5B inside the cavity 1. Since the vacuum pressure is applied after the back pressure adjustment chamber 5B is removed, the degree of vacuum in the back pressure adjustment chamber 5B becomes larger than the degree of vacuum in the cavity 1, and only after a short period of time has passed. and the degree of vacuum inside the cavity 1 is the same pressure.

According to this, the degree of vacuum in the cavity 1 including the sleeve chamber 3A does not become greater than the degree of vacuum in the back pressure adjustment chamber 5B, regardless of the time, so the plunger tip 5
It is possible to completely prevent outside air from entering the sleeve chamber 3A through the gap between the outer circumferential surface of the injection cylinder sleeve 3 and the inner circumferential surface of the injection cylinder sleeve 3. As a result, the molten metal in the sleeve chamber 3A flows into the cavity 1 before injection. It is possible to provide a vacuum die-cast product with no blowholes and good casting surface quality. The first vacuum introduction path 8 only needs to open in the gap between the inner peripheral surface of the injection cylinder sleeve 3 and the outer peripheral surface of the plunger tip 5, and does not necessarily require the back pressure adjustment chamber 5B.

〔Effect of the invention〕

As described above, according to the vacuum die casting apparatus of the present invention, vacuum pressure is supplied from a single vacuum source to the back pressure adjustment chamber through the first vacuum introduction path, and simultaneously from the back pressure adjustment chamber through the second vacuum introduction path. Since the inside of the cavity is kept under vacuum, even if vacuum pressure is supplied from the vacuum source to the back pressure adjustment chamber and the cavity at the same time, the degree of vacuum in the back pressure adjustment chamber must be made greater than the degree of vacuum in the cavity at the beginning of supply. This made it possible to completely prevent the molten metal from spewing out into the cavity before injection.

In addition, since no electrical or mechanical actuators are used to control the time difference and pressure difference in the vacuum pressure in the back pressure adjustment chamber and cavity, accurate and reliable control is possible over a long period of time. In addition, since there is no increase in the number of parts, an inexpensive vacuum die-casting device can be provided.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of essential parts showing an embodiment of a vacuum die-casting apparatus according to the present invention. 1 Cavity 3 Injection cylinder sleeve 3A Sleeve chamber 5 Plunger tip 5B Back pressure adjustment chamber 8 First vacuum introduction path 9 ,,,Second vacuum introduction path

Claims (1)

[Claims] In a vacuum die-casting device that maintains the inside of the cavity in a vacuum and injects the molten metal inside the injection cylinder sleeve into the cavity with a plunger tip, the outer periphery of the plunger tip that slides inside the injection cylinder sleeve. A back pressure adjustment chamber is provided in; the back pressure adjustment chamber and a vacuum source are connected through a first vacuum introduction path, and the back pressure adjustment chamber and the cavity are connected through a second vacuum introduction path. die casting equipment.