JPS5846386B2 - Low pressure die casting method and equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vacuum die casting method and apparatus.

Die casting equipment is a device that forms a mold cavity on the abutting surfaces of a fixed mold and a movable mold, injects the molten material into this mold cavity, and obtains a molded product according to the shape of the mold cavity. However, when the air remaining in the cavity mixes with the molten material to be injected, it remains as bubbles in the molten material to be injected, creating so-called cavities in the molded product and significantly reducing its value as a molded product.

Therefore, various structures have been proposed for discharging the gas remaining in the cavity.

Some of these conventional structures apply the depressurization method.

A die-casting device using a reduced pressure method connects a mold cavity and a vacuum device to forcibly exhaust gas within the cavity to prevent the gas from mixing with the molten material to be injected.

However, when the vacuum device is connected to the cavity, the molten material to be injected with large kinetic energy enters this communication passage, destroying the vacuum device or ejecting it outside the mold, causing a major accident. There was a drawback.

Several proposals have been made in an attempt to resolve these inconveniences.

One of these is one in which the gas exhaust path connected to the vacuum device is formed in a zigzag pattern, and the area around this exhaust path can be cooled with cooling water.

However, if such a structure is adopted, gas will certainly escape, but the zigzag passage to prevent the injected molten material has a large resistance, making it impossible to escape a large amount of gas in a short period of time.
・.

In addition, in order to maintain a high vacuum inside the cavity, the precision of the mating surfaces of the mold must be improved, which increases the manufacturing cost of the mold and makes it difficult to apply it to molded products that require a core. is extremely difficult.

Another proposal is, for example, to provide a shut-off valve that shuts off the pressure-reduction passage near the side of the pressure-reduction passage connected to the vacuum device, and to open and close this shut-off valve with a cylinder controlled by a solenoid valve. There is a known structure in which injection molding is performed by blocking the vacuum passage just before the injection molding.

However, with this type of structure, the timing of shutting off the shutoff valve is difficult; if the shutoff valve is shut off too early, the pressure reduction effect will be lost, and if the shutoff is shut off too late, the molten material to be injected may spray out of the mold.・There were some drawbacks.

The object of the present invention is to provide a low-pressure die-casting method which is capable of rapidly discharging the gas in the mold cavity, and which prevents the molten material entering the cavity from spouting out of the mold. We are in the process of providing equipment.

In the present invention, in order to achieve the above-mentioned object, a pressure reduction passage leading from the mold cavity to a pressure reduction circuit outside the mold is opened by the action of a valve. , by directly applying the inertial force of the injected molten material that has advanced from inside the cavity during injection to the valve,
A configuration was adopted in which the valve was moved and the pressure reduction passage was directly blocked by this valve.

Hereinafter, the present invention will be described in detail together with embodiments shown in the drawings.

The figure is for explaining one embodiment of the present invention. In the figure, the reference numeral 1 indicates a fixed mold (or a movable mold), and the butting surface of the fixed mold 1 with the movable mold is The mold cavity 2 is formed.

A vacuum passage 3, which is a first passage for pressure reduction (or gas discharge), is formed on the butt surface of the mold while communicating with this cavity 2. The second branch is for depressurization (and the second one is for gas exhaust).
Bypasses 4, 4, which are passages, are also formed along the abutting surfaces, and open at the rear of the decompression passage 3.

A cylindrical body 5 having a valve seat 5c at its lower end is fitted into a half hole provided in the dividing plane between the fixed mold 1 and the movable mold, and this cylindrical body 5 is fixed. Said bypass 4 of mold 1
, 4 so that it can be located near the opening end of the
The cylinder 6 fixed to the fixed mold 1 is configured to be able to change its position in the vertical direction in the figure.

A valve 7 is provided in the cylindrical body 5 so as to be slidable along the axial direction of the cylindrical body 5.
is provided, and the rear end of this valve 7 serves as a stopper 1a, and even if the tip becomes a relatively large-diameter valve head 7b.
Ru.

The valve 7 is provided at the end of the pressure reduction passage 3, which is the first passage, so as to be slidable in the axial direction of the end of the pressure reduction passage 3.
Ru.

Moreover, the valve 7 is used for depressurization that communicates with the outside of the mold from the bypass 4, 4, which is the second passage, and the side surface of the movement path of the valve 7, which is the end of the bypass 4, 4. The L/L has a surface portion that can communicate with and shut off the third passage for gas exhaust, and also absorbs the inertia of the injected molten material that advances through the decompression passage 3. One end surface that can receive the pressure reduction passage 3
L.L.L.

The stopper 7a contacts a partition wall 5a formed in the middle of the cylindrical body 5 to restrict its movement limit.
A spring 8 is elastically mounted between a and the inner surface of the upper end of the cylinder 5, and the elastic force of the spring 80 pushes the valve 7 downward, blocking the opening end of the decompression passage 3 and closing the L.
・Ru.

The opening ends of the bypasses 4, 4 are open on the discharge side of the movement path of the valve 7.

An opening 5b is formed at a position closer to the fixed mold 1 than the partition wall 5a of the cylindrical body 5, and is also a part of a third passage for depressurization and gas discharge. One end of a pipe 9 is connected to the portion 5b.

The other end of the pipe 9 is connected to a pressure reducing cylinder 10 having a relatively large diameter.

The decompression cylinder 10 has an opening 10a on its rod end side.
The piping 9 is connected to the head side of this decompression cylinder.

Piston rod 11 of piston 11 of pressure reducing cylinder 10
The outer end of a is connected to the piston 1 of the relatively small diameter cylinder 12.
2a, and by supplying working fluid to the cylinder 12, the piston 11 of the pressure reduction cylinder 10 is pushed, and by the pump action, the head side of the pressure reduction cylinder 10 is made negative pressure, and is in a vacuum state. I can do it.

Note that a check valve indicated by reference numeral 13 is interposed in the middle of the pipe 9.

Next, the effects of this embodiment configured as described above will be explained.

First, a movable mold (not shown) and a fixed mold are butted against each other and clamped.

When the mold clamping is completed, the mold clamping state is input as a signal to a solenoid valve that controls the fluid pressure cylinder 12 via a limit switch (not shown) or the like.

As a result, the cylinder 12 is activated and the head side of the decompression cylinder 10 is brought into a vacuum state, and this negative pressure is led to the opening 5b of the cylinder 5 via the pipe 9.

In this state, as shown in the figure, the cylindrical body 5 has been moved to the limit of entry into the fixed mold 1 by the operation of the cylinder 6, the valve head 7b of the valve 7 is at the lower limit position, and the pressure reducing passage 3 The open end of the bypass 4 is blocked and the open end of the bypass 4 is opened.

The time point at which the decompression cylinder 10 is activated can be set at the start of high-speed injection of the injection plunger, as shown in the figure.

Simultaneously with mold clamping, that is, from low-speed injection, the vacuum cylinder 1
It is possible to operate at 0°C, but at this point the injection sleeve's supply port for the molten material to be injected is open, and air will be sucked in from there (the efficiency will be slightly reduced).

The negative pressure led to the opening 5b of the cylinder 5 passes through the cylinder 5 and is passed through the bypass 4. guided into the decompression passage 3 and the cavity 2,
C. gas remaining in the cavity 2 is sucked into the vacuum cylinder 10 via the pipe 9.

When the inside of the cavity 2 reaches a predetermined degree of vacuum, the operation of the decompression cylinder 10 is stopped and the injection of the molten metal, which is the molten material to be injected, is continued.

The molten material to be injected is sent into the cavity 2 at high pressure and high speed by an injection plunger, filling the cavity 2 in a vacuum state.

The molten material to be injected that has filled the cavity 2 enters the depressurizing passage 3 and is L · with a large inertial force.
goes straight and collides with the valve head 7b of the valve 7.

As a result, the valve 7 is pushed outward from the mold against the elastic force of the spring 80, and at the same time the opening ends of the bypasses 4, 4 are blocked by the valve head 7b.

Therefore, even if the molten material to be injected tries to bypass the bypasses 4, 4 and exit the mold, it is blocked by the valve head 7b and cannot exit.

As described above, when the molten material to be injected fills the mold cavity and eventually solidifies, the mold is opened.

Just before this mold opening, the cylinder 6 is actuated, and the cylindrical body 5 is moved toward the outside of the fixed mold 1 together with the valve T.

As a result, the adhesion between the valve head 7b and the solidified injected molten material that has filled up to the opening ends of the vacuum passage 3 and the bypass 4 is released, and the mold cavity 2, the vacuum passage 3, and the bypass 4 are no longer adhered to each other. The solidified molten material to be injected adheres to the fixed mold side and separates as the mold is opened, and eventually becomes L as shown in the figure.
(・The ejector pin operates and releases the molded product from the movable mold.

In this way, one molding cycle is completed, and the same operation is repeated again.

As described above, the pressure inside the cavity is reduced and the molten material to be injected is supplied under a predetermined degree of vacuum, so the molten material to be injected and the remaining gas are not mixed, and the molded product is (
- It is possible to obtain non-porous die-cast products without the formation of so-called nests.

By the way, in the above embodiment, a structure in which a pressure reduction cylinder is used as the pressure reduction means is illustrated, but the pressure reduction means is not limited to this structure. For example, a vacuum pump and a pressure reduction tank may be combined, and this may be connected to a pressure reduction passage. You may also adopt a structure that connects to 3 and obtains a predetermined degree of vacuum (゛.

As is clear from the above description, according to the present invention, the pressure reduction passage leading from the mold cavity to the pressure reduction circuit outside the mold is opened by the action of the valve (thus, injection is performed with the inside of the cavity in a reduced pressure state). During injection, the L-
As a result, a large amount of gas in the mold cavity can be rapidly discharged, and the molten material to be injected that enters the cavity does not spray out of the mold, resulting in a clean and good quality die-cast product. can be obtained.

In addition, since a large amount of gas escapes, the accuracy of the mold mating surface of the mold is not necessary (it is not necessary to have such high precision), and the parting surface between the mold and the core can also be used as the dividing surface between the cores. .

Furthermore, there is no need to adjust the timing of closing the valve, which is extremely advantageous.

In this invention, the inertial force of the molten metal, which is the molten material to be injected, is directly applied to the valve that opens the gas exhaust path leading to the outside of the mold, thereby directly blocking the gas exhaust path. This allows you to quickly close the valve with great force.

That is, in this invention, the molten metal that has passed through the pressure reducing passage to the bottom of the valve collides with the bottom of the valve to directly line the valve. The kinetic energy of the molten metal due to the impact force, that is, the dynamic pressure of the molten metal, is used to directly line the valve.

In this case, the force to close the valve is proportional to the square of the speed at which the molten metal collides with the bottom of the valve, so it becomes a very large force (
・Ru.

Since the molten metal can be applied to the entire bottom surface of the valve, the force to close the valve is large, and the valve can be closed directly.
Since the gas exhaust passage is directly closed by the valve, the valve itself has a simple structure and is relatively light in weight, and the valve can be quickly closed to quickly, reliably, and easily close the gas exhaust passage.

In addition, according to this invention, the time required to close the valve is extremely short, about 5 m5 ec.

In addition, in this invention, the valve of the gas discharge passage is directly and instantaneously closed by the action of the inertial force of the molten metal.
There is no need to create resistance by narrowing the entrance or middle of the gas exhaust passage, also called a bypass, which leads from the pressure reduction passage to the side of the valve movement path, and there is no need to make this passage longer than necessary. Since it is simplified and can be made relatively wide, the degassing capacity is also large and degassing can be performed reliably.

In addition, the pressure reducing passage, the valve chamber containing the valve, the valve seat, etc. are arranged in series so that the direction in which the molten metal hits the valve and the valve moves matches the direction of the flow of the molten metal. Since the surface that strikes the valve faces the flow direction of the molten metal, a large closing force acts quickly on the valve.

In the first place, gas is sufficiently vented from the mold cavity during injection to prevent the formation of cavities in the injection product, and to achieve a satisfactory temperature.
In order to continue the injection operation, sufficient gas can escape from the valve part, but it is necessary to prevent the molten metal from flowing outside. Keep the valve open until you approach the valve seat, which is the opening part of the valve, and when the gas has fully escaped, close the valve quickly (in other words, it is necessary to close it in a very short time). However, in the present invention, as described above, this operation can be performed reliably and easily, and can be performed repeatedly for each injection.

Further, in the present invention, since the valve itself is made of one piece and is simple, the structure of the entire degassing device is relatively simple, and maintenance and inspection are easy.

In addition, if a seat type valve is used that is pressed against a valve seat with an inclined surface, the seal will be reliable, the operating resistance will be small, the molten metal will not be boring, and it will not be affected by thermal expansion. The operation is stable and reliable, and the structure is relatively simple, easy to manufacture, and inexpensive.

[Brief explanation of the drawing]

The drawing is a schematic diagram showing one embodiment of an apparatus used to carry out the method of the present invention. 1... Fixed mold, 2... Cavity,
3... Decompression passage (first passage), 4...
・Bypass (second passage), 5... Cylindrical body, 5b
...Opening (third passage), 6, 12...
...Cylinder, 7...Valve, 8...Spring, 9...Piping, 10...Reducing cylinder.

Claims (1)

[Scope of Claims] 1. Injection is performed by opening the pressure reducing passage leading from the mold cavity to the pressure reducing circuit outside the mold by the action of a valve. A reduced-pressure die-casting method in which the inertial force of the melt to be injected that has progressed from the injected melt directly acts on the valve, thereby moving the valve and directly blocking the reduced-pressure passage and the reduced-pressure circuit with this valve. 2. At the abutting surface of the mold, a valve is provided at the end of the first passage for pressure reduction led from the cavity, and is slidable in the axial direction of the end of the first passage, Said first
A second passage for depressurization is provided that communicates from the passage to the side surface of the valve movement path, and a pressure reduction passage that communicates from the side surface of the valve movement path, which is the end of the 20th passage, to the outside of the mold. A third passageway is provided, and the valve has a surface portion that allows communication and isolation between the second passageway and the third passageway by sliding. A valve is provided with one end surface capable of receiving the inertial force of the molten material to be injected advancing through the passage intersecting the axial direction of the end of the first passage, and a pressure reducing device is provided in the third passage. Connected vacuum die casting equipment.