JPH04158968A - Casting apparatus - Google Patents

Abstract

PURPOSE:To improve mass-productivity of castings by shutting an evacuating passage and opening a gate piston after completing the evacuation in cavity by shutting the gate piston and opening the shut pin to introduce molten metal in cavity. CONSTITUTION:The cavity 6 in a mold 1 and a molten metal storing vessel 13 are communicated with a supplying passage 8. The supplying passage 8 is opened/shut with the gate piston 36. The evacuating passage 24 is communicated with the supplying passage 8 and a vacuum source 18. Communicating part of the evacuating passage 24 and molten metal supplying passage 8 is opened/ shut with the shut pin 26. The evacuation in the cavity 6 is completed under condition of shutting the gate piston 30 and opening the shut piston 26. After that, the evacuating passage 24 is shut and the gate piston 30 is opened and the molten metal 12 is introduced into the cavity 6 and cast. By this method, cycle time per one shot for casting can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for casting by introducing molten metal stored in a hot water storage tank into a pre-depressurized cavity of a mold.

[Conventional technology]

JP-A-63-76749 discloses an apparatus for casting molten metal by introducing it into a reduced pressure cavity. In this device, a hot water supply stopper pin is installed in the passageway through which molten metal is introduced into the cavity, the pressure inside the cavity is reduced with the stopper pin closed, and then the hot water supply stopper pin is opened to introduce molten metal into the cavity.

An exhaust passage for evacuating the inside of the cavity is provided at the mold dividing surface (parting surface) between the upper mold and the lower mold, and exhaust is performed from the inside of the cavity through the minute gap between the upper mold and the lower mold. In this manner, by evacuation through the minute gap, the inside of the cavity can be evacuated, while molten metal is prevented from entering the exhaust passage.

[Problem to be solved by the invention]

However, in the above-mentioned conventional technology, an exhaust passage is opened in the mold dividing surface (parting surface) between the upper mold and the lower mold, and a structure is adopted in which the exhaust is exhausted through a minute gap in the parting surface. Prevents intrusion into the interior. Here, the parting surface is very narrow to prevent leakage of molten metal, and it takes a long time to reduce the pressure inside the cavity to a predetermined pressure.

As a result, the cycle time per casting shot becomes longer, reducing mass productivity.

The technical problem of the present invention is, based on the above knowledge, to provide a casting device that shortens the cycle time per casting shot by shortening the depressurization time in the cavity and has excellent mass productivity. .

[Means to solve the problem]

The above problem is solved by the casting apparatus of the present invention described below.

That is, the casting apparatus according to the present invention has a cavity provided in a mold and into which molten metal is introduced to form a product.

Furthermore, it has a molten metal supply passage that connects the cavity to a molten metal storage tank.

Furthermore, it has a gate piston that opens and closes the molten metal supply passage.

Furthermore, it has an exhaust passage that communicates with the molten metal supply passage on the side closer to the cavity than the gate piston and communicates with the vacuum source at the other end.

Furthermore, it has a shut pin that opens and closes a communication portion between the exhaust passage and the molten metal supply passage.

Then, the gate piston is closed and the inside of the cavity is evacuated with the nyat pin opened, and after the exhaust is completed, the exhaust passage is closed, the gate piston is opened, and molten metal is introduced into the cavity. casting.

[For production]

According to the present invention, when the gate piston is opened and molten metal is introduced into the cavity, the communication part of the exhaust passage is closed by the shut pin, so that molten metal does not enter the exhaust passage. . Therefore, the exhaust passage can be made of a necessary and sufficient size, and the pressure inside the cavity can be quickly reduced.

〔Example〕

Hereinafter, embodiments will be specifically described with reference to the drawings.

FIG. 1 is a sectional view of a casting apparatus according to a first embodiment of the present invention.

The casting apparatus according to this embodiment is an example of an apparatus in which molten metal is introduced into the cavity 6 while the pressure inside the cavity 6 is reduced, and the molten metal is further cast while being pressurized.

In the figure, -1 is a mold, which is composed of an upper mold 2 and a lower mold 4, and is provided with a cavity 6 and a molten metal supply passage 8 for supplying molten metal to the cavity 6.

The end of the molten metal supply passage 8 opposite to the cavity 6 is connected to the lower mold 4.
It opens to the outside at the lower end. A cylindrical stalk 1 is inserted into this opening 8b via a heat-resistant sealing material 9.
0 is connected.

The tip of the stalk 10 is connected to a melting furnace 1 that functions as a hot water storage tank.
It is immersed in molten aluminum alloy 12 stored in 3.

Further, a groove 3a is formed in the mating surface 3 of the upper die 2 and the lower die 4, and a heat-resistant comb O-ring 3b is inserted into this groove 3a. Thereby, when the mold 1 is closed, the airtightness of the cavity 6 and the molten metal supply passage 8 is ensured.

In the figure, 18 is a vacuum pump that functions as a vacuum source. The vacuum pump 18 communicates with a gas chamber 22 provided inside the upper mold 2, and the gas chamber 22 also connects to the cavity 6 via an exhaust passage 24, a cylinder 27, and a molten metal supply passage 8.
It communicates with

The exhaust passage 24 drains the gas in the cavity 6 to the vacuum pump 18.
This is a passage provided to lead the air to the air, and its diameter is set to 15 mm in consideration of the suction capacity of the vacuum pump 18. In addition, a sintering vent 25 having a pore (approximately 0.4 mm) that allows only ventilation is provided at the end of the exhaust passage 24 on the cylinder 27 side to prevent the molten aluminum alloy 12 from entering the passage 24. It is being

The shut pin 26 is movably provided in the cylinder 27 and closes the exhaust passage 24 when the molten aluminum alloy 12 is introduced into the cavity 6, and also closes the exhaust passage 24 and the molten metal supply passage 8 during pressure casting. It functions to prevent the molten aluminum alloy 12 from leaking from the cavity 6 by closing the cavity 6. During pressure casting, the molten aluminum alloy 12 in the cavity 6 is subjected to high pressure (200~
1000kg/cnf), the shut pin 2
6 has the mechanical strength to withstand this pressure.

Details of the shut pin 26 and cylinder 27 are shown in FIG.

The shut pin 26 includes a piston-shaped valve body portion 26a (diameter D=35 mm) at the tip of a shaft portion 26b, and the other end of the shaft portion 26b is connected to a drive portion (not shown). When the drive section is operated at a predetermined timing, the valve body section 26a slides in the cylinder 27 provided inside the upper mold 2 in the vertical direction in the figure. Here, a clearance A of about 0.2 mm is provided between the inner wall surface of the cylinder 27 and the valve body part 26a, taking into consideration the expansion of the valve body part 26a due to heat. Further, the exhaust passage 2
4 communicates with the cylinder 27 from the right angle direction,
The communication position is set at about 15 mm from the upper surface of the molten metal supply passage 8.

With this structure, the valve body part 26a moves to the lowest part, and the lower end of the valve body part 26a becomes the bottom surface (valve seat surface) of the molten metal supply passage 8.
26c, the exhaust passage 24 and the molten metal supply passage 8 are closed from the cavity 6. In addition, the valve body part 2
6a is raised and the lower end of the valve body portion 26a is substantially aligned with the upper surface of the molten metal supply passage 8, and the molten metal supply passage 8 is opened while the exhaust passage 24 remains closed. Furthermore, the valve body part 2
6a is raised and the lower end of the valve body portion 26a is higher than the opening 24a of the exhaust passage 24, at which point the exhaust passage 24 and the molten metal supply passage 8 are opened.

That is, the shut pin 26 functions as a means for closing the exhaust passage 24 and the molten metal supply passage 8.

30 in FIG. 1 indicates the melting furnace 13 from the shut pin 26.
A gate piston is provided on the side.

The gate piston 30 is for closing the molten metal supply passage 8 and the cavity 6 when the pressure inside the cavity 6 is reduced by the vacuum pump 18, and serves to prevent outside air from flowing into the cavity 6. . For this reason, high airtightness is required when closing.

The gate piston 30 includes a piston-shaped valve body portion 30a at the tip of a shaft portion 30b, and the other end of the shaft portion 30b is connected to a drive portion (not shown). Then, by operating the drive section at a predetermined timing, the valve body section 3
0a slides in a cylinder 31 provided inside the upper mold 2 in the vertical direction in the figure to open and close the molten metal supply passage 8. That is,
The valve body portion 30a moves to the lowest position and the lower end of the valve body portion 30a comes into contact with a valve seat 30c provided in the molten metal supply passage 8, thereby closing the molten metal supply passage 8. As aforementioned,
The contact surface between the lower end surface of the valve body portion 30a and the valve seat 30c is made smooth because high airtightness is required.

Here, from the valve body part 30a of the gate piston 30 to the shaft part 3
0b, a passage 33 is provided inside, and the opening of the passage 33 on the valve body 30a side is connected to the gate piston 3.
0 closes the molten metal supply passage 8, the molten metal supply passage 8
The opening of the passage 33 on the shaft portion 30b side communicates with a vacuum pump 32 located outside the mold l.

Note that the exhaust passage 2 is connected to the opening of the passage 33 on the side of the valve body 30a.
4, a sintering vent 33a having pores is provided to prevent the molten aluminum alloy 12 from entering.

In the figure, 40 is a pressure member for pressurizing the molten aluminum alloy 12 drawn into the cavity 6. The pressure member 40 is equipped with an electric heater 42 inside, and the heat from this heater delays the solidification of the molten aluminum alloy 12 around the pressure member 40, so that the pressure applied by the pressure member 40 is efficiently applied to the surrounding area. communicated.

In the figure, 50 is an extrusion pin for demolding the casting.

The extrusion pin 50 is a rod-shaped pin with a diameter of 10 mm, and in this embodiment, the shut pin 26 is the most difficult to demold.
is installed on the valve seat surface 26c.

Next, the functions of the pressure casting apparatus according to this embodiment will be explained.

FIGS. 2(a) to 2(d) show the casting process using the casting apparatus according to this embodiment.

First, with the mold 1 closed, the valve body 26a of the shut pin 26 is raised to open the exhaust passage 24, as shown in FIG. 2(a). Furthermore, the gate piston 30
The valve body portion 30a is lowered and comes into contact with the valve seat 30c, and the molten metal supply passage 8 is closed. Then, the vacuum pump 18 is driven.

In this state, the gas inside the cavity 6 is transferred to the molten metal supply passage 8.
The air is sucked into the vacuum pump 18 via the sintering vent 25, the exhaust passage 24, and the gas chamber 22, and the pressure inside the cavity 6 is reduced. Here, the reduced pressure inside the cavity 6 is the pressure inside the cavity 6 or about 10 mmHg (degree of reduced pressure is about 750
mmHg).

And the degree of reduced pressure inside cavity 6 is about 750 mmtl
After reaching g, the decompression pump 32 is driven.

Therefore, the space from the gate piston 30 to the molten metal supply passage 8 and the stalk 10 is depressurized by the decompression pump 32 via the passage 33 formed in the gate piston 30. Here, the pressure reduction by the pressure reduction pump 32 is stoke 1
The process is continued until the pressure within 0 reaches approximately 400 mmt1g. As a result, the molten aluminum alloy 12 stored in the melting furnace 13 is sucked from the stalk IO,
The molten metal reaches the position of the gate piston 30 via the molten metal supply passage 8 and is held at this position by suction.

Next, as shown in FIG. 2(b), the valve body portion 26a of the bottom pin 26 is lowered to a position where it closes the exhaust passage 24 while opening the molten metal supply passage 8.

Then, after the communication part of the exhaust passage 24 is closed, the second
As shown in Figure (C), the valve body portion 3 of the gate piston 30
0a rises and the molten metal supply passage 8 is opened.

This allows the aluminum alloy melt to be sucked and held at the position of the gate piston 30 in advance. M12 is sucked into the cavity 6. Here, since the exhaust passage 24 is closed by the shut pin 26, the molten aluminum alloy 12 does not enter the exhaust passage 24.

When the inside of the cavity 6 is filled with the molten aluminum alloy 12 in this way, the valve body portion 26a of the shut pin 26 is further lowered to the valve seat surface 26c, as shown in FIG. 2(d). They come into contact and close the molten metal supply passage 8. Further, at the same time, a valve (not shown) located outside the mold 1 communicates the passage 33 of the gate piston 30 with the atmosphere, and air enters the molten metal supply passage 8 between the shut pin 26 and the melting furnace 13 and the stalk 10. Allows for influx. As a result, the inside of the cavity 6 is kept sealed, and no suction force is applied to the molten aluminum alloy 12 filling the molten metal supply passage 8 and the stoke 10 between the shut pin 26 and the melting furnace 13. The molten aluminum alloy 12 flows out to the melting furnace 13 side due to its own weight.

In this state, the molten aluminum alloy 12 in the cavity 6 is applied to a predetermined pressure (200 to 200
Casting is performed under pressure of 1000 kg/c♂).

As described above, in the casting apparatus according to this embodiment, the cavity 6 and the vacuum pump 18 are communicated with each other by the exhaust passage 24 having a diameter corresponding to the suction capacity of the vacuum pump 18. For this reason, the efficiency of exhausting the gas in the cavity 6 is high, and as shown by the solid line in FIG.
The time required to reach mmt (g) is a little less than 20 seconds. Therefore, compared to the conventional method of exhausting the gas in the cavity 6 via the parting surface of the mold 1 (dotted line in FIG. 4), the decompression time is shortened by about 40 seconds.

Therefore, the cycle time per casting shot is shortened, and mass productivity is improved.

Further, a gate piston 30 that closes the molten metal supply passage 8 to reduce the pressure inside the cavity 6 and a shut pin 26 that closes the molten metal supply passage 8 during pressure casting are provided separately. gate piston 3
It is installed at a position closer to cavity 6 than 0. For this reason, the gate piston 30 has a structure in which high pressure during pressure casting is not applied. In addition, since the molten metal supply passage 8 is not closed off by the gate piston 30 after pouring, and the molten aluminum alloy 12 is not pushed down, aluminum debris stuck to the valve seat 30c of the gate piston 30 can be easily removed. Will not damage 30c.

Therefore, the valve body portion 30a of the gate piston 30 and the valve seat 3
Good sealing performance between 0c and 0c can be maintained for a long period of time.

FIG. 5 shows the relationship between the number of shots and the final vacuum degree within the cavity 6 when 30 shots are continuously cast. The dotted line in the figure shows the characteristics of a conventional casting apparatus in which a single hot water supply stopper pin 6 serves as both the shunt pin 26 and the gate piston 30.

In the case of conventional casting equipment, the sealing performance of the hot water supply stopper pin 6 deteriorates after the number of casting shots exceeds 10, and the inside of the cavity 6 reaches a predetermined pressure (approximately 10 mmHg).
In other words, the degree of reduced pressure (approximately 750 mmHg) must not be reached (
It has become. On the other hand, the casting apparatus according to this embodiment has
In order to maintain good sealing performance between the valve body portion 30a and the valve seat 30c of the gate piston 30 over a long period of time,
Even if the number of shots exceeds 30, the inside of the cavity 6 is kept at a predetermined pressure (approximately 10 mmHg, that is, the degree of vacuum is approximately 750
It is possible to reduce the pressure to (mmHg), and casting can be carried out well.

FIG. 6 is an opening view of the shut pin 26 side of the exhaust passage 24 used in the casting apparatus according to the second embodiment of the present invention.

In the casting apparatus according to this embodiment, a groove 27a having a rectangular cross section is provided on the inner wall surface of the cylinder 27, and the exhaust passage 24 is communicated with the upper surface of the groove 27a. Here, groove 27
The position a is about 15 mm from the top surface of the molten metal supply passage 8.

With this structure, even if the molten aluminum alloy 12 enters between the valve body part 26a of the shut pin 26 and the inner wall surface of the cylinder 27 during pressure casting and foil-like aluminum debris is generated, this aluminum debris will be removed. Due to the presence of the groove 27a, it does not directly adhere to the opening of the exhaust passage 24, more specifically, to the sintered vent 25 provided in the opening. Therefore, the problem of clogging of the exhaust passage 24 does not occur, and the exhaust passage 24 is maintained in a good ventilation state for a long period of time. Thereby, the pressure inside the cavity 6 is stably reduced.

In the casting apparatus according to this embodiment, the final degree of reduced pressure does not decrease even in a continuous cycle of 100 shots.
Stable casting was achieved.

[Effects of the Invention] According to the present invention, the pressure inside the cavity is quickly reduced, and the pressure reduction time is shortened. This shortens the cycle time per casting shot and improves the mass productivity of castings.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a casting apparatus according to a first embodiment of the present invention;
FIG. 2 is a casting process diagram using the casting apparatus according to the first embodiment;
FIG. 3 is a detailed view of the main part of the shut pin 26, FIG. 4 is a characteristic diagram of the reduced pressure inside the cavity 6, FIG. 5 is a diagram showing the relationship between the number of casting shots and the final degree of reduced pressure inside the cavity 6, and FIG. Exhaust passage 24 in the casting apparatus according to the second embodiment of the present invention
FIG. 1... Mold 6... Cavity 12... Molten aluminum alloy (molten metal) 13...
・Melting furnace (hot water storage tank) 18... Vacuum pump (vacuum source) 24... Exhaust passage 26... Shut pin 30... Gate piston

Claims (1)

[Scope of Claims] A cavity provided in a mold for introducing molten metal to mold a product, a molten metal supply passage communicating the cavity with a molten metal storage tank, and a gate piston for opening and closing the molten metal supply passage. an exhaust passage that communicates with the molten metal supply passage on a side closer to the cavity than the gate piston and whose other end communicates with a vacuum source; and a shut pin that opens and closes a communication portion between the exhaust passage and the molten metal supply passage. Then, the inside of the cavity is evacuated with the gate piston closed and the shut pin opened, and after the exhaust is completed,
A casting apparatus characterized in that the exhaust passage is closed, the gate piston is opened, and molten metal is introduced into the cavity for casting.