JP2565007B2 - Pressure casting equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure casting apparatus for depressurizing a cavity of a mold and then pressurizing a molten metal poured into the cavity.

[0002]

2. Description of the Related Art In order to improve the internal quality of a casting, a pressure casting method in which the molten metal to be poured into the cavity is pressurized after depressurization in the cavity of the mold is disclosed in, for example, JP-A-62-114761. It is disclosed in the publication. In the pressure casting method, decompression in the cavity is performed by a so-called decompression pump such as a vacuum pump. However, decompression only by the decompression pump takes time until the pressure is reduced to a predetermined pressure. Therefore, a device as shown in FIG. 9 is adopted.

FIG. 9 shows a pressure casting apparatus for decompressing the inside of a cavity using a reservoir tank. In the figure,
Reference numeral 1 denotes a mold, and 2 denotes a cavity of the mold 1. The mold 1 can communicate with the decompression pump 4 via the communication passage 3. A switching valve 5 and a reservoir tank 6 are arranged in series in the communication passage 3. In this device, in order to quickly reduce the pressure in the cavity 2, the pressure in the reservoir tank 6 is reduced by the pressure reducing pump 4 with the switching valve 5 closed in advance. When the pressure inside the reservoir tank 6 is sufficiently reduced, the switching valve 5 is opened,
The air existing in the cavity 2 of the mold 1 is sucked into the reservoir tank 6, so that the pressure in the cavity 2 is quickly reduced. In this way, by using the reservoir tank 6, as shown in FIG. 10, the depressurization speed at the initial stage of depressurization can be increased as compared with the case of the depressurizing method using only the depressurizing pump.

[0004]

However, when the pressure in the cavity is reduced by simply using the reservoir tank, the following problems occur. In other words, by using the reservoir tank, the decompression rate at the initial stage of decompression can be increased, but in the latter half of decompression, the volume inside the reservoir tank must also be reduced by the decompression pump. The speed becomes slow. Therefore, the depressurizing work in the cavity cannot proceed at the same time as other work, and a work waiting time occurs in the casting work. Since the occurrence of this waiting for work causes a deterioration in production efficiency, it is desired to shorten the depressurizing work in the cavity.

In view of the above problems, the present invention provides a pressure casting apparatus capable of shortening the depressurization work in the cavity by increasing the depressurization rate in the cavity both in the initial stage of depressurization and in the latter stage of depressurization. With the goal.

[0006]

According to the present invention, there is provided a pressure casting apparatus, in which a cavity of a mold is depressurized by a reservoir tank to which a depressurizing pump is connected, and then the molten metal is poured into the cavity. In a pressure casting apparatus adapted to pressurize a pressure reducing pump connected to a communication passage communicating the cavity with a reservoir tank, and a first pressure reduction pump disposed in the communication passage between the pressure reduction pump and the cavity.
Switching valve, a second switching valve arranged between the pressure reducing pump in the communication passage and the reservoir tank, and a second switching valve that closes the first switching valve when only the reservoir tank is depressurized. Is opened, both the first switching valve and the second switching valve are opened at the initial stage of starting the pressure reduction in the cavity, and the first switching valve is opened when the pressure in the cavity reaches a predetermined value. And a switching valve control means for closing the second switching valve.
It is equipped with.

[0007]

In the pressure casting apparatus configured as described above, first, the switching valve control means closes the first switching valve and opens the second switching valve. When the decompression pump operates in this state, the air in the reservoir tank is sucked by the decompression pump and the inside of the reservoir tank is decompressed. When the pressure in the reservoir tank is sufficiently reduced, the switching valve control means opens both the first switching valve and the second switching valve. In this state, the cavity of the mold is in communication with the decompression pump and the reservoir tank, and the air in the cavity is sucked by the decompression pump and the reservoir tank. Therefore, the decompression rate at the initial stage of decompression is increased.

When the pressure in the cavity reaches a predetermined value by the decompression pump and the reservoir tank, the switching valve control means opens the first switching valve and closes the second switching valve. That is, in this state, the communication between the cavity and the reservoir tank is blocked by the second switching valve, and the pressure in the cavity is reduced only by the pressure reducing pump. Therefore, in the latter half of depressurization, it is not necessary to depressurize the inside of the reservoir tank having a large capacity, and the depressurization rate in the latter half of depressurization can be increased.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of a pressure casting apparatus according to the present invention will be described below with reference to the drawings.

First Embodiment FIGS. 1 to 6 show a first embodiment of the present invention.
In the figure, 11 indicates a mold, and a cavity 12 is formed in the mold 11. The mold 11 has a cavity 1
The pressurizing means 14 for pressurizing the molten metal 13 poured into the inside 2 is connected. The inside of the cavity 12 of the mold 11 can communicate with the reservoir tank 16 via the communication passage 15. The volume of the reservoir tank 16 is significantly larger than the volume of the cavity 12. A decompression pump 17 that is rotationally driven by a motor (not shown) or the like is connected to the communication passage 15. The decompression pump 17 has a function of sucking air by rotational driving by a motor,
The motor is connected to control means (not shown).

A first switching valve 18 composed of an electromagnetic valve is arranged between the cavity 12 and the position where the pressure reducing pump 17 is connected in the communication passage 15.
The first switching valve 18 can be opened and closed by a switching valve control means 25 described later. A second switching valve 19 composed of an electromagnetic valve is arranged between the reservoir tank 16 and the position where the decompression pump 17 is connected in the communication passage 15. The second switching valve 19 is
It can be opened and closed by a switching valve control means 25 described later.

A first pressure sensor 20 for detecting a change in reduced pressure is provided between the reservoir tank 16 and the second switching valve 19 in the communication passage 15. The detection signal of the first pressure sensor 20 is input to the switching valve control means 25. A second pressure sensor 21 that detects a change in pressure reduction is provided between the first switching valve 18 and the second switching valve 19 in the communication passage 15. The detection signal of the pressure sensor 21 is input to the switching valve control means 25.

The switching valve control means 25 has a function of closing the first switching valve 18 and opening the second switching valve 19 when only the reservoir tank 16 is depressurized. Further, the switching valve control means 25 has a function of opening both the first switching valve 18 and the second switching valve 19 at the initial stage of starting the pressure reduction in the cavity 12. Further, the switching valve control means 25 opens the first switching valve 18 when the pressure in the cavity 12 detected by the first pressure sensor 20 and the second pressure sensor 21 reaches a predetermined value. , Second
It has a function of closing the switching valve 19 of. The switching valve control means 25 is composed of, for example, a programmable controller (sequencer) or a microcomputer.

Next, the operation of the first embodiment will be described. First, before starting the pressure reduction in the cavity 12, the first switching valve 18 is closed by the command signal from the switching valve control means 25, and the second switching valve 19 is closed.
Is opened. As shown in FIG. 2, the decompression pump 17 is rotationally driven in this state, and decompression in the reservoir tank 16 is started. When the inside of the reservoir tank 16 is brought into a high decompression state, a switching command is output from the switching valve control means 25 based on the signal of the first pressure sensor 20, the first switching valve 18 is opened, and the first switching valve 18 is opened. 2 switching valve 19
Remains open. As shown in FIG. 3, in this state, the inside of the cavity 12 is in communication with the inside of the decompression pump 17 and the reservoir tank 16, and the air inside the cavity 12 is sucked by the decompression pump 17 and the reservoir tank 16. Thus, since the pressure is reduced by the two pressure reducing means at the initial stage of the pressure reduction, the cavity 12
The decompression rate inside is increased.

Decompression pump 17 and reservoir tank 16
When the switching valve control means 25 determines that the pressure values from the first pressure sensor 20 and the second pressure sensor 21 have reached the predetermined value P, the switching valve control means 25 issues a command. The signal causes the second switching valve 19 to close and the first switching valve 18 to remain open. This state is shown in FIG. In this state,
The communication between the cavity 12 and the reservoir tank 16 is blocked by the second switching valve 19, and the pressure inside the cavity 12 is reduced only by the pressure reducing pump 17. Therefore, the decompression pump 17 does not need to further decompress the inside of the reservoir tank 16 having a large capacity, and the decompression speed in the latter period of decompression can be increased.

As described above, in this embodiment, the initial pressure reduction is 5
The reservoir tank 16 is communicated with the cavity 12 only for ~ 6 seconds, the decompression effect of the reservoir tank 16 is utilized, and thereafter, the communication between the cavity 12 and the reservoir tank 16 is cut off, thereby further reducing the pressure of the reservoir tank 16. It has disappeared. The switching of the second switching valve 19 to the closed valve is based on a time point P when the pressure values from the pressure sensors 20 and 21 are monitored by the switching valve control means 25 and the pressure values become equal.

FIG. 6 shows changes in the reduced pressure in the cavity 12. As shown in the figure, the decompression speed is increased 5 to 6 seconds after the decompression is started, and the time required for the decompression value to reach 750 mmHg is 25 to 30 times as compared with the conventional case.
Seconds have been shortened. For example, in the past, a cycle time of about 90 seconds was required to cast the underbody parts of a vehicle, but by using the apparatus of this embodiment,
It has become possible to reduce the cycle time to 60 seconds.

When the pressure in the cavity 12 of the mold 11 is reduced to a predetermined value, the molten metal 13 is poured into the cavity 12, and the molten metal 13 in the cavity 12 is pressurized by the pressure means 14. This prevents the occurrence of casting defects and improves the quality of castings.

Second Embodiment FIGS. 7 and 8 show a second embodiment of the present invention.
The second embodiment is different from the first embodiment only in the presence or absence of the second pressure sensor, and the other parts are the same as those in the first embodiment. Therefore, the corresponding parts are designated by the same reference numerals as those in the first embodiment. Therefore, the description of the corresponding parts will be omitted, and only different parts will be described. In the first embodiment, two pressure sensors are used to detect the pressure at two locations, but in this case the structure is complicated and the pressure changes rapidly, which is likely to cause a malfunction. Therefore, if the switching valves 18 and 19 are controlled by one pressure sensor, the configuration is simplified and malfunctions are eliminated.
Then, as a result of an experiment on the control of the switching valve by one pressure sensor, it was found that the control based on the pressure value of the first pressure sensor 20 has substantially no problem.
Therefore, in the case of this embodiment, as shown in FIG. 7, the second pressure sensor 21 is omitted from the configuration of the first embodiment.

FIG. 8 shows the time required for decompression when the switching valves 18 and 19 are controlled based on the pressure value from the first pressure sensor 20. Second switching valve 19
The pressure reduction value for closing the valve is changed between 550 and 650 mmHg, and the pressure inside the cavity 12 is reduced to 750 mmHg or more.
As a result of measuring the time to reach 585-605m
It has been found that when the second switching valve 19 is closed at about mHg, the pressure reduction is fastest. Further, as is clear from FIG. 8, it was found that the time required for depressurization is similar in the range of 585 to 605 mmHg, and that it is not very sensitive to changes in the depressurization value set for valve switching. Therefore, the result of casting with the pressure reduction value of the switching timing of the second switching valve 19 to the valve closing side set to 590 mmHg (the operation and control of the first switching valve 18 are exactly the same as in the first embodiment). The same effect as in the first embodiment was obtained, and the casting cycle time was shortened by about 30 seconds as compared with the conventional case.

In each of the above-mentioned embodiments, each switching valve is controlled based on the pressure reduction value from the pressure sensor. However, the same applies to a configuration in which each switching valve is temporally controlled by means of a timer or the like. Can be obtained.

[0022]

As described above, in the pressure casting apparatus according to the present invention, decompression is performed by the decompression pump and the reservoir tank at the initial stage of decompression in the cavity, and the decompression effect of the reservoir tank no longer occurs. In the latter half of the period, the switching valve is switched to reduce the pressure only by the decompression pump, so that it is possible to increase both the decompression speed in the early period of decompression and in the latter period of decompression. Therefore, the depressurization work in the cavity can be shortened and the work waiting time in the casting work can be prevented. As a result, the depressurizing work can proceed at the same time as other work, and the production efficiency in the casting work can be improved.

[Brief description of drawings]

FIG. 1 is a system diagram of a pressure casting device according to a first embodiment of the present invention.

FIG. 2 is a system diagram showing a depressurized state inside a reservoir tank in the apparatus of FIG.

FIG. 3 is a system diagram showing a switching state of the switching valve in the initial stage of depressurization in the apparatus of FIG.

FIG. 4 is a system diagram showing a switching state of the switching valve in the latter half of the depressurization in the apparatus of FIG.

5 is a characteristic diagram showing a change in a reduced pressure value detected by a pressure sensor in the apparatus of FIG.

FIG. 6 is a characteristic diagram showing changes in reduced pressure in the apparatus of FIG. 1 and a conventional apparatus.

FIG. 7 is a system diagram of a pressure casting device according to a second embodiment of the present invention.

8 is a characteristic diagram showing a change in decompression time with respect to a decompression value for switching the second switching valve in the apparatus of FIG.

FIG. 9 is a system diagram of a conventional pressure casting device.

10 is a characteristic diagram showing changes in reduced pressure by the apparatus of FIG.

[Explanation of symbols]

 11 Mold 12 Cavity 15 Communication Channel 16 Reservoir Tank 17 Decompression Pump 18 First Switching Valve 19 Second Switching Valve 20 First Pressure Sensor 21 Second Pressure Sensor 25 Switching Valve Control Means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-63-278658 (JP, A) JP-A-63-174772 (JP, A) JP-A-56-144855 (JP, A)

Claims (1)

(57) [Claims] 1. A pressure casting apparatus configured to pressurize the molten metal poured into the cavity after depressurizing the cavity of the mold with a reservoir tank connected to a depressurizing pump. And a first switching valve arranged between the decompression pump in the communication passage and the cavity, and arranged between the decompression pump in the communication passage and the reservoir tank. And a second switching valve that closes the first switching valve at the time of depressurizing only the reservoir tank and opens the second switching valve so that the first switching valve and the first switching valve are opened at the beginning of depressurization in the cavity. Both of the two switching valves are opened, and when the pressure in the cavity reaches a predetermined value, the first switching valve is opened and the second switching valve is closed. And a switching valve control means for enabling the pressure casting device.