JPH1015657A - Method and device for detecting molten metal surface in vacuum suction casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep vacuum degree constant by feeding back the actual flowing value to the preset suction flowing value thereby controlling a flow rate adjusting means, approaching molten metal to a mold housing chamber and detecting pressure variation caused at the time of bringing a sprue into contact with the molten metal surface. SOLUTION: When the sprue 19 reaches the molten metal surface, the atmosphere flowing in the mold housing chamber 2 through the sprue 19 and the mold 1 is shut off and the vacuum degree in the mold housing chamber 2 is increased by the flowing quantity. At the time of detecting the pressure variation by a pressure sensor 9, a control part 10 judges that the sprue 19 has already reach the molten metal surface, the the pressure is dropped by prescribed quantity, e.g. by the quantity corresponding to the suction to complete the molten metal surface detecting mode. Thereafter, the actual suction mode is started. In the actual suction mode, the vacuum degree is controlled by executing a PID control based on the actual detected pressure by a processor sensor 9 and outputting an operational signal to both of an analog flow rate control valve 5 and a digital valve 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION In vacuum suction casting, in which a casting is cast by reducing the pressure in a mold cavity to below atmospheric pressure and sucking and filling the molten metal into the cavity, detection of the molten metal surface is automatically performed. A method and apparatus for performing the method.

[0002]

2. Description of the Related Art The applicant has previously filed an application for a method for detecting a molten metal level in a vacuum suction casting method. This is achieved by disposing a mold in a mold storage chamber having a molten metal suction opening so that a spout projects from the molten metal suction opening of the mold storage chamber, and depressurizing the mold storage chamber to an atmospheric pressure or less. In a vacuum suction casting method in which a molten metal is filled into a cavity from a gate through a runner, after the mold is placed in the mold storage chamber, the mold storage chamber is lowered onto the molten metal while the interior of the mold container is weakly sucked and depressurized. When the gas comes into contact with the surface of the molten metal, the air flow previously sucked from the gate is shut off, and the pressure in the mold storage chamber decreases. The pressure fluctuation is detected by a pressure sensor to detect that the tip of the gate reaches the surface of the molten metal. Things. When the lowering of the mold storage chamber is stopped by this signal, the mold storage chamber is further depressurized and the molten metal is sucked into the cavity for casting.

[0003]

When the tip of the gate that protrudes from the mold storage chamber reaches the molten metal, the mold storage chamber is closed and the degree of decompression inside the mold storage chamber is increased. The degree of pressure reduction that does not reach the temperature and that allows the control unit to recognize the change is appropriate. For this reason, when depressurizing the mold storage chamber, it is necessary to suction a predetermined amount of flow rate. However, in the above-described conventional method for detecting a molten metal level, the flow control valve is controlled in an open loop in response to an opening command from the control unit. May not correspond exactly to the value. In such a case, the degree of pressure reduction in the mold storage chamber when the mold storage chamber is in a closed state fluctuates. For example, when the degree of decompression is too high, the molten metal reaches the cavity. Conversely, when the degree of decompression is low and a sufficient pressure change does not occur, the mold storage chamber does not stop descending and enters the molten metal. It will be immersed.

[0004]

According to the present invention, a mold having a runner and a cavity communicating with the runner is provided with a mold in a mold storage chamber having a molten metal suction opening and a decompression opening. In the method for detecting the level of the molten metal in vacuum suction casting in which the molten metal is arranged so as to protrude from the molten metal suction opening and the pressure is reduced from the reduced pressure opening to fill the cavity with the molten metal from the gate,
For the preset suction flow rate value, the actual flow rate value is fed back to control the flow rate adjusting means, and the mold storage chamber is brought close to the molten metal while discharging a predetermined flow rate from the mold storage chamber, and the gate is in contact with the molten metal surface. It is characterized by detecting pressure changes that occur at times.

Further, a mold having a runner and a cavity communicating with the runner projects into a mold storage chamber having a melt suction opening and a depressurization opening from a melt suction opening of the mold storage chamber. In the molten metal level detecting device in the vacuum suction casting in which the pressure is reduced from the pressure reducing opening and the molten metal is filled into the cavity from the gate, provided in a pipe communicating the pressure reducing opening of the mold storage chamber and the vacuum exhaust device. Flow rate adjusting means and flow rate detecting means, and a control device for outputting a difference between the set flow rate value and the detected flow rate value to the flow rate adjusting means, inputting a pressure value in the mold housing chamber and identifying a pressure change. .

[0006]

FIG. 1 shows an embodiment of the present invention. The mold 1 is made of a gas-permeable material, and has a cavity 14 corresponding to the shape of a cast product and a runner 15 communicating with the cavity 14 therein. The mold accommodating chamber 2 has a structure in which the mold 1 can be sealed from the outside air and can be accommodated. The mold accommodating chamber 2 has a sluice suction opening 17 at the bottom. The upper part has a decompression opening 18 through which a pipe 11 for depressurizing and suctioning the mold storage chamber 2 is inserted. The mold storage chamber 2 can be moved up and down by a lifting device (not shown). A vacuum pump 7 is provided at the other end of the pipe 11, and a flow rate measuring device 4 is provided at a position close to the pressure reducing opening 18, and a control is provided between the flow rate measuring device 4 and the vacuum pump 7. An analog flow control valve 5 capable of continuously producing a predetermined fluid resistance in response to a signal from the section 10 is provided. Further, a digital valve 6 (Hitachi Metals Co., Ltd.) having a branch pipe provided in the middle of the pipe 12 between the analog flow control valve 5 and the flow meter 4 and having one end open to the atmosphere.
Product name). Further, the pressure sensor 9 is provided on the pipe 11 on the mold 1 side from the pipe 12 or on the upper part of the mold storage chamber 2. The opening and closing of the analog flow control valve 5 and the digital valve 6 are controlled by a control unit 10. The control unit 10 can input the output from the pressure sensor 9 and the flow measuring device 4 and adjust the analog flow control valve 5 and the digital valve 6.

Next, based on the above configuration, the operation is shown in FIG.
This will be described with reference to FIGS. 2, 3 and 4. When the vacuum suction casting apparatus is started, the vacuum pump 7 is operated. The control unit 10 closes the analog flow control valve 5 and the digital valve 6 so that the mold storage chamber 2 is under the atmospheric pressure environment.
Open. Next, when the mold 1 is hermetically accommodated in the mold accommodating chamber 2, the signal is received and a cycle of the reduced pressure suction control is started. The reduced pressure suction control includes a water level detection mode and an actual suction mode.

[0008] When entering the molten metal level detection mode, a predetermined small amount of air flows from the gate 19 so as to be secured.
The analog flow control valve 5 is controlled so as to be slightly opened, and the digital valve 6 is controlled so as to be kept open or slightly closed. That is, the flow rate value from the flow rate measuring device 4 is
If this value does not fall within the set range, the same PID adjustment as in the actual suction mode described later is performed, and the opening of the analog flow rate control valve 5 and the digital valve 6 is adjusted.

When the flow rate value is smaller than the set range, the analog flow control valve 5 is slightly opened, and the digital valve 6 is slightly closed or kept open at the same time. The control valve 5 is slightly closed, and the digital valve 6 is slightly opened or kept open. If the flow rate value is within the range specified in advance, the lowering of the mold storage chamber 2 is started as shown in FIG.
Start monitoring the pressure value. At this time, the detection value of the pressure sensor 9 is as small as about -1000 Pa, for example, as shown in part A of FIG. It should be noted that the air permeability of the mold 1 is slightly different for different types, and in this case, the detection value of the pressure sensor 9 also changes accordingly.

When the gate 19 reaches the molten metal surface as shown in FIG. 2 (b), the mold storage chamber 2 passes through the gate 19 and the mold 1.
The atmosphere flowing into the mold is shut off, and the degree of pressure reduction in the mold storage chamber 2 is increased by the flow rate (for example, about -3000P).
a). That is, the flow rate to be set is set to an amount such that a predetermined degree of pressure reduction is obtained when the mold storage chamber is evacuated to a corresponding degree. When this pressure change is detected by the pressure sensor 9 (part B in FIG. 4), the control unit 10 determines that the gate 19 has reached the molten metal level, and further lowers it by a predetermined amount, for example, by the amount corresponding to suction. Complete. Thereafter, the actual suction mode is started. FIG. 3 shows a flowchart from the molten metal level detection mode to the actual suction mode.

In the actual suction mode, the degree of pressure reduction is controlled by performing PID adjustment based on the pressure detected by the actual pressure sensor 9 and outputting an operation signal to both the analog flow rate control valve 5 and the digital valve 6 for control. At this time, the analog flow control valve 5 outputs the analog voltage or current converted into the opening / closing operation signal. In order to increase the degree of pressure reduction, the analog flow control valve 5 is opened, and the exhaust in the mold storage chamber 2 may be increased. That is, from 0% to 100 from the PID adjustment unit
In response to the output value change to%, an operation signal is output so as to open the valve proportionally from fully closed to fully open.

On the other hand, the digital valve 6 outputs an ON-OFF signal to each of a plurality of solenoid valves of the digital valve 6 corresponding to the output value of the PID-adjusted operation signal from 0 to 100%. To increase the degree of pressure reduction, the digital valve 6 may be closed to reduce the amount of inflow of air. That is, P
In accordance with the output value from 0% to 100% of the ID-adjusted operation signal, calculation and judgment processing are performed so that the opening degree of the entire valve is closed in a stepwise but proportional manner from full open to full close. ,
An operation signal is output to each of the plurality of solenoid valves.

Since the opening of the digital valve 6 is opened and closed by an electromagnetic valve, the opening area can be adjusted with an extremely high responsiveness in 0.01 seconds. That is, in response to a rapid pressure reduction instruction, the amount of air flowing in is reduced instantaneously, and the target pressure reduction curve can be followed. Furthermore, the amount of inflow can be instantaneously increased with respect to the overshoot after reaching the predetermined pressure, and the amount of overshoot can be almost eliminated. On the other hand, although the analog flow control valve 5 has poor responsiveness, the flow rate can be changed gently, and the flow rate of the digital valve 6 can be changed smoothly. Therefore, due to the synergistic effect of the two valves, the decompression can be quickly raised, and the target value can be reached without a large hunting. Can be maintained. FIG. 4 shows the change in the reduced pressure suction pressure from the start of the reduced pressure to the constant pressure in the present embodiment, but the target value is not excessively increased irrespective of the rapid reduced pressure speed (part C) of about 0.04 MPa / sec. You can see that he is calm down.

By the above-described pressure reduction control, the molten metal 3 is rapidly filled in the cavity 14 of the mold 1 without solidifying even in contact with the mold, and solidifies under a certain suction force. After a predetermined time after the completion of the solidification, the analog flow control valve 5 and the digital valve 6 are returned to the open / close positions in the initial state, and the inside of the mold storage chamber 2 is set to the atmospheric pressure to complete the reduced pressure suction control cycle. Thereafter, the mold storage chamber 2 is raised, the mold 1 is taken out of the mold storage chamber 2, and the casting is completed.

[0015]

According to the method and the apparatus for detecting the molten metal level in the vacuum suction casting of the present invention, the above-described means are used, and the following effects are obtained. 1) The degree of pressure reduction in the mold storage chamber when the gate is closed with the molten metal is determined by the preset amount of inflow of air, so that the degree of decompression can be kept constant, and the flow of molten metal into the cavity and the detection of pressure changes are detected. There are no mistakes. 2) Since the flow rate of the air is controlled by feeding back the flow rate value of the flow meter, a predetermined flow rate can be obtained. 3) The level of the molten metal can be detected using a decompression controller without using a molten metal level meter or the like, and the peripheral equipment can be simplified.

[Brief description of the drawings]

FIG. 1 is a view for explaining a vacuum suction casting apparatus of the present invention.

FIG. 2 is a diagram for explaining the concept of the principle of detecting a molten metal level;

FIG. 3 is a flowchart illustrating reduced pressure suction control.

FIG. 4 is a diagram showing an example of a change in reduced-pressure suction pressure.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mold 2 mold storage chamber 3 molten metal 4 flow meter 5 analog flow control valve 6 digital valve 7 vacuum pump 9 pressure sensor 10 control unit 14 cavity 15 runner 16 gate section 19 … Gate

Claims (2)

[Claims] 1. A mold having a runner and a cavity communicating with the runner is protruded from a mold storage chamber having a molten metal suction opening and a depressurization opening. In the method for detecting the level of the molten metal in the vacuum suction casting in which the cavity is filled with the molten metal from the gate by reducing the pressure from the vacuum opening, the actual flow value is fed back to a preset suction flow value. Controlling the adjusting means to discharge the predetermined flow rate from the mold storage chamber to bring the mold storage chamber close to the molten metal and detect a pressure change generated when the gate comes into contact with the molten metal surface, and the molten metal level in the vacuum suction casting. Detection method. 2. A mold having a runner and a cavity communicating with the runner is protruded from a mold storage chamber having a molten metal suction opening and a decompression opening, and a spout is protruded from the molten metal suction opening of the mold storage chamber. In the molten metal level detecting device in the vacuum suction casting in which the pressure is reduced from the pressure reducing opening and the molten metal is filled into the cavity from the gate, the pipe connecting the pressure reducing opening of the mold storage chamber and the vacuum exhaust device is provided. It is characterized by having a control device for providing a flow rate adjusting means and a flow rate detecting means, outputting a difference between the set flow rate value and the detected flow rate value to the flow rate adjusting means, inputting a pressure value in the mold housing chamber and identifying a pressure change. Level detector in vacuum suction casting.