JP2006110561A - Method of die casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for determining an optimum supply quantity of oxygen taking a characteristic (individuality) of a die into consideration by correcting the supply quantity of oxygen in a next shot by a new method. <P>SOLUTION: A method of die casting comprises a first step for supplying oxygen into a die cavity 6, a second step for carrying out the casting into the die cavity 6 and for sucking the gas existing in the die cavity 6 into a vacuum tank 12 by making the vacuum tank 12, which serves as an external vessel of a die casting machine 1, communicate with the die cavity 6, a third step for measuring the density of the oxygen existing in the vacuum tank 12, and a fourth step for calculating the supply quantity of oxygen in the first step of the next shot based on the density of the oxygen measured in the third step. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention replaces a gas such as air in a mold cavity with oxygen gas, and die casting suitable for performing an oxygen atmosphere die casting method (PF method) in which molten metal is supplied into the mold cavity in this state. It is about the law.

Conventionally, an oxygen atmosphere die casting method (PF method) is known in which a gas such as air in a cavity is replaced with oxygen gas, and molten metal is supplied into the cavity in that state (see, for example, Patent Documents 1 and 2). .
Then, the oxygen concentration in the mold cavity is measured by an oxygen concentration sensor, and the required oxygen supply amount at the next shot is determined based on the measurement result. Corrections are made so as to approach the planned values actually required.
The timing for calculating the oxygen concentration is assumed to be performed before the start of the casting operation by the injection tip in the injection sleeve or during the low-speed movement period of the injection tip after the start of the casting operation.
JP-A-10-113757 Japanese Patent Laid-Open No. 10-029050

However, at the timing of measuring the oxygen concentration as described above, it is not possible to determine the optimum required oxygen supply amount according to the characteristics (individual differences between molds) such as the sealing performance, cavity volume, and cavity shape inherent to the mold. It has become.
For example, when the sealing performance of the mold mating surface is poor, oxygen leaks after supplying oxygen, and in this case, the oxygen concentration in the cavity becomes low in the conventional method. The sealing performance of the mold mating surface changes over time due to thermal deformation of the mold due to continuous casting and biting of the generated burrs. This makes it impossible to obtain the oxygen concentration required in the interior. That is, oxygen is insufficient.
In contrast to the above, it is conceivable to supply more oxygen than the originally required supply amount. In this case, unnecessary oxygen is supplied. That is, excessive oxygen supply is performed.
In the technique disclosed in Patent Document 1, suction decompression in the cavity is performed before the casting operation. The degree of decompression achieved by the suction decompression is also affected by the sealing performance and the shape of the cavity. As a result, the oxygen substitution rate also fluctuates.
As described above, the conventional technology cannot determine the optimum oxygen supply amount in consideration of the mold characteristics (individual differences), and has corrected the oxygen supply amount for the next shot. Even so, the actual oxygen concentration was not the required planned value.

In addition, since the cavity shape is complicated, an error occurs between the oxygen concentration sensor installed in the vent passage and the oxygen concentration sensor installed in the suction passage in the prior art with the actual oxygen concentration in the cavity. In addition, since the concentration is measured under pressure fluctuation in the suction path, the reliability of the measurement result is low.
For this reason, it is also considered to install an oxygen concentration sensor in the mold. However, since there is no oxygen concentration sensor that has heat resistance and a high detection speed at present, this scheme cannot be adopted.
As described above, the conventional technology cannot accurately detect (monitor) the actual oxygen concentration in the cavity. Under such circumstances, the oxygen supply amount for the next shot is corrected. However, the actual oxygen concentration was not the required planned value.

  The present invention has been made in view of the above points. A technique for correcting the oxygen supply amount of the next shot by a novel method and determining an optimum oxygen supply amount in consideration of the characteristics (individual difference) of the mold. It is what we propose.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

  That is, as described in claim 1, the first step of supplying oxygen into the mold cavity, casting into the mold cavity, and communication between the container outside the die casting machine and the mold cavity, Based on the second step of sucking the gas in the mold cavity into the external container, the third step of measuring the oxygen concentration in the external container, and the oxygen concentration measured in the third step, The die casting method has a fourth step of calculating the amount of oxygen supplied in the first step of the shot.

  Further, as described in claim 2, in the third step, the oxygen concentration is measured in a predetermined period in which the value of the oxygen concentration is stabilized.

  Further, as described in claim 3, in the third step, the nitrogen concentration is measured, and if the nitrogen concentration is higher than a specified value, the occurrence of a malfunction of the apparatus is recognized.

  As effects of the present invention, the following effects can be obtained.

That is, according to the first aspect of the present invention, the supply amount is corrected based on the actually measured oxygen concentration in each shot, that is, the optimum oxygen supply considering the characteristics (individual difference) of the mold. A quantity determination can be made. Thereby, problems such as insufficient oxygen in the mold cavity and excessive oxygen supply can be prevented.
In addition, since the oxygen concentration in the external container is detected, the oxygen concentration in the mold cavity can be accurately detected, and the oxygen supply amount is controlled based on highly reliable data. Can do.

  In the invention according to claim 2, in the calculation of the oxygen supply amount in the fourth step, the oxygen concentration during the unstable period is not adopted, and only the oxygen concentration during the predetermined period when the concentration is stable is used. Therefore, it is possible to calculate the oxygen supply amount based on an accurate oxygen concentration.

  Further, in the invention according to the third aspect, it is possible to find out early occurrence of problems such as breakage of the mold, deterioration of the sealing performance of the mating surface, and pressure leakage of the vacuum decompression path 11.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment of an apparatus configuration for carrying out a die casting method according to the present invention.
The die casting machine 1 has a fixed mold 2 and a movable mold 3, and the movable mold 3 is moved in the left-right direction in FIG. 1 by a mold clamping device (not shown). In addition, in FIG. 1, the state which completed the mold clamping is shown.
An injection sleeve 4 is attached to the fixed mold 2. The injection sleeve 4 is slidably provided with a tip 5 for injecting a molten metal that is advanced and retracted by an injection cylinder (not shown). By moving leftward, the mold cavity 6 is pushed and filled through the runner 2a.

The fixed mold 2 is provided with a pressure reducing valve 7 that communicates with the inner space of the mold cavity 6.
The pressure reducing valve 7 is connected to an oxygen supply source 9 constituted by an oxygen cylinder or the like via an oxygen supply path 8.
The oxygen supply path 8 is provided with a flow rate control valve 8a. The flow rate control valve 8a is connected to a controller 10, and the controller 10 controls the opening degree of the flow rate control valve 8a.
With the above configuration, the controller 10 controls the opening degree of the flow rate control valve 8 a so that oxygen in the oxygen supply source 9 is supplied into the mold cavity 6 through the oxygen supply path 8 and the pressure reducing valve 7. ing.

The decompression valve 7 is connected to a vacuum tank 12 which is a container outside the die casting machine 1 through a vacuum decompression path 11.
The vacuum decompression path 11 is provided with an open / close control valve 11a. The opening / closing control valve 11a is connected to the controller 10, and the controller 10 controls the opening / closing of the opening / closing control valve 11a.
Further, the vacuum tank 12 is configured so that a vacuum state is formed by sucking the gas in the vacuum tank 12 by a vacuum pump 13. The vacuum tank 12 is provided with a nitrogen concentration sensor 14 for detecting the nitrogen concentration in the vacuum pump 13 and an oxygen concentration sensor 15 for detecting the oxygen concentration in the vacuum tank 12. Each of the sensors 14 and 15 is connected to the controller 10 so that the controller 10 can measure the nitrogen concentration and the oxygen concentration in the vacuum tank 12.
The vacuum pump 13 is connected to the controller 10, and the controller 10 controls the start / stop of the driving of the vacuum pump 13.
With the above configuration, the controller 10 controls the vacuum pump 13 and the open / close control valve 11a to suck the gas in the mold cavity 6 into the vacuum tank 12, and to adjust the nitrogen concentration and oxygen concentration of the sucked gas. It is possible to measure.

Next, a die casting method using the above apparatus configuration will be described.
FIG. 2 shows a process (one-shot process) performed from the start to the end of casting. The left column shows the operating positions of the movable mold 3 and the chip 5, the oxygen supply state, and the like, and the right column shows the time variation of the oxygen concentration 21 and the nitrogen concentration 22 in the vacuum tank 12. Yes.
FIG. 3 is a diagram showing details of the flow from the start to the end of casting.
Hereinafter, each step will be described step by step.

As shown in the first stage D1 of FIG. 2, the movable mold 3 is separated from the fixed mold 2 and is in a standby state, and the pressure reducing valve 7 is opened to the atmosphere. As a result, the oxygen concentration 21 and the nitrogen concentration 22 in the vacuum tank 12 are the same as the concentrations in the atmosphere.
In this case, the controller 10 closes the flow control valve 8a (step 31 shown in FIG. 3).

Next, as shown in stage D2 of FIG. 2, the movable mold 3 is clamped with respect to the fixed mold 2 (step 32). In this clamped state, the controller 10 opens the opening / closing control valve 11a (step 33) and drives the vacuum pump 13 to start sucking the gas in the mold cavity 6 and the vacuum tank 12. (Step 34).
When the controller 10 confirms the vacuum state, that is, confirms that the oxygen concentration 21 and the nitrogen concentration 22 are 0%, the controller 10 closes the open / close control valve 11a (step 35) and drives the vacuum pump 13. Stop and complete the suction of gas (step 36). As a result, the mold cavity 6 and the vacuum tank 12 are evacuated.
Next, the controller 10 opens the flow rate control valve 8a and starts supplying oxygen into the mold cavity 6 (step 37). Here, the opening degree C of the flow control valve 8a and the time T during which the flow control valve 8a is opened, that is, the supply amount F, are calculated by the controller 10 as described later.
After the elapse of time T, the controller 10 closes the flow control valve 8a and completes the supply of oxygen (step 38).

Next, as shown in stage D3 of FIG. 2, casting by the movement of the chip 5 is started (step 39), and the opening / closing control valve 11a is opened by the controller 10 (step 40), and the gas in the mold cavity 6 is opened. Is sucked into the vacuum tank 12 (step 41). Thereby, pressure reduction in the mold cavity 6 is performed.
Here, as shown in the graph of the stage D3 in FIG. 2, the oxygen concentration 21 in the vacuum tank 12 increases with the passage of time. The increase in the oxygen concentration 21 is based on oxygen supplied from the oxygen supply source 9. In this case, the nitrogen concentration 22 also increases. The increase in the nitrogen concentration 22 is based on the air that has entered the mold cavity 6 from the outside of the die casting machine 1. For example, when the deterioration of the sealing performance is in progress, the nitrogen concentration 22 is increased. Increase amount becomes large.

Next, as shown in stage D4 of FIG. 2, when the casting by the movement of the chip 5 is completed (step 42), the controller 10 closes the open / close control valve 11a (step 43), and the gas is trapped in the vacuum tank 12. It becomes a state.
At this stage, the controller 10 determines the supply amount F in the next shot based on the measured value of the oxygen concentration 21 in the vacuum tank 12 (step 44).
For example, when the measured value of the oxygen concentration 21 is lower than the specified value M (see the graph of the step D4 in FIG. 2), correction for increasing the supply amount F in the next shot is performed, and the measured value of the oxygen concentration 21 is specified. When the value is higher than the value M, a correction for decreasing the supply amount F in the next shot is performed. In this way, the actual oxygen concentration 21 is fed back to the supply amount F in the next shot.

The specified value M is a theoretical planned value determined at the device design stage. By setting the specified value M, an optimal oxygen atmosphere is realized.
Further, the correction amount of the supply amount F is performed in accordance with a calculation formula stored in advance in the controller 10. For example, the difference between the specified value M and the actual oxygen concentration 21 is obtained, the amount of oxygen to be increased or decreased corresponding to this difference is obtained, and the value obtained by adding or subtracting this amount of oxygen to the supply amount of the current shot is calculated for the next shot. The supply amount F of
Further, the correction is performed by changing the opening degree C of the flow rate control valve 8a or the open time T.

  Furthermore, the mold cavity 6 is rich only in oxygen and nitrogen, and the oxygen concentration 21 can be calculated from the nitrogen concentration 22. For this reason, in determining the supply amount F in the next shot, in addition to using the oxygen concentration 21 as a reference, the nitrogen concentration 22 is also used as a reference, so that the errors of the nitrogen concentration sensor 14 and the oxygen concentration sensor 15 are mutually different. Corrections can be made and the reliability of the measurement data can be increased.

  After the above casting is completed, the movable mold 3 is removed from the fixed mold 2 and the cast product is taken out. At the same time, the controller 10 opens the open / close control valve 11a so that the gas in the vacuum tank 12 is discharged to the outside. And is set in a standby state for the next shot (step 45).

Die casting is performed as described above.
That is, in the above configuration, as shown in FIG. 4, the first step S <b> 1 for supplying oxygen into the mold cavity 6, casting into the mold cavity 6, and vacuum as a container outside the die casting machine 1. A second step S2 for communicating the tank 12 and the mold cavity 6 to suck the gas in the mold cavity 6 into the vacuum tank 12, and a third step S3 for measuring the oxygen concentration 21 in the vacuum tank 12. Based on the oxygen concentration 21 measured in the third step, the die casting method has a fourth step S4 for calculating the supply amount F of oxygen in the first step of the next shot.

Then, according to the above method, the supply amount F is corrected based on the actually measured oxygen concentration 21 in each shot, that is, optimal oxygen supply in consideration of mold characteristics (individual differences). A quantity determination can be made. Thereby, problems such as insufficient oxygen in the mold cavity 6 and excessive oxygen supply can be prevented.
Further, since the oxygen concentration 21 in the vacuum tank 12 communicating with the mold cavity 6 via the vacuum decompression path 11 is detected, the oxygen concentration 21 in the mold cavity 6 can be detected accurately. Thus, it is possible to control the oxygen supply amount based on highly reliable data.

In the third step, the oxygen concentration 21 is measured. As shown in FIG. 5, the oxygen concentration 21 in the vacuum tank 12 is a period T1 during which the gas in the mold cavity 6 is sucked. Then, it rises, and after a while, shows a substantially constant value and stabilizes. For this reason, it is desirable that the measurement of the oxygen concentration 21 is performed in the period T2 in which the oxygen concentration 21 is stable.
Therefore, in the third step, the oxygen concentration 21 is measured during a predetermined period T2 in which the value of the oxygen concentration 21 is stable.
According to the above, in the calculation of the oxygen supply amount F in the fourth step, the oxygen concentration 21 of the period T1 where the concentration is unstable is not adopted, and only the oxygen concentration 21 of the predetermined period T2 where the concentration is stable is used. Since it is adopted, the supply amount F can be calculated based on the accurate oxygen concentration 21.

For the predetermined period T2, in addition to using the time as a reference so as to be a fixed time after the start of suction and the time T3 has elapsed, a period with little variation in measurement data is extracted. In addition, the measurement data may be used as a reference.
Also in this case, by using the nitrogen concentration 22 as a reference in addition to the oxygen concentration 21 as a reference, the errors of the nitrogen concentration sensor 14 and the oxygen concentration sensor 15 can be mutually corrected. The reliability of measurement data can be improved.

In the third step, the controller 10 measures the nitrogen concentration 22 and, when the nitrogen concentration 22 is higher than the specified value N, authorizes the occurrence of a malfunction of the apparatus.
As shown in FIG. 6, when a malfunction such as a decrease in the sealing performance of the mating surface of the movable mold 3 and the fixed mold 2 or a pressure leak in the vacuum decompression path 11 occurs, the nitrogen concentration 22 increases. This is to detect the occurrence of a malfunction of the apparatus. And when generation | occurrence | production of a malfunction is detected, the generation | occurrence | production of a malfunction will be alert | reported by the alerting means which is not shown in figure.
If the nitrogen concentration 22 is lower than the specified value N, that is, if it is within the management range P1, the controller 10 assumes that there is no occurrence of the malfunction of the apparatus as described above, and notifies the occurrence of the malfunction. Shall not be performed.

According to the above, it is possible to detect at an early stage occurrence of problems such as damage to the mold, deterioration of the sealing performance of the mating surfaces, and pressure leakage in the vacuum decompression path 11.
Further, in this case, by using the oxygen concentration 21 as a reference in addition to the nitrogen concentration 22 as a reference, errors in the nitrogen concentration sensor 14 and the oxygen concentration sensor 15 can be mutually corrected. The reliability of measurement data can be improved. That is, for the oxygen concentration 21, a management width P2 is provided, and if the management width P2 is deviated, a problem occurs.

The figure shown about the apparatus structural example for implementing the die-casting method of this invention. The figure shown about the process performed from casting start to completion | finish. The figure which similarly shows a flowchart. The figure which shows the outline | summary of the process performed from a casting start to completion | finish. The figure shown about the transition of oxygen and nitrogen concentration in a vacuum tank. The figure shown about the relationship between nitrogen concentration and apparatus malfunction generation | occurrence | production.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Die casting machine 2 Fixed type 3 Movable type 5 Chip 6 Mold cavity 8 Oxygen supply path 8a Flow control valve 9 Oxygen supply source 10 Controller 11 Vacuum decompression path 12 Vacuum tank 14 Nitrogen concentration sensor 15 Oxygen concentration sensor 21 Oxygen concentration 22 Nitrogen concentration

Claims (3)

A first step of supplying oxygen into the mold cavity;
While casting into the mold cavity,
A second step of communicating a container outside the die casting machine with the mold cavity, and sucking the gas in the mold cavity into the external container;
A third step of measuring the oxygen concentration in the external container;
A die casting method having a fourth step of calculating an oxygen supply amount in the first step of the next shot based on the oxygen concentration measured in the third step.   2. The die casting method according to claim 1, wherein in the third step, the oxygen concentration is measured in a predetermined period during which the value of the oxygen concentration is stable.   3. The method according to claim 1, wherein in the third step, the nitrogen concentration is measured, and if the nitrogen concentration is higher than a specified value, the occurrence of a malfunction of the apparatus is recognized. Die casting method.

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