JPS63273561A - Method and apparatus for controlling pressure - Google Patents

Abstract

PURPOSE:To eliminate resistance to rise of molten metal by adjusting air under high pressure to the prescribed reference pressure, outputting by adding negative bias pressure to the reference pressure and outputting after adjusting this pressure by presetting pressure control pattern. CONSTITUTION:In this apparatus, a furnace 5 is put on a carriage 4 and a crucible 6 is arranged in inner part 5a of the furnace 5 and molten metal 7 is charged in the crucible 6. A stokes 10 is inserted between the crucible 6 and a cavity 9 in the die and the molten metal 7 is filled up into the cavity 9 through the stokes 10. The die 8 is tightly shut by a chamber 11 and the furnace 5 and the chamber 11 are separated by a lower die base 12. Then, the air supplied from an air supplying source under high pressure is adjusted to the prescribed reference pressure and outputted, and the negative bias pressure is added to this reference pressure and outputted. The air pressure adding the negative bias pressure to the above reference pressure is adjusted based on the presetting pressure control pattern.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is employed, for example, when controlling the chamber pressure of a casting device when molten metal is raised into a cavity in a mold of the casting device. The present invention relates to a pressure control device and a pressure control method.

(Prior Art) Conventionally, as an example of controlling a pressure-controlled device using air pressure, there has been a means for low-pressure controlling a casting apparatus 100 as shown in FIG. 12, for example.

According to this casting means using low pressure control, the cavity 102 in the mold 101 is under atmospheric pressure, and the -beak 3 furnace break 103
The inside of the is pressurized from the boat 104 to atmospheric pressure plus P.
By setting the pressure to 1, the molten metal in the crucible 105 rises to the cavity 102 via the stalk 106,
Cavity 102 is filled with molten metal. At this time, the atmospheric pressure inside the cavity 102 was discharged from a vent boat (not shown) inside the mold 101, but the atmospheric pressure inside the cavity 102 became a significant back pressure, which created resistance when the molten metal rose. Therefore, a pressure reduction method is sometimes used as a means to eliminate this resistance to rising of the molten metal. This pressure reduction method was a means of setting the inside of the furnace body 103 to atmospheric pressure, while reducing the pressure of the cavity 102 in the mold 101, and causing the molten metal to rise due to the pressure difference.

(Problems to be solved by the invention) However, in the above conventional pressure-controlled casting apparatus,
In the case of low pressure control, as described above, there is a problem in that resistance to rising of the molten metal occurs due to back pressure due to the atmospheric pressure within the cavity 102. On the other hand, casting means using a reduced pressure method eliminates the molten metal rising resistance, but because the pressure inside the cavity 102 is low, there are problems in that it takes too much time to promote solidification of the molten metal and there is a limit to improving casting quality. there were.

Therefore, the present invention provides a pressure control device that simultaneously achieves the purpose of promoting solidification of the molten metal, which is a feature of the casting means using low pressure control, and the purpose of eliminating the rising resistance of the molten metal, which is a feature of the casting means using a reduced pressure method. This is a technical problem to be solved.

(Means for solving the problem) The technical means for solving the above problem is to install a pressure control device,
A reference pressure regulating means that regulates air supplied from a high-pressure air supply source to a predetermined reference pressure and outputs the same; A bias pressure regulating means for adding and outputting a predetermined bias pressure is installed in an atmospheric pressure-blocking sealed container that receives the air pressure outputted from the bias pressure regulating means, and the bias pressure regulating means adds and outputs a predetermined bias pressure. output pressure regulating means for regulating the air pressure input into the pressure-blocking sealed container to the reference pressure and outputting the regulated air pressure based on a predetermined pressure control pattern; The present invention is configured to include a control means for outputting the pressure regulation signal to the output pressure regulation means as well as a setting value.

(Function) The pressure control function of the pressure control device having the above configuration includes a first step of adjusting the pressure of air supplied from a high-pressure air supply source to a predetermined reference pressure and outputting it, and a negative bias pressure to the reference pressure. a second step of adding and outputting the negative bias pressure, and a third step of regulating the air pressure obtained by adding the negative bias pressure to the reference pressure based on a preset pressure control pattern and outputting it to the outside. to control the pressure of any pressure controlled device.

(Example) Next, a description will be given of an example in which a casting apparatus 1 as shown in FIG. 1 is adopted as a pressure-controlled device, and the pressure of the casting apparatus 1 is controlled.

As shown in FIG. 1, the casting apparatus 1 has an outer frame formed by four frame supports 2, each of which is erected on a base 3. A truck 4 is configured to run on the base 3, and a furnace 5 is placed on the truck 4. Furnace 5
A crucible 6 is provided inside the furnace 5A, and a molten metal 7 is poured into the crucible 6. A stalk 10 is inserted between the crucible 6 and a cavity 9 in the mold 8, and the molten metal 7 is filled into the cavity 9 through the stalk 10.

The mold 8 is sealed by a chamber 11, and the furnace 5 and the chamber 11 are separated by a lower die base 12. The mold 8 is configured to be separable into an upper mold 8A and a lower mold 8B.

The casting apparatus 1 as described above is heated to a furnace 5 by a counter pressure method (hereinafter abbreviated as CP method) as shown below.
An embodiment in which the pressure of the chamber 11 is controlled will be described.

As mentioned above, the furnace 5 of the casting apparatus 1 has a sealed structure, and the mold 8 is also sealed in the chamber 11, so that the furnace 5 and the mold 8 are separated from each other. When controlling the pressure of the casting apparatus 1 using the CP method, first set a pressure of PA kg/cm inside the furnace 5A and the chamber 11 at C in Fig. 2.
As shown in the P method pressurization characteristic curve diagram, pressure is applied during T1 time to make the inside of the furnace 5A and the inside of the chamber 11 the same pressure. Thereafter, for a time TK corresponding to between points AB, the pressure circuit inside the chamber 11 is cut off from the pressure circuit inside the furnace 5A, while maintaining the pressure inside the furnace 5A and the chamber 11 at P A kg/cm''. The internal pressure PAkg/an'' is made independent.

Next, the pressure inside the chamber 11 is gradually reduced from point B in FIG. 2, and pressure reduction control is performed based on the pressure reduction pattern between points B and C so that a stable pressure difference of PA-P3kg/an1 is generated at point C. and PA-P3 as P B kg
According to the general theory based on the CP method, which maintains a pressure of 0/cm", the rising resistance when the molten metal 7 rises is F.
This is solved by the pressure difference A-P3, and on the other hand, the pressure applied to the molten metal becomes a high pressure of PBkg/38, which makes it possible to promote solidification under high pressure.

Next, a pressure control method based on the general theory of the CP method described above will be explained in some detail.

Initially, as shown in Figure 2, the pressure inside the furnace 5A and the chamber 1
It is necessary to increase the pressure in the furnace 5 to PA kg/am'' during the time TI. In this pressurization control process, in order to shorten the cycle time, it is necessary to shorten the time T1. Since both the internal volume of the furnace and the internal volume of the chamber 11 are large, when the pressure inside the furnace 5A and the pressure inside the chamber 11 are quickly increased to P A kg/cm'', a high-pressure service tank as shown in Fig. 3 is used. By supplying air at high speed from 21 through the vibrator 22 and the vibrator 23 until just before the pressure in the furnace 5A and chamber 11 reaches PA kg/cm'', the time T1
A method is adopted to shorten the period.

As shown in FIG. 3, from the service tank 21 the vibe 2
2 and the vibrator 23, there is generally a difference between the internal volume of the furnace and the internal volume of the chamber, so for example, if the internal volume of the chicken bar 11 is smaller than the internal volume of the furnace 5A. , chamber 11
Since the internal air pressure is higher than the 5A inside the furnace, P A kg /
The time it takes to reach "an" becomes faster, and air enters the crucible 6. Therefore, a phenomenon in which the molten metal 7 is stirred by air pressure is caused.

On the other hand, if the internal volume of the furnace is smaller than the internal volume of the chamber,
Since the pressure inside the furnace increases quickly, a problem arises in that the molten metal 7 is filled into the cavity 9. Therefore, as shown in FIG. 3, a bypass circuit 24 and a bypass circuit 25 are provided, and an isopressure valve 26 is also provided.
It is necessary to converge the differential pressure in A and the chamber 11 to zero, and to measure the differential pressure with the differential pressure gauge 27.

The air pressure supplied from the service tank 21 to the inside of the chamber 11 and the inside of the furnace 5A is P A kg/cm.
The air pressure inside the chamber 11 and inside the furnace 5A is then reduced to P A kg by another means.
/cm''. Therefore, as shown in FIG. 4, a release valve 31 is provided in the air supply path of the service tank 21, and the standard pressure is further controlled by a pressure control signal output from the computer CPU. A pressure servo valve 32 and a reference pressure booster 33 for receiving the signal pressure of the servo valve 32 and outputting air at a reference pressure are provided.

The pressurization control process is performed using the pressurization control device as follows. That is, the reference pressure PA kg/cm'' output from the reference pressure booster 33 is supplied to the furnace interior 5A and the chamber 11, and the reference pressure PA kg/cm'' is monitored via the bypass circuit 24 and the bypass circuit 25. The monitor pressure is converted into an electrical signal and the computer CPU
will be given feedback. As a result, when detecting that an error has occurred in the reference pressure, the computer CPU outputs a correction signal to the reference pressure servo valve 32, thereby supplying the correction signal pressure from the servo valve 3 to the reference pressure booster 33, The error is corrected. Furthermore, the reference pressure P A k
g/am” is arbitrarily set by the computer CPU.

Next, the pressure holding control process between points A and B on the pressure characteristic curve diagram of the CP method shown in FIG. 2 will be explained.

As mentioned above, the actual pressure in the furnace 5A and the chamber 11 relative to the reference pressure setting is stabilized by feedback control, but it is not stable with absolutely zero error, and the moment it enters a stable region, Or it may fluctuate even after entering a stable region. Therefore, as shown in Fig. 5, the reference pressure PA
kg/cm! For example, ±50m1 for 5 seconds from the time the actual pressure enters within ±501111Ag! If it is within the range of 1Ag, it is determined that the pressure inside the furnace 5A and the chamber 11 has reached the standard pressure and is stable, and the computer CPU moves to the pressure reduction control step.

The depressurization process is performed at the reference pressure PAkg/c at point B in Figure 2.
This is a step in which the pressure inside the chamber 11 is controlled to be reduced from PBkg/cm'' to PBkg/cm''.

FIG. 6 is an overall system diagram of this embodiment for consistently carrying out the pressure control process, the pressure maintenance control process, and the pressure reduction control process.

As is clear from FIG. 6, in addition to the respective devices related to the pressurization control process and the pressure maintenance control process, a chamber pressure servo valve 42 provided in a sealed container 41 isolated from atmospheric pressure; A chamber booster 43 adjusts the pressure inside the chamber 11 in response to a signal from the servo valve 42, and a reference air pressure of PAkg/an'' output from the reference pressure booster 33 is input, and a negative pressure is applied to the reference air pressure. A bias relay 4 that supplies bias additional air pressure obtained by adding bias air pressure into the sealed container 41.
4 are provided. In addition, the reference pressure booster 33
From the standard pressure PA for the inside of the furnace 5A and the inside of the chamber 11
A pressurizing valve 45 is provided on the output side of the reference pressure booster 33 to be activated when outputting a pressure of 71" kg/c.

The casting apparatus 1 has the configuration shown in FIG. 1, and includes bypass circuits 24, 25, and pressure valves 26. The differential pressure gauge 27 has the same structure as shown in FIG. 3 above.

However, as shown in Fig. 6, the furnace pressure feedback circuit R
1. A chamber pressure feedback circuit R3 is provided,
Each pressure is input into the computer control unit 47 after being converted into an electrical signal. The computer control unit 47 includes the differential pressure gauge 27.
Reference pressure servo valve 32. Chamber pressure servo valve 42.
A bias relay 44 is incorporated, and it is configured so that it can be operated simply by connecting to an AC 100V power source and connecting piping to external pneumatic equipment. Also, a CRT color display 48 for displaying various information is connected to the computer CPU of the computer control unit 47 via a communication line R8232C! I'm pissed. A numeric keypad 47A of the computer control unit 47 is provided for various setting operations such as setting the reference pressure and setting a pressure control teaching pattern to be described later.

Further, the display 47B is provided to digitally display the set reference pressure, the actual furnace pressure, the set differential pressure, the actual differential pressure, and the like.

Next, a CP whose control object is the casting apparatus 1 having the above configuration is
The operation of the specific pressure control device will be explained.

After a start button attached to an operation panel (not shown) is pressed to operate the casting apparatus 1 and close the upper mold 8A and lower mold 8B, in the first step, a reference pressure output control signal is sent from the computer CPU. Servo valve 32 for reference pressure input
outputs a signal pressure corresponding to a preset reference pressure PA kg/cm" to the reference pressure booster 33, and causes the reference pressure booster 33 to output a reference air pressure of the reference EEPA kg/cm".

In the second step, the exhaust valve 51 connected to the bypass circuit 25 is closed, the same pressure valve 26 is opened, the discharge valve 31 is opened, and the pressurizing valve 45 is opened, so that a service tank is installed inside the furnace 5A and inside the chicken bar 11. 21 and reference pressure booster 3
Air is supplied from 3.

In the third step, when the computer control unit 47 measures that the pressure inside the furnace 5A and the chamber 11 has risen to near the reference pressure PAkg/Cm, the discharge valve 31 is closed and the air is discharged from the service tank 21. Stop supply.

In the fourth step, the pressure inside the furnace 5A and the chicken bar 11 reaches the standard pressure PAkg/cm'' and the standard pressure P
Confirm that Akg/cm' is maintained for a predetermined time.

In the next fifth step, the same pressure valve 26 is closed and the sixth
In the step, the chamber pressure servo valve 4 is activated based on the signal from the computer control unit 47.
2 is controlled, and the servo valve 42 outputs a differential pressure signal to the chamber booster 43. That is, in the same step, the reference pressure booster 33 to the pressurizing valve 45
A negative bias pressure, for example, -1 kg/cm'' is added to the reference pressure PAkg/cm'' supplied to the bias relay 44 via the bias relay 44 (F
A-1) Set the pressure in kg/cm" to f 'r n i<-
The output of the chamber pressure servo valve 42 is adjusted to (
PA-1+1)-PAkg/Cm". Therefore, the pressure P A k with respect to the chamber booster 43
A signal pressure corresponding to "1 kg/cm" is output. Furthermore, as long as a signal corresponding to a pressure of 1 kg/cm" is output from the computer control unit 47 to the servo valve 4 for chamber pressure, the signal pressure corresponding to the pressure 1 kg/cm" is output from the reference pressure booster 33. Even if the output pressure changes, a pressure equivalent to the output pressure is output from the chamber booster 43. In the seventh step, a depressurization step is carried out. That is,
Based on a control signal based on a preset pressure reduction control pattern of the computer control unit 47, the output pressure of the chamber pressure servo valve 42 is reduced from 1 kg/cm'', and the molten metal 7 is raised into the cavity 9. When starting, the pressure inside the furnace 5A is the standard pressure PAkg/
(Since it holds the standard pressure PAkg/Cl11"
The differential pressure from the differential pressure gauge 27 is read, and the signal from the differential pressure gauge is input to the computer control unit 47.

In the eighth step, after reducing the pressure inside the chamber 11 to a predetermined pressure and maintaining it for a predetermined time, the reference pressure servo valve 3
2. Chamber pressure servo valve 4i is set to 0FFL, pressure valve 4
5 is closed, the same pressure valve 26 is opened, and the exhaust valve 51 is further opened to exhaust the air. Thereafter, the service tank 21 is charged with air, and the upper mold 8A is further raised to open the mold 8 and take out the cast product.

Next, computer control of the pressure reduction process in the seventh step will be explained.

The depressurization process includes 5A (7) EE power in the furnace and chicken bar 11
After setting the pressure inside the furnace to the standard pressure PA) cg/cm, the pressure inside the chamber 11 is gradually reduced to create casting pressure by differential pressure while maintaining the pressure inside the furnace 5A at PA kg/cm. , is a process for raising the molten metal 7 into the cavity 9.

How the computer CPU outputs the control signal to the chamber pressure servo valve 42 in the above pressure reduction step will be explained below.For example, the teaching pattern as shown in FIG. A pattern is set to linearly reach the differential pressure from " to PXkg/Cm" in TX seconds, and when this setting pattern is input to the computer CPU, the computer CPU
As shown in Fig. 8, Tx seconds is divided into every 611 seconds, the angle at that time is calculated, and it is converted into a signal for producing a pressure called ΔP. This signal is outputted to the chamber pressure servo valve 42 every Δt8 seconds to output the set teaching pattern 0-1. The chamber pressure servo valve 42 is proportionally controlled by voltage or current (0-10V), (4mA-20mA) signals.

However, even if the above-mentioned signal is properly outputted from the unviewer CPU to the chamber pressure servo valve 42 after setting the above-mentioned teaching pattern, it is not known whether the signal is reliably converted into pressure and is operating. The so-called feedback method is used to check whether the pressure matches the taught pattern ΔP''1 every Δt8 seconds.If the actual pressure should be 8P1 after Δt1 seconds, A software program is built into the computer CPU that corrects the insufficient pressure if ΔPA is insufficient.

On the other hand, although a pressure correction function using a feedback method is incorporated as described above, the actual pressure constantly changes with time. If the actual pressure has stopped even though time is progressing, it is only necessary to correct the error by the amount after confirmation, but as mentioned above, the actual pressure changes with time, so correction after confirmation will reduce the control delay. arise. Therefore,
As shown in FIG. 10, if the taught pattern is short by ΔPA at Δt0 seconds, the signal from the computer CPU is input to the chamber pressure servo valve 4.2 after the next Δt or 615 seconds. is ΔP++ΔP
A so-called feedforward method is also used in which it is determined whether or not the input signal matches the taught pattern while replacing the input signal with an input signal that has been corrected by x.

In order to improve accuracy, the memory capacity of the computer CPU is utilized to store the difference between the actual pressure and the corrected pressure for the taught pattern of the previous shot, and then perform learning control for the next shot.

As shown in Figure 10, even if the pressure is controlled using the feedforward method, there will be a difference in the feedforward correction value ΔP for ΔPA, as shown in Figure 11, and even if a correction signal corresponding to +ΔPx is output, there will be a difference in ΔPA. Put it away. Even if the pressure is controlled by feedforward in this way, it is determined that there is still a pressure error in the equally divided time Δt1 to Δt in the teaching pattern, and this amount is memorized and the feedback correction amount ΔPA is used from the next shot. A correction signal corresponding to the feedforward correction amount ΔP1+ΔPx is output, and if it is still insufficient, ΔP1+ΔPx+(ΔP1+ΔPx/
2), on the other hand, if it is excessive, ΔP, +ΔPX-(ΔP, +Δ
Px/2) is used to correct the actual pressure relative to the taught pattern by outputting a corresponding correction signal, thereby bringing the actual pressure closer to the taught pattern as the shot progresses.

(Effects of the Invention) As described above, according to the present invention, for example, when making a casting by controlling the pressure of the casting device to raise the molten metal from the crucible into the cavity of the mold and solidifying it, first, the pressure in the furnace is After simultaneously increasing the pressure and the pressure inside the chamber to the standard pressure, the standard pressure is maintained for a predetermined period of time, and then the pressure is reduced based on a preset pressure control pattern, and when the molten metal is solidified, high pressure is applied to the molten metal. Since the pressure is controlled by applying it, it has the effect of reducing the rising resistance of the molten metal and making it possible to accelerate the solidification of the molten metal.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram partially showing a casting apparatus in which pressure is controlled by a pressure control device according to an embodiment of the present invention, and FIG.
The figure is a CP method pressurization characteristic curve diagram, Figure 3 is a piping system diagram of the pressurizing mechanism, Figure 4 is a standard pressure air supply piping system diagram, Figure 5 is an explanatory diagram of standard pressure stability conditions, and Figure 611A is a casting equipment FIG. 7 is an ideal pressure teaching pattern diagram, FIG. 8 is an illustration of computer pressure control signal output, FIG. 9 is an illustration of feedback control of pressure control, Fig. 10 is an explanatory diagram of feedforward control of pressure control, Fig. 11 is an explanatory diagram of learning control of pressure control, and Fig. 12 is an explanatory diagram of feedforward control of pressure control.
The figure is a structural diagram showing a conventional casting apparatus, including a partial cross section. 32... Servo valve for reference pressure 33... Booster for reference pressure 42... Servo valve for chamber pressure 43... Booster for chamber 44... Bias relay 47... Computer control unit Patent applicant Isuzu Seisakusho Co., Ltd. Agent Patent Attorney Yoshihisa Shimizu Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 9 Figure 10 Figure 11 Figure 12

Claims (2)

[Claims] (1) A reference pressure regulating means for regulating air supplied from a high-pressure air supply source to a predetermined reference pressure, and inputting the air regulated to a reference pressure by the reference pressure regulating means to the same reference pressure. A bias pressure regulating means for adding and outputting a negative bias pressure to the bias pressure regulating means is installed in an atmospheric pressure-blocking sealed container into which the air pressure outputted from the bias pressure regulating means is input, and the air pressure is adjusted according to a pressure regulating signal from the outside. output pressure regulating means for regulating the air pressure input into the atmospheric pressure-blocking sealed container to the reference pressure and outputting the regulated air pressure based on a predetermined pressure control pattern; and the reference pressure and the pressure control pattern. 1. A pressure control device comprising: control means for setting the output pressure and outputting the pressure regulation signal to the output pressure regulation means. (2) a first step of adjusting the pressure of air supplied from a high-pressure air supply source to a predetermined reference pressure and outputting the same; a second step of adding a negative bias pressure to the reference pressure and outputting the result; A pressure control method that performs pressure control in the order of a third step in which the air pressure obtained by adding the negative bias pressure to the reference pressure is regulated based on a preset pressure control pattern and outputted to the outside.