JP3503257B2 - Injection speed control method for die casting - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the injection speed in die casting according to the filling condition of the molten metal in the die.

[0002]

2. Description of the Related Art Generally, die casting is intended for casting a product having a thin wall thickness, and rapid cooling is performed in order to reduce the grain size of the cast product and increase the strength. When the injection speed of the molten metal from these is low, leading to casting defects solidification begins with the hot water around defect before the entire cavity tee <br/> in the mold melt over go. Therefore the molten metal has to be filled into a mold by high-speed injection, but just because the molten metal
When once filled at high speed from the injection device to the mold cavity, write winding an air and oil in the injection device in the molten metal
Rarely , this also contributes to casting defects.

As a technique for taking measures against this, there is, for example, a die casting casting means disclosed in the column of "Prior Art" in Japanese Patent Laid-Open No. 4-94856. In this technique, when the molten metal is filled in the mold by the plunger of the injection device, the movement stroke of the plunger when the process of filling the molten metal into the cavity in the mold is reached is detected by the limit switch. Then, based on the detection signal from the limit switch, the working hydraulic pressure for the hydraulic cylinder that is the drive source of the plunger is increased, and the injection speed of the molten metal by the injection device is switched from low speed to high speed to fill the cavity with the molten metal. .

[0004]

However, it cannot be said that the filling amount of the molten metal by the injection device and the moving stroke of the plunger are necessarily in a predetermined correspondence relationship. For example, the amount of molten metal supplied from the ladle or the automatic water heater to the injection device is not strictly constant, and therefore the amount of molten metal filled when the plunger moves to the detection position by the limit switch also varies, and Whether or not the cavity in the mold has been reached is not uniquely determined. Therefore, when the injection speed of the molten metal by the injection device is switched to a high speed, the process of filling the cavity may not yet be reached in the mold, and as a result, the cause of the casting defect remains. .

One problem to be solved by the present invention is
The molten metal injection speed corresponding to the filling amount of the molten metal in the mold is detected based on the detection result by detecting the actual arrival of the molten metal at the mold weir or the shut-off valve set by the casting method. It is to prevent the occurrence of casting defects due to improper injection speed. Another problem to be solved by the present invention is to compare the pressure of the molten metal when the molten metal reaches the weir portion or the shut-off valve with the pressure of the molten metal at the time of favorable casting, and thus the abnormal casting condition is observed. Is also detectable. Another problem to be solved by the present invention is to reliably suppress the molten metal when it is filled in the mold by low-speed injection with a shut-off valve, and accurately detect the pressure change of the molten metal. .

[0006]

The injection speed control method for die casting according to the present invention is as follows. The invention according to claim 1 detects the pressure change of the molten metal when the molten metal reaches the weir portion in the mold set by the casting method.
It is characterized in that the injection speed of the molten metal by the injection device is switched from low speed to high speed based on this detection . In the invention according to claim 2, the shut-off valve is advanced near the weir portion in the mold set by the casting method, and it is detected that the molten metal has actually reached the shut-off valve, and based on that, The shut-off valve is retracted from the mold and the injection speed of the molten metal by the injection device is switched from low speed to high speed. According to a third aspect of the invention, in the injection speed control method according to the second aspect, the pressure change of the molten metal suppressed by the shut-off valve is measured, and the molten metal reaches the shut-off valve based on the measured value. It is characterized by detecting. According to a fourth aspect of the invention, in the injection speed control method according to the second aspect, the temperature change of the shutoff valve is measured, and it is detected that the molten metal has reached the shutoff valve based on the measured value. And According to a fifth aspect of the present invention, in the injection speed control method according to the second aspect, the shut-off valve is provided with a gas vent hole communicating with a gas vent passage open to the atmosphere, and the gas vent hole is blocked by the molten metal. It is characterized in that the change in the gas flow rate in the gas vent passage is measured, and the arrival of the molten metal at the shutoff valve is detected based on the measured value.

[0007]

According to the first aspect of the invention, when the molten metal injected from the injection device into the mold actually reaches the dam portion, the injection speed of the molten metal is switched from low speed to high speed. Therefore, the switching of the injection speed is performed at an accurate timing corresponding to the filling amount of the molten metal in the mold. According to the second aspect of the present invention, the molten metal at the time of low speed injection is reliably suppressed by the shutoff valve, and when the molten metal actually reaches the shutoff valve, the injection speed is switched from the low speed to the high speed. Therefore, the switching of the injection speed is performed at an accurate timing corresponding to the filling amount of the molten metal in the mold. According to the third aspect of the present invention, it is detected that the molten metal actually reaches the shutoff valve by measuring a rapid pressure change (rise) of the molten metal that is suppressed by the shutoff valve. The molten metal injection speed is switched from low speed to high speed. Therefore, the injection speed switching timing becomes clearer, and by comparing the measured value with the molten metal pressure at the time of favorable casting, it is possible to detect abnormalities in the casting condition and take prompt action. In the invention according to claim 4, by measuring the temperature change of the shut-off valve, it is detected that the molten metal actually reaches the shut-off valve, and based on that, the injection speed of the molten metal is changed from low speed to high speed. Can be switched. Further, the measured value in this case can also detect the temperature abnormality of the molten metal that has reached the shutoff valve. In the invention according to claim 5, it is detected that the molten metal actually reaches the shutoff valve by measuring the change in the gas flow rate in the gas passage, and based on that, the injection speed of the molten metal changes from a low speed. Can be switched at high speed.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. Embodiment 1 (corresponding to the invention described in claim 1 ) FIG. 1 is a configuration diagram showing a partial cross section of a die casting apparatus.
As shown in this drawing, a fixed die plate 14 and a movable die plate 16 are arranged on the substrate 13 of the casting apparatus so as to face each other. The fixed die plate 14 is immovable with respect to the substrate 13, while the movable die plate 16 is guided by the tie bar 20.
It can move in the direction of approaching or leaving 4.

A fixed mold 10 and a movable mold 12 are provided between the die plates 14 and 16.
The fixed die 10 is fixed to a fixed die plate 14, and the movable die 12 is fixed to the movable die plate 16 via a movable die base 18. Further, the movable die plate 16 is moved while being guided by the tie bar 20 through the movements of the toggle link 23 and the cross head 24 by the operation of the mold clamping cylinder 26.
It is well known that the mold clamping for joining the movable mold 12 to the fixed mold 10 or the mold opening for separating the movable mold 12 from the fixed mold 10 is performed by this.

An injection device 40 is provided on the fixed mold 10 side, and the molten metal in a molten metal heat-retaining furnace (not shown) provided near the die-casting device is placed in the ladle 4.
8 to be supplied by. By pushing and moving the plunger 44 of the injection device 40 by the injection cylinder 50, the molten metal is filled in both the molds 10 and 12.

FIG. 2 is a block diagram showing a part of FIG. 1 in an enlarged cross section. As is clear from this drawing, a cavity 30 for molding a cast product is formed inside each of the above-mentioned molds 10 and 12, and a runner 32 having a shape and a position set based on a casting bill is provided. The dam portion 34 is configured. The injection device 40 includes the fixed die plate 14
And a sleeve 42 which penetrates the fixed mold 10 and communicates with the runner 32, and the plunger 44 which reciprocates in the sleeve 42. Further, the sleeve 42 is formed with a sprue 46 on the outer side of the fixed die plate 14 for receiving the molten metal supplied from the ladle 48.

The injection cylinder 50 is the injection device 4
0 and the piston 52 and the plunger 44 of the injection device 40 are arranged coaxially with the piston rod 5
Three are connected to each other. This injection cylinder 5
Reference numeral 0 is a hydraulic type, and the hydraulic pressure for the piston 52 can be controlled by the hydraulic control valve 58. That is, it is possible to adjust the moving speed (injection speed) of the plunger 44 during the filling of the molten metal by controlling the hydraulic pressure. Further, the hydraulic pressure to the piston 52 of the injection cylinder 50 can be detected by the pressure detector 60 during the filling of the molten metal.

Next, the control of the injection speed during casting will be described. First, after supplying the molten metal into the sleeve 42 of the injection device 40, the plunger 44 is pushed by the operation of the piston 52 of the injection cylinder 50. At this time, the operating pressure of the injection cylinder 50 is kept low by the hydraulic control valve 58 to move the plunger 44 at a low speed, and the molten metal in the sleeve 42 is moved to the inside of the runner 32 to the dam portion 34. It is filled by low-speed injection until reaching.

When the molten metal reaches the dam portion 34, the filling pressure of the molten metal sharply rises. This pressure change (increase)
Acts on the plunger 44 of the injection device 40, and in turn acts as a reaction force to the piston 52 of the injection cylinder 50. As a result, the hydraulic pressure of the injection cylinder 50 rises, which is detected by the pressure detector 60. At this time, an electric signal transmitted from the pressure detector 60 is sent to the control circuit 56 shown in FIG. 2, and in accordance with the electric signal output from the control circuit 56 to the hydraulic control valve 58, the injection cylinder 50 is injected. The piston 52
The operating hydraulic pressure for is switched to high pressure. Therefore, from this time point, the plunger 44 moves at high speed, and the molten metal is filled in the cavity 30 by high-speed injection.

FIG. 3 shows the relationship between the molten metal filling pressure (the operating hydraulic pressure of the injection cylinder 50) P by the injection device 40 and the time T. In this figure, T0 to T1 are times when the sleeve 42 of the injection device 40 is filled with the molten metal, and T1 to T2 are times when the runner 32 is filled with the molten metal. And the filling pressure P of the molten metal
Continues to rise until reaching P1 during the time T0 → T1 and then reaching time T2, but up to this point it is still in the low-speed injection region. Then, when the time T2 is reached, the filling pressure P becomes P2, which is the high-speed injection region.

In this way, the injection speed switching timing corresponding to the filling amount of the molten metal into the molds 10 and 12 is set based on the pressure change of the molten metal when the molten metal actually reaches the dam portion 34. As a result, even if there is some variation in the amount of molten metal supplied to the sleeve 42 of the injection device 40, the change from low-speed injection to high-speed injection can be performed accurately without being affected by it. As a result, the molten metal can be filled into the cavities 30 of the molds 10 and 12 by high-speed injection, and by solidifying the molten metal by rapid cooling, the grain size of the cast product can be reduced and its strength can be increased. At the same time, the cycle time of casting can be shortened.

Since the time point at which the molten metal is started to be filled in the cavity 30 can be accurately grasped, if the subsequent molten metal filling amount (movement amount of the plunger 44) is managed,
Spouting of molten metal from the mating surfaces of the molds 10 and 12 can be avoided, and burrs of cast products can be prevented. Further, in the present embodiment, it is also possible to previously obtain the pressure of the molten metal when favorable casting is performed and compare the value with the pressure value detected by the pressure detector 60.
By this comparison, it is possible to detect the malfunction of the injection device 40 and the abnormality of the pressure increase of the cavity 30.

Embodiment 2 FIG. 4 is a sectional view showing the die casting apparatus of Embodiment 2. As is apparent from this drawing, in this embodiment, the insert 64 made of a material different from that of the fixed mold 10 is fixed to the surface layer corresponding to the dam portion 34 in the fixed mold 10. The fixed die plate 1 is attached to the insert 64.
A thermocouple 66 is assembled by penetrating the fixed mold 10 from the outer side of 4. The thermoelectromotive force generated in the electric circuit of the thermocouple 66 is measured by the measuring device 62, and the temperature change of the dam portion 34 can be detected.

In the second embodiment, the molten metal filled in the runners 32 in both molds 10 and 12 by low-speed injection by the injection device 40 reaches the weir portion 34, and the weir portion 34.
When the temperature rises rapidly, the temperature change is detected by the measuring device 62. Then, an electric signal is sent from the measuring device 62 to the control circuit 56, and based on the control signal output from the control circuit 56 to the hydraulic control valve 58 in accordance with the electric signal, the injection cylinder 5 is ejected as in the case of the first embodiment.
The operating oil pressure for the zero piston 52 is switched to a high pressure. As a result, the molten metal is filled into the cavity 30 by high-speed injection, and the same function as in the first embodiment can be obtained.

Particularly, in the second embodiment, both molds 10, 1 are used.
It is possible to detect the temperature abnormality of the molten metal itself injected into the inside of No. 2, and it is also possible to cope with the die life such as metal fatigue from the relationship between the number of times casting is repeated and the temperature detected by the measuring device 62. In the second embodiment, members which are considered to have the same or equivalent configurations as those in the first embodiment are designated by the same reference numerals in the drawings, and duplicated description will be omitted. Also, for the third to fifth embodiments described below, the same reference numerals are given to the drawings and the duplicated description will be omitted based on the same idea.

Embodiment 3 (corresponding to the invention described in claims 2 and 4 ) FIG. 5 is a sectional view showing the die casting apparatus of Embodiment 3 in section. As shown in this drawing, the mold 1 is used in this embodiment.
A shut-off valve 70 is provided at a position corresponding to the dam portion 34 in 0 and 12 by penetrating the fixed mold 10 from the outside of the fixed die plate 14. On the other hand, a shut-off cylinder 80 is attached to the outer surface of the fixed die plate 14, and a piston 82 in the cylinder 80 is connected to the shut-off valve 70.

The shut-off cylinder 80 is also hydraulic, and the piston 82 is controlled by a hydraulic control valve 84.
The direction of the hydraulic pressure acting on the can be switched and controlled. By the movement of the piston 82 in accordance with the control of the operating hydraulic pressure, the shutoff valve 70 can be advanced toward the inside of the molds 10 and 12, or conversely can be retracted from the inside of the molds 10 and 12. Is. When the shut-off valve 70 is advanced into the molds 10 and 12, the tip of the shut-off valve 70 comes into contact with the dam portion 34 and the communication between the runner 32 and the cavity 30 is blocked.

FIG. 6 is an enlarged plan view of a part of the shutoff valve 70. As is apparent from this drawing, the tip portion of the shutoff valve 70, that is, the molds 10, 12
A plurality of slits 72 are formed in the widthwise direction at the end located inside. Each of these slits 7
The width a of 2 allows air and gas to pass from the runner 32 side to the cavity 30 side even when the shut-off valve 70 is advanced into the molds 10 and 12, and the passage of molten metal can be suppressed. The size is set to about 0.2 mm.

At the tip of the shut-off valve 70, as shown in FIG. 5, there is provided an electrode for energizing due to the deposition of molten metal, or a detector 74 such as a sensor for electrically detecting a temperature change. The electric signal output from the detector 74 is sent to the control circuit 56 shown in FIG. 5, and from this control circuit 56, the hydraulic control valve 58 of the injection cylinder 50 and the hydraulic control valve 84 of the shutoff cylinder 80. A control signal is transmitted to each.

In the third embodiment, the shut-off valve 70 is made to advance into the molds 10 and 12 at the time of die casting, and the plunger 44 of the injection device 40 is injected as in the first and second embodiments. The piston 52 of the working cylinder 50 is moved at a low speed to fill the molten metal into the inside of the runner 32 by low-speed injection. At this time, the gas generated from the air or the molten metal in the sleeve 42 of the injection device 40 passes from the runner 32 side to the cavity 30 side through each slit 72 of the shutoff valve 70, and the molds 10 and 12 are separated. It is released to the atmosphere through a gas vent hole (not shown) provided.

The detector 74 indicates that the molten metal filling the runway 32 by low-speed injection adheres to the shutoff valve 70, or that the molten metal reaches the shutoff valve 70 due to a rapid temperature rise. Detected in. An electric signal based on this detection is sent to the control circuit 56,
As a result, control signals are transmitted from the control circuit 56 to the hydraulic control valve 58 of the injection cylinder 50 and the hydraulic control valve 84 of the shutoff cylinder 80 as described above. As a result, the direction of the operating oil pressure acting on the piston 82 of the shut-off cylinder 80 is switched, and the shut-off valve 70 is retracted from the molds 10 and 12 by the movement of the piston 82 accordingly.
At the same time, the piston 5 of the injection cylinder 50
The operating hydraulic pressure for 2 is switched to a high pressure, whereby the molten metal is filled in the cavity 30 by high-speed injection as in the case of the first and second embodiments.

The molten metal filling the runner 32 by low-speed injection cannot pass through the slits 72 of the shutoff valve 70 and is suppressed by the shutoff valve 70. Therefore, until the molten metal is filled in the runner 32, even a slight amount of the molten metal is not press-fitted into the cavity 30, and it is certain that the cavity 30 is filled with the molten metal by low-speed injection and solidification starts early. Avoided.

Embodiment 4 (corresponding to the invention described in claim 3 ) FIG. 7 is a sectional view showing the die casting apparatus of Embodiment 4 in section. In this embodiment, instead of the detector 74 of the third embodiment, a pressure detector 60 capable of detecting the working hydraulic pressure of the injection cylinder 50 during the filling of the molten metal is used as in the first embodiment. That is, in die casting, the shut-off valve 7 having the slits 72 similar to those in the third embodiment is formed.
0 is advanced into the molds 10 and 12, and the injection device 4
The plunger 44 of 0 is moved at a low speed to melt the molten metal 32
Fill the inside of the container by low speed injection. When the molten metal reaches the shut-off valve 70, the filling pressure rapidly rises, and this pressure change acts as a reaction force against the piston 52 of the injection cylinder 50 through the plunger 44 of the injection device 40. Therefore, the working oil pressure of the injection cylinder 50 rises, which is detected by the pressure detector 60. The control signal transmitted from the control circuit 56 on the basis of this detection signal switches the direction of the working hydraulic pressure acting on the piston 82 of the shutoff cylinder 80 as in the case of the third embodiment, thereby switching the shutoff valve. 70 is a mold 10,1
At the same time, the working hydraulic pressure for the piston 52 of the injection cylinder 50 is switched to a high pressure, and the molten metal is filled into the cavity 30 by high-speed injection.

Also in the fourth embodiment, since the melt when the runner 32 is filled by low-speed injection is suppressed by the shut-off valve 70, the pressure of the melt when the runner 32 is filled up is suppressed. The change (increase) becomes more prominent.
Therefore, the timing at which the molten metal injection speed is switched from low speed to high speed becomes more accurate based on the measurement result of the pressure detector 60.

Embodiment 5 (corresponding to the invention described in claim 5 ) FIG. 8 is a sectional view showing a die casting apparatus of Embodiment 5 in section, and FIG. 9 is an enlarged sectional view showing a part of FIG. Is. As shown in these drawings, in the shutoff valve 70, a gas vent passage 90 is formed from the inside of the molds 10 and 12 to the side of the shutoff cylinder 80 where the shutoff cylinder 80 is connected to the piston 82. A plurality of ends of the shut-off valve 70 located inside the molds 10 and 12 are connected to the gas vent passage 90 and are opened to the runner 32 side in the molds 10 and 12. A gas vent hole 92 is formed. The diameter b of each of the gas vent holes 92 is such that air or gas is allowed to pass from the runner 32 to the gas vent passage 90 while the shutoff valve 70 is advanced into the molds 10 and 12, and the molten metal flows in. Is set to a size that can be suppressed (about 0.2 mm).

An end of the gas vent passage 90 opposite to the gas vent hole 92 is open to the atmosphere through a space outside the hydraulic chamber of the shutoff cylinder 80. Further, as shown in FIG. 8, in the gas vent passage 90,
A flow rate measuring device 94 capable of measuring the change in the flow rate of the gas flowing therein is provided. The electric signal output from the flow rate measuring device 94 is sent to the control circuit 56 shown in FIG. 8, and from this control circuit 56, the hydraulic control valve 58 of the injection cylinder 50 and the hydraulic control valve of the shut-off cylinder 80. A control signal is transmitted to each 84.

Also in this fifth embodiment, during die casting, the plunger 44 of the injection device 40 is moved at a low speed while the shutoff valve 70 is advanced into the molds 10 and 12 to melt the molten metal 32. Fill the inside of the container by low speed injection. At this time, the gas generated from the air or the molten metal in the sleeve 42 of the injection device 40 is discharged from the shutoff valve 7
From each of the gas vent holes 92 of No. 0, it is discharged to the atmosphere through the gas vent passage 90. When the molten metal reaches the shut-off valve 70 and adheres to the gas vent holes 92, the flow rate of the gas flowing through the gas vent passage 90 up to that point becomes zero or drastically decreases. Detected at 94. Based on this detection signal, the control signal transmitted from the control circuit 56 switches the direction of the hydraulic pressure acting on the piston 82 of the shut-off cylinder 80, as in the third and fourth embodiments, to change the direction. The shut-off valve 70 retracts from the inside of the molds 10 and 12, and at the same time, the working hydraulic pressure for the piston 52 of the injection cylinder 50 is switched to high pressure, and the molten metal is filled into the cavity 30 by high-speed injection.

[0033]

According to the present invention, the injection speed of the molten metal can be accurately controlled according to the filling amount of the molten metal in the mold without being affected by variations in the amount of the molten metal supplied to the injection device. It is possible to eliminate the occurrence of casting defects due to an appropriate injection speed. When a shut-off valve is used, the molten metal filled in the mold by low-speed injection is surely suppressed by this shut-off valve, and the rapid change in the molten metal pressure caused by the shut-off valve is detected. , It is possible to switch the injection speed of the molten metal at a more accurate timing.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a partial cross section of a die casting apparatus.

FIG. 2 is a configuration diagram showing a part of FIG. 1 in an enlarged cross section.

FIG. 3 is a characteristic diagram showing a relationship between a molten metal filling pressure P and a time T.

FIG. 4 is a configuration diagram showing a cross section of a die casting apparatus according to a second embodiment.

FIG. 5 is a sectional view showing the die casting apparatus of Example 3 in section.

FIG. 6 is an enlarged plan view showing a part of the shutoff valve.

FIG. 7 is a configuration diagram showing a cross section of a die casting apparatus according to a fourth embodiment.

FIG. 8 is a sectional view showing the die casting apparatus of Example 5 in section.

9 is a sectional view showing a part of FIG. 8 in an enlarged manner.

[Explanation of symbols]

10,12 mold 34 Weir 40 injection device 44 Plunger 70 Shut-off valve 90 Degassing passage 92 Gas vent hole

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B22D 17 / 32,17 / 20 B29C 45/77

Claims (5)

(57) [Claims] 1. When a molten metal reaches a weir in a mold set by a casting method , a pressure change of the molten metal is detected.
Then , based on this detection , the injection speed control method for die casting is characterized in that the injection speed of the molten metal by the injection device is switched from low speed to high speed. 2. A shut-off valve is advanced near the weir in the mold set by the casting method, and it is detected that the molten metal has actually reached this shut-off valve, and the shut-off is performed based on that. An injection speed control method for die casting, characterized in that the valve is retracted from the mold and the injection speed of the molten metal by the injection device is switched from low speed to high speed. 3. The injection speed control method according to claim 2, wherein the pressure change of the molten metal suppressed by the shutoff valve is measured, and the arrival of the molten metal at the shutoff valve is detected based on the measured value. A method for controlling injection speed in die casting, characterized by: 4. The die casting according to claim 2, wherein the temperature change of the shutoff valve is measured, and the arrival of the molten metal at the shutoff valve is detected based on the measured value. Casting injection speed control method. 5. The injection speed control method according to claim 2, wherein the shut-off valve has a gas vent hole communicating with a gas vent passage open to the atmosphere, and the gas vent hole is formed by closing the gas vent hole with molten metal. An injection speed control method for die casting, characterized by measuring a change in gas flow rate in a passage and detecting that the molten metal has reached a shut-off valve based on the measured value.