JPH0159066B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The industrial application field of the present invention relates to a molten metal casting apparatus, and more specifically, a molten metal casting apparatus that performs casting by reducing the pressure inside a mold cavity. It is a device.

[Conventional technology]

Casting using a die-casting machine has traditionally been widely used as a method for manufacturing precision products in large quantities.In this type of casting, molten metal is filled into the cavity of a mold at high speed and high pressure. Since the gas may not escape sufficiently and may mix with molten metal and remain in the product as voids, it may not be suitable for products where integrity without voids is important.

In order to solve this inconvenience, the present applicant has proposed Utility Application No. 56-107265 (Utility Model Application No. 57-13873).
We have developed and proposed a degassing device for molds that removes gas from the mold cavity during casting, eliminates gas entrainment, and produces healthy die-cast products.

This device is equipped with a gas vent valve in the gas exhaust path leading from the mold cavity to the outside of the mold, and when the valve is open, molten metal is injected into the cavity, and the gas with a small mass in the cavity is exhausted. When the molten metal has finished being discharged through the gas passage, the inertial force of the large mass of the molten metal that has entered the gas exhaust passage from inside the cavity acts on the valve to close it, thereby blocking the outflow of the molten metal. Therefore, the gas inside the mold can be reliably and easily vented.

The applicant has also developed a reduced-pressure or vacuum-type die-casting method and an apparatus therefor, in which the gas in the mold cavity is actively exhausted by connecting the gas exhaust path to a vacuum generator. This reduced pressure die casting method reduces the pressure by suctioning an amount of gas from the outside that is greater than the amount of gas that flows into the cavity from outside the mold through the gap, thereby eliminating gas from inside the mold. It can be made more reliable.

[Problem that the invention seeks to solve]

However, in such conventional casting methods, gas flows from the outside to the inside in the gap between the injection sleeve and the plunger tip due to the difference between the amount of gas discharged from the cavity and the amount of gas flowing into the cavity. As a result of this flow, as the vacuum is drawn, some of the molten metal in the injection sleeve is randomly sucked up into the cavity in a state close to foaming before injection, and a thin solidified layer is formed along the inner surface of the cavity. arise. Therefore, after reaching this state, a proper injection product cannot be obtained even if injection is performed. Furthermore, even if injection is attempted, moisture, mold release agent, lubricant, etc. outside the cavity may be sucked into the cavity, or molten metal inside the injection sleeve may be sucked into the cavity before the degree of vacuum has increased. Impurities such as lubricants may get mixed into the product, reducing the quality of the product, or moisture may come into contact with the injected molten metal and gasify, creating cavities that may prevent sufficient vacuum effectiveness from being achieved. Otherwise, the molten metal may be sucked in before the specified degree of vacuum is reached, which may entrain gas, or may not mix well with the molten metal injected in the subsequent high-speed injection region, which may affect the appearance of the product. There was a problem with the damage. Furthermore, even if an attempt is made to block the intrusion of air by a solidified layer of molten metal that is formed in close contact with the end face of the plunger tip,
As shown in the cross-sectional view near the plunger tip, when the cavity is suctioned to reduce the pressure, the molten metal is lifted because the degree of vacuum between the plunger tip and the casting sleeve is lower than the degree of vacuum in the cavity. Due to the force, the molten metal floats up from the end of the plunger tip, and the air that flows into the bottom of the molten metal and the end of the plunger tips insulates the bottom of the molten metal, and the solidified layer that has formed on the bottom of the molten metal softens due to the heat of the molten metal. The center part ruptures due to the air pressure difference between the cavity and the end of the plunger tip.
External air freely entered the mold cavity through the gap between the plunger tip 2 and the injection sleeve 3 and through the holes in the torn solidified layer 1, making it difficult to shut off.

In addition, the injection sleeve 3 swells to some extent in a cylindrical shape due to the heat, but in the case of the conventional plunger 2a with only one plunger tip 2 at the tip,
When the plunger tip 2 moved forward to the center of the injection sleeve 3, a gap was created between the outer circumferential surface of the plunger tip 2 and the inner circumferential surface of the injection sleeve 3, and the degree of vacuum dropped.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention has a plunger tip provided at the tip.
A structure is adopted in which a block part that can slide in contact with the inner surface of the sleeve is provided apart from the plunger tip, and a vacuum suction port is provided in the block part.

[Effect]

If such a structure is adopted, the chip will be formed in two stages, and the gap between the chip and the sleeve will be sealed twice, making it difficult to suction air, and it will also be difficult to vacuum the chip in the latter stage. Since the opening is provided, even if the air inside the cavity is sucked from the gas venting device side, outside air will not mix into the molten metal inside the cavity.

〔Example〕

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings.

1 to 4 are for explaining one embodiment of the present invention. In the figures, a fixed mold 11 and a movable mold 1 are shown.
2 are joined at the dividing surface 13 and molded together, and there is a cavity 14 and a constriction 15 inside.
and vertical holes 16 are formed on both sides of the dividing surface 13, and a fixing sleeve 17 is fitted into the vertical holes 16. The die casting machine of this embodiment is of a horizontal mold clamping and vertical casting type, and the mold clamping and mold opening are performed by moving the movable mold 12 in the horizontal direction. 1
It is located directly below 2. The injection cylinder 18 is equipped with a piston rod 19 that moves forward and backward under hydraulic pressure, and a plunger 20 is concentrically connected to the working end of the piston rod 19 by a coupling 21. Reference numeral 22 denotes an injection sleeve formed to have the same diameter as the fixed sleeve 17 and moved up and down by a cylinder (not shown) to move toward and away from the fixed sleeve 17, and has an inner hole 22a.
A plunger tip 23 at the head of the plunger 20 is slidably fitted, and the casting sleeve 22 is removed from the fixed sleeve 17 and the plunger tip 23 is inserted into the head of the plunger 20 .
The cast sleeve 22 is inserted and rotated together with the injection cylinder 18 by a tilting cylinder (not shown).
It is configured to inject molten metal into the tank. After pouring, the injection cylinder 18 is erected, the casting sleeve 22 is inserted into the fixed sleeve 17, and the piston rod 19 is advanced by hydraulic pressure, so that the plunger tip 23 injects the molten metal into the cavity 14.

On the other hand, a block 24 having approximately the same diameter as the plunger tip 23 is provided at a predetermined distance behind the plunger tip 23.

A passage 25 is formed through the center of the plunger 20 until it reaches the plunger tip 23, and a space 23 is formed in the center of the plunger tip 23.
a is formed.

The passage 25 and the space 23a communicate with each other, and a pipe 26 is arranged concentrically in the passage 25 so as to reach into the space 23a.

By providing this piping 26, a cooling water passage 26a is formed concentrically, and cooling water is supplied to the passage 26a from a supply port 26b formed on the side surface of the plunger 20. After the chips 23 are cooled, they are discharged from the discharge port 26c.

Further, around the block 24, there is an annular groove 24a.
is formed around the entire circumference, and this annular groove 2
4a communicates with a passage 24b formed through the plunger 20.

The lower end of this passage 24b is connected to a gas venting device, which will be described later, including a flexible hose 35a and piping 35 via an opening 24c.

Next, the mold degassing device will be explained. On the outer periphery of the cavity 14 of both the molds 11 and 12,
A degassing path 40 and a degassing groove 41 communicating with this are formed on both sides of the dividing surface 13, and a mold degassing device, designated as a whole by reference numeral 42, is located directly above the degassing groove 41, for example. It is fixed to the movable mold 12 side. That is, the cylinder 4 is attached to the upper end of the bracket 43 fixed to the movable mold 12.
A cylindrical spool 46 connects the lower end of the piston rod 46, which is the active end of the piston rod 45 that moves back and forth with the fluid pressure, to the lower end of the piston rod 45.
1 and 12 so that they can be inserted and removed freely. And when mold clamping and mold opening,
The spool 46 is inserted into and removed from the molds 11 and 12 via the piston rod 45 by the operation of the cylinder 44. Mold 11,
Below the spool 46 inserted into the spool 12, there is a valve chamber 47, a degassing groove 41 which detours laterally.
A bypass 48 is provided to communicate between the spool 46 and a valve seat 49 facing the valve chamber 47 is formed on the lower end surface of the spool 46. A pair of elongated holes 50 provided in the outer peripheral wall of the spool 46 have a return rod 51.
Both rod portions 51a of the piston rod 45 are slidably engaged with each other, and between the return rod 51 and the flange portion of the piston rod 45, there is a tension spring 52, a cylinder, a solenoid device, and a gravity spring that urges the return rod 51 upward. Components such as equipment are strung up. Below the return rod 51, a valve guide 53 integrally formed with a cylindrical portion 53a and a pair of screw hole portions 53b is fixed to the spool 46 with the screw hole portion 53b attached inside the elongated hole 50, A valve rod 56 whose upper end threaded portion is screwed into a screw hole of the return rod 51 is slidably supported on the cylindrical portion 53a. At the lower end of the valve stem 56 is a valve body 56 that seats on the valve seat 49 as it rises.
a is provided, and the valve body 56a, which had been opened by the gas pressure in the cavity 14, is seated due to the inertia of the molten metal advancing at high speed from the cavity 14, and the valve body 56a is seated in the inner chamber of the spool 46 and the gas vent groove. 41 and bypass 48. Reference numeral 57 denotes a ball that engages with the groove 56b of the valve stem 56 under the bias of a compression coil spring 58, 54 a bolt, and 55 a nut, which form a locking mechanism. The valve body 56a, once closed by the pressure of the molten metal, is configured so that it will not open again due to the action of members such as the tension spring 52 unless an external force is applied. Note that the valve body 56a is opened by pushing down 51a with the return rod 51. 59
is a stopper which is fixed to the bracket 43 and restricts the upper limit of the rise of the return rod 51a, which is raised together with the spool 46 by the operation of the cylinder 44. An exhaust hole 60 is opened at the lower end of the spool 46, and this exhaust hole 60 is connected to a second exhaust hole 60.
It is connected to piping 61 of the pneumatic circuit shown in the figure (described later).

Next, the plunger 20 and the gas venting device 42
The pneumatic circuit will be explained based on FIG. The pipe 63 connected to the vacuum pump 62 is branched into a pipe 64 and a pipe 65 in the middle, and the pipe 63,
64, a vacuum tank 66 and an auxiliary vacuum tank 6 are installed.
7 are provided respectively, and the piping 6
3 and 64 are connected to the pipe 6 via filters 68 and 69.
1 and 35, respectively. Solenoid valves 70 and 71 are disposed on the pipes 64 and 65, respectively. When the solenoid of the solenoid valve 70 is excited from the state shown in the figure, the air in the plunger 20 is sucked, and the solenoid of the solenoid valve 71 is When excited, the cavity 1 is energized through the gas venting device 42.
The air inside 4 is sucked. In this case, the suction on the gas venting device 42 side is set to be delayed by about 0.2 to 1 second, preferably about 0.3 to 0.5 seconds, behind the suction on the plunger 20 side, based on a command from a timing regulating device (not shown). Further, the degree of vacuum is set to, for example, 200 to 300 Torr on the plunger 20 side and 150 to 250 Torr on the gas venting device 42 side.
This is achieved by providing an auxiliary vacuum tank 67. The auxiliary vacuum tank 67 is provided as close as possible to the plunger 20 in consideration of resistance generated in relatively thin piping sections and passages during vacuum suction. Further, the piping 35 having the flexible hose 35a is made as short as possible and has a relatively large pipe diameter, for example, 1 inch, and the other ports of the solenoid valves 70 and 71 are provided with solenoid valves 72 and 73. These pipes 74 and 75 are connected to a pipe 77 provided with a variable throttle valve 76, and connected to, for example, an air compressor 78 in a factory. Then, the solenoid valves 70 and 71 are closed and the solenoid valves 72 and 73 are closed.
By opening, high pressure air is sent to the plunger 20 and the degassing device 42 for spraying for internal cleaning.

A casting method using the die casting machine configured as above will be explained. The movable mold 12 is moved and clamped, and the cylinder 4 of the degassing device 42 is moved.
4 to engage the spool 46 into the spool holes of the molds 11 and 12 as shown in FIG. At this time, the piston rod 19 and injection sleeve 22 of the injection cylinder 18 are lowered, so the injection cylinder 18 is tilted and the plunger 2
After injecting the molten metal into the injection sleeve 22, which is facing downward, and raising it up again, the injection sleeve 22 is raised and engaged with the fixed sleeve 17 as shown in FIG. After evacuation, oil is supplied to the injection cylinder 18 and the piston rod 19 is raised, the plunger 20 is raised and the injection of molten metal indicated by reference numeral 4 in FIG. 1 is started.
At this time, cold water is being supplied to the plunger 20 from the cold water inlet 26c, and this cold water rises inside the pipe 26, overflows into the space 23a, and flows down inside the cold water passage 26b. Block 24 as well as plunger 20 are cooled. Furthermore, the injection sleeve 22 is also cooled from the outside by a cooling device (not shown).
Therefore, a solidified layer is formed on the upper end surface of the plunger tip 23 and the inner wall surface of the injection sleeve 22 following the upper end surface due to solidification of the molten metal, which is indicated by reference numeral 1 in FIG. Then, inside the vacuum tank 60 and the auxiliary tank 67
Since the pressure inside the injection sleeve has been reduced in advance by suction with the vacuum pump 62, when injection starts at low speed and the groove 24a provided in the block 24 enters the injection sleeve 22, first, when the solenoid valve 70 is opened. Negative pressure acts on the suction hole 24c of the plunger 20,
The annular groove 24a of the block 24 becomes under negative pressure. At this time, the upper part of the molten metal in the injection sleeve 22 was slightly inserted into the constricted portions 15 of the molds 11 and 12. .

As a result, when the solenoid valve 71 is opened with a delay of, for example, 0.3 to 0.5 seconds, the gas venting device 4
Since valve body 56a of No. 2 is open, cavity No. 1
The gas inside 4 is released through a gas venting path 40, a gas venting groove 41,
The gas inside the cavity 14 is suctioned through the exhaust hole 60 via the bypass 48 and exhausted. By suctioning from both the plunger 20 side and the gas venting device 42 side in this way, the inside of the cavity 14 and the gaps between the injection sleeve 22, the plunger tip 23, and the block 24, etc., have the same degree of vacuum. However, by suctioning the plunger 20 side slightly faster and by making the degree of vacuum on the plunger 20 side larger than the degree of vacuum on the gas venting device 42 side, the solidified layer 1 is removed from the plunger as shown in FIG. The solidified layer 1 is strengthened by closely adhering to the end face of the tip 23 and the annular recess around it, and is also cooled to 300 to 400 DEG C. as the plunger tip 23 is cooled, thereby increasing the thickness of the solidified layer 1. When the injection sleeve 22 is slightly swollen into a pyramid shape due to heat and the plunger tip 23 is located at the center of the swollen injection sleeve 22, a block 24 is inserted at the lower end of the injection sleeve 22.
At that time, a vacuum is drawn from block 24. These prevent outside air from entering through the gap between the injection sleeve 22 and the plunger tip 23. Moreover, the molten metal does not get inserted into the cavity 14 before the molten metal is injected.

After creating a vacuum inside the cavity 14 in this way, the high-speed injection operation is started, and when the plunger 23 is advanced while degassing, the molten metal 4 in the injection sleeve 22 is injected into the cavity 14. When the inside is filled with molten metal 4, this molten metal 4 rises in the gas vent groove 41 and comes into contact with the lower surface of the valve body 56a together with the gas. At this time,
The impact applied to the valve element 56a is larger than the impact applied by the gas to the valve element 56a, since the mass of the molten metal 4 is extremely large compared to the mass of the gas and has a large inertia. 5
8 and rises while compressing the valve body 56a to the valve seat 4.
Block 9. Therefore, even if the molten metal 80 is blocked from flowing out from the valve seat 49 and mixes with the gas in the gas venting path 40 and the gas venting groove 41 and hits the valve body 56a discontinuously in the form of droplets, the molten metal 80 is prevented from flowing out from the valve seat 49. Molten metal 4
Since the valve element 56a pushed up is pulled upward by the tension spring 52, the upper position is maintained and the exhaust passage is reliably closed by the valve element 56a.

After being pressurized and cooled for a predetermined time with the valve body 56 a closed, the movable mold 12 is opened, and the spool 46 is raised by the cylinder 44 of the degassing device 42 to release the engagement with the movable mold 12 . Remove the product from the

Note that when the spool 46 is raised, the valve body 56
Due to the separation resistance between a and the solidified metal, only the spool 46 rises and the valve stem 56 rises with a delay.As a result, the ball 57 that had come off from the groove 56b of the valve stem 56 engages with the groove 56b again, and the next time Preparation for casting will be completed. Furthermore, at the upper limit of the spool 46, the return rod 51 contacts the stopper 59 and pushes down the valve rod 56, so that the valve body 56a is reliably opened and ready for the next casting.

Note that this embodiment shows an example in which the present invention is applied to a vertical casting type die-casting machine, but in this case, the timing of vacuuming is set immediately after the molten metal inlet of the injection sleeve is blocked with a block after the start of injection. If the process is carried out from the beginning, it can be similarly applied to a horizontal casting type die-casting machine.

〔effect〕

As is clear from the above description, according to the present invention, at the rear of the plunger tip provided at the tip,
A block portion slidable in contact with the inner surface of the injection sleeve is provided at a predetermined distance from the plunger tip,
Since the block part has a structure with a vacuum suction port, when the block part enters the injection sleeve, negative pressure can be created between the plunger part and the sleeve, and air from the outside can be removed. It can be constructed so that it does not enter the mold cavity, and it is possible to prevent the formation of cavities due to air being drawn into the molten metal.

[Brief explanation of drawings]

1 to 4 illustrate one embodiment of the present invention, and FIG. 1 is an enlarged sectional view of the plunger portion;
FIG. 2 is an air circuit diagram, FIG. 3 is a vertical side view of the degassing device, FIG. 4 is a sectional view taken along the line -- in FIG. 3, and FIG. 5 is a sectional view illustrating the conventional structure. 11...Fixed mold, 12...Movable mold, 14...
...Cavity, 20...Plunger, 22...Injection sleeve, 23...Plunger tip, 24...
... Block, 24a ... Annular groove, 24b ... Passage, 42 ... Gas venting device.

Claims (1)

[Claims] 1 Behind the plunger tip provided at the tip,
A molten metal casting device characterized in that a block that can slide in contact with the inner surface of a sleeve is provided at a predetermined distance from a plunger tip at the tip, and a vacuum suction port is provided in the block portion.