JPH0218667B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an injection device for injecting molten metal injected into an injection sleeve into a cavity of a mold in a die casting machine.

[Conventional technology]

Casting using a die-casting machine has traditionally been widely used as a method for manufacturing precision products in large quantities, but this type of forging involves filling the cavity of a mold with molten metal 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 eliminate such inconveniences, the present applicant has developed a mold that removes gas from the mold cavity during casting, eliminates gas entrainment, and obtains a sound die-cast product in accordance with Utility Application No. 107265/1983. We developed and proposed a degassing device.

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, 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. from outside the cavity may be sucked into the cavity, or molten metal from the injection sleeve may be sucked into the cavity before the degree of vacuum has increased, resulting in lubrication. Impurities such as chemicals may get mixed into the product and reduce the quality of fine refining, or moisture may come into contact with the injected molten metal and gasify, creating cavities that may prevent a sufficient vacuum effect from being achieved. If the molten metal is sucked in before the specified degree of vacuum is reached, gas may be drawn in.
Alternatively, there was a problem in that the product did not mix sufficiently with the molten metal injected in the subsequent high-speed injection region, and the appearance of the product was impaired. In addition, 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 surface of the plunger tip, as shown in the cross-sectional view of the vicinity of the plunger tip in Figure 9, if suction is performed to reduce the pressure, it will be insulated. Due to the cooling and upward suction action, the extremely solid layer 1 shrinks and floats up from the end face of the plunger tip 2 together with the molten metal, and the central part of the thin solidified layer 1 is torn by the suction force, forming the hole 1a.
As a result, external air freely enters the mold cavity through the gap between the plunger tip 2 and the injection sleeve 2 and the hole 1a in the torn solidified layer 1, making it difficult to shut off.

[Means for solving problems]

In order to solve these problems, the present invention provides a vacuum suction device that suctions and exhausts the gas in the mold cavity while the molten metal for injection is supplied into the injection sleeve. A recessed portion having an inner circumferential surface having a smaller diameter than the outer circumferential diameter of the plunger tip and parallel to the axis was provided on the molten metal contacting end surface of the plunger tip.

[Effect]

With this configuration, when the gas in the mold cavity is suctioned and discharged just before the start of molten metal injection, the solidified layer of molten metal formed on the end face side of the plunger sticks closely to the end face, blocking the intrusion of outside air. Even if outside air enters between the end face of the plunger and the coagulated layer, the perpendicular inner circumferential surface of the recess blocks the air from entering the recess, and the coagulated layer is not torn.

[Example] Figures 1 to 8 show an example of the injection device for a die-casting machine according to the present invention. Enlarged sectional view, Figure 3 is a sectional view AA in Figure 2, Figure 4 is a BB sectional view in Figure 2, Figure 5 is a CC sectional view in Figure 2, and Figure 6 is a partially broken section of the plunger tip. An enlarged front view, FIG. 7 is a vertical sectional view of the mold gas venting device, and FIG. 8 is a DD sectional view of FIG. 7. In the figure, a fixed mold 11 and a movable mold 12 are joined and clamped at a dividing surface 13, and a cavity 14 and a constriction 15 are provided 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.
is located directly below. The injection cylinder 18 is equipped with a piston rod 19 that moves forward and backward using hydraulic pressure.
A plunger 20, detailed in FIGS. 2 to 6, is concentrically connected to its working end 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) toward and away from the fixed sleeve 17. The plunger tip 23 of the head of the plunger 20 slides into its inner hole 22a. The casting sleeve 22 is movably fitted, and the casting sleeve 22 is removed from the fixed sleeve 17, and while the plunger tip 23 is fitted, it is tilted together with the injection cylinder 18 by a tilting cylinder (not shown) to inject the molten metal into the casting sleeve 22. It is configured as follows. After pouring the molten metal, 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.

Therefore, details of the plunger tip 23 will be explained. A plunger rod 24 connected to the piston rod 19 with a coupling 21 includes, from above, a screw hole 24a, a pressure reducing pipe support hole 24b, an air passage hole 24
The inner hole is formed in steps in the order of c. has been done. A pair of upper and lower adapters 26 and 27 are attached to the central threadless portion 25b of the threaded pipe 25.
is loosely installed, and the upper threaded part 25 of the threaded pipe 25
The plunger tip 23 and the plunger rod 24, which are screwed into the plunger tip 23 and the plunger rod 24, are clamped and fixed. 28 is a holding cylinder 28a and a pipe 2 welded thereto.
The tube 28b is inserted from the bottom hole 24d side and the holding cylinder 28a is fitted to the upper end of the bottom hole 24d.
4c, and its upper portion is fitted into the pressure reducing tube support hole 24b. Further, 29 is a water-cooled tube consisting of a holding shaft 29a and a tube 29b welded to the holding shaft 29a,
The holding shaft 29a is fitted into the bottom hole 24d to hold down the holding cylinder 28a from below, and the pipe 29b passes through the holding cylinder 28a, the pipe 28b, and the threaded pipe 25, and its tip is inserted into the space 23a of the plunger tip 23. I'm making you come. Reference numeral 30 indicates six O-rings as sealing materials provided at various locations. 30a is an oil supply port for sliding lubrication of the plunger tip 23.

Annular groove 2 provided on the outer periphery of plunger tip 23
3b and an annular groove 26a provided in the adapter 26 are communicated with each other through an air passage 23c.
The annular groove 27a provided in the wire mesh filter 3
1 through an air passage 27b. Air passage hole 24c of plunger rod 24 and pipe 28
b and the annular groove 2.
7a through an air passage 33, and a suction hole 34 opened at the lower end of the air passage 32 is connected to a piping 35 of a pneumatic circuit (described later) shown in FIG.
is connected. On the other hand, the water cooling pipe 29b
The lower end opening is connected to the cold water passage 29d and the annular groove 29c.
The upper end opening is connected to the cold water inlet 35b through the space 23a, and a cold water passage 36 and water channel 37 extending downward around the pipe 29b.
It communicates with a cold water outlet 39 via an annular groove 38 . The cold water inlet 35b is connected to a pump or the like through a flexible hose or the like, and the cold water supplied to the cold water inlet 35b by the operation of the pump rises in the pipe 29b and fills the space 23a, and the plunger tip 23 After cooling, the water flows down the cold water passage 36 and is drained from the cold water outlet 39.

The plunger tip 23 has a recess 23.
d is provided on the end surface of the injection sleeve 22 on the side that contacts the molten metal 80. This recess 23d is
It is a circular hole having a smaller diameter than the outer circumferential diameter of the plunger 23, and has an inner circumferential surface 23e parallel to the axis of the plunger tip 23. Further, the molten metal contacting end of the plunger tip 23 is formed in a tapered shape, and an annular recess 23f is formed between this molten metal contacting end and the inner hole 22a of the injection sleeve 22. 23g is a chamfered portion to which a wrench is applied when screwing into the threaded pipe 25.

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 path 40 which detours to the side.
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. The reason why the tension spring 52 is provided here is to prevent the valve body 56 from closing once due to the pressure of the molten metal.
This is because a does not open again unless an external force is applied. Below the return rod 51 is a cylindrical portion 53.
A valve guide 53 is attached to the spool 46, and is integrally formed with a valve guide 53a and a pair of screw hole portions 53b. The cylindrical portion 53a has an upper end screw portion attached to the return rod 51.
A valve rod 56 screwed into the screw hole is slidably supported. A valve body 56a is provided at the lower end of the valve stem 56 and seats on the valve seat 49 when the valve stem 56 rises. and the inner chamber of the spool 46, the gas vent groove 41,
It is configured to be cut off from the bypass 48. 57 is a ball that engages with the groove 56b of the valve stem 56 by the bias of the compression coil spring 58, and the pressing force of the ball 57 against the valve stem 56 is generated by the action of the bolt 54 and the nut 55; ball 5
7. A locking mechanism is formed by a compression coil spring 58, a bolt 54, etc., and the valve body 56a is kept open by the action of this locking mechanism. Of course, if the inertial force of the molten metal acts on the open valve body 56a, the ball 57 will move back as the valve stem 56 retreats, and the valve body 56a will immediately close. Note that the valve body 56a is opened by pushing down the rod portion 51a of the return rod 51. Reference numeral 59 is a stopper that restricts the upper limit of the rise of the spool 46 which is raised by the operation of the cylinder 44, and is fixed to the bracket 43. An exhaust hole 60 is opened at the lower end of the spool 46, and this exhaust hole 60 is connected to the piping 60 of the pneumatic circuit (described later) shown in FIG.
Connected to 1.

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 pipes 61 and 35 via filters 68 and 69, respectively. Solenoid valves 70 and 71 are disposed on the pipes 64 and 65, respectively, and from the state shown in the figure, the solenoid valve 7
When the solenoid No. 0 is energized, the air inside the plunger 20 is sucked, and when the solenoid of the electromagnetic valve 71 is energized, the air inside the cavity 14 is sucked through the gas venting device 42. The degree of vacuum at this time 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, and this is achieved by providing the 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. In addition, flexible hose 35
The pipe 35 having a diameter is made as short as possible and has a relatively large pipe diameter, for example, 1 inch.

Further, the other ports of the solenoid valves 70 and 71 are connected to piping 74 and 75 equipped with solenoid valves 72 and 73, respectively.
are joined to a pipe 77 equipped with a variable throttle valve 76 and connected to, for example, an air compressor 78 in a factory. Then, close the solenoid valves 70 and 71 and close the solenoid valve 7.
When 2, 73 is opened, high pressure air flows into plunger 2.
0 and a 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 to the illustrated position and the mold is clamped, and the gas venting device 4
The second cylinder 44 is operated to engage the spool 46 into the spool holes of the molds 11 and 12 as shown. At this time, the piston rod 19 of the injection cylinder 18 and the injection sleeve 22 are lowered, so the injection cylinder 18 is tilted, the plunger 20 injects the molten metal into the lowered injection sleeve 22, and then raised again. Injection sleeve 22
is raised to engage the fixation sleeve 17 as shown. After evacuation, oil is supplied to the injection cylinder 18 and the piston rod 19 is raised, causing the plunger 20 to rise and injection of molten metal, indicated by reference numeral 80 in FIG. 2, to begin. At this time, cold water is supplied to the plunger 20 from the cold water inlet 35b, and this cold water rises in the pipe 29b and then overflows into the space 23a and flows into the cold water passage 36.
Since the water is flowing down inside, the plunger tip 23 and the plunger rod 24 are cooled.
Furthermore, the injection sleeve 22 is also cooled from the outside by a cooling device (not shown). Therefore, the upper end surface of the plunger tip 23 and the inner wall surface of the injection sleeve 22 that follows it are different from those shown in FIG.
A solidified layer indicated by reference numeral 1 in the figure is generated by the solidification of the molten metal. Since the inside of the vacuum tank 66 and the auxiliary vacuum tank 67 have been previously depressurized by suction with the vacuum pump 62, when the solenoid valve 70 is first opened before starting injection, negative pressure is applied to the suction hole 34 of the plunger rod 24. The air in the annular groove 23b of the plunger tip 23 flows through the air passage 2.
3c, annular groove 26a, filter 31, air passage 2
7b, the annular groove 27a, the air passage 33, and the air passage 32. Further, when the solenoid valve 71 is opened at the same time, the valve body 56a of the gas venting device 42 is open at this time, so that the gas in the cavity 14 is released from the gas venting path 40 and the gas venting groove 4.
1. The gas inside the cavity 14 is suctioned through the exhaust hole 60 via the bypass 48 and exhausted. In this way, the plunger 20 side and the gas venting device 42
By suctioning from both sides, the vacuum level inside the cavity 14 and the gap between the injection sleeve 22 and the plunger tip 23 will be the same.
By making the degree of vacuum higher than the degree of vacuum shown in FIG. Solidified layer 1 is formed by cooling to 300~400℃
becomes thicker. This prevents outside air from entering through the gap between the injection sleeve 22 and the plunger tip 23. Also, before injection of molten metal, cavity 14
Molten metal will not get inside. Furthermore, in this device, the recess 23d is provided on the end surface of the plunger tip 23 on the molten metal contact side, and the inner circumferential surface 23e of the recess is made parallel to the axis of the plunger tip 23, so that, for example, the solidified layer 1 can be brought into close contact with the end surface of the plunger tip 23. Even if it floats slightly, the solidified layer 1
The part that enters the recess 23d has its peripheral surface in close contact with the vertical inner peripheral surface 23e, so that air is blocked by this contact part and flows into the gap between the bottom of the recess 23d and the solidified layer 1. Since it does not penetrate, the solidified layer 1
The center part of the membrane does not tear due to air pressure, which further reduces the intrusion of outside air and the insertion of molten metal, and since the membrane does not tear, the intrusion of lubricating oil, which can cause defective products, is also blocked. Ru. Further, by forming the annular recess 23f on the end face of the plunger tip 23, the solidified layer 1
is formed so as to fit into this recess 23f, so there is no risk that the solidified layer 1 will break from this location and enter the molten metal, unlike when there is no recess 23f.

After creating a vacuum inside the cavity 14 in this way, the injection operation begins, and when the plunger 23 is advanced while degassing, the molten metal 80 in the injection sleeve 22 spreads between the fixed sleeve 17 and the constricted portion 15. is injected into the cavity 14,
When the cavity 14 is filled with the molten metal 80, the molten metal 80 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 greater than the impact applied by the gas to the valve element 56a, since the mass of the molten metal 80 is extremely large compared to the mass of the gas and has a large inertia. Compression coil spring 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 8
Since the valve body 56a pushed up at 0 is pulled upward by the tension spring 52, the raised position is maintained and the exhaust passage is reliably closed by the valve body 56a. Note that when injecting the molten metal 80, the solidified layer 1
When the plunger tip 23 rises, it is crushed between its end face and the end face in front of the constriction part 15, but by providing the thin constriction part 15, the crushed solidified layer 1 does not enter the cavity 14.

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.

In this embodiment, the suction on the gas venting device 42 side and the suction on the plunger 20 side are performed at the same time, but in order to more reliably block the intrusion of outside air, It is preferable to set the timing regulating device to delay the suction on the plunger 20 side by, for example, about 0.2 seconds to 1 second, preferably about 0.3 to 0.5 seconds.

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 evacuation can be performed immediately after the molten metal inlet of the injection sleeve is closed after the start of injection. For example, the same method can be applied to a horizontal casting type die-casting machine.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, an injection device for a die-casting machine is provided with a vacuum suction device for sucking and discharging gas in the mold cavity while molten metal for injection is being supplied into the injection sleeve. , is formed on the end surface side of the plunger tip by providing a recess on the molten metal contacting end surface of the plunger tip that slides within the injection sleeve and having an inner circumferential surface that is smaller in diameter than the outer circumferential diameter of the plunger tip and parallel to the axis. The solidified layer of molten metal adheres to this end face, and becomes thicker and stronger as it cools, so outside air that attempts to enter through the gap between the plunger tip and the injection sleeve is blocked by this solidified layer and is prevented from entering. Moreover, even if the adhesion of the coagulated layer to the end face of the plunger is poor and outside air may enter between the end face of the plunger and the periphery of the coagulated layer, this is blocked by the vertical inner circumferential surface of the recess and the central part of the coagulated layer is Since the molten metal does not tear, the intrusion of outside air is further reduced, molten metal is no longer inserted into the mold cavity, and impurities are no longer mixed into the molten metal, resulting in good injection and smooth casting. Product quality is significantly improved.

[Brief explanation of drawings]

1 to 8 show an embodiment of the injection device for a die-casting machine according to the present invention, FIG. 1 is a schematic sectional view and pneumatic piping diagram, FIG. 2 is an enlarged sectional view of an injection sleeve and a plunger, Fig. 3 is a sectional view AA in Fig. 2, Fig. 4 is a sectional view BB in Fig. 2, Fig. 5 is a sectional view CC in Fig. 2, Fig. 6 is an enlarged partially broken front view of the plunger tip, FIG. 7 is a longitudinal sectional view of a mold gas venting device, FIG. 8 is a DD sectional view of FIG. 7, and FIG. 9 is an explanatory diagram of the state of a solidified layer in a conventional injection device. 11...Fixed mold, 12...Movable mold, 14...
...Cavity, 20...Plunger, 22...Injection sleeve, 23...Plunger tip, 23b
...Annular groove, 23c...Air passage, 23d...Recess, 23e...Inner peripheral surface, 24...Plunger rod, 24c...Air passage hole, 26a, 27a...
Annular groove, 27b, 32, 33...Air passage, 42
...Gas venting device, 62...Vacuum pump, 66...
...Vacuum tank, 67...Auxiliary vacuum tank, 80...
...molten metal.

Claims (1)

[Claims] 1. A vacuum suction device is provided for suctioning and discharging the gas in the mold cavity while the molten metal for injection is supplied into the injection sleeve into which the plunger tip is slidably inserted, and a vacuum suction device is provided on the molten metal contacting end surface of the plunger tip. 1. An injection device for a die-casting machine, comprising a recessed portion having an inner circumferential surface that is smaller in diameter than the outer circumferential diameter and parallel to an axis.