JPH0761535B2 - Degassing method for mold - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a mold degassing method for extracting gas from a mold cavity during injection molding by an injection molding device such as a die casting machine or an injection molding machine. Is.

[Prior Art] Conventionally, in an injection molding apparatus such as a die casting machine, when the melt is injected and filled into the cavity at high speed and high pressure, the gas in the cavity may not be completely exhausted and a cavity may occur in the product. The applicant of the present invention has developed a degassing device for a die that can release a large amount of gas in a short time. This degassing device has a degassing groove that communicates with the cavity, a valve that slides in the axial direction at the end of the degassing groove, and a bypass as a gas discharge passage that detours from the middle of the degassing groove to the side of the valve section. It is provided on the separation surface of the mold, and the gas in the cavity is discharged to the outside of the mold through the bypass and the valve body opening at the time of injection molding, and the injection melt enters the cavity and the end of the degassing groove. When the temperature reaches, the valve body is pushed up by the action of the melt having a large mass, and the end portion of the bypass is closed by the valve body.

However, in this degassing device, the operation of the valve body is not always satisfactory, and especially when the melt reaches the valve body discontinuously at the tip of the flow, the valve body is not sufficiently operated. Sometimes it didn't work. That is,
Even if the valve closes once due to the operation of the melt, when the gas comes next, it opens due to the action of the compression spring provided at the rear end of the valve, and then the melt comes again and tries to close the valve, Since the melt in front of the earlier valve position is about to solidify, the force of the later melt does not act directly on the valve, but on the previous melt.
At this time, there is a frictional resistance between the molten material that has been solidifying first and the mold surface around it, so the action of the molten material that comes later on the valve may weaken and the valve may not close. There was a risk that the melt coming from the bypass would enter the valve chamber through the valve opening.

Therefore, the applicant further proposed the gas venting device disclosed in Japanese Patent Publication No. 59-310. This degassing device is provided with a member such as a tension spring that biases the valve in the closing direction, a compression spring that locks the valve in the open position, and a member such as a ball. The valve is closed against the locking force of the member, and the valve body can be closed quickly and reliably when the first melt reaches the valve body.

[Problems to be Solved by the Invention] However, such a conventional gas venting device is not necessarily satisfactory in that the locking force at the open position of the valve is maintained for a long period of time. That is, the valve is repeatedly opened and closed in each injection cycle, and when it reaches thousands of times, the ball and its contact part are worn out and the valve closes before the melt comes due to the reduction of the locking force. There was a risk that the gas could not be released. On the contrary, if the contact surface of the ball becomes rough or deformed, the locking force at the valve open position becomes stronger, and even if the melt comes, the locking force exceeds the collision force and the valve will not close. Due to the fact that the melt enters the valve chamber, or because the collision force of the melt acting on the valve is small, it takes time for the valve to close even if the lock is released, and the melt enters during that time. There was a problem that it would end up.

In addition, during the injection, the inside of the cavity is vacuum-sucked through this degassing device, but at this time, it is also necessary to prevent the valve from closing due to the vacuum suction force, and the valve does not allow inertia of the melt. When closing by the action of force, it is also necessary that the valve be closed quickly with a small force.

[Means for Solving Problems] In order to solve such problems, in the present invention, it is possible to control the valve opening holding force when vacuuming the inside of the cavity through the gas venting device. As a method of degassing the mold, the gas vent valve provided at the end of the gas discharge passage communicating with the cavity is kept open when the injected melt is injected, and the gas in the cavity is discharged. After vacuum suction is performed by the vacuum suction device through the extraction valve, the force in the valve closing direction is applied to the valve by the collision force of the injected melt on the valve bottom or the acting force in the valve closing direction to perform the valve closing operation. At the time of holding the valve open state, the initial valve opening holding force for holding the gas vent valve in the valve open state is applied to the gas vent valve during vacuum suction during injection of the injection melt in the valve closing direction. Vacuum suction as well as The valve opening holding force when the vacuum suction state is maintained by applying a force in the valve opening direction to the degassing valve after a predetermined time has elapsed from the start and before the injected melt reaches the valve bottom, The valve opening holding force is set to be smaller than that.

[Operation] According to the present invention, until the injection melt reaches the bottom portion of the degassing valve, the force in the valve opening direction is applied to the valve and the valve is held in the open state, and Is sucked by a vacuum suction device through a gas vent valve.
During the initial vacuum suction, the gas is sucked through the valve opening portion, so that the force of the vacuum suction force causes a sudden force to act on the valve in the valve closing direction. However, at this time, the valve opening holding force is set to be larger than the force in the valve closing direction that acts on the valve by the vacuum suction at the time of starting the vacuum suction through the gas vent valve during the injection, and the valve closes. There is no such thing.
However, since the vacuum suction is continued, after a predetermined time has passed from the start of the vacuum suction, the inside of the cavity and the valve bottom side of the gas discharge path are in a vacuum state, and a slight force in the valve opening direction is applied to the valve. . On the other hand, since a slight force in the valve opening direction is applied to the valve, the force in the valve opening direction acts on the valve as a whole after the cavity side is in a vacuum state, and the valve is surely open. . However, if these forces in the valve opening direction are too large, when the valve is closed by the inertial force of the melt, the valve tends not to close quickly. However, here, the valve opening holding force is set to be smaller than the initial valve opening holding force before the melt reaches the valve, so that the valve closing force may be relatively small when closing the valve. Even if the inertial force of the melt is small, the valve can be closed quickly, easily and surely. Further, the melted material does not get caught in the valve portion, and the gas can always be sufficiently discharged.

[Embodiment] FIGS. 1 to 5 are views for explaining a mold degassing method according to the present invention, and FIG. 1 is a vertical sectional view of a mold degassing apparatus, and FIG. Is also a longitudinal sectional view and a pneumatic circuit diagram of the main part, FIG. 3 is a partially cutaway front view of a mold degassing device and a mold for carrying out the same, and FIG. FIG. 5 is a vertical cross-sectional view showing the portion corresponding to FIG. 1, and FIG. 5 is a vertical cross-sectional view of the main part of the die degassing device.

In FIG. 3, a cavity 4 is formed in a dividing surface 3 which is a joint surface between the fixed mold 1 and the movable mold 2 shown in the mold clamping state, and a cavity 4 described later is provided in the cavity 4. The advancing action of 55 causes the molten metal 7 which is an injection molten material to be injected and filled from the injection sleeve 5 through the gate 6.
Reference numeral 8 denotes a product extruding device that extrudes the product obtained by solidifying the molten metal 7 from the cavity 4 of the movable mold 2 after the mold is opened. Mold 1,2
A spool hole 11 communicating with the cavity 4 through the gas vent groove 10 is opened to the outside at the upper end of the dividing surface 3 of the, and as shown in FIG. The bypass 12, which is branched and diverted, communicates with an opening to the spool hole 11 provided at the end of the gas vent groove 10.

On the bracket 13 fixed to the upper surface of the fixed mold 1, a fluid pressure cylinder 14 is fixed concentrically with the spool hole 11, and a flange 15a which is the working end of a piston rod 15 which moves forward and backward by the fluid pressure. A holder 18 for clamping the upper end of a spool 17 of a gas venting device, which is indicated by reference numeral 16, is fixed to the spool 17, and the spool 17 is held by a retainer 19 and a bolt 20.
It is fixed at 18. The spool 17 is formed in a cylindrical shape with a bottom, and a step portion 17a is formed at the lower end of the spool 17, and as the piston rod 15 moves back and forth, the entire degassing device 16 moves up and down, and the step portion 17a engages with the spool hole 11. Mating or spool hole 11
It is configured to be separated from.

As shown in FIG. 1 etc., the spool 17 of the degassing device 16
Is divided into a member 17b, a valve guide 21 and a member 17c, and a flange portion of the valve guide 21 fitted in the inner hole 17h is held between the members 17b and 17c. The members 17b and 17c and the valve guide 21 are integrated. A piston 22 is located above the valve guide 21 and is slidably fitted in the inner hole 17d of the member 17b.
A threaded portion of a valve rod 23 that is fitted in the inner hole 21a of the valve guide 21 so as to be able to move back and forth is screwed into and integrated with the valve rod 23. A valve body 24 is integrally formed at the lower end of the valve rod 23. . Meanwhile, spool
A valve seat 17e is formed at the lower open end of the valve body 24 and
And the valve seat 17e from the valve open state shown in FIG.
The molten metal 7 that rises to 0 rises by pushing the valve body 24, and is brought into a valve closed state. In the valve open state shown in the drawing, the valve body 24 engages with the opening step portion of the gas vent groove 10 to close it. The reference numeral 17f in FIG. 2 indicates the valve chamber 17 of the spool 17 that passes through the bypass 12 in the valve open state.
A vacuum suction device 70 is connected to the discharge hole 17f in the present device for discharging the gas guided to g, so that the gas in the cavity 4 can be vacuum sucked and discharged at a predetermined timing. Is configured. The vacuum suction device 70 includes a switching valve 71, a vacuum tank 72, a vacuum pump 73, and the like.

As shown in FIG. 2, a spool 17 that forms a cylinder with the piston 22 opposite to the valve body side chamber, that is, the piston 22.
In the head side chamber 25 inside the member 17b, ports 26a and 26b are opened, and the port 26b includes a switching valve 41 having a solenoid SOL-D, a switching valve 27 having a solenoid SOL-A, and a pressure reducing valve 28. It is connected to an air source 30 via a pipe 29 provided. A throttle 42 is connected to the exhaust port 41a of the switching valve 41. On the other hand, a flange portion 22a is formed at the valve body side end portion of the piston 22, and a rod side main chamber portion 31 is formed on the opposite valve body side and outer peripheral side of the flange portion 22a, and the flange portion 22a valve body side. A rod-side auxiliary chamber portion 32 is formed in the valve. As shown in FIGS. 2 and 5, when the valve is open,
The lower surface of the flange portion 22a is pressed against the O-ring 33 fitted to the upper portion of the valve guide 21, so that the inside and outside of the O-ring 33 are
That is, the flow of fluid between the rod-side main chamber portion 31 and the rod-side sub chamber portion 32 can be blocked. Here, the rod-side main chamber portion 31 and the rod-side sub-chamber portion 32 form a rod-side chamber.

Then, the port 34 opening to the rod side main chamber portion 31 is
It is connected to the air source 30 through a pipe 37 having a switching valve 35 having a solenoid SOL-B and a pressure reducing valve 36, and
A port 38, which communicates with the rod side sub chamber 32 inside the O-ring 33, is connected to the air source 30 via a pipe 40 equipped with a switching valve 39 having a solenoid SOL-C and the pressure reducing valve 36. .

With this configuration, the following control can be performed.

(1) Opening operation of valve In Fig. 2, the solenoid SOL-A is excited (energized).
Then, when the solenoids SOL-B, SOL-C and SOL-D are demagnetized (non-energized state) as shown in Fig. 2, the fluid flows into the port.
26b and 26a flow into the head side chamber 25 to push down the piston 22, and the lower surface of the piston 22 is pressed against the O ring 33,
The space between the valve seat 17e and the valve body 24 is opened.

(2) First-stage open hold of valve When the opening operation of the valve is completed, first, the solenoid SOL-B is energized, then the solenoid SOL-A is de-energized and the solenoid SOL-D is energized. In this state, the fluid flows from the port 34 into the rod side main chamber portion 31,
It leaks into the head side chamber 25 through an extremely narrow gap which is a sliding surface portion between the piston 22 and the inner hole 17d of the member 17b. At this time, if the throttle valve 42 is throttled, back pressure acts on the head side end surface of the piston 22. At this time, fluid did not flow from the rod-side main chamber portion 31 into the rod-side sub-chamber portion 32 inside the O-ring 33, which was in contact with the lower surface of the piston 22, and was before the valve closing operation. Compressed fluid flows through the valve rod 23 and the inner hole 21 of the valve guide 21.
No pressure is generated because it leaks through a very narrow gap that is a sliding surface between a and. The fluid pressure in the rod side main chamber 31 at this time is P _R , the fluid pressure in the head side chamber 25 is P _H, and the outer diameter of the valve rod 23 is d ₁ and the outer diameter of the piston 22 in the inner hole 17d. D ₂ is the diameter of the lower surface of the piston 22 and the sealing portion of the O-ring 33, that is, the ring center diameter that is the effective sealing diameter of the O-ring 33 is d ₃ , and the piston 22 is inside the rod-side main chamber 31 when the valve is open. The area where the fluid pressure effectively acts on the flange portion 22a of
₁ , the area where the force in the valve closing direction effectively acts on the piston 22 when the fluid pressure is acting on the rod side main chamber portion 31 and the rod side sub chamber portion 32 is S ₂ , the area on the head side of the piston 22 Is S ₃ , The valve opening retention force is given by P _R · S ₁ + P _H · S ₃ , which corresponds to F ₁ in Fig. 7.

(3) Holding the valve in the second stage After the valve is held in the first stage, when the solenoid SOL-D is de-energized, the rod-side main chamber 31 moves from the piston 22 to the member 17b.
Since the fluid leaking to the head side chamber 25 through the gap with the inner hole 17d is discharged through the switching valves 41 and 27 with almost no pipe resistance, back pressure is hardly generated in the head side chamber 25. The valve opening retention force at this time is given by P _R · S ₁ , which corresponds to Fa in FIG. 7.

(4) Valve closing operation by external command Energize solenoids SOL-B and SOL-C
When SOL-A and SOL-D are de-energized, the fluid flows into the rod-side main chamber portion 31 through the port 34 and
The fluid flows into the rod side sub chamber 32 through the port 38, and the fluid pressure P _R acts on the entire upper surface of the flange 22a of the piston 22 and the entire lower surface of the piston 22. As a result, the piston 22 has
The force given by P _R・ S ₂ acts in the valve closing direction, and the piston 22
Is pushed upwards and the valve closes. Of course, the valve element 24 is the valve seat
When the valve comes into contact with 17e, the valve holds the valve closed state by the force given by P _R · S ₂ .

(5) Valve closing operation due to the inertial force of the molten metal In the first stage open holding state or the second stage open holding state of the valve, the molten metal collides with the lower surface of the valve body 24 at the time of injection, and the valve opening holding force of more than the valve opening holding force is exceeded. When the inertial force of the molten metal acts, the valve moves in the valve closing direction. In this case, if the piston 22 at the rear end portion of the valve rod 23 rises even slightly, the lower surface of the piston 22 separates from the O-ring 33, and the fluid acting in the rod-side main chamber portion 31 causes the lower surface of the piston 22 to move. It also acts on the whole, and the force given by P _R S ₂ is applied, the piston 22 rises rapidly,
The valve seat 17e portion is quickly and easily closed by the valve body 24, and the valve is held in the valve closed state.

FIG. 6 is a schematic configuration diagram of a switching valve control device, a mold, and a mold degassing device shown for explaining a mold degassing method according to the present invention. The configuration of the removing device is as described in FIG. An injection sleeve 5 having a pouring port 5a is attached to the fixed mold 1 through a fixed platen (not shown).
Is supplied from the pouring port 5a into the injection sleeve 5. Reference numeral 51 denotes an injection cylinder provided concentrically with the injection sleeve 5, and a plunger tip 55, which is the head of a plunger 54 connected to a piston rod 52 that moves forward and backward by its hydraulic pressure, via a coupling 53, It is slidably fitted in the inner hole of the injection sleeve 5. Further, 56 is the switching valve 27, 35, 39, 41
Solenoid SOL-A, SOL-B, SOL-C, SOL-D and power supply
57 is an electric command device consisting of a plurality of limit switches electrically connected to 57 and a timer.
Injection cylinder 51 fixed to bracket 53 via bracket 53a
Of the solenoid SOL-A, SOL-B, SOL-C, SOL-D at the above-mentioned predetermined timing by facing the striker 58 at a predetermined position.
Are configured to be excited and de-energized. And
In the present apparatus, after the vacuum suction device 70 starts to operate, the timer of the command device 56 measures a predetermined time, and before the molten metal 7 reaches the valve body 24, the solenoid SO
As L-A opens, the head side chamber 25 becomes atmospheric pressure, and the valve closing becomes easy as described above.

A degassing method using the die degassing apparatus that can be controlled as described above will be described using die casting as an example.

After the molds 1 and 2 are clamped, the fluid pressure cylinder 14 is actuated from the state shown in FIG. 4 to lower the entire degassing device, and as shown in FIG. Fits into the spool hole 11. Next, after the above-described valve opening operation, the valve shifts to the first stage open holding state. At this time, the valve body
As shown in FIG. 1, the lower surface of 24 closes the upper end opening of the gas vent groove 10, and the gas vent groove 10 and the valve chamber 17 of the spool 17 are closed.
The g is communicated with the bypass 12 and the valve opening.

In this state, when the molten metal 7 is poured into the injection sleeve 5 from the pouring port 5a of the injection sleeve 5, the plunger tip 55 is started to move forward, and the vacuum suction device 70 is started at a predetermined timing t _0.
Starts to operate, and the timer of the command device 56 starts counting time. Operation of vacuum suction device 70 causes cavity 4
The gas inside hits the lower end of the valve body 24 through the gas vent groove 10, passes through the bypass 12 and the valve chamber 17g, and is sucked into the vacuum suction device 70 from the discharge hole 17f.

A two-dot chain line A shown in FIG. 7 shows a change in force acting on the valve by vacuum suction. Immediately after the start of vacuum suction t _0, a relatively large force F ₂ in the valve closing direction acts on the valve due to the difference in the degree of pressure reduction before and after the valve body 24, and thereafter, with the passage of time, the gas vent groove 10, The difference in the degree of pressure reduction between the bypass 12 and the valve chamber 17g becomes small. And as the degree of pressure reduction increases,
The force acting on the valve changes in the valve opening direction and shifts to Fb. As described above, the force F _{2 in the} closing direction acts on the valve immediately after the vacuum suction starts, but at this time, the valve is in the first stage open holding state and the valve open holding force F ₁ acts on the valve. There is. Where F ₁ + F ₂
Since> 0, vacuum suction does not close the valve. The force in the valve opening direction immediately after the start of vacuum suction is
F ₂ is represented as a negative.

At the start of vacuum suction t ₀ , a timer starts counting, for example, 0
In t ₁ when the lapse of a predetermined time measured out after a few tenths to a few seconds, and the t ₁ when the prior time t ₂ when the molten metal 7 reaches the bottom of the valve body 24, the valve second stage opening Move to the holding state. At this time, the valve opening retention force decreases from F ₁ to Fa, as indicated by the dotted line B in FIG. 7. In order to close the valve by the molten metal that has collided with the bottom of the valve body 24 in this state, as shown by the solid line C as the combined force of the above-mentioned diagrams A and B, as shown in the latter half of the diagram, Fc = Fa + Fb It would be good if you had a small amount of power. Assuming that the valve opening holding force F ₁ was kept constant until the end, the molten metal that collided with the bottom of the valve body 24 had a considerably large force of F ₃ = F ₁ + Fb or more to close the valve. There must be. Here, since Fc can be made considerably smaller than F ₃ , the valve can be surely closed even if a considerably small molten metal collision force acts on the valve body 24.

In FIG. 7, a chain double-dashed line A is a force acting on the valve by vacuum suction, and a dotted line B is a force in the valve opening direction to be applied to the valve when the present invention is carried out, that is, a valve opening holding force, The solid line C is the combined force of the two forces in diagrams A and B, that is, the force that actually acts on the valve in the practice of the present invention, and the upper dashed line D is the force F ₁ that acts on the valve to the end. It is a diagram which shows the force which acts on a valve when it puts it down.

In the degassing apparatus of the above-described embodiment, after the vacuum in the cavity 4 is applied, the solenoid SOL-C is energized by an external signal before the molten metal 7 collides with the bottom of the valve body 24. If so, the valve can be closed by fluid pressure without closing the valve by the collision force of the molten metal.

Further, in the above-described embodiment, the example in which the switching valve 41 is provided in the pipe 29 has been shown, but this can be implemented by using the switching valve 41 and the throttle valve 42. In that case, when the valve is held open for the first stage, SOL-A of the switching valve 27 and SOL-B of the switching valve 35 are energized so that the pressurized fluid acts on the head side chamber 25 and the rod side main chamber portion 31. Then, a force F is applied to the valve so that the SOL-B of the switching valve 27 and the SOL-C of the switching valve 39 are energized when the second stage of the valve is held open. De-energize,
Forced fluid acts only on the rod-side main chamber 31 to apply force Fa to the valve.
It is also possible to apply the force of.

In the above embodiment, the piston 22 at the valve rear end portion is shown as a flange type piston, but it is an ordinary cylindrical piston and acts on the rear chamber on the head end side of the piston. The initial valve-opening retention force at the start of vacuum suction and the valve-opening retention force before reaching the valve of the melt after a predetermined time has elapsed from the start of vacuum suction by only the force of
Large and small control should be performed.

[Effects of the Invention] As is clear from the above description, according to the present invention, as a mold degassing method, at the time of injecting the melt into the mold cavity, the end of the gas discharge path communicating with the cavity is After holding the provided degassing valve in the open state, the gas in the cavity was discharged by the vacuum suction device through the degassing valve, and then the collision force of the injection melt to the valve bottom or the valve closing direction When the valve is once moved in the valve closing direction by the action force of, the force of the valve closing direction is applied to perform the valve closing holding operation. The initial valve opening holding force for holding the valve in the valve open state is made larger than the force in the valve closing direction that acts on the degassing valve during vacuum suction during the injection of the injection melt, and the vacuum suction is performed. After a certain time has passed from the start and the injection melt The valve-opening holding force when a vacuum suction state is maintained by applying a force in the valve opening direction to the degassing valve before reaching the bottom,
Since a method of making the valve opening holding force smaller than the initial value is adopted, when the melt reaches the valve and the valve closing operation is started, the valve opening holding force becomes small and the valve is opened even with a weak collision force. Since it can be closed and the valve can be closed surely and quickly, the melted material hardly enters the valve chamber or spouts from the valve chamber, and the durability and safety of the device are greatly improved. Also, it is very important and practically important that the valve closes quickly and surely with a considerably small force.

[Brief description of drawings]

1 to 7 are views for explaining a mold degassing method according to the present invention. FIG. 1 is a vertical cross-sectional view of the mold degassing device, and FIG. FIG. 3 is a longitudinal sectional view and a pneumatic circuit diagram. FIG. 3 is a partially cutaway front view of a die degassing device and a die for carrying out the same. FIG. 4 shows the die degassing device separated from the die. FIG. 5 is a vertical cross-sectional view corresponding to FIG. 1, and FIG. 5 is a vertical cross-sectional view of a main part of a mold degassing device.
FIG. 6 is a schematic configuration diagram of the switching valve control device, the mold and the mold degassing device, and FIG. 7 is a time-force line diagram showing a change or control state of the force acting on the valve. 1 ... Fixed mold, 2 ... Movable mold, 4 ... Cavity, 11 ... Spool hole, 16 ... Gas release device, 17 ... Spool, 17d ... Inner hole, 17e ... Valve seat, 17f ...... Discharge hole, 22 ...... Piston, 22a …… Flange part, 23 …… Valve rod, 24 …… Valve body, 25 …… Head side chamber 26a, 26b, 34,38 …… Port, 27,35,39, 41 …… Switching valve, 29,37,40 …… Piping, 30 …… Air source, 31 …… Rod side main chamber, 32 …… Rod side auxiliary chamber, 70 …… Vacuum suction device.

Claims (1)

[Claims] 1. At the time of injection of the injection melt, a degassing valve provided facing an end of a gas discharge path communicating with the cavity of the mold is held in an open state, and the inside of the cavity is maintained. In a method for degassing a mold, wherein a gas is vacuum-sucked by a vacuum suction device through the degassing valve, and then a valve closing operation is performed by a collision force of the injection melt on a valve bottom or an acting force in a valve closing direction. During the holding of the valve open state, an initial valve opening holding force for holding the gas venting valve in the valve open state acts on the gas venting valve during vacuum suction during injection of the injection melt. The force in the valve closing direction is set to be greater than the force in the valve closing direction, and after the predetermined time has elapsed from the start of the vacuum suction and before the injected melt reaches the valve bottom. Opening the valve when applying force to maintain the vacuum suction state Holding power,
A degassing method for a mold, wherein the valve opening retention force at the initial stage is made smaller.