JP3329651B2 - Liquid phase injection molding of metal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid phase injection molding method of metal in which a metal is melted by an in-line screw type injection molding machine to form a liquid phase, and the molten phase is injected into a mold and molded.

[0002]

2. Description of the Related Art Conventionally, a method of forming a metal includes a cold chamber method in which a metal is melted in a melting furnace, a molten metal is drawn with a ladle, poured into a chamber, and cast. There is a die casting method typified by the installed hot chamber method. However, since the conventional die casting method uses a melting furnace, it requires a large amount of melting energy to melt the metal,
There is a problem that the working environment is poor because high heat and dust are generated. Therefore, in recent years, a metal injection molding method using an injection molding machine has attracted attention.

[0003] In this metal injection molding method, the metal is kneaded and melted by a screw having a non-return prevention mechanism at a tip end thereof.
This is a method in which the screw is retracted while the molten metal is supplied to the front of the screw, and the screw is advanced to be injected into a mold and molded. In this injection molding method, since the molten metal has a very low viscosity, when kneading and melting the metal with a screw, it is necessary to close the opening of the nozzle to prevent the molten metal from flowing out. Therefore, conventionally, as shown in FIG. 7, a method of positively forming the solid plug D in the opening hole of the nozzle 3 has been adopted. In order to form the solid plug D, the temperature of the nozzle 3 is set to be lower. Therefore, the solid plug (solid) D and the molten metal (liquid)
A semi-solidified structure F in which a solid and a liquid coexist is formed between E and E. In addition, in the injection molding method by the thixomolding method, the above-mentioned molten metal (liquid) E region also has a semi-solid structure F.

[0004]

In a conventional metal injection molding method, a fixing plug formed at the tip of a nozzle includes:
There were the following problems. (A) In many cases, the injection pressure changes due to the variation in the size of the fixed plug to be formed, or the fixed plug interferes with the flow of the molten metal, so that it is often difficult for the molten metal to quickly enter the mold cavity. appear. (B) In order to prevent the fixed plug from entering the mold cavity, a fixed plug catcher is provided in the mold. However, the fixed plug does not stably enter the catcher, and pops out of the mold cavity. Invasion often occurs. (C) Since a semi-solidified structure in which a solid and a liquid having extremely poor fluidity coexist exists, a large flow resistance is generated in a narrow portion of a flow path or a gate portion when injection molding is performed in a mold.

[0005] Due to the above (a) to (c), stable molding cannot be performed, and continuous operation of the injection molding machine has been difficult.

The present invention has been made in view of the above problems, and provides a metal liquid injection molding method capable of realizing a stable molding operation in a metal injection molding method. That is the task.

[0007]

According to the present invention, a nozzle mounted on a cylinder head of an injection molding machine is rotated by a rotating nozzle.
Has a needle valve that moves back and forth along the outer peripheral shape of the shaft
The above-mentioned problem has been solved by using a core valve type self-sealing nozzle to heat the nozzle to keep the metal in the nozzle in a liquid phase. With this configuration, the metal that has been melted and kneaded with a screw to form a liquid phase can be injected into the metal cavity without forming a solid plug at the tip of the nozzle, thereby performing a stable molding operation. It becomes possible.

[0008]

Embodiments of the present invention will be described.

According to the method of the present invention, in which a metal is melted by an in-line screw type injection molding machine and injection-molded as a liquid phase (liquid-phase metal injection molding method), a nozzle mounted on a cylinder head is a self-sealing nozzle, The nozzle is heated to maintain the metal in the nozzle in a liquid phase. The injection molding method is suitable for injection molding of a metal having a melting point of 700 ° C. or less. Further, the nozzle is preferably a self-sealing nozzle of a core valve type or a rotary type.

[0010]

Embodiments of the present invention will be described with reference to the drawings.

FIGS. 1 to 4 show a core valve type self-sealing nozzle mounted on a cylinder head of an injection molding machine. FIG. 1 is a longitudinal sectional view, and FIGS. 2 and 3 are A-
FIG. 4 is a sectional view taken along line A of FIG. 1.

As shown in FIG. 1, a cylinder head 2 is attached to a tip of a cylinder 1 of an injection molding machine by a bolt 17. A nozzle 3 having an opening 3a is screwed into the tip of the cylinder head 2.
Inside the cylinder head 2, there are provided a plurality of flow paths 14 for communicating between the inside of the cylinder 1 in which the screw 15 is inserted and the inside of the nozzle 3. Further, a hole 5a is formed in the tip end side of the cylinder head 2 in the vertical direction in the figure,
The rotating shaft 5 is fitted into the hole 5a. A hole 4a is formed in the center of the tip of the cylinder head 2 so as to communicate vertically with the hole 5a. The needle valve 4 is fitted in the hole 4a so as to be able to move back and forth. The front end of the needle valve 4 can be inserted into the opening 3 a of the nozzle 3, and the rear end is in contact with the rotating shaft 5. A heater 16 is attached to the outer periphery of the nozzle 3, the cylinder head 2, and the cylinder 1, and the temperature is controlled by a temperature detector 18.

The rotary shaft 5 is connected to an actuator 9 via an arm 6, a shaft 7, and a yoke 8, as shown in FIG. The hinge 12 of the actuator 9 is pivotally connected to a bracket 10 via a shaft 11, and the bracket 10 is fixed to a plate 13 attached to a flange of the cylinder head 2.

Next, the operation of the above-described self-sealing nozzle will be described.

In the metal melting / kneading step, the actuator 9 is operated by switching an electromagnetic valve, and the movement of the piston rod of the accumulator 9 is changed into a rotational movement using the yoke 8, the shaft 7 and the arm 6, and the arm 6 is moved. The rotation shaft connected to the shaft is moved from the state shown in FIG. 2 to the state shown in FIG.
Rotate °. Then, the needle valve 4 in contact with the rotating shaft 5 advances, the tip of which is inserted into the opening 3 a of the nozzle 3, and the opening 3 a is closed to prevent the molten metal from flowing out of the nozzle 3. You.

In the metal injection step, the rotating shaft 5 is rotated to the state shown in FIG. Then, a retreating force acts on the needle valve 4 due to the injection pressure received by the molten metal, and as shown in FIG. 2, the opening 3a of the nozzle 3 is released, and the molten metal is injected into the mold.

In any of the above-described steps, the temperature of the nozzle 3 is set to a temperature equal to or higher than the melting point of the molten metal, so that the molten metal does not solidify in the nozzle 3.

In the above-described embodiment, a self-sealing nozzle of a core valve type (needle valve type) is used as the nozzle 3, but a rotary self-sealing nozzle of a rotary type shown in FIG. 5 may be used. it can. That is, in the present embodiment, FIG.
5A, a flow path is provided in the rotating shaft 5 as shown in FIG. 5A. When the rotating shaft 5 rotates, the nozzle is opened as shown in FIG. 5B and the nozzle is closed as shown in FIG. can do.

According to the above-described embodiment, the metal is
The mixture can be melted and kneaded at 5 and injected into the mold cavity without forming a fixing plug D at the nozzle tip.

A typical metal used for injection molding is a magnesium-aluminum alloy as shown in FIG. Usually, a so-called thixomolding method in which a magnesium alloy containing 9% by weight of aluminum is injection-molded in a molding region of a semi-solid structure is used. Suitable for injection molding in the phase molding area. The melting point is 7
When the temperature exceeds 00 ° C., the strength of the needle valve becomes a problem.

[0021]

According to the present invention, there is provided a method for injection molding a metal in a liquid phase.
With the above configuration, the following effects can be obtained. That is, since injection molding can be performed without forming a solid plug at the tip of the nozzle, the solid phase does not enter the mold, the flow is smooth, and the molded product is defective, hot water is poor, and the run is poor. Defect phenomena such as cold are remarkably reduced, the quality of molded products is improved, fluidity is stabilized, the stability of molding conditions is improved, the defective rate is reduced, and productivity is improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a core valve type self-sealing nozzle used in a liquid phase injection molding method according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line AA of FIG. 1, showing a state in which an opening hole of a nozzle is released .

FIG. 3 is a sectional view taken along line AA of FIG. 1, showing a closed state of an opening hole of a nozzle.

FIG. 4 is a view taken in the direction of the arrow C in FIG. 1;

FIG. 5 is a view showing a rotary type self-sealing nozzle used in a liquid phase injection molding method according to another embodiment of the present invention, wherein FIG. 5 (a) is a longitudinal sectional view, and FIG. B- in FIG.
FIG. 3 is a cross-sectional view taken along a line B, showing a released state, and FIG. 4C is a cross-sectional view taken along a line BB in FIG.

FIG. 6 shows M which is a typical metal material used in the present invention.
FIG. 3 is an equilibrium diagram of a g-Al-based alloy.

FIG. 7 is a view showing a molten state of a metal material at a nozzle tip.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 2 Cylinder head 3 Nozzle 3a Opening hole 4 Needle valve 4a, 5a hole 5 Rotating shaft 6 Arm 9 Actuator 14 Flow path 15 Screw 16 Heater 17 Bolt 18 Temperature detector

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B22D 17/20 B22D 17/02 B29C 45/20

Claims (2)

(57) [Claims] In a method of melting a metal by an in-line screw type injection molding machine and injecting it into a liquid phase, a nozzle (3) mounted on a cylinder head (2) is rotated.
Moving back and forth along the outer peripheral shape of the rotating shaft (5).
A liquid-phase injection molding method for a metal, comprising a core valve type self-sealing nozzle having a needle valve (4) , and heating the nozzle (3) to keep the metal in the nozzle in a liquid phase. 2. The method according to claim 1, wherein the melting point of the metal is 700 ° C. or less.