JPH08300134A - Injection method in die casting - Google Patents

Abstract

PURPOSE: To restrain the development of a pressure surge at the time of filling molten metal without surely detecting what the molten metal fills up into a cavity by reducing inertia force worked to the molten metal at the time of injecting the molten metal at high velocity. CONSTITUTION: In an injecting method for die casting, at the time of injecting the molten metal into the cavity 30, a plunger tip 44 and a plunger rod 52 in the injecting device 40 are integrally worked on the way of injecting the molten metal, and only the plunger tip 44 is worked at the high velocity since the way of the injecting and the molten metal is filled up into the cavity 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for injecting a molten metal into a cavity in die casting.

[0002]

2. Description of the Related Art Generally, in die casting, when a molten metal injected by an injection device is filled in a cavity of a mold, the pressure of the molten metal rises and a pressure surge occurs. Due to this pressure surge, the high temperature molten metal that has just been filled in the cavity is ejected from the mating surface of the mold, causing burrs. Therefore, in the technique related to die casting, for example, disclosed in Japanese Patent Application Laid-Open No. 4-13465, the detection means detects that the filling of the cavity with the molten metal is completed, and based on this detection, an operation for injection in the injection device. The oil pressure is shut off to suppress the pressure rise of the molten metal, and the pressure surge described above is also being eliminated.

[0003]

However, the plunger tip and the plunger rod that press the molten metal into the cavity in the injection device have a large mass, and they do not stop immediately even if the working hydraulic pressure to the injection device is cut off, and inertia Continue to move by force. As a result, even after the filling of the molten metal into the cavity is completed, the molten metal is pushed by a large inertial force, the pressure rises, and the above-mentioned pressure surge occurs. Further, the detecting means in the above publication detects the amount of movement of the plunger rod of the injection device when the filling of the molten metal is completed, but the amount of injection of the molten metal by the injection device and the amount of movement of the plunger rod do not necessarily correspond to each other. It cannot be said that they have a 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. Therefore, there is a variation in the injection amount of the molten metal when the plunger rod moves to the position to be detected by the magnetic sensor, and it is not uniquely determined whether the molten metal is sufficiently filled in the cavity. Therefore, it is difficult to accurately detect the timing at which the operating hydraulic pressure of the injection device is cut off.

The problem to be solved by the present invention is to perform high-speed injection only with a plunger tip having a small mass from the middle of injection, and to reduce the inertial force acting on the molten metal at the time of high-speed injection, so that the molten metal enters the cavity. The purpose of this is to suppress the occurrence of pressure surge at the time of filling and prevent the occurrence of burrs without accurately detecting the filling.

[0005]

The injection method of die casting according to the present invention is as follows. According to the invention of claim 1, when the molten metal is injected into the cavity,
It is characterized in that the plunger tip and the plunger rod of the injection device are integrally operated up to the middle thereof and only the plunger tip is operated at high speed during the injection to fill the cavity with the molten metal.

[0006]

According to the invention described in claim 1, since only the plunger tip of the injection device is operated at a high speed during the injection, the inertial force acting on the molten metal during the high-speed injection becomes small. Therefore, it is possible to suppress the occurrence of pressure surge during the filling without accurately grasping the timing when the filling of the molten metal into the cavity is completed. As a result, it is possible to prevent burrs from being generated by the molten metal being ejected from the mating surface of the mold due to the pressure surge. This means that it is not necessary to set the mold mating surface to be wide in order to prevent the molten metal from spouting, the mold can be made smaller and lighter, and the casting machine can also be made smaller.

[0007]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a configuration diagram showing a partial cross section of a die casting apparatus. As shown in this drawing, the substrate 1 of the casting apparatus
A fixed die plate 14 and a movable die plate 16 are arranged on the upper surface of the sheet 3 so as to face each other. While the fixed die plate 14 is immovable with respect to the substrate 13,
The movable die plate 16 is guided by the tie bar 20 and can move in a direction toward or away from the fixed die plate 14.

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 so that the molten metal in a molten metal heat insulation furnace (not shown) provided near the die casting equipment is supplied by the ladle 48. ing. And this injection device 4
No. 0 is capable of injecting the molten metal into the two molds 10 and 12 by operating the injection cylinder 50.

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 penetrating the fixed mold 10 and communicating with the runner 32, and a plunger tip 44 is provided in the sleeve 42 so as to be reciprocally movable. Further, the sleeve 42 has a sprue 4 which is supplied with the molten metal from the ladle 48 outside the fixed die plate 14.
6 is formed.

The injection device 40 is provided with a plunger rod 52 which reciprocates under the control of operating hydraulic pressure to the injection cylinder 50, and the plunger rod 52 is arranged coaxially with the sleeve 42 and the plunger tip 44. The control of operating hydraulic pressure to the injection cylinder 50 is performed by switching the hydraulic control valve 58. A second cylinder 54 is formed inside the plunger rod 52 near the tip thereof, and a plunger 56 of the second cylinder 54 is integrally formed with or integrally connected to the plunger tip 44. Further, the second cylinder 54 has a plunger 56.
By the operation of (1), it is possible to suck and fill the inside of it with a combustible substance such as hydrogen or gasoline, and to explode the combustible substance with a spark plug (not shown).

At the time of die casting, the molten metal is supplied into the sleeve 42 of the injection device 40 from its gate 46. Then, by controlling the hydraulic pressure for the injection cylinder 50, the plunger rod 52 is moved to the left at a low speed together with the plunger tip 44 through the plunger 56 of the second cylinder 54, and the molten metal in the sleeve 42 is moved to both sides. It is injected into the molds 10 and 12 at a low speed.

The molten metal injected by the injection device 40 fills the runner 32 of the molds 10 and 12 and then passes through the dam portion 34 to fill the cavity 30. The fact that the water reaches the dam portion 34 is detected by some detection means. As one of the means, the pressure of the molten metal when it reaches the dam portion 34 rises sharply and acts as a reaction force against the plunger rod 52 of the injection cylinder 50, so that the operating hydraulic pressure of the injection cylinder 50 is changed. There is a means for detecting with a predetermined pressure detector (not shown).

Based on the detection signal from the detector, the flammable substance filling the inside of the second cylinder 54 is exploded. As a result, the plunger tip 44 (including the plunger 56) moves to the left at a high speed, and from this point, the molten metal is injected at a high speed and press-fitted inside the cavity 30. When the filling of the molten metal into the cavity 30 is completed, the plunger rod 52 of the injection cylinder 50 is moved leftward with respect to the plunger 56 of the second cylinder 54 to remove the combustible substance after combustion from the second cylinder 54. Exhaust from inside.

As described above, when the molten metal is injected at a high speed by the injection device 40, by operating only the plunger tip 44 (including the plunger 56) having a small mass, the inertial force acting on the molten metal at the time of the high speed injection becomes small. Therefore, the occurrence of a pressure surge when the cavity 30 is sufficiently filled with the molten metal is suppressed, and the inconvenience that the molten metal spouts from the mating surfaces of the molds 10 and 12 due to the pressure surge is prevented. . In this embodiment, the timing at which the molten metal is switched from the low-speed injection to the high-speed injection, that is, when the molten metal reaches the dam portion 34 is accurately detected, the time when the filling of the molten metal into the cavity 30 is completed is accurately determined. There is no need to detect.

[0016]

Industrial Applicability According to the present invention, by suppressing the occurrence of a pressure surge at the completion of filling the molten metal into the cavity, it is possible to prevent the molten metal from spouting from the mating surface of the mold and causing burrs in the cast product. The deburring process for the mold becomes unnecessary, and the mold mating surface can be narrowed to reduce the size and weight of the mold.

[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.

[Explanation of symbols]

 30 Cavity 40 Injection Device 44 Plunger Tip 52 Plunger Rod

Claims (1)

[Claims] 1. When the molten metal is being injected into the cavity, the plunger tip and the plunger rod of the injection device are integrally operated up to the middle thereof, and only the plunger tip is operated at high speed from the middle of the injection. An injection method for die casting, characterized in that the cavity is filled with molten metal.