JPS6129821B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a die-casting apparatus for casting a sound die-cast product free from shrinkage cavities caused by metal shrinkage.

Fig. 1 is a schematic cross-sectional view of the mold and injection chamber of a conventional die-casting machine, and 1 in the figure is a fixed mold;
Reference numeral 2 denotes a movable mold which is reciprocated by a mold opening/closing device (not shown). 3 is a cavity carved in the mating surface of fixed mold 1 and movable mold 2, (hereinafter referred to as cavity) 4 is an injection chamber, 5 is a runner that communicates injection chamber 4 and cavity 3, and 6 is a flow of hot water. A weir (hereinafter referred to as a gate) for giving direction and speed to the flow, 7 is an overflow. 8 is a gas vent, and is engraved with dimensions that allow gas to pass through but not molten metal. Reference numeral 9 denotes an injection sleeve, which is made to have the same core and the same inner diameter as the injection chamber 4, and has a molten metal injection port 10 in its protruding portion. Reference numeral 11 denotes an injection plunger, which is reciprocated by an injection device (not shown). The molten metal 14 is poured from the molten metal inlet 10 of the injection sleeve 9. In the general die casting method, the molten metal 14 fills the inner volume of the injection chamber 4 with 100 ml of molten metal.
Usually, 10 to 80% of the internal volume of the injection chamber 4 is on the surface of the molten metal 14 injected into the injection chamber 4.

In conventional general die-casting equipment like this, the molten metal 14 is injected into the molten metal inlet 10, and when the molten metal 14 is pressurized by the injection plunger 11 and press-fitted into the cavity 3 to perform casting, shrinkage cavities are likely to occur in the product. There were flaws.

The reason for this is that, as shown in FIG. 2, after the injection plunger 11 completes press-fitting the molten metal 14 into the cavity 3,
When the temperature of the molten metal 14 decreases, the molten metal 14 in both molds 1 and 2 begins to solidify from the outside indicated by the twill lines, and the molten metal 1
When the temperature of the molten metal 4 further decreases, the pressure inside the molten metal 14 decreases and the molten metal 14 tends to contract. At this time, unless the inside of the cavity 3 is replenished with molten metal, that is, pressurized by the injection plunger 11, the molten metal 14
A vacuum shell is formed inside, and this is the shrinkage cavity.

As described above, although the conventionally commonly used die casting method has many advantages, it also has serious drawbacks. In other words, this type of die casting method has excellent advantages such as being able to easily cast products with thin walls and complex shapes, producing beautiful product surfaces with high dimensional accuracy, and very high productivity. However, it has a serious drawback that it tends to produce many shrinkage cavities, which is a major problem in pressure resistance, strength, and heat treatability. The causes of this defect are defects in the structure of conventionally used die casting molds, the performance of casting machines, the properties of casting auxiliary materials, casting conditions, etc., but the cause of shrinkage cavities is
After the molten metal has been press-fitted into the mold, the surface of the molten metal comes into close contact with metal surfaces such as the walls of the cavity, the walls of the runner, the inside of the injection chamber, the end of the injection plunger, etc., and the thermal energy of the molten metal is rapidly absorbed. It is.

The present invention was developed in consideration of these points, and does not impair the advantages of the conventional die casting method, does not generate shrinkage cavities, and also densifies the metal structure by applying high pressure until the entire molten metal solidifies. The present invention provides a die casting device that makes it possible to cast sound products.

The details of the present invention will be explained below with reference to the drawings.

FIG. 3 is a cross-sectional view of a mold and an injection chamber showing an embodiment of the present invention. In the figure, parts having the same functions as those in FIG. Injection chamber 15
Unlike conventional die-casting machines, a large-diameter portion 16 having an inner diameter concave portion larger than the inner diameter of the injection sleeve 9 is provided in a portion of the injection chamber 15 near the mold-matching surface to prevent the heat insulating material described later from peeling off. The inner surface of the large diameter portion 16 is coated with a heat insulating material such as titanium oxide or ceramic at the thick line portion shown in the figure.

A runner 17 communicates the injection chamber 15 and the cavity 3, and the molten metal contact surface of the runner 17 is coated with a heat insulating material such as titanium oxide or ceramic. Reference numeral 20 denotes a gate that gives directionality to the flow of the molten metal, and the molten metal contact surface of this part is also coated with a heat insulating material such as titanium oxide or ceramic.

Reference numeral 21 denotes a feeder molten chamber for functioning as a feeder, which is equipped with a molded insert made of titanium oxide, ceramic, etc., or whose inner surface is coated with a heat insulating material such as titanium oxide, ceramic, etc., and is used to pressurize the feeder as described later. A riser pressure mounting 34 consisting of a plunger 22, a spring 23, and a spring receiver 24 is provided. The feeder pressurizing plunger 22 has a size that allows it to freely move in and out of the feeder molten chamber 21, and is fitted onto the mating surfaces of the molds 1 and 2. The spring 23 presses the feeder pressurizing plunger 22 in the direction of the feeder molten chamber 21 .

Therefore, the tip of the feeder pressurizing plunger 22 enters into the feeder melt chamber 21 when the feeder melt chamber 21 is empty. In addition, riser pressure plunger 2
2 is adapted to be pulled back by a cam mechanism (not shown) when both molds 1 and 2 are opened.

Next, it will be explained with reference to FIG. 4 that the present invention can effectively prevent shrinkage cavities. Figure 4 is a cross-sectional view of the vicinity of the cavity in a state where molten metal filling is completed.
In the figure, from the large diameter part 16 of the injection chamber 15, the runner 17,
The inner walls of the gate 20 and feeder molten metal chamber 21 are coated with a heat insulating material such as titanium oxide or ceramic, as explained in FIG. Therefore, it takes a long time for each of these parts to solidify after being filled with the molten metal, and the molten metal in the cavity 3 is kept in a fluid state until it is completely solidified. In addition, the feeder pressurizing plunger 22 is used to hold the molten metal 2 when filling the molten metal.
It is pushed back by the pressure of 6, compresses the spring 23, accumulates kinetic energy, and tries to move forward again.

Now, cavity 3, injection chamber 15, runner 17,
The molten metal 26 filled in each part of the gate 20 and riser molten metal chamber 21 cools and solidifies over time, but this solidification starts from the part indicated by the twill line in the figure, and as time passes, the inside surrounded by the twill line It extends to. Therefore, if the molten metal is not replenished during the solidification process inside these areas, a shrinkage cavity will be formed, but in the present invention, the injection chamber 15 is kept in the injection chamber 15 until the molten metal 26 in the cavity 3 is completely solidified. The molten metal 26 inside maintains its fluidity and is pressurized by the injection plunger 11 to be replenished into the cavity 3, and the molten metal in the feeder molten chamber 21 is pressurized by the feeder pressure plunger 22 in the part far from the gate 20. and is replenished into cavity 3. Therefore, the molten metal in the cavity 3, which will eventually become a product, completes solidification without generating shrinkage cavities, resulting in a sound casting. The molten metal in each part of the injection chamber 15, runner 17, gate 20, and riser molten metal chamber 21 is coated with a thickness of heat insulating material such as titanium oxide or ceramic so that it will solidify within a few seconds after solidification in the cavity is completed. Or it is adjusted depending on the material.

FIG. 5 shows another embodiment of the feeder molten metal chamber 21, and in FIG. . Figure 5 B is cavity 3
When the molten metal is filled into the feeder, gas is forced into the riser molten metal chamber 21, and this gas is further compressed by the molten metal 26 to form a kind of gas accumulator.
In the cooling stage, the feeder melt chamber 21 is heated by the pressure of the gas.
The cavity 3 is replenished with the molten metal 26 inside. The numeral 28 in the figure is a gasket that prevents the gas in the feeder molten chamber 21 from escaping.

FIG. 6 is a plan view showing another embodiment of the present invention,
Components in the drawings that have the same functions as those in FIGS. 3 to 5 are designated by the same reference numerals, and explanations thereof will be omitted. In the drawing, reference numeral 29 denotes a feeder molten metal chamber 30 which is pressurized by a feeder pressurizing plunger 22 and is provided with a feeder molten metal chamber which is pressurized by gas pressure when filling the molten metal. Reference numeral 31 designates air vents for discharging the gas in both molds 1 and 2 (see Figure 3) during pouring. Although it is desirable to discharge the gas, in this embodiment it is provided above the cavity 3 and in the feeder molten chamber 29.

However, in some general die-cast products, if the wall thickness near the center is greater than that at the outer periphery, shrinkage cavities are likely to form near the center of the product. In molds for products like this, shrinkage cavities can be prevented to some extent by passing a large amount of cooling water through the parts of the cavity where shrinkage cavities are likely to occur (thick parts); The cavity wall surface between the molten metal chamber and the part where shrinkage cavities are likely to form, for example, the thick part near the center of the product as shown by numeral 33 in FIG.
By coating with the above-mentioned insulating material, the solidification of the molten metal between the gate or feeder molten chamber and the thick part near the center of the product is slowed down, and the solidification of the molten metal is slowed down by the action of the gate or riser molten chamber. Since it is pressed, shrinkage cavities can be completely prevented.

As described above, according to the present invention, shrinkage cavities can be removed without impairing the advantages of conventional die-casting methods, thereby improving the quality of die-cast products.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a mold and injection part of a conventional die-casting device, FIG. 2 is a cross-sectional view of the main part of a mold in a conventional die-casting device, and FIG. 3 is a cross-sectional view of a die-casting device showing an embodiment of the present invention. Schematic diagram, FIG. 4 is a cross-sectional view of the vicinity of the cavity in a state where molten metal filling is completed in the embodiment, FIG. The figure is a plan view of essential parts of a movable mold showing another embodiment of the present invention. 1... fixed mold, 2... movable mold, 3... cavity, 4, 15... injection chamber, 5, 17... runner, 6, 20... gate, 7... overflow, 8... Gas venting, 9...Injection sleeve, 10
... Molten metal inlet, 11 ... Injection plunger, 1
2... Nozzle, 14, 26... Molten metal, 16... Large diameter part, 21, 29, 30... Risser molten metal chamber, 22
...Riser pressure plunger, 23...Spring, 24
...Spring receiver, 27...Pneumatic cylinder, 28...
Patsukin, 31...Air vent, 32...Obi,
34...Riser pressure device.

Claims (1)

[Scope of Claims] 1. A cavity consisting of both fixed and movable molds, and a recess with an inner diameter larger than the inner diameter of the injection sleeve on the side of the mold dividing surface of the injection chamber, the inner wall of which is coated with a heat insulating material. A runner which communicates the diameter part, the same large diameter part, and the cavity and whose molten metal contact surface is coated with a heat insulating material, and a runner provided in communication with the cavity in a part far from the injection chamber and molded with a heat insulating material. or a feeder molten chamber whose inner surface is coated with a heat insulating material and which acts as a riser on the cavity; A die-casting device consisting of a feeder pressure device that replenishes molten metal. 2. The die-casting apparatus according to claim 1, wherein the wall surface of the cavity between the gate or feeder molten metal chamber and a portion where shrinkage cavities are likely to be formed is coated with a heat insulating material in a band shape.