JPH05253658A - Casting apparatus and casting method for die casting - Google Patents

Abstract

PURPOSE:To prevent trouble such as the development of shrinkage cavity or the breakage of a metallic mold by providing a pressurizing control means for controlling local pressurizing force with a local pressurizing plunger in multi-steps. CONSTITUTION:Working oil 5 is pumped up from a working oil tank 34 by a hydraulic pump 33 and fed into a pressure reducing valve 12 through a digital type relief valve. Then, corresponding to the quantity detected by a means 110 for detecting the pressure in a cavity, the opening quantity of the hole of the pressure reducing valve 12 is controlled and decided. The working oil 5 is press-fed into a piston 21 through a hydraulic pipe 41 and further, the local pressurizing plunger 2 is pushed out toward the cavity 80 side to gradually apply local pressurizing force to the molten metal 6 in the cavity 80. Therefore, while accurately detecting the pressure in the cavity 80 successively, the local pressurizing force can be applied in multi-steps. By this method, the development of segregation on shrinkage cavity of the molten metal 6 can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die for die casting and a die casting method capable of preventing problems such as occurrence of shrinkage cavities and damage to the die.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, an injection plunger 7 has been used for the purpose of obtaining a high-density die-cast product with few cavities.
In addition to the above, a casting apparatus for die casting, which is provided with a local pressure plunger 9, is known. As shown in the figure, the casting apparatus injects a cavity 80 formed in a mold 8 composed of a fixed die 81 and a movable die 82, and a molten metal 6 forming a molding target in the cavity 80. 2 and a pressurizing cylinder 91 provided with a local pressurizing plunger 9 for locally pressurizing the molten metal 6 in the cavity 80.

In die casting using the above casting apparatus, the molten metal 6 is injected into the cavity 80 through the sprue 801 by the injection plunger 7. The molten metal 6 is supplied into the injection cylinder 71 from a hot water supply port 710 provided in the injection cylinder 71.

On the other hand, the molten metal 6 in the cavity 80 is locally pressurized by the locally pressurized plunger 9. As a result, a high density die cast product with few shrinkage cavities can be obtained. The local pressurizing plunger 9 is operated by the hydraulic oil 5 being fed into the pressurizing cylinder 91 by the hydraulic pressure switching valve 95 and the hydraulic pipe 951.

By the way, when the molten metal 6 in the cavity 80 is locally pressurized by the local pressure plunger 9, the timing of the pressure and the local pressure plunger 9 are applied.
The amount of displacement greatly affects the density of die cast products. As a result, the amount of shrinkage cavities will be different.

The fixed die 81 is a fixed die support base 8
It is held and fixed by a fixed block 812 supported by 11. On the other hand, the movable mold 82 has the movable mold support 9
The movable block 821 supported by 6, 97, 98 is configured to move by the driving force of a piston (not shown). Reference numeral 70 in FIG. 4 is an injection rod, 71
Reference numeral 1 is a runner, 901 is a sprue, 92 and 93 are ejector pins, and 952 is a hydraulic pipe for returning the hydraulic oil 5.

[0007]

However, the above-mentioned conventional technique has the following problems. That is, the local pressurizing plunger 9, when injecting the molten metal 6 by the injection plunger 7, as shown in FIG. 5, two to three times the casting pressure, for example, 2,000 kgf / cm ² or more to a high pressure is applied to cover also become. That is, as shown in FIG. 5, the local pressure P of the local pressure plunger and the casting pressure Q of the injection plunger 7 will be described first.

The casting pressure Q is a pressure in the cavity 80 when the molten metal 6 is injected into the cavity 80 by the injection plunger 7. As shown in FIG. 5, the casting pressure Q is about 120 which is almost constant from the start of injection to the completion thereof.
It is 0 kgf / cm ² . The local pressure P is the pressure in the cavity 80 when the molten metal 6 in the cavity 80 is locally pressurized by the local pressure plunger 9. Since the local pressure is relatively high, the molten metal 6 in the initially solidified (melted) state inside the cavity 80 is pushed out from the gate 801 into the runner 711.

As a result, sufficient local pressing force is not applied to the molten metal 6 in the cavity 80, and shrinkage cavities are formed in the die-cast molding object. In addition, the injection plunger 7
When the time lag T ₀ (see FIG. 5) from the injection of the molten metal 6 into the cavity 80 due to the time until the local pressurization of the local pressure plunger 9 (see FIG. 5) becomes longer, the molten metal 6 inside the cavity 80 solidifies. Will progress to a considerable extent. Therefore, in order to prevent the occurrence of shrinkage cavities, the local pressure P is set to about 2200 kgf / cm ^{2 as} shown in FIG.
The above may be added.

As a result, the molten metal 6 in the cavity 80 is
With the rapid increase of the pressure, it moves in the cavity 80 and segregates. Therefore, a problem (trouble) occurs that many shrinkage cavities (contraction cavities) are generated due to the occurrence of this segregation.

Further, in order to prevent the occurrence of the shrinkage cavity, the pressure P of the local pressure plunger 9 is set to 2200 kg.
If it is set to f / cm ² or more, the fixed mold 81, the movable mold 82, or the like may be damaged, which may cause a trouble. The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a casting device for die casting and a die casting method capable of preventing problems such as occurrence of shrinkage cavities and damage to the die 8. To do.

[0012]

According to the present invention, there is provided a cavity formed in a mold, an injection plunger for injecting a melt of an object to be molded into the cavity, and locally pressurizing the melt in the cavity. And a pressure control means for controlling the pressing force of the local pressure plunger in multiple stages.

What is most noticeable in the present invention is the provision of pressurizing control means for controlling the pressing force of the local pressurizing plunger in multiple stages. As the pressurizing control means, for example, as shown in the first embodiment, a digital relief valve connected to the pressure reducing valve is used. Further, the pressure in the cavity is detected by the controller, and the pressure detection means in the cavity is used to increase the local pressure in multiple stages according to the detected amount. That is, the pressurizing control means is configured to increase the local pressing force in multiple stages according to the solidified state of the molten metal.

Therefore, for example, the pressurizing control means uses a digital relief valve which operates in accordance with the molten metal pressure in the cavity and has a cavity pressure detecting means capable of detecting the degree of solidification of the molten metal. The optimum conditions for increasing the pressure in multiple stages are, for example, the elapsed times T _{1 to} T ₄ (FIG. 2) and the pressures P _{1 to} P ₄ (FIG. 3) after applying local pressure in four stages. Is determined by experiment.

Next, as a die-cast casting method, the molten metal of the object to be molded is injected into the cavity in the mold, and then the molten metal is solidified while locally applying pressure to the molten metal in the cavity with a local pressure plunger. In doing so, there is a die cast casting method characterized in that the local pressurization by the local pressurizing plunger is controlled in multiple stages according to the degree of solidification of the molten metal.

What is most noticeable in the die-cast casting method is that the local pressure applied by the local pressure plunger is controlled in multiple stages according to the degree of solidification of the molten metal. That is, the local pressure applied by the local pressure plunger is gradually increased according to the solidification rate of the molten metal. The degree of progress of solidification can be known by detecting the amount of operation of the local pressure plunger or the extent of molten metal, for example, by the correlation between the detected value and the progress of solidification.

In controlling the local pressing force in multiple stages, for example, the temperature and pressure of the molten metal in the cavity are detected. Then, the local pressing force in the cavity is increased by the pressurizing control means in accordance with the detected amount.

[0018]

In the casting apparatus for die casting of the present invention, there is provided a pressurizing control means for controlling the local pressurizing force by the local pressurizing plunger in multiple stages. for that reason,
From the time when the molten metal is completely filled into the cavity to the time when the solidification is completed, an appropriate local pressing force can be constantly applied to the molten metal.

As a result, for the molten metal in the cavity,
It is possible to control the movement of the molten metal during solidification to a minimum without applying it while the local pressure is suddenly increased. Therefore, it is possible to prevent the segregation of the molten metal and the occurrence of shrinkage cavities. Further, in preventing the occurrence of shrinkage cavities, it is possible to always apply only an appropriate local pressing force to the mold without applying a large local pressing force to the molten metal in the cavity.

Therefore, it is possible to prevent the dies such as the fixed die and the movable die from being damaged. Also, the same effect can be obtained in the die-cast casting method. Therefore,
According to the present invention, it is possible to provide a die for die casting and a casting method capable of preventing problems such as occurrence of shrinkage cavities and damage to the die.

[0021]

【Example】

Example 1 A casting apparatus for die casting according to an example of the present invention will be described with reference to FIG. The casting apparatus of this example has a mold 8
A cavity 80 formed inside, and an injection plunger 7 for injecting the melt 6 of the molding target into the cavity 80.
A local pressurizing plunger 2 for locally pressurizing the molten metal 6 in the cavity 80, and a pressurizing control means 1 for controlling the pressing force of the local pressurizing plunger 2 in four stages.
Have and.

As shown in FIG. 1, the pressurization control means 1 has an intracavity pressure detection means 110 capable of successively and accurately detecting the pressure of the molten metal 6 in the cavity 80. Also,
The pressurization control means 1 has a controller 10 electrically connected to the temperature and pressure sensors in the cavity 80. As a result, depending on the temperature and pressure in the cavity,
The digital relief valve 11 is activated.

Further, the pressurization control means 1 has a digital relief valve 11 connected to the pressure reducing valve 12 and the oil control valve 13. The digital relief valve 11 is connected to a hydraulic pump 33 and a hydraulic oil tank 34 for feeding the hydraulic oil 5. Others are the same as in the conventional example. In addition, reference numerals 22 and 23 in FIG.
Shows ejector pin.

Next, the function and effect will be described. In locally applying pressure to the molten metal 6 in the cavity 80 using the casting apparatus for die casting of this example, first, the hydraulic oil 5 is pumped up from the hydraulic oil tank 34 by the hydraulic pump 33 and the digital relief valve 11 It is fed into the pressure reducing valve 12 via. At this time, the in-cavity pressure detecting means 11
The opening amount of the pressure reducing valve 12 is controlled and determined according to the detected amount of zero.

Therefore, as shown by the solid line arrow, the hydraulic oil 5 has an appropriate amount from the hydraulic tank 34 such as the digital relief valve 11, the pressure reducing valve 12, and the oil control valve 1.
3, It is pumped into the piston 21 through the hydraulic pipe 41. As a result, the piston 21 moves in the direction of the solid arrow, and the local pressure plunger 2 is further pushed out to the cavity 80 side. Then, the molten metal 6 in the cavity 80
Therefore, the local pressure P is gradually applied. Therefore, while the pressure in the cavity 80 is sequentially and accurately detected by the in-cavity pressure detecting means 110,
The local pressure P can be applied to the cavity 80 in multiple stages.

Therefore, the digital relief valve 11 described above is used.
For example, the local pressing force P is controlled in four steps as in Example 2 described later. Therefore, from the completion of the filling of the molten metal 6 in the cavity 80 to the completion of the solidification, the appropriate local pressing force P is always gradually increased in multiple stages.
Can be added to. As a result, the local pressure P is not suddenly applied to the molten metal 6 in the cavity 80, and the movement of the molten metal 6 during solidification can be controlled to the minimum.

Therefore, it is possible to prevent segregation of the molten metal 6 and generation of shrinkage cavities. Further, in preventing the occurrence of shrinkage cavities, a large local pressing force P is not applied to the molten metal 6 in the cavity 80. Therefore, the fixed die 81 and the movable die 82
It is possible to prevent the mold from being damaged. Therefore, according to this example, it is possible to prevent problems such as the occurrence of shrinkage cavities and damage to the mold.

Example 2 As shown in FIGS. 1 to 3, this example shows a method of casting a die cast product by using the die casting casting apparatus according to the example 1. As shown in FIGS. 1 to 3, the die-cast casting method of this example injects the molten metal 6 of the object to be molded into the cavity 80 in the die 8 and then applies the local pressure plunger 2 to the molten metal 6 in the cavity 80. This is a method of solidifying the molten metal 6 while applying a local pressure P according to the degree of progress of solidification.

As shown in FIGS. 2 and 3, the local pressure P applied by the local pressurizing plunger 2 is controlled in four stages according to the degree of solidification of the molten metal 6. That is, as shown in FIG. 2, the molten metal 6 in the cavity 80 is in the first solidified state of the first solidified state.
In step T ₁ , the local pressure P is about 700 kgf /
cm ² . Here, the first stage T ₁ is 1.5 seconds.

In the second stage T ₂ , the local pressure P is about 1200 kgf / cm ² . Here, the second stage T ₂ is 2.0 seconds. Next, in the third stage T ₃ , the local pressure P is about 1600 kgf / cm ² .
Here, the third stage T ₃ is 2.5 seconds. Then, in the fourth stage T ₄ , the local pressure P is about 2000 kgf /
cm ² . The casting pressure Q by the pressure plunger 2 is always about 1000 kgf / cm ² .

On the other hand, FIG. 3 shows the amount of shrinkage cavity generation V in the molten metal 6.
The relationship between cm ³ and the elapsed time T from the start of injection is shown. As shown in the figure, the shrinkage cavity generation amount V is about the value of the first stage T ₁ of the initial solidification state at the end of casting, that is, at the fourth stage T ₄ . Two
It was twice as large as 26 cm ³ . However, it is known that the number of shrinkage cavities is highest in the first stage T ₁ and then gradually decreases. From this, it is known that increasing the local pressing force in multiple stages is effective for preventing the occurrence of shrinkage cavities.

That is, the local pressing force P is, as shown in FIGS. 2 and 3, 4 times between the start of the local pressurization and the end thereof.
The maximum pressure is about 2000kgf / cm
^{It is set to 2} . On the other hand, the conventional local pressure P is
2200 kgf, which is almost twice the casting pressure Q
/ Cm ² or more is added to the inside of the cavity 8 (Fig. 5).
reference).

Therefore, the molten metal 6 in the cavity 80 is controlled so that the movement of the molten metal 6 during solidification is minimized without being applied to the molten metal 6 in a state where the local pressing force P is rapidly increased. Therefore, the segregation of the molten metal 6 and the generation of shrinkage cavities can be reliably prevented. Also, to prevent the occurrence of shrinkage cavities, 2000 kg for the molten metal 6 in the cavity 80
Since the pressing force P of f / cm ² or more is not applied to the inside of the cavity 80, it is possible to prevent damage to the molds such as the fixed mold 81 and the movable mold 82 and their associated equipment.

Further, as shown in FIGS. 2 and 3, the initial time lag T ₀ (see FIG. 4) provided in the conventional casting method is used.
(See) is not necessary. This is, in this example,
This is because the rapid solidification of the molten metal 6 in the cavity 80 is not promoted. As a result, the molten metal 6 in the cavity 80
Is not affected by a sudden increase in pressure, so that it does not move in the cavity 80 and segregation does not occur. Therefore, it is possible to minimize the occurrence of shrinkage cavities during the solidification of the molten metal 6.

[Brief description of drawings]

FIG. 1 is a sectional view of a casting device for die casting according to a first embodiment.

FIG. 2 is an elapsed time T from the start of injection in the second embodiment.
A graph showing the relationship between pressure and pressure.

FIG. 3 is a graph showing the relationship between the elapsed time T and the shrinkage cavity generation amount V in the second embodiment.

FIG. 4 is a cross-sectional view of a conventional casting device for die casting.

FIG. 5 is a graph showing the relationship between the elapsed time T from the start of injection and the pressure in the cavity in the related art.

[Explanation of symbols]

 1. ． ． Pressure control means, 10. ． ． Controller, 11. ． ． Digital relief valve, 110. ． ． Cavity pressure detection means, 12. ． ． Pressure reducing valve, 13. ． ． Oil control valve, 2. ． ． Local pressure plunger, 21. ． ． Piston, 5. ． ． Hydraulic oil, 6. ． ． Molten metal, 8. ． ． Mold, 80. ． ． cavity,

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuyoshi Yokoi 1-1-1, Showa-cho, Kariya city, Aichi prefecture Nihon Denso Co., Ltd.

Claims (2)

[Claims] 1. A cavity formed in a mold, an injection plunger for injecting a melt of an object to be molded into the cavity, and a local pressure plunger for locally pressurizing the melt in the cavity. And a pressurizing control means for controlling the pressing force of the local pressurizing plunger in multiple stages, a casting apparatus for die casting. 2. A local pressure plunger for injecting molten metal of a molding target into a cavity in a mold and then solidifying the molten metal while locally applying pressure to the molten metal in the cavity by a local pressure plunger. The die casting method is characterized in that the pressurization is controlled in multiple stages according to the progress of solidification of the molten metal.