JP2012020310A - Apparatus and method for vacuum die casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively suppress a casting defect due to the entrapment of combustion gas from a lubricant.SOLUTION: A vacuum die casting apparatus includes: a vacuum tank 13 and a vacuum pump 14 for vacuuming the inside of a die cavity 3; an injection sleeve 6 with a molten metal supply port 5 for supplying a molten metal; and a plunger tip 8 for pushing the molten metal in the injection sleeve 6 to inject it into the die cavity 3. The vacuum die casting apparatus is configured to distribute, during the period from when a lubricant is dropped into the injection sleeve 6 till when the plunger tip 8 closes the molten metal supply port 5, a compressed air from the die cavity 3 side toward the molten metal supply port 5 to clear away the combustion gas produced as a result of combusting the lubricant.

Description

  The present invention relates to a vacuum die casting apparatus and a vacuum die casting method in which casting is performed by pressing a molten metal supplied into an injection sleeve from a hot water supply port with a plunger tip and injecting the molten metal into a die cavity that has been vacuum-depressed.

  As one of mold casting methods, there is known a die casting method capable of producing a casting with high dimensional accuracy in a short time by press-fitting molten metal into a mold. In the die casting method, defects due to air entrainment and non-filling of the mold corners caused by press-fitting molten metal into the mold at high speed may occur. Therefore, a vacuum die casting method has been proposed in which molten metal is injected and filled in a state where the inside of the mold is decompressed to a vacuum state by sucking air existing in the mold cavity with a vacuum tank. In the vacuum die casting method, since the resistance is small, the fluidity of the molten metal is improved and the hot water is improved. Further, since gas (air) is sucked out, it is also effective in suppressing the occurrence of casting defects called nests caused by gas entrainment.

  Conventionally, a vacuum die casting apparatus described in Patent Document 1 has been proposed. In the apparatus described in Patent Document 1, the mold cavity is opened to the atmosphere from the start of the molten metal supply to the injection sleeve until the plunger tip closes the hot water supply port. When the plunger tip closes the hot water supply port, forced evacuation is started by vacuum depressurization of the mold cavity. The vacuum depressurization is performed until immediately before the filling of the molten metal in the mold cavity is completed, and thereafter, the mold cavity is opened to the atmosphere and exhausted.

  FIG. 5 shows a vacuum die casting apparatus for performing such degassing. The vacuum die casting apparatus includes a hot water supply port 50 at the rear end and an injection sleeve 53 having a front end connected to a mold cavity 52 formed in the mold 51. In addition, a plunger tip 54 for extruding the molten metal supplied from the hot water supply port 50 toward the mold cavity 52 is disposed inside the injection sleeve 53 so as to advance and retreat.

  On the other hand, a gas vent 55 is connected to the mold cavity 52. An air system circuit and a vacuum exhaust system circuit are connected to the degassing section 55. In the circuit of the vacuum exhaust system, a vacuum tank 57 and a vacuum pump 58 are provided via an electromagnetic valve 56. The atmospheric circuit is provided with a solenoid valve 59, the end of which is open to the atmosphere.

JP 63-132760 A

  By the way, in many of the die casting apparatuses, in order to improve the movement of the plunger tip 54 in the injection sleeve 53, the lubricant is dropped into the injection sleeve 53 from the hot water supply port 50 prior to the hot water supply of the molten metal. . However, when the lubricant is dropped onto the injection sleeve 53, the lubricant is combusted by the heat of the injection sleeve 53, and the combustion gas enters the mold cavity 52. When the injection speed of the molten metal is high, the molten metal is injected into the mold cavity 52 before the exhausted combustion gas of the lubricant is exhausted, and casting defects may occur due to the entrainment of the combustion gas of the lubricant. . On the other hand, even if the mold cavity is vacuum-depressurized as in the conventional vacuum die casting apparatus, the mold cavity 52 is short in several seconds after the plunger tip 54 closes the hot water supply port 50. Since the injection of molten metal into the gas is started, the combustion gas cannot be exhausted completely, and a casting defect due to gas entrainment occurs.

  The present invention has been made in view of such circumstances, and a problem to be solved is a vacuum die casting apparatus and a vacuum die casting method capable of effectively suppressing casting defects due to entrainment of combustion gas of a lubricant. It is to provide.

  According to the first aspect of the present invention, there is provided a pressure reducing means for vacuum reducing the inside of a mold cavity, an injection sleeve provided with a hot water inlet for pouring molten metal, and a mold by pressing the molten metal in the injection sleeve. The premise is a vacuum die casting apparatus including a plunger tip that is injected into a cavity. And in order to solve the said subject, in invention of Claim 1, the scavenging means which flows by flowing compressed gas toward the hot-water supply port from the mold cavity side is provided.

  In the above configuration, when the lubricant is dropped on the injection sleeve in order to improve the movement of the plunger tip, the lubricant burns with the heat of the injection sleeve to generate combustion gas. In the above configuration, when such combustion gas is generated, the scavenging means can scavenge the compressed gas from the mold cavity side toward the hot water supply port. If scavenging from the mold cavity side toward the hot water supply port is performed in this manner, the lubricant combustion gas generated in the injection sleeve is discharged from the hot water supply port, and the combustion gas to the mold cavity is discharged. Intrusion can be prevented. Therefore, according to the said structure, the casting defect by the entrainment of the combustion gas of a lubricant can be suppressed effectively.

  According to the second aspect of the present invention, if the scavenging means is operated from the time when the lubricant is dropped into the injection sleeve to the time when the hot water supply port is blocked by the plunger tip, the mold for the combustion gas of the lubricant It becomes possible to more reliably prevent entry into the cavity.

  According to the third aspect of the present invention, if switching means for switching which means of the decompression means and the scavenging means is connected to the mold cavity is provided, the scavenging and vacuum decompression can be performed only by operating the switching means. Switching can be performed easily.

  On the other hand, in order to solve the above-mentioned problem, as a vacuum die casting method for performing casting by injecting the molten metal supplied into the injection sleeve from the hot water supply port with a plunger tip and injecting into the vacuum mold cavity. The invention described in claim 4 includes a step of dripping a lubricant into the injection sleeve, and a step of scavenging by flowing compressed gas from the mold cavity toward the hot water supply port of the injection sleeve where the lubricant has been dropped. And vacuum depressurization of the mold cavity after completion of scavenging.

  In the above method, after the lubricant is dropped into the injection sleeve, scavenging is performed by flowing a compressed gas from the mold cavity side toward the hot water supply port. After the scavenging is completed, the mold cavity is subjected to vacuum decompression. When a lubricant is dropped on the injection sleeve to improve the movement of the plunger tip, the lubricant burns with the heat of the injection sleeve, and combustion gas is generated. At that time, in the above-described method, when such combustion gas is generated, scavenging is performed by flowing gas from the mold cavity side toward the hot water supply port. If such scavenging is performed, the combustion gas of the lubricant generated in the injection sleeve is discharged from the hot water supply port, and the invasion of the combustion gas into the mold cavity can be prevented. Therefore, according to the above method, casting defects due to entrainment of the combustion gas of the lubricant can be effectively suppressed.

  According to claim 5, if scavenging is started so as to start from the time when the lubricant is dropped and continues until the hot water inlet is closed by the plunger tip, the mold cavity of the combustion gas of the lubricant It is possible to more reliably prevent intrusion into the inside.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows typically the structure of the vacuum die-casting apparatus about one Embodiment of this invention. The figure which shows the state at the time of the lubricant dripping of the vacuum die-casting apparatus of the embodiment. The figure which shows the state at the time of the molten metal hot water supply of the vacuum die-casting apparatus of the embodiment. The figure which shows the state after the hot-water supply port obstruction | occlusion of the vacuum die-casting apparatus of the embodiment. The schematic diagram which shows the structure of the conventional vacuum die-casting apparatus typically.

  Hereinafter, an embodiment embodying a vacuum die casting apparatus and a vacuum die casting method of the present invention will be described in detail with reference to FIGS. The vacuum die casting apparatus and method of the present embodiment embody the present invention as an apparatus and method for casting an aluminum cylinder block.

  FIG. 1 shows the overall configuration of the vacuum die casting apparatus of the present embodiment. As shown in the figure, this vacuum die casting apparatus includes two molds, a fixed mold 1 and a movable mold 2. Then, by closing these two molds, a mold cavity 3 filled with molten metal is formed. The movable die 2 is provided with an extrusion pin 4 for releasing the cast aluminum cylinder block.

  Connected to the mold cavity 3 is an injection sleeve 6 in which a hot water supply port 5 for pouring molten metal is formed on the rear end side (left side in the figure). A plunger tip 8 fixed to the tip of a rod-like plunger 7 is disposed on the injection sleeve 6 so as to be slidable in the front-rear direction (left-right direction in the figure). A displacement sensor 9 that detects the displacement (stroke) of the plunger 7 is installed in the vicinity of the plunger 7.

  The mold cavity 3 is connected to a three-way valve 11 via a pressure reducing valve 10. In this vacuum die casting apparatus, the mold cavity 3 is also connected to the three-way valve 11 through a hole through which the push pin 4 passes.

  A pressure system connected to the compressed air pipe 12 is connected to the three-way valve 11. The compressed air pipe 12 is installed in a facility where a vacuum die casting apparatus is installed, and is a pipe that conveys compressed air to each part of the facility. In addition, the three-way valve 11 is connected to a vacuum tank 13 in which a negative pressure is stored and a decompression system provided with a vacuum pump 14 that decompresses the vacuum tank 13. The three-way valve 11 is configured to selectively connect either the pressurization system or the decompression system to the mold cavity 3.

  The three-way valve 11 of such a vacuum die casting apparatus is controlled by an electronic control unit 15. The electronic control unit 15 includes a central processing unit that performs arithmetic processing related to the control of the three-way valve 11, a read-only memory in which a control program and data are stored, and arithmetic results and sensor detection results of the central processing unit. And a random access memory for temporarily storing them. The electronic control unit 15 is provided with an input port for receiving a signal from the outside, and the detection signal of the displacement sensor 9 is input to the input port.

Hereinafter, the casting procedure of the aluminum cylinder block in such a vacuum die casting apparatus will be described with reference to FIGS.
When casting an aluminum cylinder block, first, the fixed mold 1 and the movable mold 2 are set in a vacuum die casting apparatus. And the residual heat of those metal molds is performed.

  When the residual heat is completed, a water-soluble release agent is applied to the cavity portions of the fixed mold 1 and the movable mold 2, and then the remaining water is removed by blowing compressed air onto the mold surface. When the preparation for casting is thus completed, the fixed mold 1 and the movable mold 2 are closed.

  When the mold is closed, the lubricant is dropped into the injection sleeve 6 through the hot water supply port 5 by an automatic dropping device (not shown). As the lubricant dropped at this time, a graphite-based oil-based lubricant is used. When the lubricant is dropped, the lubricant burns with the heat of the injection sleeve 6 and combustion gas is generated.

  At this time, the electronic control unit 15 controls the three-way valve 11 so as to connect the mold cavity 3 to the pressurizing system. When the pressurization system is connected to the mold cavity 3, as shown in FIG. 2, the compressed air flows from the mold cavity 3 side toward the hot water inlet 5 of the injection sleeve 6, thereby Then, scavenging in the mold cavity 3 and in the injection sleeve 6 is performed. Therefore, the combustion gas generated by the combustion of the lubricant is discharged from the hot water supply port 5 to the outside.

  When dripping of the lubricant is completed, as shown in FIG. 3, pouring of the molten metal is started. During pouring, scavenging in the mold cavity 3 and the injection sleeve 6 is continued by flowing compressed air from the mold cavity 3 toward the hot water supply port 5 of the injection sleeve 6.

  When it is confirmed from the detection result of the displacement sensor 9 that the pouring is finished and the plunger tip 8 has advanced to a position where the hot water inlet 5 is completely closed, the electronic control unit 15 releases the connection with the pressurizing system. The three-way valve 11 is controlled so that the mold cavity 3 is connected to the decompression system. When the mold cavity 3 is connected to the decompression system, air is discharged from the mold cavity 3 and the injection sleeve 6 as shown in FIG. 3, and decompression is started.

  When the pressure reduction is started, the plunger tip 8 is advanced at a high speed, whereby the molten metal is injected into the mold cavity 3. When a part of the molten metal reaches the pressure reducing valve 10, the pressure reducing valve 10 is closed.

Thereafter, the solidification of the molten metal filled in the mold cavity 3 is waited for. When the solidification is completed, the mold is opened and the aluminum cylinder block is taken out.
By the way, according to the results of the tests conducted by the inventors, when casting was performed without scavenging, the casting defect (nest) of the system having a diameter of about 2 mm at the maximum due to the entrainment of the combustion gas of the lubricant was found in the cylinder bore. However, when scavenging is performed, it has been confirmed that the diameter of the casting defect can be kept to Φ0.5 mm or less.

  In the above-described embodiment, the pressure reducing means is constituted by a pressure reducing system including the vacuum tank 13 and the vacuum pump 14. A scavenging means is constituted by a pressurization system connected to the compressed air pipe 12. The three-way valve 11 corresponds to the switching means.

According to the vacuum die casting apparatus and the vacuum die casting method of the present embodiment described above, the following effects can be achieved.
(1) A vacuum die casting apparatus according to the present embodiment includes a pressure reducing system for vacuum depressurizing the inside of a mold cavity 3, an injection sleeve 6 provided with a hot water supply port 5 for pouring molten metal, and an inside of the injection sleeve 6 And a plunger chip 8 for injecting the molten metal into the mold cavity 3. The vacuum die casting apparatus according to the present embodiment includes a compressed air pipe 12 that supplies compressed air, and flows the compressed air from the mold cavity 3 side toward the hot water supply port 5 so that the inside of the mold cavity 3 And scavenging in the injection sleeve 6 is performed. In such a vacuum die casting apparatus of this embodiment, when a lubricant is dropped on the injection sleeve 6 in order to improve the movement of the plunger tip 8, the lubricant burns with the heat of the injection sleeve 6 to generate combustion gas. At this time, in the vacuum die casting apparatus of the present embodiment, when such combustion gas is generated, the compressed cavity is connected from the mold cavity 3 side to the hot water supply port 5 by connecting the mold cavity 3 to the pressurizing system. It is possible to scavenge by flowing. Thus, if scavenging from the mold cavity 3 toward the hot water supply port 5 is performed, the combustion gas of the lubricant generated in the injection sleeve 6 is discharged from the hot water supply port 5, and the mold cavity. 3 will not enter. Therefore, according to the present embodiment, casting defects due to the entrainment of combustion gas of the lubricant can be effectively suppressed.

  (2) In the present embodiment, scavenging is performed from the time when the lubricant is dropped into the injection sleeve 6 to the time when the hot water supply port 5 is blocked by the plunger tip 8. Therefore, it is possible to more reliably prevent the combustion gas of the lubricant from entering the mold cavity 3.

  (3) In the present embodiment, the three-way valve 11 that switches which one of the decompression system and the pressurization system is connected to the mold cavity 3 is provided. Therefore, it is possible to easily switch between scavenging and vacuum decompression only by operating the three-way valve 11.

(4) Vacuum die casting of this embodiment in which casting is performed by pressing the molten metal supplied from the hot water supply port 5 into the injection sleeve 6 with the plunger tip 8 and injecting it into the mold cavity 3 which has been vacuum-depressed. In the method, casting is performed through the following steps.
A step of dripping the lubricant into the injection sleeve 6.
A step of scavenging by flowing compressed gas from the mold cavity 3 toward the hot water supply port 5 of the injection sleeve 6 to which the lubricant is dropped.
A step of performing vacuum decompression of the mold cavity 3 after the completion of scavenging.

  In such a vacuum die casting method of the present embodiment, after the lubricant is dropped into the injection sleeve 6, scavenging is performed by flowing a compressed gas from the mold cavity 3 toward the hot water supply port 5. . Then, after the scavenging is completed, the vacuum of the mold cavity 3 is reduced. When a lubricant is dropped on the injection sleeve 6 in order to improve the movement of the plunger tip 8, the lubricant is combusted by the heat of the injection sleeve 6, and combustion gas is generated. At this time, in the present embodiment, when such combustion gas is generated, scavenging is performed by flowing compressed air from the mold cavity 3 toward the hot water supply port 5. If such scavenging is performed, the combustion gas of the lubricant generated in the injection sleeve 6 is discharged from the hot water supply port 5 and the intrusion of the combustion gas into the mold cavity 3 is prevented. . Therefore, according to the vacuum die casting method of the present embodiment, it is possible to effectively suppress casting defects caused by the entrainment of the combustion gas of the lubricant.

In addition, the said embodiment can also be changed and implemented as follows.
In the above embodiment, the compressed air for scavenging is obtained from the compressed air pipe 12 installed in the facility where the vacuum die casting apparatus is installed. However, in a facility without such equipment, the vacuum die casting apparatus is dedicated. A compression pump may be provided, and compressed air for scavenging may be obtained from the pump.

In the above embodiment, the combustion gas is scavenged with compressed air, but scavenging may be performed using a compressed gas other than air, such as nitrogen.
In the above embodiment, the three-way valve 11 switches between scavenging and vacuum decompression, but the switching can also be performed by another means. For example, an open / close valve may be provided in each of the pressurization system and the pressure reduction system, and switching between scavenging and vacuum depressurization may be performed depending on which open / close valve is opened.

  In the above embodiment, switching from scavenging to vacuum depressurization is performed according to the detection result of the displacement sensor 9, but the switching timing may be confirmed by other methods. For example, even if a switch that opens and closes when the plunger tip 8 moves forward to a position that completely closes the hot water supply port 5 is switched from scavenging to vacuum depressurization according to the opening and closing of the switch, scavenging is performed at the same timing. It is possible to switch from vacuum to vacuum.

  In the above embodiment, the case where the present invention is embodied as a vacuum die casting apparatus and method for casting an aluminum cylinder block has been described. However, the vacuum die casting apparatus and method of the present invention cast other casting products. The present invention can also be embodied as an apparatus and a method for doing so.

  DESCRIPTION OF SYMBOLS 1 ... Fixed type, 2 ... Movable type, 3 ... Mold cavity, 4 ... Extrusion pin, 5 ... Hot water inlet, 6 ... Injection sleeve, 7 ... Plunger, 8 ... Plunger tip, 9 ... Displacement sensor, 10 ... Pressure reducing valve, 11 ... Three-way valve (switching means), 12 ... Compressed air piping (scavenging means), 13 ... Vacuum tank (pressure reducing means), 14 ... Vacuum pump (pressure reducing means), 15 ... Electronic control unit.

Claims (5)

Depressurizing means for vacuum depressurizing the inside of the mold cavity, an injection sleeve provided with a hot water inlet for pouring molten metal, and a plunger for pressing the molten metal in the injection sleeve and injecting it into the mold cavity In a vacuum die casting apparatus comprising a chip,
A vacuum die casting apparatus comprising scavenging means for scavenging by flowing compressed gas from the mold cavity side toward the hot water supply port. 2. The vacuum die casting apparatus according to claim 1, wherein the scavenging means is operated from a time point when a lubricant is dropped into the injection sleeve to a time point when the hot water supply port is closed by the plunger tip. 3. The vacuum die casting apparatus according to claim 1, further comprising a switching unit that switches which one of the decompression unit and the scavenging unit is connected to the mold cavity. 4. A vacuum die casting method in which casting is performed by injecting molten metal supplied into an injection sleeve from a hot water supply port with a plunger tip and injecting into a mold cavity that has been vacuum-depressed,
Dropping a lubricant into the injection sleeve;
Scavenging by flowing compressed gas from the mold cavity toward the hot water supply port of the injection sleeve to which the lubricant has been dropped; and
Performing vacuum decompression of the mold cavity after completion of the scavenging;
A vacuum die casting method comprising: The vacuum die casting method according to claim 4, wherein the scavenging is started from the time when the lubricant is dropped and continued until the hot water supply port is closed by the plunger tip.

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