JP5454068B2 - Vacuum die casting method - Google Patents

Description

  The present invention relates to a technique of a vacuum die casting method, and more particularly to a technique of a decompression method in a vacuum die casting method.

As a technique for reducing defects in a casting cavity such as an entrapment defect generated inside a die-cast product, a vacuum die casting method for performing die casting in a state where the inside of a cavity is decompressed is known and widely used.
In this vacuum die casting method, it is important to maintain a high degree of vacuum in the cavity at the time of injection, but it is necessary to provide a clearance (gap) between the injection sleeve and the injection tip. Occasionally, air flows in from this clearance, which makes it difficult to increase the degree of vacuum of the cavity.

Therefore, various techniques have been developed to ensure the degree of vacuum of the cavity at the time of injection. For example, the technique is disclosed in Patent Document 1 shown below and is publicly known.
In the prior art disclosed in Patent Document 1, a closing member that forms a decompression chamber that surrounds the open end portion is provided at the open end portion of the injection sleeve, and this closing member (decompression chamber) allows It is configured to ensure airtightness on the back side. And it is set as the structure which ensures reliably the vacuum degree of the cavity at the time of injection | emission by evacuating from both a decompression chamber and a cavity.

JP 2008-93712 A

  However, in the prior art disclosed in Patent Document 1, evacuation is performed from both the decompression chamber and the cavity in the entire injection process, and the timing of evacuation from the decompression chamber and the cavity is controlled. Absent. For this reason, in the injection process, the degree of vacuum between the decompression chamber and the cavity is abrupt, and there may be a difference in pressure between the decompression chamber and the cavity.

  For example, when the vacuum degree in the decompression chamber becomes excessively higher than the vacuum degree in the cavity, the molten metal is sucked out from the cavity side to the decompression chamber side, and the molten metal is inserted into the clearance (gap) between the injection sleeve and the injection tip. A problem occurs (see FIG. 4A). In this case, there is a problem that burrs, galling, and the like occur in the injection tip and the injection sleeve, and the life of the injection tip and the injection sleeve is significantly reduced.

  On the other hand, when the degree of vacuum of the cavity is excessively higher than the degree of vacuum of the decompression chamber, the lubricant applied to the injection chip is sucked out to the cavity side, and the lubricant is mixed into the molten metal. (See FIG. 4B). In this case, there is a problem that the lubricant heated by the molten metal is vaporized to generate bubbles, and a gas nest is generated in the die cast product.

  The present invention has been made in view of the present problems, and pays attention to the differential pressure before and after the injection tip in the injection sleeve, and controls the timing of evacuation from the decompression chamber and the cavity, respectively. It prevents the molten metal from being inserted into the clearance between the tip and the injection sleeve, and prevents the lubricant of the injection tip from mixing into the molten metal. The purpose is to reduce.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

That is, in claim 1, a space formed by a cavity formed in a mold, a runner communicating with the cavity, an injection sleeve communicating with the runner, and an injection tip inserted into the injection sleeve. A vacuum die casting method for evacuating the filling chamber and performing die casting by increasing the degree of vacuum in the filling chamber, wherein the molten metal is supplied to the filling chamber from a hot water supply opening that is an opening formed in the injection sleeve. The hot water supply port and the runway of the injection sleeve communicate with each other after the end of the supply and before the start of the injection operation due to the displacement of the injection tip toward the cavity in the injection sleeve. to form a vacuum chamber which is a space surrounding the the open end is of open end formed on the opposite other end to the one end side, vacuum exhaust from the filling chamber If, to start, and evacuation from the decompression chamber, the vacuum evacuation from the charging chamber, the evacuation from the decompression chamber, the vacuum evacuation means is a means for separate evacuation performed, wherein the after starting the injection operation, thereafter when the injection tip is displaced into the cavity side than the hot water supply port in said injection sleeve, until the end of the injection operation, evacuation from the filling chamber The pressure exhaustion from the decompression chamber is weakened or stopped, and the differential pressure between the filling chamber and the decompression chamber is adjusted to a pressure at which the molten metal is not inserted into the gap between the injection sleeve and the injection tip. To do.

  According to a second aspect of the present invention, the space is formed by a cavity formed in the mold, a runner communicating with the cavity, an injection sleeve communicating with the runner, and an injection tip inserted into the injection sleeve. A vacuum die casting method in which evacuation is performed from a filling chamber to perform die casting by increasing the degree of vacuum in the filling chamber, and a molten metal is supplied to the filling chamber from a hot water supply opening that is an opening formed in the injection sleeve. An open end that is formed at the other end of the injection sleeve and the other end of the injection sleeve that communicates with the runner after the hot water supply step is completed. A decompression chamber forming step for forming a decompression chamber that is a space surrounding the end, and after the decompression chamber forming step is completed, the injection tip is changed to the cavity side in the injection sleeve. After the injection step of injecting the molten metal into the cavity and the decompression chamber forming step is completed, and before the injection tip starts to be displaced toward the cavity in the injection sleeve, Vacuum exhaust from the filling chamber and the decompression chamber is started until vacuum injection from the filling chamber and the decompression chamber is started and until the injection tip is displaced to the cavity side from the hot water supply port in the injection sleeve. After the first pressure reducing step to continue, and after the injection tip is displaced to the cavity side than the hot water supply port in the injection sleeve, weakening or stopping the vacuum exhaust from the pressure reduction chamber, While adjusting the differential pressure between the filling chamber and the decompression chamber to a pressure at which the molten metal is not inserted into the gap between the injection sleeve and the injection tip A second depressurization step of continuing evacuation from the filling chamber until the injection step is completed, and in the first depressurization step and the second depressurization step, a vacuum from the filling chamber is provided. The exhaust and the vacuum exhaust from the decompression chamber are performed by a vacuum exhaust means which is a means for performing separate vacuum exhaust.

  In Claim 3, when starting said 1st pressure reduction process, said injection tip is arranged in the above-mentioned open end side rather than said hot-water supply port in said injection sleeve, and via said hot-water supply port, The filling chamber communicates with the decompression chamber.

  According to a fourth aspect of the present invention, the displacement speed of the injection tip is higher than the displacement speed in the injection process during the first pressure reduction process. To do.

According to a fifth aspect of the present invention, the decompression chamber is a cylindrical member whose inner dimension is larger than the outer dimension of the injection sleeve, and has a first end opened and a second end closed. And a second closing member that is a lid-like member attached to the outer peripheral surface of the injection sleeve and conforming to the shape of the one end portion.

  According to a sixth aspect of the present invention, the decompression chamber is configured such that the first closing member is disposed with one end portion of the first closing member facing the open end portion of the injection sleeve, By displacing the closing member toward the injection sleeve, the open end and the hot water supply port are inserted into the first closing member, and one end of the first closing member is inserted into the second closing member. It is formed by contacting the member.

  As effects of the present invention, the following effects can be obtained.

  In the first aspect, in the injection process, it is possible to prevent the differential pressure between the filling chamber and the decompression chamber from becoming excessively large, and it is possible to prevent the molten metal from being inserted into the clearance between the injection tip and the injection sleeve. Thereby, it can prevent that the lubricant apply | coated to the injection | pouring chip | tip mixes in a molten metal, and can suppress generation | occurrence | production of the casting hole defect (especially gas nest) in die-cast products. Furthermore, the amount of vacuum exhaust in vacuum die casting can be reduced, which can contribute to energy saving.

  According to the second aspect, in the injection process, it is possible to prevent the differential pressure between the filling chamber and the decompression chamber from becoming excessively large, and to prevent the molten metal from being inserted into the clearance between the injection tip and the injection sleeve. Thereby, it can prevent that the lubricant apply | coated to the injection | pouring chip | tip mixes in a molten metal, and can suppress generation | occurrence | production of the casting hole defect (especially gas nest) in die-cast products. Furthermore, the amount of vacuum exhaust in vacuum die casting can be reduced, which can contribute to energy saving.

  According to the third aspect, before the injection, the vacuum evacuation can be performed substantially evenly from before and after the injection tip, and the differential pressure generated before and after the injection tip can be suppressed. This can prevent the molten metal from being inserted into the clearance between the injection tip and the injection sleeve.

  According to the fourth aspect of the present invention, even when high-speed injection is performed, the molten metal can be reliably prevented from being inserted into the clearance between the injection tip and the injection sleeve.

  According to the fifth aspect, the decompression chamber can be formed with a simpler configuration.

  According to the sixth aspect, the decompression chamber can be formed with a simpler configuration.

The schematic diagram which shows the whole structure of the vacuum die-casting apparatus used for the vacuum die-casting method which concerns on one Example of this invention. The figure which shows the relationship between the vacuum exhaust time and the degree of vacuum in the vacuum die-casting method which concerns on one Example of this invention. Schematic diagram showing the state of occurrence of air segregation in vacuum die casting, (a) Schematic diagram showing the state of occurrence of air segregation in a vacuum die casting method according to an embodiment of the present invention, (b) Air in a conventional vacuum die casting method The schematic diagram which shows the generation | occurrence | production state of segregation. FIG. 4 is a schematic diagram showing a defect that occurs in the clearance between the injection sleeve and the injection tip, (a) a schematic diagram showing the state of insertion of the molten metal with respect to the clearance when the vacuum chamber is excessively higher in vacuum than the filling chamber, ) A schematic view showing a leakage state of the lubricant from the clearance with respect to the molten metal when the filling chamber has an excessively high degree of vacuum as compared with the decompression chamber. The schematic diagram which shows the favorable state of the clearance gap in the vacuum die-casting method which concerns on one Example of this invention. The schematic diagram which shows the whole structure of the vacuum die-casting apparatus of another embodiment used for the vacuum die-casting method which concerns on one Example of this invention. The flowchart which shows the vacuum die-casting method which concerns on one Example of this invention. The figure which shows the change of the injection speed in the vacuum die-casting process by the vacuum die-casting method concerning one Example of this invention. The schematic diagram which shows the operation | movement condition of the vacuum die-casting apparatus in the vacuum die-casting process (STEP-1 to STEP-2) by the vacuum die-casting method concerning one Example of this invention. The schematic diagram which shows the operation | movement condition of the vacuum die-casting apparatus in the vacuum die-casting process (STEP-3 to STEP-5) by the vacuum die-casting method concerning one Example of this invention. The schematic diagram which shows the operation | movement condition of the vacuum die-casting apparatus in the vacuum die-casting process (STEP-6) by the vacuum die-casting method which concerns on one Example of this invention. The schematic diagram which shows the operation | movement condition of the vacuum die-casting apparatus in the vacuum die-casting process (STEP-7-STEP-8) by the vacuum die-casting method which concerns on one Example of this invention. The schematic diagram which shows the operation | movement condition of the vacuum die-casting apparatus in the vacuum die-casting process (STEP-8-STEP-9) by the vacuum die-casting method which concerns on one Example of this invention.

Next, embodiments of the invention will be described.
First, an overall configuration of a vacuum die casting apparatus used in a vacuum die casting method according to an embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, a vacuum die casting apparatus 30 as an example of a vacuum die casting apparatus used in a vacuum die casting method according to an embodiment of the present invention includes a mold 1, an injection sleeve 2, an injection tip 3, an actuator 9, and a closing member 10. , A vacuum tank 18, a vacuum pump 19, open / close valves 20 and 21, a control device 22, a molten metal detection sensor 23, and the like.

The mold 1 is composed of a movable mold 1a and a fixed mold 1b, and a cavity 4 that is a cavity shaped like a product shape is provided on the mating surfaces of the molds 1a and 1b, and a molten metal 6 is supplied to the cavity 4. A runner 5 serving as a route is formed.
An injection sleeve 2 is attached to the mold 1 on the fixed mold 1b side, which is in communication with the runner 5 and serves as a path for supplying the molten metal 6.

The injection sleeve 2 is a tubular portion in which the molten metal 6 injected toward the cavity 4 can be stored, and a hot water supply port 2 a that is an opening for supplying the molten metal 6 from the ladle 7 is provided. Is formed. An open end 2b is formed at the end of the injection sleeve 2 opposite to the side connected to the fixed mold 1b.
An injection tip 3 is inserted into the injection sleeve 2 from the open end 2b side.

The injection tip 3 is a substantially cylindrical portion formed with an outer diameter substantially equal to the inner diameter of the injection sleeve 2 (however, smaller than the inner diameter of the injection sleeve 2), and is stored in the injection sleeve 2. This is a part for playing the role of pushing out the molten metal 6 toward the cavity 4 side. The injection tip 3 is supported by a support shaft 9 a provided in the actuator 9 so that the axis of the injection sleeve 2 is the same as that of the injection sleeve 2.
In the following, the space formed by the injection sleeve 2, the injection tip 3, the cavity 4, and the runner 5 and filled with the molten metal 6 in the injection process (see FIG. 1) is referred to as a filling chamber 11.

  The support shaft 9a is a shaft portion provided in the actuator 9 such as an air cylinder or a hydraulic cylinder, and is configured to be able to advance and retreat (reciprocate) in the axial direction. The injection tip 3 can be reciprocated in the injection sleeve 2 by disposing the injection tip 3 at the tip of the support shaft 9a.

  Further, a flange portion 8 is provided on the outer peripheral surface of the injection sleeve 2. The flange portion 8 is configured to form a wall surface that is substantially parallel to a plane that is substantially orthogonal to the sliding direction of the injection tip 3. Moreover, the position of this flange part 8 is made into the side displaced when the injection | pouring chip | tip 3 injects the molten metal 6, ie, the metal mold | die 1 side rather than the position where the hot-water supply port 2a is arrange | positioned.

A closing member 10 for forming a decompression chamber 12 described later is provided on the axis of the support shaft 9a.
The closing member 10 is a cylindrical member in which the end face 10a on the side where the injection tip 3 moves during injection is opened, and the supporting shaft 9a is attached to the boss 10d of the other end face 10c on the closed side. A through-hole 10e through which is slidably inserted is formed.

Further, a support shaft 9a is slidably inserted into a through hole 10e provided in the closed end surface 10c of the closing member 10, and a clearance between the support shaft 9a is sealed in the through hole 10e. Seal members 10f and 10f made of an O-ring or the like are provided.
Further, the inner size of the cylindrical closing member 10 is configured to be larger than the outer size of the injection sleeve 2, and the end surface 10a of the closing member 10 is displaced in the injection direction of the injection tip 3 (die 1 side). By doing so, the open end 2b of the injection sleeve 2 is inserted into the space inside the closing member 10.
A decompression chamber 12 (chamber) surrounding the open end 2b of the injection sleeve 2 by pressing the flange 10b provided on the end surface 10a of the closing member 10 against the flange 8 attached to the outer peripheral surface of the injection sleeve 2. ) Is formed.
The decompression chamber 12 referred to here is a space formed by the injection sleeve 2, the injection tip 3, and the closing member 10, and is a space formed on the back side of the filling chamber 11 with the injection tip 3 interposed therebetween (see FIG. 1). Means.

  Further, the closing member 10 is configured to move while maintaining the same axial center position as the injection tip 3 (support shaft 9a) by a support shaft 13a provided in an actuator 13 formed of an air cylinder, a hydraulic cylinder, or the like. ing.

  Further, in the flange portion 8 erected on the outer peripheral surface of the injection sleeve 2, a sealing member (not shown) configured by an O-ring or the like is provided on the side of the closing member 10 that faces the flange portion 10 b. This seal member is configured to seal a gap formed between the flange portions 8 and 10b in a state where the flange portions 8 and 10b are in pressure contact with each other. In addition, it is good also as a structure which provides a sealing member in the flange part 10b side of the closure member 10. FIG.

Further, the closing member 10 is provided with a suction port 15 for evacuating from the decompression chamber 12 which is a space formed in the closing member 10.
The term “evacuate” as used herein refers to connecting a pressure reducing device such as a vacuum pump 19 to a certain space, and exhausting the air existing in the space to the outside of the space, thereby reducing the pressure in the space to the atmospheric pressure. It means that the pressure is reduced to a lower pressure than the above (hereinafter the same).

  Further, the mold 1 is provided with a suction port 16 that communicates with the cavity 4 and evacuates from the cavity 4. A shut valve 17 for preventing the molten metal 6 from leaking from the suction port 16 at the time of injection is provided in the path connecting the cavity 4 and the suction port 16.

  The vacuum exhaust paths (vacuum piping) connected to the two suction ports 15 and 16 are connected to the vacuum pumps 19a and 19b via the vacuum tanks 18a and 18b, respectively. Whether the vacuum exhaust from the filling chamber 11 and the decompression chamber 12 is performed or not can be switched by the operation of the open / close valves 20 and 21 provided. The vacuum tanks 18a and 18b function as buffers for stabilizing the degree of vacuum by increasing the internal volume of each vacuum exhaust path (vacuum piping). For this reason, as the vacuum tanks 18a and 18b, those having an internal volume sufficiently larger than the internal volumes of the filling chamber 11 and the decompression chamber 12 are selected, whereby the degree of vacuum of the filling chamber 11 and the decompression chamber 12 is selected. It is possible to reach the target vacuum degree in a short time after the opening / closing valves 20 and 21 are opened.

In the configuration shown in FIG. 1, the operations of the injection chip 3 (actuator 9), the ladle 7, the closing member 10 (actuator 13), the shut valve 17, the vacuum pump 19, the opening / closing valve 20, etc. are interlocked by the control device 22. It is desirable to have a configuration that is controlled to do so.
A specific mechanism for operating each device is not particularly limited.

Further, in the vacuum die casting apparatus 30, the control device 22 is connected to a molten metal detection sensor 23 that is a means for detecting that the molten metal 6 has reached a predetermined part of the cavity 4.
The molten metal detection sensor 23 can detect whether or not the molten metal 6 is present at a predetermined portion of the cavity 4 by adopting, for example, an ultrasonic sensor.
The part where the presence of the molten metal 6 is detected by the molten metal detection sensor 23 detects the presence (liquid level) of the molten metal 6 before the molten metal 6 fills the cavity 4.
Then, in consideration of the timing at which the molten metal 6 arrives at the set predetermined site, the injection speed of the molten metal 6 and the response delay time of the actuator 9 and the opening / closing valves 20 and 21, the control device 22 controls the respective sites 9 and 20. -It is configured to control operations such as 21.

Here, the change in the degree of vacuum in the vacuum die casting method according to one embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the vacuum die casting apparatus 30 can evacuate the filling chamber 11 and the decompression chamber 12 from the two suction ports 15 and 16. Here, since the diameter of the suction port 15 connected to the decompression chamber 12 can be set larger than the diameter of the suction port 16, the injection tip 3 is positioned closer to the actuator 9 than the hot water supply port 2a. In this state, the evacuation on the filling chamber 11 side is performed through the decompression chamber 12, so that the degree of vacuum in the filling chamber 11 and the decompression chamber 12 can reach the target degree of vacuum in a shorter time. .

  That is, as shown in FIG. 2, by evacuating the filling chamber 11 and the decompression chamber 12 from the two suction ports 15 and 16, it is possible to perform evacuation in the viscous flow region in a shorter time. Thus, the degree of vacuum in the filling chamber 11 and the decompression chamber 12 can be increased efficiently (in a shorter time). Note that the evacuation in the molecular region is less effective due to evacuation from the two suction ports 15 and 16 and requires a certain amount of time, but the time required to reach the target degree of vacuum is the total. Can be shortened.

Here, the segregation of air, which is a phenomenon occurring in the cavity 4, will be described with reference to FIGS. 1 and 3.
In the conventional vacuum die casting apparatus, since the vacuum exhaust is performed only from the suction port 16 with respect to the filling chamber 11 (cavity 4), as shown in FIG. It was happening. Thus, the air that segregates at a position away from the suction port 16 has a property that it is finally discharged (that is, difficult to be discharged) in the vacuum evacuation of the molecular flow region, and the air that segregates in the lower part of the cavity 4 is die-cast. It was the cause of casting defects (entrainment defects) in the product.

  On the other hand, as shown in FIG. 1, when evacuating from the two suction ports 15 and 16 to the filling chamber 11 and the decompression chamber 12, as shown in FIG. The air segregates. Since the segregated air is located at a position relatively close to the suction port 16, the air that is gradually segregated by the vacuum exhaust in the viscous flow region is reduced by continuing the vacuum exhaust from the suction port 16. The position where air segregates can be shifted to a position closer to the suction port 16. Further, the air segregated in the vicinity of the suction port 16 is pushed out to the suction port 16 along the flow of the molten metal 6 at the time of injection and effectively exhausted. According to the vacuum die casting method according to the present embodiment, the occurrence of defects in the cavity due to the segregated air can be effectively reduced.

Furthermore, the state of the molten metal and the lubricant in the clearance between the injection sleeve and the injection tip will be described with reference to FIGS. 1, 4, and 5.
As shown in FIG. 1, when evacuating the filling chamber 11 and the decompression chamber 12 from the two suction ports 15 and 16, the degree of vacuum in the decompression chamber 12 is higher than the degree of vacuum in the filling chamber 11. 4A, the molten metal 6 is sucked out from the filling chamber 11 side to the decompression chamber 12 side, and the molten metal 6 is inserted into the clearance between the injection sleeve 2 and the injection chip 3 as shown in FIG. Occurs. In this case, burrs, galling, and the like occur in the injection tip 3 and the injection sleeve 2, causing a problem that the life of the injection tip 3 and the injection sleeve 2 is remarkably reduced.

  In contrast, when the degree of vacuum in the filling chamber 11 is excessively higher than the degree of vacuum in the decompression chamber 12, the lubricant 3a applied to the injection chip 3 is filled with the filling chamber 11 as shown in FIG. The phenomenon that the lubricant 3a is mixed into the molten metal 6 is sucked out to the side. In this case, the lubricant 3a heated by the molten metal 6 is vaporized to generate bubbles 3b, 3b..., And the gas nest in the die cast product increases.

  Therefore, when the degree of vacuum in each of the chambers 11 and 12 is adjusted so as not to cause an excessive difference in the degree of vacuum between the filling chamber 11 and the decompression chamber 12, as shown in FIG. The molten metal 6 is not inserted into the clearance. More specifically, as shown in FIG. 5, it is desirable that the molten metal 6 slightly enters the clearance. Thereby, it is possible to reliably prevent the lubricant 3a applied to the injection chip 3 from being sucked out and leaked to the filling chamber 11 side.

  That is, when using a vacuum die casting apparatus 30 for evacuating the filling chamber 11 and the decompression chamber 12 as shown in FIG. 1 from the two suction ports 15 and 16, the filling chamber 11 and the decompression chamber 12 are used. It is desirable to perform the injection process while adjusting so that the difference in vacuum degree (that is, the differential pressure) does not become excessively large. More specifically, as shown in FIG. It is desirable to adjust the balance of the degree of vacuum in each of the chambers 11 and 12 so as to generate a differential pressure enough to enter.

That is, the vacuum die casting method according to an embodiment of the present invention is a vacuum evacuation unit (each of which is a unit for performing evacuation from the filling chamber 11 and vacuum evacuation from the decompression chamber 12 separately. This is performed by the suction ports 15 and 16, vacuum pipes of different systems, and vacuum pumps 19a and 19b).
With such a configuration, the differential pressure generated before and after the injection tip 3 can be adjusted more finely.

Next, another embodiment of a vacuum die casting apparatus to which a vacuum die casting method according to an embodiment of the present invention is applied will be described with reference to FIG.
As shown in FIG. 6, a vacuum die casting apparatus 31, which is another embodiment of a vacuum die casting apparatus used in a vacuum die casting method according to an embodiment of the present invention, has a vacuum tank 18 and a vacuum as compared with the vacuum die casting apparatus 30 described above. The number of pumps 19 is reduced, and the difference is that a vacuum die casting apparatus 31 is constituted by one vacuum tank 18c and one vacuum pump 19c.

  With such a configuration, it is possible to reduce the number of vacuum tanks 18 and vacuum pumps 19 and the amount of vacuum exhaust paths (vacuum piping) while ensuring the same functions as the vacuum die casting apparatus 30. For this reason, the configuration of the vacuum die casting apparatus 31 can reduce the initial cost as compared with the vacuum die casting apparatus 30.

  Further, since the number of vacuum pumps 19 is reduced in the vacuum die casting device 31 (that is, only one vacuum pump 19c is provided), two vacuum pumps 19a and 19b are provided like the vacuum die casting device 30. In some cases, it is possible to reduce the power consumption due to the operation of the vacuum pump 19 as compared with the case where the operation is performed. In this case, it is possible to reduce running costs and contribute to energy saving.

That is, the vacuum die casting method according to one embodiment of the present invention is a vacuum exhaust means (same as the means for performing the same vacuum exhaust for the vacuum exhaust from the filling chamber 11 and the vacuum exhaust from the decompression chamber 12. This is performed by the system vacuum piping and vacuum pump 19c).
With such a configuration, the molten metal 6 can be prevented from being inserted into the clearance between the injection tip 3 and the injection sleeve 2 by the vacuum die casting apparatus 31 having a simpler configuration.

Next, a vacuum die casting process to which a vacuum die casting method according to an embodiment of the present invention is applied will be described with reference to FIGS.
As shown in FIGS. 7 and 9, in the vacuum die casting process by the vacuum die casting method according to one embodiment of the present invention, first, the movable die 1a is pressed against the fixed die 1b, and the die 1 is closed. (STEP-1).

At this time, the closing member 10 is displaced in the direction away from the mold 1 by shortening the support shaft 13 a of the actuator 13 in the direction away from the mold 1. At this time, the decompression chamber 12 is not yet formed, and the hot water supply port 2a is opened to the outside and exposed. The injection chip 3 is located closer to the actuator 9 than the hot water supply port 2a.
In this state, the ladle 7 injects the molten metal 6 from the hot water supply port 2a into the injection sleeve 2, and supplies the molten metal 6 into the injection sleeve 2 (filling chamber 11) (STEP-2).
At this time, the on-off valves 20 and 21 are both “closed”.

In this state, the vacuum pumps 19a and 19b are operated, and the insides of the vacuum exhaust paths (including the vacuum tanks 18a and 18b) closer to the vacuum pumps 19a and 19b than the open / close valves 20 and 21 are set in a predetermined manner. Increase to a vacuum level.
When a predetermined amount of molten metal 6 has been injected into the injection sleeve 2 (filling chamber 11), the process proceeds to the next step.

  Next, as shown in FIGS. 7 and 10, the closing member 10 is displaced to the mold 1 side by the actuator 13 and pressed against the flange portions 8 and 10b to form the decompression chamber 12 (STEP-3). ). Thereafter, the process proceeds to an injection process and a pressure reduction process.

  That is, in the vacuum die casting method according to one embodiment of the present invention, the decompression chamber 12 is a cylindrical member whose inner dimension is smaller than the outer dimension of the injection sleeve 2 and one end (end face 10a) is open. In addition, the closing member 10 is a first closing member whose other end portion (end surface 10c) is closed, and one end portion of the closing member 10 (the flange portion 10b of the end surface 10a) attached to the outer peripheral surface of the injection sleeve 2. ), And a flange portion 8 that is a second closing member that is a lid-like member that conforms to the shape of).

Further, in the vacuum die casting method according to one embodiment of the present invention, the decompression chamber 12 has the closing member 10 disposed such that the end surface 10a of the closing member 10 faces the open end 2b of the injection sleeve 2, By displacing the closing member 10 toward the injection sleeve 2, the open end 2b and the hot water supply port 2a are inserted into the closing member 10, and one end of the closing member 10 (the flange portion 10b of the end surface 10a) is inserted into the flange portion. 8 is formed by being brought into contact with 8.
With such a configuration, the decompression chamber 12 can be formed with a simpler configuration.

(Low-speed injection process and first decompression process)
In the vacuum die casting method according to an embodiment of the present invention, the injection process includes a low-speed injection process and a high-speed injection process. First, the low-speed injection process is executed.
When the low-speed injection process is started, as shown in FIGS. 7 and 10, the open / close valves 20 and 21 are both opened while maintaining the airtightness of the decompression chamber 12, and the decompression chamber 12 and the filling chamber 11 (cavity) Vacuum exhaust is performed from the suction ports 15 and 16 respectively connected to 4), and the first pressure reduction process is started (STEP-4).

  At this time, since the inside of each vacuum exhaust path (including each vacuum tank 18a, 18b) closer to each vacuum pump 19a, 19b than each open / close valve 20, 21 is raised to a predetermined degree of vacuum in advance, When the open / close valves 20 and 21 are opened, the degree of vacuum in the filling chamber 11 and the decompression chamber 12 can be quickly increased.

Next, as shown in FIGS. 7 and 8, while confirming the degree of vacuum of the decompression chamber 12 and the cavity 4 (STEP-5), the mold 1 is accelerated while accelerating the displacement speed of the injection tip 3 to a predetermined speed V _L. And after the displacement speed of the injection tip 3 reaches the speed V _L , the injection tip 3 is displaced toward the mold 1 while maintaining the displacement speed at the speed V _L. The filling rate of the molten metal 6 is increased (that is, the low-speed injection process is executed).

  Here, while the injection tip 3 is positioned closer to the actuator 9 than the hot water supply port 2a, the filling chamber 11 and the decompression chamber 12 communicate with each other via the hot water supply port 2a, and thus become an integral space. The degree of vacuum in the filling chamber 11 and the decompression chamber 12 is increased in a short time by evacuation from the suction ports 15 and 16.

That is, in the vacuum die casting method according to an embodiment of the present invention, when the first pressure reducing step is started, the injection tip 3 is disposed in the injection sleeve 2 closer to the open end 2b than the hot water supply port 2a. The filling chamber 11 and the decompression chamber 12 are communicated with each other through the port 2a.
With such a configuration, the vacuum evacuation can be performed substantially uniformly from the front and rear of the injection tip 3 before injection, and the differential pressure generated before and after the injection tip 3 can be suppressed. Thereby, the molten metal 6 can be prevented from being inserted into the clearance between the injection tip 3 and the injection sleeve 2.

  Further, while the injection tip 3 is located on the mold 1 side with respect to the hot water supply port 2a, the filling chamber 11 and the decompression chamber 12 are isolated by the injection tip 3, so that filling is performed by vacuum exhaust from the suction port 16. The degree of vacuum in the chamber 11 is increased, and the degree of vacuum in the decompression chamber 12 is increased by evacuation from the suction port 15.

  At this time, as shown in FIG. 10, the degree of vacuum in the filling chamber 11 (cavity 4) and the decompression chamber 12 is quickly increased by performing vacuum exhaust from both the filling chamber 11 (cavity 4) and the decompression chamber 12. (See FIG. 2). At this time, the evacuation speeds and the like by the vacuum pumps 19a and 19b are adjusted so that the difference in the degree of vacuum between the filling chamber 11 and the decompression chamber 12 (that is, the differential pressure) does not become excessively large.

  When the filling rate of the molten metal 6 in the filling chamber 11 reaches a predetermined set filling rate, the low-speed injection process is terminated, and the process proceeds to the high-speed injection process and the second decompression process.

(High-speed injection process and second decompression process)
Next, when the filling rate of the molten metal 6 in the filling chamber 11 reaches a predetermined set filling rate, the open / close valve 20 maintains the “open” state as shown in FIGS. The vacuum evacuation is continuously performed, the open / close valve 21 is set to “closed”, the vacuum evacuation from the decompression chamber 12 is stopped, and the process proceeds to the second decompression process (STEP-6).
Accordingly, the degree of vacuum of the decompression chamber 12 is prevented from being excessively increased as compared with the degree of vacuum of the filling chamber 11 (cavity 4), and the molten metal with respect to the clearance (gap) between the injection sleeve 2 and the injection tip 3 is prevented. 6 is prevented from entering.

  In this embodiment, when the filling rate of the molten metal 6 in the filling chamber 11 reaches a predetermined set filling rate, the opening / closing valve 21 is set to “closed” and the vacuum exhaust from the decompression chamber 12 is completely stopped. Although illustrated, for example, by adjusting the opening degree of the on-off valve 21, the vacuum exhaust amount from the decompression chamber 12 is reduced (that is, the vacuum exhaust from the decompression chamber 12 is weakened). Is possible.

  In this way, by controlling the operation of the open / close valves 20 and 21 so that the difference in the degree of vacuum between the filling chamber 11 and the decompression chamber 12 (that is, the differential pressure) does not become excessively large, as shown in FIG. While the molten metal 6 is not inserted into the clearance between the injection sleeve 2 and the injection tip 3, and the lubricant 3a applied to the injection tip 3 does not leak to the filling chamber 11 side, the injection process is performed. It can be carried out.

  More specifically, as shown in FIG. 5, it is desirable to adjust the clearance 6 so that the molten metal 6 slightly enters the clearance in order to surely prevent the leakage of the lubricant 3a. It is desirable to control the operation timing of each of the on-off valves 20 and 21 so that a differential pressure is generated to a certain extent.

When the filling rate of the molten metal 6 in the filling chamber 11 reaches a predetermined set filling rate, as shown in FIG. 8, the displacement speed of the injection tip 3 is accelerated to a predetermined speed V _H while moving toward the mold 1 side. At the same time, after the displacement speed of the injection tip 3 reaches the speed V _H , the injection tip 3 is displaced toward the mold 1 while maintaining the displacement speed of the injection tip 3 at the speed V _H , and the molten metal 6 is inserted into the cavity 4. Inject at high speed (ie, perform a high speed injection process).

  In the present embodiment, as shown in FIG. 11, the filling rate of the molten metal 6 in the filling chamber 11 is 100% (that is, the runway 5 is completely filled with the molten metal 6, and the cavity 4 is filled with the molten metal. 6 illustrates the case where the on-off valve 21 is set to “closed” and the vacuum exhaust from the decompression chamber 12 is stopped at the timing of reaching the state 6), but the vacuum exhaust from the decompression chamber 12 is stopped. The filling rate at the timing does not necessarily need to be 100%, and the filling rate is less than 100% (that is, the runner 5 is not filled with the molten metal 6), or the filling rate exceeds 100%. (That is, the molten metal 6 has entered the cavity 4).

  Next, as shown in FIGS. 7, 8, and 12, when the high-speed injection process proceeds and the molten metal detection sensor 23 detects that the injected molten metal 6 has reached a predetermined portion of the cavity 4, this detection information Is sent to the control device 22 (STEP-7).

And if the control apparatus 22 acquires the information that the molten metal 6 was detected, the control apparatus 22 will control the completion | finish timing of a high-speed injection process based on the detection timing of this information (STEP-7). More specifically, based on the timing at which the molten metal detection sensor 23 detects the molten metal 6, taking into account the response delay time of the support shaft 9a, it depends on the injection speed V _H (that is, the displacement of the support shaft 9a (injection tip 3)). Controls how long the displacement continues.

Further, when the control device 22 acquires information indicating that the molten metal 6 has been detected, the control device 22 sets the open / close valve 20 to “closed” and sets the open / close valves 20 and 21 to “close” (STEP−). 8).
It should be noted that the high-speed injection process proceeds during the response delay time from when the molten metal 6 is detected by the molten metal detection sensor 23 to when the opening / closing valve 20 is closed, so that the molten chamber 6 is filled with the molten metal 6. In addition, the detection part by the molten metal detection sensor 23 is set in consideration of the response delay time of the opening / closing valve 20.

In this manner, the open / close valve 20 is “closed” in accordance with the end timing of the high-speed injection process, so that unnecessary vacuum exhaust is not performed. At this time, the shut valve 17 is “closed”, so that the leakage of the molten metal 6 from the suction port 16 is surely prevented.
Thus, a series of injection processes (a low-speed injection process and a high-speed injection process) are completed.
In this embodiment, the case where the injection process is a two-stage injection of one stage each at a low speed and a high speed is illustrated, but the aspect of the injection process when the vacuum die casting method according to the present invention is applied is limited to this. Not what you want.

That is, in the vacuum die casting method according to an embodiment of the present invention, the displacement speed (that is, the injection speed) of the injection tip 3 is the displacement speed (that is, the low speed injection process) in the first decompression process (that is, the low speed injection process). Compared with the injection speed V _L ), the displacement speed (that is, the injection speed V _H ) in the injection process (that is, the high-speed injection process) in the second decompression process is made high (that is, V _H > V _L ). It is.
With such a configuration, even when high-speed injection is performed, the molten metal 6 can be reliably prevented from being inserted into the clearance between the injection tip 3 and the injection sleeve 2.

Then, as shown in FIGS. 7, 8 and 13, the displacement speed of the injection tip 3 is reduced to a predetermined speed V _LL while the molten metal 6 is completely filled in the cavity 4 (filling chamber 11). Then, after the displacement speed of the injection tip 3 reaches the speed V _LL , the displacement speed of the injection tip 3 is further lowered to the mold 1 side while maintaining the displacement speed at the speed V _LL. The molten metal 6 in the cavity 4 is pressurized.
Thereby, a series of pressurization processes are completed.

7 and 13, the movable mold 1a is displaced to open the mold 1 (STEP-9), and the die-cast product is released from the cavity 4 of the mold 1 (STEP-10). . Further, the closing member 10 is displaced in a direction away from the mold 1, and the decompression chamber 12 is opened in preparation for the next vacuum die casting process (STEP-11).
This completes a series of vacuum die casting processes according to an embodiment of the present invention.

  Then, as shown in FIG. 7, returning to (STEP-1) again, the series of steps (STEP-1) to (STEP-11) is repeatedly executed, thereby according to an embodiment of the present invention. Vacuum die casting by the vacuum die casting method can be repeatedly executed.

Next, the application effect of the vacuum die casting method according to an embodiment of the present invention will be described.
Analysis of the die volume of the die cast product manufactured by a series of vacuum die casting processes according to an embodiment of the present invention (the ratio of the volume of the die defect contained in the die cast product to the volume of the die cast product) As a result, (1) the volume ratio of the cast hole was reduced to about ダ イ as compared with the die-cast product manufactured by the vacuum die casting method in which only the conventional filling chamber 11 (cavity 4) was evacuated.
(2) Compared to a die-cast product manufactured by a vacuum die-casting method (that is, a vacuum die-casting method described in Patent Document 1) that evacuates from both the conventional filling chamber 11 (cavity 4) and the decompression chamber 12. It was also confirmed that the volume ratio of the cast hole was reduced to about ½.
That is, it has been confirmed that the vacuum die casting method according to one embodiment of the present invention has an effect in reducing the defects in the cast hole.

  In addition, the defects in the voids (i.e., bubbles) are (1) entrainment nest caused by air entrainment, (2) gas nest caused by bubbles generated by vaporizing the lubricant applied to the injection chip, 3) It can be classified into water remaining defects caused by water mixed in the molten metal. When analysis of the gas component contained in the casting defect (bubble) is performed, (1) in the case of the entrapment nest, (2) in the case of the gas nest, mainly carbon, (3) water remaining In the case of defects, hydrogen is mainly detected.

And about the die-cast product manufactured by the vacuum die-casting method concerning this invention, when the component analysis of the gas contained in a casting hole defect was performed, compared with the die-cast product manufactured by the conventional vacuum die-casting method, (2 ) It was confirmed that the detected amount of carbon, which is the main component of the gas nest, decreased.
In other words, the vacuum die casting method according to an embodiment of the present invention can suppress the lubricant 3a applied to the injection chip 3 from being mixed into the molten metal 6, and thus is particularly effective in reducing the gas nest among casting defects. It was confirmed to have an effect.

  That is, a vacuum die casting method according to an embodiment of the present invention includes a cavity 4 formed in a mold 1, a runner 5 communicating with the cavity 4, an injection sleeve 2 communicating with the runner 5, and the injection sleeve A vacuum die casting method for performing die casting by evacuating the filling chamber 11 which is a space formed by the injection chip 3 inserted into the die 2 and increasing the degree of vacuum in the filling chamber 11. After the completion of the supply of the molten metal 6 to the filling chamber 11 from the hot water supply port 2a which is the opening to be performed, before the start of the injection operation by the displacement of the injection tip 3 toward the cavity 4 in the injection sleeve 2 Further, a decompression that is a space surrounding the hot water supply port 2a and an open end 2b that is an open end formed at the other end of the injection sleeve 2 on the side opposite to the end communicating with the runner 5 12 and the evacuation from the filling chamber 11 and the decompression chamber 12 is started, and the injection tip 3 after the injection process is started is displaced in the injection sleeve 2 to the cavity 4 side from the hot water inlet 2a. After that, the vacuum exhaust from the decompression chamber 12 is weakened.

The vacuum die casting method according to one embodiment of the present invention includes a cavity 4 formed in a mold 1, a runner 5 communicating with the cavity 4, an injection sleeve 2 communicating with the runner 5, and the injection sleeve A vacuum die casting method for performing die casting by evacuating the filling chamber 11 which is a space formed by the injection chip 3 inserted into the die 2 and increasing the degree of vacuum in the filling chamber 11. A hot water supply process for supplying the molten metal 6 to the filling chamber 11 from the hot water supply opening 2a, which is an opening to be performed, and a side communicating with the hot water supply opening 2a and the runway 5 of the injection sleeve 2 after the hot water supply process is completed. A decompression chamber forming step of forming a decompression chamber 12 that is a space surrounding the open end portion 2b that is an open end portion formed at the other end opposite to the one end, and the decompression chamber formation step is completed After that, After the completion of the injection process in which the tip 3 is displaced toward the cavity 4 in the injection sleeve 2 and the molten metal 6 is injected into the cavity 4 and the decompression chamber forming step, the injection tip 3 is in the injection sleeve 2. Before starting the displacement toward the cavity 4 side, evacuation from the filling chamber 11 and the decompression chamber 12 is started, and when the injection tip 3 is displaced closer to the cavity 4 than the hot water supply port 2a in the injection sleeve 2 Until the first depressurization step, which is the first depressurization step of continuing the vacuum exhaust from the filling chamber 11 and the decompression chamber 12, and when the injection tip 3 is displaced in the injection sleeve 2 to the cavity 4 side from the hot water supply port 2a. Thereafter, the vacuum exhaust from the decompression chamber 12 is stopped, and the second reduction in which the vacuum exhaust from the filling chamber 11 is continued until the injection process is completed. A second depressurizing step is a step, in which comprises a.
With such a configuration, it is possible to prevent the differential pressure between the filling chamber 11 and the decompression chamber 12 from becoming excessively large in the injection process, and to prevent the molten metal 6 from being inserted into the clearance between the injection tip 3 and the injection sleeve 2. Thereby, it is possible to prevent the lubricant 3a applied to the injection chip 3 from being mixed into the molten metal 6 and to suppress the occurrence of a casting hole defect (particularly a gas hole) in the die-cast product. Furthermore, the amount of vacuum exhaust in vacuum die casting can be reduced, which can contribute to energy saving.

DESCRIPTION OF SYMBOLS 1 Mold 2 Injection sleeve 3 Injection tip 4 Cavity 5 Runway 6 Molten metal 11 Filling chamber 12 Decompression chamber 18 Vacuum tank 19 Vacuum pump 20 On-off valve 21 On-off valve 30 Vacuum die casting apparatus

Claims (6)

A cavity formed in the mold,
A runway communicating with the cavity;
An injection sleeve communicating with the runner;
An injection tip to be inserted into the injection sleeve;
Evacuate from the filling chamber, which is a space formed by
A vacuum die casting method for performing die casting by increasing the degree of vacuum of the filling chamber,
After the completion of the supply of the molten metal to the filling chamber from the hot water supply opening which is an opening formed in the injection sleeve, the injection operation is started by the displacement of the injection tip toward the cavity in the injection sleeve Before you do,
A decompression chamber is formed as a space surrounding the hot water supply opening and an open end portion that is an open end portion formed at the other end opposite to one end of the injection sleeve that communicates with the runner. as well as, starting the evacuation from said charging chamber, and a vacuum evacuation from the decompression chamber,
Evacuation from the filling chamber;
Evacuation from the decompression chamber;
Is performed by vacuum evacuation means which is a means for evacuating separately,
After the injection operation is started, after the injection tip is displaced to the cavity side from the hot water supply port in the injection sleeve, until the injection operation is finished,
While continuing evacuation from the filling chamber, weakening or stopping evacuation from the decompression chamber, the differential pressure between the filling chamber and the decompression chamber is reduced in the gap between the injection sleeve and the injection tip. Adjust the pressure so that the molten metal cannot be inserted,
A vacuum die casting method characterized by the above. A cavity formed in the mold,
A runway communicating with the cavity;
An injection sleeve communicating with the runner;
An injection tip to be inserted into the injection sleeve;
Evacuate from the filling chamber, which is a space formed by
A vacuum die casting method for performing die casting by increasing the degree of vacuum of the filling chamber,
A hot water supply step of supplying molten metal to the filling chamber from a hot water supply opening which is an opening formed in the injection sleeve;
After the hot water supply step is completed, the hot water supply opening and an open end portion which is an open end portion formed at the other end opposite to the one end communicating with the runner of the injection sleeve, A decompression chamber forming step of forming a decompression chamber that is a surrounding space;
After the completion of the decompression chamber forming step, the injection step of displacing the injection tip toward the cavity in the injection sleeve and injecting the molten metal into the cavity; and
After the completion of the decompression chamber forming step and before the injection tip starts to be displaced toward the cavity in the injection sleeve, vacuum exhaust from the filling chamber and the decompression chamber is started. And a first depressurization step of continuing evacuation from the filling chamber and the decompression chamber until the injection tip is displaced to the cavity side from the hot water inlet in the injection sleeve;
After the injection tip is displaced to the cavity side with respect to the hot water inlet in the injection sleeve, the vacuum exhaust from the decompression chamber is weakened or stopped to reduce the differential pressure between the filling chamber and the decompression chamber. Adjusting the pressure so that the molten metal is not inserted into the gap between the injection sleeve and the injection tip, and a second decompression step of continuing evacuation from the filling chamber until the injection step is completed,
With
In the first decompression step and the second decompression step,
Evacuation from the filling chamber;
Evacuation from the decompression chamber;
Is performed by vacuum evacuation means which is a means for evacuating separately,
A vacuum die casting method characterized by the above. When starting the first decompression step,
The injection tip,
Arranged on the open end side of the hot water outlet in the injection sleeve,
Through the hot water outlet,
Communicating the filling chamber and the decompression chamber;
The vacuum die casting method according to claim 2. The displacement speed of the injection tip is
Compared to the displacement speed in the injection step during the first decompression step,
The displacement speed in the injection process during the second decompression process is set to a high speed.
The vacuum die casting method according to claim 2 or 3, wherein the vacuum die casting method is performed. The decompression chamber is
A cylindrical member whose inner dimension is larger than the outer dimension of the injection sleeve, wherein one end is opened and the other end is closed;
A second closing member that is a lid-like member attached to the outer peripheral surface of the injection sleeve and conforming to the shape of the one end;
Formed by,
The vacuum die casting method according to any one of claims 1 to 3, wherein the vacuum die casting method is performed. The decompression chamber is
The first closing member;
By disposing one end portion of the first closing member facing the open end portion of the injection sleeve, and displacing the first closing member toward the injection sleeve side,
The open end and the hot water supply port,
Inserting into the first closure member,
One end of the first closing member is
Forming by contacting the second closing member;
The vacuum die casting method according to claim 5.

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