JP7721948B2 - Die casting machine injection unit - Google Patents

Description

The present invention relates to an injection device for a die-casting machine that supplies molten metal into an injection sleeve and injects the molten metal into a mold cavity using a plunger that moves back and forth.

Casting using a die-casting machine involves supplying molten metal into the injection sleeve, and then injecting and filling the mold cavity as the plunger moves forward. The molten metal is cooled and solidified within the mold cavity, and the cooled and solidified product is then removed from the mold cavity to obtain the cast product. The plunger is then moved backward, and molten metal is again supplied into the injection sleeve, and preparations for molding the next shot begin. This molding process is repeated until the planned number of cast products are obtained.

At this point, the injection sleeve is heated and deformed by the high-temperature molten metal, widening the gap between the injection sleeve and plunger, allowing the molten metal to penetrate the gap. The molten metal solidifies and adheres to the injection sleeve, creating molten metal residue. This molten metal residue causes wear and damage to the plunger as it moves forward and backward, further widening the gap between the injection sleeve and plunger and increasing the amount of molten metal that penetrates into the gap, accelerating the creation and accumulation of molten metal residue.

These large deposits of molten metal residue can rub against the plunger as it moves back and forth, causing it to peel off. When the peeled-off molten metal residue mixes with the molten metal and is injected into the mold cavity, it can cause casting defects such as blowholes and foreign matter contamination. Furthermore, if the plunger's forward movement becomes unstable due to friction with the molten metal residue, the molten metal in the injection sleeve can ripple and become violent, leading to casting defects such as air entrapment (void inclusion), poor molten metal wrinkles, and poor molten metal flow. Furthermore, friction with the molten metal residue causes wear on the plunger, making it unable to seal the molten metal during injection and filling, resulting in molten metal leakage, frequent casting defects, and making it impossible to maintain stable casting quality. This requires additional maintenance, such as temporarily halting molding and replacing the plunger. Furthermore, the repeated generation and peeling of molten metal residue can corrode and damage the injection sleeve, raising concerns about long-term production downtime due to the need for extensive part replacement, including the injection sleeve.

Therefore, it has been proposed to stabilize the quality of the cast products of the die casting machine by preventing the generation, accumulation, and peeling of molten metal residue inside the injection sleeve.
Patent Document 1 discloses that temperature control of the injection sleeve and plunger prevents the expansion of the gap due to thermal deformation caused by high-temperature molten metal, thereby preventing the generation of molten metal residue due to the insertion of the molten metal. Patent Document 2 discloses that a two-layer injection sleeve using alloys with different thermal conductivities improves the heat retention of the molten metal and prevents the generation of molten metal residue. Patent Document 3 discloses that multiple rings of different sizes with different outer diameters are arranged on the plunger. These multiple rings are automatically aligned along the inner diameter of the injection sleeve. This prevents uneven wear of the plunger and prevents the generation and accumulation of molten metal residue. Patent Document 4 discloses that a cleaning tool is inserted into the injection sleeve to forcibly remove foreign matter, such as molten metal residue, from the injection sleeve, thereby preventing the accumulation and peeling of molten metal residue.

Japanese Patent Application Publication No. 10-15652 Japanese Patent Application Laid-Open No. 2000-263208 Japanese Patent Application Laid-Open No. 2005-349397 JP 2017-47434 A

When molten metal is supplied into an injection sleeve that is set at a significantly lower temperature than the high molten metal temperature, the molten metal cools and solidifies at the point of contact with the injection sleeve, inevitably generating molten metal residue. Therefore, while the methods described in Patent Documents 1 and 2 may be able to reduce the generation of molten metal residue, it is difficult to eliminate it entirely, and they do not completely solve the casting defects caused by molten metal residue. Furthermore, with the method described in Patent Document 3, if molten metal residue is generated and accumulates inside the injection sleeve, the automatically aligned large and small rings move to avoid the molten metal residue, thereby preventing wear and tear on the plunger and injection sleeve. However, the plunger's scraping action is weak, and molten metal residue cannot be completely removed from the injection sleeve. In contrast, the method described in Patent Document 4 can reliably remove molten metal residue from the injection sleeve. However, it cannot be used simultaneously with casting, and casting must be temporarily suspended.

The present invention aims to provide an injection device for a die-casting machine that can reliably remove molten metal residue from inside the injection sleeve without interrupting the casting process, and that can stabilize the quality of cast products by injecting and filling clean molten metal free of molten metal residue.

The injection device of the die-casting machine of the present invention supplies molten metal into the injection sleeve and injects and fills the molten metal into the mold cavity using a plunger that moves back and forth.The plunger is characterized by having a seal tip that seals against molten metal leakage, a sleeve cleaning unit with a mixture of convex and concave portions that cleans the inside of the injection sleeve, a rod connecting unit that connects the plunger rod, and an injection drive unit that is connected to the plunger rod and moves the plunger back and forth.

In the injection device of the die-casting machine of the present invention, the convex portion and concave portion are continuous annular protrusion shapes and continuous annular groove shapes, and it is preferable that multiple protrusion shapes and groove shapes are arranged in parallel.

In the injection device of the die-casting machine of the present invention, the convex portion and concave portion are continuous spiral protrusion shapes and continuous spiral groove shapes, and it is preferable that multiple protrusion shapes and groove shapes are arranged in parallel.

Furthermore, in the injection device of the die-casting machine of the present invention, the convex portions and concave portions are discontinuous protrusion shapes and continuous planar shapes, and it is preferable that multiple protrusion shapes are arranged regularly or irregularly on the planar shape.

Furthermore, in the injection device of the die casting machine of the present invention, it is preferable that the injection drive unit further adds a rotational motion to the retraction movement of the plunger.

The present invention provides an injection device for a die-casting machine that can reliably remove molten metal residue from within the injection sleeve without interrupting the casting process, and can stabilize the quality of cast products by injecting and filling clean molten metal free of molten metal residue.

FIG. 1 is a conceptual diagram of an injection device of a die casting machine according to an embodiment. FIG. 2 is a conceptual diagram of a plunger according to the first embodiment. FIG. 3 is a flow diagram of a casting process using the plunger of FIG. 2 . FIG. 10 is a conceptual diagram of a plunger according to a second embodiment. FIG. 10 is a conceptual diagram of a plunger according to a third embodiment. FIG. 6 is a flow diagram of a casting process using the plunger of FIGS. 4 and 5 .

Preferred embodiments for carrying out the present invention will be described below with reference to the drawings. Note that the following embodiments do not limit the inventions according to the claims. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solutions of the inventions according to the claims. Furthermore, in the present embodiments, the scales and dimensions of each component may be exaggerated, and some components may be omitted.

[Die casting machine injection unit]
First, an injection device of a die casting machine according to an embodiment of the present invention will be described with reference to Figure 1. In the following description, the die casting machine according to this embodiment is based on a horizontal die casting machine, but the present invention is not limited to this.

The die-casting machine 100 shown in Figure 1 comprises a fixed mold 2 supported by a fixed platen (not shown), a movable mold 4 supported by a movable platen (not shown) and movable toward and away from the fixed mold 2, an injection device 10 that injects and fills the mold cavity with molten metal, and an injection control unit 40 that controls the operation of the injection device 10. Molten metal such as an aluminum alloy is injected and filled by the injection device 10 into the mold cavity 6 formed by the fixed mold 2 and the movable mold 4 to obtain a cast product.

The injection device 10 includes a cylindrical injection sleeve 12 into which molten metal is supplied, a columnar plunger 20 disposed inside the injection sleeve 12, and a plunger rod 14 connecting an injection drive unit 30 and the plunger 20. The injection drive unit 30 controls the forward and backward movement of the plunger 20 based on control data from an injection control unit 40.
Here, the direction closer to the mold cavity 6 is defined as the forward F, the movement in the forward F direction is defined as the forward movement of the plunger 20, the direction away from the mold cavity 6 is defined as the backward B, and the movement in the backward B direction is defined as the backward movement of the plunger 20. In addition, the completion position of the forward movement of the plunger 20 is defined as the injection completion position FE, and the completion position of the backward movement of the plunger 20 is defined as the standby position BE.

While the plunger 20 waits at standby position BE, molten metal is supplied into the injection sleeve 22 from the pouring port 16 on the injection sleeve 12 using a melt supply device (not shown). The plunger 20 is then advanced to the injection completion position FE, and the molten metal in the injection sleeve 12 is injected and filled into the mold cavity 16. After a pressure-holding filling and cooling process to compensate for solidification shrinkage that occurs as the injected molten metal cools and solidifies, the fixed mold 2 and movable mold 4 are opened, and the cooled and solidified casting is removed from the mold cavity 6. At the same time, the plunger tip 20 is retracted to standby position BE, and the process proceeds to the preparation process for the next casting shot.

If necessary, the injection sleeve 12 may be provided with a cooling mechanism (not shown) that includes a flow path through which a cooling medium such as cooling water flows. It is also preferable to apply a lubricant to the sliding surfaces between the injection sleeve 12 and plunger 20 to prevent wear and tear on the plunger 20, stabilize the sliding condition, and prevent molten metal from adhering. The plunger 20 may also be provided with a cooling mechanism that includes a flow path through which a cooling medium such as cooling water flows.

[Plunger of First Embodiment]
Next, a plunger according to a first embodiment of the present invention will be described with reference to Fig. 2. Fig. 2 is an enlarged view of the plunger 20. The plunger 20 of the injection device 10 suitable for the first embodiment of the present invention includes, in order from the front F to the rear B, a seal tip portion 22, a sleeve cleaning portion 24, and a rod connecting portion 26, as shown in Fig. 2.

The seal tip portion 22 serves to seal the molten metal inside the injection sleeve 12 during the injection filling process so that the molten metal does not leak to the rear of the plunger 20. Therefore, the shape of the seal tip portion 22 is made cylindrical, which is approximately the same as the shape of the inner wall surface 12U of the cylindrical injection sleeve 12.
Here, the outer diameter 22R of the seal tip portion 22 is set based on the gap between the injection sleeve 12 and the seal tip portion 22, taking into account thermal deformation and thermal expansion due to the temperature of the molten metal, while ensuring the sealing of the molten metal and preventing galling damage due to strong contact between the plunger 20 and the injection sleeve 12. The length 22L of the seal tip portion 22 is set to a value that reliably ensures the sealing of the molten metal, taking into account the melt viscosity of the molten metal, the casting pressure during injection filling, and the outer diameter 22R. These settings may be determined by calculation or based on empirical values. For example, for a large die casting machine with a clamping force of 10,000 KN or more, experimental results show that the outer diameter 22R is set so that the gap between the injection sleeve 12 and the seal tip portion 22 is approximately 5/100 to 5/10 mm, and the ratio of the length 22L to the outer diameter 22R (22L/22R) is preferably set to approximately 0.3 to 3.0. This ensures that the molten metal is sealed securely by the seal tip 22 during injection filling, stabilizing the casting quality. Furthermore, smooth forward movement of the plunger 20 is ensured, preventing casting defects caused by fluctuations in the forward movement.

Here, the corner 22F on the front F side of the seal tip 22 is rounded, while the corner 22B on the rear B side is not. This is intended to allow the unrounded corner 22B to scrape the inner wall surface 12U of the injection sleeve 12 during the plunger 20's retreating movement after injection filling is complete, thereby efficiently removing molten metal residue adhering to the inner wall surface 12U of the injection sleeve 12. Furthermore, during the plunger 20's forward movement during injection filling, the rounded corner 22F allows the plunger 20 to glide smoothly through the injection sleeve 12, preventing the forced removal of molten metal residue. As a result, casting defects caused by molten metal residue can be prevented. At the same time, the stable forward movement of the plunger 20 ensures high-quality castings. For large die-casting machines with a clamping force of 10,000 kN or more, the rounded corner 22F is preferably approximately 0.5R to 5R.

Next, the sleeve cleaning section 24 serves to scrape off and remove molten metal residue that has accumulated inside the injection sleeve 12 when the plunger 20 is retracted. Therefore, multiple convex sections 242, which act as cutters to scrape off molten metal residue, and multiple concave sections 244, which act as containers to collect the scraped molten metal residue, are arranged in parallel from the front F to the rear B in the direction of the plunger 20's advancement and retreat, forming an uneven shape. This uneven arrangement allows the molten metal residue to be scraped off and collected simultaneously, improving efficiency. It is preferable to arrange multiple uneven sections within the range of the sleeve cleaning section 24.

Here, the convex portion 242 is equivalent to the outer diameter 22R of the seal tip portion 22 and has a continuous annular protrusion shape that is perpendicular to the direction of movement of the plunger 20. Furthermore, the length 242L of the convex portion 242 is made as small as possible based on the molten metal temperature, casting pressure, and the strength of the steel used in the sleeve cleaning portion 24, and the number of convex portions 242 arranged is increased to prioritize the efficiency of scraping off molten metal residue (the number of convex portions 242 arranged in Figure 2 is five). Based on experimental results, for example, in large die-casting machines with a clamping force of 10,000 KN or more, it is preferable to set the length 242L/outer diameter 22R to approximately 0.03 to 0.3.

The recess 244 is recessed from the protrusion 242 to capture the scraped molten metal residue, and is a continuous, annular groove parallel to the protrusion 244. The groove depth and length 244L of the recess 244 groove shape indicate the size of the container for capturing the scraped molten metal residue. While a larger container increases the collection margin, the depth should be set within an appropriate range, taking into account the constraints described below. For example, if the plunger 20 is equipped with a cooling mechanism including a flow path for circulating a cooling medium such as cooling water, it is preferable to set the groove depth of the recess 244 so as not to interfere with this cooling mechanism. Furthermore, to prevent the collected molten metal residue from leaking out the rear of the plunger 20, it is preferable to set the groove depth to be recessed from the rod connecting portion 26. Furthermore, if the length 244L of the recess 244 is set too large, it becomes impossible to provide a large number of protrusions 242, which would affect the efficiency of scraping the molten metal residue. If scraping efficiency is prioritized and an adequate number of convex portions 242 are to be arranged, the plunger 20 will become larger. Therefore, based on experimental results, for example, in large die casting machines with a clamping force of 10,000 KN or more, it is preferable to set 242L = 244L.

Here, the corner 242F on the front F side of the convex portion 242 and the corner 242B on the rear B side are not rounded. The convex portion 242 is fixed to the plunger 20. This strengthens the scraping force of the convex portion 242, allowing the molten metal residue to be efficiently removed during both the forward and backward movements of the plunger 20. Even if molten metal residue is detached during the forward movement of the plunger 20, it can be reliably collected in the recess 244, preventing it from mixing with the molten metal. Furthermore, during the retraction of the plunger 20, the convex portion 242 scrapes off the molten metal residue, which is then immediately collected in the recess 244 and then discharged outside the injection sleeve 12. This completely prevents molten metal residue from mixing with the molten metal in the next shot, ensuring that casting defects caused by molten metal residue are prevented.

Furthermore, even if wear and tear on the seal tip 22 reduces its sealing ability against molten metal, causing a problem in which molten metal leaks backward from the plunger 20, the sleeve cleaning section 24 adjacent to the seal tip 22 can stop the leakage of molten metal by utilizing the following three functions. The first function is that the protrusion 242 of the sleeve cleaning section 24 has the same outer diameter as the seal tip 22, so like the seal tip 22, the protrusion 242 also has the sealing ability against molten metal. The second function is that any molten metal that leaks beyond the protrusion 242 is captured in the recess 244, preventing the leakage of molten metal. The third function is that the continuous arrangement of the protrusions 242 and recesses 244 is similar to a sealing structure that utilizes the pressure relief effect of a labyrinth shape that continuously combines narrow and wide passages, and therefore is believed to be able to similarly seal molten metal. As a result, it is possible to avoid sudden interruptions to casting due to molten metal leakage.

The rod connection portion 26 is the part that connects the plunger rod 14, which transmits the driving force of the injection drive portion 30. Therefore, the rod connection portion 26 must have dimensions that allow it to reliably connect to the plunger rod 14, accurately transmit the driving force of the injection drive portion 30, be strong enough to handle the injection speed and casting pressure of the injection filling process, and not affect the cooling mechanism of the plunger 20. Furthermore, when the plunger 20 is waiting at standby position BE, the sleeve cleaning portion 24 must extend outside at position B behind the injection sleeve 12, and the rod connection portion must have dimensions that satisfy this. In other words, the plunger 20 performs a cleaning process in which it cleans up the collected molten metal residue at standby position BE.

In the plunger 20 according to the first embodiment shown in FIG. 2, the seal tip portion 22, sleeve cleaning portion 24, and rod connecting portion 26 are integrally formed. However, specific portions may be separate components, or all portions may be separate components. For example, the seal tip portion 22, which is subject to severe damage due to direct contact with the molten metal, may be formed as a separate component. In this case, the seal tip portion 22 is treated as a consumable item, minimizing the number of parts that need to be replaced. Furthermore, the convex portion 242 and concave portion 244 of the through-hole cleaning portion 24 are formed as separate components. In this case, only the convex portion 242, which is subject to severe damage due to scraping off molten metal residue, is replaced, minimizing the number of replacement parts and reducing maintenance costs, and extending the life of the plunger 20. Regardless of which components are formed as separate components, each component is firmly fastened to the plunger 20. In particular, the sleeve cleaning portion 24, which scrapes off molten metal residue, is securely fastened.

[Casting of the first embodiment]
Next, a casting process using the plunger 20 according to the first embodiment shown in Fig. 2 will be described with reference to Fig. 3. The fixed mold 2 and the movable mold 4 are clamped to form a mold cavity 6, the plunger 20 is waiting at the waiting position BE, and casting begins with molten metal being supplied into the injection sleeve 12 from a melt supply device (not shown) or the like.

Based on the control data for injection speed, speed switching position, and casting pressure set in the injection control unit 40, the injection drive unit 30 moves the plunger 20 forward via the plunger rod 14 from the standby position BE to the injection completion position FE. During this forward movement of the plunger 20, the molten metal in the injection sleeve 12 is injected and filled into the mold cavity 6 through the processes of low-speed injection, high-speed injection, and high-pressure filling. After the molten metal has been injected and filled, the forward movement of the plunger 20 is stopped. The stop position of the plunger 20 at this time is the injection completion position FE. Note that the injection completion position FE may also fluctuate due to variations in the amount of molten metal supplied to the injection sleeve 12, etc. In other words, during the low-speed injection, high-speed injection, and high-pressure filling processes, particularly during the high-pressure filling process, variations in the amount of molten metal supplied act as a holding pressure to compensate for solidification shrinkage that occurs as the molten metal injected and filled into the mold cavity 6 cools and solidifies, resulting in fluctuations in the injection completion position FE.

After the cooling step, the fixed mold 2 and the movable mold 4 are opened, and the casting is removed from the mold cavity 6, completing the casting process. The process then proceeds to the preparation step for the next shot.
In parallel with this molding operation, the plunger 20 moves backward from the injection completion position FE toward the standby position BE based on the setting value of the injection control unit 40. When the plunger 20 reaches the standby position BE, the backward movement is stopped, and the plunger 20 is cleaned, for example, by spraying cleaning air from an air blow cleaning device (not shown) or by using a cleaning tool such as a rotating brush. This cleaning is a cleaning process in which the molten metal residue scraped off by the convex portion 242 of the sleeve cleaning unit 24 and collected in the concave portion 244 is removed. Once the molten metal residue has been cleaned, the process proceeds to a preparation process for the next shot, such as supplying molten metal into the injection sleeve 12.

Here, the forward movement of the plunger 20 is a straight movement, and the seal tip 22 reliably seals the molten metal, accurately injecting and filling the molten metal into the mold cavity 6. At the same time, the convex portion 242 of the sleeve cleaning portion 24 scrapes off molten metal residue inside the injection sleeve 12, and the concave portion 244 collects the scraped off molten metal residue, preventing it from becoming contaminated with the molten metal. Furthermore, the rounded corner portion 22F of the seal tip 22 smooths the forward movement of the plunger 20, resulting in stable casting quality.
The plunger 20 moves backward in a straight line. The convex portion 242 of the sleeve cleaning portion 24 scrapes off the molten metal residue inside the injection sleeve 12, and the concave portion 244 collects the scraped molten metal residue, thoroughly cleaning the plunger 20 in the cleaning process. This allows the injection sleeve 12 to be kept clean at all times, completely preventing the intrusion of molten metal residue.
In this way, the injection sleeve 12 can be cleaned thoroughly during the molding process without interrupting the casting process, thereby realizing stable production of high-quality castings without casting defects.

[Plunger of Second Embodiment]
Next, a plunger according to a second embodiment of the present invention will be described with reference to FIG. 4 . FIG. 4 is an enlarged view of the plunger 20. As shown in FIG. 4 , the plunger 20 of the injection device 10 suitable for the second embodiment of the present invention includes, in order from the front F to the rear B, a seal tip portion 22, a sleeve cleaning portion 27, and a rod connecting portion 26. The seal tip portion 22 and the rod connecting portion 26 are the same as those in the first embodiment, and therefore their description will be omitted. The sleeve cleaning portion 27, which differs from the first embodiment, will be described in detail. The integrated structure and divided structure of the plunger 20, as well as the behavior of the plunger 20 during forward movement, are the same as those in the first embodiment, and therefore their description will be omitted. The retraction movement of the plunger 20 will be described in detail.

When the plunger 20 retracts, the sleeve cleaning section 27 plays a role in scraping off and removing molten metal residue that has accumulated inside the injection sleeve 12. To this end, multiple convex sections 272, which act as cutters to scrape off molten metal residue, and concave sections 274, which act as containers to collect the scraped molten metal residue, are arranged in parallel from the front F to the rear B in the direction of the plunger 20's advancement and retreat, forming an uneven shape. This uneven arrangement allows the molten metal residue to be scraped off and collected simultaneously, improving efficiency. It is preferable to have a large number of uneven arrangements within the range of the sleeve cleaning section 24.

The protrusion 272 has the same outer diameter 22R as the seal tip 22 and has a continuous spiral protrusion shape extending from the seal tip 22 toward the rod connecting portion 26. It is preferable that the length 272L and the corners 272F and 272B of the protrusion 272 be the same as in the first embodiment.

The recess 274 is recessed more than the protrusion 272 in order to collect the scraped molten metal residue, and has a continuous spiral groove shape arranged in parallel with the protrusion 272. The groove depth and length 274L of the groove shape of this recess 274 indicate the size of the container that will collect the scraped molten metal residue, and are preferably the same as in the first embodiment. Furthermore, the protrusion 274 and recess 274 are fixed to the plunger 20, as in the first embodiment.

In the second embodiment, the plunger 20 retracts while rotating. This dual action—the retraction and rotation of the convex portion 272—synthetically doubles the scraping efficiency of molten metal residue, completely removing the molten metal residue from the injection sleeve 12 and further cleaning the interior of the injection sleeve 12. Furthermore, the concave portion 274 has a continuous spiral groove shape extending from the seal tip portion 22, which is parallel to the convex portion 272, toward the rod connecting portion 26. This prevents the scraped molten metal residue from filling the concave portion 274 and allows it to be continuously discharged from the injection sleeve 12 toward the rear B of the plunger 20, completely cleaning the interior of the injection sleeve 12. This means that the rotational direction of the plunger 20 and the spiral direction of the concave portion 274 are the same, flowing from the front F toward the rear B. This prevents, for example, scraped-off molten metal residue from clogging the recess 274 and causing it to become eccentric, which can cause the plunger 20 to move uncontrollably when retracting or rotating, thereby damaging the injection sleeve 12 and plunger 20.

[Plunger of the Third Embodiment]
Next, a plunger according to a third embodiment of the present invention will be described with reference to FIG. 5. FIG. 5 is an enlarged view of the plunger 20. As shown in FIG. 5, the plunger 20 of the injection device 10 suitable for the third embodiment of the present invention includes, in order from the front F to the rear B, a seal tip portion 22, a sleeve cleaning portion 28, and a rod connecting portion 26. The sleeve cleaning portion 28, which differs from the first and second embodiments, will now be described. As with the second embodiment, the third embodiment is also characterized by the fact that the plunger 20 moves backward while rotating.

The sleeve cleaning section 28 in the third embodiment further enhances its role of scraping off and removing molten metal residue accumulated within the injection sleeve 12. To this end, the configuration maximizes the number of protrusions 282, which act as cutters to scrape off molten metal residue. Multiple discontinuous protrusions 282, each with a diameter equal to the outer diameter 22R of the seal tip section 22, are regularly or irregularly arranged relative to a continuous, flat recess 284 recessed from the seal tip section 22 and the rod connecting section 26. The size (length 282L and width 282S) and arrangement (spacing 284L and spacing 284S) of the protrusions 282 should be set to maximize the number of arrangements within the range of the sleeve cleaning section 28, taking into account the strength of the steel used in the sleeve cleaning section 28.

In the third embodiment, the efficiency of scraping molten metal residue from the injection sleeve 12 is maximized during all of the plunger 20's forward, backward, and rotational movements, ensuring a very clean injection sleeve 12 and completely preventing the intrusion of molten metal residue. Here, the convex portions 282 shown in FIG. 5 are aligned at equal intervals in the forward/backward and rotational directions of the plunger 20. However, this is not limited to this. For example, the convex portions 282 may be randomly arranged, or may be arranged so that the front, rear, left, and right convex portions 282 partially overlap. Furthermore, multiple convex portions 282 may be arranged in a spiral, and the rotation of the plunger 20 may be used to discharge the scraped molten metal residue to the rear B side of the plunger 20. Furthermore, in order to increase the efficiency of scraping molten metal residue, it is preferable that the convex portions 282 not be rounded. While the convex portions 282 are rectangular, they may also be cylindrical or polygonal.

[Casting using the plungers of the second and third embodiments]
Next, casting using plungers according to second and third embodiments of the present invention will be described with reference to Fig. 6. Explanations of parts that overlap with the casting of the first embodiment will be omitted, and only parts that show the characteristics of the second and third embodiments will be described in detail.

The plunger 20 moves forward from the standby position BE toward the injection completion position FE, where the molten metal is injected and filled into the mold cavity 6. After the pressure holding and cooling steps are completed, the mold is opened, the casting is removed, and preparations for molding the next shot begin.
At the same time, the plunger 20 moves backward from the injection completion position FE toward the standby position BE based on the setting value of the injection control unit 40. When the plunger 20 reaches the standby position BE, the backward movement is stopped, and the plunger 20 is cleaned, for example, by spraying cleaning air from an air blow cleaning device (not shown) or by using a cleaning tool such as a rotating brush. This is a cleaning process in which the molten metal residue scraped off from the injection sleeve 12 by the convex portion 282 and collected in the concave portion 284 is removed. Once the molten metal residue has been cleaned, the cleaning process ends, and the process proceeds to a preparation process for the next shot, such as supplying molten metal into the injection sleeve 12.

Here, the forward movement of the plunger 20 in the casting process is a straight movement, similar to the casting of the first embodiment, and the same improvement effect as in the first embodiment is obtained.
In the casting processes of the second and third embodiments, the plunger 20 is characterized by retracting while rotating from the injection completion position FE toward the standby position BE. In other words, the retraction and rotation of the plunger 20 synergistically double the efficiency of scraping off molten metal residue, enabling complete removal of molten metal residue from the injection sleeve 12 and complete prevention of molten metal residue contamination.

Furthermore, in the plunger 20 of the second embodiment, the combination of the spiral recess 274 and the rotational movement allows the scraped molten metal residue to be efficiently discharged out of the injection sleeve 12 at the rear B of the plunger 20, making it possible to prevent problems caused by clogging of the molten metal residue. The inclination direction of the spiral recess 274 is set so that the molten metal residue can be transported in the direction of the rear B of the plunger 20 depending on the direction of rotation of the rotational movement.
Furthermore, in the plunger 20 of the third embodiment, the numerous protrusions 282 rotate like rotating brushes, greatly increasing the efficiency of scraping off molten metal residue, thereby achieving a clean state in which no molten metal residue remains inside the injection sleeve 12, enabling the stable production of high-quality castings.

After the plunger 20 reaches the standby position BE, its retraction stops, but its rotation continues. When the elapsed time of the timer, which is started when the plunger 20 stops retracting, reaches the preset rotation time TB, the rotation of the plunger 20 stops and preparations for molding the next shot begin. It is preferable to continue a cleaning process, such as air blowing, while the plunger 20 is rotating. The rotation of the plunger 20 is performed by a rotary drive device (not shown). For example, the injection drive unit that moves the plunger 20 forward and backward may use a commercially available combined hydraulic cylinder capable of both linear and rotary motion. Alternatively, the linear motion may be performed using a general hydraulic cylinder, with transmission switching via a clutch, while the rotational motion may be performed using a rotary drive device that combines an electric motor and a rotary screw mechanism.

In this way, in the casting molding of the second and third embodiments, as in the casting molding of the first embodiment, the injection sleeve 12 can be cleaned thoroughly during the molding process without interrupting the casting molding, thereby realizing the stable production of high-quality castings without casting defects.
In the above description, the sleeve cleaning units of the plungers according to the first, second, and third embodiments are used independently, but the present invention is not limited to this, and may be, for example, a sleeve cleaning unit that combines the first and second embodiments, or a sleeve cleaning unit that combines the three embodiments, and may be selected appropriately depending on the type of molten metal used, the details of the casting, etc. In this case, it is also possible to obtain a high-quality casting.

[Variations]
Although the preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the scope described in the above-described embodiments. Various modifications and improvements can be made to the above-described embodiments.

In the above-described embodiment, the invention is described as being applied to an injection device based on a horizontal die-casting machine that injects and fills molten metal such as an aluminum alloy into a mold cavity 14. However, this is not limited to this. For example, the invention may be applied to an injection device based on a vertical low-pressure casting machine, or an injection device based on a semi-solid casting machine that pressurizes and injects a semi-solid metal alloy into the mold cavity. It may also be applied to an injection device of a vacuum casting machine that applies vacuum to the injection sleeve or mold cavity.

100 Die-casting machine 2 Fixed mold 4 Movable mold 6 Mold cavity 10 Injection device 12 Injection sleeve 14 Plunger rod 16 Pouring port 20 Plunger 22 Seal tip portion 24, 27, 28 Sleeve cleaning portion 26 Rod connecting portion 30 Injection driving portion 40 Injection control portion

Claims (4)

An injection device of a die casting machine supplies molten metal into an injection sleeve and injects the molten metal into a mold cavity using a plunger that moves back and forth,
the plunger comprises a seal tip portion that seals against leakage of the molten metal, a sleeve cleaning portion that has a mixture of a plurality of convex portions and a plurality of concave portions and that cleans the inside of the injection sleeve, a rod connecting portion that connects a plunger rod, and an injection drive portion that is connected to the plunger rod and performs a forward and backward movement along the forward and backward direction of the plunger ,
The outer diameter of the protrusion is the same as the outer diameter of the seal tip portion,
The convex portion and the concave portion are a continuous annular protrusion shape and a continuous annular groove shape, and the protrusion shapes and the groove shapes are arranged in parallel in multiple numbers so as to be alternately aligned in the forward/backward direction . 2. The injection device of a die casting machine according to claim 1, wherein the length of each of the convex portion and the concave portion in the advancing/retracting direction is 0.03 to 0.3 times the outer diameter of the seal tip portion. 3. An injection device of a die casting machine according to claim 1, wherein, when the direction approaching the mold cavity in the advancing/retracting direction is defined as the front and the direction away from the mold cavity is defined as the rear, a corner on the front side of the seal tip is rounded, and a corner on the rear side of the seal tip is not rounded. 4. The injection device of a die casting machine according to claim 1 , wherein the injection drive unit further applies a rotational motion to the retraction motion of the plunger.