PLUNGER TIP, INJECTION DEVICE, AND INJECTION METHOD

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2020-003651 filed on Jan. 14, 2020, incorporated herein by reference in its entirety.

BACKGROUND
1. Technical Field

The disclosure relates to a plunger tip, an injection device, and an injection method.

2. Description of Related Art

A die casting apparatus is equipped with an injection device that injects a molten metal to fill in a metal mold with the molten metal. The injection device includes a cylindrical plunger sleeve, a plunger tip that is slidably installed in the plunger sleeve, and a plunger rod that causes the plunger tip to slide.

Here, in order to improve injection performance, it is required for the injection device to minimize friction between the plunger tip and the plunger sleeve so as to allow the plunger tip to slide smoothly.

A technique related to the injection device is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2016-68106 (JP 2016-68106 A). The injection device disclosed in JP 2016-68106 A promotes cooling of the molten metal after the molten metal is injected into the metal mold by causing coolant to flow inside the plunger tip. Further, in the injection device above, the coolant is used to sufficiently cool an outer peripheral surface near a tip end surface of the plunger tip to suppress occurrence of friction caused by contact between the outer peripheral surface near the tip end surface of the plunger tip and an inner peripheral surface of the plunger sleeve.

SUMMARY

In the injection device disclosed in JP 2016-68106 A, cooling of the molten metal needs to be started using the coolant in the plunger tip at a relatively late timing such that the molten metal stored in the in the injection device is not solidified before being injected into the metal mold. However, by the time when cooling of the molten metal is started at such a timing, the molten metal has already entered a gap between the outer peripheral surface of the tip end of the plunger tip and the plunger sleeve. Therefore, burrs are created in the gap between the outer peripheral surface of the tip end of the plunger tip and the plunger sleeve as the molten metal that has entered the gap is solidified. Thus, in the injection device, friction between the plunger tip and plunger sleeve is increased as being influenced by the burrs, which disables smooth sliding of the plunger tip. Therefore, there may be a case where injection performance deteriorates.

The disclosure provides a plunger tip, an injection device, and an injection method capable of improving injection performance by suppressing creation of burrs.

A first aspect of the disclosure relates to a plunger tip. The plunger tip includes a main body of the plunger tip. In the plunger tip, a first cooling chamber is provided at a central region of a tip end of the main body of the plunger tip inside the main body of the plunger tip, and a second cooling chamber is provided inside the main body of the plunger tip along an outer peripheral surface of the tip end. The second cooling chamber is configured such that a cooling medium flows in the second cooling chamber in priority to the first cooling chamber.

According to the first aspect, the molten metal in proximity to the entrance of the gap between the outer peripheral surface of the tip end of the plunger tip and the plunger sleeve can be solidified using the second cooling chamber before the molten metal enters the gap. Therefore, creation of burrs between the plunger tip and the plunger sleeve can be suppressed. With this configuration, friction between the plunger tip and the plunger sleeve is reduced, which enables smooth sliding of the plunger tip. Accordingly, injection performance is improved.

In the first aspect, the second cooling chamber may be configured such that the cooling medium flows at a timing earlier than a timing of the first cooling chamber.

In the aspect above, the second cooling chamber may be configured independently of the first cooling chamber and configured such that the cooling medium different from a cooling medium flowing in the first cooling chamber flows in the second cooling chamber.

With the configuration above, the molten metal in proximity to the entrance of the gap between the outer peripheral surface of the tip end of the plunger tip and the plunger sleeve can be solidified using the second cooling chamber before the molten metal enters the gap. Therefore, creation of burrs between the plunger tip and the plunger sleeve can be suppressed. With this configuration, friction between the plunger tip and the plunger sleeve is reduced, which enables smooth sliding of the plunger tip. Accordingly, injection performance is improved.

In the aspect above, the cooling medium to flow in the second cooling chamber of the plunger tip may be liquid nitrogen. With the configuration above, the molten metal in proximity to the entrance of the gap can be solidified more quickly than when coolant is used.

In the aspect above, the outer peripheral surface of the tip end of the plunger tip may include a stepped shape. With this configuration, the molten metal can be solidified quickly at a stepped portion in proximity to the entrance of the gap between the outer peripheral surface of the tip end of the plunger tip and the plunger sleeve before the molten metal enters and reaches the depth of the gap.

A second aspect of the disclosure relates to an injection device. The injection device includes a plunger sleeve having a cylindrical shape; the plunger tip according to the aspect above, the plunger tip being configured so as to be slidable in a cylinder of the plunger sleeve; and a plunger rod that causes the plunger tip to slide in the cylinder of the plunger sleeve.

According to the second aspect, the molten metal in proximity to the entrance of the gap between the outer peripheral surface of the tip end of the plunger tip and the plunger sleeve can be solidified using the second cooling chamber before the molten metal enters the gap. Therefore, creation of burrs between the plunger tip and the plunger sleeve can be suppressed. With this configuration, friction between the plunger tip and the plunger sleeve is reduced, which enables smooth sliding of the plunger tip. Accordingly, injection performance is improved.

According to the second aspect, the plunger tip may be configured so as to be rotatable about an axial direction as a rotation axis. With the configuration above, a high temperature portion of the plunger tip that is immersed in the molten metal is switched with a low temperature portion that is not immersed in the molten metal. Therefore, the molten metal in proximity to the entrance of the gap between the outer peripheral surface of the tip end of the plunger tip and the plunger sleeve can be solidified more quickly using the low temperature portion.

A third aspect of the disclosure relates to an injection method of an injection device. The injection device includes a plunger sleeve having a cylindrical shape, a plunger tip configured to be slidable in a cylinder of the plunger sleeve and including a main body of the plunger tip, and a plunger rod causing the plunger tip to slide in the cylinder of the plunger sleeve. A first cooling chamber is provided in a central region of a tip end of the main body of the plunger tip. A second cooling chamber is provided along an outer peripheral surface of the tip end inside the main body of the plunger tip. The injection method includes: causing a cooling medium to flow in the second cooling chamber in priority to the first cooling chamber; supplying molten metal into the cylinder of the plunger sleeve; and injecting the molten metal by causing the plunger tip to slide using the plunger rod while the cooling medium is caused to flow in the first cooling chamber.

According to the third aspect, the molten metal in proximity to the entrance of the gap between the outer peripheral surface of the tip end of the plunger tip and the plunger sleeve can be solidified using the second cooling chamber before the molten metal enters the gap. Therefore, creation of burrs between the plunger tip and the plunger sleeve can be suppressed. With this configuration, friction between the plunger tip and the plunger sleeve is reduced, which enables smooth sliding of the plunger tip. Accordingly, injection performance is improved.

According to the third aspect, the cooling medium may be caused to flow in the second cooling chamber before the molten metal is supplied into the cylinder of the plunger sleeve.

According to the aspects of the disclosure, the disclosure can provide the plunger tip, the injection device, and the injection method capable of improving injection performance by suppressing creation of burrs.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein:

FIG. 1 is a schematic sectional view showing a part of an injection device according to a first embodiment;

FIG. 2 is a schematic sectional view of a part of the injection device shown in FIG. 1 as seen from the front;

FIG. 3 is a diagram for explaining an operation of the injection device according to the first embodiment;

FIG. 4 is a diagram for explaining the operation of the injection device according to the first embodiment;

FIG. 5 is a diagram for explaining the operation of the injection device according to the first embodiment;

FIG. 6 is a diagram for explaining the operation of the injection device according to the first embodiment;

FIG. 7 is a diagram for explaining the operation of the injection device according to the first embodiment;

FIG. 8 is a schematic sectional view showing a part of an injection device according to a second embodiment; and

FIG. 9 is a schematic sectional view showing a part of an injection device according to a third embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, specific embodiments to which the disclosure is applied will be described in detail with reference to the drawings. However, the disclosure is not limited to the following embodiments. Further, the following description and drawings are simplified as appropriate for the sake of clarity.

First Embodiment

FIG. 1 is a schematic sectional view showing a part of an injection device 1 according to a first embodiment. The injection device 1 shown in FIG. 1 is a device that is mounted on a die casting apparatus and injects a molten metal such as aluminum accumulated in the injection device 1 into a metal mold to fill in the metal mold with the molten metal.

Specifically, the injection device 1 includes at least a plunger sleeve 11 having a cylindrical shape, a plunger tip 12, and a plunger rod 13. The plunger tip 12 is slidably installed in a cylinder of the plunger sleeve 11. The plunger rod 13 causes the plunger tip 12 to slide in the cylinder of the plunger sleeve 11.

The injection device 1 is installed such that the plunger sleeve 11 and a sprue sleeve 71 provided in a metal mold 70 communicate with each other. In the metal mold 70, a mold sprue 72 is provided in a cylinder of the sprue sleeve 71. The mold sprue 72 is provided at a position facing a forward direction of the plunger tip 12 that is slidably installed in the plunger sleeve 11. A runner 73 is provided between the sprue sleeve 71 and the mold sprue 72. Further, a gate 74 (not shown) and a cavity 75 (not shown) are provided at a tip end of the runner 73.

For example, in the injection device 1, when the plunger tip 12 is moved backward (that is, the plunger tip 12 is slid in a negative direction of an X-axis), the molten metal is supplied into the cylinder of the plunger sleeve 11 through a molten metal supply port 111 that is provided in an upper portion of the plunger sleeve 11. As a result, the molten metal is accumulated in a hollow portion 60. The hollow portion 60 is a space surrounded by the plunger sleeve 11, the plunger tip 12, and the sprue sleeve 71 and the mold sprue 72 of the metal mold 70. Thereafter, the injection device 1 applies a pressure of an injection cylinder (not shown) to the plunger tip 12 via the plunger rod 13 to move the plunger tip 12 forward (that is, to cause the plunger tip 12 to slide in a positive direction of the X-axis). Consequently, the molten metal accumulated in the hollow portion 60 is filled in the cavity 75 via the sprue sleeve 71, the mold sprue 72, the runner 73, and the gate 74 of the metal mold 70.

Subsequently, a cooling mechanism of the injection device 1 will be described with reference to FIG. 2 in addition to FIG. 1. FIG. 2 is a schematic sectional view of the plunger tip 12 provided in the injection device 1 as seen from the front. Note that FIG. 2 is a schematic sectional view of a portion cut along II-IP in FIG. 1.

As shown in FIGS. 1 and 2, a first cooling chamber 121 is provided inside a main body of the plunger tip 12 in the central region of the tip end of the plunger tip 12 (the end on the side facing the mold sprue 72). A second cooling chamber 122 is provided inside the main body of the plunger tip 12 along an outer peripheral surface of a tip end of the plunger tip 12 (a portion close to the inner peripheral surface of the plunger sleeve 11). The second cooling chamber 122 has an annular shape so as to surround the first cooling chamber 121 when viewed in a front view (that is, when viewed from an x-axis direction).

Further, a coolant supply path 121a is provided in the plunger tip 12 from a rear end of the plunger tip 12 (an end on the side of the plunger tip 12 connected to the plunger rod 13) to the first cooling chamber 121, and a coolant discharge path 121b extends from the first cooling chamber 121 to the rear end of the plunger tip 12.

Further, the coolant supply path 122a is provided in the plunger tip 12 from the rear end of the plunger tip 12 to the second cooling chamber 122, and the coolant discharge path 122b extends from the second cooling chamber 122 to the rear end of the plunger tip 12.

In the plunger rod 13, a coolant supply path 131a, a coolant discharge path 131b, a coolant supply path 132a, and a coolant discharge path 132b are provided to extend from one end (an end connected to the plunger tip 12) to the other end (an end connected to the injection cylinder (not shown)).

The plunger tip 12 is connected to the one end of the plunger rod 13 such that the coolant supply path 121a and the coolant supply path 131a communicate with each other, the coolant discharge path 121b and the coolant discharge path 131b communicate with each other, the coolant supply path 122a and the coolant supply path 132a communicate with each other, and the coolant discharge path 122b and the coolant discharge path 132b communicate with each other. An injection cylinder 14 (not shown) is connected to the other end of the plunger rod 13, and a coolant supply source 15 and a coolant discharge port 16 (both not shown) are provided at the other end of the plunger rod 13.

A cooling medium M1 such as coolant discharged from the coolant supply source 15 is supplied to the first cooling chamber 121 via the coolant supply path 131a and the coolant supply path 121a. The cooling medium M1 supplied to the first cooling chamber 121 is then discharged from the coolant discharge port 16 via the coolant discharge path 121b and the coolant discharge path 131b.

A cooling medium M2 such as coolant discharged from the coolant supply source 15 is supplied to the second cooling chamber 122 via the coolant supply path 132a and the coolant supply path 122a. The cooling medium M2 supplied to the second cooling chamber 122 is then discharged from the coolant discharge port 16 via the coolant discharge path 122b and the coolant discharge path 132b.

Here, the second cooling chamber 122 is provided independently of the first cooling chamber 121, and the cooling medium M2 different from the cooling medium M1 that flows in the first cooling chamber 121 flows in the second cooling chamber 122. Therefore, in the injection device 1, a timing of causing the cooling medium M1 to flow in the first cooling chamber 121 and a timing of causing the cooling medium M2 to flow in the second cooling chamber 122 can be freely set.

In the injection device 1, the cooling medium M1 flows in the first cooling chamber 121 so as to cool the molten metal accumulated in the hollow portion 60 to such an extent that the molten metal is not solidified, thereby cooling of the injected molten metal filled in the cavity of the metal mold 70 can be promoted. Further, after that, detachability between the plunger tip 12 and a biscuit produced by solidifying the molten metal can be improved.

However, in the injection device 1, cooling of the molten metal using the first cooling chamber 121 needs to be started at a relatively late timing in order to suppress that the molten metal accumulated in the hollow portion 60 is solidified in the hollow portion 60 before being injected into the cavity of the metal mold 70.

However, there is a possibility that, by the time when cooling of the molten metal is started at such a timing, the molten metal has already entered a gap between the outer peripheral surface of the tip end of the plunger tip 12 and the plunger sleeve 11. Therefore, there is also a possibility that burrs are created in the gap between the outer peripheral surface of the tip end of the plunger tip 12 and the plunger sleeve 11 as the molten metal that has entered the gap is solidified. Thus, friction between the plunger tip 12 and plunger sleeve 11 is increased as being influenced by the burrs, which disables smooth sliding of the plunger tip 12. Therefore, there may be a case where injection performance deteriorates.

Accordingly, in the injection device 1, the cooling medium M2 is caused to flow in the second cooling chamber 122 before causing the cooling medium M1 to flow in the first cooling chamber 121 such that the molten metal in proximity to an entrance of the gap between the outer peripheral surface of the tip end of the plunger tip 12 and the plunger sleeve 11 is solidified before the molten metal enters the gap. With this configuration, in the injection device 1, creation of burrs between the outer peripheral surface of the tip end of the plunger tip 12 and the plunger sleeve 11 can be suppressed, which enables smooth sliding of the plunger tip 12. Accordingly, the injection performance can be improved.

Next, operations of the injection device 1 will be described with reference to FIGS. 3 to 7. FIGS. 3 to 7 are diagrams for explaining the operations of the injection device 1. Note that, FIG. 5 is an enlarged view of an area A in FIG. 4.

First, as shown in FIG. 3, the plunger tip 12 is moved backward. That is, the plunger tip 12 is slid in the negative direction of the X-axis.

After that, as shown in FIG. 4, molten metal 50 is supplied into the cylinder of the plunger sleeve 11 from the molten metal supply port 111 of the plunger sleeve 11. Consequently, the molten metal 50 is accumulated in the hollow portion 60 (a space surrounded by the plunger sleeve 11, the plunger tip 12, and the sprue sleeve 71 and the mold sprue 72 of the metal mold 70).

At this time, the cooling medium M2 is caused to flow in the second cooling chamber 122. With this configuration, the molten metal 50 in proximity to the entrance of the gap between the outer peripheral surface of the tip end of the plunger sleeve 11 and the plunger tip 12 can be solidified before the molten metal 50 enters the gap (see FIG. 5). With a solidified metal 51 described above, creation of burrs between the outer peripheral surface of the tip end of the plunger tip 12 and the plunger sleeve 11 can be suppressed in the injection device 1.

Note that, the timing of causing the cooling medium M2 to flow in the second cooling chamber 122 (that is, the timing of starting cooling of the molten metal 50 using the second cooling chamber 122) is preferably prior to supply of the molten metal 50 into the hollow portion 60. However, the timing of causing the cooling medium M2 to flow may be after the molten metal 50 is supplied to the hollow portion 60 as long as the timing occurs before the molten metal 50 enters the gap between the plunger sleeve 11 and the plunger tip 12.

After that, as shown in FIG. 6, the plunger tip 12 is moved forward. Accordingly, the volume of the hollow portion 60 is reduced, and the hollow portion 60 is filled with the molten metal 50. Even at this time, the cooling medium M2 is continuously caused to flow in the second cooling chamber 122. With this configuration, even in a portion of the gap that is to be newly immersed in the molten metal 50 due to rising of a surface of the molten metal 50 in the hollow portion 60, only the molten metal 50 in proximity to an entrance of the portion of the gap can be solidified before the molten metal 50 enters the portion of the gap. Consequently, in the injection device 1, creation of burrs (e.g. so called gap burrs and wedge burrs) that is caused by the molten metal entering the gap between the outer peripheral surface of the tip end of the plunger tip 12 and the plunger sleeve 11 and that increases a sliding resistance can be suppressed.

After that, as shown in FIG. 7, the plunger tip 12 is moved further forward at a high pressure while causing the cooling medium M1 to flow in the first cooling chamber 121. The forward movement of the plunger tip 12 shown in FIG. 6 and the further forward movement of the plunger tip 12 shown in FIG. 7 may be performed stepwise or continuously. With the movement above, the molten metal 50 in the hollow portion 60 is injected into and filled in the cavity 75 (not shown) in the metal mold 70 via the sprue sleeve 71, the mold sprue 72, the runner 73, and the gate 74 (not shown).

In the injection device 1, the cooling medium M1 flows in the first cooling chamber 121 so as to cool the molten metal 50 accumulated in the hollow portion 60 to such an extent that the molten metal 50 is not solidified, thereby cooling of the injected molten metal 50 filled in the cavity of the metal mold 70 can be promoted. Further, after that, detachability between the plunger tip 12 and a biscuit produced by solidifying the molten metal 50 can be improved.

After the product is produced using the metal mold 70, the processes described in FIGS. 3 to 7 are repeated.

As described above, the injection device 1 according to the first embodiment further includes, inside the plunger tip 12, the second cooling chamber 122 provided along the outer peripheral surface of the plunger tip 12 in addition to the first cooling chamber 121 for promoting solidification of the molten metal after being filled into the cavity. Therefore, in the injection device 1, the cooling medium M2 is caused to flow in the second cooling chamber 122 before causing the cooling medium M1 to flow in the first cooling chamber 121 such that the molten metal in proximity to the entrance of the gap between the outer peripheral surface of the tip end of the plunger tip 12 and the plunger sleeve 11 is solidified before the molten metal enters the gap. With this configuration, in the injection device 1, creation of burrs between the outer peripheral surface of the tip end of the plunger tip 12 and the plunger sleeve 11 can be suppressed, which enables smooth sliding of the plunger tip 12. Accordingly, the injection performance can be improved.

In the first embodiment, the case where the second cooling chamber 122 is configured independently of the first cooling chamber 121 and is configured such that the cooling medium M2 different from the cooling medium M1 flowing in the first cooling chamber 121 flows in the second cooling chamber 122 is described. However, the disclosure is not limited to this. For example, even when the second cooling chamber 122 is not independent of the first cooling chamber 121, the second cooling chamber 122 may only be provided along the outer periphery of the tip end inside the main body of plunger tip such that the cooling medium flows in the second cooling chamber 122 in priority to the first cooling chamber 121 (for example, at an earlier timing).

Second Embodiment

FIG. 8 is a schematic sectional view showing a part of an injection device 2 according to a second embodiment. Compared with the injection device 1, the injection device 2 shown in FIG. 8 further includes a stepped shape 123 on the outer peripheral surface of the tip end of the plunger tip 12.

With this configuration, in the injection device 2, the molten metal 50 at a stepped portion in proximity to the entrance of the gap between the outer peripheral surface of the tip end of the plunger tip 12 and the plunger sleeve 11 can be solidified quickly before the molten metal 50 enters and reaches the depth of the gap.

Structures and operations of the injection device 2 other than the above are the same as those of the injection device 1, and thus the description thereof is omitted.

Third Embodiment

FIG. 9 is a schematic sectional view showing a part of an injection device 3 according to a third embodiment. In the injection device 3 shown in FIG. 9, compared to the injection device 2, the plunger tip 12 is further configured to be rotatable about an axial direction (X-axis direction) as a rotation axis.

In the injection device 3, as the plunger tip 12 is rotated, a high temperature portion of the plunger tip 12 that is immersed in the molten metal 50 is switched with a low temperature portion that is not immersed in the molten metal 50. Therefore, the molten metal 50 in proximity to the entrance of the gap between the outer peripheral surface of the tip end of the plunger tip 12 and the plunger sleeve 11 can be solidified more quickly using the low temperature portion.

Structures and operations of the injection device 3 other than above are the same as those of the injection device 2, and thus the description thereof is omitted.

In the third embodiment, the case has been described as an example where the plunger tip 12 provided in the injection device 2 is configured to be rotatable about the axial direction as the rotation axis, but the disclosure is not limited to this. Needless to say, the plunger tip 12 provided in the injection device 1 may be configured to be rotatable about the axial direction as the rotation axis.

In the first to third embodiments, the case where both the cooling media M1, M2 are coolant has been described as an example, but the disclosure is not limited to this. The cooling media M1, M2 may be, for example, liquid nitrogen. With this configuration, the molten metal 50 in proximity to the entrance of the gap between the outer peripheral surface of the tip end of the plunger tip 12 and the plunger sleeve 11 can be solidified more quickly. Further, the cooling media M1, M2 may be different types of cooling media from each other.

PLUNGER TIP, INJECTION DEVICE, AND INJECTION METHOD

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