PLUNGER TIP AND SLIDING METHOD

A plunger tip slides along an inner surface of the plunger sleeve and that injects a molten metal into a mold. The plunger tip includes: a tip main body; a ring-shaped hard resin member that is attached to an outer peripheral surface of the tip main body and that is in contact with the inner surface of the plunger sleeve at least during a hot period in which the plunger tip slides along the inner surface of the plunger sleeve; and a silicone resin member positioned between the tip main body and the ring-shaped hard resin member, in which a radial thickness of the silicone resin member during the hot period is thinner than a radial thickness of the silicone resin member during a cold period in which the molten metal is not supplied in the plunger sleeve.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2020-156841 filed on Sep. 18, 2020, incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a plunger tip and a sliding method.

2. Description of Related Art

A plunger tip used in a die casting machine slides in a plunger sleeve. Thus, lubricity and sealing property are required between the plunger tip and an inner surface of the plunger sleeve. In Japanese Unexamined Patent Application Publication No. 2006-035308 (JP 2006-035308 A), a part of an outer peripheral side surface of a tip main body is covered with a hard resin, and the hard resin comes into contact with an inner surface of a plunger sleeve and thus, lubricity and sealing property are provided between the plunger tip and the inner surface of the plunger sleeve.

SUMMARY

Although the hard resin used for the plunger tip is required to have heat resistance, a hard resin having high heat resistance has a large coefficient of thermal expansion in general. Thus, in JP 2006-035308 A, when it is designed such that the hard resin is in contact with the inner surface of the plunger sleeve in a state in which the molten metal is supplied in the plunger sleeve (in the present disclosure, referred to as “during a cold period” or a “cold period”), the diameter of the hard resin is increased due to thermal expansion when the plunger tip slides in the plunger sleeve to inject the molten metal supplied in the plunger sleeve200into the mold (in the present disclosure, referred to as “during a hot period” or a “hot period”). Thus, the frictional resistance during sliding becomes too large. In contrast, if the size of the diameter of the hard resin is designed in consideration of the thermal expansion of the hard resin during the hot period so that the frictional resistance during sliding does not become too large, there is a possibility that the sealing property of the hard resin and the inner surface of the plunger sleeve during the hot period cannot be sufficiently obtained when the thermal expansion of the hard resin is not as designed, and the like.

The present disclosure has been made to solve such a problem, and the object of the present disclosure is to provide a plunger tip and a sliding method that can further reduce a frictional resistance during sliding while ensuring a sealing property during the hot period.

A plunger tip slides along an inner surface of the plunger sleeve and that injects a molten metal into a mold. The plunger tip includes: a tip main body; a ring-shaped hard resin member that is attached to an outer peripheral surface of the tip main body and that is in contact with the inner surface of the plunger sleeve at least during a hot period in which the plunger tip slides along the inner surface of the plunger sleeve; and a ring-shaped elastic member positioned between the tip main body and the ring-shaped hard resin member, in which a radial thickness of the ring-shaped elastic member during the hot period is thinner than a radial thickness of the ring-shaped elastic member during a cold period in which the molten metal is not supplied in the plunger sleeve.

In a sliding method according to the present disclosure, a plunger tip slides along an inner surface of a plunger sleeve and injects a molten metal into a mold. The plunger tip includes: a tip main body; a ring-shaped hard resin member that is attached to an outer peripheral surface of the tip main body and that is in contact with the inner surface of the plunger sleeve at least during a hot period in which the plunger tip slides along the inner surface of the plunger sleeve; and a ring-shaped elastic member positioned between the tip main body and the silicone resin member, in which a radial thickness of the ring-shaped elastic member during the hot period is thinner than a radial thickness of the ring-shaped elastic member during a cold period in which the molten metal is not supplied in the plunger sleeve.

In the plunger tip according to the present disclosure, since the ring-shaped elastic member becomes thinner during the hot period than during the cold period, even when the diameter of the ring-shaped hard resin member is increased due to thermal expansion, it is possible to suppress the frictional resistance between the inner surface of the plunger sleeve and the ring-shaped hard resin member from being increased. Further, since the ring-shaped hard resin member comes into contact with the inner surface of the plunger sleeve at least during the hot period, it is possible to secure the sealing property during the hot period. This makes it possible to provide the plunger tip that can further reduce the frictional resistance during sliding while ensuring the sealing property during the hot period.

In the sliding method according to the present disclosure, since the ring-shaped elastic member becomes thinner during the hot period than during the cold period, even when the diameter of the ring-shaped hard resin member is increased due to thermal expansion, it is possible to suppress the frictional resistance between the inner surface of the plunger sleeve and the ring-shaped hard resin member from being increased. Further, since the ring-shaped hard resin member comes into contact with the inner surface of the plunger sleeve at least during the hot period, it is possible to secure the sealing property during the hot period. This makes it possible to provide the sliding method that can further reduce the frictional resistance during sliding while ensuring the sealing property during the hot period.

DETAILED DESCRIPTION OF EMBODIMENTS

First Embodiment

Hereinafter, a first embodiment of the present disclosure will be described with reference to the drawings. However, the disclosure is not limited to the following first embodiment. The following description and drawings are simplified as appropriate for the sake of clarity.

FIG. 1is a partial cross-sectional view showing a plunger tip100and a plunger sleeve200according to the first embodiment of the present disclosure. On the left side ofFIG. 1, the plunger tip100and the plunger sleeve200in a state in which a molten metal is not supplied in the plunger sleeve200(hereinafter, referred to as “during a cold period” or “a cold period” in the present specification) is shown. On the right side ofFIG. 1, the plunger tip100and the plunger sleeve200in a state in which the molten metal is supplied in the plunger sleeve200(hereinafter, referred to as “during a hot period” or “a hot period” in the present specification) is shown. The plunger tip100slides along an inner surface of the plunger sleeve200having a cylindrical shape, and injects the molten metal supplied in the plunger sleeve200into a mold. As shown inFIG. 1, the plunger tip100includes a tip main body101, a ring-shaped hard resin member102(hereinafter, simply referred to as a “hard resin member102”), and a ring-shaped silicone resin member103(hereinafter, simply referred to as a “resin member103”) serving as a ring-shaped elastic member.

The tip main body101has a cylindrical shape, and a cooling device can be provided inside the cylindrical shape. Here, the cooling device is, for example, a cooling pipe or the like that serves as a flow path for a refrigerant. When the cooling device is not required, the tip main body101may have a columnar shape instead of a cylindrical shape. The tip main body101is made of heat-resistant tool steel or the like. Further, the tip main body101may be formed of a copper alloy such as beryllium copper.

Further, in at least a part of the outer peripheral surface, the tip main body101has a groove portion101A extending along a circumferential direction in which the hard resin member102and the silicone resin member103can be disposed. The depth of the groove portion101A is determined by the thickness of the hard resin member102and the thickness of the silicone resin member103disposed in the groove portion101A. Specifically, the silicone resin member103and the hard resin member102are disposed in this order in the groove portion101A toward an outer radial side of the tip main body101. The groove portion101A has a depth in which the hard resin member102can come into contact with the inner surface of the plunger sleeve200, at least during the hot period. As a result, the sealing property between the inner surface of the plunger sleeve200and the hard resin member102during the hot period can be ensured. Further, the depth of the groove portion101A may be a depth in which the hard resin member102comes into contact with the inner surface of the plunger sleeve200during the cold period. As a result, the sealing property between the inner surface of the plunger sleeve200and the hard resin member102during the cold period can be more surely ensured. Specifically, the sealing property can be ensured until the thermal expansion of the hard resin member102is completed (in the initial stage of the hot period). Here, “the thermal expansion of the hard resin member102is completed” means that the temperature of the hard resin member102and the ambient temperature become substantially constant, and the amount of thermal expansion of the hard resin member102becomes substantially constant.

Further, the diameter of a part of the tip main body101excluding the groove portion101A is slightly smaller than the inner diameter of the plunger sleeve200. In casting using a die casting machine, the plunger tip100and the plunger sleeve200are thermally expanded by the heat of the molten metal or the like. Therefore, the diameter of the tip main body101is formed to be slightly smaller than the inner diameter of the plunger sleeve200so that the thermal expansion of the tip main body101during the hot period can be allowed. In other words, the diameter of the tip main body101is such that a minute gap is formed between the outer surface of the tip main body101and the inner surface of the plunger sleeve200in a state in which the plunger sleeve200and the tip main body101are thermally expanded. This makes it possible to prevent frictional resistance from being generated between the inner surface of the plunger sleeve200and the outer surface of the plunger tip100when sliding the plunger tip100inside the plunger sleeve200.

The hard resin member102is a ring-shaped member formed of a hard resin having a high heat resistance. Further, the hard resin member102is attached to the inside of the groove portion101A of the tip main body101and on the outer radial side of the tip main body101of the silicone resin member103attached to the groove portion101A.

Further, the hard resin member102has a radial thickness that allows contact with the inner surface of the plunger sleeve200at least during the hot period in which the plunger tip100slides along the inner surface of the plunger sleeve200.

Specifically, during the cold period, that is, in the state in which the silicone resin member103described below is not compressed, the hard resin member102may have a radial thickness so as to provide a slight gap between the inner surface of the plunger sleeve200and the hard resin member102. The slight gap has a size in which the amount of thermal expansion of the hard resin member102during the hot period and the amount of compression of the silicone resin member103described later is taken into consideration. More specifically, the slight gap has a size in which it is possible to prevent the inner surface of the plunger sleeve200and the hard resin member102from coming into contact and prevent an excessive frictional resistance from being generated when the plunger tip100slides along the inner surface of the plunger sleeve200, due to the hard resin member102being thermally expanded by the heat of the molten metal during the hot period and the silicone resin member103being compressed by the thermal expansion of the hard resin member102. As a result, the sealing property during the hot period is ensured, and the frictional resistance between the inner surface of the plunger sleeve200and the hard resin member102when sliding the plunger tip100can be prevented from becoming excessively large.

Alternatively, during the cold period, in the state in which the silicone resin member103described below is not compressed, the hard resin member102may have a radial thickness in which the inner surface of the plunger sleeve200and the hard resin member102come into contact. In this case, it is possible to prevent an excessive frictional resistance from being generated between the inner surface of the plunger sleeve200and the hard resin member102, due to the hard resin member102being thermally expanded and the silicone resin member103being compressed by the thermal expansion of the hard resin member102, during the hot period. Further, since the inner surface of the plunger sleeve200and the hard resin member102are in contact during the cold period, the sealing property can be ensured until the thermal expansion of the hard resin member102is completed (the initial stage of the hot period).

The silicone resin member103is a ring-shaped member formed of a heat-resistant silicone resin. Further, the silicone resin member103is attached to the inside of the groove portion101A of the tip main body101and on the inner radial side of the tip main body101of the hard resin member102attached to the groove portion101A. That is, the silicone resin member103is positioned between the tip main body101and the hard resin member102. Further, the silicone resin member103has, for example, a static shear modulus of 0.2 MPa or more and 1.0 MPa or less. Then, although the silicone resin member103slightly thermally expands during the hot period, the silicone resin member103is actually compressed by being pushed by the thermally expanded hard resin member102. In other words, the radial thickness of the silicone resin member103during the hot period is thinner than the radial thickness of the silicone resin member103during the cold period. Further, during the cold period, the silicone resin member103is not substantially compressed.

Next, a sliding method according to the first embodiment in which a plunger tip100is slid along the inner surface of the plunger sleeve200to inject a molten metal into a mold will be described.

First, as shown on the left side ofFIG. 1, the silicone resin member103is not compressed during the cold period, and the hard resin member102is in contact with the inner surface of the plunger sleeve200.

Next, as shown on the right side ofFIG. 1, the molten metal is supplied in the plunger sleeve200, the molten metal causes the plunger tip100and the plunger sleeve200to thermally expand slightly and the hard resin member102to be thermally expanded significantly, and the silicone resin member103is compressed by the thermally expanded hard resin member102. That is, the radial thickness of the silicone resin member103during the hot period is thinner than the radial thickness of the silicone resin member103during the cold period.

Then, the plunger tip100is slid along the inner surface of the plunger sleeve200to inject the molten metal supplied in the plunger sleeve200into the mold. At this time, while the hard resin member102is thermally expanded, the silicone resin member103is compressed by the amount of thermal expansion of the hard resin member102. Thus, the frictional resistance during sliding does not become excessively large. Further, since the inner surface of the plunger sleeve200and the hard resin member102are already in contact during the cold period, the sealing property can be ensured until the thermal expansion of the hard resin member102is completed (the initial stage of the hot period).

In the plunger tip100and the sliding method according to the first embodiment described above, since the silicone resin member103becomes thinner during the hot period than during the cold period, even when the diameter of the hard resin member102is increased due to thermal expansion, it is possible to suppress the frictional resistance between the inner surface of the plunger sleeve200and the hard resin member102during sliding of the plunger tip100from being increased. Further, since the hard resin member102comes into contact with the inner surface of the plunger sleeve200at least during the hot period, it is possible to secure the sealing property during the hot period. This makes it possible to provide the plunger tip100and the sliding method that can further reduce the frictional resistance during sliding while ensuring the sealing property during the hot period.

Second Embodiment

Next, a plunger tip100A according to a second embodiment of the present disclosure will be described with reference toFIG. 2. The following description and drawings are simplified as appropriate for the sake of clarity.

As shown inFIG. 2, the plunger tip100A according to the second embodiment is different from the plunger tip100according to the first embodiment in that an elastic spring104is provided instead of the silicone resin member103as the ring-shaped elastic member. Thus, in the plunger tip100A according to the second embodiment, the same components as those of the plunger tip100according to the first embodiment are indicated with the same reference numerals, and the description thereof will be omitted.

The elastic spring104is a ring-shaped leaf spring, and the cross-sectional shape of the ring in the radial direction is substantially U-shaped. Further, the elastic spring104is attached to the inside of the groove portion101A of the tip main body101and on the inner radial side of the tip main body101of the hard resin member102attached to the groove portion101A. That is, the elastic spring104is positioned between the tip main body101and the hard resin member102. Further, during the hot period, the elastic spring104contracts by being pushed by the thermally expanded hard resin member102. In other words, the radial thickness of the elastic spring104during the hot period is thinner than the radial thickness of the elastic spring104during the cold period. Also, during the cold period, the elastic spring104is not substantially compressed.

Next, a sliding method according to the second embodiment in which the plunger tip100is slid along the inner surface of the plunger sleeve200to inject the molten metal into the mold will be described.

First, as shown on the left side ofFIG. 2, the elastic spring104is not compressed during the cold period, and the hard resin member102is in contact with the inner surface of the plunger sleeve200.

Next, as shown on the right side ofFIG. 2, the molten metal is supplied in the plunger sleeve200, the molten metal causes the plunger tip100and the plunger sleeve200to thermally expand slightly and the hard resin member102to be thermally expanded significantly, and the elastic spring104pressed by the thermally expanded hard resin member102is shrunk. That is, the radial thickness of the elastic spring104during the hot period is thinner than the radial thickness of the elastic spring104during the cold period.

Then, the plunger tip100is slid along the inner surface of the plunger sleeve200to inject the molten metal supplied in the plunger sleeve200into the mold. At this time, while the hard resin member102is thermally expanded, the elastic spring is shrunk by the amount of thermal expansion of the hard resin member102. Thus, the frictional resistance during sliding does not become excessively large. Further, since the inner surface of the plunger sleeve200and the hard resin member102are already in contact during the cold period, the sealing property can be ensured until the thermal expansion of the hard resin member102is completed (the initial stage of the hot period).

In the plunger tip100and the sliding method according to the second embodiment described above, since the elastic spring104becomes thinner during the hot period than during the cold period, even when the diameter of the hard resin member102is increased due to thermal expansion, it is possible to suppress the frictional resistance between the inner surface of the plunger sleeve200and the hard resin member102during sliding of the plunger tip100from being increased. Further, since the hard resin member102comes into contact with the inner surface of the plunger sleeve200at least during the hot period, it is possible to secure the sealing property during the hot period. This makes it possible to provide the plunger tip100A and the sliding method that can further reduce the frictional resistance during sliding while ensuring the sealing property during the hot period.

The present disclosure is not limited to the above embodiments, and can be appropriately modified without departing from the spirit thereof.