JP7697391B2 - Plunger tip for die casting and die casting device - Google Patents

Description

This disclosure relates to a plunger tip for die casting and a die casting device.

Conventionally, in die casting machines, in order to extrude molten metal at high speed and high pressure, it is necessary to move the plunger tip at high speed within the injection sleeve. When the plunger tip is moved at high speed, the supply of lubricant to the sliding surface between the plunger tip and the injection sleeve becomes insufficient, causing an increase in sliding resistance and causing the operation to stop. The plunger tip described in Patent Document 1 prevents a decrease in sliding properties by providing a layer of molybdenum as a solid lubricant on part of the outer circumferential surface of the plunger tip.

JP 2001-347355 A

However, the plunger tip described in Patent Document 1 has a problem in that the heat resistance of molybdenum is low, and therefore the sliding properties decrease in a high-temperature environment where it comes into contact with molten metal.

The present disclosure can be realized in the following forms.
According to one embodiment of the present disclosure, there is provided a plunger tip for die casting, which is used by sliding and reciprocating in an injection sleeve to which a powder lubricant containing graphite is applied, comprising a tip body and a cast iron ring attached to the outer periphery of the tip body, having an outer diameter larger than that of the tip body, and forming a sliding surface with the injection sleeve, the average particle diameter of the graphite contained in the spheroidal graphite cast iron forming the cast iron ring is larger than the average particle diameter of the powder lubricant, the cast iron ring has a groove on its outer periphery, the groove is formed linearly, and the longitudinal direction of the groove is formed in a twisted position with respect to the central axis of the cast iron ring, one end of the groove reaches one of both end faces in the central axis direction of the cast iron ring that is farther from the cavity in the reciprocating direction of the plunger tip, and the other end does not reach any end face of the cast iron ring.

(1) According to one embodiment of the present disclosure, there is provided a plunger tip for die casting, which is used by sliding back and forth within an injection sleeve to which a powder lubricant has been applied, and which includes a tip body and a cast iron ring attached to the outer periphery of the tip body and forming a sliding surface with the injection sleeve, and the average particle size of graphite contained in the cast iron forming the cast iron ring is larger than the average particle size of the powder lubricant.
According to the plunger tip of this embodiment, since the cast iron ring is made of cast iron, the deterioration of heat resistance can be suppressed. Also, since the average particle size of the graphite contained in the cast iron forming the cast iron ring is larger than the average particle size of the powder lubricant applied to the inside of the injection sleeve, the powder lubricant can easily be retained on the surface of the cast iron ring by entering the voids generated when the graphite falls off the surface of the cast iron ring, and the deterioration of the sliding property of the plunger tip can be suppressed.
(2) In the above embodiment, the cast iron ring may have a groove on its outer circumferential surface.
According to this form of plunger tip, a groove is provided on the outer peripheral surface of the cast iron ring, so that on the return path (path away from the cavity), the powder lubricant is more easily supplied to the sliding surface along the groove, thereby further suppressing deterioration of the sliding properties of the plunger tip.
(3) In the above embodiment, the groove may be formed linearly, and the longitudinal direction of the groove may be formed in a twisted position with respect to the central axis of the cast iron ring.
According to this form of plunger tip, the longitudinal direction of the groove is twisted with respect to the central axis of the cast iron ring, so that the powder lubricant held in the groove can be prevented from flowing out of the groove on the way thereto (the way to the cavity). This makes it easier for the powder lubricant to be continuously supplied to the sliding surface, so that the deterioration of the sliding property of the plunger tip can be further prevented.
(4) In the above embodiment, the groove is formed linearly, and one end of the groove reaches one of the end faces in the central axial direction of the cast iron ring that is farther from the cavity in the reciprocating direction of the plunger tip, and the other end does not necessarily reach either end face of the cast iron ring.
According to this form of plunger tip, one end of the groove reaches the end face of the cast iron ring farther from the cavity, and the other end does not reach either end face of the cast iron ring, so that even if the powder lubricant is supplied to the groove from one end of the groove on the return path, the powder lubricant supplied to the groove can be prevented from passing through the groove and being mixed into the molten metal, thereby preventing deterioration of the quality of the die cast product.
(5) In the above embodiment, a plurality of the cast iron rings may be arranged side by side in the reciprocating direction of the plunger tip.
With this type of plunger tip, only the worn parts of the multiple cast iron rings (mainly the ring closest to the cavity) can be replaced and use can continue, thereby reducing the cost of replacing parts due to wear on the plunger tip.
(6) In the above embodiment, the plurality of cast iron rings may be formed from the same material.
With this form of plunger tip, the multiple cast iron rings are formed from the same material, so they have the same thermal expansion coefficient, which makes it possible to suppress differences in dimensional change due to temperature increase between each cast iron ring, and also to suppress deterioration of the sliding properties of the plunger tip due to differences in dimensional change between each cast iron ring.
(7) In the above embodiment, a plurality of cast iron rings may be provided that are arranged in a line in the reciprocating direction of the plunger tip, and among the plurality of cast iron rings, the cast iron ring that is closest to the cavity in the reciprocating direction of the plunger tip may have the groove on its outer peripheral surface.
With this form of plunger tip, it becomes easier to supply powder lubricant to the sliding surface of the cast iron ring that is closest to the cavity in the reciprocating direction of the plunger tip, which is prone to have high sliding resistance, thereby suppressing deterioration of the sliding performance of the plunger tip.
(8) In the above embodiment, the average particle size of the graphite contained in the cast iron forming the cast iron ring may be 1.5 times or more the average particle size of the powder lubricant.
According to this form of plunger tip, the average particle size of the graphite contained in the cast iron forming the cast iron ring is 1.5 times or more the average particle size of the powder lubricant applied inside the injection sleeve, so that the powder lubricant is more easily retained on the surface of the cast iron ring, thereby further suppressing the deterioration of the sliding properties of the plunger tip.
(9) In the above embodiment, the average particle size of graphite contained in the cast iron forming the cast iron ring may be 30 μm or more.
According to this form of plunger tip, the average particle size of the graphite contained in the cast iron forming the cast iron ring is 30 μm or more, so that powder lubricant having an average particle size smaller than 30 μm is easily retained on the surface of the cast iron ring, thereby suppressing a decrease in the sliding properties of the plunger tip.

FIG. 1 is an explanatory diagram showing a die casting apparatus to which a plunger tip for die casting according to an embodiment of the present invention is applied. FIG. 2 is an exploded view of the plunger tip of the present embodiment. FIG. 2 is an external perspective view of the cast iron ring of the present embodiment. FIG. 13 is a diagram showing a sample for a performance evaluation test. FIG. 13 is a diagram showing the results of a performance evaluation test.

A. Embodiments:
FIG. 1 is an explanatory diagram showing a die casting apparatus 1000 to which a plunger tip 100 for die casting of this embodiment is applied. The die casting apparatus 1000 transmits a driving force generated by a driving device (not shown) to the plunger tip 100 via a plunger rod 200, and reciprocates the plunger tip 100 in an injection sleeve 300. During reciprocation, sliding resistance occurs between the plunger tip 100 and the injection sleeve 300. A powder lubricant having high heat resistance is applied to the inner peripheral surface of the injection sleeve 300, and the powder lubricant is supplied between the plunger tip 100 and the injection sleeve 300, thereby suppressing the sliding resistance. In this embodiment, a powder lubricant containing graphite as a main component is used. By driving the plunger tip 100 in this way, the die casting apparatus 1000 extrudes the molten metal filled inside the injection sleeve 300, and fills the molten metal into the cavity 10 formed by the fixed mold 400 and the movable mold 500. In the following description, the path of the plunger tip 100 approaching the cavity 10 during reciprocating motion is also referred to as the "outgoing path," and the path of the plunger tip 100 moving away from the cavity 10 is also referred to as the "returning path."

Figure 2 is an exploded view of the plunger tip 100 of this embodiment. The plunger tip 100 includes a tip body 110 and cast iron rings 121 and 122. The tip body 110, the cast iron ring 121, and the cast iron ring 122 are combined so that their respective central axes coincide with each other to form the central axis L of the plunger tip 100. The tip body 110 is formed of body members 111 to 113. In this embodiment, the body members 111 to 113 are formed of SKD61 material. The body members 111 to 113 each include a screw portion C and are formed so that they can be screwed together. In addition, the outer diameter of the screw portion C is smaller than the outer diameter of the other portions.

The cast iron rings 121 and 122 have a ring shape and are attached to the outer periphery of the screw-in portion C of the main body members 112 and 113, respectively. The cast iron rings 121 and 122 are held in the tip body 110 by the fastening force when the main body members 111 to 113 are screwed together. The outer diameter of the cast iron rings 121 and 122 is larger than the outer diameter of the tip body 110. When the cast iron rings 121 and 122 are combined with the tip body 110, the outer peripheral surfaces of the cast iron rings 121 and 122 protrude from the outer peripheral surface of the tip body 110 when viewed in the direction of the central axis L of the plunger tip 100. Therefore, when the plunger tip 100 slides inside the injection sleeve 300, the outer peripheral surfaces of the cast iron rings 121 and 122 form a sliding surface with the injection sleeve 300.

In this embodiment, the cast iron rings 121 and 122 are formed from cast iron with a graphite spheroidization rate of 80%. The average particle size of the spheroidal graphite contained in the cast iron is controlled by changing the manufacturing conditions such as the cooling rate so that it is larger than the average particle size of the powder lubricant used. The average particle size of the spheroidal graphite contained in the cast iron is preferably about 1.5 to 2 times the average particle size of the powder lubricant used. In this embodiment, the average particle size of the spheroidal graphite contained in the cast iron forming the cast iron rings 121 and 122 is 30 μm. The spheroidal graphite contained in the cast iron falls off the surface of the cast iron rings 121 and 122 due to the sliding resistance with the injection sleeve 300, and forms voids on the surface of the cast iron rings 121 and 122. By entering the voids formed in this way, the powder lubricant smaller than the voids becomes more likely to be held on the surface of the cast iron rings 121 and 122, and the deterioration of the sliding properties of the plunger tip 100 can be suppressed.

3 is an external perspective view of the cast iron ring 121. The cast iron ring 121, which is the cast iron ring arranged closer to the cavity 10 in the reciprocating direction of the plunger tip 100, of the cast iron rings 121 and 122, has multiple grooves G on its outer circumferential surface. The grooves G are formed linearly so that the longitudinal direction is in a twisted position with respect to the central axis M of the cast iron ring 121. By forming the grooves G in this way, the powder lubricant is easily supplied to the sliding surface between the injection sleeve 300 and the cast iron ring 121 along the grooves G on the return path, so that the deterioration of the sliding properties of the plunger tip 100 can be suppressed. In addition, the outflow of the powder lubricant held in the grooves G from the grooves G on the outward path is suppressed, and the powder lubricant is easily continuously supplied to the sliding surface, so that the deterioration of the sliding properties of the plunger tip 100 can also be suppressed.

One end of the groove G reaches one of the two end faces of the cast iron ring 121 in the direction of the central axis L, but the other end of the groove G does not reach either end face of the cast iron ring 121. The cast iron ring 121 is combined with the tip body 110 so that the end face on the side where the end of the groove G reaches becomes the end face farther from the cavity 10 in the reciprocating direction of the plunger tip 100 when combined with the tip body 110. By combining the tip body 110 and the cast iron ring 121 in this way, even if powder lubricant is supplied to the groove G from one end of the groove G on the return path, the other end does not reach either end face of the cast iron ring 121, so that the powder lubricant supplied to the groove G can be prevented from passing through the groove G and being mixed into the molten metal, and deterioration of the quality of the die cast product can be prevented.

Figure 4 is a diagram showing samples for a performance evaluation test. As shown in Figure 4, plunger tips of samples 1 to 4 were created for the performance evaluation test. The ring of the plunger tip of sample 1, which forms the sliding surface with the injection sleeve 300, is made of SKD61 material, which is the same material as the tip body 110 of this embodiment. The ring of the plunger tip of sample 2 is made of cast iron containing spheroidal graphite with an average particle size of 10 μm. The ring of the plunger tip of sample 3 is made of cast iron containing spheroidal graphite with an average particle size of 30 μm. The ring of the plunger tip 100 of sample 4 is made of cast iron containing spheroidal graphite with an average particle size of 30 μm, and a groove G is formed on the outer circumferential surface of the ring. The graphite spheroidization rate of the cast iron forming the ring of each sample is 80%.

Figure 5 shows the results of the performance evaluation test. The average particle size of the powder lubricant used in the performance evaluation test was greater than 10 μm and smaller than 30 μm. In Figure 5, the horizontal axis indicates the number of reciprocations of the plunger tip, and the vertical axis indicates the sliding resistance between the plunger tip and the injection sleeve 300. Figure 5 shows the change in sliding resistance with increasing number of reciprocations for each sample.

In FIG. 5, sample 1 shows a rapid increase in sliding resistance after fewer cycles compared to the other samples. Sample 2, which has a ring made of cast iron with an average particle size of 10 μm, which is smaller than the average particle size of the powder lubricant, shows a greater number of cycles before the sliding resistance starts to increase compared to sample 1. Sample 3, which has a ring made of cast iron with an average particle size of 30 μm, which is larger than the average particle size of the powder lubricant, shows an even greater number of cycles before the sliding resistance starts to increase compared to sample 2. Furthermore, sample 4, which has grooves G on the outer circumferential surface, shows a more suppressed rate of increase in sliding resistance with an increase in the number of cycles compared to sample 3.

According to the plunger tip 100 in the embodiment described above, since the cast iron rings 121, 122 are formed from cast iron, it is possible to suppress a decrease in heat resistance. In addition, since the average particle size of the graphite contained in the cast iron forming the cast iron rings 121, 122 is larger than the average particle size of the powder lubricant, the powder lubricant enters the voids generated when the graphite falls off the surface of the cast iron ring 121, making it easier for the powder lubricant to be retained on the surface of the cast iron rings 121, 122, and thus it is possible to suppress a decrease in the sliding properties of the plunger tip 100.

In addition, the plunger tip 100 has a groove G on the outer peripheral surface of the cast iron ring 121, which makes it easier for the powder lubricant to be supplied to the sliding surface along the groove G on the return path, thereby further suppressing deterioration of the sliding properties of the plunger tip 100.

In addition, the longitudinal direction of the groove G is twisted relative to the central axis L of the cast iron ring 121, so that the powder lubricant held in the groove G can be prevented from flowing out of the groove G during the forward movement. This makes it easier for the powder lubricant to be continuously supplied to the sliding surface, so that the deterioration of the sliding properties of the plunger tip 100 can be further prevented.

In addition, one end of the groove G reaches the end face of the cast iron ring 121 farther from the cavity 10, and the other end does not reach either end face of the cast iron ring 121. Therefore, even if powder lubricant is supplied to the groove G from one end of the groove G on the return trip, the powder lubricant supplied to the groove G can be prevented from passing through the groove G and being mixed into the molten metal. This makes it possible to prevent deterioration in the quality of the die-cast product.

In addition, the plunger tip 100 can be used continuously by replacing only the worn out cast iron rings 121 and 122, thereby reducing the cost of replacing parts due to wear and tear on the plunger tip 100.

In addition, since the cast iron rings 121, 122 are made of the same material, they have the same thermal expansion coefficient, which makes it possible to suppress differences in dimensional change due to temperature rise among the multiple cast iron rings 121, and to suppress deterioration of the sliding properties of the plunger tip 100 due to differences in dimensional change.

In addition, the plunger tip 100 makes it easier to supply powder lubricant to the sliding surface of the cast iron ring 121, which is the cast iron ring 121 that is more likely to have high sliding resistance, thereby preventing a decrease in the sliding properties of the plunger tip 100.

B. Other embodiments (B1) In the above embodiment, the plunger tip 100 includes the cast iron rings 121 and 122 having a ring shape, but the present disclosure is not limited thereto. The plunger tip 100 may include a cast iron ring having a C-shape with a portion of the outer periphery cut out. According to this configuration, even if the tip body 110 is formed as an integral member, the cast iron ring 121 can be assembled, so that the structure of the plunger tip 100 can be simplified and the manufacturing cost can be reduced.

(B2) In the above embodiment, the plunger tip 100 has two cast iron rings 121, 122, but the present disclosure is not limited to this. The plunger tip 100 may have three or more cast iron rings.

(B3) In the above embodiment, the cast iron ring 121 has a groove G, but the present disclosure is not limited to this. The cast iron ring 121 does not have to have a groove G.

(B4) In the above embodiment, the groove G is formed so that the longitudinal direction of the groove G is twisted relative to the central axis M of the cast iron ring 121, but the present disclosure is not limited to this. The groove G may be formed so that the longitudinal direction of the groove G is parallel to the central axis M of the cast iron ring 121.

(B5) In the above embodiment, the plunger tip 100 includes two cast iron rings 121, 122, but the present disclosure is not limited thereto. The plunger tip 100 may include only the cast iron ring 121. Alternatively, the cast iron ring may be an integrated sleeve member that covers the entire outer circumferential surface of the tip body 110.

(B6) In the above embodiment, the cast iron rings 121 and 122 are made of the same material, but the present disclosure is not limited to this. The cast iron rings 121 and 122 may be made of different materials. With this configuration, the cast iron ring 122, which is less prone to wear than the cast iron ring 121, is made of a cheaper material than the material used to make the cast iron ring 121, thereby reducing the manufacturing costs of the plunger tip 100.

The present disclosure is not limited to the above-described embodiments, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features in the embodiments corresponding to the technical features in each form described in the Summary of the Invention column can be replaced or combined as appropriate to solve some or all of the above-described problems or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate.

10...cavity, 100...plunger tip, 110...tip body, 111...body member, 112...body member, 121, 122...cast iron ring, 200...plunger rod, 300...injection sleeve, 400...fixed mold, 500...movable mold, 1000...die casting device, C...screw portion, G...groove, L, M...center axis

Claims (7)

A plunger tip for die casting that is used by sliding and reciprocating within an injection sleeve to which a powder lubricant containing graphite is applied,
A chip body;
a cast iron ring attached to the outer periphery of the tip body, having an outer diameter larger than the outer diameter of the tip body, and forming a sliding surface with the injection sleeve;
Equipped with
the average particle size of the graphite contained in the spheroidal graphite cast iron forming the cast iron ring is larger than the average particle size of the powder lubricant;
The cast iron ring has a groove on its outer circumferential surface,
The groove is formed linearly,
The longitudinal direction of the groove is formed in a twisted position with respect to the central axis of the cast iron ring,
One end of the groove reaches one of the end faces of the cast iron ring in the central axis direction, which is farther from the cavity in the reciprocating direction of the plunger tip, and the other end does not reach either end face of the cast iron ring.
Plunger tip. 2. The plunger tip of claim 1 ,
The plunger tip includes a plurality of the cast iron rings arranged in a line in a reciprocating direction of the plunger tip.
Plunger tip. 3. The plunger tip of claim 2 ,
The plurality of cast iron rings are formed from the same material.
Plunger tip. 2. The plunger tip of claim 1,
A plurality of the cast iron rings are arranged in a line in a reciprocating direction of the plunger tip,
Among the plurality of cast iron rings, the cast iron ring closest to the cavity in the reciprocating direction of the plunger tip has the groove on its outer circumferential surface.
Plunger tip. 3. The plunger tip according to claim 1,
The average particle size of the graphite is 1.5 times or more the average particle size of the powder lubricant.
Plunger tip. 6. The plunger tip of claim 5 ,
The average particle size of the graphite is 30 μm or more.
Plunger tip. 1. A die casting apparatus comprising:
An injection sleeve;
a plunger tip for die casting that is used by reciprocating while sliding within the injection sleeve; and a powder lubricant containing graphite that is applied between the injection sleeve and the plunger tip;
Equipped with
The plunger tip is
A chip body;
a cast iron ring attached to the outer periphery of the tip body, having an outer diameter larger than the outer diameter of the tip body, and forming a sliding surface with the injection sleeve;
the average particle size of the graphite contained in the spheroidal graphite cast iron forming the cast iron ring is larger than the average particle size of the powder lubricant;
The cast iron ring has a groove on its outer circumferential surface,
The groove is formed linearly,
The longitudinal direction of the groove is formed in a twisted position with respect to the central axis of the cast iron ring,
One end of the groove reaches one of the end faces of the cast iron ring in the central axis direction, which is farther from the cavity in the reciprocating direction of the plunger tip, and the other end does not reach either end face of the cast iron ring.
Die casting equipment.

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