Die-casting plunger tip and injection device

Abstract

To provide a die-casting plunger tip allowed to forcibly smash a solidification layer produced in a sleeve and inhibit a solidification piece from intruding into a metal mold, and an injection device.SOLUTION: A die-casting plunger tip 20, allowed to slide in a circularly-cylindrical sleeve 12 to inject a metal melt in the sleeve into a metal mold, comprises: smash portions 30 that are provided on an outer peripheral surface closer to a front end of the plunger tip and allowed to contact a solidification layer of the metal melt produced on an inner peripheral surface of the sleeve to smash the solidification layer; and groove portions 32 that are provided oppositely of the smash portion in a circumferential direction and recessed radially inside of the smash portion. The smash portion is formed triangular in shape having an apex closer to a front end of the plunger tip, in a region between circumferentially-adjacent two of the groove portions.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a plunger tip and an injection device for die casting, and more particularly to a plunger tip that slides inside a sleeve into which molten metal is poured, and an injection device equipped with the plunger tip. [Background technology]

[0002] An injection device for die casting includes a sleeve connected to a die into which molten aluminum is poured, and a plunger rod with a plunger tip attached to its tip that slides inside the sleeve. In this type of injection device, when molten metal is supplied into the sleeve and the plunger rod is advanced toward the die, the molten metal is pressurized by the plunger tip and injected into the cavity of the die.

[0003] When the molten metal is poured into the sleeve, the molten metal cools and a solidified layer is formed on the inner peripheral surface of the sleeve. When the plunger tip advances in the sleeve in this state, the front surface of the plunger tip comes into contact with the solidified layer formed inside the sleeve, scraping the solidified layer. If a part of the scraped off solidified layer, i.e., a solidified piece, gets mixed into the molten metal and enters the cavity of the mold, it will lead to a deterioration in the quality of the cast product.

[0004] In order to prevent solidified pieces from being mixed into the product, Patent Document 1 describes a structure in which the plunger tip has a cylindrical portion that slides inside the sleeve and a truncated cone-shaped protruding portion whose outer diameter decreases from the cylindrical portion toward the tip side. In this plunger tip, a recess is formed at the tip of the protruding portion. In an injection device equipped with such a plunger tip, when the plunger tip advances inside the sleeve toward the mold, the solidified layer generated on the sleeve is scraped off by the cylindrical portion. The scraped off solidified pieces can be captured in the space between the outer peripheral surface of the protruding portion of the plunger tip and the inner peripheral surface of the sleeve, and in the recess of the protruding portion. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent No. 5647848 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] In the injection device described in Patent Document 1, it is possible to capture the solidified pieces and suppress their entry into the mold. However, the solidified layer generated in the sleeve cannot be sufficiently crushed, and there is a concern that the solidified layer remains in the sleeve. The solidified layer remaining in the sleeve may lead to a deterioration in the quality of the subsequent cast product, and may also lead to a reduction in the life of the sleeve by fusing with the metal sleeve and becoming a welded state.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide a plunger tip and an injection device for die casting that can forcibly crush the solidified layer generated in the sleeve and suppress the entry of solidified pieces into the mold. [Means for Solving the Problems]

[0008] In order to achieve the above object, an embodiment of the present invention is a plunger tip for die casting that slides inside a cylindrical sleeve and injects the molten metal inside the sleeve into a mold. A crushing portion provided on the outer peripheral surface of the tip side of the plunger tip, which contacts the solidified layer of the molten metal generated on the inner peripheral surface of the sleeve and can crush the solidified layer, and groove portions provided on both sides of the crushing portion in the circumferential direction and recessed radially inward from the crushing portion, and the crushing portion is a region between two adjacent groove portions in the circumferential direction and is formed in a triangular shape with the tip side of the plunger tip as the top.

[0009] Also, to achieve the above object, one embodiment of the present invention is an injection device for die casting, comprising a cylindrical sleeve and a plunger tip that slides within the sleeve to inject molten metal within the sleeve into a mold. The plunger tip is provided on the outer peripheral surface of the tip side, and has a crushing portion that contacts a solidified layer of the molten metal formed on the inner peripheral surface of the sleeve and can crush the solidified layer, and groove portions provided on both sides of the crushing portion in the circumferential direction and recessed radially inward of the crushing portion. The crushing portion is a region between two adjacent groove portions in the circumferential direction and is formed in a triangular shape with the tip side of the plunger tip as the top.

Effect of the Invention

[0010] According to the plunger tip and injection device for die casting of the present invention, the chill layer formed within the sleeve can be forcibly crushed and recovered.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

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Figure 10

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Figure 12

Mode for Carrying Out the Invention

[0012] FIG. 1 and FIG. 2 are cross-sectional views showing a die-casting apparatus 1 provided with an injection device 10 for die-casting according to an embodiment of the present invention. The die-casting apparatus 1 includes an injection device 10 and a mold 40. The injection device 10 includes a sleeve 12, a ladle 14, a plunger rod 16, an injection cylinder 18, and a plunger tip 20. The die-casting plunger tip 20 is attached to the tip of the plunger rod 16 and slides within the sleeve 12.

[0013] The mold 40 includes a fixed mold 44 fixed to a fixed plate 42 and a movable mold 46 that can approach and separate from the fixed mold 44. As shown in FIG. 1, the mold 40 is configured such that a cavity 41 as a casting space is formed inside the mold 40 in a mold-closed state where the movable mold 46 is brought close to the fixed mold 44.

[0014] The injection device 10 is a device for injecting the molten metal 11 into the cavity 41 of the mold 40. In the present embodiment, an aluminum alloy molten metal is used as an example of the molten metal 11. In the following description, the molten metal 11 is also simply referred to as "molten metal 11".

[0015] The sleeve 12 is formed in a cylindrical shape, and a first end 12a, which is one end, is fixed to the fixed mold 44 and extends in the horizontal direction. A pouring port 13 that opens upward is formed on the circumferential surface of the sleeve 12 on the side of the second end 12b. The injection device 10 injects a predetermined amount of molten metal 11 into the sleeve 12 through the pouring port 13 from the ladle 14, which is a pouring means. The molten metal 11 in the sleeve 12 is pressurized by the plunger tip 20 and injected into the mold 40.

[0016] The plunger rod 16 is formed in a rod shape extending linearly. The rear end portion of the plunger rod 16 is connected to the tip end portion of the piston rod 17 of the injection cylinder 18. The injection cylinder 18 is a hydraulic cylinder operated by hydraulic pressure, and the amount and pressure of the hydraulic oil are controlled by a hydraulic control circuit (not shown) to move the piston rod 17 forward and backward. The plunger rod 16 is configured to be able to move forward and backward within the sleeve 12 by receiving power from the injection cylinder 18. A cylindrical plunger tip 20 that slides within the sleeve 12 is attached to the tip end of the plunger rod 16.

[0017] FIG. 3 is a perspective view of the plunger tip 20, and FIG. 4 is a partial cross-sectional side view of the plunger tip 20. In the following description, the tip end side of the plunger tip 20 is the side of the first end portion 12a of the sleeve 12, that is, the mold 40 side, in the state of being assembled to the injection device 10 shown in FIG. 1, and the rear end side of the plunger tip 20 is the side of the second end portion 12b of the sleeve 12, that is, the side connected to the plunger rod 16. The plunger tip 20 is formed to be slidable within the sleeve 12 and has a crushing portion 30 and a groove portion 32 on the outer peripheral surface of the tip end side. In the present embodiment, the plunger tip 20 includes a cylindrical main body portion 22 and a protruding portion 24 provided on the tip end side of the main body portion 22, and the crushing portion 30 and the groove portion 32 are provided at the tip end portion of the main body portion 22.

[0018] The main body portion 22 is a hollow cylinder and has an outer diameter substantially equal to the inner diameter of the sleeve 12 so as to slide within the sleeve 12. In the present embodiment, a missing portion 23 where a part of the outer peripheral surface is missing is formed at the rear end portion of the main body portion 22. The missing portion 23 is a portion used when connecting to other members, and the plunger tip 20 may have a shape without the missing portion 23.

[0019] When the plunger tip 20 slides within the sleeve 12, the crushing portion 30 is a part that contacts the solidified layer formed by the molten metal 11 on the inner peripheral surface of the sleeve 12 and can crush the solidified layer. The groove portion 32 is provided on both sides of the crushing portion 30 in the circumferential direction of the plunger tip 20, and is a portion that is recessed radially inward of the crushing portion 30. The groove portion 32 is formed such that the groove width, that is, the dimension in the circumferential direction, increases toward the tip side of the plunger tip 20. In the present embodiment, it is formed in a trapezoidal shape with the tip side of the plunger tip 20 as the lower base and the rear end side as the upper base.

[0020] The crushing portion 30 is a region between two groove portions 32 adjacent in the circumferential direction, and is formed in a triangular shape with the tip side of the plunger tip 20 as the top portion 30a. In the examples shown in FIGS. 3 and 4, the top portion 30a of the crushing portion 30 is formed in a sharp shape forming an acute angle. In the plunger tip 20 of the present embodiment, the crushing portion 30 and the groove portion 32 are alternately arranged in the circumferential direction of the plunger tip 20 and are formed on the entire circumference of the plunger tip 20.

[0021] In the region where the crushing portion 30 is formed on the plunger tip 20, that is, at the tip of the main body portion 22 where the crushing portion 30 exists, the outer diameter of the plunger tip 20 gradually decreases toward the tip side of the plunger tip 20. In other words, the triangular surface of the crushing portion 30 is inclined radially inward toward the tip side of the plunger tip 20. The inclination angle of the surface of the crushing portion 30 can be, for example, at most 0.5° or less, preferably around 0.2°. In the main body portion 22, in the tip region of the plunger tip 20 where the groove portion 32 is formed, the area of contact with the high-temperature molten metal 11 becomes large, so the rate of thermal expansion also becomes large. By gradually reducing the outer diameter of the plunger tip 20 toward the tip side in the region where the crushing portion 30 exists as in the present embodiment, the influence of thermal expansion can be absorbed.

[0022] As shown in Fig. 5, the bottom surface 32a of the groove portion 32 is inclined radially inward of the plunger chip 20 as it goes toward the tip side of the plunger chip 20. The plunger chip 20 of the present embodiment is integrally formed using a mold. By providing a draft angle on the bottom surface 32a of the groove portion 32, it is possible to smoothly release the mold after molding. The inclination angle θ of the bottom surface 32a can be in the range of, for example, 2° to 10°.

[0023] The protruding portion 24 of the plunger chip 20 is a portion that protrudes from the tip surface of the main body portion 22 and is formed in a frustum shape with an outer diameter gradually decreasing toward the tip side of the plunger chip 20. The central axis of the protruding portion 24 is coaxial with the central axis of the main body portion 22. At the rear end of the protruding portion 24 where the outer diameter is the largest, the outer diameter of the protruding portion is set to be smaller than the outer diameter of the main body portion 22. As shown in Fig. 4, the outer peripheral surface of the rear end portion of the protruding portion 24 is located radially inward of the groove portion 32. The axial length of the protruding portion 24 is preferably 1 / 10 or less of the axial length of the main body portion 22. In the present embodiment, as an example, the main body portion 22 is set to 165 mm and the protruding portion 24 is set to 15 mm.

[0024] Next, a die-casting method using the plunger tip 20 for die-casting and the injection device 10 will be described. First, in the die-casting apparatus 1, the mold 40 moves the movable mold 46 closer to the fixed mold 44 to bring the fixed mold 44 and the movable mold 46 into a clamped state with the molds aligned. The injection device 10 retracts the piston rod 16 and the plunger tip 20 so that the plunger tip 20 is in a standby position retracted from the sprue 13. In this state, a lubricant (not shown) is applied to the inner peripheral surface of the sleeve 12 or the plunger tip 20. The lubricant is for lubricating the movement of the plunger tip 20 relative to the sleeve 12, and for example, lubricating oil can be used. The lubricant can be applied, for example, by spraying from the sprue 13 or by directly dripping it onto the plunger tip 20. Next, as shown in FIG. 1, the molten metal 11 is poured into the sleeve 12 from the sprue 13 using the ladle 14. Then, the plunger rod 16 and the plunger tip 20 are moved forward toward the mold 40 by the driving force of the injection cylinder 18.

[0025] FIG. 6 is a diagram for explaining the movement state of the plunger tip 20 in the sleeve 12 in the injection device 10, showing a state where the plunger tip 20 moves forward in the sleeve 12. The molten metal 11 injected into the sleeve 12 is cooled by the sleeve 12 which is at a lower temperature than this, and a solidified layer 54 where the molten metal 11 has solidified, a so-called "chill layer", is formed on the inner peripheral surface of the sleeve 12. When the plunger tip 20 moves forward in the sleeve 12 with the solidified layer 54 formed on the inner wall, the crushing portion 30 of the plunger tip 20 contacts the solidified layer 54 and the solidified layer 54 is crushed. Since the crushing portion 30 is formed in a triangular shape with the tip side being the top 30a, the solidified layer 54 can be forcibly crushed by the sharp top 30a. In the present embodiment, since the top 30a of the crushing portion 30 has a pointed shape with a sharp tip, the crushing effect is higher.

[0026] When the solidified layer 54 is crushed by the crushing part 30, a part of the solidified layer 54 peels off as solidified pieces 56. The peeled solidified pieces 56, the so-called "broken chill layer", enter and are collected inside the groove parts 32 provided on both sides of the crushing part 30. Thus, in the plunger tip 20 of the present embodiment, the solidified layer 54 generated in the sleeve 12 can be forcibly crushed, and further, the peeled solidified pieces 56 can be collected in the groove parts 32 to prevent the solidified pieces 56 from entering the cavity 41 of the mold 40.

[0027] Furthermore, in the injection device 10 of the present embodiment, the surplus lubricant adhering to the inside of the sleeve 12 can also be collected in the groove parts 32. When the lubricant comes into contact with the molten metal 11 and is exposed to high temperature, gas may be generated due to the combustion of the oil component, which may affect the quality of the casting product. In the plunger tip 20 of the present embodiment, by collecting the lubricant in the groove parts 32 to suppress the contact with the molten metal 11, it is possible to suppress the generation of gas.

[0028] When the plunger tip 20 comes into contact with the molten metal 11, the plunger tip 20 thermally expands due to the high-temperature molten metal 11. In the main body part 22 of the plunger tip 20, in the region where the groove parts 32 and the crushing part 30 are formed, since the contact area with the molten metal 11 becomes large, the rate of thermal expansion becomes high. In the present embodiment, at the tip of the plunger tip 20 where the groove parts 32 and the crushing part 30 are formed, the outer diameter of the main body part 22 of the plunger tip 20 is gradually reduced toward the tip side, so that when thermally expanded, the outer diameter of the main body part 22 can be made uniform in the axial direction.

[0029] When the plunger tip 20 moves forward toward the mold 40 by the driving force of the injection cylinder 18, the molten metal 11 in the sleeve 12 is pressurized by the plunger tip 20, and the molten metal 11 is injected into the cavity 41 of the mold 40. Then, as shown in FIG. 2, the movable mold 46 is separated from the fixed mold 44 to open the mold, and the casting product 50 having the shape of the cavity 41 is taken out from the mold 40.

[0030] The solidified pieces 56 and lubricant collected in the groove portion 32 of the plunger chip 20 are discharged to the outside of the sleeve 12 by adhering to the biscuit 51 of the casting product 50 formed near the casting gate of the mold 40 during casting, as shown in FIGS. 2 and 7. The biscuit 51 is a metal in which the molten metal 11 remaining in the space between the sleeve 12 and the cavity 41 solidifies, and is a casting unnecessary material that is separated from the casting product 50. In the plunger chip 20 and the injection device 10 of the present embodiment, the solidified layer 54 can be forcibly crushed, and the collected solidified pieces 56 can be discharged to the outside of the sleeve 12 for each injection, so that the solidified layer 54 and the solidified pieces 56 can be prevented from remaining in the sleeve 12. As a result, the quality of the product can be improved, and it is possible to prevent the solidified layer 54 from fusing with the sleeve 12 and becoming in a welded state, thereby reducing the life of the sleeve 12.

[0031] Next, with reference to FIGS. 8, 9, 10, 11, and 12, another embodiment of the plunger chip 20 will be described. The plunger chip 20 shown in FIG. 8 has a main body portion 22 and a protruding portion 24. The main body portion 22 has a crushing portion 30 and a groove portion 32 provided at the tip end portion, and a rear crushing portion 36 and a rear groove portion 38 provided at the rear end portion. In the plunger chip 20 shown in FIG. 8, since the structure other than the rear crushing portion 36 and the rear groove portion 38 is the same as that of the plunger chip 20 shown in FIG. 3, the details are omitted here.

[0032] The rear crushing portion 36 is a portion that can come into contact with the solidified layer 54 formed by the molten metal 11 on the inner peripheral surface of the sleeve 12 when the plunger chip 20 slides inside the sleeve 12 and can crush the solidified layer 54. The rear groove portion 38 is provided on both sides of the rear crushing portion 36 in the circumferential direction of the plunger chip 20, and is a portion that is recessed more radially inward than the rear crushing portion 36. The rear groove portion 38 is formed so that the groove width, that is, the dimension in the circumferential direction, increases toward the rear end side of the plunger chip 20. In the illustrated example, it is formed in a trapezoidal shape with the rear end side of the plunger chip 20 as the bottom and the front end side as the top.

[0033] The rear crushing part 36 is an area between two rear groove parts 38 adjacent in the circumferential direction, and is formed in a triangular shape with the rear end side of the plunger tip 20 being the top 36a. In the example shown in FIG. 8, the top 36a of the rear crushing part 36 is formed in a pointed shape with an acute angle, and the rear crushing part 36 and the rear groove part 38 are alternately arranged in the circumferential direction of the plunger tip 20A and are formed on the entire circumference of the plunger tip 20. In the plunger tip 20 shown in FIG. 8, each of the rear crushing part 36 and the rear groove part 38 has the same shape as each of the crushing part 30 and the groove part 32, and in the axial direction of the plunger tip 20, the top 36a of the rear crushing part 36 is formed so as to be in the opposite direction to the top 30a of the crushing part 30.

[0034] In the injection device 10 using the plunger tip 20 of the present embodiment, when the plunger tip 20 retracts away from the mold 40 in the sleeve 12 where the solidified layer 54 is formed on the inner wall, the rear crushing part 36 can contact the solidified layer 54 and crush the solidified layer 54. Since the top 36a of the rear crushing part 36 is formed in a pointed shape, the sharp top 36a can forcibly crush the solidified layer 54. The solidified pieces 56 crushed by the rear crushing part 36 and peeled off from the solidified layer 54 can be collected inside the rear groove parts 38 provided on both sides of the rear crushing part 36.

[0035] In another embodiment of the plunger tip 20 shown in FIG. 9, at the tip of the plunger tip 20, the crushing part 30, the groove parts 32 on both sides thereof, the rear crushing part 36, and the rear groove parts 38 on both sides thereof are formed at intervals on the entire circumference of the plunger tip 20. Thus, in the plunger tip 20, one crushing part 30 and a pair of groove parts 32 formed on both sides thereof do not have to be formed on the entire circumference, and at least one set may be formed. In such a case, for example, by advancing in the sleeve 12 while rotating the plunger tip 20, the solidified layer 54 generated in a wide range in the circumferential direction by one crushing part 30 can be crushed.

[0036] In another embodiment of the plunger tip 20 shown in FIG. 10, in the circumferential direction, the width of the groove portion 32 is increased so that there is no region where the crushing portion 30 and the groove portion 32 are not formed. Similarly, on the rear end side of the plunger tip 20, a rear groove portion 38 having a large groove width is provided together with the rear crushing portion 36. Thus, by increasing the groove widths of the groove portion 32 and the rear groove portion 38, the amount of the solidified piece 56 recovered can be increased.

[0037] In other embodiments of the plunger tip 20 shown in FIGS. 11 and 12, the crushing portion 30 and the rear crushing portion 36 are formed in a triangular shape, and Rs are provided at their tops 30a, 36a. Thus, the tops 30a, 36a may have a rounded shape. Also, as in the example of the plunger tip 20 shown in FIG. 12, the crushing portion 30 and the rear crushing portion 36 may be in an asymmetric triangular shape that is not line-symmetric.

[0038] Note that the present invention is not limited to the above-described embodiments and modifications, and various changes can be made without departing from the spirit of the invention.

Explanation of Signs

[0039] 1 Die casting apparatus 10 Injection device 12 Sleeve 13 Pouring gate 16 Plunger rod 20 Plunger tip 30 Crushing portion 32 Groove portion 36 Rear crushing portion 38 Rear groove portion 40 Mold 41 Cavity 50 Cast product 51 Biscuit 54 Solidified layer 56 Solidified piece

Claims

1. In a plunger tip for die casting that slides inside a cylindrical sleeve and injects the molten metal inside the sleeve into a mold, a crushing portion provided on the outer peripheral surface of the tip side of the plunger tip, which contacts the solidified layer of the molten metal formed on the inner peripheral surface of the sleeve and can crush the solidified layer; and groove portions provided on both sides of the crushing portion in the circumferential direction, which are recessed more radially inward than the crushing portion. The plunger tip is characterized in that the crushing portion is a region between two adjacent groove portions in the circumferential direction and is formed in a triangular shape with the tip side of the plunger tip as the top.

2. The plunger tip according to claim 1, wherein the crushing portion and the groove portions are alternately arranged in the circumferential direction and formed on the entire circumference of the plunger tip.

3. The plunger tip according to claim 1 or 2, wherein in the region where the crushing portion is formed, the outer diameter of the plunger tip gradually decreases toward the tip side of the plunger tip.

4. The plunger tip according to claim 1 or 2, wherein the bottom surface of the groove portion is inclined radially inward of the plunger tip as it goes toward the tip side of the plunger tip.

5. a rear crushing portion provided on the outer peripheral surface of the rear end portion of the plunger tip, which contacts the solidified layer formed on the inner peripheral surface of the sleeve and can crush the solidified layer; and rear groove portions provided on both sides of the rear crushing portion in the circumferential direction, which are recessed more radially inward than the rear crushing portion. The plunger tip according to claim 1 or 2, wherein the rear crushing portion is a region between two adjacent rear groove portions in the circumferential direction and is formed in a triangular shape with the rear end side of the plunger tip as the top.

6. In an injection device for die casting comprising a cylindrical sleeve and a plunger tip that slides inside the sleeve and injects the molten metal inside the sleeve into a mold, the plunger tip has a crushing portion provided on the outer peripheral surface of the tip side, which contacts the solidified layer of the molten metal formed on the inner peripheral surface of the sleeve and can crush the solidified layer; and groove portions provided on both sides of the crushing portion in the circumferential direction, which are recessed more radially inward than the crushing portion. The crushing part is an area between two adjacent groove parts in the circumferential direction, and is formed in a triangular shape with the tip side of the plunger tip as the top, and is characterized by an injection device.

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