Plunger, sealing method, and supply device

Abstract

The present invention provides a plunger to be used in a die casting apparatus, said plunger having sealing performance that meets a high vacuum requirement.　A plunger (50) according to the present invention comprises: a plunger tip (60) on the outer periphery of which a seal ring (66), a spacer ring (67A), and a backup ring (68) are mounted in order from the front (F); a plunger rod (80) connected to the rear (R) of the plunger tip (60); and a sealing medium supply path (65) for supplying a sealing medium toward at least one from among the seal ring (66), the spacer ring (67A), and the backup ring (68) through the plunger tip (60).

Description

Plunger, Sealing Method, and Supply Device

[0001] The present invention relates to a plunger tip used in a die-casting apparatus.

[0002] The die-casting method is a processing method in which a metal typified by an aluminum alloy is melted and poured into a cavity in a mold at high speed and high pressure to obtain a cast product.

[0003] In a plunger that constitutes an injection mechanism in a die-casting apparatus, since the outer peripheral surface of the plunger tip slides on the inner peripheral surface of the sleeve, wear occurs on the sliding surface. In a more severe case, galling may occur, so it is common to apply a lubricant to the sliding surface to make the sliding smooth.

[0004] For example, the die-cast plunger disclosed in Patent Document 1 has a structure in which a plunger tip and a plunger rod are connected by a joint interposed therebetween, and two flow paths for separately supplying air and a lubricant in the axial direction of the plunger rod are provided. At the outlet-side end portions of the two flow paths connected to the joint, air and the lubricant are mixed to form a mist, and the mist of the lubricant mixture is distributed to a plurality of single flow paths provided in the joint via a distribution path, and the mist of the lubricant mixture is sprayed from nozzles opening toward the outer peripheral side provided in each single flow path onto the inner surface of the plunger sleeve to apply the lubricant to the inner surface of the plunger sleeve.

[0005] In the die-casting method, in order to pour molten metal into a cavity, which is a space in a mold, at high speed, vacuum die-casting that evacuates the air in the cavity before pouring has been applied mainly to products with high quality requirements. In this vacuum die-casting, it is required to ensure the sealing performance between the plunger sleeve and the plunger.

[0006] Japanese Patent Application Laid-Open No. 2009-279645

[0007] An object of the present invention is to provide a plunger used in a die-casting apparatus having a sealing performance that meets the increasing requirements for high vacuum in recent years.

[0008] The plunger (50) in the die-casting apparatus of the present invention comprises a plunger tip (60) on which a seal ring (66), a spacer ring (67A), and a backup ring (68) are arranged in order from the front (F) on its outer circumference; a plunger rod (80) connected to the rear (R) of the plunger tip (60); and a seal medium supply passage (65) that supplies a seal medium through the plunger tip (60) toward at least one of the seal ring (66), spacer ring (67A), and backup ring (68).

[0009] Preferably, the seal ring (66) may include a first seal medium passage (66B) that is connected to a seal medium supply passage (65) and penetrates in the thickness direction, and an annular seal medium storage groove (66A) that is connected to the first seal medium passage (66B) and recessed from the outer surface of the seal ring (66). According to the plunger (50) having this requirement, by filling the seal medium storage groove (66A) with seal medium via the first seal medium passage (66B), a sealing performance is provided that maintains a vacuum between the seal ring (66) and the plunger sleeve (21), and lubrication is provided that stabilizes the sliding between the plunger tip (60) and the plunger sleeve (21).

[0010] Preferably, the plunger (50) is equipped with a spacer ring retainer (67B) stacked on the outside of the spacer ring (67A), the spacer ring (67A) is equipped with a second seal medium passage (67C) that is connected to a seal medium supply passage (65) and penetrates in the thickness direction, and each of the seal ring (66) and backup ring (68) is equipped with a joint. According to the plunger (50) equipped with these requirements, the second seal medium passage (67C) is provided in the spacer ring (67A) as a passage for the seal medium, and the seal medium is supplied between the rings and the plunger sleeve (21) through the joint gap between the seal ring 66 and the backup ring (68). This not only improves sealing performance but also ensures lubrication between the rings and the plunger sleeve (21). In this case, the backup ring (68) acts as a seal ring.

[0011] Preferably, the sealing medium supply passage (65) is on the outer circumferential surface of the plunger tip (60) and can open toward the sealing ring (66). In a plunger (50) having this requirement, the sealing medium is supplied to the gap between the plunger tip (60) and the sealing ring (66) without providing a first sealing medium passage (66B) in the rings. The sealing performance is ensured by the pressure of the supplied sealing medium pressing the sealing ring against the plunger sleeve (21). In addition, a portion of the sealing medium leaks into and fills the gap between the outer tip (61) and the sealing ring (66), which not only enhances the sealing performance but also ensures lubrication between the rings and the plunger sleeve (21). In this case as well, the backup ring acts as a sealing ring.

[0012] Preferably, a seal medium supply pipe (5) connected to the seal medium supply passage (65) is attached to the plunger rod (80). A plunger (50) having this requirement allows the seal medium supply pipe (5) to be easily handled together with the plunger rod (80).

[0013] Preferably, the plunger tip (60) comprises a cylindrical outer tip (61) having a housing gap inside, and an inner tip (71) positioned in the housing gap of the outer tip (61), wherein the outer tip (61) comprises a tip head (92) and a tip body (96) that are separable in the direction of the central axis (C). With a plunger tip (60) having this requirement, rings can be attached and detached without disassembling the plunger tip (60) into the outer tip (61) and the inner tip (71).

[0014] The present invention provides a sealing method between a plunger sleeve (21) and a plunger (50) described above, which is provided reciprocally movably inside the plunger sleeve (21), wherein the sealing medium is supplied from a sealing medium supply passage (65). In the sealing method of the present invention, the sealing medium can be filled into the sealing medium storage groove (66A) via a first sealing medium passage (66B). The sealing medium can also be supplied to the front side of the spacer ring (67A) via a second sealing medium passage (67C). Furthermore, the sealing medium can be supplied between the plunger tip (60) and the sealing ring (66) via the sealing medium supply passage (65).

[0015] The present invention provides a supply device (130) for supplying a sealing medium to a sealing medium supply pipe (5) in a die-casting apparatus comprising a plunger sleeve (21) and a plunger (50) as described above, which is provided to be reciprocally movable inside the plunger sleeve (21). The supply device (130) includes a tank (131) for storing a sealing medium, a pressure pump (133) for sucking in and discharging the sealing medium stored in the tank (131), a metering pump (135) for discharging a predetermined amount of the sealing medium discharged from the pressure pump (133), a medium supply pipe (137) through which the sealing medium flows to the sealing medium supply pipe (5) via the tank (131), the pressure pump (133), and the metering pump (135), and an on / off valve (139) provided in the medium supply pipe (137) between the pressure pump (133) and the metering pump (135), which opens and closes according to the pressure of the sealing medium inside the medium supply pipe (137).

[0016] According to the plunger of the present invention, in addition to the sealing performance provided by the seal ring, a sealing medium can be supplied toward the seal ring. This makes it possible to maintain vacuum sealing performance during the vacuum evacuation process during injection in die casting, and also maintain lubrication between the rings and the plunger sleeve.

[0017] This is a side view showing the schematic configuration of a die-casting apparatus. This is a longitudinal cross-sectional view showing the configuration of a plunger according to the first embodiment. This is an enlarged view of the plunger tip and its vicinity in Figure 2. This is a diagram showing the procedure for attaching various rings to the plunger tip according to the embodiment and the function of the rings. This is a side cross-sectional view showing the main part of a plunger according to the second embodiment. This is a plan view showing the main part of a plunger according to the second embodiment. This is a side cross-sectional view showing the main part of a plunger according to the third embodiment. This is a side cross-sectional view showing the main part of a plunger according to the fourth embodiment. This is a diagram showing the schematic configuration of an apparatus used for evaluating sealing performance. This is a graph showing the results of the sealing performance evaluation. This is a graph showing the results of the sealing performance evaluation. This is a diagram showing the configuration of a supply device preferred for supplying a high-viscosity substance, such as grease, to a sealing medium supply pipe.

[0018] Next, embodiments of plungers applied to die-casting apparatuses will be described in detail with reference to the drawings as appropriate. In each figure, common parts are denoted by the same reference numerals, and redundant explanations will be omitted. Furthermore, the following description will be in the order of a configuration example of a die-casting apparatus 1 to which the plunger 50 according to the embodiment is applied, the configuration of the plunger 50, and a casting experiment (example) conducted using the plunger 50.

[0019] [Configuration of die-casting apparatus 1: See Figure 1] The die-casting apparatus 1 comprises a mold section 10 that forms a casting cavity CA into which molten metal is injected, an injection section 20 for injecting molten metal into the casting cavity CA of the mold section 10, and a vacuum suction section 30 for evacuating the casting cavity CA prior to the injection of molten metal. Although not shown in the figures, the die-casting apparatus 1 is equipped with a ladle for supplying molten metal to the injection section 20. In the die-casting apparatus 1, front (F) and rear (R) are defined as shown in Figure 1 and other figures.

[0020] The mold section 10 includes a fixed mold 12 whose position is fixed, and a movable mold 13 that moves back and forth relative to the fixed mold 12. In the mold section 10, when the movable mold 13 is abutted against the fixed mold 12 in a closed state, a casting cavity CA is formed between the fixed mold 12 and the movable mold 13. The mold section 10 is equipped with a device for clamping the fixed mold 12 and the movable mold 13, although this is not shown in the figure. In this closed state, a flow path for molten metal is formed between the fixed mold 12 and the movable mold 13, consisting of a gate 14 that opens into the casting cavity CA, and a runner 15 that connects this gate 14 to the plunger sleeve 21 of the injection section 20 which is coupled to the back of the fixed mold 12. The movable mold 13 has a built-in ejector 11 for demolding the cast product.

[0021] The injection unit 20 comprises a plunger sleeve 21 and a plunger 50 slidably disposed inside the plunger sleeve 21. The plunger 50 comprises a plunger tip 60, a plunger rod 80 with one end connected to the plunger tip 60, and an injection cylinder 24 connected to the other end of the plunger rod 80, which moves the plunger tip 60 forward or backward via the plunger rod 80. The plunger sleeve 21 is provided with a molten metal inlet 22 at the upper rear end for receiving molten metal, and molten metal is stored inside.

[0022] The vacuum suction unit 30 includes a vacuum pump 31, a vacuum tank 32 whose internal space is depressurized by the vacuum pump 31, a vacuum pipe 33 that connects the vacuum tank 32 to the casting cavity CA in the mold unit 10, and a pressure reducing valve 34 provided on the vacuum pipe 33. The internal space of the vacuum tank 32 is maintained at a predetermined negative pressure by intermittently operating the vacuum pump 31. By opening the pressure reducing valve 34, the air in the casting cavity CA is drawn into the vacuum tank 32. In addition, to evacuate the inside of the plunger sleeve 21, a vent hole for vacuum evacuation can be provided in the plunger sleeve 21, and vacuum evacuation can be performed through the vent hole.

[0023] At the start of casting, the plunger tip 60 is in the retracted position within the plunger sleeve 21. The pressure reducing valve 34 is also closed. After a predetermined amount of molten metal is supplied into the plunger sleeve 21 from the hot water inlet 22 using a ladle (not shown), the plunger tip 60 is advanced, causing the molten metal to be injected, i.e., pressurized and filled, from inside the plunger sleeve 21 through the runner 15 and gate 14 into the casting cavity CA. The pressure reducing valve 34 is opened when the plunger tip 60 has advanced beyond the hot water inlet 22 to a predetermined position. During this vacuum evacuation, sealing performance is required at the sliding surfaces of the plunger sleeve 21 and the plunger tip 60.

[0024] [Plunger 50: See Figures 2 and 3] Next, the plunger 50 will be described. The plunger 50 comprises a plunger tip 60, a plunger rod 80 that supports the plunger tip 60 at the front (F), and a sealing medium supply pipe 5 that supplies a sealing medium such as grease to the plunger tip 60. The sealing medium will be described in more detail later. In the plunger 50, as shown in Figures 1 and 2, the side on which the plunger tip 60 is provided is defined as the front (F), and the side opposite to the front (F) on the central axis C is defined as the rear (R). Front (F) and rear (R) have relative meanings. Also, in the plunger 50, as shown in Figures 1 and 2, the radial direction RD and the longitudinal direction L are defined.

[0025] [Plunger tip 60: See Figure 3] The plunger tip 60 comprises an outer tip 61 positioned on the outside of the radial direction RD and an inner tip 71 positioned on the inside of the outer tip 61 in the radial direction RD.

[0026] [Outer tip 61: See Figure 3] The outer tip 61 has a cylindrical shape with a closed front (F). The outer tip 61 includes a cap 62 provided at the tip, a ring retaining cylinder 63 connected to the cap 62 and having a gap inside for housing the inner tip 71, and a fitting sleeve 64 connected to the ring retaining cylinder 63. In the outer tip 61, the cap 62, the ring retaining cylinder 63, and the fitting sleeve 64 are integrally formed from a metal material such as alloy tool steel, pure copper, or copper alloy, as an example. The inner tip 71 and plunger rod 80 are made similarly.

[0027] The outer circumference of the ring-holding cylinder 63 is provided with a first holding portion 63A, a second holding portion 63B, and a third holding portion 63C, which hold rings described later. The outer surfaces of the first holding portion 63A and the third holding portion 63C form arcuate surfaces that are equal in distance from the central axis C, for example, while the outer surface of the second holding portion 63B forms an arcuate surface that is shorter in distance from the central axis C than the first holding portion 63A and the third holding portion 63C. The fitting sleeve 64 is formed with a smaller radial dimension RD than the ring-holding cylinder 63 and is fitted with a fixed flange 79 for joining the outer tip 61 and the plunger rod 80.

[0028] The outer tip 61 is provided with a seal medium supply passage 65 for supplying the seal medium, which is sent from the seal medium supply pipe 5, between the outer tip 61 and the plunger sleeve 21. The seal medium supply passage 65 includes a first supply passage 65A drilled parallel to the central axis C from the rear R end of the fitting sleeve 64 to the front F end of the ring holding cylinder 63, and a second supply passage 65B connected to the front F end of the first supply passage 65A and extending outward in the radial direction RD. The tip of the second supply passage 65B opens to the surface of the first holding portion 63A. The seal medium supplied through this opening passes through the seal ring 66, which will be described later, outward in the radial direction RD, and is supplied between the outer tip 61, which includes the rings, and the plunger sleeve 21. Grease is one example of the seal medium referred to here.

[0029] In the outer tip 61, as an example, a seal ring 66, a spacer ring 67A, a spacer ring retainer 67B, and a backup ring 68 are arranged in order from the front F in a ring retaining cylinder 63. The seal ring 66 is fitted into the first retaining portion 63A, the spacer ring 67A is fitted into the second retaining portion 63B, and the backup ring 68 is fitted into the third retaining portion 63C. The seal ring 66, spacer ring 67A, spacer ring retainer 67B, and backup ring 68 are sometimes collectively referred to as the rings.

[0030] The seal ring 66 is provided to hermetically seal the space between the outer tip 61 and the plunger sleeve 21. A gap is formed at the joint of the seal ring 66. As an example, the seal ring 66 includes a seal medium storage groove 66A provided along the entire circumferential surface and recessed inward in the radial direction RD, and a first seal medium passage 66B, one end of which opens into the seal medium storage groove 66A and the other end which opens opposite the second supply passage 65B. The seal medium supplied from the seal medium supply pipe 5 is stored in the seal medium storage groove 66A through the first supply passage 65A, the second supply passage 65B, and the first seal medium passage 66B of the outer tip 61. The seal medium is also supplied to the outer surfaces of the spacer ring retainer 67B and the backup ring 68, thereby hermetically sealing the space between the rings fitted to the outer tip 61 and the plunger sleeve 21.

[0031] The spacer ring 67A is provided between the seal ring 66 and the backup ring 68, maintaining the distance between the seal ring 66 and the backup ring 68. The spacer ring 67A is formed in multiple parts in the circumferential direction, for example, in two sections. Therefore, by covering the spacer ring 67A from the periphery with the spacer ring retainer 67B, the multiple divided spacer rings 67A are held in the second holding part 63B.

[0032] The backup ring 68 is provided to restrict the movement of the seal ring 66 toward the rear R. The backup ring 68 is fixed in position between the spacer ring 67A, the spacer ring retainer 67B and the fixed flange 79 so that it cannot easily move in the longitudinal direction L.

[0033] The seal ring 66 has a joint, partly for the purpose of being assembled into the outer tip 61. When the seal ring 66 with this joint is assembled into the outer tip 61, the gap between the joints widens and the ring diameter increases. As a result, the seal ring 66 can adhere tightly to the inner circumferential surface of the plunger sleeve 21 due to its tension, thereby improving sealing performance. On the other hand, because the seal ring 66 with the joint has an elliptical shape, a gap is created between it and the perfectly circular outer tip 61. The spacer ring 67A is formed in a perfect circle, so it has better sealing performance with the outer tip 61 compared to the seal ring 66.

[0034] [Inner tip 71: Figure 3] The inner tip 71 is supported by the plunger rod 80 at the front F and is housed and held inside the outer tip 61. The inner tip 71 includes a cooling cylinder 72 which is positioned with a gap between it and the outer tip 61 at the front F and radial RD, a fitting cylinder 73 which is connected to the cooling cylinder 72 and fits with the outer tip 61 and the fixing flange 79, and an insertion sleeve 74 which is connected to the fitting cylinder 73 and inserted into the front F end of the plunger rod 80. The inner tip 71 includes a cooling water passage 75 which is connected to the plunger rod 80. The plunger tip 60 includes a cooling water passage 75 which includes a water supply passage 75A which sends cooling water supplied from the cooling water passage 84 of the plunger rod 80 toward the front F, and a drainage passage 75B which sends the cooling water that has cooled around the cooling cylinder 72 through the water supply passage 75A to the cooling water passage 84. Furthermore, in the inner chip 71, a cooling water channel 75C is provided on the outer circumference of the cooling cylinder 72 through which the supplied cooling water flows. The cooling water channel 75C is formed by grooves formed on the outer circumference of the cooling cylinder 72.

[0035] [Plunger rod 80: See Figures 2 and 3] The plunger rod 80 holds the plunger tip 60 at the front F. The plunger rod 80 comprises a cylindrical rod body 81 extending from the front F to the rear R, and a rod flange 82 that connects to the outer tip 61 via a fixed flange 79 provided at the front F end of the rod body 81. The plunger rod 80 also comprises a fitting groove 83 provided inside the rod flange 82 into which an insertion sleeve 74 is fitted, and a cooling water passage 84 formed around the central axis C of the rod body 81 and the rod flange 82.

[0036] The plunger rod 80 and the plunger tip 60 are connected as follows: The insertion sleeve 74 of the inner tip 71 is inserted and fitted into the fitting groove 83 of the rod body 81, and the fixing flange 79 is positioned in a fixed position around the fitting sleeve 64. As the fixing flange 79 and the rod flange 82 face each other, the fixing flange 79 and the rod flange 82 are fixed together with bolts B as fasteners. As mentioned above, the outer tip 61 and the fixing flange 79 are fixed together with bolts B, so the plunger tip 60 is fixed to the front end F of the plunger rod 80.

[0037] [Seal medium supply pipe 5: See Figures 2 and 3] The plunger 50 is equipped with a seal medium supply pipe 5 for supplying seal medium between the plunger tip 60 and the plunger sleeve 21 via a seal ring 66. The seal medium supply pipe 5 is fixed to the side surface of the rod body 81 so as to be parallel to the central axis C. In the seal medium supply pipe 5, a receiving port 5A for the seal medium is provided at one end of the rear R, and a discharge port 5B for the seal medium is provided at one end of the front F. The receiving port 5A is connected to, for example, an electric pump (not shown), and the required amount of seal medium is supplied to the receiving port 5A from this electric pump. The discharge port 5B is inserted into the rear R end of the seal medium supply passage 65 of the outer tip 61. As a result, a supply passage for seal medium is connected from the receiving port 5A of the seal medium supply pipe 5 through the discharge opening of the second supply passage 65B to the first seal medium passage 66B of the seal ring 66.

[0038] When the molten metal introduced into the plunger sleeve 21 is pushed by the plunger 50 and injected into the casting cavity CA of the mold, a sealing medium is supplied from the sealing medium supply pipe 5. The sealing medium is supplied in a fixed amount, for example, with each shot cycle. The sealing medium fills the sealing medium reservoir 66A of the sealing ring 66, thereby hermetically sealing the space between the outer tip 61 and the plunger sleeve 21. Therefore, even if the casting cavity CA is vacuum-suctioned by the vacuum suction unit 30 when the molten metal is injected into the casting cavity CA, the sealing performance between the outer tip 61 and the plunger sleeve 21 can be ensured.

[0039] Here, an example has been described in which the seal medium supply pipe 5 is provided outside the rod body 81. However, if the diameter of the rod body 81 is large, the seal medium supply passage may be formed inside the rod body 81. This seal medium supply passage is provided parallel to the cooling water passage 84.

[0040] [Procedure for attaching rings to the outer tip 61: See Figure 4] Next, the procedure for attaching rings to the outer tip 61 will be explained with reference to Figure 4. This procedure is carried out in the following order: attachment of the seal ring 66, attachment of the spacer ring 67A and spacer ring retainer 67B, and attachment of the backup ring 68. Note that the inner tip 71 is omitted in Figure 4.

[0041] [Installation of seal ring 66: ST01-ST02] The seal ring 66 is fitted into the first retaining portion 63A of the outer tip 61, which does not yet have any rings installed. The seal ring 66 is fitted into the first retaining portion 63A from the rear R towards the front F of the outer tip 61.

[0042] [Mounting of Spacer Ring 67A: ST03 - ST04] After mounting the seal ring 66, the spacer ring 67A is mounted (ST03). The inner diameter of the spacer ring 67A is set smaller than the outer diameter of the second holding portion 63B of the outer tip 61 on which it is to be mounted. Therefore, the spacer ring 67A has a split structure. Next, the spacer ring retainer 67B is mounted so as to be laminated on the spacer ring 67A. The spacer ring retainer 67B is a ring formed integrally without a joint. Therefore, the spacer ring retainer 67B is mounted from the rear R to the front F of the outer tip 61 so as not to interfere with the outer tip 61.

[0043] The spacer ring 67A is provided to fix the seal ring 66 and the backup ring 68 to be mounted later so that they do not move in the advancing direction of the plunger 50 due to the frictional force with the plunger sleeve 21. Also, the reason for making the spacer ring 67A have a split structure is not only for the convenience of mounting. That is, since both the seal ring 66 and the backup ring 68 have a structure with a joint, they become elliptical rather than circular because they tend to expand when mounted, and a slight gap is generated between them and the outer periphery of the outer tip 61 (the first holding portion 63A, the third holding portion 63C). Since the spacer ring 67A is machined into a perfect circle, the gap with the outer periphery is small and it is difficult for air to pass through. The spacer ring retainer 67B is mounted to fix the split - structured spacer ring 67A so that it does not expand in the radial direction.

[0044] [Mounting of Backup Ring 68: ST05 - ST06] If the spacer ring 67A and the spacer ring retainer 67B are mounted, then next, after fitting the backup ring 68 into the third holding portion 63C, with the fixing flange 79 abutted against the backup ring 68 and the outer tip 61, the fixing flange 79 and the rod flange 82 of the plunger rod 80 are fastened with bolts B. Thus, the mounting of the backup ring 68 is completed.

[0045] The above embodiment has shown the embodiment (the first embodiment) in which the seal ring 66 serves as the supply source of the seal medium. However, as will be described below, the supply source of the seal medium can also be configured as in the second embodiment or the third embodiment. The second embodiment or the third embodiment is the same as the first embodiment in that the seal medium is supplied toward the rings.

[0046] [Second Embodiment of the Supply Source of the Seal Medium: See FIGS. 5 and 6] In the second embodiment, a second seal medium passage 67C penetrating both of them is provided in the spacer ring 67A and the spacer ring retainer 67B disposed between the seal ring 66 and the backup ring 68. The second seal medium passage 67C communicates with the seal medium supply passage 65. In the second embodiment, the seal medium supplied through the second seal medium passage 67C passes through the outer peripheral surface of the spacer ring retainer 67B and the gaps at the joints of the adjacent seal ring 66 and backup ring 68, and is also supplied to the outer peripheral surfaces of the seal ring 66 and the backup ring 68. Thereby, the sealing performance between the plunger chip 60 and the plunger sleeve 21 can be improved. The backup ring 68 in the second embodiment functions as a seal ring.

[0047] [Third Embodiment of the Supply Source of the Seal Medium: See FIG. 7] In the third embodiment, without providing a seal medium passage in the rings, the seal medium is supplied into the gaps between the seal medium supply passage 65 (the first supply passage 65A, the second supply passage 65B, etc.) between the first holding portion 63A and the seal ring 66 and between the second holding portion 63B and the spacer ring 67A. Since the seal ring 66 is expanded in diameter by the pressure of the supplied seal medium, the outer peripheral surface of the seal ring 66 is pressed against the inner peripheral surface of the plunger sleeve 21, improving the sealing performance. In addition, the supplied seal medium fills the gap between the outer tip 61 and the seal ring 66, improving the sealing performance.

[0048] In the third embodiment shown in Figure 7, in addition to the second supply passage 65B for the seal ring 66, a third supply passage 65C corresponding to the spacer ring 67A is provided. When the sealing medium is supplied to the third supply passage 65C, the spacer ring 67A and the spacer ring retainer 67B are also pressed toward the inner circumferential surface of the plunger sleeve 21, thereby improving the sealing performance of that portion. In addition, the supplied sealing medium fills the gap between the spacer ring retainer 67B and the seal ring 66, thereby improving the sealing performance. Furthermore, as this sealing medium also moves toward the outer circumferential surface of the backup ring 68, the sealing performance between the backup ring 68 and the plunger sleeve 21 can be improved. In the third embodiment as well, the backup ring 68 functions as a seal ring.

[0049] [Comparison of the First to Third Embodiments] Of the first to third embodiments, the first embodiment is the most desirable from the viewpoint of rapid filling of the sealing medium. In the second embodiment, the sealing medium is supplied from a first sealing medium passage 67C provided in the spacer ring 67A. In this case, the process of supplying the sealing medium to the outer circumferential surface of the sealing ring 66 is as follows: first, the sealing medium is filled into the joint (not shown) of the sealing ring 66, and then the sealing medium is filled into the gap between the outer circumferential surface of the sealing ring 66 and the inner circumferential surface of the plunger sleeve 21. This is because the joint has a larger area through which the sealing medium passes, so the grease fills the joint preferentially. Therefore, compared to the first embodiment, the time it takes for the sealing medium to fill the sliding interface between the sealing ring 66 and the plunger sleeve 21 is longer. This is not a problem in the operating cycle of a normal die-casting machine, but in the case of a high-cycle machine with a short operating cycle, the configuration of the first embodiment may be required. In the third embodiment, the sealing medium is supplied from the second supply path 65B of the outer tip 61 through the space between the first retaining portion 63A and the sealing ring 66 to the sliding interface between the sealing ring 66 and the plunger sleeve 21. Therefore, in the third embodiment, the sealing performance is equivalent to that of the first embodiment, but the filling path of the sealing medium becomes longer, and the filling time becomes longer.

[0050] [Divided structure of outer chip 91 (fourth embodiment): See Figure 8] In the first to third embodiments, the outer chip 61 has an overall integrated structure, but as will be explained below, by making it a structure that can be divided in the direction of the central axis C, remarkable effects that cannot be obtained with an integrated structure can be obtained. The outer chip 91 according to the fourth embodiment consists of a chip head 92 and a chip body 96. The chip head 92 is positioned at the front F and the chip body 96 is positioned at the rear R.

[0051] The chip head 92 comprises a disc-shaped head body 93 and an annular ring support 94 that protrudes toward the rear R from near the periphery of the head body 93. The chip body 96 has a generally cylindrical shape and comprises a ring support 97 with a relatively small outer diameter and an outer shell structure 98 with a relatively large outer diameter. The radial RD dimension on the inner circumferential surface of the ring support 94 is the same as the radial RD dimension on the outer circumferential surface of the ring support 97. In addition, there is a difference in the radial RD dimension between the ring support 97 and the outer shell structure 98 to an extent corresponding to the thickness of the rings.

[0052] The chip head 92 and the chip body 96 are assembled such that the inner circumferential surface of the ring support 94 of the chip head 92 is in contact with the outer circumferential surface of the ring support 97 of the chip body 96. At this time, the front end F of the chip body 96 abuts against the chip head 92, and the rear end R of the chip body 96 abuts against the front wall F of the flange 113 of the inner chip 111.

[0053] With the outer chip 91 and inner chip 111 assembled, a seal ring 101 is mounted on the outer circumferential surface of the ring support 94 of the chip head 92. A spacer ring 102 and a split ring 104 are mounted on the outer circumferential surface of the ring support 97 of the chip body 96, and a backup ring 103 is mounted on the outer circumference of the spacer ring 102. The seal ring 101, backup ring 103, and split ring 104 have rectangular cross-sections, while the spacer ring 102 has an L-shaped cross-section. In this spacer ring 102, the portion 102A protruding in the radial direction RD is sandwiched between the seal ring 101 and the backup ring 103, thereby functioning as a spacer. The backup ring 103 is mounted on the outer circumference of portion 102B of the spacer ring 102. The split ring 104 is fixed to the chip body 96 by bolts B.

[0054] The plunger tip 110, having an outer tip 91 and an inner tip 111, is provided with a seal medium supply passage 65. The seal medium supply passage 65 is formed across the inner tip 111, the tip body 96, and the tip head 92, and includes a first supply passage 65A parallel to the central axis C and a second supply passage 65B intersecting the central axis C. The second supply passage 65B penetrates the ring support 94 and opens toward the inner circumferential surface of the seal ring 101. The seal ring 101 has the same inclination as the second supply passage 65B and is provided with a seal medium passage 101B that penetrates both the front and back surfaces of the seal ring 101. In addition, the outer surface of the seal ring 101 is provided with a seal medium storage groove 101A similar to that of the first embodiment.

[0055] In the plunger tip 110 described above, supplying a sealing medium via the sealing medium supply passage 65 ensures sealing performance between the plunger tip 110 and the plunger sleeve 21, and also guarantees sliding performance between the plunger tip 110, including the rings, and the plunger sleeve 21.

[0056] Furthermore, when replacing the rings after continued use of the plunger tip 110, the bolt B is removed. This allows the seal ring 101, spacer ring 102, and backup ring 103 to be removed.

[0057] [Seal performance evaluation: See Figures 9, 10, and 11] Next, the seal performance was measured and evaluated using the plunger tip 60 and the like according to the first embodiment. The results are shown in Figures 10 and 11. Figure 10 shows the average value of multiple measurement results, and Figure 11 shows each of the multiple measurement results.

[0058] The sealing performance was measured using the experimental apparatus 120 shown in Figure 9, in roughly the following manner. Note that components identical to those in the die-casting apparatus 1 shown in Figure 1 are denoted by the same reference numerals in Figure 9 as in Figure 1. A plunger tip 60 according to the first embodiment was inserted into a plunger sleeve 21 with one end sealed, and 2.6 kg of aluminum alloy ADC 12, heated to 700°C and melted, was supplied from the hot water inlet 22. Half of the space SP formed between the plunger sleeve 21 and the plunger tip 60 was occupied by the molten aluminum alloy. This is called a 50% filling rate. The plunger tip 60, to which lubricating oil or grease had been supplied, was moved in the direction of the arrow in the figure, and immediately after the plunger tip 60 blocked the hot water inlet 22, the remaining space SP was evacuated with a vacuum pump 31. The space SP was reduced to 5 kPa at room temperature and maintained there. The change in atmospheric pressure of the space SP over time was measured after the pressure reducing valve 34 was opened.

[0059] Figure 10 shows the pressure in the space SP from the time the pressure is reduced to 5 kPa until 30 seconds have elapsed. The breakdown of the first example, second example, third example, first comparative example, and second comparative example in Figures 10 and 11 is as follows.

[0060] First embodiment (EX1): Plunger tip 60; first embodiment, sealing medium; grease Second embodiment (EX2): Plunger tip 60; first embodiment, sealing medium; high viscosity lubricant First comparative example (CE1): Plunger tip; first embodiment, sealing medium: high viscosity lubricant Second comparative example (CE2): Plunger tip; no rings, sealing medium; grease Third comparative example (CE3): Plunger tip; no rings, sealing medium; high viscosity lubricant *EX1, EX2: Sealing medium supplied from sealing medium supply pipe 5 *CE1 to CE3: Sealing medium dripped from hot water inlet 22 toward plunger tip

[0061] As shown in Figure 10, the first embodiment (EX1) and the second embodiment (EX2) showed a suppression of the pressure rise inside the plunger sleeve 21 after the start of vacuuming compared to the second comparative example (CE2) and the third comparative example (CE3), confirming that they have superior sealing performance. The second comparative example (CE2) and the third comparative example (CE3) returned to atmospheric pressure in less than 10 seconds. In contrast, the first embodiment (EX1) was able to maintain a vacuum of 10 kPa for more than 10 seconds, and the second embodiment (EX2) was able to maintain a vacuum of 10 kPa for 5 seconds. In the operation of a normal die-casting apparatus, the time from vacuuming to the completion of injection is 5 seconds or less, so the second embodiment (EX2) also has sufficient sealing performance if there is no abnormal operation.

[0062] The first comparative example (CE1), as shown in Figure 10, can be said to have sufficient sealing performance compared to the second example (EX2). However, referring to Figure 11, the first comparative example (CE1) is not suitable for actual casting production because the sealing performance measured varies greatly.

[0063] [About the type of sealing medium] High-viscosity lubricants are used as sealing mediums. Lubricants are classified into liquid lubricants (lubricating oils), semi-solid lubricants (greases, compounds), and solid lubricants depending on their form, and the present invention can be applied to any form of lubricant. The sealing medium used in the examples is a high-viscosity lubricant consisting of grease and liquid. Grease is a type of lubricant that is semi-solid or solid in nature, made by adding thickeners and additives to a base oil made from mineral oil or synthetic oil. Grease remains stationary and does not flow like lubricating oil unless external force is applied, but it has the property of flowing when external force is applied, such as by stirring. In the present invention, it is preferable to use a hard grease with a consistency of No. 2 or higher according to the JIS classification. Alternatively, a grease with a consistency of No. 1 or lower according to the JIS classification is also acceptable if it contains a dispersant such as graphite. The base oil in the grease can be of any type, such as mineral oil or synthetic oil such as poly-αolefin. Furthermore, the type of thickener is not limited; it can be a soap fiber such as lithium stearate, an aluminum compound, or an organically modified layered silicate with a flaky structure called clay.

[0064] Preferably, a plunger lubricant with a viscosity exceeding 100 mPa·s (30°C) is used as the high-viscosity lubricant. Known plunger lubricants include water-soluble (white / black) types, oil-based non-pigment types, oil-based (white / black) types, and powder lubricants, but any type may be used as the high-viscosity lubricant in this invention. However, it is recommended that the viscosity exceed 100 mPa·s (30°C), and more preferably exceed 500 mPa·s (30°C).

[0065] [Regarding the amount of sealing medium supplied] If the amount of sealing medium supplied is too little, the sealing performance and lubrication effect at the sliding boundary between the outer tip 61 and the plunger sleeve 21 will be insufficient. On the other hand, if there is too much, it may be discharged outside the system and contaminate the area around the device, and may also degrade the quality if it enters the die-casting. According to the inventors' studies, for example, the volume V (mm) of the sealing medium storage groove 66A in the first embodiment ３ ) The amount of sealing medium supplied is V (mm３ ) may be insufficient, and it is preferable to supply a sealing medium of 2V or higher.

[0066] [Supplying device 130: See Figure 12] Next, a supplying device 130 preferred for supplying a high-viscosity sealing medium, such as grease, to the sealing medium supply pipe 5 will be described. As shown in Figure 12, the supplying device 130 includes a tank 131 for storing the sealing medium, a pressure pump 133 for sucking in and discharging the sealing medium stored in the tank 131, and a metering pump 135 for discharging the sealing medium supplied from the pressure pump 133 as a predetermined amount. The supplying device 130 also includes a medium supply pipe 137 through which the sealing medium flows to the sealing medium supply pipe 5 via the tank 131, the pressure pump 133, and the metering pump 135, and an on-off valve 139 that opens and closes according to the pressure of the sealing medium in the medium supply pipe 137 between the pressure pump 133 and the metering pump 135. The supplying device 130 includes a controller 141 that controls the operation of the pressure pump 133, the metering pump 135, and the on-off valve 139.

[0067] The metering pump 135 comprises a media passage 135A that forms part of the media supply pipe 137, a cylinder 135B connected to the media passage 135A, and a piston 135C that reciprocates within a cavity 135E inside the cylinder 135B. Check valves 135D, 135D are provided in the media passage 135A on the upstream and downstream sides of the connection portion with the cylinder 135B.

[0068] For example, lubricating oil can be delivered to the desired destination by gravity, but semi-solid lubricants such as grease and solid lubricants cannot be supplied by gravity. Furthermore, since the suction of the metering pump 135 alone is insufficient, the supply device 130 uses a pressure pump 133 to suck the sealing medium from the tank 131 and discharge it toward the metering pump 135.

[0069] For example, grease supplied by the pressure pump 133 is sent to the seal medium supply pipe 5 in a predetermined amount by the metering pump 135. Here, as described above, for example, the volume V (mm²) of the seal medium storage groove 66A ３For example, it is desirable to supply only 2V of sealing medium to the supply device 130. Therefore, in the supply device 130, a predetermined amount of sealing medium is sent to the sealing medium supply pipe 5 using a metering pump 135. When a predetermined amount of sealing medium is discharged by the metering pump 135 and sent to the sealing medium supply pipe 5, the on / off valve 139 is closed (OFF).

[0070] When the sealing medium is discharged from the metering pump 135, the piston 135C of the metering pump 135 moves downward in the direction of the black arrow to supply the next sealing medium, creating negative pressure in the cavity 135E inside the cylinder 135B. The sealing medium is drawn into this negatively pressurized cavity 135E, but semi-solid lubricants such as grease and solid lubricants in this invention have high viscosity, so they need to be pumped by a pressurizing pump 133. However, when supplying to the metering pump 135, if the pressure becomes too high, the medium supply pipe 137 may not be able to withstand the high pressure. Therefore, in the supply device 130, in addition to providing an on-off valve 139 in the medium supply pipe 137, a pressure threshold Pt is set in the on-off valve 139 for the detected pressure Pd in ​​the medium supply pipe 137. When the detected pressure Pd reaches the pressure threshold Pt, the on-off valve 139 is opened (ON).

[0071] The controller 141 instructs the operation of the pressure pump 133 and the metering pump 135 in conjunction with the start of die casting, and the pressure pump 133 and the metering pump 135 operate according to this instruction. In addition to instructing the operation of the pressure pump 133 and the metering pump 135, the controller 141 also monitors the ON / OFF operation of the on / off valve 139. Although this example shows the pressure pump 133 connected to the tank 131, the metering pump 135 can also be supplied by other means. For example, by connecting an air pipe through which compressed air flows, which is installed in the factory, to the tank 131, the sealing medium can be supplied to the metering pump through the medium supply pipe 137. In this case, a high-viscosity lubricant with lower viscosity than grease is used as the sealing medium.

[0072] As explained above, by using the supply device 130, even if a semi-solid lubricant or a solid lubricant is used as the sealing medium, clogging of the sealing medium in the medium supply pipe 137 and damage to the medium supply pipe 137 can be prevented.

[0073] The embodiments described above are merely examples of how the present invention can be realized. Therefore, the technical scope of the present invention should not be interpreted as being limited by these embodiments. This is because the present invention can be implemented in various forms without departing from its gist or its main features. For example, not only for the purpose of obtaining a high vacuum, but also because the sealing time is extended according to the present invention, it is possible to set a longer vacuum evacuation time. This is effective for die-casting equipment such as the recent gigacast and megacast, which have cavity capacities that are orders of magnitude larger than conventional equipment.

[0074] 1 Die-casting apparatus 5 Seal medium supply pipe 5A Inlet 5B Outlet 10 Mold section 11 Ejector 12 Fixed mold 13 Movable mold 14 Gate 15 Runner 20 Injection section 21 Plunger sleeve 22 Hot water inlet 24 Injection cylinder 30 Vacuum suction section 31 Vacuum pump 32 Vacuum tank 33 Vacuum piping 34 Pressure reducing valve 50 Plunger 60 Plunger tip 61 Outer tip 62 Cap 63 Ring retaining cylinder 63A First retaining section 63B Second retaining section 63C Third retaining section 64 Fitting sleeve 65 Seal medium supply passage 65A First supply passage 65B Second supply passage 65C Third supply passage 66 Seal ring 66A Seal medium storage groove 66B First seal medium passage 67A Spacer ring 67C Second seal medium passage 68 Backup ring 71 Inner tip 72 Cooling cylinder 73 Fitting cylinder 74 Insertion sleeve 75 Cooling water passage 75A Water supply passage 75B Drainage passage 75C Cooling water passage 79 Fixing flange 80 Plunger rod 81 Rod body 82 Rod flange 83 Fitting groove 84 Cooling water passage 91 Outer tip 92 Tip head 93 Head body 94 Ring support 96 Tip body 97 Ring support 98 Outer shell structure 101 Seal ring 101A Seal medium storage groove 101B Seal medium passage 102 Spacer ring 102A Part 102B Part 103 Backup ring 104 Split ring 110 Plunger tip 111 Inner tip 113 Flange 120 Experimental apparatus 130 Supply device 131 Tank 133 Pressure pump 135 Metering pump 137 Medium supply pipe 139 On / off valve 141 Controller B Bolt C Center axis F Forward R Rearward L Longitudinal RD Radial SP Space CA Casting cavity

Claims

1. A plunger (50) comprising: a plunger tip (60) on which a seal ring (66), a spacer ring (67A), and a backup ring (68) are arranged in order from the front (F) on its outer circumference; a plunger rod (80) connected to the rear (R) of the plunger tip (60); and a seal medium supply passage (65) that supplies a seal medium through the plunger tip (60) to at least one of the seal ring (66), spacer ring (67A), and backup ring (68).

2. The plunger (50) according to claim 1, wherein the seal ring (66) comprises a first seal medium passage (66B) that is connected to the seal medium supply passage (65) and penetrates in the thickness direction, and an annular seal medium storage groove (66A) that is connected to the first seal medium passage (66B) and recessed from the outer surface of the seal ring (66).

3. The plunger (50) according to claim 1, comprising a spacer ring retainer (67B) stacked on the outside of the spacer ring (67A), the spacer ring (67A) and the spacer ring retainer (67B) having a second seal medium passage (67C) that is connected to the seal medium supply passage (65) and penetrates in the thickness direction, and each of the seal ring (66) and the backup ring (68) having a joint.

4. The plunger (50) according to claim 1, wherein the sealing medium supply passage (65) is on the outer circumferential surface of the plunger tip (60) and opens toward the sealing ring (66).

5. The plunger (50) according to claim 1, wherein the seal medium supply pipe (5) connected to the seal medium supply passage (65) is attached to the plunger rod (80).

6. The plunger tip (60) comprises a cylindrical outer tip (61) having a housing gap inside, and an inner tip (71) disposed in the housing gap of the outer tip (91), wherein the outer tip (91) comprises a tip head (92) and a tip body (96) that are separable in the direction of the central axis (C), the plunger (50) according to claim 1.

7. A sealing method between a plunger sleeve (21) and a plunger (50) according to any one of claims 1 to 6, which is provided reciprocally movably inside the plunger sleeve (21), wherein a sealing medium is supplied from the sealing medium supply passage (65).

8. A supply device (130) for supplying a seal medium to a seal medium supply pipe (5) in a die-casting apparatus comprising a plunger sleeve (21) and a plunger (50) according to any one of claims 1 to 6, which is provided inside the plunger sleeve (21) so as to be reciprocally movable, comprising: a tank (131) for storing the seal medium; a pressure pump (133) for sucking in and discharging the seal medium stored in the tank (131); and a metering pump (135) for discharging the seal medium discharged from the pressure pump (133) in a predetermined amount; A supply device (130) comprising: a medium supply pipe (137) through which the sealing medium flows to the sealing medium supply pipe (5) via the tank (131), the pressure pump (133), and the metering pump (135); and an on / off valve (139) provided in the medium supply pipe (137) between the pressure pump (133) and the metering pump (135), which opens and closes according to the pressure of the sealing medium inside the medium supply pipe (137).

Images