Injection device for a light metal injection molding machine

Abstract

In an injection device of a light metal injection molding machine including a melt tank that accumulates a quantity of melt exceeding a capacity that can be accumulated in a melting cylinder, it is desirable to prevent a liquid surface of the melt in the melt tank from fluctuating greatly due to the melt flowing backward from an injection cylinder. The injection device of the light metal injection molding machine of the present invention includes a melting cylinder that heats and melts a billet extruded along a cylinder hole and accumulates the melt; an injection cylinder that injects the melt supplied from the melting cylinder due to free fall caused by gravity through an openable and closable communication path using an interposed plunger; and a melt tank that causes a melt supply discharge outlet connected to the melting cylinder to open at a position in the melting cylinder that does not face an opening surface of the melting cylinder side of the communication path.

Description

TECHNICAL FIELD

[0001] The present application relates to an injection device of a light metal injection molding machine. BACKGROUND

[0002] A light metal injection molding machine includes an injection device, a mold clamping device, and a control device that controls these devices. The injection device heats and melts a light metal material into a melt, and injects the melt into a mold device. The mold clamping device mounts the mold device, opens and closes the mold device, and clamps the mold. The melt is solidified by cooling in the mold device to become a molded product. The light metal material is, for example, a magnesium alloy or an aluminum alloy.

[0003] The injection device of the light metal injection molding machine of Patent Literature 1 and Patent Literature 2 includes a melting unit that heats and melts a light metal material in a cylindrical short rod shape into a melt, an injection unit that injects the melt supplied from the melting unit, and a connecting member that is formed with a communication path that communicates the melting unit and the injection unit. The melting unit is disposed above the injection unit. The light metal material in a cylindrical short rod shape is, for example, referred to as a billet.

[0004] The melting unit includes a horizontally disposed melting cylinder. The melting cylinder is connected at a front side portion and a lower side portion with a communication path that communicates with an injection cylinder, and supplies the billet from an opening of a rear end face in order. The melting cylinder is configured to forcibly melt the billet as it moves from the rear end toward the front end by controlling the heating temperature based on a plurality of heaters. The melting cylinder accumulates the melt of the light metal material that has been heated and melted. The billet has an outer diameter that is slightly smaller than the inner diameter of the rear end portion of the melting cylinder. The rear end portion of the melting cylinder and the billet are sealed by a sealing member that is a solidified product of the melt in a softened state to some extent and solidified to a degree that prevents back flow of the melt. The sealing member smoothly slides the billet that is moving forward.

[0005] The injection unit includes a transverse injection cylinder. The injection cylinder is connected at a front side portion and an upper side portion to a communication passage that communicates with a melting cylinder, and is connected at a front end portion to an injection nozzle. A plunger is housed in the injection cylinder in such a manner that the plunger is inserted into a cylinder hole from an opening of a rear end face of the injection cylinder. In addition, in the injection cylinder, an injection chamber surrounded by the cylinder hole and a front end face of the plunger is formed. The injection unit, after forming the injection chamber of a prescribed volume by moving the plunger to a prescribed position, measures the molten metal in such a manner that the molten metal supplied from the melting cylinder to the injection cylinder by free fall due to the weight of the molten metal through the communication passage is accumulated in the injection chamber, and advances the plunger to inject the molten metal in the injection chamber through the injection nozzle. The outer diameter of the plunger is slightly smaller than the inner diameter of the rear end portion of the injection cylinder. The rear end portion of the injection cylinder and the plunger are sealed by a sealing member that is a solidified product of the molten metal in a softened state to some extent and solidified to a degree that prevents backflow of the molten metal. The sealing member smoothly slides the plunger that moves forward and backward.

[0006] In addition, the injection device of the light metal injection molding machine of Patent Literature 1 and Patent Literature 2 includes a backflow prevention device that opens the communication passage when the molten metal is measured, and closes the communication passage when the molten metal is injected; an inert gas accumulation portion that accumulates the molten metal in an amount exceeding the capacity that can be accumulated in the melting cylinder, and makes the upper portion of the accumulated molten metal an environment of inert gas; a liquid level detection device that detects the liquid level of the molten metal in the inert gas accumulation portion; and an inert gas supply device that supplies inert gas to the inert gas accumulation portion.

[0007] The backflow prevention device includes a valve seat formed around the opening of the communication passage on the melting cylinder side, and a valve stem that advances and retreats in such a manner that the communication passage is closed by the valve stem being seated in the valve seat and the front end portion being seated in the valve seat in the inert gas accumulation portion and the melting cylinder, and the communication passage is opened by the front end portion being away from the valve seat. The backflow prevention device prevents the molten metal from flowing backward from the injection cylinder to the melting cylinder by closing the communication passage when the molten metal is injected.

[0008] The inert gas accumulation portion is one of the molten metal tanks that accumulates the molten metal in an amount exceeding the capacity that can be accumulated in the melting cylinder. The inert gas accumulation portion is connected to the upper portion of the opening of the communication passage on the melting cylinder side in the melting cylinder, and communicates with the melting cylinder. Therefore, when the molten metal in the melting cylinder is supplied to the injection cylinder by free fall due to the weight, the molten metal in the inert gas accumulation portion is supplied to the melting cylinder by free fall due to the weight. The inert gas accumulation portion is formed with a gas supply port and a gas discharge port in the upper portion. The gas supply port is connected to the inert gas supply device. The gas discharge port is connected to a pressure adjusting valve such as a relief valve. In the inert gas accumulation portion, the upper portion of the accumulated molten metal is maintained as an environment of inert gas at a prescribed pressure.

[0009] A liquid level detecting device is installed in the inert gas accumulation section. The liquid level detecting device is connected to the control device and outputs a signal indicating the liquid level of the molten metal accumulated in the inert gas accumulation section to the control device. The control device controls the timing of supplying the billet to the melting cylinder of the melting unit based on the output signal of the liquid level detecting device.

[0010] [Related Art Documents]

[0011] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent No. 6544875

[0013] [Patent Document 2] Japanese Patent No. 6590425 SUMMARY

[0014] [Problems to be Solved by the Invention]

[0015] An injection device of a light metal injection molding machine is structured such that a molten metal tank is connected to a melting cylinder and a backflow preventing device is installed at an opening of the injection cylinder side of a communication passage and at the middle of the communication passage. In this injection device, for example, the backflow preventing device is structured such that a valve seat is formed around the opening of the injection cylinder side of the communication passage and a valve rod passes through the injection cylinder and seats at the valve seat to close the communication passage and moves away from the valve seat to open the communication passage.

[0016] In this way, the molten metal tank is connected to the melting cylinder and the backflow preventing device is installed at the opening of the injection cylinder side of the communication passage and at the middle of the communication passage. Therefore, for example, when the valve rod seats at the valve seat due to wear or the like of the valve rod and the valve seat, if a gap is generated between the valve rod and the valve seat, there is a risk that the molten metal subjected to the injection pressure in the melting cylinder will backflow to the melting cylinder through the communication passage when the molten metal is injected. The backflowing molten metal travels straight in the communication passage and travels straight into the molten metal tank connected directly above the opening of the melting cylinder side of the communication passage, thereby greatly fluctuating the liquid level of the molten metal accumulated in the molten metal tank.

[0017] The greatly fluctuating liquid level of the molten metal accumulated in the molten metal tank has a risk of becoming an obstacle when the liquid level of the molten metal is detected by the liquid level detecting device. In addition, if the liquid level of the molten metal accumulated in the molten metal tank greatly fluctuates, there is a risk that the molten metal will adhere to the liquid level detecting device, the gas supply port, and the gas discharge port. The molten metal adhering to the liquid level detecting device has a risk of becoming an obstacle when the liquid level of the molten metal is detected by the liquid level detecting device. The molten metal adhering to the gas supply port has a risk of becoming an obstacle when the inert gas is supplied. The molten metal adhering to the gas discharge port has a risk of becoming an obstacle when the inert gas is discharged.

[0018] In view of the problems described above, it is a main object of the present application to provide an injection device of a light metal injection molding machine which, in the case where a molten metal tank which accumulates a quantity of molten metal exceeding the capacity that can be accumulated in a melting cylinder is included, can prevent the molten metal in the molten metal tank from greatly fluctuating due to the molten metal that has flowed back from the injection cylinder through the communication path and the melting cylinder when the molten metal is injected. Other objects or advantages of the present application will be described in the following description.

[0019] [Technical means for solving the problems]

[0020] The injection device of a light metal injection molding machine of the present application includes: a melting unit which heats and melts a light metal material in the form of a cylindrical short rod that is sequentially supplied into a melting cylinder along a cylinder hole from an opening of a rear end surface of the melting cylinder into molten metal, and accumulates the molten metal in the melting cylinder; an injection unit which accumulates the molten metal supplied into an injection cylinder due to free fall by gravity from the melting cylinder in the injection cylinder, and injects the molten metal accumulated in the injection cylinder using a plunger that can be movably inserted in the injection cylinder; a connecting member which connects the melting unit and the injection unit, and forms a communication path that communicates the melting cylinder and the injection cylinder; a molten metal tank which is formed with a molten metal supply / discharge port that discharges the molten metal, and is connected to the melting cylinder with the molten metal supply / discharge port being provided at a position other than a position where an opening surface of the melting cylinder side of the communication path faces, in the melting cylinder, and accumulates the molten metal in a quantity exceeding the capacity that can be accumulated in the melting cylinder; and a backflow prevention device which opens and closes the communication path.

[0021] [Effects of the invention]

[0022] The injection device of a light metal injection molding machine of the present application, when a molten metal tank which accumulates a quantity of molten metal exceeding the capacity that can be accumulated in a melting cylinder is included, can prevent the liquid surface of the molten metal accumulated in the molten metal tank from greatly fluctuating due to the molten metal that has flowed back from the injection cylinder through the communication path and the melting cylinder when the molten metal is injected. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a cross-sectional view showing the basic structure of the injection device of a light metal injection molding machine of the present application.

[0024] Figure 2 is a cross-sectional view showing another structure of the injection device of a light metal injection molding machine of the present application.

[0025] [Explanation of symbols]

[0026] 1: Injection device of light metal injection molding machine, injection device

[0027] 2: Melting unit

[0028] 3: Injection unit

[0029] 4: Connecting member

[0030] 5: Backflow prevention device

[0031] 6: Molten metal tank

[0032] 6a: Molten metal supply discharge port

[0033] 7: Liquid level detecting device

[0034] 8: Inert gas supply device

[0035] 20: Melting cylinder

[0036] 21: Reduced diameter portion

[0037] 21a: Opening of rear end surface of melting cylinder

[0038] 22: Light metal material, billet in cylindrical short rod shape

[0039] 23: Billet extruding device

[0040] 30: Injection cylinder

[0041] 30a: Injection chamber

[0042] 31: Reduced diameter portion

[0043] 31a: Opening of rear end surface of injection cylinder

[0044] 32: Plunger

[0045] 33: Plunger driving device

[0046] 34: Coupler

[0047] 35: Injection nozzle

[0048] 40: Communication path

[0049] 40a: Opening of melting cylinder side of communication path

[0050] 40b: Opening of injection cylinder side of communication path

[0051] 51: Valve seat

[0052] 52: Valve stem

[0053] 53: Valve stem driving device

[0054] 61: Main body member

[0055] 62: lid member

[0056] 62a: gas supply port

[0057] 62b: gas exhaust port

[0058] 63: molten metal dispersing member

[0059] 63a: through hole

[0060] 71: upper limit level sensor

[0061] 72: lower limit level sensor DETAILED DESCRIPTION

[0062] A light metal injection molding machine includes an injection device, a mold clamping device, and a control device that controls these devices. The injection device is shown, for example, in Figure 1 and Figure 2 . Figure 1 A basic structure of the injection device 1 of the light metal injection molding machine of the present application is shown. Figure 2 Another structure of the injection device 1 of the light metal injection molding machine of the present application is shown. The mold clamping device and the control device are omitted from the drawing. The mold clamping device mounts a mold device, and opens and closes the mold device or clamps the mold. The mold device, which is omitted from the drawing, has a fixed-side mold and a movable-side mold, for example. Further, the driving sources that drive various devices are not described in detail, but various types of driving sources such as oil pressure type, air pressure type, or electric type are appropriately used.

[0063] The light metal injection molding machine closes the mold device by the mold clamping device, and further clamps the mold, injects and fills a molten metal material into a cavity space in the mold device by the injection device 1, and cools and solidifies the molten metal material in the mold device. After that, the mold is opened by the mold clamping device, and a molded product is taken out.

[0064] The light metal injection molding machine of the embodiment has a structure of an injection molding machine that is suitable for a light metal material as a molding material. The light metal material in the present application refers to a metal having a specific gravity of 4 or less. In practice, a light metal material such as aluminum and magnesium is effective as a molding material. In the case where the molding material is aluminum, a portion that contacts the molding material is coated with a cermet-based material so as not to be damaged by melting.

[0065] Figure 1The injection device 1 of the light metal injection molding machine of the illustrated embodiment includes a melting unit 2 having a melting cylinder 20, an injection unit 3 having an injection cylinder 30, a connecting member 4 formed with a communication path 40 that communicates between the melting cylinder 20 and the injection cylinder 30, and a backflow prevention device 5 that opens and closes the communication path 40. Various driving devices and various sensors included in the melting unit 2, the injection unit 3, and the backflow prevention device 5 are connected to a control device to control various operations.

[0066] In addition, Figure 1 The injection device 1 illustrated includes a molten metal tank 6 connected to the melting cylinder 20 that accumulates molten metal exceeding the capacity that can be accumulated in the melting cylinder, and a liquid level detecting device 7 that detects the liquid level of the molten metal in the molten metal tank 6. The liquid level detecting device 7 is connected to the control device.

[0067] In addition, Figure 1 The injection device 1 illustrated further includes an inert gas supply device 8, not shown, that supplies inert gas above the molten metal accumulated in the molten metal tank 6. The inert gas supply device 8 can also be connected to the control device to control various operations.

[0068] At least one heater is wound around each of the melting cylinder 20, the injection cylinder 30, the connecting member 4, and the molten metal tank 6. In the case where the melting cylinder 20 is connected to the molten metal tank 6 by a connecting pipe, not shown, at least one heater is also wound around the outer periphery of the connecting pipe. In addition, at least one heater is also wound around the injection nozzle 35 described later.

[0069] The melting cylinder 20, the injection cylinder 30, and the communication path 40 are arranged and connected in such a manner that the molten metal in the melting cylinder 20 can flow into the injection cylinder 30 through the communication path 40 due to free fall caused by gravity. The melting cylinder 20 and the molten metal tank 6 are arranged and connected in such a manner that the molten metal in the molten metal tank 6 can flow into the melting cylinder 20 through a molten metal supply discharge port 6a described later due to free fall caused by gravity.

[0070] The melting unit 2 heats and melts the light metal material 22 (hereinafter referred to as a billet 22) in the form of a cylindrical short rod that is sequentially supplied into the melting cylinder 20 from the opening 21a of the rear end surface of the melting cylinder 20 along the cylinder hole, into the molten metal in the melting cylinder 20, and accumulates the molten metal in the melting cylinder 20. Furthermore, the molten metal tank 6 described later is connected to the melting cylinder 20, so even after the molten metal accumulated in the melting cylinder 20 reaches the capacity of the molten metal that can be accumulated in the melting cylinder 20, the billet 22 is further sequentially supplied into the melting cylinder 20, and the molten metal exceeding the capacity that can be accumulated in the melting cylinder 20 can be supplied into the molten metal tank 6 in such a manner that it is squeezed out of the melting cylinder 20.

[0071] The melting unit 2 has a melting cylinder 20 and a billet extruding device 23 for extruding a billet 22 into the melting cylinder 20. Figure 1 The illustrated melting cylinder 20 is arranged above the injection cylinder 30 in a manner that the center axis of the cylinder hole becomes horizontal. In other words, Figure 1 The illustrated melting cylinder 20 is arranged above the injection cylinder 30 in a manner that the center axis of the cylinder hole becomes horizontal. In other words,

[0072] The melting cylinder 20 forcibly heats the billet 22 with a heater as it advances from the rear end toward the front end. For example, by arranging a plurality of heaters in series from the rear end toward the front end of the melting cylinder 20, the heating temperature of each portion of the melting cylinder 20 can be controlled individually. The melting cylinder 20 accumulates the melt of the light metal material after heating and melting.

[0073] The billet 22 is a cylindrical short rod shape of a prescribed length and a prescribed outer diameter, and is extruded into the melting cylinder 20 in order from the opening 21a of the rear end face of the melting cylinder 20. The billet 22 is heated and melted into a melt as it advances in the heated melting cylinder 20 while the temperature rises. The billet 22 is gradually heated and melted into a melt from the outside in the melting cylinder 20, for example, before reaching the vicinity of the center of the melting cylinder 20, and is completely heated and melted into a melt when reaching the vicinity of the center of the melting cylinder 20. The softened portion of the billet 22 before melting expands in diameter by advancing. The expanded portion of the billet 22 slidably abuts against the cylinder hole of the melting cylinder 20, and seals between the melting cylinder 20 and the billet 22.

[0074] The inner diameter of the cylinder hole of the melting cylinder 20 is smaller at the rear end portion than at other portions and is larger than the outer diameter of the billet 22. Figure 1 The illustrated melting cylinder 20 has a reduced diameter portion 21 at the rear end portion. At this time, the opening 21a of the rear end face of the melting cylinder 20 is the opening of the rear end face of the reduced diameter portion 21. The inner diameter of the reduced diameter portion 21 is smaller than the inner diameter of the cylinder hole of the melting cylinder 20 and is larger than the outer diameter of the billet 22. The melting cylinder 20 and the reduced diameter portion 21 can also be formed integrally.

[0075] For the melting cylinder 20, Figure 1 For the illustrated melting cylinder 20, the temperature of the rear end portion is controlled by the heater, and a sealing member is generated between the reduced diameter portion 21 and the billet 22, which is a solidified product of the melt in a softened state to some extent and solidified to the extent of preventing backflow of the melt. The sealing member seals between the rear end portion of the melting cylinder 20 and the billet 22 to prevent leakage of the melt. The sealing member reduces the friction between the melting cylinder 20 and the billet 22 to enable the billet 22 to move smoothly. Furthermore, the melting cylinder 20 can also include a cooling device not shown in the rear end portion, and the rear end portion is controlled by the heater and the cooling device in a prescribed heating temperature.

[0076] The sealing member is caught on a step formed between the annular groove of the inner peripheral surface of the reduced diameter portion 21 or the cylinder hole of the melting pot 20 and the reduced diameter portion 21, and thus does not come off from the rear end portion of the melting pot 20 even if subjected to the pressure of the molten metal. Further, the billet 22 can be supplied to the melting pot after being preheated by a preheating device not shown. The preheated billet 22 is rapidly heated to a temperature at which it is melted into a molten metal after passing through the reduced diameter portion 21.

[0077] The molten metal supplied from the melting pot 20 through the communication path 40 by free fall due to its own weight into the injection cylinder 30 is accumulated in the injection cylinder 30, and the molten metal accumulated in the injection cylinder 30 is injected by the plunger 32 which is capable of being inserted in the injection cylinder 30 so as to move forward and backward.

[0078] The injection unit 3 includes the injection cylinder 30, an injection nozzle 35 mounted to the front end portion of the injection cylinder 30, the plunger 32 which is inserted into the cylinder hole from the opening 31a of the rear end surface of the injection cylinder 30 and moves forward and backward in the injection cylinder 30, and a plunger drive device 33 for driving the plunger 32. Figure 1 The injection cylinder 30 shown is horizontally arranged below the melting pot 20. Figure 1 The injection cylinder 30 shown is arranged below the melting pot 20, and is arranged so that the axial direction of the central axis of the cylinder hole becomes the horizontal direction. The plunger 32 is connected to the drive shaft of the plunger drive device 33 via the coupling 34.

[0079] In the injection cylinder 30, an injection chamber 30a which is an internal space surrounded by the cylinder hole and the front end surface of the plunger 32 is formed. The volume of the injection chamber 30a becomes smaller as the plunger 32 advances, and becomes larger as the plunger 32 retreats. The plunger 32 is moved to a prescribed position in advance before the molten metal is supplied, so that the volume of the injection chamber 30a becomes a volume required for metering. The molten metal in the melting pot 20 flows into the injection chamber 30a which becomes a prescribed volume by free fall due to its own weight through the communication path 40, and is metered by filling the injection chamber 30a. The molten metal in the injection chamber 30a is injected into the mold device from the injection nozzle 35 by the advancement of the plunger 32. At the time of injection of the molten metal, the injection nozzle 35 abuts against the mold device to communicate the cavity space in the mold device with the injection chamber 30a.

[0080] The molten metal accumulated in the injection cylinder 30 is heated, for example, by a heater to maintain the state of the molten metal. For example, a plurality of heaters are arranged in series from the rear end to the front end of the injection cylinder 30, and the heating temperature of each portion of the injection cylinder 30 can be controlled individually.

[0081] The inner diameter of the cylinder hole of the injection cylinder 30 is smaller at the rear end portion than at other portions, and is larger than the outer diameter of the plunger 32. Figure 1The illustrated injection cylinder 30 has a reduced diameter portion 31 at the rear end portion. At this time, the opening 31a of the rear end face of the injection cylinder 30 is the opening of the rear end face of the reduced diameter portion 31. The inner diameter of the reduced diameter portion 31 is smaller than the inner diameter of the cylinder hole of the injection cylinder 30 and larger than the outer diameter of the plunger 32. The injection cylinder 30 and the reduced diameter portion 31 can also be integrally formed.

[0082] Figure 1 In the illustrated injection cylinder 30, the temperature of the rear end portion is controlled by a heater, and a sealing member is generated between the reduced diameter portion 31 and the plunger 32, which is a solidified product of the molten metal in a softened state to some extent and solidified to an extent that prevents backflow of the molten metal. The sealing member seals between the rear end portion of the injection cylinder 30 and the plunger 32 to prevent leakage of the molten metal. The sealing member reduces friction between the injection cylinder 30 and the plunger 32 to enable smooth movement of the plunger 32. The sealing member is caught on an annular groove formed on the inner circumferential surface of the reduced diameter portion 31 or a step difference between the cylinder hole of the injection cylinder 30 and the reduced diameter portion 31, so that it does not come off from the rear end portion of the injection cylinder 30 even if it is subjected to the pressure of the molten metal. In addition, the injection cylinder 30 can also include a cooling device at the rear end portion, and the rear end portion is controlled to a predetermined heating temperature by the heater and the cooling device.

[0083] The connecting member 4 connects the melting unit 2 and the injection unit 3, and a communication passage 40 that communicates between the melting cylinder 20 and the injection cylinder 30 is formed. For example, Figure 1 In the illustrated connecting member 4, the end portion on the melting unit 2 side is connected to the front side portion and the lower side portion of the melting cylinder 20, and the end portion on the injection unit 3 side is connected to the front side portion and the upper side portion of the injection cylinder 30. For example, Figure 1 One end of the illustrated communication passage 40 is connected to the front side portion and the lower side portion in the melting cylinder 20, and the other end is connected to the front side portion and the upper side portion in the injection cylinder 30. In addition, the portions of the melting cylinder 20 and the injection cylinder 30 to which the communication passage 40 is connected are portions where the molten metal in the melting cylinder 20 can flow into the injection cylinder 30 through the communication passage 40 due to free fall caused by gravity.

[0084] For example, Figure 1 The opening 40a of the melting cylinder 20 side of the illustrated communication passage 40 is opened at the front side portion and the lower side portion of the cylinder hole of the melting cylinder 20. For example, Figure 1 The opening 40b of the injection cylinder 30 side of the illustrated communication passage 40 is opened at the front side portion and the upper side portion of the cylinder hole of the injection cylinder 30. In addition, the opening 40b of the injection cylinder 30 side of the communication passage 40 can also be configured to be opened in the cylinder hole of the injection cylinder 30 in such a manner that the end portion of the injection cylinder 30 side of the communication passage 40 penetrates the front side portion and the upper side portion of the cylinder hole of the injection cylinder 30 and protrudes into the cylinder hole of the injection cylinder 30.

[0085] The inner diameter of the communication path 40 can be formed to be a size that the molten metal in the melting pot 20 can be supplied into the injection pot 30 by free fall due to the weight, and that the area of the seal can be minimized when backflow is prevented by the backflow prevention device 5. The inner diameter of the communication path 40 can be, for example, 10 mm or more and 15 mm or less, and preferably 12 mm.

[0086] The backflow prevention device 5 opens and closes the communication path 40. The backflow prevention device 5 opens and closes the injection pot 30 side opening 40b of the communication path 40, the middle of the communication path 40, or the melting pot 20 side opening of the communication path 40. For example, the backflow prevention device 5 includes a valve seat 51 formed around the injection pot 30 side opening 40b of the communication path 40 that opens in the cylinder hole of the injection pot 30, a valve stem 52 that advances and retreats in a manner that closes the communication path 40 by seating in the valve seat 51 in the cylinder hole of the injection pot 30 and opens the communication path 40 by moving away from the valve seat 51, and a valve stem driving device 53 that moves the valve stem 52 toward and away from the valve seat 51.

[0087] In addition, for example, the backflow prevention device 5 can also be configured to provide various valves such as a rotary valve or a check valve in the middle of the communication path 40. In addition, for example, the backflow prevention device 5 can also be configured to form a valve seat around the melting pot 20 side opening 40a of the communication path 40, to seat the valve stem in the valve seat in the cylinder hole of the melting pot 20 to close the communication path 40, and to move the valve stem away from the valve seat to open the communication path 40.

[0088] Figure 1 The illustrated backflow prevention device 5 is provided with the valve stem driving device 53 below the injection pot 30. The valve stem 52 is provided to pass through the front and lower side portions of the injection pot 30 and is movable up and down in the cylinder hole. The valve seat 51 is formed around the injection pot 30 side opening 40b of the communication path 40 that opens in the front and upper side portions of the cylinder hole of the injection pot 30. The valve stem 52 is raised to seat in the valve seat 51 to close the communication path 40, and is lowered to move away from the valve seat 51 to open the communication path 40.

[0089] The valve stem 52 can also have a not-shown cooling pipe that circulates a cooling medium inside, for the purpose of cooling the front end of the valve stem 52. For example, the valve stem 52 can cool the front end portion just before seating in the valve seat 51, and a solidified product of the molten metal in a softened state to some extent can be formed around the front end portion. The solidified product of the front end of the valve stem 52 deforms like the valve seat 51 when the valve stem 52 seats in the valve seat 51, and leakage of the molten metal can be prevented by eliminating the gap between the valve stem 52 and the valve seat 51.

[0090] Further, the portion of the injection cylinder 30 through which the valve rod 52 penetrates can also have a cooling pipe not shown. The cooling pipe generates a sealing member that is a solidified product of the molten metal in a softened state to some extent between the portion of the injection cylinder 30 through which the valve rod 52 penetrates and the valve rod 52. The sealing member seals between the portion of the injection cylinder 30 through which the valve rod 52 penetrates and the valve rod 52 to prevent leakage of the molten metal, and reduces friction therebetween to allow smooth movement of the valve rod 52.

[0091] The molten metal tank 6 is formed with a molten metal supply discharge port 6a that supplies and discharges the molten metal, and the molten metal supply discharge port 6a is opened in the melting cylinder 20 and connected to the melting cylinder 20 in a manner communicating with the melting cylinder 20. The molten metal tank 6 accumulates the molten metal in an amount exceeding the capacity that can be accumulated in the melting cylinder 20.

[0092] The supply of the molten metal to the molten metal tank 6 is performed in such a manner that the billet 22 that is sequentially supplied in a manner of being extruded into the melting cylinder 20 along the cylinder hole from the opening 21a of the rear end face of the melting cylinder 20 is heated and melted to become the molten metal in the melting cylinder 20, and the molten metal is accumulated in the melting cylinder 20, and after the molten metal in the melting cylinder 20 reaches the capacity of the molten metal that can be accumulated in the melting cylinder 20, the supply and heating and melting of the billet 22 are continued, whereby the molten metal in an amount exceeding the capacity that can be accumulated in the melting cylinder 20 is extruded from the melting cylinder 20 through the molten metal supply discharge port 6a. The molten metal tank 6 can accumulate, for example, the molten metal in a so-called prescribed capacity such as a capacity required for injection molding at least once. Further, when the capacity of the molten metal accumulated in the melting cylinder 20 decreases, the molten metal tank 6 discharges the accumulated molten metal to the melting cylinder 20 through the molten metal supply discharge port 6a due to free fall by gravity.

[0093] For example, Figure 1 The molten metal tank 6 shown is disposed vertically above the melting cylinder 20. The molten metal tank 6 includes a cylindrical main body member 61 disposed in a manner that the axial direction of the center axis becomes the up-down direction, and a cover member 62 that covers the opening of the upper end face of the main body member 61. The opening of the molten metal supply discharge port 6a communicates with the main body member 61 and is opened in the lower end face of the main body member 61. The molten metal tank 6 can accumulate the molten metal in an amount exceeding the capacity that can be accumulated in the melting cylinder 20 in the internal space formed by the wall surface of the main body member 61 and the cover member 62. Here, the up-down direction refers to the direction perpendicular to the horizontal direction.

[0094] The portion of the molten metal tank 6 above the liquid level of the molten metal stored in the molten metal tank 6 is also maintained in an inert gas atmosphere by the inert gas supplied from the inert gas supply device 8. The inert gas is, for example, argon (Ar) or nitrogen (N2) or the like. The molten metal tank 6 can be formed with a gas supply port 62a and a gas exhaust port 62b at a position above the liquid level of the stored molten metal and at a position directly above the molten metal supply and discharge port 6a in the horizontal direction. The gas supply port 62a is connected to the inert gas supply device 8 and guides the inert gas to the portion above the liquid level of the molten metal in the molten metal tank 6. The gas exhaust port 62b exhausts the inert gas in the molten metal tank 6 to the outside.

[0095] Figure 1 The molten metal tank 6 is formed with the gas supply port 62a and the gas exhaust port 62b in the lid member 62. The inert gas supply device 8 is connected to the gas supply port 62a. The inert gas is supplied from the gas supply port 62a to the molten metal tank 6. The inert gas in the molten metal tank 6 is exhausted to the outside from the gas exhaust port 62b. The inert gas supply device 8 can also always supply a certain amount of inert gas to the molten metal tank 6 from the gas supply port 62a. The gas exhaust port 62b can be provided with a not-shown pressure adjusting valve for maintaining the gas pressure in the molten metal tank 6 at a prescribed pressure. The pressure adjusting valve is, for example, a pressure relief valve that opens and closes the gas exhaust port so that the pressure in the molten metal tank 6 does not exceed the prescribed pressure or the like.

[0096] The inert gas is supplied to and exhausted from the molten metal tank 6 in such a manner that the gas pressure becomes a pressure that does not interfere with the free fall of the molten metal in the molten metal tank 6 due to gravity and the discharge of the molten metal in the molten bath 20 to the molten metal tank 6 and the supply of the molten metal in the molten metal tank 6 to the molten bath 20.

[0097] The liquid level height of the molten metal stored in the molten metal tank 6 is detected by at least one liquid level detecting device 7. The liquid level detecting device 7 indirectly detects the volume of the molten metal stored in the molten metal tank 6. The liquid level detecting device 7 outputs a signal indicating the liquid level height to the connected control device. The liquid level detecting device 7 can employ various detection methods such as a contact type using a float, an electrode, an electrostatic capacitor or the like and a non-contact type using an ultrasonic wave, a laser or the like as long as it can detect the liquid level height of the molten metal in the molten metal tank 6. The liquid level detecting device 7 can also be a device that can detect that the liquid level of the molten metal is above or below a prescribed height. The liquid level detecting device 7 can also be a device that can detect any height of the liquid level of the molten metal.

[0098] Figure 1The liquid level detecting device 7 shown includes an upper limit level sensor 71 and a lower limit level sensor 72. The upper limit level sensor 71 and the lower limit level sensor 72 are, for example, contact type, and show ON when the molten metal is in contact with the front end portion, and show OFF when the molten metal is not in contact with the front end portion. The upper limit level sensor 71 and the lower limit level sensor 72 are installed to the lid member 62 of the molten metal tank 6 with the bases thereof arranged at different prescribed heights in the molten metal tank 6 with the front end portions thereof. The height of the front end portion of the upper limit level sensor 71 is installed higher than the height of the front end portion of the lower limit level sensor 72. Further, the liquid level detecting device 7 can be installed at a position directly above the molten metal supply discharge port 6a in the horizontal direction.

[0099] When the liquid level height of the molten metal in the molten metal tank 6 becomes a liquid level height indicating a capacity of the molten metal that can be accumulated in the molten metal tank 6 or more, the upper limit level sensor 71 shows ON. The control device, for example, is controlled so that when the upper limit level sensor 71 shows ON, if the billet 22 is being supplied to the molten cylinder 20, a prescribed action such as stopping the supply is performed. Also, for example, the control device can be controlled so that when the upper limit level sensor 71 shows ON, a warning is issued.

[0100] When the capacity of the molten metal in the molten metal tank 6 decreases to a liquid level height indicating a prescribed capacity or less, the lower limit level sensor 72 shows OFF. The control device, for example, is controlled so that when the output signal of the lower limit level sensor 72 shows OFF, before the molten metal in the molten cylinder 20 is supplied to the injection cylinder 30 by free fall due to gravity, the billet 22 is supplied to the molten cylinder 20 from the opening 21a of the rear end face of the molten cylinder 20, the billet 22 is heated and melted in the molten cylinder 20 to become molten metal, and the molten metal that exceeds the capacity that can be accumulated in the molten cylinder 20 is sent out to the molten metal tank 6, so that the molten metal is supplied to the molten metal tank 6 as in the range where the upper limit level sensor 71 shows OFF and the lower limit level sensor 72 shows ON.

[0101] Here, when the lower limit level sensor 72 is switched from ON to OFF, if the molten metal of the prescribed capacity is supplied to the molten metal tank 6, as long as it is known in advance that the situation is as in the range where the upper limit level sensor 71 shows OFF and the lower limit level sensor shows ON, the prescribed capacity that is set in advance can be supplied to the molten metal tank 6. The prescribed capacity, for example, is the capacity of the molten metal that is injected into the mold device by one injection molding, the capacity of the molten metal that is obtained by heating and melting one billet 22, or the capacity of the molten metal that is obtained by heating and melting 2.5 billets 22, and the like. In addition to this, for example, it can be configured to include another level sensor that detects a prescribed height of the liquid level of the molten metal between the upper limit level sensor 71 and the lower limit level sensor 72, and the molten metal is supplied to the molten metal tank 6 before the other level sensor shows ON.

[0102] Figure 1 The injection device 1 of the light metal injection molding machine of the illustrated embodiment operates in the following manner. Here, the molten metal has been accumulated in the melting pot 20 and the molten metal tank 6 in the preparation stage. At this time, the upper limit level sensor 71 shows off and the lower limit level sensor 72 shows on. The backflow prevention device 5 closes the communication path 40.

[0103] In the state where the backflow prevention device 5 has closed the communication path 40, the plunger 32 is moved to a prescribed position in the injection cylinder 30. The volume of the injection chamber 30a formed in the injection cylinder 30 becomes the volume required for metering. The molten metal in the melting pot 20 is supplied to the injection chamber 30a by free fall due to gravity through the communication path 40 by the backflow prevention device 5 opening the communication path 40. The molten metal is metered by the injection chamber 30a being filled with the molten metal. The backflow prevention device 5 closes the communication path 40. The plunger 32 advances and the molten metal in the injection chamber 30a is injected into the mold device through the injection nozzle 35.

[0104] The molten metal in the molten metal tank 6 is supplied to the injection chamber 30a by free fall due to gravity of the molten metal in the melting pot 20 and is discharged to the melting pot 20 by free fall due to gravity in an amount that is reduced. After performing at least one injection molding, in the case where the molten metal in the molten metal tank 6 is reduced and the lower limit level sensor 72 shows off, before performing the next injection molding, the melting pot 20 is supplied with the billet 22, the billet 22 is heated and melted to molten metal in the melting pot 20, the molten metal that exceeds the capacity that can be accumulated in the melting pot 20 is extruded to the molten metal tank 6, and thus the molten metal is supplied to the molten metal tank 6 as in the range where the upper limit level sensor 71 shows off and the lower limit level sensor 72 shows on.

[0105] Next, the structure of the present application is described in further detail.

[0106] The molten metal tank 6 is formed with a molten metal supply / discharge port 6a that supplies and discharges the molten metal, the molten metal supply / discharge port 6a is opened in the melting pot 20 at a position other than the position that faces the opening 40a of the melting pot 20 side of the communication path 40, and is connected to the melting pot 20 in a manner that communicates with the melting pot 20, and accumulates the molten metal in an amount that exceeds the capacity that can be accumulated in the melting pot 20. In addition, the position in the melting pot 20 where the molten metal supply / discharge port 6a is opened is a position other than the position that faces the opening 40a of the melting pot 20 side of the communication path 40, and is a position where the molten metal in the molten metal tank 6 can flow into the melting pot 20 by free fall due to gravity. Further, the inner diameter of the molten metal supply / discharge port 6a can be formed to be larger than the inner diameter of the communication path 40 and smaller than the inner diameter of the molten metal tank 6.

[0107] The molten metal tank 6 accumulates the molten metal in an amount exceeding the capacity that can be accumulated in the melting pot 20. The molten metal tank 6 is supplied with the molten metal in such a manner that the billet 22 is sequentially supplied into the melting pot 20 from the opening 21a of the rear end face of the melting pot 20 along the pot hole. The billet 22 is heated and melted in the melting pot 20 until it becomes the molten metal. The molten metal produced by heating and melting the billet 22 is accumulated in the melting pot 20. After the molten metal in the melting pot 20 reaches the capacity of the molten metal that can be accumulated in the melting pot 20, the supply and heating and melting of the billet 22 are continued. At this time, the molten metal in an amount exceeding the capacity that can be accumulated in the melting pot 20 is supplied into the molten metal tank 6 through the molten metal supply discharge port 6a in such a manner that the molten metal is discharged from the melting pot 20. The supply and heating and melting of the billet 22 are performed before the molten metal tank 6 accumulates the molten metal in a prescribed capacity when the molten metal is supplied to the molten metal tank 6. The molten metal tank 6 can accumulate, for example, the molten metal in a so-called prescribed capacity such as a capacity required for one or a plurality of injection molding. The molten metal tank 6 at the time of accumulation of the prescribed capacity can further accumulate the molten metal in an amount of backflow even when the molten metal in the injection cylinder 30 backflows into the melting pot 20 at the time of injection of the molten metal. In addition, when the capacity of the molten metal accumulated in the melting pot 20 decreases, the molten metal tank 6 discharges the accumulated molten metal into the melting pot 20 by free fall due to gravity through the molten metal supply discharge port 6a. The molten metal supply discharge port 6a can also include a connection pipe not shown that connects the melting pot 20 and the molten metal tank 6 and communicates between the melting pot 20 and the molten metal tank 6 and enables supply and discharge of the molten metal therebetween.

[0108] At the time of injection of the molten metal, even when the molten metal in the injection cylinder 30 backflows into the melting pot 20, the molten metal that straightly flows in the communication path 40 into the melting pot 20 changes the direction of flow in the melting pot 20 having a larger inner diameter than the communication path 40 to the axial direction of the melting pot 20 and further disperses in the melting pot 20 before flowing into the molten metal tank 6 to decelerate the flow rate. Thus, it is possible to prevent the liquid level of the molten metal accumulated in the molten metal tank from greatly fluctuating due to the backflow of the molten metal. In addition, if the inner diameter of the molten metal supply discharge port 6a is formed to be larger than the inner diameter of the communication path 40 and smaller than the inner diameter of the molten metal tank 6, it is possible to further prevent the liquid level of the molten metal accumulated in the molten metal tank from greatly fluctuating due to the backflow of the molten metal as described later.

[0109] Figure 1The molten metal tank 6 is disposed above the molten bath 20 in the horizontal direction above the opening 40a of the molten bath 20 side of the communication passage 40. The molten metal supply discharge port 6a of the molten metal tank 6 is opened in the upper side portion of the cylinder hole of the molten bath 20 in the horizontal direction above the opening 40a of the molten bath 20 side of the communication passage 40. Further, the inner diameter of the molten metal supply discharge port 6a is formed to be larger than the inner diameter of the communication passage 40 and smaller than the inner diameter of the molten metal tank 6. Here, by the inner diameter of the molten metal supply discharge port 6a being formed to be smaller than the inner diameter of the inner space of the molten metal tank 6, the inner space of the molten metal tank 6 can also have a space around the space above the molten metal supply discharge port 6a. Therefore, the inner space of the molten metal tank 6 can have a space capable of detecting the liquid level of the molten metal around the space above the molten metal supply discharge port 6a. Therefore, the liquid level detecting device 7 can detect the liquid level of the molten metal existing in the space around the space above the molten metal supply discharge port 6a. Further, the inner space of the molten metal tank 6 can have a space capable of disposing the liquid level detecting device 7 around the space above the molten metal supply discharge port 6a. Therefore, the liquid level detecting device 7 can be disposed in the space around the space above the molten metal supply discharge port 6a. Further, the inner space of the molten metal tank 6 can have a space capable of opening the gas supply port 62a and the gas exhaust port 62b in the space around the space above the molten metal supply discharge port 6a and at a position higher than the liquid surface of the molten metal. Therefore, the gas supply port 62a and the gas exhaust port 62b can be opened in the space around the space above the molten metal supply discharge port 6a and at a position higher than the liquid surface of the molten metal. Here, the space above the molten metal supply discharge port 6a means a space or region extending vertically upward from the molten metal supply discharge port 6a formed in the lower end surface of the molten metal tank 6 to the upper end surface of the molten metal tank 6 in the inner space of the molten metal tank 6. Further, the space around the space above the molten metal supply discharge port 6a means a space or region other than the space above the molten metal supply discharge port 6a in the inner space of the molten metal tank 6.

[0110] Further detailed description Figure 1 The molten metal tank 6 is disposed above the molten bath 20 in the longitudinal direction. The molten metal tank 6 includes a cylindrical main body member 61 disposed with the axial direction of the center axis as the vertical direction, and a lid member 62 covering the opening of the upper end surface of the main body member 61. The inner diameter of the lower portion of the main body member 61 is formed to be smaller than the inner diameter of the upper portion of the main body member 61 and is equal to or larger than the inner diameter of the molten metal supply discharge port 6a. For example, in the main body member 61, the upper portion is formed with a certain inner diameter, and the lower portion is formed with the inner diameter becoming smaller from the upper portion to the lower portion. Figure 1 In the main body member 61, the upper portion is formed with a certain inner diameter, and the lower portion is formed with the inner diameter becoming smaller from the upper portion to the lower portion. Further, for example, in the main body member 61, the lower portion is formed with the inner diameter becoming smaller from the upper portion to the lower portion.Figure 1 Among the main body member 61, the largest inner diameter is formed larger than the inner diameter of the cylinder hole of the melting pot 20. The opening of the molten metal supply discharge port 6a is communicated in the main body member 61 and opens at the lower end surface of the main body member 61. The molten metal tank 6 can accumulate the molten metal in an amount exceeding the capacity that can be accumulated in the melting pot 20 in the internal space formed by the inner wall of the main body member 61 and the cover member 62.

[0111] The molten metal supply discharge port 6a opens in the upper side portion of the cylinder hole of the melting pot 20 except directly above the opening 40a of the melting pot 20 side of the communication path 40. In addition, the molten metal supply discharge port 6a opens in the portion of the melting pot 20 in which the molten metal is accumulated. Figure 1The molten metal supply discharge port 6a is shown as being positioned directly above the opening 40a of the communicating passage 40 on the molten metal tank 6 side of the molten bath tank 20 in the horizontal direction. The inner diameter of the molten metal supply discharge port 6a is formed to be larger than the inner diameter of the communicating passage 40 and smaller than the inner diameter of the interior space of the molten metal tank 6. In addition, the inner diameter of the molten metal supply discharge port 6a is formed to be smaller than the inner diameter of the cylinder hole of the molten bath tank 20. Here, by the inner diameter of the molten metal supply discharge port 6a being formed to be smaller than the inner diameter of the interior space of the molten metal tank 6, the interior space of the molten metal tank 6 can also have a space between the inner wall of the molten metal tank 6 and the space positioned directly above the molten metal supply discharge port 6a. Therefore, the interior space of the molten metal tank 6 can have a space between the inner wall of the molten metal tank 6 and the space positioned directly above the molten metal supply discharge port 6a in which the liquid level of the molten metal can be detected by the liquid level detecting device 7. Therefore, the liquid level detecting device 7 can detect the liquid level of the molten metal present in the space between the inner wall of the molten metal tank 6 and the space positioned directly above the molten metal supply discharge port 6a. In addition, the interior space of the molten metal tank 6 can have a space in which the liquid level detecting device 7 can be disposed between the inner wall of the molten metal tank 6 and the space positioned directly above the molten metal supply discharge port 6a. Therefore, the liquid level detecting device 7 can be disposed in the space between the inner wall of the molten metal tank 6 and the space positioned directly above the molten metal supply discharge port 6a. In addition, the interior space of the molten metal tank 6 can have a space in which the gas supply port 62a and the gas exhaust port 62b can be opened at a position higher than the liquid level of the molten metal between the inner wall of the molten metal tank 6 and the space positioned directly above the molten metal supply discharge port 6a. Therefore, the gas supply port 62a and the gas exhaust port 62b can be opened at a position higher than the liquid level of the molten metal in the space between the inner wall of the molten metal tank 6 and the space positioned directly above the molten metal supply discharge port 6a. Here, the space positioned directly above the molten metal supply discharge port 6a is a space or region in the interior space of the molten metal tank 6 that extends directly upward from the molten metal supply discharge port 6a formed in the lower end surface of the main member 61 to the cover member 62 in a cylindrical shape having the same inner diameter as the inner diameter of the molten metal supply discharge port 6a. In addition, the space around the space positioned directly above the molten metal supply discharge port 6a is a space or region in the interior space of the molten metal tank 6 other than the space positioned directly above the molten metal supply discharge port 6a. In addition, the inner wall of the molten metal tank 6 is, for example, the inner wall of the main member 61 shown. Figure 2 the inner wall of the main member 61.

[0112] In the case where the molten metal supply discharge port 6a is formed in the lower end surface of the main member 61, the inner wall of the main member 61 can be formed to be inclined downward toward the center of the molten metal supply discharge port 6a. Figure 2When the molten metal is injected from the injection device 1, even if the molten metal in the injection cylinder 30 flows backward into the melting cylinder 20, the molten metal flowing straight in the communication path 40 into the melting cylinder 20 changes the direction of flow in the melting cylinder 20 having a larger inner diameter than the communication path 40 to the axial direction of the melting cylinder 20 and further disperses in the melting cylinder 20 before flowing into the molten metal tank 6, thereby reducing the flow rate. Thus, it is possible to prevent the liquid level of the molten metal accumulated in the molten metal tank from greatly fluctuating due to the backward flow of the molten metal.

[0113] Further, ​ In the molten metal tank 6, the inner diameter of the molten metal supply discharge port 6a is formed to be larger than the inner diameter of the communication path 40 and smaller than the inner diameter of the inner space of the molten metal tank 6. Further, the inner diameter of the inner space of the molten metal tank 6 is formed to have the inner diameter of the space around the space located directly above the molten metal supply discharge port 6a. Further, the inner diameter of the inner space of the molten metal tank 6 can be formed to have the inner diameter of the space around the space located directly above the molten metal supply discharge port 6a, which enables detection of the liquid level of the molten metal. Further, the inner diameter of the inner space of the molten metal tank 6 can be formed to have the inner diameter of the space around the space located directly above the molten metal supply discharge port 6a, which enables arrangement of the liquid level detection device 7. Further, the inner diameter of the inner space of the molten metal tank 6 can be formed to have the inner diameter of the space around the space located directly above the molten metal supply discharge port 6a, which enables arrangement of the gas supply port 62a and the gas discharge port 62b at a position higher than the liquid level of the molten metal. When the molten metal is injected, even if the molten metal in the injection cylinder 30 flows backward into the melting cylinder 20 in the communication path 40, the molten metal flowing into the molten metal tank 6 through the molten metal supply discharge port 6a having a larger inner diameter than the communication path 40 after the direction of flow is changed in the melting cylinder 20 has a slower flow rate than when flowing through the communication path 40. Further, the temporary flow of the molten metal in the melting cylinder 20 generated during the dispersion of the backwardly flowing molten metal colliding with the molten metal in the melting cylinder 20 also affects the molten metal in the molten metal tank 6, thereby temporarily fluctuating the liquid level of the molten metal in the molten metal tank 6. In addition to the inner diameter of the molten metal supply discharge port 6a being formed to be larger than the inner diameter of the communication path 40, it is also formed to be smaller than the inner diameter of the inner space of the molten metal tank 6, thereby making it possible to suppress the above situation. Thus, it is possible to further prevent the liquid level of the molten metal accumulated in the molten metal tank from greatly fluctuating due to the backward flow of the molten metal.

[0114] Further, at a position in the molten metal tank 6 opposite the opening surface of the molten metal supply discharge port 6a, a molten metal dispersion member 63 dispersing the molten metal flowing into the molten metal tank 6 in the molten metal tank 6 can also be included. The molten metal dispersion member 63 disperses the molten metal flowing straight in the molten metal supply discharge port 6a into the molten metal tank 6 in the molten metal tank 6, thereby reducing the flow rate. Thus, it is possible to prevent the liquid level of the molten metal accumulated in the molten metal tank from greatly fluctuating due to the backward flow of the molten metal.

[0115] ​ The molten metal tank 6 is shown to have an inner diameter of the molten metal supply discharge port 6a that is larger than the inner diameter of the communication path 40 and smaller than the inner diameter of the inner space of the molten metal tank 6, and further includes the molten metal dispersing member 63 in the inner space. ​ The molten metal dispersing member 63 is shown to have a cylindrical shape, and is installed in the molten metal tank 6 in a manner that connects the base end to the cover member 62, and has an opening of the front end that is distanced from the opening of the molten metal supply discharge port 6a by a prescribed distance and faces the opening. The inner diameter of the cylindrical molten metal dispersing member 63 is formed to be larger than the inner diameter of the opening of the molten metal supply discharge port 6a. In addition, the outer diameter of the cylindrical molten metal dispersing member 63 is formed to be smaller than the inner diameter of the inner space of the molten metal tank 6. Thus, the molten metal dispersing member 63 can accommodate the upper portion of the space directly above the molten metal supply discharge port 6a. In addition, there can be a space between the outer peripheral surface of the molten metal dispersing member 63 and the inner wall of the molten metal tank 6 that is around the space directly above the molten metal supply discharge port 6a. Therefore, the inner space of the molten metal tank 6 can have a space between the outer peripheral surface of the molten metal dispersing member 63 and the inner wall of the molten metal tank 6 that is capable of detecting the liquid level of the molten metal by the liquid level detecting device 7. Thus, the liquid level detecting device 7 can detect the liquid level of the molten metal present in the space between the outer peripheral surface of the molten metal dispersing member 63 and the inner wall of the molten metal tank 6. In addition, the inner space of the molten metal tank 6 can have a space between the outer peripheral surface of the molten metal dispersing member 63 and the inner wall of the molten metal tank 6 that is capable of disposing the liquid level detecting device 7. Thus, the liquid level detecting device 7 can be disposed in the space between the outer peripheral surface of the molten metal dispersing member 63 and the inner wall of the molten metal tank 6. In addition, the inner space of the molten metal tank 6 can have a space between the outer peripheral surface of the molten metal dispersing member 63 and the inner wall of the molten metal tank 6 that is capable of having the gas supply port 62a and the gas exhaust port 62b at a position that is higher than the liquid surface of the molten metal. Thus, the gas supply port 62a and the gas exhaust port 62b can be opened at a position that is between the outer peripheral surface of the molten metal dispersing member 63 and the inner wall of the molten metal tank 6 and is higher than the liquid surface of the molten metal. Further, the molten metal dispersing member 63 has at least one through-hole 63a that penetrates the inside and the outside in the side surface portion other than the base end side portion. At this time, the liquid level detecting device 7, the gas supply port 62a, and the gas exhaust port 62b are disposed in a manner that is outside of the molten metal dispersing member 63 and does not face the through-hole 63a of the molten metal dispersing member 63. Furthermore, the side surface portion of the molten metal dispersing member 63 can be, in other words, the side wall of the molten metal dispersing member 63.

[0116] When the molten metal is injected, even if the molten metal in the injection cylinder 30 has a reverse flow, the molten metal flowing straight in the molten metal supply discharge port 6a into the molten metal tank 6 is dispersed in the direction of flowing in the molten metal dispersion member 63 by initially flowing into the molten metal dispersion member 63 and then flowing out through the through hole 63a after the flow rate is reduced, and the flow rate is further reduced. Thus, the liquid level of the molten metal accumulated in the molten metal tank can be prevented from greatly fluctuating due to the reverse flow of the molten metal.

[0117] In addition, as in other embodiments not shown, the molten metal dispersion member can be a flat plate shape or a disc shape, and installed in the molten metal tank 6 in a manner that the single surface faces the opening of the molten metal supply discharge port 6a at a predetermined distance. The area of the plate surface of the flat plate shape or disc shape of the molten metal dispersion member is larger than the area of the opening of the molten metal supply discharge port 6a. At this time, the molten metal dispersion member of the flat plate shape or disc shape is disposed between the opening of the molten metal supply discharge port 6a and the liquid level detecting device 7, between the opening of the molten metal supply discharge port 6a and the gas supply port 62a, and between the opening of the molten metal supply discharge port 6a and the gas discharge port 62b.

[0118] When the molten metal is injected, even if the molten metal in the injection cylinder 30 has a reverse flow, the molten metal flowing straight in the molten metal supply discharge port 6a into the molten metal tank 6 is dispersed in a radial direction along the plate surface of the flat plate shape or disc shape of the molten metal dispersion member, and the flow rate is reduced by further flowing into the molten metal tank 6 from the outer edge of the plate surface and the inner wall of the molten metal tank 6. Thus, the liquid level of the molten metal accumulated in the molten metal tank can be prevented from greatly fluctuating due to the reverse flow of the molten metal.

[0119] The embodiments are chosen to illustrate the principles of the invention and its utility. Various modifications can be made to the described embodiments. The scope of the invention is defined by the appended claims.

Claims

1. An injection device of a light metal injection molding machine, comprising: a melting unit that heats and melts a light metal material in a cylindrical short bar shape supplied in order from an opening of a rear end face of a melting cylinder into the melting cylinder along a cylinder hole, into a melt in the melting cylinder, and accumulates the melt in the melting cylinder; an injection unit that accumulates the melt supplied into an injection cylinder from the melting cylinder by free fall due to gravity in the injection cylinder, and injects the melt accumulated in the injection cylinder using a plunger that is able to be inserted in the injection cylinder so as to be movable forward and backward; a connecting member that connects the melting unit and the injection unit, and is formed with a communication path that communicates the melting cylinder and the injection cylinder; a melt tank that is formed with a melt supply / discharge port that supplies and discharges the melt, is provided with the melt supply / discharge port at a position other than a position at which an opening face of the melting cylinder side of the communication path faces, opens the melt supply / discharge port in the melting cylinder, is connected to the melting cylinder in a manner that communicates with the melting cylinder, accumulates the melt in an amount that exceeds a capacity that is able to be accumulated in the melting cylinder, is disposed away from the communication path in a horizontal direction, an inner diameter of the melt supply / discharge port is formed to be larger than an inner diameter of the communication path and smaller than an inner diameter of the melt tank; a backflow prevention device that opens and closes the communication path; and a melt dispersing member that is installed at a position in the melt tank that faces an opening face of the melt supply / discharge port, disperses the melt flowing into the melt tank in the melt tank. The melt tank includes a main body member in a cylindrical shape that is disposed so that an axial direction of a center axis becomes a vertical direction, and a cover member that covers an opening of an upper end face of the main body member. The melt supply / discharge port is formed in a lower end face of the main body member. The melt dispersing member is in a cylindrical shape, and is installed in the melt tank so that a base end is connected to the cover member, and an opening of a front end faces the opening of the melt supply / discharge port at a prescribed distance away from the opening. An inner diameter of the melt dispersing member is formed to be larger than an inner diameter of the melt supply / discharge port. An outer diameter of the melt dispersing member is formed to be smaller than an inner diameter of the melt tank. At least one through hole that penetrates an inside and an outside is formed in a side portion of the melt dispersing member other than a base end side portion.

2. The injection device of a light metal injection molding machine according to claim 1, comprising a liquid level detection device. The liquid level detection device detects a liquid level height of the melt accumulated in the melt tank.

3. The injection device of a light metal injection molding machine according to claim 2, wherein The melting cylinder is disposed laterally and above the injection cylinder. The opening of the melting cylinder side of the communication path is opened at a lower side portion of a cylinder hole of the melting cylinder. The melt tank is disposed above the melting cylinder away from the opening of the melting cylinder side of the communication path in a horizontal direction. ​ ​ ​ ​ ​ ​ The molten metal supply discharge port is formed in a lower end surface of the molten metal tank, is located directly above the opening of the molten cylinder side of the communication path in the horizontal direction, and is opened in an upper side portion of the cylinder hole of the molten cylinder, The liquid level detection device is disposed directly above the molten metal supply discharge port in the horizontal direction.

4. The injection device of a light metal injection molding machine according to claim 3, wherein The interior space of the molten metal tank has a space capable of detecting the liquid level of the molten metal around the space located directly above the molten metal supply discharge port.

5. The injection device of a light metal injection molding machine according to claim 3, wherein The injection cylinder is disposed laterally and below the molten cylinder, The plunger is moved to a prescribed position before the molten metal is supplied, and is advanced when the molten metal is injected, In the connecting member, the molten unit side is connected to the front side portion and the lower side portion of the molten cylinder, and the injection unit side is connected to the front side portion and the upper side portion of the injection cylinder, The opening of the molten cylinder side of the communication path is opened in the front side portion of the cylinder hole of the molten cylinder, and the opening of the injection cylinder side is opened in the front side portion and the upper side portion of the cylinder hole of the injection cylinder, The backflow prevention device opens and closes the communication path at a midway portion thereof or the opening of the injection cylinder side of the communication path.

6. The injection device of a light metal injection molding machine according to claim 5, wherein The backflow prevention device includes: A valve seat is formed around the opening of the injection cylinder side of the communication path, and a valve rod is advanced and retracted in a manner that seats in the valve seat to close the communication path and is retracted from the valve seat to open the communication path.

7. The injection device of a light metal injection molding machine according to claim 3, comprising an inert gas supply device that supplies inert gas, The molten metal tank is formed with a gas supply port and a gas exhaust port at a position above the molten metal accumulated therein and at a position directly above the molten metal supply discharge port in the horizontal direction, and the space above the molten metal accumulated therein is an inert gas environment, The gas supply port is connected to the inert gas supply device and guides inert gas to the space above the molten metal in the molten metal tank, The gas exhaust port exhausts inert gas in the molten metal tank to the outside.

8. The injection device of a light metal injection molding machine according to claim 7, wherein The interior space of the molten metal tank has a space capable of being around the space located directly above the molten metal supply discharge port and is a space in which the gas supply port and the gas exhaust port are opened at a position higher than the liquid level of the molten metal accumulated in the molten metal tank.

9. The injection device of a light metal injection molding machine according to claim 3, wherein The molten metal tank comprises: A cylindrical main body member is disposed with the axial direction of the center axis as the up-down direction; A cover member covers the opening of the upper end surface of the main body member, The molten metal supply discharge port is formed in the lower end surface of the main body member.

10. The injection device of a light metal injection molding machine according to claim 3, wherein The inner diameter of the lower portion of the main member is formed to be smaller than the inner diameter of the upper portion of the main member and is equal to or greater than the inner diameter of the molten metal supply discharge port.

11. The injection apparatus of a light metal injection molding machine according to claim 1, wherein The internal space of the molten metal tank has a space capable of detecting the liquid level of the molten metal between the outer peripheral surface of the molten metal dispersing member and the inner wall of the molten metal tank.

12. The injection apparatus of a light metal injection molding machine according to claim 2, wherein The internal space of the molten metal tank has a space capable of disposing the liquid level detecting device between the outer peripheral surface of the molten metal dispersing member and the inner wall of the molten metal tank.

13. The injection apparatus of a light metal injection molding machine according to claim 2, wherein The liquid level detecting device is disposed outside the molten metal dispersing member without facing the through hole of the molten metal dispersing member.

14. The injection apparatus of a light metal injection molding machine according to claim 1, comprising an inert gas supply device that supplies inert gas, The molten metal tank is formed with a gas supply port and a gas discharge port above the accumulated molten metal, outside the molten metal dispersing member, and without facing the through hole of the molten metal dispersing member, so that the environment above the accumulated molten metal is the inert gas, The gas supply port is connected to the inert gas supply device to direct inert gas toward the above of the molten metal in the molten metal tank, The gas discharge port discharges inert gas in the molten metal tank to the outside.

15. The injection apparatus of a light metal injection molding machine according to claim 1, wherein The inner diameter of the lower portion of the main member is formed to be smaller than the inner diameter of the upper portion of the main member and is equal to or greater than the inner diameter of the molten metal supply discharge port.

16. The injection apparatus of a light metal injection molding machine according to claim 1, wherein The melting unit, the injection unit, the connecting member, and the molten metal tank each has at least one heater.

17. The injection apparatus of a light metal injection molding machine according to claim 1, wherein A control device is connected to at least the melting unit and controls at least the melting unit.

18. The injection apparatus of a light metal injection molding machine according to claim 2, wherein A control device is connected to at least the melting unit and the liquid level detecting device and controls at least the melting unit based on the output signal of the liquid level detecting device.

19. The injection apparatus of a light metal injection molding machine according to claim 2, wherein The inner diameter of the molten metal supply discharge port is formed to be smaller than the inner diameter of the cylinder hole of the melting cylinder.

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