Injection device, molding machine and control method of a molding machine

Abstract

An injection device of an embodiment includes an injection cylinder including a rod connectable to a plunger, a piston fixed to the rod, a cylinder tube slidably housing the piston, a rod-side chamber in which the rod is disposed, and a head-side chamber disposed on an opposite side of the rod-side chamber from the piston, a hydraulic pump, a flow control valve that controls a flow rate of an operating fluid discharged from the rod-side chamber, an accumulator that increases a flow rate of the operating fluid supplied to the head-side chamber, and a control unit that controls the hydraulic pump, the flow control valve, and the accumulator to start supplying the operating fluid to the head-side chamber using the hydraulic pump in a state in which the flow control valve is closed when injecting a liquid material using the plunger, and to supply the operating fluid to the head-side chamber using the accumulator after the operating fluid in the head-side chamber reaches a predetermined pressure.

Description

TECHNICAL FIELD

[0001] The present application relates to an injection device that fills a cavity in a metal mold with a liquid material, a molding machine, and a control method of a molding machine. BACKGROUND

[0002] A die casting machine manufactures a molded product (a die casting product) by filling a cavity in a metal mold, which is clamped by a clamping device, with a melt using an injection device. The injection device includes, for example, an injection cylinder as an actuator. The injection cylinder includes, for example, a rod that can be coupled to a plunger that slides in a sleeve, an injection piston that is fixed to the rod, and a cylinder barrel that slidably houses the piston inside. The cylinder barrel has a rod-side chamber in which the rod is disposed and a head-side chamber that is located on the opposite side of the rod-side chamber with the injection piston interposed therebetween.

[0003] The injection piston moves toward the rod by supplying an operating oil to the head-side chamber. With the movement of the injection piston, the plunger advances in the sleeve toward the metal mold, and the melt is filled into the cavity in the metal mold.

[0004] The speed of the injection piston is controlled, for example, by controlling the flow rate of the operating oil discharged from the rod-side chamber with a flow control valve. This control method is called outlet throttle control.

[0005] In the case where the injection of the melt is performed by the outlet throttle control, when the operating oil is supplied to the head-side chamber, the operating oil of the rod-side chamber is compressed, and the injection piston can sharply fly out. If the injection piston sharply flies out, air can be entrapped in the melt. If air is entrapped in the melt, the quality of the molded product can deteriorate.

[0006] In Patent Literature 1, an injection device is described that has an auxiliary oil pressure supply portion that supplies the operating oil when the pressure of the operating oil of the rod-side chamber is below a reference value in order to suppress the sharp fly-out of the injection piston.

[0007] PRIOR ART DOCUMENTS

[0008] PATENT LITERATURE

[0009] Patent Literature 1: Japanese Patent Application Publication No. 2019-72751 SUMMARY

[0010] PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] The present application is to provide an injection device, a molding machine, and a control method of a molding machine that can suppress the sharp fly-out of a piston.

[0012] MEANS FOR SOLVING THE PROBLEMS

[0013] The injection device of the technical solution of the present application has: an injection cylinder including a rod connectable with a plunger sliding in a sleeve, a piston fixed on the rod, a cylinder barrel slidably accommodating the piston, a rod-side chamber in which the rod is arranged, and a head-side chamber located on the opposite side of the rod-side chamber and sandwiching the piston; a hydraulic pump; a flow control valve controlling the flow of the operating fluid discharged from the rod-side chamber; an accumulator for increasing the flow of the operating fluid supplied to the head-side chamber; and a control unit controlling the hydraulic pump, the flow control valve, and the accumulator when injecting a liquid material using the plunger, so as to start supplying the operating fluid to the head-side chamber using the hydraulic pump in a state that the flow control valve is closed, and supply the operating fluid to the head-side chamber using the accumulator after the operating fluid in the head-side chamber reaches a specified pressure.

[0014] In the injection device of the above technical solution, preferably, the specified pressure is the pressure at which the pressure of the operating fluid in the rod-side chamber and the pressure of the operating fluid in the head-side chamber are balanced.

[0015] In the injection device of the above technical solution, preferably, the control unit opens the flow control valve to discharge the operating fluid from the rod-side chamber after the specified pressure is reached.

[0016] In the injection device of the above technical solution, preferably, the hydraulic pump has variable discharge amount or discharge pressure of the operating fluid, and the control unit controls the discharge amount or discharge pressure of the operating fluid of the hydraulic pump to increase the pressure of the head-side chamber.

[0017] In the injection device of the above technical solution, preferably, it further has: a first flow path supplying the operating fluid to the accumulator using the hydraulic pump; a second flow path supplying the operating fluid to the head-side chamber using the accumulator; a third flow path discharging the operating fluid from the rod-side chamber and having the flow control valve; and a fourth flow path supplying the operating fluid to the head-side chamber using the hydraulic pump and being different from the first flow path; and the control unit supplies the operating fluid to the head-side chamber using the accumulator and the second flow path after starting to supply the operating fluid to the head-side chamber using the hydraulic pump and the fourth flow path.

[0018] In the injection device of the above technical solution, preferably, between the hydraulic pump and the fourth flow path, a first branch flow path that supplies the operating fluid at a first pressure and a second branch flow path that supplies the operating fluid at a second pressure higher than the first pressure are further provided; the control unit controls to supply the operating fluid to the head-side chamber using the second branch flow path after the operating fluid is started to be supplied to the head-side chamber using the first branch flow path and before the operating fluid is supplied to the head-side chamber using the accumulator.

[0019] In the injection device of the above technical solution, preferably, the control unit controls to supply the operating fluid to the head-side chamber using the first flow path when the operating fluid is supplied to the head-side chamber using the accumulator and the second flow path.

[0020] The molding machine of one technical solution of the present application includes the injection device of the above technical solution, a mold clamping device that clamps a metal mold, and an ejection device that ejects a molded product from the metal mold; the injection device injects a liquid material into the metal mold.

[0021] The control method of the molding machine of one technical solution of the present application includes a mold clamping device that clamps a metal mold, an ejection device that ejects a molded product from the metal mold, and an injection device that injects a liquid material into the metal mold using a plunger; the injection device includes an injection cylinder including a rod that is connected to the plunger that slides in a sleeve, a piston that is fixed to the rod, a cylinder tube that slidably accommodates the piston, a rod-side chamber in which the rod is disposed, and a head-side chamber that is located on the opposite side of the rod-side chamber with the piston interposed therebetween, a hydraulic pump, a flow control valve that controls the flow rate of an operating fluid discharged from the rod-side chamber, and an accumulator that increases the flow rate of the operating fluid supplied to the head-side chamber; in the control method of the molding machine, when the injection of the liquid material is performed, the operating fluid is started to be supplied to the head-side chamber using the hydraulic pump in a state where the flow control valve is closed; and after the operating fluid in the head-side chamber reaches a predetermined pressure, the operating fluid is supplied to the head-side chamber using the accumulator.

[0022] In the control method of the molding machine of the above technical solution, preferably, the predetermined pressure is a pressure at which the pressure of the operating fluid in the rod-side chamber and the pressure of the operating fluid in the head-side chamber are balanced.

[0023] In the control method of the molding machine of the above technical solution, preferably, after the predetermined pressure is reached, the flow control valve is opened to discharge the operating fluid from the rod-side chamber.

[0024] In the control method of the molding machine according to the above aspect, preferably, the discharge amount or the discharge pressure of the hydraulic fluid of the hydraulic pump is controlled to increase the pressure of the head-side chamber.

[0025] Effects of Invention

[0026] According to the present application, it is possible to provide an injection device, a molding machine, and a control method of a molding machine that can suppress the abrupt ejection of a piston. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a schematic view showing the overall structure of the molding machine according to the first embodiment.

[0028] Figure 2 is a schematic view showing the structure of the injection device according to the first embodiment.

[0029] Figure 3 is a schematic view showing the control method of the molding machine according to the first embodiment.

[0030] Figure 4 is a schematic view showing the control method of the molding machine according to the first embodiment.

[0031] Figure 5 is a schematic view showing the control method of the molding machine according to the first embodiment.

[0032] Figure 6 is a schematic view showing the control method of the molding machine according to the first embodiment.

[0033] Figure 7 is a schematic view showing the operation of the injection device according to the comparative example of the first embodiment.

[0034] Figure 8 is a schematic view showing the operation of the injection device according to the first embodiment.

[0035] Figure 9 is a schematic view showing the structure of the injection device according to the second embodiment.

[0036] Figure 10 is a schematic view showing the control method of the molding machine according to the second embodiment.

[0037] Figure 11 is a schematic view showing the control method of the molding machine according to the second embodiment.

[0038] Figure 12 is a schematic view showing the control method of the molding machine according to the second embodiment.

[0039] Figure 13 is a schematic view showing the control method of the molding machine according to the second embodiment.

[0040] Figure 14is a diagram for explaining a control method of the molding machine of the second embodiment.

[0041] Figure 15 is a diagram for explaining an operation of the injection device of the second embodiment. DETAILED DESCRIPTION

[0042] Hereinafter, an embodiment of the present application will be described with reference to the drawings.

[0043] In addition, in the present specification, an oil pressure is described as an example of hydraulic pressure. For example, an oil pressure pump is described as an example of a hydraulic pump. In addition to the oil pressure, for example, a water pressure can be used. Furthermore, in the present specification, an operating oil is described as an example of an operating fluid.

[0044] (First Embodiment)

[0045] The injection device of the first embodiment includes an injection cylinder including a rod connectable to a plunger that slides in a sleeve, a piston fixed to the rod, a cylinder tube in which the piston is slidably accommodated, a rod-side chamber in which the rod is disposed, and a head-side chamber located on the opposite side of the rod-side chamber with the piston interposed therebetween, a hydraulic pump, a flow control valve that controls a flow rate of an operating fluid discharged from the rod-side chamber, an accumulator that increases a flow rate of the operating fluid supplied to the head-side chamber, and a control section that controls the hydraulic pump, the flow control valve, and the accumulator so as to start supplying the operating fluid to the head-side chamber using the hydraulic pump in a state where the flow control valve is closed when injection of a liquid material using the plunger is performed, and supplies the operating fluid to the head-side chamber using the accumulator after the operating fluid in the head-side chamber reaches a predetermined pressure.

[0046] The molding machine of the first embodiment includes the injection device described above, a mold clamping device that clamps a metal mold, and an ejection device that ejects a molded product from the metal mold, and the injection device injects a liquid material into the metal mold.

[0047] Figure 1 is a diagram showing the entire structure of the molding machine of the first embodiment. Figure 1 is a side view including a cross-sectional view in a part. The molding machine of the first embodiment is a die casting machine 100. The die casting machine 100 is, for example, a cold chamber type die casting machine.

[0048] The die casting machine 100 includes a mold clamping device 10, an ejection device 12, an injection device 14, a metal mold 18, and a control unit 20.

[0049] The die casting machine 100 includes a base 22, a fixed platen 24, a movable platen 26, a link housing 28, a tie rod 30, a sleeve 31, and a plunger 33. The plunger 33 has a top pin 33a and a plunger rod 33b.

[0050] The die casting machine 100 is a cold chamber type die casting machine that performs injection molding by injecting a liquid material into the inside of the metal mold 18 (Figure 1

[0051] The metal mold 18 includes a fixed metal mold 18a and a movable metal mold 18b. The metal mold 18 is provided between the mold clamping device 10 and the injection device 14.

[0052] The fixed platen 24 is fixed to the base 22. The fixed platen 24 is capable of holding the fixed metal mold 18a.

[0053] The movable platen 26 is movably provided to the base 22 in a mold opening and closing direction. The mold opening and closing direction is a direction in which the mold is opened and closed, and is a direction in which the movable metal mold 18b is opposed to the fixed metal mold 18a and held by the movable platen 26. Figure 1

[0054] The link housing 28 is provided to the base 22. One end of a link mechanism constituting the mold clamping device 10 is fixed to the link housing 28.

[0055] The fixed platen 24 and the link housing 28 are fixed by a tie bar 30. The tie bar 30 supports a mold clamping force during application of the mold clamping force to the fixed metal mold 18a and the movable metal mold 18b.

[0056] The mold clamping device 10 has a function of opening and closing the metal mold 18 and clamping the metal mold 18.

[0057] The injection device 14 has a function of injecting a melt into the cavity Ca of the metal mold 18 and pressurizing the melt. The injection device 14 has a rod 80 which is connected to a plunger 33 that slides in a sleeve 31.

[0058] The ejection device 12 has a function of ejecting a die casting product manufactured from the metal mold 18.

[0059] The sleeve 31 penetrates the cavity Ca of the metal mold 18. The sleeve 31 is, for example, a cylindrical member which is connected to the fixed metal mold 18a. The sleeve 31 is, for example, a circular cylindrical shape.

[0060] The plunger 33 slides in the sleeve 31. The plunger 33 includes a tip core 33a and a plunger rod 33b. The tip core 33a which is fixed to a front end of the plunger rod 33b slides in the sleeve 31 in a front and rear direction. The melt in the sleeve 31 is pushed out into the metal mold 18 by the tip core 33a sliding forward in the sleeve 31.

[0061] ​​The control unit 20 includes a control device 32, an input device 34, and a display device 36. The control unit 20 has a function of controlling molding operation of the die casting machine 100 using the clamping device 10, the ejecting device 12, and the injection device 14.

[0062] The input device 34 receives an input operation by an operator. The operator can set a molding condition of the die casting machine 100 or the like using the input device 34. The input device 34 is, for example, a touch panel using a liquid crystal display or an organic EL display.

[0063] The display device 36 displays, for example, a molding condition, an operation state, or the like of the die casting machine 100 on a screen. The display device 36 is, for example, a liquid crystal display or an organic EL display.

[0064] The control device 32 has a function of performing various kinds of arithmetic operations and outputting a control command to each part of the die casting machine 100. The control device 32 has, for example, a function of storing a molding condition or the like. The control device 32 controls, for example, operation of the injection device 14.

[0065] The control device 32 is constituted, for example, by a combination of hardware and software. The control device 32 includes, for example, a CPU (Central Processing Unit), a semiconductor memory, and a control program stored in the semiconductor memory.

[0066] Figure 2 is a schematic view showing a structure of the injection device of the first embodiment.

[0067] The injection device 14 has an injection cylinder 44, an oil pressure pump 46 (hydraulic pump), an oil tank 48, an accumulator 50, a position sensor 52, an injection valve 54, a speed control valve 56 (flow control valve), a direction switching valve 58, a first on-off valve 60, a second on-off valve 62, a filling supplement valve 64, a first flow path 70a, a second flow path 70b, a third flow path 70c, a fourth flow path 70d, a fifth flow path 70e, a sixth flow path 70f, and a controller 72 (control section). The oil pressure pump 46 is an example of a hydraulic pump. The speed control valve 56 is an example of a flow control valve. The controller 72 is an example of a control section.

[0068] The injection cylinder 44 includes a rod 80, an injection piston 82 (piston), a cylinder tube 84, a rod side chamber 86, and a head side chamber 88. The injection piston 82 is an example of a piston.

[0069] The rod 80 can be coupled to the plunger 33 that slides in the sleeve 31. The plunger 33 moves in the sleeve 31 by movement of the rod 80.

[0070] The injection piston 82 is fixed to the rod 80. The injection piston 82 is slidably housed in the cylinder tube 84. The injection piston 82 is, for example, cylindrical.

[0071] The cylinder 84 slidably houses the injection piston 82. The cylinder 84 is, for example, a cylindrical shape.

[0072] A rod side chamber 86 is provided on the rod 80 side inside the cylinder 84. The rod 80 is disposed in the rod side chamber 86.

[0073] A head side chamber 88 is provided on the side opposite the rod 80 side inside the cylinder 84. The head side chamber 88 is located on the side opposite the rod side chamber 86 with the injection piston 82 interposed therebetween.

[0074] The oil pressure pump 46 is driven by a pump motor not shown, for example. The oil pressure pump 46 has a function of sucking and discharging the operating oil from the oil tank 48. The oil pressure pump 46 contributes to supplying the operating oil to the accumulator 50 and the injection cylinder 44, for example.

[0075] The discharge amount or discharge pressure of the operating oil discharged by the oil pressure pump 46 is variable. The oil pressure pump 46 is, for example, a variable displacement type pump. The variable displacement type pump is capable of varying the discharge amount and discharge pressure of the operating oil.

[0076] The oil tank 48 stores the operating oil supplied to the accumulator 50 or the injection cylinder 44, for example. In addition, the oil tank 48 recovers the operating oil used by the accumulator 50 or the injection cylinder 44, for example.

[0077] The accumulator 50 has a function of making the flow rate of the operating oil supplied to the head side chamber 88 large. The accumulator 50 uses a high-pressure enclosed gas to accumulate energy, and makes the flow rate of the operating oil large by instantaneously releasing the energy. By providing the accumulator 50, it is possible to make the injection cylinder 44 act at high speed.

[0078] The first flow path 70a connects the oil pressure pump 46 and the accumulator 50. Using the first flow path 70a, it is possible to supply the operating oil from the oil pressure pump 46 to the accumulator 50, and to charge the operating oil into the accumulator 50 to accumulate pressure.

[0079] In addition, the first flow path 70a is connected to the head side chamber 88 via the second flow path 70b. At the time of the injection operation of the injection cylinder 44, it is possible to supplement the operating oil to the second flow path 70b using the first flow path 70a.

[0080] The sixth flow path 70f connects the oil pressure pump 46 and the head side chamber 88 via the fourth flow path 70d. Using the sixth flow path 70f and the fourth flow path 70d, it is possible to supply the operating oil from the oil pressure pump 46 to the head side chamber 88. The fourth flow path 70d is different from the first flow path 70a.

[0081] In addition, the sixth flow path 70f connects the oil pressure pump 46 and the rod side chamber 86 via the fifth flow path 70e. Using the sixth flow path 70f and the fifth flow path 70e, it is possible to supply the operating oil from the oil pressure pump 46 to the rod side chamber 86.

[0082] The 3rd flow path 70c connects the rod-side chamber 86 with the oil tank 48. With the 3rd flow path 70c, the operation oil discharged from the rod-side chamber 86 can be recovered into the oil tank 48.

[0083] The 1st flow path 70a to the 6th flow path 70f are constituted, for example, by steel pipes or hoses.

[0084] The injection valve 54 is provided in the 2nd flow path 70b. The injection valve 54 is provided between the head-side chamber 88 and the accumulator 50. The injection valve 54 permits or interrupts the supply of operation oil from the accumulator 50 to the head-side chamber 88.

[0085] The injection valve 54 is constituted, for example, by a forward-acting check valve that permits the flow of operation oil from the accumulator 50 to the head-side chamber 88 when no pilot pressure is introduced, and interrupts the flow thereof in the opposite direction. When the pilot pressure is introduced to the injection valve 54, the flow of both is interrupted. The injection valve 54 has a function of preventing the backflow of operation oil from the head-side chamber 88 to the accumulator 50.

[0086] When the injection valve 54 is in the open state, the flow of operation oil from the accumulator 50 to the head-side chamber 88 is permitted. When the injection valve 54 is in the closed state, the flow of operation oil from the accumulator 50 to the head-side chamber 88 is interrupted.

[0087] The speed control valve 56 is provided in the 3rd flow path 70c. The speed control valve 56 is provided between the rod-side chamber 86 and the oil tank 48. The speed control valve 56 controls the flow rate of operation oil discharged from the rod-side chamber 86 to the oil tank 48.

[0088] The advancing speed of the injection piston 82 is controlled by the control of the flow rate of operation oil by the speed control valve 56. The so-called outlet throttle control is performed by the speed control valve 56. In the case where the speed control valve 56 is in the closed state, the flow of operation oil between the rod-side chamber 86 and the oil tank 48 is interrupted.

[0089] The kind of the speed control valve 56 is not particularly limited as long as it can control the flow rate of operation oil. The speed control valve 56 can be, for example, either a valve that performs pressure compensation or a valve that does not perform pressure compensation. Further, the speed control valve 56 can be, for example, either a servo valve that is subjected to feedback control or a proportional valve that is subjected to open control.

[0090] The direction switching valve 58 is provided between the 6th flow path 70f and the 4th flow path 70d, and between the 6th flow path 70f and the 5th flow path 70e. The direction switching valve 58 is provided between the head-side chamber 88 and the oil pressure pump 46, and between the rod-side chamber 86 and the oil pressure pump 46.

[0091] The direction switching valve 58 has a function of switching a flow path of the operation oil supplied from the oil pressure pump 46 via the 6th flow path 70f between the 4th flow path 70d and the 5th flow path 70e. The direction switching valve 58 has a function of switching a supply target of the operation oil supplied from the oil pressure pump 46 between the head side chamber 88 and the rod side chamber 86.

[0092] For example, by supplying the operation oil to the head side chamber 88, the injection piston 82 advances. Also, for example, by supplying the operation oil to the rod side chamber 86, the injection piston 82 retreats.

[0093] The kind of the direction switching valve 58 is not particularly limited as long as it can switch the flow direction of the operation oil supplied from the oil pressure pump 46. The direction switching valve 58 is, for example, an electromagnetic switching valve that moves a spool core using an electromagnet.

[0094] The 1st on-off valve 60 is provided in the 4th flow path 70d. The 1st on-off valve 60 is provided between the head side chamber 88 and the direction switching valve 58. The 1st on-off valve 60 allows or blocks the flow of the operation oil between the direction switching valve 58 and the head side chamber 88.

[0095] When the 1st on-off valve 60 is in an open state, the flow of the operation oil between the direction switching valve 58 and the head side chamber 88 is allowed. When the 1st on-off valve 60 is in a closed state, the flow of the operation oil between the direction switching valve 58 and the head side chamber 88 is allowed or blocked.

[0096] The kind of the 1st on-off valve 60 is not particularly limited as long as it can allow and block the flow of the operation oil.

[0097] The 2nd on-off valve 62 is provided in the 5th flow path 70e. The 2nd on-off valve 62 is provided between the rod side chamber 86 and the direction switching valve 58. The 2nd on-off valve 62 allows or blocks the flow of the operation oil between the direction switching valve 58 and the rod side chamber 86.

[0098] When the 2nd on-off valve 62 is in an open state, the flow of the operation oil between the direction switching valve 58 and the rod side chamber 86 is allowed. When the 2nd on-off valve 62 is in a closed state, the flow of the operation oil between the direction switching valve 58 and the rod side chamber 86 is blocked.

[0099] The kind of the 2nd on-off valve 62 is not particularly limited as long as it can allow and block the flow of the operation oil.

[0100] The filling replenishment valve 64 is provided in the 1st flow path 70a. The filling replenishment valve 64 is provided between the oil pressure pump 46 and the accumulator 50. The filling replenishment valve 64 is provided between the head side chamber 88 and the oil pressure pump 46.

[0101] The filling replenishment valve 64 allows or blocks the flow of the hydraulic oil between the accumulator 50 and the oil hydraulic pump 46, for example. The filling replenishment valve 64 allows or blocks the flow of the hydraulic oil between the head-side chamber 88 and the oil hydraulic pump 46, for example.

[0102] The type of the filling replenishment valve 64 is not particularly limited as long as it can allow and block the flow of the hydraulic oil.

[0103] The position sensor 52 has a function of detecting the position of the rod 80. The position sensor 52 is an optical or magnetic linear encoder, for example. By differentiating the position of the rod 80 detected by the position sensor 52, the speed of the rod 80 can be detected.

[0104] The controller 72 controls the operation of the injection cylinder 44, the oil hydraulic pump 46, the oil tank 48, the accumulator 50, the injection valve 54, the speed control valve 56, the direction switching valve 58, the first on-off valve 60, the second on-off valve 62, and the filling replenishment valve 64, for example.

[0105] The controller 72 has a function of, when the injection of the molten metal using the plunger 33 is performed, starting the supply of the hydraulic oil to the head-side chamber 88 using the oil hydraulic pump 46 in a state where the speed control valve 56 is closed, and after the hydraulic oil of the head-side chamber 88 reaches a predetermined pressure, controlling the speed control valve 56, the oil hydraulic pump 46, and the accumulator 50 to supply the hydraulic oil to the head-side chamber 88 using the accumulator 50, for example.

[0106] The above-described predetermined pressure is a pressure at which the pressure of the hydraulic oil of the rod-side chamber 86 and the pressure of the hydraulic oil of the head-side chamber 88 are balanced, for example. The controller 72 has a function of, after the hydraulic oil of the head-side chamber 88 reaches the above-described predetermined pressure, controlling to open the speed control valve 56 and discharge the hydraulic oil from the rod-side chamber 86, for example.

[0107] The controller 72 has a function of controlling the discharge amount or the discharge pressure of the hydraulic oil of the oil hydraulic pump 46 to increase the pressure of the hydraulic oil of the head-side chamber 88, for example. The controller 72 preferably controls the discharge amount or the discharge pressure of the hydraulic oil of the oil hydraulic pump 46 to gently increase the pressure of the hydraulic oil of the head-side chamber 88, for example.

[0108] The controller 72 has a function of, after starting the supply of the hydraulic oil to the head-side chamber 88 using the oil hydraulic pump 46 and the fourth flow path 70d, controlling to supply the hydraulic oil to the head-side chamber 88 using the accumulator 50 and the second flow path 70b, for example.

[0109] Further, the controller 72 has, for example, a function of controlling to supply the actuating oil to the head-side chamber 88 using the first flow path 70a when the actuating oil is supplied to the head-side chamber 88 using the accumulator 50 and the second flow path 70b.

[0110] The controller 72 is composed of, for example, a combination of hardware and software. The controller 72 includes, for example, a CPU, a semiconductor memory, and a control program stored in the semiconductor memory.

[0111] The controller 72 is, for example, a part of the control device 32.

[0112] Next, an example of a control method of the die casting machine 100 will be described. In particular, a control method of the injection device 14 of the die casting machine 100 will be described. A part of the description will be omitted with respect to the control other than the control method of the injection device 14 of the die casting machine 100, for example, the control of the mold clamping device 10 and the ejector device 12.

[0113] Figure 3 、 Figure 4 、 Figure 5 and Figure 6 are explanatory diagrams of the control method of the molding machine of the first embodiment. Figure 3 、 Figure 4 、 Figure 5 and Figure 6 are explanatory diagrams of the control method of the injection device 14 of the die casting machine 100.

[0114] When the die casting product is manufactured with the die casting machine 100, the metal mold 18 is clamped using the mold clamping device 10. With respect to the cavity Ca inside the metal mold 18 that is clamped, the molten metal is injected using the injection device 14.

[0115] First, as shown in Figure 3 , the actuating oil is filled in the accumulator 50. The actuating oil is filled in the accumulator 50 from the oil pressure pump 46 through the first flow path 70a. At this time, the filling make-up valve 64 is set to the open state. Further, the injection valve 54, the speed control valve 56 (flow control valve), the direction switching valve 58, the first on-off valve 60, and the second on-off valve 62 are set to the closed state. The white arrow indicates the flow of the actuating oil.

[0116] After the filling of the actuating oil to the accumulator 50 is performed, the injection of the molten metal using the plunger 33 is performed.

[0117] The molten metal is supplied from an unillustrated molten metal supply device to the sleeve 31.

[0118] Next, as shown in Figure 4As shown, the supply of the action melt to the head-side chamber 88 is started using the oil pressure pump 46. The controller 72 controls the direction switching valve 58 so that the supply target of the action oil supplied from the oil pressure pump 46 becomes the head-side chamber 88. That is, the direction switching valve 58 is controlled so that the action oil flows from the 6th flow path 70f to the 4th flow path 70d.

[0119] When the supply of the action melt to the head-side chamber 88 is started using the oil pressure pump 46, the 1st on-off valve 60 is set to the open state. The injection valve 54, the speed control valve 56, the 2nd on-off valve 62, and the filling supplement valve 64 are set to the closed state.

[0120] When the supply of the action melt to the head-side chamber 88 is started using the oil pressure pump 46, the discharge amount or the discharge pressure of the oil pressure pump 46 is controlled, for example, so that the flow rate of the action oil supplied to the head-side chamber 88 continuously or stepwise becomes large. When the action melt is supplied to the head-side chamber 88 using the oil pressure pump 46, the discharge amount or the discharge pressure of the oil pressure pump 46 is controlled, for example, so that the pressure of the action oil of the head-side chamber 88 continuously or stepwise becomes large.

[0121] If the action melt is supplied to the head-side chamber 88, the action oil of the rod-side chamber 86 is compressed, and the rod 80 advances.

[0122] Next, as shown in FIG. 6, the supply of the action melt to the head-side chamber 88 is started using the oil pressure pump 46. At this time, the 1st on-off valve 60 is set to the open state. Figure 5

[0123] The prescribed pressure is, for example, a pressure at which the pressure of the action oil of the head-side chamber 88 and the pressure of the action oil of the rod-side chamber 86 become in a balanced state. That is, it is a pressure at which a so-called outlet throttling state is achieved. The prescribed pressure can also be set to, for example, a pressure lower than the pressure at which the pressure of the action oil of the head-side chamber 88 and the pressure of the action oil of the rod-side chamber 86 become in a balanced state. In addition, the prescribed pressure can also be set to the same pressure as the supply pressure when the action oil is supplied to the head-side chamber 88 using the accumulator 50 later.

[0124] The determination of whether or not the prescribed pressure is reached can be performed by directly measuring the pressure of the action oil of the head-side chamber 88, for example. In addition, the determination of whether or not the prescribed pressure is reached can also be performed in terms of the elapsed time from the start of the supply of the action oil to the head-side chamber 88, for example. In addition, the determination of whether or not the prescribed pressure is reached can also be based on the amount of movement of the rod 80 measured by the position sensor 52, for example.

[0125] Next, as shown in FIG. 6, the supply of the action melt to the head-side chamber 88 is started using the oil pressure pump 46. At this time, the 1st on-off valve 60 is set to the open state. Figure 6 Next, as shown in FIG. 6, the supply of the action melt to the head-side chamber 88 is started using the oil pressure pump 46. At this time, the 1st on-off valve 60 is set to the open state.​

[0126] At this time, the injection valve 54 is set to the open state. Further, the speed control valve 56 is set to the open state. The first on-off valve 60 and the second on-off valve 62 are set to the closed state.

[0127] By setting the speed control valve 56 to the open state, the operation oil is discharged from the rod-side chamber 86.

[0128] By supplying the operation oil to the head-side chamber 88, the operation oil is discharged from the rod-side chamber 86, and the rod 80 advances. By controlling the flow rate of the operation oil discharged from the rod-side chamber 86 by the speed control valve 56, the advancing speed of the rod 80 is controlled to the desired speed.

[0129] The filling replenishment valve 64 is set to the open state, for example. By setting the filling replenishment valve 64 to the open state, the operation oil supplied to the head-side chamber 88 can be replenished.

[0130] The replenishment of the operation oil supplied to the head-side chamber 88 is stopped, for example, before the supply of the operation oil to the head-side chamber 88 is ended using the accumulator 50. The filling replenishment valve 64 stops the replenishment of the operation oil, for example, by being set to the closed state after the advancing speed of the rod 80 reaches a prescribed speed.

[0131] By the rod 80 advancing, the plunger 33 coupled to the rod 80 advances in the sleeve 31. Also, the molten metal supplied into the sleeve 31 is filled into the cavity Ca in the metal mold 18.

[0132] Next, the effects and advantages of the injection device 14 of the first embodiment, the die casting machine 100, and the control method of the die casting machine 100 will be described.

[0133] In a die casting machine, by supplying operation oil to the head-side chamber of an injection cylinder, an injection piston moves to the rod side. With the movement of the injection piston, a plunger advances in a sleeve toward a metal mold, and fills molten metal into a cavity in the metal mold.

[0134] The speed of the injection piston is controlled, for example, by using a flow control valve to control the flow rate of the operation oil discharged from the rod-side chamber. This control method is called outlet throttle control.

[0135] In the case of injection of molten metal by outlet throttle control, when operation oil is initially supplied to the head-side chamber, the operation oil of the rod-side chamber is compressed, and the injection piston can sharply fly out. If the injection piston sharply flies out, air can be entrapped in the molten metal pushed out by the plunger. If air is entrapped in the molten metal, the quality of the molded product can deteriorate.

[0136] Figure 7is a explanatory view of the operation of the injection device of the comparative example of the first embodiment. The injection device of the comparative example differs from the injection device of the first embodiment in that the supply of the action oil to the head-side chamber using the oil pressure pump is not performed before the supply of the action oil to the head-side chamber using the accumulator is performed by the control section.

[0137] In the control method of the injection device of the comparative example, when the molten metal is filled into the cavity Ca of the metal mold 18 using the injection device 14, the supply of the action oil to the head-side chamber using the oil pressure pump is omitted Figure 4 and the supply of the action oil to the head-side chamber using the accumulator is performed Figure 6 as shown by the step.

[0138] Figure 7 The horizontal axis of the graph is time. Figure 7 The vertical axis of the graph is the pressure of the action oil of the rod-side chamber and the head-side chamber and the advancing speed of the rod.

[0139] In the control method of the injection device of the comparative example, a large amount of the action oil is supplied to the head-side chamber in a short time using the accumulator. Therefore, the pressure of the action oil of the head-side chamber sharply rises. The action oil of the rod-side chamber is sharply compressed, and the pressure of the action oil of the rod-side chamber also sharply rises.

[0140] The injection piston sharply flies out by the action oil of the rod-side chamber being sharply compressed. That is, the rod sharply advances at a large speed. Thus, the plunger fixed to the front portion of the rod sharply advances and pushes the molten metal. Thereby, air is entrapped into the molten metal, and the quality of the die casting product can be deteriorated.

[0141] Figure 8 is a explanatory view of the operation of the injection device of the first embodiment. Figure 8 The horizontal axis of the graph is time. Figure 8 The vertical axis of the graph is the pressure of the action oil of the rod-side chamber and the head-side chamber and the advancing speed of the rod.

[0142] In the injection device 14 of the first embodiment, before a large amount of the action oil is supplied to the head-side chamber 88 using the accumulator 50, the oil pressure pump 46 is controlled so that, for example, the flow rate of the action oil supplied to the head-side chamber 88 continuously becomes large. Further, for example, the pressure of the action oil of the head-side chamber 88 continuously becomes large.

[0143] Therefore, as shown in Figure 8 the pressure of the action oil of the head-side chamber 88 gradually rises. Further, the pressure of the action oil of the rod-side chamber 86 also gradually rises.

[0144] Thus, the sharp flying out of the injection piston 82 is suppressed, and, as shown in Figure 8 the advancing speed of the rod 80 is suppressed. Thereby, the advancing speed of the plunger 33 pushing the molten metal is also suppressed, the entrapping of air into the molten metal is reduced, and the quality of the die casting product is improved.

[0145] The injection device of the first embodiment can suppress the abrupt shooting-out of the injection piston 82 with a simple structure in which only a new function is added to the controller 72, while adopting the outlet throttle control. The injection device of the first embodiment controls the oil pressure pump to perform the inlet throttle control, while adopting the configuration for the outlet throttle control.

[0146] From the viewpoint of suppressing the air from being entrapped into the melt, the advancing speed of the rod 80 is preferably 0.1 m / sec or less.

[0147] The time point at which the supply of the operating oil to the head-side chamber 88 using the fourth flow path 70d is stopped after the operating oil of the head-side chamber 88 reaches the prescribed pressure is preferably the same as the time point at which the supply of the operating oil to the head-side chamber 88 using the accumulator 50 is started. By setting the two time points to be the same, the time of the injection operation performed by the injection device 14 can be shortened, and the injection operation can be stabilized. For example, by setting the first on-off valve to the closed state at the same time as setting the injection valve 54 to the open state, the above-described two time points can be set to be the same.

[0148] The above-described two time points can also be made to be different.

[0149] Before the supply of the large amount of operating oil to the head-side chamber 88 using the accumulator 50, the flow rate of the operating oil supplied to the head-side chamber 88 can be made to be larger in stages by controlling the oil pressure pump 46, for example. Further, the pressure of the operating oil of the head-side chamber 88 can be made to be larger in stages, for example.

[0150] According to the first embodiment, an injection device, a molding machine, and a control method of a molding machine that can suppress the abrupt shooting-out of the piston and improve the quality of the molded product can be provided.

[0151] (Second Embodiment)

[0152] The injection device of the second embodiment is different from the injection device of the first embodiment in that: between the hydraulic pump and the fourth flow path, a first branch flow path that can supply the operating fluid at a first pressure and a second branch flow path that can supply the operating fluid at a second pressure higher than the first pressure are further provided; and the control section controls to perform the supply of the operating fluid to the head-side chamber using the second branch flow path after the supply of the operating fluid to the head-side chamber using the first branch flow path is started and before the supply of the operating fluid to the head-side chamber using the accumulator is started. Hereinafter, regarding the contents repeated from the first embodiment, there are cases where a part of the description is omitted.

[0153] The molding machine of the second embodiment differs from the molding machine of the first embodiment in the injection device.

[0154] The molding machine of the second embodiment is a die casting machine 200. The die casting machine 200 is, for example, a cold chamber type die casting machine.

[0155] The die casting machine 200 includes a mold clamping device 10, an ejection device 12, an injection device 15, a metal mold 18, and a control unit 20.

[0156] Figure 9 is a schematic view showing the structure of the injection device of the second embodiment.

[0157] The injection device 15 includes an injection cylinder 44, an oil hydraulic pump 46 (hydraulic pump), an oil tank 48, an accumulator 50, a position sensor 52, an injection valve 54, a speed control valve 56 (flow control valve), a direction switching valve 58, a first on-off valve 60, a second on-off valve 62, a filling supplement valve 64, a first pressure relief valve 66, a second pressure relief valve 68, a first flow path 70a, a second flow path 70b, a third flow path 70c, a fourth flow path 70d, a fifth flow path 70e, a sixth flow path 70f, a first branch flow path 71a, a second branch flow path 71b, and a controller 72 (control section). The oil hydraulic pump 46 is an example of a hydraulic pump. The speed control valve 56 is an example of a flow control valve. The controller 72 is an example of a control section.

[0158] The injection cylinder 44 includes a rod 80, an injection piston 82 (piston), a cylinder tube 84, a rod side chamber 86, and a head side chamber 88. The injection piston 82 is an example of a piston.

[0159] The oil hydraulic pump 46 is, for example, a constant displacement type pump. The constant displacement type pump is, for example, a pump whose discharge amount of operation oil is constant regardless of the use pressure.

[0160] The first branch flow path 71a is provided between the oil hydraulic pump 46 and the fourth flow path 70d. The first branch flow path 71a is, for example, provided between the direction switching valve 58 and the sixth flow path 70f. The first branch flow path 71a is capable of supplying operation oil at the first pressure P1.

[0161] The second branch flow path 71b is provided between the oil hydraulic pump 46 and the fourth flow path 70d. The second branch flow path 71b is, for example, provided between the direction switching valve 58 and the sixth flow path 70f. The second branch flow path 71b is capable of supplying operation oil at the second pressure P2 which is higher than the first pressure. The second branch flow path 71b is provided in parallel with the first branch flow path 71a.

[0162] The first pressure relief valve 66 is provided in the first branch flow path 71a. The first pressure relief valve 66 sets the pressure of the operation oil flowing through the first branch flow path 71a to the first pressure P1.

[0163] The first pressure relief valve 66 also has a function of permitting or blocking the flow of the operating oil of the first branch flow path 71a. When the first pressure relief valve 66 is in an open state, the flow of the operating oil of the first branch flow path 71a is permitted. When the first pressure relief valve 66 is in a closed state, the flow of the operating oil of the first branch flow path 71a is blocked.

[0164] The second pressure relief valve 68 is provided in the second branch flow path 71b. The pressure of the operating oil flowing through the second branch flow path 71b is set to the second pressure P2 higher than the first pressure P1 by the second pressure relief valve 68.

[0165] The second pressure relief valve 68 also has a function of permitting or blocking the flow of the operating oil of the second branch flow path 71b. When the second pressure relief valve 68 is in an open state, the flow of the operating oil of the second branch flow path 71b is permitted. When the second pressure relief valve 68 is in a closed state, the flow of the operating oil of the second branch flow path 71b is blocked.

[0166] The controller 72 controls, for example, the operation of the injection cylinder 44, the oil pressure pump 46, the oil tank 48, the accumulator 50, the injection valve 54, the speed control valve 56, the direction switching valve 58, the first on-off valve 60, the second on-off valve 62, the first pressure relief valve 66, the second pressure relief valve 68, and the filling supplement valve 64.

[0167] The controller 72 has, for example, a function of controlling to supply the operating oil to the head-side chamber 88 using the second branch flow path 71b after starting the supply of the operating oil to the head-side chamber 88 using the first branch flow path 71a and before starting the supply of the operating oil to the head-side chamber 88 using the accumulator 50.

[0168] Next, an example of the control method of the die casting machine 200 will be described. In particular, the control method of the injection device 15 of the die casting machine 200 will be described. The control of the injection device 15 of the die casting machine 200 other than the control method will be described with omission of a part of the description, for example, regarding the control of the mold clamping device 10 and the ejecting device 12.

[0169] Figure 10 、 Figure 11 、 Figure 12 、 Figure 13 and Figure 14 is a diagram for explaining the control method of the molding machine of the second embodiment. Figure 10 、 Figure 11 、 Figure 12 、 Figure 13 and Figure 14 is a diagram for explaining the control method of the injection device 15 of the die casting machine 200.

[0170] When manufacturing die-cast products using the die-casting machine 200, the metal mold 18 is closed using the mold-closing device 10. Molten liquid is then injected into the cavity Ca within the closed metal mold 18 using the injection device 15.

[0171] First, such as Figure 10 As shown, operating oil is filled into the accumulator 50. Operating oil is supplied from the hydraulic pump 46 through the first flow path 70a to the accumulator 50. At this time, the filling valve 64 is set to the open state. Furthermore, the injection valve 54, speed control valve 56, direction switching valve 58, first on / off valve 60, second on / off valve 62, filling valve 64, first pressure relief valve 66, and second pressure relief valve 68 are set to the closed state. The white arrows indicate the flow of operating oil.

[0172] After filling the accumulator 50 with operating oil, the molten liquid is injected using the plunger 33.

[0173] Molten liquid is supplied into sleeve 31 by a molten liquid supply device not shown in the figure.

[0174] Next, as Figure 11 As shown, hydraulic pump 46 begins supplying actuating fluid to head chamber 88. Controller 72 controls directional switching valve 58 to direct the actuating fluid supplied from hydraulic pump 46 to head chamber 88. That is, directional switching valve 58 is controlled to direct the actuating fluid from sixth flow path 70f to fourth flow path 70d.

[0175] Furthermore, controller 72 controls the supply of actuating oil to the head chamber 88 at a first pressure P1 using the first branch flow path 71a. Controller 72 also controls the opening of the first pressure relief valve 66 and the closing of the second pressure relief valve 68, supplying actuating oil to the head chamber 88 using the first branch flow path 71a.

[0176] When the hydraulic pump 46 begins to supply the working melt to the head chamber 88, the first on / off valve 60 is set to the open state. The injection valve 54, the speed control valve 56, the second on / off valve 62, and the filling and replenishing valve 64 are set to the closed state.

[0177] If the first branch flow path 71a is used to supply the actuating melt to the head side chamber 88, the actuating oil in the rod side chamber 86 is compressed, and the rod 80 advances.

[0178] Next, as Figure 12 As shown, controller 72 controls the supply of actuating oil to head chamber 88 at a second pressure P2, which is higher than the first pressure P1, using second branch flow path 71b. Controller 72 also controls the opening of second pressure relief valve 68 and the closing of first pressure relief valve 66, using second branch flow path 71b to supply actuating oil to head chamber 88.

[0179] If the actuating oil is supplied to the head-side chamber 88 using the second branch passage 71b, the actuating oil of the rod-side chamber 86 is compressed, and the rod 80 is further advanced.

[0180] Next, as shown in FIG. 6, the actuating oil is supplied to the head-side chamber 88 using the oil pressure pump 46. After the actuating oil of the head-side chamber 88 reaches a predetermined pressure, the supply of the actuating oil to the head-side chamber 88 is stopped. At this time, the first on-off valve 60 and the second pressure relief valve 68 are set to the closed state. Figure 13

[0181] Next, as shown in FIG. 7, the supply of the actuating oil to the head-side chamber 88 is performed using the accumulator 50. In addition, the actuating oil is discharged from the rod-side chamber 86. Figure 14 At this time, the injection valve 54 is set to the open state. In addition, the speed control valve 56 is set to the open state. The first on-off valve 60, the second on-off valve 62, the first pressure relief valve 66, and the second pressure relief valve 68 are set to the closed state.

[0182] By setting the speed control valve 56 to the open state, the actuating oil is discharged from the rod-side chamber 86.

[0183] By supplying the actuating oil to the head-side chamber 88, the actuating oil is discharged from the rod-side chamber 86, and the rod 80 is advanced. By controlling the flow rate of the actuating oil discharged from the rod-side chamber 86 by the speed control valve 56, the advancing speed of the rod 80 is controlled to a desired speed.

[0184] The filling replenishment valve 64 is set to the open state, for example. By setting the filling replenishment valve 64 to the open state, the actuating oil supplied to the head-side chamber 88 can be replenished. The filling replenishment valve 64 is set to the closed state, for example, after the advancing speed of the rod 80 reaches a predetermined speed.

[0185] By the advancement of the rod 80, the plunger 33 is advanced in the sleeve 31. Also, the melt supplied into the sleeve 31 is filled into the cavity Ca in the mold 18.

[0186] Next, the effects of the injection device 15, the die casting machine 200, and the control method of the die casting machine 200 of the second embodiment will be described.

[0187]

[0188] is a diagram for explaining the effects of the injection device of the second embodiment. Figure 15 The horizontal axis of is time. Figure 15 The vertical axis of is the pressure of the actuating oil of the rod-side chamber and the head-side chamber and the advancing speed of the rod. Figure 15

[0189] ​​In the injection device 15 of the second embodiment, before the accumulator 50 supplies a large amount of operation oil to the head-side chamber 88, the first branch flow path 71a and the second branch flow path 71b are used in stages so that the flow rate of the operation oil supplied to the head-side chamber 88 increases in stages. Further, the first branch flow path 71a and the second branch flow path 71b are used in stages, for example, so that the pressure of the operation oil of the head-side chamber 88 increases in stages.

[0190] Therefore, as shown in FIG. 6, the pressure of the operation oil of the head-side chamber 88 increases in stages. Further, the pressure of the operation oil of the rod-side chamber 86 also increases in stages. Figure 15

[0191] Therefore, the flying out of the injection piston 82 is divided into two times. Thus, as shown in FIG. 7, the advancing speed of the rod 80 is suppressed. Thereby, the advancing speed of the plunger 33 that pushes the molten metal is also suppressed, the entrainment of air into the molten metal is suppressed, and the quality of the die casting is improved. Figure 15

[0192] In addition, it is also possible to further suppress the advancing speed of the plunger 33 that pushes the molten metal by providing three or more branch flow paths that can supply operation oil having different pressures.

[0193] According to the second embodiment, it is possible to provide an injection device, a molding machine, and a control method of a molding machine that can suppress the sharp flying out of a piston and improve the quality of a molded product.

[0194] In the first and second embodiments, a die casting machine that fills a molten metal into a metal mold is exemplified as a molding machine, but for example, the present application can be applied to an injection molding machine that fills a resin material into a metal mold.

[0195] The embodiments of the present application have been described above with reference to specific examples. However, the present application is not limited to these specific examples. In the embodiments, in the injection device, the molding machine, and the control method of the molding machine, and the like, the parts that are not directly required in the description of the present application are omitted from the description, but the elements related to the injection device, the molding machine, and the control method of the molding machine, and the like that are required can be appropriately selected and used.

[0196] In addition to this, all of the injection device, the molding machine, and the control method of the molding machine that have the elements of the present application and can be appropriately designed and changed by those skilled in the art are included in the scope of the present application. The scope of the present application is defined by the technical solution and the equivalent scope thereof.

[0197] Explanation of Reference Numerals

[0198] 10 mold clamping device

[0199] 12 ejector device

[0200] ​​14 injection device

[0201] 15 injection device

[0202] 18 mold

[0203] 31 sleeve

[0204] 33 plunger

[0205] 44 syringe

[0206] 46 oil hydraulic pump

[0207] 50 accumulator

[0208] 56 speed control valve

[0209] 70a first flow path

[0210] 70b second flow path

[0211] 70c third flow path

[0212] 70d fourth flow path

[0213] 71a first branch flow path

[0214] 71b second branch flow path

[0215] 72 controller

[0216] 80 rod

[0217] 82 injection piston

[0218] 84 cylinder

[0219] 86 rod side chamber

[0220] 88 head side chamber

[0221] 100 die casting machine

[0222] 200 die casting machine

[0223] Ca cavity

Claims

1. An injection device, characterized in that, have: The injection cylinder includes a rod that can be connected to a plunger that slides in a sleeve, a piston fixed to the rod, a cylinder that slidably houses the piston, a rod-side chamber on which the rod is disposed, and a head-side chamber on the opposite side of the rod-side chamber that sandwiches the piston. Hydraulic pump; A flow control valve controls the flow rate of the operating fluid discharged from the aforementioned rod-side chamber; An accumulator is used to increase the flow rate of the actuating fluid supplied to the head chamber; and The control unit controls the hydraulic pump, the flow control valve, and the accumulator when injecting liquid material using the plunger. The hydraulic pump is used to start supplying the actuating fluid to the head chamber when the flow control valve is closed. After the actuating fluid in the head chamber reaches a predetermined pressure, the accumulator is used to supply the actuating fluid to the head chamber. The pressure specified above is the pressure at which the pressure of the actuating fluid in the rod-side chamber and the pressure of the actuating fluid in the head-side chamber are in equilibrium. After reaching the specified pressure, the control unit opens the flow control valve to discharge the actuating fluid from the rod-side chamber.

2. The injection device as claimed in claim 1, characterized in that, The discharge volume or discharge pressure of the hydraulic pump's operating fluid is variable, and the control unit controls the discharge volume or discharge pressure of the hydraulic pump's operating fluid to increase the pressure in the head chamber.

3. The injection device as described in claim 1 or 2, characterized in that, It also has: In the first flow path, the aforementioned hydraulic pump is used to supply the aforementioned operating fluid to the aforementioned accumulator; The second flow path uses the aforementioned accumulator to supply the aforementioned actuating fluid to the aforementioned head-side chamber; The third flow path discharges the aforementioned actuating fluid from the aforementioned rod-side chamber and includes the aforementioned flow control valve; and The fourth flow path uses the aforementioned hydraulic pump to supply the aforementioned actuating fluid to the aforementioned head side chamber, which is different from the aforementioned first flow path. After the control unit starts supplying the actuating fluid to the head chamber using the hydraulic pump and the fourth flow path, it supplies the actuating fluid to the head chamber using the accumulator and the second flow path.

4. The injection device as described in claim 3, characterized in that, Between the hydraulic pump and the fourth flow path, there is a first branch flow path that can supply the operating fluid at a first pressure and a second branch flow path that can supply the operating fluid at a second pressure higher than the first pressure. The control unit controls the supply of the operating fluid to the head chamber using the second branch flow path after the first branch flow path is used to start supplying the operating fluid to the head chamber and before the accumulator is used to supply the operating fluid to the head chamber.

5. The injection device as described in claim 3, characterized in that, The aforementioned control unit controls the supply of the operating fluid to the head-side chamber using the aforementioned accumulator and the aforementioned second flow path, while also using the aforementioned first flow path to supply the operating fluid to the head-side chamber.

6. A molding machine, characterized in that, have: The injection device according to any one of claims 1 to 5; The mold closing device closes the metal mold; and An ejection device ejects the molded article from the aforementioned metal mold; The aforementioned injection device injects liquid material into the aforementioned metal mold.

7. A control method for a molding machine, the molding machine comprising: The mold closing device closes the metal mold; An ejection device ejects the molded article from the aforementioned metal mold; as well as An injection device that uses a plunger to inject liquid material into the aforementioned metal mold; The injection device includes: The injection cylinder includes a rod that can be connected to the plunger that slides in a sleeve, a piston fixed to the rod, a cylinder that slidably houses the piston, a rod-side chamber on which the rod is disposed, and a head-side chamber on the opposite side of the rod-side chamber that sandwiches the piston. Hydraulic pump; A flow control valve controls the flow rate of the operating fluid discharged from the aforementioned rod-side chamber; and An accumulator is used to increase the flow rate of the actuating fluid supplied to the head chamber. Its features are, When injecting the above-mentioned liquid material, with the flow control valve closed, the hydraulic pump is used to start supplying the action fluid to the head chamber. After the operating fluid in the head chamber reaches the specified pressure, the accumulator is used to supply the operating fluid to the head chamber. The pressure specified above is the pressure at which the pressure of the actuating fluid in the rod-side chamber and the pressure of the actuating fluid in the head-side chamber are in equilibrium. After reaching the specified pressure, the flow control valve is opened to allow the actuating fluid to be discharged from the rod-side chamber.

8. The control method for the molding machine as described in claim 7, characterized in that, The discharge volume or discharge pressure of the hydraulic pump is controlled to increase the pressure in the head chamber.

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