Die casting machine

Abstract

To provide a die casting machine capable of reducing cost without requiring an electric servo motor to be large-sized and high-output.SOLUTION: A die casting machine 10 is composed of an injection mechanism 30, a hydraulic operation mechanism 32, and an electric pressurizing mechanism 34. The electric pressurizing mechanism 34 is composed of an electric servo motor 60, a ball screw 62 driven by the electric servo motor 60, and a pressurizing piston 64 pushed out by the ball screw 62. The pressurizing piston 64 is pushed out into an injection cylinder 42 by the ball screw 62 to increase the pressure of working oil O, and the working oil O from a hydraulic pump 46 is supplied into the injection cylinder 42 so as to push out the pressurizing piston 64 at the time of increasing the pressure.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a die casting machine that injects molten metal into a die to form a molded product. [Background technology]

[0002] In conventional die casting machines, the molten metal melted in a melting furnace is measured and pumped up with a ladle for each shot, and the pumped molten metal is supplied to the inlet of the injection sleeve. The molten metal is then injected and filled into the cavity of the mold by the forward movement of an injection plunger that is movably mounted within the injection sleeve, thereby forming a green body.

[0003] The injection process, in which molten metal is injected into the cavity of a mold, consists of a low-speed injection process followed by a high-speed injection process. In the high-speed injection process, the molten metal must be injected to fill the mold at an injection speed that is about one order of magnitude faster than the injection speed of the injection molding machine that molds plastic products.

[0004] Furthermore, after the high-speed injection step is completed, a pressure increase step is carried out in which the pressure of the molding material in the cavity is increased by the injection plunger (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2011-224626 A Summary of the Invention [Problem to be solved by the invention]

[0006] In conventional die casting machines, in the pressure boosting process, a pressurizing piston is slid by moving a ball screw with an electric servo motor, and the pressure of the hydraulic oil in the injection cylinder in which the injection piston slides to push out the injection plunger is increased.

[0007] In addition, after the pressure of the hydraulic oil in the injection cylinder has increased to a predetermined pressure, the pressure piston is continuously pressed by the electric servo motor to maintain the pressure for a predetermined period of time.

[0008] Because a large load is placed on the electric servo motor when boosting and maintaining the hydraulic oil pressure, the electric servo motor must be made large and powerful, which increases the cost of the entire die casting machine.

[0009] The present invention has been made in consideration of these problems, and its purpose is to provide a die casting machine that does not require a large, high-output electric servo motor, thereby reducing costs. [Means for solving the problem]

[0010] According to one aspect of the present invention, A die casting machine having an injection mechanism, a hydraulic operation mechanism, and an electric pressure mechanism, The injection mechanism has an injection plunger that injects molten metal into the cavity, The hydraulic operation mechanism includes an injection cylinder that houses the injection plunger, and a hydraulic pump that supplies hydraulic oil to the injection cylinder, the electric pressure mechanism includes an electric servo motor, a ball screw driven by the electric servo motor, and a pressure piston pushed out by the ball screw, The pressurizing piston is pushed into the injection cylinder by the ball screw to increase the pressure of the hydraulic oil, The hydraulic oil from the hydraulic pump is supplied into the injection cylinder so as to push out the pressurizing piston during the pressure increase. A die casting machine is provided.

[0011] Preferably, Within the injection cylinder, a hydraulic oil filling space is formed on the opposite side of the moving direction of the pressurizing piston as viewed from the tip of the pressurizing piston, and into which the hydraulic oil for pushing out the pressurizing piston is supplied. Effect of the Invention

[0012] According to the die casting machine of the present invention, the pressure piston can be moved and the pressure maintained by applying the pressure of the hydraulic oil in addition to the power of the electric servo motor, so the burden on the electric servo motor can be reduced. This makes it unnecessary to use a large, high-power electric servo motor, and therefore makes it possible to provide a die casting machine that can reduce costs. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing an example of a die casting machine 10 according to an embodiment. [Diagram 2] 2 is a diagram showing an example of an electric pressure mechanism 34 in the die casting machine 10 according to the embodiment. FIG. [Diagram 3] 13 is a graph showing changes in the moving speed of an injection plunger 38, changes in the internal pressure of an injection cylinder 42 (inside B), and changes in the speed of an electric servo motor 60 during an injection process of a die casting machine 10 according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] (Configuration of die casting machine 10) As shown in FIG. 1, the die casting machine 10 according to this embodiment generally includes a die unit 12 and an injection unit 14.

[0015] The mold device 12 generally comprises a fixed mold 22 mounted on a fixed die plate 20 and a movable mold 26 mounted on a movable die plate 24, and a cavity 28 is formed by closing the fixed mold 22 and the movable mold 26.

[0016] The injection device 14 generally includes an injection mechanism 30, a hydraulic operation mechanism 32, and an electric pressure mechanism .

[0017] The injection mechanism 30 includes an injection sleeve 36 , an injection plunger 38 , an injection piston 40 , and an injection cylinder 42 .

[0018] The injection sleeve 36 is provided integrally with the fixed die plate 20, and is a cylindrical member having a supply port 43 formed at its upper portion through which the molten metal is supplied.

[0019] The injection plunger 38 is a generally rod-shaped member that is provided within the injection sleeve 36 so as to be capable of advancing and retreating.

[0020] The injection piston 40 is formed on the rear end side of the injection plunger 38 (the end opposite to the end in contact with the molten metal).

[0021] The injection cylinder 42 is a cylindrical member through which the injection piston 40 advances and retreats, and is filled inside with hydraulic oil O. When viewed from the injection piston 40, the space inside the injection piston 40 in the direction in which the injection piston 40 moves during the injection process is called the out-side A, and the opposite side is called the in-side B.

[0022] The hydraulic operation mechanism 32 is a mechanism for supplying hydraulic oil O used in the low-speed injection stroke, high-speed injection stroke, and pressure boosting stroke of the injection plunger 38 to the injection cylinder 42 to act on the injection piston 40, and generally includes oil piping 44, a hydraulic pump 46, a plurality of control valves 48, a low-speed side flow rate control valve 50, a high-speed side flow rate control valve 52, an accumulator 54, a pressure sensor 56, and control means 58.

[0023] In addition, the hydraulic operation mechanism 32 has a pressure piston flow rate adjustment valve 57 for applying the hydraulic oil O to the pressure piston 64 of the electric pressure mechanism .

[0024] The oil piping 44 sends the hydraulic oil O pressurized by the hydraulic pump 46 to the injection cylinder 42 via the accumulator 54, the low-speed side flow rate control valve 50, and the high-speed side flow rate control valve 52, and also forms a flow path for returning the hydraulic oil O coming out of the injection cylinder 42 to its original position via the control valve 48.

[0025] The hydraulic pump 46 is for pressurizing the hydraulic oil O to a pressure required for the low-speed injection stroke, the high-speed injection stroke, and the pressure boosting stroke of the injection plunger 38.

[0026] The control valve 48 includes a first control valve 48a for switching on and off a flow path that sends the hydraulic oil O discharged from the hydraulic pump 46 to the accumulator 54, and a second control valve 48b for switching on and off a flow path that returns the hydraulic oil O from the inside B of the injection cylinder 42 to the hydraulic pump 46 side when the injection plunger 38 is returned to the starting position, and that supplies the hydraulic oil O discharged from the hydraulic pump 46 to the outside A of the injection cylinder 42.

[0027] The low-speed flow rate adjustment valve 50 is a valve for adjusting the flow rate of the hydraulic oil O supplied from the accumulator 54 or the like to the inside B of the injection cylinder 42 in the low-speed injection process.

[0028] The high-speed side flow rate adjustment valve 52 is a valve for adjusting the flow rate of the hydraulic oil O supplied from the accumulator 54 or the like to the IN side B of the injection cylinder 42 in the high-speed injection process.

[0029] The accumulator 54 is a container for temporarily storing the hydraulic oil O pressurized by the hydraulic pump 46.

[0030] The pressure sensor 56 is an instrument for measuring the pressure of the hydraulic oil O in the inside B of the injection cylinder 42.

[0031] The control means 58 has a role of operating the hydraulic pump 46, the control valve 48, the low-speed side flow rate control valve 50, the high-speed side flow rate control valve 52, and the pressurizing piston flow rate control valve 57 while detecting position information of the injection piston 40 and a pressure signal from the pressure sensor 56 when performing the low-speed injection process, the high-speed injection process, the pressure boosting process, and the return process of the injection plunger 38. The control means 58 also controls the electric pressurizing mechanism 34.

[0032] The electric pressurizing mechanism 34 according to this embodiment will be described in detail with reference to Fig. 2. The electric pressurizing mechanism 34 is a mechanism for further pressurizing the hydraulic oil O sent into the inside B of the injection cylinder 42, and generally includes an electric servo motor 60, a ball screw 62, a pressurizing piston 64, and a plurality of guide bars 66 (only one is shown in Fig. 2). The ball screw 62 is composed of a screw shaft 68 and a nut 70.

[0033] The electric servo motor 60 has a role of rotating a screw shaft 68 of the ball screw 62 via a belt or the like (or a gear) and sliding a nut 70 relative to the screw shaft 68.

[0034] In this embodiment, the electric servo motor 60 is fixed to a servo motor mount 72. A threaded shaft bearing 74 that holds the rotating threaded shaft 68 is formed in the servo motor mount 72, and a first guide bar holding portion 76 that holds one end of each guide bar 66 is also formed. A drive belt 78 is stretched between the rotating shaft 77 of the electric servo motor 60 and an end of the threaded shaft 68, and the rotational force of the rotating shaft 77 of the electric servo motor 60 is transmitted to the threaded shaft 68 by this drive belt 78.

[0035] The nut 70 of the ball screw 62 is fixed to an intermediate holding member 80, which has a guide bar insertion hole 82 through which the guide bar 66 is inserted. By inserting the guide bar 66 into the guide bar insertion hole 82, the intermediate holding member 80 is guided by the guide bar 66, and the nut 70 can advance and retreat in a predetermined direction (downward in the figure) without wobbling. In addition, because the intermediate holding member 80 is guided by the guide bar 66, the pressurizing piston 64 can advance and retreat in a predetermined direction (downward in the figure) without wobbling.

[0036] The other end of the guide bar 66 is held by a tip holding member 84. This tip holding member 84 is provided at the end of the injection cylinder 42 on the pressure piston 64 side. The tip holding member 84 is also formed with a pressure piston insertion hole 86 through which the pressure piston 64 attached to the nut 70 is inserted.

[0037] The pressurizing piston 64 is composed of a tip portion 64a that slides inside the injection cylinder 42 and a rod portion 64b that has a smaller diameter than the tip portion 64a, and the opposite end of the rod portion 64b is connected to a nut 70. In this manner, the tip portion 64a of the pressurizing piston 64 is inserted and installed so as to be able to protrude and retract into the inside side B of the injection cylinder 42 in the hydraulic operation mechanism 32, and as the nut 70 of the ball screw 62 moves downward in the figure, the pressurizing piston 64 enters the inside side B and pressurizes the hydraulic oil O filled in the inside side B.

[0038] As viewed from the tip 64a of the pressurizing piston 64, the space within the injection cylinder 42 in the direction in which the pressurizing piston 64 moves during the pressure increasing process is the “IN-side B” as described above, and on the opposite side thereto is formed a hydraulic oil filling space C filled with hydraulic oil O that presses the pressurizing piston 64 toward the IN-side B.

[0039] An oil piping 44 for supplying hydraulic oil O from a hydraulic pump 46 and an accumulator 54 is connected to this hydraulic oil filling space C, and a pressurized piston flow control valve 57 is disposed between the accumulator 54 and the hydraulic oil filling space C.

[0040] The pressurized piston flow control valve 57 can be switched between a mode in which the hydraulic oil O from the accumulator 54 is supplied to the hydraulic oil filling space C, and a mode in which the hydraulic oil O filled in the hydraulic oil filling space C is returned to the hydraulic oil reservoir 59.

[0041] (Injection process of the die casting machine 10 according to this embodiment) Next, the injection step in the procedure for molding a molded body using the die-casting machine 10 according to this embodiment will be described with reference to FIG.

[0042] In the die casting machine 10 according to this embodiment, the injection process is also divided into a low-speed injection process, a high-speed injection process, and a pressure boosting process.

[0043] Before starting the injection process, the control valve 48 of the hydraulic operation mechanism 32 is operated to connect the discharge side of the hydraulic pump 46 to the accumulator 54 and connect the suction side of the hydraulic pump 46 to a hydraulic oil tank (not shown). In addition, both the low-speed side flow rate control valve 50 and the high-speed side flow rate control valve 52 are closed to a zero flow rate state.

[0044] Thereafter, the hydraulic pump 46 is operated to fill the accumulator 54 with hydraulic oil O at a predetermined pressure. At the same time, the injection sleeve 36 is filled with molten metal that has been separately prepared.

[0045] The low-speed injection process is started. The low-speed flow rate control valve 50 in the hydraulic operation mechanism 32 is opened, and hydraulic oil O from the accumulator 54 (and hydraulic pump 46) is supplied to the inside B of the injection cylinder 42, and the injection plunger 38 is moved at a predetermined speed to fill the molten metal into the cavity 28. This low-speed injection process continues for several seconds (1 to 2 seconds).

[0046] Thereafter, the high-speed injection process begins. In addition to the low-speed flow rate control valve 50 in the hydraulic operation mechanism 32, the high-speed flow rate control valve 52 is opened, hydraulic oil O is supplied to the inside B of the injection cylinder 42, and the injection plunger 38 is moved at a predetermined speed to fill the cavity 28 with molten metal. The high-speed injection process lasts for about a few hundredths of a second. When the high-speed injection process is completed, the low-speed flow rate control valve 50 and the high-speed flow rate control valve 52 are closed.

[0047] Next, the pressure increasing process is started. The electric servo motor 60 of the electric pressure mechanism 34 is operated to rotate the screw shaft 68 of the ball screw 62, and the nut 70 is moved toward the injection cylinder 42. In this way, the pressure piston 64 is pushed by the nut 70 and moved, whereby the pressure of the hydraulic oil O filled in the inside B of the injection piston 40 can be increased.

[0048] In the die casting machine 10 according to this embodiment, at the start of the pressure increasing process, the pressurizing piston flow control valve 57 enters a mode in which it supplies hydraulic oil O from the hydraulic pump 46 and the accumulator 54 to the hydraulic oil filling space C simultaneously with the operation of the electric servo motor 60.

[0049] As a result, the pressure of the hydraulic oil O supplied to the hydraulic oil filling space C can be applied to move the pressurizing piston 64, not only with the force of the electric servo motor 60, thereby reducing the burden on the electric servo motor 60 and shortening the acceleration time of the pressure boost. In addition, by making the diameter of the tip end 64a of the pressurizing piston 64 larger, the rise time of the pressure boost can be further shortened.

[0050] In addition, after the hydraulic oil O in the inside B of the injection cylinder 42 is increased to a predetermined pressure, it is necessary to maintain that pressure. Even during this maintenance, part of the force required to maintain the pressure can be borne by the pressure of the hydraulic oil O filled in the hydraulic oil filling space C. This reduces the load on the electric servo motor 60 required to maintain the pressure, and therefore the time for which the pressure is maintained can be extended.

[0051] When the pressure boosting process is completed, the pressurizing piston flow rate control valve 57 goes into a mode of returning the hydraulic oil O filled in the hydraulic oil filling space C to the hydraulic oil reservoir 59, and the electric servo motor 60 rotates in the reverse direction to pull up the pressurizing piston 64. As a result, the hydraulic oil filling space C in the injection cylinder 42 becomes smaller, and the filled hydraulic oil O returns to the hydraulic oil reservoir 59 via the oil piping 44.

[0052] (Variation 1) In the die casting machine 10 according to the embodiment described above, an example of so-called "in-throttling" for adjusting the flow rate of the hydraulic oil O flowing into the IN side B of the injection cylinder 42 in the low-speed injection process and the high-speed injection process has been shown, but instead of this, so-called "out-throttling" for adjusting the flow rate of the hydraulic oil O flowing out from the OUT side A of the injection cylinder 42 may be used. In the case of this "out-throttling", the low-speed side flow rate control valve 50 and the high-speed side flow rate control valve 52 are attached to the oil piping 44 connected to the OUT side A of the injection cylinder 42.

[0053] (Variation 2) Furthermore, in the die casting machine 10 according to the embodiment described above, the pressure applying piston 64 is connected in series to the nut 70 constituting the ball screw 62 in the electric pressure applying mechanism 34, and the nut 70 and the pressure applying piston 64 are moved up and down by rotating the screw shaft 68 with the electric servo motor 60. Alternatively, the pressure applying piston 64 may be connected in series to the screw shaft 68, and the screw shaft 68 and the pressure applying piston 64 may be moved up and down by rotating the nut 70 with the electric servo motor 60.

[0054] (Variation 3) Furthermore, the electric pressure mechanism 34 according to the embodiment described above is merely one example, and instead of connecting the end of the pressure piston 64 in series to the nut 70 of the ball screw 62, for example, a movable plate that presses the pressure piston may be installed between two ball screws, and the pressing force of the ball screws may be applied to the pressure piston via the movable plate.

[0055] Furthermore, instead of arranging the ball screw 62 and the pressure piston 64 vertically so that they move up and down, the ball screw 62 and the pressure piston 64 may be arranged horizontally so that they move substantially horizontally.

[0056] (Variation 4) Furthermore, the timing at which the electric servo motor 60 of the electric pressurizing mechanism 34 starts to operate is not limited to the above-described embodiment, and for example, the electric servo motor 60 may start to operate the nut 70 and the pressurizing piston 64 prior to the start of the pressure increasing step so that the pressurizing piston 64 of the electric pressurizing mechanism 34 is ready to pressurize the hydraulic oil O at the timing at which the high-speed injection step is completed. In this way, since the preparation operation time has elapsed at the time of completion of the high-speed injection step requiring pressure increase, pressure increase can be started at any speed of the electric servo motor 60, and therefore the speed at which the hydraulic pressure is increased to a predetermined pressure after the pressure increasing step is started can be sufficiently ensured using a relatively small and low-output electric servo motor 60, and the electric servo motor 60 can be decelerated from a non-accelerating state, reducing the possibility of the pressure of the hydraulic oil O overshooting.

[0057] In addition, since the timing at which the electric servo motor 60 starts operating prior to the start of the pressure boosting step depends on the preparatory operation time, the start timing may be during the low-speed injection step or during the high-speed injection step. Of course, when the electric servo motor 60 starts operating, the amount of hydraulic oil O flowing into the injection cylinder 42 through the low-speed side flow rate control valve 50 and the high-speed side flow rate control valve 52 is reduced by the amount of movement of the pressurizing piston 64.

[0058] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0059] 10...Die casting machine, 12...Molding device, 14...Injection device, 20...Fixed die plate, 22...Fixed mold, 24...Moving die plate, 26...Moving mold, 28...Cavity, 30...Injection mechanism, 32...Hydraulic operation mechanism, 34...Electric pressure mechanism, 36...Injection sleeve, 38...Injection plunger, 40...Injection piston, 42...Injection cylinder, 43...Water supply port, 44...Oil piping, 46...Hydraulic pump, 48...Control valve, 48a...First control valve, 48b...Second control valve, 50...Low speed side flow control valve, 52...High speed side flow control valve, 5 4...accumulator, 56...pressure sensor, 57...pressurizing piston flow rate control valve, 58...control means, 59...hydraulic oil reservoir, 60...electric servo motor, 62...ball screw, 64...pressurizing piston, 64a...tip portion, 64b...rod portion, 66...guide bar, 68...screw shaft, 70...nut, 72...servo motor mount, 74...screw shaft bearing, 76...guide bar first holding portion, 77...rotating shaft, 78...drive belt, 80...intermediate holding member, 82...guide bar insertion hole, 84...tip holding member, 86...pressurizing piston insertion hole O: hydraulic oil; A: outer side of the injection piston 40; B: inner side of the injection piston 40; C: hydraulic oil filling space of the injection cylinder 42

Claims

1. A die casting machine having an injection mechanism, a hydraulic operation mechanism, and an electric pressure mechanism, The injection mechanism has an injection plunger that injects molten metal into the cavity, The hydraulic operation mechanism includes an injection cylinder that houses the injection plunger, and a hydraulic pump that supplies hydraulic oil to the injection cylinder, the electric pressure mechanism includes an electric servo motor, a ball screw driven by the electric servo motor, and a pressure piston pushed out by the ball screw, The pressurizing piston is pushed into the injection cylinder by the ball screw to increase the pressure of the hydraulic oil, The hydraulic oil from the hydraulic pump is supplied into the injection cylinder so as to push out the pressurizing piston during the pressure increase. Die casting machine.

2. Within the injection cylinder, a hydraulic oil filling space is formed on the opposite side of the movement direction of the pressure applying piston as viewed from the tip end of the pressure applying piston, and into which the hydraulic oil for pushing out the pressure applying piston is supplied.

2. The die casting machine according to claim 1.

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