Die-casting machine

Abstract

To provide a die cast machine constructed simple as a whole and capable of reducing cost.SOLUTION: A die cast machine 10 comprises an injection mechanism 30, a hydraulic operation mechanism 32, and a power pressure mechanism 34. The power pressure mechanism 34 includes a power servo motor 60, a ball screw 62 driven by the power servo motor 60, and a pressure piston 64 extruded by the ball screw 62. The pressure piston 64 is connected in series to a screw shaft 68 or a nut 70 of the ball screw 62 and, only in boosting of an injection step, the pressure piston 64 is extruded into an injection cylinder 42 by the screw shaft 68 or the nut 70 to boost hydraulic oil O.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] In a die-casting machine that has been conventionally used, molten metal melted in a melting furnace is weighed and lifted by a ladle for each shot, the lifted molten metal is fed into a water inlet of an injection sleeve, and the molten metal is injected and filled into a cavity of a mold by the forward movement of an injection plunger provided to be movable forward and backward in the injection sleeve, thereby forming a molded body.

[0003] In an injection process of injecting molten metal into a cavity of a mold, it consists of a low-speed injection process and a subsequent high-speed injection process. In the high-speed injection process, it is necessary to inject and fill the molten metal into the mold at a high injection speed that is about one digit faster than the injection speed of an injection molding machine for molding plastic products.

[0004] Furthermore, after the completion of the high-speed injection process, a pressure boosting process of increasing the pressure of the molding material in the cavity by an injection plunger is carried out (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Incidentally, in conventional die-casting machines, an electric servo motor is used to move a ball screw, which in turn slides the injection piston and increases the pressure of the hydraulic fluid inside the injection cylinder. The electric servo motor operates not only in the pressure-boosting process but also in the low-speed and high-speed injection processes.

[0007] However, attempting to slide the injection piston using an electric servo motor and ball screw presented a problem: the entire system became bulky, increasing the overall cost of the die-casting machine.

[0008] This invention has been made in view of these problems, and its purpose is to provide a die-casting machine that simplifies the overall apparatus and reduces costs. [Means for solving the problem]

[0009] According to one aspect of the present invention, A die-casting machine having an injection mechanism, a hydraulic operating mechanism, and an electric pressurizing mechanism, The injection mechanism has an injection plunger for injecting molten metal into the cavity, The hydraulic operating mechanism includes an injection cylinder that houses the injection plunger and a hydraulic pump that supplies hydraulic fluid to the injection cylinder. The electric pressurizing mechanism comprises an electric servo motor, a ball screw driven by the electric servo motor, and a pressurizing piston pushed out by the ball screw. The aforementioned ball screw has a screw shaft and a nut. The pressurizing piston is connected in series with the screw shaft or the nut, and is pushed into the injection cylinder by the screw shaft or the nut to increase the pressure of the hydraulic fluid. The pressure increase by the aforementioned pressurizing piston is performed only during the pressure increase process. A die-casting machine will be provided.

[0010] Preferably, The screw shaft or nut, and the pressurizing piston are configured to move in the vertical direction. [Effects of the Invention]

[0011] In the die-casting machine according to the present invention, a pressurizing piston connected in series with the screw shaft or nut constituting the ball screw is pushed into the injection cylinder to increase the pressure of the hydraulic fluid. As a result, it is not necessary to slide the injection cylinder itself with the ball screw, thus simplifying the overall device and providing a die-casting machine that can reduce costs. [Brief explanation of the drawing]

[0012] [Figure 1] This is a diagram showing an example of a die-casting machine 10 according to an embodiment. [Figure 2] This figure shows an example of an electric pressurizing mechanism 34 in a die-casting machine 10 according to an embodiment. [Figure 3] This graph shows the changes in the movement speed of the injection plunger 38, the change in the internal pressure of the injection cylinder 42, and the change in the speed of the electric servo motor 60 during the injection process of the die-casting machine 10 according to this embodiment. [Modes for carrying out the invention]

[0013] (Configuration of die-casting machine 10) As shown in Figure 1, the die-casting machine 10 according to this embodiment comprises, broadly speaking, a mold device 12 and an injection device 14.

[0014] The mold apparatus 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. A cavity 28 is formed when the fixed mold 22 and the movable mold 26 are closed together.

[0015] The injection device 14 generally comprises an injection mechanism 30, a hydraulic operating mechanism 32, and an electric pressurizing mechanism 34.

[0016] The injection mechanism 30 has an injection sleeve 36, an injection plunger 38, an injection piston 40, and an injection cylinder 42.

[0017] The injection sleeve 36 is integrally provided with respect to the fixed die plate 20, and is a cylindrical member having a hot water supply port 43 through which molten metal is supplied formed at its upper part.

[0018] The injection plunger 38 is a substantially rod-shaped member provided so as to be able to advance and retreat within the injection sleeve 36.

[0019] 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), and is a part pressed by the hydraulic oil O.

[0020] The injection cylinder 42 is a cylindrical member in which the injection piston 40 advances and retreats, and is filled with hydraulic oil O. Looking from the injection piston 40, the space inside the injection piston 40 in the direction in which the injection piston 40 moves in the injection process is called the out side A, and the opposite in side B.

[0021] The hydraulic operation mechanism 32 is a mechanism for supplying the hydraulic oil O used in the low-speed injection process and the high-speed injection process of the injection plunger 38 to the injection cylinder 42 and acting on the injection piston 40, and generally has an oil pipe 44, a hydraulic pump 46, a plurality of control valves 48, a low-speed side flow rate adjustment valve 50, a high-speed side flow rate adjustment valve 52, an accumulator 54, a pressure sensor 56, and a control means 58.

[0022] The oil pipe 44 constitutes a flow path for sending 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 adjustment valve 50, and the high-speed side flow rate adjustment valve 52, and returning the hydraulic oil O coming out of the injection cylinder 42 back via the control valve 48.

[0023] The hydraulic pump 46 is for pressurizing the hydraulic oil O to the pressure required for the low-speed injection process and the high-speed injection process of the injection plunger 38.

[0024] The control valve 48 includes a first control valve 48a for switching on and off a passage that sends the hydraulic fluid O discharged from the hydraulic pump 46 to the accumulator 54, and a second control valve 48b for switching on and off a passage that returns the hydraulic fluid O from the inlet side B of the injection cylinder 42 to the hydraulic pump 46 side when the injection plunger 38 is returned to the starting position, and also supplies the hydraulic fluid O discharged from the hydraulic pump 46 to the outlet side A of the injection cylinder 42.

[0025] The low-speed side flow control valve 50 is a valve for adjusting the flow rate of the hydraulic fluid O supplied from the accumulator 54, etc., to the inlet side B of the injection cylinder 42 during the low-speed injection process.

[0026] The high-speed side flow control valve 52 is a valve for adjusting the flow rate of the hydraulic fluid O supplied from the accumulator 54, etc., to the inlet side B of the injection cylinder 42 during the high-speed injection process.

[0027] The accumulator 54 is a container for temporarily storing the hydraulic fluid O that has been pressurized by the hydraulic pump 46.

[0028] The pressure sensor 56 is a device for measuring the pressure of the hydraulic fluid O inside the intake side B of the injection cylinder 42.

[0029] The control means 58 is responsible for operating the hydraulic pump 46, control valve 48, low-speed side flow control valve 50, and high-speed side flow control valve 52 while detecting the position information of the injection piston 40 and the pressure signal from the pressure sensor 56 when performing the low-speed injection process, high-speed injection process, pressure boosting process, and return process of the injection plunger 38. This control means 58 also controls the electric pressurizing mechanism 34.

[0030] The electric pressurizing mechanism 34 according to this embodiment will be described in detail with reference to Figure 2. The electric pressurizing mechanism 34 is a mechanism for further pressurizing the hydraulic fluid O sent into the inlet side B of the injection cylinder 42, and generally comprises 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 Figure 2). The ball screw 62 is composed of a screw shaft 68 and a nut 70.

[0031] The electric servo motor 60 rotates the screw shaft 68 of the ball screw 62 via a belt or the like (a gear may also be used), thereby causing the nut 70 to slide relative to the screw shaft 68.

[0032] In this embodiment, the electric servo motor 60 is fixed to a servo motor mount 72. The servo motor mount 72 has a screw shaft bearing 74 that holds the rotating screw shaft 68, and also has a first guide bar holding part 76 that holds one end of each guide bar 66. A drive belt 78 is stretched between the rotating shaft 77 of the electric servo motor 60 and the end of the screw shaft 68, and the rotational force of the rotating shaft 77 of the electric servo motor 60 is transmitted to the screw shaft 68 by this drive belt 78.

[0033] The nut 70 of the ball screw 62 is fixed to an intermediate retaining member 80, which has a guide bar insertion hole 82 through which a guide bar 66 is inserted. By inserting the guide bar 66 through the guide bar insertion hole 82, the intermediate retaining member 80 is guided by the guide bar 66, and the nut 70 can move forward and backward in a predetermined direction (downward in the figure) without wobbling. Also, since the intermediate retaining member 80 is guided by the guide bar 66, the pressurizing piston 64 can move forward and backward in a predetermined direction (downward in the figure) without wobbling.

[0034] Furthermore, the other end of the guide bar 66 is held by a tip holding member 84. This tip holding member 84 has a pressure piston insertion hole 86 through which a pressure piston 64 attached to a nut 70 is inserted. In addition, the injection cylinder 42 has a pressure piston guide hole 88 through which the pressure piston 64 is guided.

[0035] The pressurizing piston 64 is inserted into the inlet side B of the injection cylinder 42 in the hydraulic operating mechanism 32 so that its tip can be moved in and out. When the nut 70 of the ball screw 62 moves downward in the figure, the pressurizing piston 64 enters the inlet side B and pressurizes the hydraulic fluid O filled in the inlet side B.

[0036] As described above, in the electric pressurizing mechanism 34 according to this embodiment, the end of the pressurizing piston 64 is connected in series to the nut 70 of the ball screw 62 via an intermediate holding member 80, so that the nut 70 and the pressurizing piston 64 are in series, and the pressurizing piston 64 is pushed into the injection cylinder 42 to increase the pressure of the hydraulic fluid O. As a result, there is no need to slide the injection piston 40 itself, so the entire device can be made simpler and a die-casting machine 10 that can reduce costs can be provided.

[0037] Furthermore, by connecting the end of the pressurizing piston 64 in series with the nut 70 of the ball screw 62, the weight that the ball screw needs to drive (driving weight) can be reduced compared to a structure in which a movable plate is installed between two ball screws to press the pressurizing piston, and the pressing force from the ball screw is applied to the pressurizing piston via the movable plate. As a result, the inertial force is reduced, which prevents overshoot of the hydraulic fluid O pressure caused by the pressurizing piston.

[0038] Furthermore, in this embodiment, the ball screw 62 and the pressure piston 64 are arranged to move vertically. This makes it possible to reduce the width dimension of the electric pressure mechanism 34 and the entire die-casting machine 10, and provides a die-casting machine 10 that can be installed in relatively narrow spaces.

[0039] (Injection process of die-casting machine 10 according to this embodiment) Next, the injection process in the procedure for forming a molded body using the die-casting machine 10 according to this embodiment will be explained with reference to Figure 3.

[0040] In the die-casting machine 10 according to this embodiment, the injection process is divided into a low-speed injection process, a high-speed injection process, and a pressure-boosting process.

[0041] Before entering the injection process, the control valve 48 of the hydraulic operating mechanism 32 is operated to connect the discharge side of the hydraulic pump 46 to the accumulator 54 and the suction side of the hydraulic pump 46 to the hydraulic oil tank (not shown). In addition, both the low-speed flow control valve 50 and the high-speed flow control valve 52 are closed to a zero flow rate state.

[0042] Subsequently, the hydraulic pump 46 is activated to fill the accumulator 54 with hydraulic fluid O at a predetermined pressure. At the same time, the separately prepared molten metal is filled into the injection sleeve 36.

[0043] The low-speed injection process is initiated. The low-speed flow control valve 50 in the hydraulic operating mechanism 32 is opened, and the hydraulic fluid O from the accumulator 54 (and hydraulic pump 46) is supplied to the inlet side B of the injection cylinder 42, causing the injection plunger 38 to move at a predetermined speed and filling the cavity 28 with molten metal. This low-speed injection process lasts for a few seconds (1 to 2 seconds).

[0044] Subsequently, the high-speed injection process begins. In addition to the low-speed flow control valve 50 in the hydraulic operating mechanism 32, the high-speed flow control valve 52 is opened, and the hydraulic fluid O is supplied to the inlet side B of the injection cylinder 42, moving the injection plunger 38 at a predetermined speed to fill the cavity 28 with molten metal. The high-speed injection process lasts for a few hundredths of a second. When the high-speed injection process is completed, the low-speed flow control valve 50 and the high-speed flow control valve 52 are closed.

[0045] Incidentally, the injection process of the die-casting machine 10 according to this embodiment is characterized by the operation of the electric pressurizing mechanism 34. Specifically, prior to the start of the pressurizing process, the electric servo motor 60 is started to operate, thereby starting the operation of the nut 70 and the pressurizing piston 64, so that the preparation for pressurizing the hydraulic fluid O by the pressurizing piston 64 of the electric pressurizing mechanism 34 is completed at the time the high-speed injection process described above is completed.

[0046] This is because, immediately after the electric servo motor 60 of the electric pressurizing mechanism 34 starts operating, the belt between the electric servo motor 60 and the screw shaft 68 of the ball screw 62 stretches slightly, and due to backlash between the screw shaft 68 and the nut 70, as well as inertial force due to the drive weight, the rotational force of the electric servo motor 60 is not fully transmitted to the nut 70 via the screw shaft 68. It takes some time after the electric servo motor 60 starts operating for the rotational force to be fully transmitted to the nut 70. This time is called the "preparation time".

[0047] If the pressure build-up time in the pressure-boosting process is slow, the molten metal filling cavity 28 will solidify too quickly, raising concerns that this could degrade the quality of the finished molded product.

[0048] Therefore, if the electric servo motor 60 is started at the same time as the high-speed injection process is completed, the speed at which the hydraulic pressure is increased to a predetermined pressure after entering the pressure-boosting process depends on the acceleration of the electric servo motor, making it difficult to adequately guarantee the speed at which the hydraulic pressure is increased to a predetermined pressure (i.e., the pressure rise time).

[0049] Furthermore, equipping the die-casting machine with a large, high-power electric servo motor to speed up the pressure build-up time would lead to an increase in the overall cost of the machine.

[0050] Furthermore, if one attempts to speed up the pressure rise time by relying on the acceleration of an electric servo motor, it becomes necessary to continue accelerating until the hydraulic pressure reaches a predetermined level, and then rapidly decelerate the electric servo motor as it approaches that level. This acceleration-to-rapid deceleration process makes it easy for an overshoot to occur, where the hydraulic pressure spikes and exceeds the predetermined level.

[0051] In this regard, in the electric pressurizing mechanism 34 according to this embodiment, as described above, by starting the operation of the electric servo motor 60 and the operation of the nut 70 and pressurizing piston 64 prior to the start of the pressurizing process, the preparation time has elapsed by the time the high-speed injection process requiring pressurizing is completed, so pressurizing can be started at any speed of the electric servo motor 60.

[0052] This ensures that the relatively small, low-power electric servo motor 60 can be used to quickly raise the hydraulic pressure to a predetermined level after entering the pressure-boosting process, and also reduces the possibility of the hydraulic fluid O pressure overshooting because the electric servo motor 60 can be decelerated from a non-accelerating state.

[0053] The timing of starting the operation of the electric servo motor 60 prior to the start of the pressure-boosting process depends on the preparation time, so this start timing may be during the low-speed injection process or during the high-speed injection process. Of course, when the electric servo motor 60 starts operating, the amount of hydraulic fluid O flowing into the injection cylinder 42 through the low-speed flow control valve 50 and the high-speed flow control valve 52 is reduced by the amount that the pressurizing piston 64 moves.

[0054] (Variation 1) In the die-casting machine 10 according to the above embodiment, an example of a so-called "inlet throttle" was shown to adjust the flow rate of the hydraulic fluid O flowing into the inlet side B of the injection cylinder 42 during the low-speed injection process and the high-speed injection process. However, instead, a so-called "outlet throttle" may be used to adjust the flow rate of the hydraulic fluid O flowing out from the outlet side A of the injection cylinder 42. In the case of this "outlet throttle," the low-speed side flow control valve 50 and the high-speed side flow control valve 52 are attached to the oil piping 44 connected to the outlet side A of the injection cylinder 42.

[0055] (Modification 2) Furthermore, in the die-casting machine 10 according to the above embodiment, a pressure piston 64 was connected in series to a nut 70 constituting the ball screw 62 in the electric pressure mechanism 34, and the nut 70 and pressure piston 64 were moved vertically by rotating the screw shaft 68 with an electric servo motor 60. However, instead, the pressure piston 64 may be connected in series to the screw shaft 68, and the screw shaft 68 and pressure piston 64 may be moved vertically by rotating the nut 70 with an electric servo motor 60.

[0056] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0057] 10…Die casting machine, 12…Mold 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 operating mechanism, 34…Electric pressurization mechanism, 36…Injection sleeve, 38…Injection plunger, 40…Injection piston, 42…Injection cylinder, 43…Hot water inlet, 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 flow control valve, 54... Accumulator, 56... Pressure sensor, 58... Control means, 60... Electric servo motor, 62... Ball screw, 64... Pressurizing piston, 66... ​​Guide bar, 68... Screw shaft, 70... Nut, 72... Servo motor mount, 74... Screw shaft bearing, 76... Guide bar first holding part, 77... Rotating shaft, 78... Drive belt, 80... Intermediate holding member, 82... Guide bar insertion hole, 84... Tip holding member, 86... Pressurizing piston insertion hole, 88... Pressurizing piston guide hole O...Hydraulic fluid, A...Outlet side of injection piston 40, B...Inlet side of injection piston 40

Claims

1. A die-casting machine having an injection mechanism, a hydraulic operating mechanism, and an electric pressurizing mechanism, The injection mechanism has an injection plunger for injecting molten metal into the cavity, The hydraulic operating mechanism includes an injection cylinder that houses the injection plunger and a hydraulic pump that supplies hydraulic fluid to the injection cylinder. The electric pressurizing mechanism comprises an electric servo motor, a ball screw driven by the electric servo motor, and a pressurizing piston pushed out by the ball screw. The aforementioned ball screw has a screw shaft and a nut. The pressurizing piston is connected in series with the screw shaft or the nut, and is pushed into the injection cylinder by the screw shaft or the nut to increase the pressure of the hydraulic fluid. The pressure increase by the aforementioned pressurizing piston is performed only during the pressure increase process. Die-casting machine.

2. The screw shaft or nut, and the pressurizing piston are configured to move in the vertical direction. The die-casting machine according to claim 1.

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