Die-casting machine and die-casting method

Abstract

To provide a die-cast machine and a die-casting method that has faster changeover responsiveness from a high-speed injection process to a surge pressure process and can achieve high-quality casting with stabilization of a molten metal flow.SOLUTION: A machine comprises a hydraulic driving part for supplying hydraulic pressure to an injection cylinder driving a plunger and is characterized that: the hydraulic driving part comprises an accumulator, a flow passage adjustment part, a gas bottle for speed adjustment, and a gas bottle for pressure adjustment; and the flow passage adjustment part adjusts a passage for pressurized gas to be supplied to the accumulator based on a working position of the plunger to switch the process from a high-speed injection process using the gas bottle for speed adjustment to a surge pressure process using the gas bottle for pressure adjustment.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a die-casting machine and a die-casting method for injecting and filling molten metal into a mold cavity by a plunger that can move forward and backward freely within an injection sleeve into which the molten metal is supplied.

Background Art

[0002] A die-casting method by die-casting using molten metal such as an aluminum alloy is performed in the following procedure. First, the molten metal is supplied into the injection sleeve. Next, by the forward movement of a plunger that is disposed in the injection sleeve so as to be able to move forward and backward, the molten metal in the injection sleeve is injected and filled into the mold cavity (injection filling step). Thereafter, through a pressure increasing step of increasing the density of the filled molten metal, a pressure holding step of applying a pressure holding force to compensate for the cooling and solidification shrinkage of the molten metal, and a cooling step of cooling and solidifying the molten metal, a cast product is taken out from the mold cavity. This series of molding steps is repeated until the planned number of cast products is obtained.

[0003] Here, the injection filling step is divided into a low-speed injection step of pressing the molten metal in the injection sleeve at a low speed to discharge air and gas in the injection sleeve and increase the filling rate of the molten metal in the injection sleeve, and a high-speed injection step of pressing the molten metal in the injection sleeve at a high speed to inject and fill the molten metal into the mold cavity at a high speed. Further, the pressure increasing step plays a role of pressing the molten metal in the injection sleeve at a high pressure to increase the pressure of the molten metal in the mold cavity, completely filling the mold cavity with the molten metal, and increasing the filling density of the molten metal. When switching from this high-speed injection step to the pressure increasing step, if the responsiveness is poor, casting defects caused by the flow of the molten metal such as flow marks, poor flow around the molten metal, flash, and shrinkage cavities occur due to the temporary stop of the flow of the molten metal, a large change in the flow velocity of the flow of the molten metal, or a delay in the pressurizing action on the flow of the molten metal.

[0004] Therefore, an injection device with high switching responsiveness from the high-speed injection process to the pressure boosting process has been proposed. Here, in terms of the flow velocity of the molten metal passing through the gate portion of the mold cavity, for example, in the low-speed injection process, a slow injection speed of around 1 m / s can be set, and in the high-speed injection process, a fast injection speed exceeding 10 m / s can be set. Therefore, an injection device that can handle speeds from low to high and has high switching responsiveness as described above is desired.

[0005] For example, an injection device has been proposed that includes a drive unit (injection cylinder) connected to a plunger within an injection sleeve, a speed accumulator capable of supplying hydraulic fluid (hydraulic oil) to the injection cylinder, and a pressure boosting accumulator that generates a driving force transmitted to the plunger, as shown in Patent Document 1. By calculating the required pressure of the speed accumulator in the high-speed injection process, it is said that the switching responsiveness from the high-speed injection process to the pressure boosting process can be enhanced, the surge pressure can be reduced, and casting defects such as flash can be improved.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Here, the speed accumulator and the boost accumulator of the means shown in Patent Document 1 are arranged so as to supply hydraulic oil to the injection cylinder through different paths. Therefore, when switching the supply of hydraulic oil from the speed accumulator to the boost accumulator, at least two path switching operations are required. In other words, when switching between these two paths, the supply of hydraulic oil to the drive unit necessarily stops for an instant, or the hydraulic oil flows back instantaneously due to a pressure difference, causing the operation of the drive unit to waver, greatly disturbing the flow of the molten metal during injection filling, making it difficult to improve casting defects caused by disturbances in the flow of the molten metal, such as molten metal wrinkles, poor molten metal running, casting burrs, and casting cavities. In addition, hydraulic oil used in hydraulic pressure is said to be close to a non-compressible fluid with extremely small pressure fluctuations, and a temporary stop or disturbance in the supply of hydraulic oil directly leads to disturbances in the operation of the drive unit and the flow of the molten metal. In particular, in the high-speed injection process, the disturbances are noticeable. Therefore, when switching from the high-speed injection process to the pressure boosting process, it is considered that a means for switching the supply of hydraulic oil is not preferable.

[0008] Therefore, an object of the present invention is to provide a die casting machine and a die casting method that have a high response when switching from the high-speed injection process to the pressure boosting process and can achieve high quality casting by stabilizing the flow of molten metal. [Means for solving the problem]

[0009] The die casting machine of the present invention is a die casting machine in which molten metal is injected and filled into a mold cavity by a plunger that moves freely back and forth within an injection sleeve to which the molten metal is supplied, and is characterized in that it is equipped with a hydraulic drive unit that supplies hydraulic pressure to an injection cylinder that drives the plunger, and the hydraulic drive unit is equipped with an accumulator, a flow path adjustment unit, a speed adjustment gas bottle, and a pressure adjustment gas bottle, and the flow path adjustment unit adjusts the flow path of pressurized gas supplied to the accumulator based on the operating position of the plunger, and switches from the speed adjustment gas bottle to the pressure adjustment gas bottle.

[0010] In the die-casting machine of the present invention, the accumulator includes an operating oil chamber for storing hydraulic operating oil, a gas chamber for storing pressurized gas, and an airtight member that hermetically partitions and slidably separates the operating oil chamber and the gas chamber. The speed adjustment gas bottle and the gas chamber are connected via the flow path adjustment unit, and the injection cylinder and the operating oil chamber are connected via an operating oil adjustment unit that adjusts the flow of the operating oil. This is preferable.

[0011] The die-casting method of the present invention includes a low-speed injection step of pressing the molten metal in the injection sleeve at a low speed, a high-speed injection step of pressing the molten metal in the injection sleeve at a high speed and injecting and filling it into the mold cavity, and a pressure boosting step of pressing the molten metal in the injection sleeve at a high pressure and pressing the molten metal injected and filled into the mold cavity. The flow path adjustment unit adjusts the flow paths of the speed adjustment gas bottle and the pressure adjustment gas bottle based on the operating position of the plunger to switch from the high-speed injection step to the pressure boosting step. This is the gist of the invention.

[0012] In the die-casting method of the present invention, it is preferable that in the low-speed injection step and the high-speed injection step, pressurized gas is supplied from the speed adjustment gas bottle to the accumulator to adjust the flow of the operating oil supplied from the accumulator to the injection cylinder.

[0013] Also, in the die-casting method of the present invention, in the pressure boosting step, it is preferable that pressurized gas is supplied from the pressure adjustment gas bottle to the accumulator to adjust the flow of the operating oil supplied from the accumulator to the injection cylinder.

Advantages of the Invention

[0014] According to the present invention, it is possible to provide a die-casting machine and a die-casting method that achieve high switching responsiveness from the high-speed injection step to the pressure boosting step and high quality of the casting quality due to the stabilization of the molten metal flow.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0016] Hereinafter, preferred embodiments for carrying out the present invention will be described with reference to the drawings. Note that the following embodiments do not limit the invention according to each claim. Also, not all combinations of features described in the embodiments are essential for the solution means of the invention according to each claim. Further, in the present embodiment, there are cases where the scales and dimensions of each component are exaggerated or some components are omitted.

[0017] [Die-casting machine] The die-casting machine according to the present embodiment will be described with reference to FIG. 1. FIG. 1 shows a conceptual diagram of the die-casting machine. In the following description, a horizontal die-casting machine is used as the die-casting machine according to the present embodiment, but it is not limited thereto. The die-casting machine 100 shown in FIG. 1 includes a casting mold 10, an injection unit 20, an injection cylinder 30, a hydraulic drive unit 40, and an injection control unit 50 that controls the operation of the hydraulic drive unit 40 to inject and fill the molten metal into the mold cavity 13.

[0018] The casting mold 10 includes a fixed mold 11 and a movable mold 12 attached to a mold clamping device (not shown), and a mold cavity 13 formed by clamping the fixed mold 11 and the movable mold 12. The mold cavity 13 is connected to the injection device 20 via a gate 14, and a casting product is formed by injecting and filling the molten metal from the injection device 20 into the mold cavity 13.

[0019] The injection unit 20 includes a cylindrical injection sleeve 21, a plunger 22 that is disposed to be able to advance and retreat within the injection sleeve 21, and a rod 23 that connects the plunger 22 and the injection cylinder 30. Using a molten metal supply device (not shown) or the like, molten metal is supplied into the injection sleeve 21 from the pouring port 24. Further, the injection sleeve 21 and the plunger 22 are provided with a cooling mechanism (not shown) that includes a flow path through which a cooling medium such as cooling water flows, as necessary. Further, in order to prevent wear and damage of the plunger 22, stabilize the sliding state, and suppress adhesion of molten metal residue, it is preferable to apply a lubricant to the sliding surface between the injection sleeve 21 and the plunger 22. Further, a vacuum suction path (not shown) or the like may be provided in the injection sleeve 21, and a form may be adopted in which vacuum suction within the injection sleeve 21 and the mold cavity 13 is combined with injection filling of molten metal.

[0020] Here, regarding the operation of the plunger 22, the direction closer to the mold cavity 13 is defined as the front F, the operation in the front F direction is defined as the forward operation, the direction farther from the mold cavity 13 is defined as the rear B, and the operation in the rear B direction is defined as the retreat operation. By the forward operation of the plunger 22, the molten metal in the injection sleeve 21 supplied from the pouring port 24 is injection-filled into the mold cavity 13 via the gate 14. While the plunger 22 performs a retreat operation and waits on the rear B side of the pouring port 24, molten metal is supplied into the injection sleeve portion 21. Further, the operation position of the plunger 22 is measured by a position sensor (not shown) or the like, and the measurement result is transmitted to the injection control unit 50 and used for controlling the injection filling of molten metal. Note that the operation position of the plunger 22 may be determined by measuring the operation position of the rod 23.

[0021] The injection cylinder 30 includes an integrated cylinder rod 32 and a cylinder head 34 that slide forward and backward freely within a cylindrical cylinder container 31. The tip of the cylinder rod 32 is detachably connected to the rod 23 by a connecting portion 33, and the injection cylinder 30 performs the forward and backward movement of the plunger 22. The injection cylinder 30 is hydraulically driven, and by controlling the flow of hydraulic oil in the space on the cylinder head 34 side of the cylinder container 31 (referred to as the head side hydraulic chamber 34a) and the space on the cylinder rod 32 side (referred to as the rod side hydraulic chamber 32a), the forward speed (referred to as the injection speed) and forward pressure (referred to as the injection pressure) during the forward movement of the plunger 22, and the backward speed during the backward movement can be controlled. Specifically, it will be described in the die-casting method described later. Also, the operating positions of the cylinder rod 32, the cylinder head 34, or the connecting portion 33 may be measured by a position sensor (not shown) or the like and used as the operating position of the plunger 22.

[0022] The hydraulic drive unit 40 is characterized in that a gas bottle for speed adjustment (441, 442) and a gas bottle for pressure adjustment 46 are arranged in parallel with respect to one accumulator 41 via a flow path adjustment unit 43. Further, based on the operating position of the plunger 22, the flow path adjustment unit 43 is operated to switch the flow paths of the gas bottles for speed adjustment (441, 442) and the gas bottle for pressure adjustment 46. By this switching operation, the hydraulic control is switched between the high-speed injection process and the pressure boosting process in injection filling.

[0023] The accumulator 41 includes an operating oil chamber 41a for storing hydraulic operating oil, a gas chamber 41b for storing pressurized gas, and an airtight member 41c that hermetically partitions and slidably separates the operating oil chamber 41a and the gas chamber 41b, and is disposed within a sealed container 41d. The operating oil chamber 41a and the head-side hydraulic chamber 34a of the injection cylinder 30 are connected via an operating oil adjustment unit 42 that adjusts the flow of the hydraulic operating oil. Further, the gas chamber 41b, the speed adjustment gas bottles (441, 442), and the pressure adjustment gas bottle 46 are connected via a flow path adjustment unit 43. Between the speed adjustment gas bottles (441, 442) and the flow path adjustment unit 43, speed adjustment gas adjustment units (451, 452) for adjusting the gas flow are provided, and between the pressure adjustment gas bottle 46 and the flow path switching valve 43, a pressure adjustment gas adjustment unit 47 is provided. In FIG. 1, two speed adjustment gas bottles and one pressure adjustment gas bottle are shown, but the present invention is not limited thereto, and the number of each gas bottle may be appropriately set. Further, an accumulator having an airtight member is used, but the present invention is not limited thereto, and for example, an accumulator in which the operating oil chamber and the gas chamber are hermetically partitioned and slidably separated using a balloon may also be used.

[0024] [Die Casting Method] Next, a die casting method using the die casting machine shown in FIG. 1 will be described with reference to FIG. 2. FIG. 2 is a flowchart showing the casting and molding process of the die casting method. The plunger 22 waits at a predetermined position, molten metal is supplied into the injection sleeve 21, and the fixed die 11 and the movable die 12 are clamped to form a die cavity 13. The description will start from the state where the casting and molding starts.

[0025] First, the injection control unit 50 starts the pressurized gas control using the accumulator 41. The flow path adjustment unit 43 is operated to switch the flow path of the pressurized gas from the neutral position to the V position, and the pressurized gas is supplied from the gas bottles for speed adjustment (441, 442) to the gas chamber 41b. At this time, the flow of the pressurized gas is adjusted by the gas regulators for speed adjustment (451, 452). Due to the supply of the pressurized gas to the gas chamber 41b, the airtight member 41c is pressed and moves. Along with the movement of the airtight member 41c, the working oil is supplied from the working oil chamber 41a to the head-side hydraulic chamber 34a of the injection cylinder 30, the cylinder head 34 is pressed, and the plunger 22 starts to move forward in the forward F direction via the cylinder rod 32 and the rod 23, pressing the molten metal in the injection sleeve 21, and the injection filling process is started. Here, the injection filling process is divided into a low-speed injection process of pressing the molten metal in the injection sleeve 21 at a low speed to discharge the air and gas in the injection sleeve 21 and increase the filling rate of the molten metal in the injection sleeve 21, and a high-speed injection process of pressing the molten metal in the injection sleeve 21 at a high speed to inject and fill the molten metal into the mold cavity 13 at a high speed.

[0026] In the low-speed injection process, the injection speed is controlled (meter-out control) by operating the discharge adjustment unit 35 to adjust the discharge amount of the working oil in the rod-side hydraulic chamber 32a of the injection cylinder 30. Separately from this, it may also be a means (meter-in control) of controlling the injection speed by adjusting the working oil adjustment unit 42 to adjust the supply amount of the working oil supplied from the working oil chamber 41a to the head-side hydraulic chamber 34a. Alternatively, the meter-out control and the meter-in control may be performed simultaneously. Note that in the low-speed injection process, a slow injection speed of, for example, around 1 m / s is set in terms of the flow rate of the molten metal passing through the gate 14 of the mold cavity 13. Therefore, it is also possible to operate the gas regulators for speed adjustment (451, 452) and supply the pressurized gas using only one of the two gas bottles for speed adjustment (441, 442).

[0027] When the injection control unit 50 detects that the operating position K of the plunger 22 has reached the preset speed switching position K1 (K = K1), the injection process switches from the low-speed injection process to the high-speed injection process. Also in the high-speed injection process, similar to the low-speed injection process, the injection speed is controlled by meter-out control. Naturally, meter-in control, meter-out control, and the simultaneous use of meter-in control may also be used. Note that in the high-speed injection process, for example, since a high injection speed exceeding 10 m / s is set, it is preferable to operate the gas regulators for speed adjustment (451, 452) and use two gas bottles for speed adjustment (441, 442). Further, when the discharge of the hydraulic oil from the discharge regulator 35 is not in time, the discharge control of the hydraulic oil from the hydraulic circuit regulator 36 (meter-out control) may be combined.

[0028] When the injection control unit 50 detects that the operating position K of the plunger 22 has reached the preset pressure boosting switching position K2 (K = K2), the injection process switches from the high-speed injection process to the pressure boosting process. The flow path regulator 43 is operated to switch the flow path of the pressurized gas from the V position to the P position, and the supply of the pressurized gas to the gas chamber 41b is switched from the gas bottles for speed adjustment (441, 442) to the gas bottle for pressure adjustment 46. During the supply of the pressurized gas, the gas regulator for pressure adjustment 47 is opened.

[0029] Here, the pressurized gas is a gas obtained by pressurizing a gas such as air or nitrogen gas, and is a compressed fluid whose volume changes greatly depending on the pressure. The compressibility of the pressurized gas is 10,000 times greater than that of the hydraulic oil of the hydraulic pressure. Therefore, when operating the flow path regulator 43, even if the supply of the pressurized gas stops instantaneously, the fluctuation of the pressurized gas in the gas chamber 41b is extremely small, and no fluctuation occurs in the pressing of the airtight member 41c. As a result, the hydraulic oil supplied from the hydraulic oil chamber 41a to the head-side hydraulic oil chamber 34a also does not fluctuate, and the injection cylinder 30 can maintain a stable forward movement, and the switching from the high-speed injection process to the pressure boosting process is smoothly performed.

[0030] In contrast, for comparison, a conventional die-casting machine and a die-casting method will be described with reference to FIGS. 3 and 4. FIG. 3 shows a conceptual diagram of a conventional die-casting machine 100D, and FIG. 4 shows a flowchart of die-casting forming using the conventional die-casting machine 100D. Note that descriptions of portions overlapping with FIGS. 1 and 2 and portions not related to the operation of the present invention will be omitted, and different portions will be described in detail.

[0031] First, in the conventional die-casting machine 100D shown in FIG. 3, the differences from FIG. 1 are the hydraulic drive unit 60 and the injection control unit 70. The hydraulic drive unit 60 arranges two accumulators, namely an accumulator 61 for speed adjustment and an accumulator 65 for pressure adjustment. Also, the accumulator 61 for speed adjustment and the gas bottles (631, 632) for speed adjustment are connected via gas on-off valves (641, 642) for speed adjustment, and the accumulator 65 for pressure adjustment and the gas bottle 67 for pressure adjustment are connected via a gas on-off valve 68 for pressure adjustment. Further, the accumulator 61 for speed adjustment and the hydraulic chamber 34a on the head side of the injection cylinder 30 are connected via an operating oil on-off valve 62 for speed adjustment, and the accumulator 65 for pressure adjustment and the hydraulic chamber 34a on the head side are connected via an operating oil on-off valve 66 for pressure adjustment. That is, the accumulator 61 for speed adjustment and the accumulator 65 for pressure adjustment are connected to the injection cylinder 30 through different paths and are configured to control the operation of the injection cylinder 30 through different paths.

[0032] Next, die-casting forming using the conventional die-casting machine 100D will be described with reference to FIG. 4. Molten metal is supplied into the injection sleeve 21, and die-casting forming is started from the state where the mold cavity 13 is formed, and pressure gas control by the injection control unit 70 is started.

[0033] First, close the pressure regulating gas on-off valve 68 and the pressure regulating hydraulic oil on-off valve 66 to close the connection between the pressure regulating accumulator 65 and the injection cylinder 30. Then, open the speed regulating gas on-off valves (641, 642) and the speed regulating hydraulic oil on-off valve 62 to open the connection between the speed regulating accumulator 61 and the injection cylinder 30. By these two operations, pressurized gas is supplied from the speed regulating gas bottles (631, 632) to the gas chamber 61b of the speed regulating accumulator 61, pressing the piston 61c, and hydraulic oil is supplied from the hydraulic oil chamber 61a to the head-side hydraulic oil chamber 34a of the injection cylinder 30, starting the injection filling process. Similar to FIG. 2, the injection filling process combines a low-speed injection process and a high-speed injection process. The low-speed injection process and the high-speed injection process are controlled for injection speed by appropriately combining meter-out control, meter-in control, and proper use of the two speed regulating gas bottles (631, 632), similar to FIG. 2. Also, the switching between the low-speed injection process and the high-speed injection process is also controlled based on the operating position of the plunger 22, similar to FIG. 2.

[0034] When the injection control unit 70 detects that the operating position K of the plunger 22 has reached the preset pressure increasing switching position K2 (K = K2), the process switches from the high-speed injection process to the pressure increasing process. First, close the speed regulating gas on-off valves (641, 642) and the speed regulating hydraulic oil on-off valve 62 to close the connection between the speed regulating accumulator 61 and the injection cylinder 30. Then, open the pressure regulating gas on-off valve 68 and the pressure regulating hydraulic oil on-off valve 66 to open the connection between the pressure regulating accumulator 65 and the injection cylinder 30. By these two operations, the supply of hydraulic oil to the head-side hydraulic oil chamber 34a is temporarily stopped. Here, the hydraulic oil for hydraulic pressure is considered to be a non-compressible fluid with an extremely small compression ratio compared to gases such as air and nitrogen gas used for pressurized gas. Therefore, due to the temporary stop of the supply of hydraulic oil, the operation of the injection cylinder 30 is greatly disturbed, the forward movement of the plunger 22 becomes unstable, and the molten metal flow may be greatly disturbed. As a result, the risk of casting defects such as sink marks, flow marks, flash, and porosity caused by the disturbance of the molten metal flow is further increased.

[0035] In addition, even if the connection between the pressure regulating accumulator 65 and the injection cylinder 30 is suddenly opened after the supply of the hydraulic oil is temporarily stopped, the operation of the injection cylinder 30 will also be greatly disturbed. Pressurized gas is supplied from the pressure regulating gas bottle 67 to the gas chamber 65b of the pressure regulating accumulator 65, pressing the piston 65c, and hydraulic oil is suddenly supplied from the hydraulic oil chamber 65a to the head-side hydraulic oil chamber 34a where the supply of the hydraulic oil is temporarily stopped and the pressure of the hydraulic oil has decreased. As a result, the plunger 22 suddenly accelerates as if it pops out, the pressure of the molten metal in the injection through portion 21 suddenly increases, which causes serious casting defects such as flash. Thus, in the prior art, when switching from the high-speed injection process to the pressure boosting process, the hydraulic pressure fluctuates greatly and the operation of the plunger 22 is greatly disturbed.

[0036] Return to the description of FIG. 2. The pressure boosting process presses the molten metal in the injection sleeve 21 at high pressure to increase the pressure of the molten metal in the mold cavity 13, completely fill the inside of the mold cavity 13 with the molten metal, and plays a role in increasing the filling density of the molten metal. Depending on the type of molten metal, melting temperature, volume of the mold cavity 13, flow length of the molten metal including the gate 14, etc., it is adjusted to a pressure of, for example, around 100 MPa in terms of molten metal pressure. Pressurized gas is supplied from the pressure regulating gas bottle 46 to the gas chamber 41b of the accumulator 41 via the flow path regulating unit 43, pressing the airtight member 41c, and hydraulic oil is supplied from the hydraulic oil chamber 41a to the head side hydraulic oil chamber 34a of the injection cylinder 30. As a result, a forward pressure acts on the plunger 22 via the cylinder head 34, the cylinder rod 32, and the rod 23, and the molten metal in the injection sleeve 21 can be pressed at high pressure. The control of the forward pressure of the plunger 22 is meter-out control by operating the discharge regulating unit 35, similar to the low-speed injection process or the high-speed injection process. Note that it may be meter-out control by operating the hydraulic circuit regulating unit 36, or these two may be combined. Also, it may be meter-in control by operating the hydraulic oil regulating unit 42 or the pressure regulating gas regulating unit 47, or meter-out control and meter-in control may be combined. Furthermore, it may be a means of controlling the pressure of the pressurized gas supplied from the pressure regulating gas bottle 46 to the gas chamber 41b in multiple stages to control the pressure of the pressure boosting process in multiple stages, or a configuration called a run-around circuit that supplies the hydraulic oil discharged from the rod side hydraulic oil chamber 32a of the injection cylinder 30 to the head side hydraulic oil chamber 34a may be used.

[0037] Next, when the elapsed time T = T1 preset by the injection control unit 50 is confirmed, the holding pressure process proceeds. The holding pressure process plays a role in compensating for the solidification shrinkage accompanying the cooling and solidification of the molten metal in the injection-filled mold cavity 13, and presses the molten metal in the injection sleeve 21 to apply a holding pressure. Alternatively, a holding pressure may be applied using a pressurizing mechanism (not shown) provided in the casting mold 10. Also, the two means may be combined to apply the holding pressure. When pressing the molten metal in the injection sleeve 21, it is performed by appropriately adjusting the pressing force in the same procedure as the pressure boosting process.

[0038] After that, at elapsed time T = T2, the process proceeds to the cooling process, and at elapsed time T = T3, the pressurized gas control is terminated, and the casting forming is completed. Note that the pressurized gas control may be terminated first when the molten metal in the injection sleeve 21 cools and solidifies. After the casting forming is completed, the process proceeds to the preparation process for the next shot. First, the casting mold 10 is opened, and the cast product that has cooled and solidified in the mold cavity 13 is taken out. The plunger 22 is retracted to a predetermined position at the rear B, and the casting mold 10, the injection sleeve 21, and the plunger 22 are cleaned and the mold is prepared such as by applying a mold release agent. After that, the casting mold 10 is closed to form the mold cavity 13. Then, molten metal is supplied into the injection sleeve 21, and the casting forming for the next shot is started. Note that by the retraction operation of the plunger 22, the cylinder head 34 of the injection cylinder 30 returns to the normal position.

[0039] In parallel with the preparation process for the next shot, the hydraulic oil is replenished to the accumulator 41, and the pressurized gas is replenished to the pressure regulating gas bottle 46 and the speed regulating gas bottles (441, 442). First, for the replenishment of the hydraulic oil, for example, the hydraulic oil adjustment unit 42 is operated to supply the hydraulic oil from the hydraulic oil supply source 37 to the hydraulic oil chamber 41a. By replenishing the hydraulic oil, the airtight member 41c moves and returns to the normal position. The pressurized gas in the compressed gas chamber 41b compressed by the movement of the airtight member 41c may be used for replenishing the pressurized gas to each gas bottle, but it is preferable to replenish the pressurized gas using a booster device (not shown) or the like. For example, the pressure regulating gas adjustment unit 47 is operated to replenish the pressurized gas from the booster device to the pressure regulating gas bottle 46. Similarly, the speed regulating adjustment units (451, 452) are operated to replenish the pressurized gas from the booster device to the speed regulating gas bottles (441, 442). It is desirable to complete this replenishment of the hydraulic oil and the pressurized gas within the scope of the preparation process for the next shot.

[0040] As described above, with the configuration of the die-casting machine 100 shown in FIG. 1, when switching from the high-speed injection process to the pressure-increasing process, by utilizing the characteristics of the pressurized gas, which is a compressed fluid, the hydraulic pressure fluctuation is small, and the smooth forward movement of the plunger 22 can be maintained by the stable operation of the injection cylinder 30. Further, since the switching operation from the high-speed injection process to the pressure-increasing process can be realized by one operation of the flow path adjustment unit 43, a die-casting machine with high switching responsiveness can be provided. Furthermore, by performing die-casting using the die-casting machine shown in FIG. 1, when switching from the high-speed injection process to the pressure-increasing process, the molten metal exhibits stable flow, so casting defects caused by molten metal flow such as sink marks, flow-around defects, and flash can be reliably prevented, and a die-casting method for obtaining high-quality cast products can be provided.

[0041] As described above, the preferred embodiments of the present invention have been described, but the technical scope of the present invention is not limited to the scope described in the above-described embodiments. Various changes or improvements can be made to the above embodiments.

Explanation of Reference Numerals

[0042] 10 Die casting mold 11 Fixed mold 12 Movable mold 13 Mold cavity 14 Gate 20 Injection unit 21 Injection sleeve 22 Plunger 23 Rod 24 Pouring port 30 Injection cylinder 31 Cylinder container 32 Cylinder rod 32a Rod-side hydraulic chamber 33 Connecting part 34 Cylinder head 34a Head-side hydraulic chamber 35 Discharge adjustment unit 36 Hydraulic circuit adjustment unit 37 Hydraulic supply source 40 Hydraulic drive unit 41 Accumulator 41a Hydraulic oil chamber 41b Gas chamber 41c Hermetic member 41d Sealed container 42 Hydraulic oil adjustment unit 43 Flow path adjustment unit 441, 442 Gas bottles for speed adjustment 451, 452 Gas adjustment units for speed adjustment 46 Gas bottle for pressure adjustment 47 Gas adjustment unit for pressure adjustment 50 Injection control unit 100 Die casting machine

Claims

1. In a die-casting machine that injects and fills molten metal into a mold cavity by a plunger that moves forward and backward freely within an injection sleeve to which the molten metal is supplied, a low-speed injection step of pressing the molten metal in the injection sleeve at a low speed, a high-speed injection step of pressing the molten metal in the injection sleeve at a high speed and injecting and filling it into the mold cavity, and a pressure boosting step of pressing the molten metal in the injection sleeve at a high pressure and pressing the molten metal injected and filled into the mold cavity are performed. It is provided with a hydraulic drive unit that supplies hydraulic pressure to an injection cylinder that drives the plunger. The hydraulic drive unit includes an accumulator, a flow path adjustment unit, a gas bottle for speed adjustment, and a gas bottle for pressure adjustment. The gas bottle for speed adjustment supplies hydraulic pressure to the injection cylinder via the accumulator in the high-speed injection step. The gas bottle for pressure adjustment supplies hydraulic pressure to the injection cylinder via the accumulator in the pressure boosting step. The flow path adjustment unit adjusts the flow path of the pressurized gas supplied to the accumulator based on the operating position of the plunger so as to switch from the high-speed injection step to the pressure boosting step, and switches from the gas bottle for speed adjustment to the gas bottle for pressure adjustment. A die-casting machine characterized by this.

2. The accumulator includes an operating oil chamber that stores hydraulic operating oil, a gas chamber that stores pressurized gas, and an airtight member that hermetically partitions and slidably moves the operating oil chamber and the gas chamber. The die-casting machine according to claim 1, wherein the gas bottle for speed adjustment and the gas chamber are connected via the flow path adjustment unit, and the injection cylinder and the operating oil chamber are connected via an operating oil adjustment unit that adjusts the flow of the operating oil.

3. In a die-casting method using the die-casting machine according to claim 1, the low-speed injection step, the high-speed injection step, and the pressure boosting step are provided. A die-casting method characterized in that the flow path adjustment unit adjusts the flow paths of the gas bottle for speed adjustment and the gas bottle for pressure adjustment based on the operating position of the plunger, and switches from the high-speed injection step to the pressure boosting step.

4. The die-casting method according to claim 3, wherein in the low-speed injection step and the high-speed injection step, pressurized gas is supplied from the gas bottle for speed adjustment to the accumulator to adjust the flow of the operating oil supplied from the accumulator to the injection cylinder.

5. The pressure increasing step is the die casting method according to claim 3, which supplies pressurized gas from the pressure regulating gas bottle to the accumulator to adjust the flow of hydraulic oil supplied from the accumulator to the injection cylinder.

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