Accumulator charge pressure setting method

Abstract

To provide a die cast machine and an accumulator charge pressure setting method which can operate an injection driving part based on the feed of a hydraulic fluid from an oil pressure feed part provided with an accumulator capable of the adjustment of charge pressure to secure an acceleration speed required upon injection-filling molten metal toward a mold cavity.SOLUTION: In a die cast machine for operating an injection driving part based on the feed of a hydraulic fluid from an oil pressure feed part to injection-mold molten metal from an injection part connected with the injection driving part toward a mold cavity formed by clamping a casting mold, the oil pressure feed part comprises: an accumulator for adjusting charge pressure; a charge pressure setting part for setting the charge pressure of the accumulator; and a compressible fluid charge part for charting a compressible fluid to the accumulator based on the setting of the charge pressure setting part.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a die-casting machine that operates an injection drive unit based on the supply of hydraulic oil from a hydraulic supply unit equipped with an accumulator capable of adjusting the charge pressure, closes a casting mold, and injects molten metal from an injection unit connected to the injection drive unit into a mold cavity formed thereby, and a method for setting the charge pressure of the accumulator.

Background Art

[0002] A die-casting machine that manufactures a casting by injecting and filling molten metal (referred to as molten metal) such as an aluminum alloy at high speed into a mold cavity formed by closing a casting mold includes a mold clamping unit that supports the casting mold, an injection unit that presses the molten metal supplied from a hot water supply means and injects and fills it into the mold cavity, and an injection drive unit that operates the injection and filling operation of the injection unit. This injection drive unit includes hydraulic drive means including an injection cylinder that is driven by receiving the supply of hydraulic oil from a hydraulic supply unit such as a hydraulic pump, electric drive means including conversion means that converts a rotational motion such as an electric motor into a linear motion, or hybrid drive means that combines hydraulic drive means and electric drive means, which are appropriately selected depending on applications, costs, etc.

[0003] Since the molten metal has a high thermal conductivity, when it is injected and filled into the mold cavity, it receives heat removal from the casting mold and cools and solidifies in a short time. Therefore, the time required for injection and filling into the mold cavity (referred to as injection time) is generally set to 1 second or less, and an injection drive unit capable of high-speed injection is required. In addition, by increasing the density of the molten metal injected and filled into the mold cavity and cooling and solidifying it, a stable supply of high-quality castings is made possible. Therefore, an injection drive unit with a high pressing force (referred to as filling force) of the molten metal is required. As an injection drive unit that satisfies both high-speed injection and high filling force, hydraulic drive means that is driven by receiving the supply of hydraulic oil from a hydraulic supply unit equipped with an accumulator is widely used.

[0004] An accumulator is a high-pressure container (also called an accumulator or ACC) that is divided into a gas chamber for sealing a high-pressure gas (called a compressible fluid), such as nitrogen, and a hydraulic chamber for accumulating hydraulic fluid. By utilizing the expansion force of the compressible fluid, the hydraulic fluid in the hydraulic chamber is instantaneously discharged toward the injection cylinder, enabling high-speed injection operation. Furthermore, by increasing the charge pressure of the compressible fluid in the gas chamber, high-pressure hydraulic fluid can be supplied from the hydraulic chamber to the injection drive unit, enabling a high filling force that can overcome the filling resistance of the molten metal flowing through the mold cavity. For this reason, the charge pressure of the compressible fluid in the accumulator is generally set to the maximum capacity of the equipment.

[0005] For example, if the charge pressure is 10 MPa, and the actual filling force required for casting is converted to a casting pressure of 5 MPa, the supply of hydraulic fluid from the accumulator is adjusted to limit the hydraulic fluid pressure to be equal to the casting pressure during casting. In other words, the 5 MPa difference between the charge pressure and the casting pressure is wasted. Because the compressible fluid charge into the gas chamber is carried out including this waste, the operating time and power consumption of the equipment required for charging increase, resulting in inefficient casting. Therefore, many methods have been proposed to set the charge pressure to match the actual casting pressure.

[0006] For example, as shown in Patent Document 1, a means for setting the charge pressure has been proposed which includes a speed accumulator capable of supplying hydraulic fluid to the injection cylinder and a pressure boosting accumulator that generates the driving force transmitted to the plunger, and the charge pressure of the speed accumulator is calculated to be the minimum pressure necessary to achieve the high injection speed set as a molding condition. According to this, by lowering the pressure of the speed accumulator, the surge pressure can be reduced, and casting defects such as casting burrs caused by the surge pressure can be reduced. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2017-136618 [Overview of the project] [Problems that the invention aims to solve]

[0008] Here, casting using a die-casting machine equipped with an accumulator will be explained using Figure 4. In Figure 4, the horizontal axis shows the injection position, and the vertical axis shows the injection speed and filling force. Molten metal is supplied to a cylindrical injection sleeve connected to the mold cavity, and the plunger tip is advanced to inject and fill the mold cavity with the molten metal in the injection sleeve. The injection filling pattern at that time is set in multiple stages, for example, with an injection speed VZ1 for a low-speed injection process that fills the injection sleeve with molten metal, and an injection speed VZ2 for a high-speed injection process that fills the mold cavity with molten metal. In addition, the filling force PZ1 for filling the mold cavity with molten metal and the filling force PZ2 for a pressure-boosting process that increases the density of the molten metal are shown by dashed lines, relative to the filling resistance of the molten metal flowing in the mold cavity during injection filling. The distance between injection positions SZ1 and SZ2 indicates the acceleration from injection speed VZ1 to VZ2. Since the molten metal filled into the mold cavity cools and solidifies in a short time, the injection speed VZ2 is set so that the injection time is less than 1 second, and an injection drive unit with a large acceleration is preferred in order to ensure the injection speed VZ2.

[0009] For example, when acceleration is low, the increase in injection speed is gradual, and as shown by the dashed line, the injection position SZ3 for pressure switching is reached at a low injection speed VZ3, ending the high-speed injection process and switching to the pressure-boosting process. As a result, the injection time becomes longer, the cooling and solidification of the molten metal progresses, the flow of molten metal in the mold cavity stops midway, and casting defects such as product shorts occur. In addition, the transmission of filling force to the molten metal decreases due to the cooling and solidification of the molten metal, and in the pressure-boosting process, as shown by the dashed line, the filling pressure becomes low PZ3, making it impossible to increase the molten metal density, leading to a significant decrease in casting quality. For this reason, it is important to set the injection drive unit to prioritize acceleration, and in setting the charge pressure of the accumulator, it is preferable to set the optimal charge pressure that can secure the required acceleration. In contrast, Patent Document 1 sets the charge pressure of the accumulator that can secure the injection speed of the high-speed injection process, and does not consider acceleration at all.

[0010] Therefore, the present invention aims to provide a method for setting the charge pressure of a die-casting machine and an accumulator, which can operate the injection drive unit based on the supply of hydraulic fluid from a hydraulic supply unit equipped with an accumulator with adjustable charge pressure, thereby ensuring the necessary acceleration when injecting and filling molten metal into a mold cavity. [Means for solving the problem]

[0011] The die-casting machine of the present invention is In a die-casting machine that operates an injection drive unit based on the supply of hydraulic fluid from a hydraulic supply unit and injects and fills molten metal from an injection unit connected to the injection drive unit into a mold cavity formed by clamping a casting mold, the hydraulic supply unit is characterized by comprising an accumulator whose charge pressure can be adjusted, a charge pressure setting unit for setting the charge pressure of the accumulator, and a compressible fluid charging unit for charging the accumulator with compressible fluid based on the setting of the charge pressure setting unit.

[0012] The method for setting the charge pressure of an accumulator according to the present invention is: A method for setting the charge pressure of an accumulator using the die-casting machine described in claim 1, characterized in that the compressible fluid is charged from the compressible fluid charging unit toward the accumulator based on the setting of the charge pressure setting unit.

[0013] In the method for setting the charge pressure of an accumulator according to the present invention, In a production casting process that involves operating the injection drive unit based on the supply of hydraulic fluid from the hydraulic supply unit, a low-speed injection process in which the injection drive unit is advanced at a low speed to fill the injection unit with molten metal, and a high-speed injection process in which the injection drive unit is advanced at a high speed to inject and fill the molten metal from the injection unit into the mold cavity, it is preferable that the high-speed injection process is performed by supplying the hydraulic fluid from the accumulator.

[0014] In the method for setting the charge pressure of an accumulator according to the present invention, It is preferable to calculate the charge pressure of the accumulator based on the acceleration of the switch from the preset low-speed injection process to the preset high-speed injection process, and set the calculation result as the optimal charge pressure in the charge pressure setting unit.

[0015] In the method for setting the charge pressure of an accumulator according to the present invention, Preferably, the system includes: a first setting step of setting a first machine line from the maximum charge pressure allowed by the accumulator and the maximum drowning speed of the injection drive unit using a pressure-velocity diagram created by the pressure axis and the velocity axis; a second setting step of setting a first die line from the drowning injection speed and drowning filling force during drowning performed before production casting; a third setting step of setting a second machine line that passes through the intersection of the first die line and the velocity line indicating the forward speed of the injection drive unit during the high-speed injection process during production casting, and setting the minimum charge pressure at the intersection of the second machine line and the pressure axis; a fourth setting step of setting a guaranteed charge pressure of the accumulator to guarantee the acceleration of the switching from the low-speed injection process to the high-speed injection process during production casting; and a fifth setting step of setting an optimal charge pressure by adding the guaranteed charge pressure to the minimum charge pressure.

[0016] Furthermore, in the method for setting the charge pressure of the accumulator of the present invention, It is preferable to operate the compressible fluid charging unit based on the optimal charging pressure to charge the compressible fluid into the accumulator.

[0017] Furthermore, in the method for setting the charge pressure of the accumulator of the present invention, Preferably, the injection drive unit operates the high-speed injection process by receiving the supply of hydraulic fluid from the accumulator, which has been charged to the optimal charge pressure. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a die-casting machine and a method for setting the charge pressure of an accumulator, which can ensure the necessary acceleration when injecting and filling molten metal toward a mold cavity by operating an injection driving unit based on the supply of hydraulic oil from a hydraulic supply unit having an accumulator capable of adjusting the charge pressure.

Brief Description of the Drawings

[0019] [Figure 1] It is a conceptual diagram showing a die-casting machine according to an embodiment of the present invention. [Figure 2] It is a diagram showing details of a charge pressure setting unit of the die-casting machine shown in FIG. 1. [Figure 3] It is a diagram showing the procedure of a method for setting the charge pressure of an accumulator according to an embodiment of the present invention. [Figure 4] It is a diagram for explaining casting forming using a die-casting machine.

Embodiments for Carrying Out the Invention

[0020] 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, the scales and dimensions of each component may be exaggerated or some components may be omitted.

[0021] (Die-casting machine) [[ID=​​​The casting mold 10 comprises a fixed mold 11 and a movable mold 12 supported by a clamping means (not shown). The fixed mold 11 and the movable mold 12 are clamped together to form a mold cavity 13 and a mold gate 14. Here, in order to stabilize the surface temperature of the mold cavity 13 and the temperature of the casting and shorten the casting cycle, it is preferable to provide the fixed mold 11 and the movable mold 12 with cooling means including a cooling circuit (not shown). Furthermore, in order to improve the release properties when pushing the casting out of the mold cavity 13 using an extrusion means (not shown) arranged in the fixed mold 11 or the movable mold 12, it is preferable to apply a release agent or the like to the mold cavity 13. Alternatively, the casting mold 10 may be provided with a vacuum suction means (not shown) to vacuum-suction the inside of the mold cavity 13 in synchronization with the casting process.

[0023] The injection unit 20 comprises a cylindrical injection sleeve 21 arranged horizontally, a pouring port 22 for supplying molten metal M such as aluminum alloy into the injection sleeve 21, a plunger tip 23 that slides in the front-rear direction within the injection sleeve 21, and a plunger rod 24 connecting the injection drive unit 30 and the plunger tip 23. Here, the injection sleeve 21 and the plunger tip 23 are provided with cooling means (not shown) through which a cooling medium flows, as needed. Furthermore, it is preferable to apply a lubricant to the sliding surfaces of the injection sleeve 21 and the plunger tip 23 to prevent wear damage to the plunger tip 23, stabilize the sliding state, and prevent adhesion of molten metal M residue. Alternatively, the injection sleeve 21 may be provided with a vacuum suction means (not shown) to suction the inside of the injection sleeve 21 in synchronization with the casting process.

[0024] The tip of the injection sleeve 21 is connected to the mold gate 14 of the casting mold 10, and the injection sleeve 21 and the mold cavity 13 are in communication via the mold gate 14. Here, with respect to the sliding of the plunger tip 23, the direction approaching the mold gate 14 is defined as forward F, sliding toward forward F is defined as forward movement, the direction away from the mold gate 14 is defined as backward R, and sliding toward backward R is defined as backward movement. Due to the forward movement of the plunger tip 23, the molten metal M supplied into the injection sleeve 21 passes through the mold gate 14 and fills the mold cavity 13.

[0025] The injection drive unit 30 includes a piston head 32 that slides in the front-rear direction, a piston rod 33 connected to the piston head 32, and an injection cylinder 31 that houses the piston head 32 and the piston rod 33. The piston rod 33 and the plunger rod 24 are connected at the connecting part 34, and the plunger tip 23, the piston rod 33, and the piston head 32 move forward and backward as a single unit. For example, hydraulic fluid is supplied to the head-side hydraulic chamber 35 of the injection cylinder 31, pushing the piston head 32 and piston rod 33 forward F to cause forward movement. Also, hydraulic fluid is supplied to the rod-side hydraulic chamber 36 of the injection cylinder 31, pushing the piston rod 33 and piston head 32 backward R to cause backward movement. This forward and backward movement is adjusted by adjusting the amount of hydraulic fluid supplied to the head-side hydraulic chamber 35 and the rod-side hydraulic chamber 36 (called meter-in control), or by adjusting the amount of fluid discharged (called meter-out control). For this purpose, it is preferable to provide adjustment valves (37, 38) for adjusting the supply or discharge of hydraulic fluid to the head-side hydraulic chamber 35 and the rod-side hydraulic chamber 36, respectively.

[0026] The hydraulic supply unit 40 includes a hydraulic pump 41 that supplies hydraulic fluid with adjusted pressure and flow rate to the injection drive unit 30, and a hydraulic control unit 42 that operates the hydraulic pump 41. It also includes an accumulator 43 that supplies hydraulic fluid to the injection drive unit 30 by discharging a large volume of hydraulic fluid from the hydraulic chamber using, for example, the expansion force of a compressible fluid such as nitrogen stored under high pressure in the gas chamber. The hydraulic pump 41 and the accumulator 43 are connected to the head-side hydraulic chamber 35 of the injection cylinder 31 via an adjustment valve 38. For this purpose, the adjustment valve 38 includes a switching means for switching the connection between the hydraulic pump 41 and the accumulator 43 and the head-side hydraulic chamber 35.

[0027] Here, with the hydraulic pump 41 and the head-side hydraulic chamber 35 connected via the adjustment valve 38, the hydraulic control unit 42 operates the hydraulic pump 41 to supply hydraulic fluid with adjusted pressure and flow rate from the hydraulic pump 41 to the head-side hydraulic chamber 35. This adjusts the forward movement of the plunger tip 23, enabling a low-speed injection process to fill the injection sleeve 21 with molten metal M, as shown in Figure 4. The hydraulic pump 41 is also connected to the rod-side hydraulic chamber 36 via the adjustment valve 37. When supplying hydraulic fluid from the hydraulic pump 41 to the head-side hydraulic chamber 35, the hydraulic fluid discharged from the rod-side hydraulic chamber 36 is returned to the hydraulic pump 41 via the adjustment valve 37. For this purpose, it is preferable that the hydraulic pump 41 be equipped with a storage means such as a hydraulic tank for storing hydraulic fluid. The hydraulic control unit 42 also operates the hydraulic pump 41 to supply hydraulic fluid with adjusted pressure and flow rate to the rod-side hydraulic chamber 36, thereby adjusting the retraction movement of the plunger tip 23. In this case, the hydraulic fluid discharged from the head-side hydraulic chamber 35 is returned to the hydraulic pump 41 via the adjustment valve 38.

[0028] Furthermore, with the accumulator 43 and the head-side hydraulic chamber 35 connected via the adjustment valve 38, the accumulator control unit 45 operates the hydraulic servo valve 46 to supply hydraulic fluid with adjusted pressure and flow rate from the accumulator 43 to the head-side hydraulic chamber 35. Since the amount of hydraulic fluid supplied from the accumulator 43 is large, it enables high-speed forward movement of the plunger tip 23, allowing for a high-speed injection process, for example, in which molten metal M is rapidly filled into the mold cavity 13, as shown in Figure 4. In addition, the hydraulic fluid discharged from the rod-side hydraulic chamber 36 is stored in the hydraulic pump 41 via the adjustment valve 37. Subsequently, at the appropriate timing for casting, hydraulic fluid is supplied from the hydraulic pump 41 to the accumulator 43 via the adjustment valve 38 and the hydraulic servo valve 46. Alternatively, hydraulic fluid may be supplied to the accumulator 43 using a hydraulic supply means (not shown).

[0029] Here, the hydraulic control unit 42 and the accumulator control unit 45 operate the hydraulic pump 41 and the hydraulic servo valve 46 based on the casting data set in the injection control unit 50. This casting data includes casting condition data and casting measurement data from trial casting and production casting, the equipment capacity of the injection drive unit 30 and the hydraulic supply unit 40, past casting performance data, and analysis data using analytical means such as flow analysis.

[0030] Furthermore, the accumulator 43 is connected to a compressible fluid charging unit 44 that stores a compressible fluid such as nitrogen adjusted to a predetermined pressure. The accumulator control unit 45 operates the compressible fluid charging unit 44 to replenish the compressible fluid consumed in the accumulator 43 during casting (this is called charging). The pressure of the compressible fluid being charged, or the pressure of the compressible fluid in the accumulator 43 after charging is complete, is called the charge pressure. For this purpose, it is preferable to provide a pressure measuring means for measuring the charge pressure in the compressible fluid charging unit 44 or the accumulator 43. The method for setting this charge pressure will be explained using Figures 2 and 3. Note that there is also a form of charging where hydraulic oil is replenished to the accumulator 43 consumed during casting, but here we will distinguish it from the replenishment of hydraulic oil to avoid confusion.

[0031] (Charge pressure setting unit 60) Next, the charge pressure setting unit 60, which sets the charge pressure during the charging of the accumulator 43, will be explained using Figure 2. First, as shown in Figure 2(a), the charge pressure setting unit 60 comprises a data transmission / reception unit 61, a data setting unit 62, a calculation unit 63, and a display unit 64. The charge pressure setting unit 60 is connected to the injection control unit 50, and is also connected to the hydraulic control unit 42 and the accumulator control unit 45 (simplified as the ACC control unit in Figure 2(a)) via the injection control unit 50.

[0032] The data transmission / reception unit 61 extracts the data necessary for setting the charge pressure from the casting molding data set in the injection control unit 50 and transfers the data to the data setting unit 62.

[0033] As shown in Figure 2(b), the data setting unit 62 sets the conditions for calculating the charge pressure based on the data transmitted from the data transmission / reception unit 61. Specifically, it includes a mode selection unit 621, a maximum charge pressure setting unit 622 for setting the maximum charge pressure of the accumulator 43, a maximum drowning speed setting unit 623 for setting the maximum injection speed (referred to as the maximum drowning speed) of the injection drive unit 30 during no-load operation when the maximum charge pressure is set, a drowning speed setting unit 624 for setting the drowning speed during drowning casting, an injection speed setting unit 625 for setting the injection speed of the high-speed injection process during production casting, an injection stroke setting unit 626 for setting the injection stroke, and an acceleration setting unit 627 for setting the acceleration for switching from the low-speed injection process to the high-speed injection process. When ON is selected in the mode selection unit 621, the calculation unit 63 starts calculating the charge pressure (referred to as the optimal charge pressure) that is suitable for production casting based on the settings in the data setting unit 62. When OFF is selected in the mode selection unit 621, the charge pressure of the accumulator 43 is set to the maximum charge pressure. Note that in Figure 2(b), the notation for the setting unit, etc., is omitted.

[0034] The calculation unit 63 calculates and sets the optimal charge pressure of the accumulator 43 based on the items set in the data setting unit 62. The display unit 64 displays the calculation results of the calculation unit 63, as shown in Figure 2(c). Specifically, it includes a sacrificial casting pressure display unit 641 that displays the sacrificial casting pressure measured during sacrificial casting, a minimum charge pressure display unit 642 that displays the minimum charge pressure required during production casting, a guaranteed charge pressure display unit 643 that displays the guaranteed charge pressure that guarantees the set acceleration, and an optimal charge pressure display unit 644 that displays the optimal charge pressure. Note that the notation of the display unit is omitted in Figure 2(c).

[0035] Furthermore, the data for the optimal charge pressure set by the calculation unit 63 is transmitted to the accumulator control unit 45 via the data transmission / reception unit 61 and the injection control unit 50. Based on the transmitted data, the accumulator control unit 45 operates the compressible fluid charging unit 44 to charge the accumulator 43 with a compressible fluid such as nitrogen, and sets the accumulator 43 to the optimal charge pressure. The injection drive unit 30 also receives hydraulic fluid from the accumulator 43, which is set to the optimal charge pressure, and performs the injection filling operation of the high-speed injection process.

[0036] This enables precise control of the injection speed pattern of the casting data set in the injection control unit 50, providing a die-casting machine 100 that can stably supply high-quality castings. Furthermore, by setting the optimal charge pressure, it is possible to shorten the charging time of the accumulator 43, reduce the size of the equipment involved in charging, and lower power consumption, thereby improving productivity. Additionally, the load on the die-casting machine 100, including the accumulator 43, can be reduced, leading to the expectation of preventive maintenance benefits for the equipment.

[0037] (How to set the charge pressure of the accumulator) Next, the method for setting the charge pressure of the accumulator 43 using the charge pressure setting unit 60 shown in Figure 2 will be explained with reference to Figure 3. The injection filling operation consists of a low-speed injection process in which molten metal M is filled into the injection sleeve 21 of the injection unit 20, and a high-speed injection process in which the injection drive unit 30 is moved forward at high speed to inject and fill the mold cavity 13. For this high-speed injection process, the supply of hydraulic fluid from the accumulator 43, which is charged with compressible fluid at the optimal charge pressure set by the charge pressure setting unit 60, is used.

[0038] Generally, in the consideration of appropriate casting conditions and casting equipment for casting molding, a PQ2 diagram is used to show the correlation between the equipment capacity of the die-casting machine 100 and the casting mold 10 and the casting conditions during production casting. In this case, the vertical axis represents the force generated on the surface of the plunger tip 23. The horizontal axis represents the squared value of the molten metal flow rate that the plunger tip 23 can move per unit time. Note that by multiplying both the horizontal and vertical axes by a coefficient, the vertical axis can be converted to the filling force or the charge pressure of the accumulator 43, and the horizontal axis can be converted to the molten metal flow velocity or the injection speed of the injection drive unit 30. Therefore, as shown in Figure 3, the calculation unit 63 uses a pressure-velocity diagram, which is a modified version of the PQ2 diagram with the charge pressure of the accumulator 43 as the vertical axis (referred to as the P axis or pressure axis) and the injection speed as the horizontal axis (referred to as the V axis or velocity axis). Alternatively, the display unit 64 may display this pressure-velocity diagram.

[0039] First, as shown in Figure 3(a), the maximum charge pressure P1 set in the maximum charge pressure setting unit 622 is set on the vertical axis, and the maximum drowning speed V1 set in the maximum drowning speed setting unit 623 is set on the horizontal axis. The line connecting the maximum charge pressure P1 and the maximum drowning speed V1 is set as the first machine line ML1 (first setting step). The area enclosed by this first machine line ML1 and the vertical and horizontal axes corresponds to the equipment capacity of the injection drive unit 30, and it is preferable to set the casting conditions within this area.

[0040] Next, based on the test casting speed V2 set in the test casting speed setting unit 624, test casting is performed using the casting mold 10, and the filling force measured during test casting is converted to the charge pressure of the accumulator 43 and set as the test casting pressure P2. The line passing through the intersection point PV1 of the test casting speed V2 and the test casting pressure P2 and the origin of the pressure velocity diagram is set as the first die line DL1 (second setting step). Since this first die line DL1 changes depending on, for example, the gate ratio of the casting mold 10, it is preferable to acquire casting molding data during trial casting and set the first die line DL1. It is also preferable to set the casting conditions along this first die line DL1.

[0041] Next, as shown in Figure 4, the first velocity line VL1 is set based on the injection speed VZ2 of the high-speed injection process set in the injection speed setting unit 625, and the intersection point PV2 of the first velocity line VL1 and the first die line DL1 is set. The first machine line ML1 is shifted in parallel toward the intersection point PV2, and the shifted line passing through the intersection point PV2 is set as the second machine line ML2. The intersection point of this second machine line ML2 and the velocity axis is set as the minimum drowning speed V3, and the intersection point of the second machine line ML2 and the pressure axis is set as the minimum charge pressure P3 (third setting step). By charging the accumulator 43 with compressible fluid at this minimum charge pressure P3, the injection speed VZ2 of the high-speed injection process is guaranteed. Furthermore, for example, in the trial run adjustment of the injection drive unit 30, the minimum drowning speed V3 can be used as a guideline for trial run adjustment. Although the first machine line ML1 is described as being moved in parallel to set up the second machine line ML2, the inclination angle of the second machine line ML2 may be corrected considering the efficiency of the injection drive unit 30's equipment capacity, etc.

[0042] Next, the charge pressure (guaranteed charge pressure P4) of the accumulator 43 that guarantees the acceleration set in the acceleration setting unit 627 is calculated. Here, the acceleration is calculated using (Equation 1) shown below, and the pressure is calculated using (Equation 2) shown below. Using (Equation 1) and (Equation 2), the acceleration can be set by pressure. The acceleration set in the acceleration setting unit 627 guarantees that the injection speed VZ2 will be reliably achieved when switching from the low-speed injection process to the high-speed injection process, as shown in Figure 4.

[0043] F=m×α(Formula 1) F (load) m (mass) α (acceleration) F=P×S (formula 2) F (load) P (pressure) S (area)

[0044] Here, in equations 1 and 2, F (load) is the thrust force that the injection drive unit 30 can generate, or the force (filling force) that the plunger tip 23 presses against the molten metal M. Also, in equation 1, m (mass) is the weight of the injection drive unit 30 components that slide in the front-rear direction, such as the plunger tip 23 and the plunger rod 24. Also, in equation 2, P (pressure) is the pressure of the hydraulic fluid supplied from the accumulator 43 to the head-side hydraulic chamber 35, and S (area) is the pressure-receiving area of ​​the piston head 32 or the cross-sectional area of ​​the plunger tip 23 that presses against the molten metal M. Note that the pressure of the hydraulic fluid supplied from the accumulator 43 to the head-side hydraulic chamber 35 can be converted into the charge pressure of the compressible fluid in the accumulator 43. In other words, P (pressure) is the charge pressure of the accumulator 43. These items relate to the equipment capacity of the die-casting machine 100, are set in the injection control unit 50, and the data is transferred to the charge pressure setting unit 60 as casting molding data.

[0045] Using these relationships, as shown in Figure 3(a), the guaranteed charge pressure P4 is calculated and set from the acceleration set in the acceleration setting unit 627 (fourth setting step). The guaranteed charge pressure P4 is set in anticipation of the amount of charge pressure consumed by the accumulator 43 due to casting. In addition, the second die line DL2 is set by adding the guaranteed charge pressure P4 to the first die line DL1 and shifting it in parallel. Although the second die line DL2 is set by shifting the first die line DL1 in parallel, the inclination angle of the second die line DL2 may be corrected considering the efficiency of the equipment capacity of the casting mold 10, etc.

[0046] Finally, the minimum charge pressure P3 is added to the guaranteed charge pressure P4 to set the optimal charge pressure P5 (5th setting step). Also, the intersection point PV3 of the second die line DL2 and the first velocity line VL1 is determined, and the intersection point of the velocity axis on the extension line connecting the optimal charge pressure P5 and intersection point PV3 is set as the optimal drowning speed V4. The line connecting this optimal drowning speed V4 and the optimal charge pressure P5 is set as the third machine line ML3. This third machine line ML3 represents the state at the start of casting, and casting is repeatedly performed within the area enclosed by the third machine line ML3 and the second machine line ML2.

[0047] This enables precise control of the injection speed pattern of the casting data set in the injection control unit 50, as shown in Figure 4, and provides a method for setting the optimal charge pressure P5 of the accumulator 43, which enables the stable supply of high-quality castings. As a result, it is possible to achieve productivity improvements through a reduction in the charging time of the accumulator 43, miniaturization of the equipment involved in charging, and reduction in power consumption. In addition, the load on the die-casting machine 100, including the accumulator 43, can be reduced, and a preventive maintenance effect on the equipment can be expected.

[0048] Next, another embodiment of the method for setting the optimal charge pressure P5 of the accumulator 43 will be described using Figure 3(b). Figure 3(b) also includes a first setting step to a fifth setting step. Note that the first to third setting steps are the same as in Figure 3(a), so their explanation will be omitted, and the fourth and fifth setting steps will be described.

[0049] First, in the fourth setting step of the other embodiment (referred to as the fourth H setting step for convenience), the guaranteed injection velocity V5 is calculated from the acceleration set by the acceleration setting unit 627 using the following equation (Equation 3). Next, as shown in Figure 4, a second velocity line VL2 is set with the guaranteed injection velocity V5 as the starting point. α = dv / dt (Equation 3) α (acceleration) dv (velocity displacement) dt (time displacement)

[0050] Next, in the fifth setting step of the other embodiment (for convenience, referred to as the fifth H setting step), the intersection point PV4 of the first die line DL1 and the second velocity line VL2 is determined, and a line parallel to the first machine line ML1 or the second machine line ML2 that passes through this intersection point PV4 is set as the fourth machine line ML4. Note that the fourth machine line ML4 and the third machine line ML3 are ultimately the same. Therefore, the intersection point of this fourth machine line ML4 and the pressure axis may be set as the optimal charge pressure P5. Alternatively, the intersection point of the fourth machine line ML4 and the velocity axis may be set as the optimal dry-firing speed V4. In this way, the required acceleration may be converted to the guaranteed injection speed V5, and the optimal charge pressure P5 of the accumulator 43 may be set.

[0051] Although preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the embodiments described above. Various modifications or improvements can be made to the above embodiments. [Explanation of symbols]

[0052] 100 die-casting machines 10 Casting molds 11 Fixed mold 12. Movable molds 13 Mold Cavity 14 Mold Gate 20 Injection part 21 Injection Sleeve 22 pouring spouts 23 Plunger Tip 24 Plunger Rods 30 Injection drive unit 31 Injection Cylinder 32 Piston Heads 33 Piston Rod 34 Connecting part 35 Head-side hydraulic chamber 36 Rod-side hydraulic chamber 37, 38 Adjustment valve 40 Hydraulic supply unit 41 Hydraulic pump 42 Hydraulic Control Unit 43 Accumulator 44 Compressible fluid charging section 45. Accumulator Control Unit (ACC Control Unit) 46 Hydraulic servo valve 50 Injection control unit 60 Charge pressure setting section 61 Data transmission / reception unit 62 Data Setting Section 621 Mode Selection Section 622 Maximum charge pressure setting section 623 Maximum dry-firing speed setting section 624 Discarded shot speed setting section 625 Injection speed setting section 626 Injection stroke setting section 627 Acceleration setting unit 63 Arithmetic section 64 Display section 641 Discarded firing pressure indicator 642 Minimum charge pressure display section 643 Guaranteed Charge Voltage Indicator 644 Optimal Charge Pressure Display Section M molten metal P1 Maximum Charge Pressure P2 Discard pressure P3 Minimum charge pressure P4 Guaranteed Charge Voltage P5 Optimal Charge Pressure V1 Maximum dry-firing speed V2 Discarded shot speed V3 Minimum dry firing speed V4 Optimal dry-firing speed V5 Guaranteed Injection Speed ML1 Machine Line 1 ML2 2nd Machine Line ML3 3rd Machine Line ML4 4th Machine Line DL1 First Dire Line DL2 Second Dire Line PV1~PV4 intersection VL1 1st speed line VL2 2nd speed line VZ1~VZ3 Injection speed PZ1~PZ3 Filling Force SZ1~SZ3 firing positions

Claims

1. In a method for setting the charge pressure of an accumulator using a die-casting machine that operates an injection drive unit based on the supply of hydraulic fluid from a hydraulic supply unit and injects and fills molten metal from an injection unit connected to the injection drive unit into a mold cavity formed by clamping a casting mold, The hydraulic supply unit comprises an accumulator whose charge pressure can be adjusted, a charge pressure setting unit for setting the charge pressure of the accumulator, and a compressible fluid charging unit for charging the accumulator with compressible fluid based on the setting of the charge pressure setting unit. Based on the setting of the charge pressure setting unit, the compressible fluid is charged from the compressible fluid charging unit toward the accumulator. In a production casting process that involves operating the injection drive unit based on the supply of hydraulic fluid from the hydraulic supply unit, performing a low-speed injection process in which the injection drive unit is advanced at a low speed to fill the injection unit with molten metal, and a high-speed injection process in which the injection drive unit is advanced at a high speed to inject and fill the molten metal from the injection unit into the mold cavity, the high-speed injection process involves supplying the hydraulic fluid from the accumulator, The charge pressure of the accumulator is calculated based on the acceleration of the switch from the preset low-speed injection process to the preset high-speed injection process, and the calculation result is set as the optimal charge pressure in the charge pressure setting unit. Calculating the charge pressure of the accumulator based on the acceleration and setting the calculation result as the optimal charge pressure in the charge pressure setting unit is: A first setting step involves setting a first machine line based on the maximum charge pressure allowed by the accumulator and the maximum dry-firing speed of the injection drive unit, using a pressure-velocity diagram created with a pressure axis and a velocity axis. A second setting step involves setting the first die line based on the injection speed and filling force of a test casting performed before the aforementioned production casting. A third setting step involves setting a second machine line that passes through the intersection of the first die line and the speed line indicating the forward speed of the injection drive unit in the high-speed injection process during the aforementioned production casting, and setting the minimum charge pressure at the intersection of the second machine line and the pressure axis. A fourth setting step involves setting the guaranteed charge pressure of the accumulator to guarantee the acceleration during the aforementioned production casting, The system includes a fifth setting step of setting the optimal charge pressure by adding the guaranteed charge pressure to the minimum charge pressure, In the fourth setting step described above, F, m, α, S, and P are set as follows: F: The thrust force that the injection drive unit can generate, m: Mass of the movable part of the injection drive unit, α: The acceleration, S: The pressure-receiving area of ​​the piston head of the injection drive unit, which is pressed by the hydraulic fluid from the accumulator, P: Pressure of the hydraulic fluid supplied from the accumulator to the injection drive unit, A method for setting the charge pressure of an accumulator, characterized in that the guaranteed charge pressure is calculated using equation 1: F = m × α and equation 2: F = P × S.

2. A method for setting the charge pressure of an accumulator according to claim 1, comprising operating the compressible fluid charging unit based on the optimal charge pressure to charge the compressible fluid into the accumulator.

3. The method for setting the charge pressure of an accumulator according to claim 2, wherein the injection drive unit operates the high-speed injection process by receiving the supply of the hydraulic fluid from the accumulator which has been charged to the optimal charge pressure.

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