Die casting apparatus

Abstract

To suppress deterioration in the quality of a cast caused by the inflow of a part of a molten metal into a cavity.SOLUTION: A die casting device comprises: a mold having an introduction port introduced with a molten metal and forming a cavity; a sleeve connected to the introduction port; a plunger arranged so as to be advanceable and retreatable at the inside of the sleeve and emitting, into the cavity, the molten metal fed into the sleeve by advance; a decompression apparatus decompressing the inside of the cavity; a detection sensor detecting the arrival of the molten metal; and a control part controlling the advance / retreat of the plunger. When an arrival time from the advance start point of the plunger to a detection point in which the arrival of the molten metal is detected by the detection sensor is shorter than a predetermined standard advance time, the control part executes a speed control step of controlling at least either a changeover position of an advance speed of the plunger or the magnitude of the advance speed so that an advance time from a position of the plunger at the detection point to the most advanced position of the plunger is made shorter than the predetermined standard advance time.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a die-casting apparatus.

Background Art

[0002] Conventionally, there has been a die-casting method of injecting molten metal into a depressurized cavity (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As the pressure in the cavity decreases, a part of the molten metal near the cavity in the sleeve may flow into the cavity first. In this case, since the solidification times of a part of the molten metal that has flowed into the cavity first and the molten metal that flows in later are different, the quality of the cast product may deteriorate.

Means for Solving the Problems

[0005] The present disclosure can be realized in the following forms. According to one aspect of the present disclosure, a die-casting apparatus is provided. The die-casting apparatus includes a mold that forms a cavity and has an inlet for introducing molten metal, a sleeve communicating with the inlet, a plunger disposed to be movable forward and backward within the sleeve and ejecting the molten metal supplied into the sleeve into the cavity by moving forward, a decompression device for decompressing the cavity, a detection sensor for detecting the arrival of the molten metal flowing from the sleeve toward the cavity, and a control unit for controlling the forward and backward movement of the plunger. When the arrival time from the start time of the forward movement of the plunger to the detection time when the detection sensor detects the arrival of the molten metal is shorter than a predetermined reference time, the control unit performs a speed control step of controlling at least one of the switching position of the forward movement speed of the plunger and the magnitude of the forward movement speed so that the forward movement time from the position of the plunger at the detection time to the most forward position of the plunger when the supply of the molten metal to the cavity is completed is shorter than a predetermined reference forward movement time. After the molten metal is supplied to the sleeve, a first step of setting the forward movement speed to a first speed and moving the plunger from a first position, which is the position at the start time of the forward movement, to the switching position is performed, and after the first step, the forward movement speed is switched to a second speed greater than the first speed, and a second step of moving the plunger to a second position, which is a predetermined position on the backward side of the most forward position, is performed. When the arrival time is shorter than the reference time, the switching position is set to a reference switching position, which is the switching position at which the forward movement time becomes the reference forward movement time when the second speed is set to a predetermined reference second speed and the plunger is moved forward, and the speed control step is performed by changing the second speed to a speed greater than the reference second speed.

[0006] (1) According to one embodiment of the present disclosure, a die-casting apparatus is provided. This die-casting apparatus has an inlet for introducing molten metal, a mold that forms a cavity, a sleeve communicating with the inlet, a plunger disposed to be movable forward and backward within the sleeve and ejecting the molten metal supplied into the sleeve into the cavity by moving forward, a decompression device for decompressing the cavity, a detection sensor for detecting the arrival of the molten metal flowing from the sleeve toward the cavity, and a control unit for controlling the forward and backward movement of the plunger. The control unit executes a speed control step of controlling at least one of the switching position of the forward speed of the plunger and the magnitude of the forward speed such that, when the arrival time from the start time of the forward movement of the plunger to the detection time when the detection sensor detects the arrival of the molten metal is shorter than a predetermined reference time, the forward movement time from the position of the plunger at the detection time to the most forward position of the plunger when the supply of the molten metal to the cavity is completed is shorter than a predetermined reference forward movement time. According to this embodiment, by shortening the forward movement time of the plunger, the subsequent molten metal can be made to flow into the cavity earlier, and the difference in the solidification times with the previously flowed-in molten metal can be reduced. When the arrival of the molten metal is detected by the detection sensor before the elapse of the reference time, it means that a part of the molten metal has flowed into the cavity earlier. In this case, by moving the plunger forward quickly to make the remaining molten metal flow into the cavity earlier, the difference in the solidification times of the previously flowed-in molten metal and the subsequently flowed-in molten metal can be reduced. Therefore, deterioration in the quality of the cast product can be suppressed. (2) In the die-casting apparatus of the above-described embodiment, after the molten metal is supplied to the sleeve, the control unit sets the forward speed to a first speed and moves the plunger from a first position, which is the position at the start of forward movement, to the switching position in a first step; and after the first step, the control unit switches the forward speed to a second speed greater than the first speed and moves the plunger to a second position, which is a predetermined position on the retracted side from the most forward position, in a second step. When the arrival time is shorter than the reference time, the speed control step may be executed by changing the switching position to a position between the reference switching position, which is the switching position when the forward movement time is the reference forward movement time, and the first position. According to this embodiment, by changing the switching position between the reference switching position and the first position, the distance traveled at the second speed greater than the first speed can be increased, and the forward movement time can be made shorter than the reference forward movement time. Therefore, the remaining molten metal can be caused to flow into the cavity more quickly. (3) In the die-casting apparatus of the above-described embodiment, when the arrival time is shorter than the reference time, the control unit may move the switching position closer to the first position as the arrival time is shorter. According to this embodiment, the switching position can be finely adjusted according to the timing detected by the detection sensor. (4) In the die-casting apparatus of the above-described embodiment, the speed control step may include controlling the forward speed so that the forward movement time becomes longer than the reference forward movement time when the arrival time is longer than the reference time. According to this embodiment, by increasing the forward movement time, the generation of turbulent flow in the molten metal can be suppressed, and a decrease in the quality of the cast product can be suppressed. The case where the arrival time is longer than the reference time is a case where the molten metal has not yet reached the vicinity of the inlet. In this case, the generation of turbulent flow can be suppressed by delaying the timing at which the plunger reaches the second position. (5) In the die-casting apparatus of the above-described embodiment, when the arrival time is longer than the reference time, the speed control step may be executed by changing the switching position to a position between the reference switching position and the second position. According to this embodiment, by changing the switching position between the reference switching position and the second position, the distance traveled at the first speed, which is smaller than the second speed, can be increased, and the forward movement time can be lengthened. Therefore, the generation of turbulent flow can be suppressed. (6) In the die-casting apparatus of the above-described embodiment, when the arrival time is longer than the reference time, the switching position may be closer to the second position as the arrival time is longer. According to this embodiment, the switching position can be finely adjusted according to the timing detected by the detection sensor. (7) In the die-casting apparatus of the above-described embodiment, the control unit includes a supply step of supplying the molten metal to the sleeve, and after the supply step, a forward movement step of moving the plunger from the first position to the second position by the first step and the second step, and after the forward movement step, a backward movement step of moving the plunger back to the first position. The injection process is repeatedly performed. When the switching position is changed in the second step of the nth (n is a positive integer) injection process, the reference switching position may be changed to the changed switching position before the start of the (n + 1)th injection process. According to this embodiment, the inflow of a part of the molten metal into the cavity in the subsequent injection process can be suppressed. The case where the arrival of the molten metal is detected by the detection sensor before the reference time in the nth injection process means that a part of the molten metal has flowed into the cavity in advance. In this case, it is considered that the leading position of the molten metal is closer to the inlet than the target position, and there is a high possibility that a part of the molten metal will flow into the cavity in the subsequent injection process as well. Therefore, by changing the reference switching position to a position between the reference switching position and the first position, the inflow of a part of the molten metal into the cavity in the subsequent casting process can be suppressed. The present disclosure can also be realized in various forms other than the die-casting apparatus. For example, it can be realized in the form of a die-casting method or the like.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0008] A. First Embodiment: FIG. 1 is a schematic diagram showing a cross section of a die-casting apparatus 1. The die-casting apparatus 1 includes a mold 10, a sleeve 20, a plunger 30, a decompression device 40, and a control unit 80. The die-casting apparatus 1 is an apparatus for manufacturing a cast product by pouring molten metal into a cavity 13 decompressed by a decompression device 40, that is, by a method called the vacuum die-casting method or the decompression die-casting method. The mold 10 has a fixed mold 11 and a movable mold 12. A cavity 13 is formed between the fixed mold 11 and the movable mold 12. The fixed mold 11 has an inlet 14 for introducing molten metal into the cavity 13. The sleeve 20 communicates with the inlet 14 through a liner 16 which is a molten-metal flow path formed in the fixed mold 11. The sleeve 20 is provided with a pouring port 21 into which molten metal is poured. The plunger 30 is disposed in the sleeve 20 so as to be able to advance and retreat, and by advancing, the molten metal supplied into the sleeve 20 is ejected into the cavity 13. Specifically, the plunger 30 is connected to a hydraulic device (not shown) via a rod 31 connected to the rear end. Then, by the driving force of the hydraulic device, the plunger 30 advances or retreats. In FIG. 1, the advancing direction in which the plunger 30 approaches the mold 10 and the retreating direction which is the reverse direction are shown. The mold 10 is formed with a flow path 15 for decompressing the cavity 13. The flow path 15 is connected to the decompression device 40. The decompression device 40 is realized by a vacuum pump or the like. A decompression valve 41 is attached to the flow path 15. When the inside of the cavity 13 is decompressed, the decompression valve 41 is opened, and the air inside the cavity 13 is discharged by the decompression device 40.

[0009] The control unit 80 is configured as a computer including a CPU, a memory, and the like. The memory stores an execution program for injection processing and the like, which will be described later. The control unit 80 controls the pressure reducing device 40, the hydraulic device, and the like. Specifically, the control unit 80 controls the forward and backward movement of the plunger 30. In the present embodiment, the reference switching position WP, which will be described later, means a reference position when switching the forward speed of the plunger 30, and is preset as the tip position of the plunger 30. Here, the first position SP is a position in the backward direction from the pouring port 21. The second position EP is a position in the forward direction from the first position SP and is closer to the inlet 14 than the first position SP.

[0010] Furthermore, the die casting apparatus 1 includes a detection sensor 51 and a stroke sensor 52. The detection sensor 51 detects the arrival of the molten metal flowing from the plunger 30 toward the cavity 13. In the present embodiment, the detection sensor 51 is disposed near the inlet 14. When the molten metal reaches the detection sensor 51, the detection sensor 51 outputs an arrival detection signal to the control unit 80. That is, when the molten metal reaches the detection sensor 51, it is detected that the molten metal has reached the inlet 14. The detection sensor 51 includes two conductors. A voltage is applied between the two conductors. The two conductors are attached with their respective tips exposed from the liner 16 in a state where the respective tips are separated. When the molten metal has not reached the detection sensor 51, that is, when there is no molten metal at the tips of the two conductors, no current flows between the two conductors. On the other hand, when the molten metal reaches the detection sensor 51, that is, when there is molten metal at the tips of the two conductors, a current flows between the two conductors through the molten metal which is a conductor. Therefore, when a current flows between the two built-in conductors of the detection sensor 51, the detection sensor 51 outputs an arrival detection signal to the control unit 80. The stroke sensor 52 is attached to the plunger 30 and is a displacement sensor that detects the distance from the reference position of the plunger 30. In the present embodiment, the reference position coincides with the first position SP.

[0011] FIG. 2 is a diagram showing the relationship between time and the forward speed and position of the plunger 30. The upper part of FIG. 2 shows the relationship between time and the position of the plunger 30. The lower part of FIG. 2 shows the relationship between time and the forward speed of the plunger 30. In this embodiment, as shown by the solid line in FIG. 2, after the molten metal is poured into the sleeve 20, the plunger 30 first advances at a first speed V1, which is a low speed, and then advances at a second speed V2, which is a high speed. Specifically, the plunger 30 starts to advance at the first speed V1 from the first position SP, which is the position at the start of advancement shown in FIG. 1. The first speed V1 is a speed slow enough that turbulence is not generated in the molten metal in the sleeve 20. This makes it possible to reduce the occurrence of porosity due to air being entrained in the molten metal by the generation of turbulence. Thereafter, the cavity 13 is depressurized. This makes it possible to reduce the occurrence of porosity due to the entrainment of air in the cavity 13 and gas caused by the mold release agent. The plunger 30 advances at the first speed to the reference switching position WP. In this embodiment, the reference switching position WP is a position where the molten metal reaches the inlet 14. Thereafter, the plunger 30 is advanced to the second position EP at a second speed V2 higher than the first speed V1. This allows the filling of the molten metal into the cavity 13 to be completed in a short time, and the variation in the solidification time can be reduced. The second position EP is a predetermined position on the retreat side of the most forward position FP of the plunger 30 when the supply of the molten metal to the cavity 13 is completed. The most forward position FP is the position of the plunger 30 when the pressure in the cavity 13 becomes the target pressure. When the plunger 30 approaches the most forward position FP, it is decelerated by the pressure of the molten metal filled in the cavity 13. The second position EP is the position at the time when the plunger 30 starts to decelerate. In the following description, the case where the forward speed is switched from the first speed V1 to the second speed V2 at the reference switching position WP may be called the reference state.

[0012] FIG. 3 is a diagram for explaining the case where a part of the molten metal flows into the cavity 13. As shown in FIG. 3, when the cavity 13 is depressurized by the depressurizing device 40, a part of the molten metal close to the cavity 13 may separate from many other molten metals (main flow MM described later) and flow into the cavity 13. This is because the molten metal may fluctuate, and the closer it is to the pressure reducing valve 41, the more easily it is affected by the depressurization. Here, a part of the molten metal flowing into the cavity 13 is referred to as the front molten metal TM, and the other molten metal is referred to as the main flow MM. When the front molten metal TM occurs, since the main flow MM flows into the cavity 13 behind the front molten metal TM, the front molten metal TM solidifies before the main flow MM. If the solidification times are different, an interface may occur and the strength of the casting may decrease. Therefore, in the present embodiment, the following injection process is executed. In the injection process, it is predicted whether the front molten metal TM is occurring by using the detection sensor 51. And when it is predicted that the front molten metal TM is occurring, the switching position where the forward speed is switched to the second speed V2 is changed. Thereby, the difference in the solidification times between the front molten metal TM and the main flow MM can be reduced. Therefore, a decrease in the quality of the casting can be suppressed.

[0013] FIG. 4 is a flowchart of the injection process. The injection process is executed in the casting process. As shown in FIG. 4, the control unit 80 brings the fixed mold 11 and the movable mold 12 into close contact with each other, controls a ladle (not shown), and pours molten metal into the sleeve 20 through the pouring gate 21 (supply step S10). The control unit 80 sets the forward speed of the plunger 30 to the first speed V1 and advances the plunger 30 (step S12). After the plunger 30 has advanced to a position where it closes the pouring gate 21, the control unit 80 opens the pressure reducing valve 41 to reduce the pressure inside the cavity 13 (step S14). The control unit 80 determines whether the detection sensor 51 has detected the arrival of the molten metal (step S16). If it is determined that the detection sensor 51 has not detected the arrival of the molten metal (step S16: NO), the control unit 80 determines whether the reference time has elapsed since the start of the forward movement of the plunger 30 (step S18). In the present embodiment, the reference time is set to the time from when the plunger 30 starts to advance until it reaches the reference switching position WP. If it is determined that the reference time has not elapsed (step S18: NO), steps S16 or steps S16 and S18 are repeatedly executed at predetermined time intervals until the detection sensor 51 detects or until the reference time elapses. The predetermined time interval is, for example, several ms.

[0014] When it is determined that the reference time has elapsed (step S18: YES), since it is predicted that the flash TM has not occurred, the control unit 80 switches the forward speed of the plunger 30 to the second speed V2 at the reference switching position WP as the switching position, and continues to move the plunger 30 forward (step S20). As a result, the molten metal rapidly fills the cavity 13. As the cavity 13 is filled with the molten metal, the plunger 30 decelerates. Note that the switching position is a position where the forward speed is switched from the first speed V1 to the second speed V2. After moving the plunger 30 to the furthest forward position FP where the pressure in the cavity 13 becomes the target pressure, the control unit 80 stops the plunger 30 at the furthest forward position FP (step S50). The molten metal solidifies in the cavity 13. The control unit 80 separates the movable mold 12 from the fixed mold 11, projects an ejector pin (not shown), and takes out the casting from the mold 10 (step S52). The control unit 80 retracts the plunger 30 to the first position SP (retraction step S54), and ends this processing routine.

[0015] The injection process includes a first step and a second step. The first step is a step of moving the plunger 30 to the switching position after the molten metal is supplied to the sleeve 20 in the supply step S10, the forward speed is set to the first speed V1 in step S12, and until the forward speed is switched to the second speed V2 in step S20. The second step is a step of moving the plunger 30 from the step S20 after the forward speed is switched to the second speed V2 greater than the first speed V1 to the second position EP. The first step and the second step are also called forward steps.

[0016] When it is determined that the detection sensor 51 has detected the arrival of the molten metal (step S16: YES), since it is predicted that the pre-molten metal TM is generated, the control unit 80 changes the switching position to a changed switching position WPa (FIG. 2), which is a position between the reference switching position WP and the first position SP (step S22). Step S22 is also called a speed control step. In the present embodiment, the changed switching position WPa is a predetermined position. Note that the case where it is determined that the detection sensor 51 has detected the arrival of the molten metal means that the arrival time from the start of forward movement to the detection time when the detection sensor 51 detects the arrival of the molten metal is shorter than the reference time. The control unit 80 switches the forward speed of the plunger 30 to the second speed V2 at the changed switching position WPa as the switching position, and continues to move the plunger 30 forward (step S24). Thereby, the molten metal can be ejected into the cavity 13 faster than in the reference state. Therefore, the difference in solidification times between the pre-molten metal TM and the main flow MM can be reduced, and deterioration of the quality of the cast product can be suppressed. Note that after the execution of step S24, the control unit 80 proceeds to step S50.

[0017] Regarding steps S22 and S24, an explanation will be given with reference to FIG. 2. The dashed-dotted line shown in FIG. 2 indicates the relationship between time, forward speed, and position when the control unit 80 determines that the detection sensor 51 has detected the arrival of the molten metal (step S16: YES), that is, when it is predicted that the leading molten metal TM is generated. When it is predicted that the leading molten metal TM is generated, the forward speed is switched from the first speed V1 to the second speed V2 at a time ta1 before the time t1 when the forward speed is switched to the second speed V2 at the reference switching position WP. Therefore, at a time ta2 before the time t2 when the plunger 30 reaches the second position EP in the reference state, the plunger 30 reaches the second position EP. That is, the forward time required for the plunger 30 to advance from the first position SP to the second position EP when the forward speed is switched to the second speed V2 at the changeover switching position WPa is shorter than the reference forward time TAt, which is the forward time in the reference state. And the forward time required for the plunger 30 to advance from the first position SP to the most forward position FP is shorter than the forward time in the reference state. As a result, the molten metal is ejected into the cavity 13 earlier than in the reference state. Therefore, the difference in the solidification times between the leading molten metal TM and the main flow MM can be reduced.

[0018] According to the first embodiment described above, when the arrival time from the start of the forward movement of the plunger 30 until the detection sensor 51 detects the arrival of the molten metal is shorter than the reference time, the control unit 80 controls the forward speed in step S24 so that the forward time from the first position SP to the second position EP is shorter than the reference forward time TAt. Specifically, the control unit 80 changes the switching position to the changeover switching position WPa, which is a position between the reference switching position WP and the first position SP, in step S22. Then, in step S24, the control unit 80 switches the forward speed to the second speed V2 at the changeover switching position WPa. Therefore, when it is predicted that the leading molten metal TM is generated, by shortening the forward time of the plunger 30, the main flow MM can be made to flow into the cavity earlier, and the difference in the solidification times between the leading molten metal TM and the main flow MM can be reduced. Therefore, deterioration in the quality of the cast product can be suppressed.

[0019] B. Second Embodiment: FIG. 5 is a flowchart of the continuous injection process according to the second embodiment. FIG. 6 is a diagram for explaining a method of determining the switching position. In the second embodiment, the method of determining the switching position is different from that of the first embodiment. The same processing steps as those in the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof are omitted as appropriate. In the continuous injection process according to the present embodiment, the injection process is repeatedly executed.

[0020] As shown in FIG. 5, the control unit 80 executes steps S10 to S16 in the same manner as in the first embodiment. When the control unit 80 determines that the detection sensor 51 has not detected the arrival of the molten metal (step S16: NO), the control unit 80 executes step S16 at a predetermined time interval until it determines that the detection sensor 51 has detected the arrival of the molten metal. The predetermined time interval is, for example, several milliseconds. When the control unit 80 determines that the detection sensor 51 has detected the arrival of the molten metal (S16: YES), the control unit 80 determines the switching position (step S40).

[0021] In step S40, the control unit 80 determines the switching position using the relationship between the arrival time and the switching position shown in FIG. 6. The relationship between the arrival time and the switching position is determined in advance by experiments or the like and is stored in the memory of the control unit 80. The relationship between the arrival time and the switching position may be defined by a mathematical formula or may be defined by a map associating the arrival time and the switching time. The horizontal axis in FIG. 6 is the arrival time [s], and the vertical axis is the switching position [mm]. The switching position is a position with the forward direction as the positive direction with reference to the first position SP.

[0022] When the arrival time is the reference time TRt, the switching position is set to the reference switching position WP. In the present embodiment, as in the first embodiment, the reference switching position WP is set to the position of the plunger 30 when the molten metal reaches the inlet 14 in the reference case where the front molten metal TM has not occurred. That is, the reference time TRt is the arrival time from the start of forward movement to when the detection sensor 51 detects the arrival of the molten metal in the reference case.

[0023] The relationship between the arrival time and the switching position is such that when the arrival time is shorter than the reference time TRt, the earlier the arrival of the molten metal at the detection sensor 51 is detected, that is, the shorter the arrival time, the switching position is set to approach the first position SP. And when the arrival time is longer than the reference time TRt, the later the arrival of the molten metal at the detection sensor 51 is detected, that is, the longer the arrival time, the switching position is set to approach the second position EP.

[0024] As described above, when the arrival time is shorter than the reference time TRt, it is a case where it is predicted that the pre-melt TM is generated. In this case, by bringing the switching position closer to the first position SP, the forward movement time of the plunger 30 can be shortened, the main flow MM can be made to flow into the cavity earlier, and the difference in the solidification times of the pre-melt TM and the main flow MM can be reduced. On the other hand, when the arrival time is longer than the reference time TRt, it is a case where the arrival at the molten metal inlet 14 is delayed. In this case, if the switching to the second speed V2 is made early, turbulent flow is likely to occur. Therefore, by bringing the switching position closer to the second position EP and switching to the second speed at a time when the molten metal reaches the inlet 14, the generation of turbulent flow can be suppressed. In either case, by using the relationship between the arrival time and the switching position, the switching position can be finely adjusted. For example, when the switching position is brought closer to the first position SP than the reference switching position WP, while the main flow MM can be made to flow into the cavity 13 earlier, it is also conceivable that turbulent flow is likely to occur. Therefore, by defining the relationship between the arrival time and the switching position so as to suppress the generation of turbulent flow and suppress the deterioration of quality due to the generation of the pre-melt TM, the deterioration of the quality of the casting can be suppressed.

[0025] The control unit 80 switches the forward speed to the second speed V2 at the changeover position WPb, which is the changeover position determined in step S40 (step S42). Steps S40 and S42 are also referred to as speed control steps. The control unit 80 changes the reference changeover position WP to the changeover position WPb (step S44). As a result, in subsequent injection processes, the forward speed is switched at the changeover position WPb, which is the changed reference changeover position WP. When the changeover position WPb coincides with the reference changeover position WP, the reference changeover position is not changed. Therefore, the generation of leading hot water TM or the generation of turbulent flow in the molten metal in subsequent injection processes can be suppressed.

[0026] When it is changed to the changeover position WPb, there are cases where the changeover position WPb is between the reference changeover position WP and the first position SP, and cases where the changeover position WPb is between the reference changeover position WP and the second position EP. Among these, the case where the changeover position WPb is between the reference changeover position WP and the first position SP is the case where it is predicted that leading hot water TM is generated. In this case, it is considered that the leading position of the molten metal is closer to the inlet 14 than the target position, and there is a high possibility that leading hot water TM will also be generated in subsequent injection processes. Therefore, by changing the reference changeover position to a position between the reference changeover position WP and the first position SP in advance, the inflow of a part of the molten metal into the cavity in subsequent injection processes can be suppressed.

[0027] On the other hand, the case where the changeover position WPb is between the reference changeover position WP and the second position EP is the case where the molten metal reaches the inlet 14 late. In this case, if the speed is switched to the second speed V2 early, the speed of the plunger 30 is switched quickly before the molten metal reaches the inlet 14, so turbulent flow may easily occur. Therefore, by bringing the changeover position closer to the second position EP, the generation of turbulent flow in subsequent injection processes can be suppressed.

[0028] The control unit 80 stops the plunger 30 at the furthest forward position FP (step S50). The control unit 80 takes out the cast product from the mold 10 (step S52). The control unit 80 retracts the plunger 30 to the first position SP (retraction step S54). The control unit 80 determines whether the casting process is completed (step S56). The control unit 80 determines that the casting process is completed, for example, when it receives an instruction to end the casting process via an end button. On the other hand, when the control unit 80 has not received an instruction to end the casting process, it determines that the casting process is not completed.

[0029] When it is determined that the casting process is completed (step S56: YES), the control unit 80 ends this processing routine. When it is determined that the casting process is not completed (step S56: NO), for the next injection process, similar to the supply step S10, the control unit 80 pours molten metal into the sleeve 20 (supply step S60). The control unit 80 sets the forward speed of the plunger 30 to the first speed V1 and advances the plunger 30, similar to step S12 (step S62). The control unit 80 depressurizes the inside of the cavity 13, similar to step S14 (step S64).

[0030] The control unit 80 changes the forward speed to the second speed V2 at the reference switching position WP (step S66). Here, if the reference switching position WP has been changed in step S44, then in step S66, the forward speed is changed at the changed switching position WPb which is the changed reference switching position WP. Therefore, since the state of the molten metal in the previous injection process can be reflected, the generation of leading molten metal TM or the generation of turbulent flow in the molten metal can be suppressed.

[0031] Similar to step S50, the control unit 80 stops the plunger 30 at the furthest forward position FP (step S68). Similar to step S52, the control unit 80 takes out the cast product from the mold 10 (step S70). Similar to the retraction step S54, the control unit 80 retracts the plunger 30 to the first position SP (retraction step S72) and proceeds to step S56 for the next injection process.

[0032] After the molten metal is supplied to the sleeve 20 in the supply step S60, the step of advancing the plunger 30 until the advancing speed is switched to the second speed V2 in step S66 is also referred to as the first step. The step of advancing the plunger 30 from the time when the advancing speed is switched to the second speed V2 greater than the first speed V1 in step S66 to the second position EP is also referred to as the second step. The process from the supply step S60 to the retreat step S72 is also referred to as the injection process.

[0033] According to the second embodiment described above, in step S40, when the arrival time is shorter than the reference time, the control unit 80 makes the switching position closer to the first position SP as the arrival time is shorter. Thereby, the switching position can be finely adjusted according to the timing detected by the detection sensor 51.

[0034] Further, in step S40, when the arrival time is longer than the reference time, the control unit 80 controls the advancing speed in step S40 so that the advancing time from the first position SP to the second position EP is longer than the reference advancing time TAt. Specifically, the longer the arrival time is, the closer the switching position is to the second position EP. Thereby, when the molten metal has not yet reached the vicinity of the introduction port, the generation of turbulent flow in the molten metal due to the advancing speed of the plunger 30 being switched to the second speed V2 before the molten metal reaches the introduction port 14 can be suppressed, and the deterioration of the quality of the cast product can be suppressed.

[0035] Further, when the control unit 80 changes the switching position in step S42 as the second step included in the supply step S10 to the retreat step S54 as the nth injection process, in step S44 executed before the start of the supply step S60 to the retreat step S72 as the (n + 1)th injection process, the reference switching position WP is changed to the changed switching position WPb. Thereby, the generation of the previous molten metal TM can be suppressed in the supply step S60 to the retreat step S72 which are subsequent injection processes.

[0036] C. Other Embodiments: (C1) In the above first embodiment, the position where the switching is made from the first speed V1 to the second speed V2 is changed to a position between the reference switching position WP and the first position SP, so that the forward movement time is set shorter than the reference forward movement time. The mode of making the forward movement time shorter than the reference forward movement time is not limited to this. For example, without changing the switching position, the second speed may be made larger than the second speed V2 in the reference state. Furthermore, the forward movement speed may use not only the two speeds of the first speed V1 and the second speed V2, but also three or more speeds.

[0037] (C2) In the above second embodiment, when the arrival time is longer than the reference time TRt, the position where the switching is made from the first speed V1 to the second speed V2 is changed to a position between the reference switching position WP and the second position EP, so that the forward movement time is set longer than the reference forward movement time. The mode of making the forward movement time longer than the reference forward movement time is not limited to this. For example, without changing the switching position, the second speed may be made smaller than the second speed V2 in the reference state.

[0038] (C3) In the above second embodiment, when the arrival time is longer than the reference time TRt, the control unit 80 uses the relationship between the arrival time and the switching position shown in FIG. 6, and the longer the arrival time is, the closer the switching position is to the second position EP. Separately from this, when the arrival time is longer than the reference time TRt, the control unit 80 may perform control to change the switching position to a predetermined position between the reference switching position WP and the second position EP regardless of the length of the arrival time. Also in this mode, by lengthening the forward movement time of the plunger 30, the generation of turbulent flow in the molten metal can be suppressed, and the deterioration of the quality of the cast product can be suppressed.

[0039] (C4) In the above first embodiment, the reference time used to determine whether the leading hot metal TM is generated is set to the time from when the plunger 30 starts to move forward until it reaches the reference switching position WP. The reference time is not limited to this, and it may be within the time from when the plunger 30 starts to move forward until it reaches the reference switching position WP.

[0040] (C5) In the second embodiment described above, in the injection process after the second time, the change of the reference switching position using the detection sensor 51 as in step S44 is not performed. Separately from this, every time, the change of the reference switching position using the detection sensor 51 as in step S44 may be performed in the injection process. Thereby, the variation in the behavior of the molten metal can be finely reflected.

[0041] (C6) In the second embodiment described above, in the injection process after the second time, the change of the reference switching position using the detection sensor 51 as in step S44 is not performed. Separately from this, for example, each time the injection process is performed several times, the configuration may be such that the reference switching position using the detection sensor 51 is changed. Thereby, while appropriately reducing the step of changing the reference switching position using the detection sensor 51, the behavior of the molten metal in the previous time can be reflected.

[0042] (C7) In the above embodiment, at the time when the molten metal reaches the inlet 14, the speed of the plunger 30 is switched from the first speed V1 to the second speed V2. The timing of switching to the second speed V2 is not limited to the time when the molten metal reaches the inlet 14. The leading edge position of the molten metal may be switched to the second speed V2 before reaching the inlet 14. Thereby, the molten metal can be made to flow into the cavity 13 earlier.

[0043] (C8) In the above embodiment, the detection sensor 51 is disposed near the inlet 14, but the placement location of the detection sensor 51 is not limited to near the inlet 14. In the second embodiment, it is preferable that the installation location of the detection sensor 51 be a location corresponding to the switching position. As described in the above (C7), in the case of the configuration in which the leading edge position of the molten metal is switched to the second speed V2 before reaching the inlet 14, by disposing the detection sensor 51 in front of the inlet 14, after the detection sensor 51 detects the arrival of the molten metal, the speed of the plunger 30 is switched. Therefore, a configuration in which the leading edge position of the molten metal is switched to the second speed V2 before reaching the inlet 14 can be realized.

[0044] The present disclosure is not limited to the above-described embodiments, and can be realized in various configurations without departing from the gist thereof. For example, the technical features of the embodiments corresponding to the technical features in each of the forms described in the summary of the invention can be appropriately replaced or combined in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Further, if the technical feature is not described as essential in this specification, it can be appropriately deleted.

Description of Reference Numerals

[0045] 1... Die casting apparatus, 10... Mold, 11... Fixed mold, 12... Movable mold, 13... Cavity, 14... Inlet, 15... Flow path, 16... Liner, 20... Sleeve, 21... Pouring port, 30... Plunger, 31... Rod, 40... Vacuum device, 41... Vacuum valve, 51... Detection sensor, 52... Stroke sensor, 80... Control unit, MM... Main flow, TM... Preheated molten metal, SP... First position, EP... Second position, FP... Furthest forward position, V1... First speed, V2... Second speed, TAt... Reference forward time, TRt... Reference arrival time, WP... Reference switching position, WPa, WPb... Changed switching positions

Claims

1. A die-casting apparatus, comprising: a mold that has an inlet for introducing molten metal and forms a cavity; a sleeve communicating with the inlet; a plunger disposed to be movable forward and backward within the sleeve, and configured to eject the molten metal supplied into the sleeve into the cavity by moving forward; a decompression device for decompressing the cavity; a detection sensor for detecting the arrival of the molten metal flowing from the sleeve toward the cavity; a control unit for controlling the forward and backward movement of the plunger, wherein the control unit when the arrival time from the start time of the forward movement of the plunger to the detection time when the detection sensor detects the arrival of the molten metal is shorter than a predetermined reference time, at least one of the switching position of the forward movement speed of the plunger and the magnitude of the forward movement speed is controlled so that the forward movement time from the position of the plunger at the detection time to the most forward position of the plunger when the supply of the molten metal to the cavity is completed is shorter than a predetermined reference forward movement time, and executes a speed control step; a first step of setting the forward movement speed to a first speed after the molten metal is supplied to the sleeve and moving the plunger from a first position, which is the position at the start time of the forward movement, to the switching position; after the first step, a second step of switching the forward movement speed to a second speed greater than the first speed and moving the plunger to a second position, which is a predetermined position on the backward side of the most forward position; when the arrival time is shorter than the reference time, the switching position is set to a reference switching position, which is the switching position at which the forward movement time becomes the reference forward movement time when the second speed is set to a predetermined reference second speed and the plunger is moved forward, and the speed control step is executed by changing the second speed to a speed greater than the reference second speed. A die-casting apparatus.

2. The die-casting apparatus according to claim 1, wherein the speed control step when the arrival time is longer than the reference time, includes controlling the forward movement speed so that the forward movement time is longer than the reference forward movement time. A die-casting apparatus.

3. The die-casting apparatus according to claim 2, A die casting apparatus that executes the speed control step by changing the switching position to a position between the reference switching position and the second position when the arrival time is longer than the reference time. **Claim 4** The die casting apparatus according to claim 3, A die casting apparatus in which when the arrival time is longer than the reference time, the longer the arrival time, the closer the switching position is to the second position. **Claim 5** The die casting apparatus according to claim 3 or 4, The control unit, A supply step of supplying the molten metal to the sleeve, After the supply step, an advancing step of advancing the plunger from the first position to the second position by the first step and the second step, After the advancing step, a retracting step of retracting the plunger to the first position, and repeatedly performing an injection process having these steps, In the second step of the nth (n is a positive integer) injection process, when the switching position is changed, before the start of the (n + 1)th injection process, the reference switching position is changed to the changed switching position. A die casting apparatus.

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