Abnormality detection method for die-casting injection device

Abstract

To provide an abnormality detection method of an injection device for die casting capable of detecting abnormality of a screwed state of a plunger tip and a plunger rod.SOLUTION: An abnormality detection method for a die-casting injection device having a plunger including a plunger tip for injecting a molten metal supplied into a plunger sleeve and a plunger rod for advancing and retracting the plunger tip screwed to a distal end of the plunger rod into and from the plunger sleeve, the abnormality detection method including detecting an abnormality in a screwed state of the plunger tip and the plunger rod during an injection operation based on measurement data of a measurement sensor that measures a displacement in a rotation direction of at least one of the plunger tip and the plunger rod.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a method for detecting an abnormality in a die-casting injection device, and more particularly to a method for detecting an abnormality in a die-casting injection device having a plunger including a plunger tip for injecting molten metal supplied into a plunger sleeve, and a plunger rod for moving the plunger tip, threaded onto the tip, back and forth within the plunger sleeve. [Background technology]

[0002] Patent Document 1 discloses a die casting apparatus using this type of die casting injection device.

[0003] The die-casting apparatus described in Patent Document 1 includes a plunger sleeve to which molten metal is supplied for injection into a mold cavity, a plunger tip for injecting the molten metal supplied into the plunger sleeve toward the cavity, and a plunger rod for moving the plunger tip back and forth in the direction of injection of the molten metal, and further includes an acceleration sensor capable of detecting acceleration in three axial directions in the plunger sleeve and at least one of the plunger tip and plunger rod.

[0004] In this way, it is described that by providing the plunger sleeve and at least one of the plunger tip and plunger rod with an acceleration sensor capable of detecting acceleration in three axial directions, the detection accuracy of galling (friction) occurring between the plunger tip and plunger sleeve can be improved. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-138209 Summary of the Invention [Problem to be solved by the invention]

[0006] In die-casting injection devices having a plunger rod and a plunger including the plunger rod, a plunger tip is often threaded onto the tip of the plunger rod. During the injection operation of the die-casting injection device, if the plunger tip threaded onto the tip of the plunger rod comes into contact with the molten metal in the plunger sleeve, the plunger tip may not be able to rotate due to frictional resistance between the plunger tip and the molten metal. If the plunger rod rotates in this situation, the threaded engagement between the plunger tip and the plunger rod may loosen depending on the direction of rotation.

[0007] However, the technology described in Patent Document 1 has a problem in that it is difficult to detect an abnormality in the screwed state of the plunger tip and plunger rod during injection operation. An abnormality in the screwed state that causes the plunger tip and plunger rod to become loose can lead to problems such as leakage of cooling water that cools the plunger tip and poor sliding of the plunger tip, resulting in a decrease in the quality of molded products, so it is necessary to detect signs of loosening of the screwed state early.

[0008] The present disclosure has been made to solve such problems, and aims to provide an abnormality detection method for a die-casting injection device that can detect abnormalities in the threaded engagement state of the plunger tip and plunger rod. [Means for solving the problem]

[0009] One embodiment of the method for detecting an abnormality in a die-casting injection device is a method for detecting an abnormality in a die-casting injection device having a plunger including a plunger tip for injecting molten metal supplied into the plunger sleeve, and a plunger rod for moving the plunger tip threaded to the tip back and forth within the plunger sleeve, and detects an abnormality in the threaded state of the plunger tip and plunger rod during the injection operation based on measurement data from a measurement sensor that measures the displacement in the rotational direction of at least one of the plunger tip and plunger rod. [Effects of the Invention]

[0010] The present disclosure provides an abnormality detection method for a die-casting injection device that can detect an abnormality in the threaded engagement state of a plunger tip and a plunger rod. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a front cross-sectional view illustrating a die-casting machine provided with a die-casting injection device according to a first embodiment. [Figure 2] 1 is a front cross-sectional view illustrating the injection operation of the die-casting injection device according to the first embodiment when the device is moving forward. FIG. [Figure 3] 1 is a front cross-sectional view illustrating the extrusion stage of the injection operation of the die-casting injection device according to the first embodiment. FIG. [Figure 4] 3 is a front cross-sectional view illustrating the injection operation of the die-casting injection device according to the first embodiment when the device is retracting. FIG. [Figure 5] 3 is a flowchart illustrating an anomaly detection method according to the first embodiment. [Figure 6] 10 is a graph illustrating an example of a waveform of time-series data of acceleration. DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiment 1 Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. For clarity of explanation, the following description and drawings have been simplified as appropriate. What is shown in the drawings is only a part of the whole, and many other configurations not shown are actually included. In the following description, identical or equivalent elements are given the same reference numerals, and redundant explanations will be omitted. The right-handed xyz coordinate system shown in the drawings is for the sake of convenience in explaining the positional relationship of the components. Unless otherwise specified, the positive direction of the z axis is vertically upward. The xy plane is a horizontal plane.

[0013] Fig. 1 is a front cross-sectional view illustrating a die-casting machine provided with a die-casting injection device according to embodiment 1. As shown in Fig. 1, injection device 10, which is the die-casting injection device according to embodiment 1, is provided in die-casting machine 1.

[0014] In addition to the injection device 10, the die-casting apparatus 1 is equipped with a mold 20 including a movable mold 21 and a fixed mold 22. When the movable mold 21 and the fixed mold 22 are clamped together, a cavity C, which is a hollow space for molding a molded product P, is formed in the mold 20.

[0015] The injection device 10 is a device that injects molten metal M into a cavity C of a mold 20. The injection device 10 includes a plunger sleeve 11, a plunger 14 including a plunger tip 12 and a plunger rod 13, and an injection cylinder (not shown). Fig. 1 shows a horizontal injection type injection device 10 that is arranged so that the axial direction of the plunger sleeve 11 is parallel to the horizontal direction.

[0016] The plunger sleeve 11 is supplied with molten metal M to be injected and filled into the cavity C. The plunger sleeve 11 is, for example, cylindrical in shape. The plunger sleeve 11 is connected to the fixed die 22 of the mold 20 and is disposed so as to communicate with the movable die 21. The plunger sleeve 11 has a pouring port 11a on its upper surface for supplying the molten metal M into the inside of the plunger sleeve 11. The molten metal M is, for example, molten aluminum. The plunger sleeve 11 also has an injection port 11b that opens so as to communicate with the cavity C.

[0017] The plunger tip 12 is a plunger member for injecting the molten metal M supplied into the plunger sleeve 11. The plunger tip 12 is screwed onto the tip (the end on the negative side of the x-axis) of the plunger rod 13 and is disposed inside the plunger sleeve 11. The shape of the plunger tip 12 is a shape that follows the shape of the inner surface of the plunger sleeve 11 and can be a shape that allows it to slide inside the plunger sleeve 11. For example, if the plunger sleeve 11 is cylindrical, the shape of the plunger tip 12 is preferably columnar. The plunger tip 12 slides inside the plunger sleeve 11 and injects the molten metal M inside the plunger sleeve 11 by pushing it out into the cavity C.

[0018] The plunger rod 13 is a plunger member for moving the plunger tip 12, which is threaded onto the tip, back and forth within the plunger sleeve 11. The plunger rod 13 moves back and forth within the plunger sleeve 11 together with the plunger tip 12. The plunger rod 13 is fixed to a surface of the plunger tip 12 opposite to the surface that contacts the molten metal M (the yz plane on the negative side of the x-axis) (the yz plane on the positive side of the x-axis). The plunger rod 13 has a cylindrical or rectangular tubular shape extending in the axial direction of the plunger sleeve 11. A cooling water hose (not shown) for supplying and discharging cooling water to cool the plunger tip 12 may be connected to the plunger rod 13.

[0019] The injection cylinder is connected to the plunger rod 13. For example, the cylinder rod of the injection cylinder is connected to the base end (the end on the x-axis positive side) of the plunger rod 13 via a coupling. The injection cylinder moves the plunger 14 back and forth within the plunger sleeve 11. This causes the plunger 14 to move in a movement direction (x-axis direction) in which the plunger 14 moves back and forth between a predetermined injection start position and an injection completion position. The injection start position is a position at which injection of the molten metal M into the cavity C starts, and the injection completion position is a position at which injection of the molten metal M into the cavity C is completed.

[0020] The injection device 10 further includes an acceleration sensor S. The acceleration sensor S can measure acceleration in at least two axial directions: the direction of movement of the plunger 14 and a planar direction (y-axis direction) that is a direction perpendicular to the direction of movement. The planar direction is a direction perpendicular to both the direction of movement and the vertical direction.

[0021] The acceleration sensor S may be capable of measuring acceleration in at least two axial directions, i.e., the direction of movement and a direction perpendicular to the direction of movement, but is not limited to this. The acceleration sensor S may be capable of measuring acceleration in three axial directions. In this embodiment, the acceleration sensor S is also capable of measuring acceleration in the vertical direction (z-axis direction).

[0022] The acceleration sensor S is provided on at least one of the plunger tip 12 and the plunger rod 13. In this embodiment, as shown in Fig. 1, the acceleration sensor S is provided on the upper surface side (positive side of the z-axis) of the plunger rod 13, but is not limited to this. More specifically, the acceleration sensor S may be provided anywhere on the outer circumferential surface of the plunger rod 13, for example.

[0023] Measurement of acceleration using the acceleration sensor S can be performed continuously over time, for example, from the start of injection to the completion of injection, that is, from the time when the plunger tip 12 advances within the plunger sleeve 11 from the injection start position to the injection completion position until it retreats to the injection start position. Note that it is also possible to set one or more arbitrary acceleration measurement positions (timings) and measure acceleration at those timings.

[0024] The acceleration sensor S is communicably connected to a personal computer (not shown). The acceleration sensor S is preferably communicably connected to the personal computer wirelessly, but may be communicatively connected via a wire. The acceleration sensor S transmits the acquired measurement data to the personal computer. The personal computer includes a display medium such as a liquid crystal monitor. The display medium displays various information related to abnormality detection of the injection device 10, including the measurement data.

[0025] The measurement data is preferably time-series data of the measurement values ​​of the acceleration sensor S. This makes it possible to easily grasp the cycle and timing of the injection operation when detecting an abnormality in the injection device 10.

[0026] Next, the injection operation of the injection device 10 will be described with reference to Figures 2 to 4 as well as Figure 1. First, as shown in Figure 1, at the injection start position, the plunger 14 is located rearward (in the positive direction of the x-axis) of the pouring port 11a of the plunger sleeve 11, and molten metal M is supplied into the plunger sleeve 11 through the pouring port 11a.

[0027] 2 is a front cross-sectional view illustrating the forward movement of the injection operation of the die-casting injection device according to the first embodiment. When molten metal M is supplied into the plunger sleeve 11, as shown in FIG. 2, the plunger 14 moves forward from the injection start position in the forward direction (negative direction of the x-axis) indicated by the outline arrow, causing the plunger tip 12 to inject the molten metal M into the cavity C through the injection port 11b.

[0028] Next, Figure 3 is a front cross-sectional view illustrating the extrusion stage of the injection operation of the die-casting injection device according to the first embodiment. When the injection of molten metal M into cavity C is completed, as shown in Figure 3, mold 20 is opened and the molded product P is released from mold 20 by being pushed out by plunger tip 12. Specifically, after molten metal M is solidified to form molded product P, movable mold 21 moves in the direction of the black arrow (negative x-axis direction). As movable mold 21 moves, plunger tip 12 moves forward in the forward direction (negative x-axis direction) indicated by the white arrow to push out molded product P, thereby releasing molded product P from fixed mold 22.

[0029] 4 is a front cross-sectional view illustrating the retraction of the injection operation of the die-casting injection device according to embodiment 1. After the molded product P is extruded, as shown in FIG. 4, the plunger tip 12 retracts from the injection completion position in the retraction direction (positive x-axis direction) indicated by the outline arrow to return to the injection start position.

[0030] In this way, the injection device 10 can inject the molten metal M supplied into the plunger sleeve 11 into the cavity C of the mold 20 by the plunger tip 12 as the injection cylinder moves the plunger 14 back and forth.

[0031] In such an injection device 10, as the plunger 14 moves back and forth during the injection operation, at least one of the plunger tip 12 and the plunger rod 13 may rotate in a loosening direction that loosens the threaded engagement between the plunger tip 12 and the plunger rod 13.

[0032] For example, during the injection operation of the injection device 10, if the plunger tip 12 is in contact with the molten metal M in the plunger sleeve 11, the plunger tip 12 may not be able to rotate due to frictional resistance between the plunger tip 12 and the molten metal M. At this time, if the plunger rod 13 rotates in a direction that loosens the threaded engagement between the plunger tip 12 and the plunger rod 13, the threaded engagement between the plunger tip 12 and the plunger rod 13 may loosen.

[0033] Abnormalities in the threaded condition, such as loosening of the plunger tip 12 and plunger rod 13, can lead to problems such as leakage of the cooling water that cools the plunger tip 12 and a decrease in the quality of the molded product P due to poor sliding of the plunger tip 12, so it is necessary to detect signs of loosening of the threaded connection early.

[0034] Therefore, the abnormality detection method of embodiment 1 detects abnormalities in the threaded engagement state of the plunger tip 12 and the plunger rod 13 during the injection operation based on measurement data from an acceleration sensor S as a measurement sensor that measures the displacement of at least one of the plunger tip 12 and the plunger rod 13 in the rotational direction.

[0035] Fig. 5 is a flowchart illustrating an example of an anomaly detection method according to the first embodiment. The series of flows shown in Fig. 5 is executed, for example, for each cycle of the injection operation. Note that one cycle of the injection operation refers to the cycle from the start of injection to the completion of injection.

[0036] Hereinafter, the abnormality detection method for the injection device 10 (hereinafter referred to as the abnormality detection method) will be described, taking as specific example a case where the measurement data of the acceleration sensor S provided on the plunger rod 13 is time-series data.

[0037] 5, step S1 is a process of measuring the displacement in the rotational direction of the plunger rod 13 by measuring acceleration in at least two axial directions, the direction of movement and the plane direction. In step S1, first, the acceleration sensor S provided on the plunger rod 13 is made to measure acceleration in at least two axial directions, the direction of movement and the plane direction. In this embodiment, since the acceleration sensor S is capable of measuring acceleration in three axial directions, it measures acceleration in the vertical direction in addition to the two axial directions, the direction of movement and the plane direction.

[0038] Next, step S2 is a process of acquiring time series data. In step S2, the time series data acquired by the acceleration sensor S is input into a personal computer connected to the acceleration sensor S.

[0039] Next, step S3 is a step of determining, based on the time-series data of the acceleration sensor S, whether or not the plunger rod 13 has rotated.

[0040] Here, Fig. 6 is a graph illustrating an example of the waveform of time-series data of acceleration. The vertical axis of the graph shown in Fig. 6 represents acceleration (G), and the horizontal axis represents time. The lower part of Fig. 6 shows a graph that shows the graph shown in the upper part of Fig. 6 with the vertical axis scale changed.

[0041] The waveform in the region indicated by the dashed line (c1) in the graph of FIG. 6 indicates the acceleration measured by the acceleration sensor S when the plunger 14 retracted in the previous cycle. The waveform in the region indicated by the dashed line (a2) in the graph of FIG. 6 indicates the acceleration measured by the acceleration sensor S when the plunger 14 advanced in the next cycle. The waveform in the region indicated by the dashed line (b2) in the graph of FIG. 6 indicates the acceleration measured by the acceleration sensor S when the mold opened and the plunger tip 12 ejected the molded product P. The waveform in the region indicated by the dashed line (c2) in the graph of FIG. 6 indicates the acceleration measured by the acceleration sensor S when the plunger 14 retracted after the molded product P was ejected.

[0042] 6, the acceleration values ​​measured by the acceleration sensor S provided on the plunger rod 13 in the movement direction, planar direction, and vertical direction change when vibration occurs in the plunger rod 13. The acceleration value measured in the planar direction by the acceleration sensor S provided on the plunger rod 13 increases while the plunger rod 13 is rotating in the loosening direction to loosen the threaded engagement with the plunger tip 12, decreases while the plunger rod 13 is rotating in the tightening direction to tighten the threaded engagement with the plunger tip 12, and does not change while the plunger rod 13 is not rotating.

[0043] Therefore, for example, when the plunger rod 13 is not rotating during one cycle of the injection operation, the waveform of the acceleration in the planar direction shows almost the same shape as the waveform of the acceleration in the vertical direction. On the other hand, when the plunger rod 13 is rotating during one cycle of the injection operation, the waveform of the acceleration in the planar direction shows a different shape from the waveform of the acceleration in the vertical direction.

[0044] In step S3, the waveforms of the time series data of acceleration in the direction of movement and the time series data of acceleration in the planar direction are compared, and if the waveform of acceleration in the planar direction shows a different shape from the waveform of acceleration in the vertical direction, it can be determined that the plunger rod 13 has rotated.

[0045] 5, if it is determined that the plunger rod 13 has rotated (step S3: YES), the process proceeds to step S4. On the other hand, if it is determined that the plunger rod 13 has not rotated (step S3: NO), the process proceeds to step S8, where it is determined that the threaded state of the plunger tip 12 and the plunger rod 13 is normal. Then, the series of steps ends.

[0046] Step S4 is a step of determining whether the timing at which plunger rod 13 rotates is the timing at which the plunger moves forward.

[0047] Here, loosening of the threaded engagement between the plunger tip 12 and the plunger rod 13 is likely to occur particularly when the plunger 14 moves forward. This is because, when the plunger 14 moves forward, the injection device 10 switches the injection speed from low to high depending on the position of the plunger tip 12, causing greater vibrations in the plunger rod 13 than at other times during the injection operation.

[0048] Furthermore, the greater the vibration, the higher the acceleration measurement value will be, as shown in FIG. 6, so it is easy to determine when the plunger 14 is moving forward from the time-series data of acceleration.

[0049] In step S4, the waveform in the area indicated by the dashed line (a2) in the graph shown in Figure 6 is checked, and if there is an increase or decrease in the measured value of the acceleration in the planar direction due to the rotation of the plunger rod 13, it can be determined that the timing when the plunger rod 13 rotated is the time when the plunger 14 moved forward.

[0050] 5, if it is determined that the plunger 14 is moving forward (step S4: YES), the process proceeds to step S5. On the other hand, if it is determined that the plunger 14 is not moving forward (step S4: NO), the process proceeds to step S8, where it is determined that the threaded state of the plunger tip 12 and the plunger rod 13 is normal. Then, the series of flows ends.

[0051] Step S5 is a process for determining whether the rotation direction of the plunger rod 13 when the plunger 14 moves forward is the loosening direction. In step S5, the waveform in the region indicated by the dashed line (a2) in the graph shown in Fig. 6 is checked, and if the measured value of the acceleration in the planar direction shows an increasing trend, it can be determined that the rotation direction of the plunger rod 13 when the plunger 14 moves forward is the loosening direction.

[0052] 5, if it is determined that the rotation direction of the plunger rod 13 is the loosening direction (step S5: YES), the process proceeds to step S6, where it is determined that the threaded state of the plunger tip 12 and the plunger rod 13 is abnormal. On the other hand, if it is determined that the rotation direction of the plunger rod 13 is not the loosening direction (step S4: NO), the process proceeds to step S8, where it is determined that the threaded state of the plunger tip 12 and the plunger rod 13 is normal. Then, the series of flows ends.

[0053] After determining in step S6 that the threaded state of the plunger tip 12 and the plunger rod 13 is abnormal, the process proceeds to step S7, where corrective measures are taken to improve the looseness of the threaded state of the plunger tip 12 and the plunger rod 13. Then, the process returns to step S1, and the series of steps are repeated until it is determined that the threaded state of the plunger tip 12 and the plunger rod 13 is normal.

[0054] As described above, the abnormality detection method according to this embodiment uses the measurement data of the acceleration sensor S to monitor the screwed state of the plunger tip 12 and the plunger rod 13 of the injection device 10, and detects abnormalities in the screwed state in which the screwed state of the plunger tip 12 and the plunger rod 13 becomes loose. Therefore, signs of loosening of the screwed state can be found early.

[0055] As described above, according to this embodiment, it is possible to provide an abnormality detection method for the injection device 10 that can detect an abnormality in the screwed state of the plunger tip 12 and the plunger rod 13.

[0056] The present disclosure is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the present disclosure.

[0057] In the above embodiment, the abnormality detection method using the acceleration sensor S provided on the plunger rod 13 has been described. However, the acceleration sensor S may be provided on at least one of the plunger tip 12 and the plunger rod 13. For example, the sensor S may be provided on the plunger tip 12, or on the surface of the plunger tip 12 opposite to the surface that contacts the molten metal M (the yz plane on the negative side of the x-axis) (the yz plane on the positive side of the x-axis). Furthermore, the acceleration sensor S may be provided so as to contact both the surface of the plunger tip 12 opposite to the surface that contacts the molten metal M (the yz plane on the negative side of the x-axis) (the yz plane on the positive side of the x-axis) and the outer circumferential surface of the plunger rod 13. Alternatively, the acceleration sensor S may be provided on both the plunger tip 12 and the plunger rod 13.

[0058] In other words, the location of the acceleration sensor S can be appropriately selected according to the specifications of the injection device 10, such as a location that does not interfere with the cooling water hose connected to the plunger sleeve 11 or the plunger rod 13, or a location that is less susceptible to the heat generated by the molten metal M.

[0059] Furthermore, in the above embodiment, the abnormality detection method for the horizontal injection type injection device 10 has been described, but the injection device 10 is not limited to the horizontal injection type, and may be a vertical injection type.

[0060] Furthermore, in the above embodiment, an abnormality detection method using an acceleration sensor S capable of measuring acceleration in a planar direction as a direction orthogonal to the movement direction in addition to acceleration in the movement direction has been described. However, the direction orthogonal to the movement direction may be the vertical direction instead of the planar direction. When the direction orthogonal to the movement direction is the vertical direction, the acceleration sensor S is only required to be able to measure acceleration in at least two axial directions, the movement direction and the vertical direction. As the direction orthogonal to the movement direction, a direction in which rotational displacement due to the rotational movement of the plunger member to which the acceleration sensor S is attached is likely to occur can be appropriately selected from the planar direction and the vertical direction according to the specifications of the injection device 10.

[0061] Furthermore, in the above embodiment, an anomaly detection method using an acceleration sensor S that measures acceleration in at least two axial directions including the direction of movement has been described as an example of a measurement sensor, but the measurement sensor is not limited to the acceleration sensor S as long as it is capable of measuring displacement in the rotational direction of at least one of the plunger tip 12 and plunger rod 13. The measurement sensor used in the anomaly detection method may be, for example, an angular velocity sensor (gyro sensor) or a motion capture device. [Explanation of symbols]

[0062] 1. Die-casting equipment 10 Injection device 11 plunger sleeve 11a pouring port 11b injection port 12 plunger tip 13 plunger rod 14 plunger 20 Mold 21 Movable type 22 Fixed type C Cavity M Molten metal P Molded product S Acceleration sensor

Claims

1. A method for detecting an abnormality in a die-casting injection device having a plunger including a plunger tip for injecting molten metal supplied into a plunger sleeve, and a plunger rod threadedly attached to the tip for moving the plunger tip back and forth within the plunger sleeve, comprising: An abnormality detection method for a die-casting injection device that detects abnormalities in the threaded engagement state of the plunger tip and the plunger rod during an injection operation based on measurement data from a measurement sensor that measures the rotational displacement of at least one of the plunger tip and the plunger rod.

2. 2. The method for detecting an abnormality in a die-casting injection device according to claim 1, wherein the measurement sensor is provided on the plunger rod.

3. 2. The method for detecting an abnormality in a die-casting injection device according to claim 1, wherein the measurement data is time-series data of the measurement values ​​of the measurement sensor.

4. 2. The method for detecting an abnormality in a die-casting injection device according to claim 1, wherein the measurement sensor is an acceleration sensor capable of measuring acceleration in at least two axial directions, namely, the direction in which the plunger moves back and forth and a direction perpendicular to the direction of movement.

5. 5. The method for detecting an abnormality in a die-casting injection device according to claim 4, wherein the direction perpendicular to the moving direction is a planar direction perpendicular to the moving direction and the vertical direction.

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