Magnetic clamping apparatus and injection molding apparatus

Abstract

To provide a magnetic clamping apparatus that can perform a clamping operation flexibly according to a shape of an object to be clamped, while confirming contact between the object to be clamped and an attraction surface to ensure clamping force.SOLUTION: A magnetic clamping apparatus can be switched, by a reversal of a polarity of a first magnet 11, between an un-clamping state in which a first mold 81 is not clamped on an attraction face 25 of a first magnetic plate 6 and a clamping state to be clamped on the attraction face 25. When a first operation is performed with respect to the magnetic clamping apparatus, a clamping operation of switching from the un-clamping state into the clamping state is performed on condition that a proximity sensor 30 detects proximity of the first mold 81. When a second operation that is different from the first operation is performed, the clamping operation is performed on condition that the proximity sensor 30 does not detect the proximity of the first mold 81.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a magnetic clamping device that uses magnetism to hold an object to be clamped on an attraction surface. [Background technology]

[0002] This type of magnetic clamping device is disclosed, for example, in Patent Document 1. The magnetic clamping device of Patent Document 1 includes a plurality of magnetic adsorption units for fixing a mold and a detection means for detecting the operating state of the magnetic clamping device. Patent Document 1 also mentions a case where the magnetic clamping device includes a proximity sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2005-515080 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to obtain a strong clamping force in a magnetic clamp device, it is important that there is no gap between the clamping object and the clamping surface. Therefore, if the magnetic clamp device is equipped with a proximity sensor, it is possible to implement an interlock control that prohibits the clamping operation unless the proximity sensor detects that the clamping object is in proximity.

[0005] However, depending on the shape of the object to be clamped, the arrangement of the proximity sensor, etc., there may be cases where the clamping operation needs to be performed when the object to be clamped is not in close proximity to the proximity sensor. In such cases, the above-mentioned interlock control reduces convenience.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a magnetic clamping device that can flexibly perform clamping operation according to the shape of the object to be clamped while checking contact between the object to be clamped and the attraction surface to ensure a sufficient clamping force.

[0007] The problem to be solved by the present invention has been described above. Next, the means for solving this problem and the effects thereof will be described.

[0008] According to a first aspect of the present invention, there is provided a magnetic clamping device having the following configuration. That is, this magnetic clamping device magnetically holds a clamping object on an adsorption surface. The magnetic clamping device includes a holding member, a first magnet, a second magnet, an electromagnetic coil, and a proximity sensor. The adsorption surface is formed on the holding member. The first magnet and the second magnet are disposed on the holding member. The electromagnetic coil reverses the polarity of the first magnet by a current flowing therethrough. The proximity sensor detects a state in which the clamping object is in proximity to the adsorption surface. The magnetic clamping device is switched between a clamp release state and a clamp state by the reversal of the polarity of the first magnet. In the clamp release state, the magnetic flux from the first magnet and the magnetic flux from the second magnet do not appear on the adsorption surface. In the clamp state, the magnetic flux from the first magnet and the magnetic flux from the second magnet appear on the adsorption surface. When a first operation is performed, a clamping operation is performed to switch from the clamp release state to the clamp state, provided that the proximity sensor detects the proximity of the clamping object. When a second operation different from the first operation is performed, the clamping operation is performed on the condition that the proximity sensor does not detect the proximity of the object to be clamped.

[0009] As a result, the clamping operation is usually performed on the condition that the proximity sensor detects contact between the clamping object and the suction surface by performing the first operation, so reliable clamping can be achieved. On the other hand, there are cases where it is difficult for the proximity sensor to detect the clamping object due to circumstances such as the shape of the clamping object and the arrangement of the proximity sensor, in which case the clamping operation is performed on the condition that such detection is not performed by performing the second operation. Therefore, the clamping object can be flexibly clamped in various situations.

[0010] The magnetic clamping device is preferably configured as follows: That is, when the clamping operation is performed based on the first operation, if the proximity sensor does not detect the proximity of the object to be clamped after the clamping operation, an abnormality in the clamping state is detected. When the clamping operation is performed based on the second operation, the detection result of the proximity sensor after the clamping operation is ignored in detecting an abnormality in the clamping state.

[0011] This allows for consistent monitoring even after the clamping operation, since the clamping operation by the second operation is performed on the condition that the proximity sensor does not detect an object to be clamped.

[0012] The magnetic clamping device is preferably configured as follows. That is, the magnetic clamping device includes a detection coil that detects a change in magnetic flux when the object to be clamped moves relative to the attraction surface. When the clamping operation is performed based on the first operation, an abnormality in the clamping state is detected when the proximity sensor no longer detects the proximity of the object to be clamped or the detection coil detects a change in magnetic flux after the clamping operation. When the clamping operation is performed based on the second operation, an abnormality in the clamping state is detected when the detection coil detects a change in magnetic flux after the clamping operation.

[0013] As a result, when the clamping operation is performed by the first operation, the clamping state can be monitored in a composite manner using both the proximity sensor and the detection coil, whereas when the clamping operation is performed by the second operation, the clamping state can be appropriately monitored using the detection coil.

[0014] According to a second aspect of the present invention, there is provided an injection molding apparatus which performs injection molding using a mold fixed by the above-mentioned magnetic clamp device.

[0015] This makes it possible to realize an injection molding device that can magnetically hold a mold flexibly in a variety of situations. [Brief description of the drawings]

[0016] [Figure 1] 1 is a front view showing an overall configuration of an injection molding apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 4 is a side view showing the configuration of the first magnetic plate. [Diagram 3] FIG. [Figure 4] FIG. 13 is a schematic diagram showing a released state of the first magnetic plate. [Diagram 5] FIG. 4 is a schematic diagram showing a first magnetic plate in a locked state. [Figure 6] FIG. 2 is a block diagram showing an electrical configuration of the magnetic clamp device. [Figure 7] FIG. 4 is a diagram showing the configuration of an avoidance switch. [Figure 8] FIG. [Figure 9] FIG. 4 is an enlarged front view showing a state in the middle of attaching a mold to an injection molding device. [Figure 10] FIG. 4 is an enlarged front view showing a state immediately before a clamping operation by the magnetic clamping device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Next, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a front view showing the overall configuration of an injection molding apparatus 70 according to an embodiment of the present invention. Fig. 2 is a side view showing the configuration of a first magnetic plate 6.

[0018] 1 includes a fixed platen 71, a movable platen 72, a mold clamping device 73, a hopper 74, a heating cylinder 75, and an ejector device 76. Furthermore, the injection molding device 70 includes a magnetic clamp device 1. The magnetic clamp device 1 is used to detachably fix a first mold 81 to the fixed platen 71 and a second mold 82 to the movable platen 72, respectively.

[0019] The injection molding device 70 includes a main frame 80 formed elongated in the horizontal direction. A fixed platen 71 and a mold clamping device 73 are fixed to the main frame 80. A movable platen 72 is supported via a guide rod 78 so as to be slidable along the longitudinal direction of the main frame 80. The fixed platen 71 and the movable platen 72 are disposed to face each other in the longitudinal direction of the main frame 80.

[0020] The mold clamping device 73 includes an actuator (not shown). The configuration of the actuator is arbitrary, and may be, for example, a motor or a hydraulic cylinder. The mold clamping device 73 transmits the driving force of the actuator to the movable platen 72, and can move the movable platen 72 in a direction approaching and away from the fixed platen 71. Hereinafter, the direction in which the movable platen 72 approaches the fixed platen 71 may be referred to as the mold clamping direction D1, and the direction in which the movable platen 72 moves away from the fixed platen 71 may be referred to as the mold opening direction D2.

[0021] The hopper 74 and the heating cylinder 75 are attached to a main frame 80. The hopper 74 can store granular synthetic resin material that is the raw material for the molded product. The lower end of the hopper 74 is connected to the heating cylinder 75. The heating cylinder 75 is formed to be hollow. A screw (not shown) is arranged inside the heating cylinder 75.

[0022] An actuator (not shown) is connected to the heating barrel 75. The actuator can move the heating barrel 75 between a position where the heating barrel 75 protrudes from the fixed platen 71 toward the movable platen 72 and a retracted position. When the heating barrel 75 protrudes from the fixed platen 71, the internal space of the heating barrel 75 is connected to a cavity (not shown) formed inside the heating barrel 75 when the first mold 81 and the second mold 82 are closed. The synthetic resin material supplied to the heating barrel 75 is melted by heating and supplied to the cavity by the extrusion of the screw. In this way, the heating barrel 75 functions as a nozzle for discharging the molten material.

[0023] After the injection molding is completed, the ejector device 76 removes the molded product from the first mold 81 and the second mold 82 in the open state.

[0024] The magnetic clamp device 1 includes a first magnetic plate (holding member) 6, a second magnetic plate (holding member) 7, a controller 40, and an operation device 60.

[0025] A first magnetic plate 6 is fixed to the fixed platen 71 by bolts (not shown). Similarly, a second magnetic plate 7 is fixed to the movable platen 72 by bolts (not shown). The first magnetic plate 6 and the second magnetic plate 7 are disposed so as to face each other in the movement direction of the movable platen 72.

[0026] Each of the first magnetic plate 6 and the second magnetic plate 7 has a flat adsorption surface 25. The first mold 81 and the second mold 82, which are targets of the clamping operation performed by the magnetic clamping device 1, are made of a magnetic material, for example, iron.

[0027] The first magnetic plate 6 can be switched between a locked state and a released state. In the locked state, a magnetic flux is generated on the attraction surface 25 of the first magnetic plate 6, and the first die 81 is attracted to the attraction surface 25 by magnetic force. In the released state, the generation of the magnetic flux on the attraction surface 25 is released, and the attraction of the first die 81 is released. Similarly, the second magnetic plate 7 can be switched between a locked state and a released state.

[0028] Since the first magnetic plate 6 and the second magnetic plate 7 have substantially the same configuration, the configuration of the first magnetic plate 6 will be described below as a representative example.

[0029] The first magnetic plate 6 is formed in a plate shape. One surface of the first magnetic plate 6 in the thickness direction is fixed to a fixed plate 71, and a flat attraction surface 25 is formed on the opposite surface.

[0030] The first magnetic plate 6 comprises a plurality of magnetic pole elements 10 and a plurality of proximity sensors 30 .

[0031] As shown in FIG. 2, the multiple magnetic pole elements 10 are arranged in a lattice pattern along the attraction surface 25. Each magnetic pole element 10 is formed in a cylindrical shape. The first magnetic plate 6 is formed with the same number of recesses 26 as the magnetic pole elements 10. Each recess 26 forms a circular opening in the attraction surface 25. Each magnetic pole element 10 is arranged so as to be embedded in the corresponding recess 26. An end face on one axial side of the magnetic pole elements 10 constitutes the attraction surface 25 of the first magnetic plate 6.

[0032] The first magnetic plate 6 is provided with two types of magnetic pole elements 10, namely, N-pole type and S-pole type. The N-pole type means that the pole facing the attracting surface 25 of the first magnet 11 described below is the N-pole, and the S-pole type means that the pole is the S-pole. The magnetic pole elements 10 are provided on the first magnetic plate 6 such that two adjacent magnetic pole elements 10 in the vertical or horizontal direction have opposite pole types.

[0033] The N-pole type magnetic pole element 10N will be described in detail. As shown in Fig. 3, the N-pole type magnetic pole element 10N includes a first magnet 11, a second magnet 12, an electromagnetic coil 13, a detection coil 14, and a fixing member 15. The first magnet 11, the second magnet 12, the electromagnetic coil 13, the detection coil 14, and the fixing member 15 are all housed inside a recess 26.

[0034] The first magnet 11 is configured as a permanent magnet, for example, an alnico magnet. The first magnet 11 is formed in a disk shape, and its magnetization direction coincides with the thickness direction. In the N-pole type magnetic pole element 10N, the first magnet 11 is arranged so that the N pole faces the attracting surface 25 side and the S pole faces the opposite side to the attracting surface 25.

[0035] The second magnet 12 is configured as a permanent magnet, for example, a neodymium magnet. The second magnet 12 is formed in a cylindrical shape, and its magnetization direction coincides with the radial direction. The second magnet 12 is disposed on the outer periphery of a shaft portion 17 (to be described later) of the fixed member 15. In the N-pole type magnetic pole element 10N, the second magnet 12 is disposed so that the N pole faces radially outward and the S pole faces radially inward.

[0036] The electromagnetic coil 13 is formed by winding a thin conductor into a cylindrical shape. The electromagnetic coil 13 is disposed on the outer periphery of the disk-shaped first magnet 11. The electromagnetic coil 13 is disposed alongside the second magnet 12 in the axial direction of the magnetic pole element 10. The electromagnetic coil 13 is electrically connected to the controller 40 via a cable 18. The magnetic pole of the first magnet 11 can be reversed by passing a current through the electromagnetic coil 13 and applying a magnetic field of sufficient strength in a direction opposite to the magnetization direction of the first magnet 11.

[0037] The detection coil 14 is formed by winding a thin and long conductor in a circular shape. The detection coil 14 is fixed along the inner circumferential surface of the recess 26. The detection coil 14 detects magnetic flux passing through the inside of the detection coil 14. In this embodiment, the number of turns of the detection coil 14 is substantially one, but it may be two or more.

[0038] The fixed member 15 is formed in a generally cylindrical shape. As shown in Fig. 3, the fixed member 15 has a flange portion 16 with a large diameter and a shaft portion 17 with a small diameter. The diameter of the flange portion 16 substantially matches the diameter of the opening of the recess 26. The flange portion 16 closes the opening of the recess 26. The shaft portion 17 is disposed adjacent to the first magnet 11 in the axial direction of the magnetic pole element 10.

[0039] The proximity sensor 30 is a non-contact type sensor, and can be configured as, for example, a known semiconductor switch. The first magnetic plate 6 is formed with the same number of sensor recesses 27 as the proximity sensors 30. Each sensor recess 27 forms a circular opening in the adsorption surface 25. Each proximity sensor 30 is disposed so as to be embedded in the corresponding sensor recess 27. The detection portion of the proximity sensor 30 is disposed near the opening of the sensor recess 27. The proximity sensor 30 is turned ON when the first mold 81, which is the detection target, approaches the proximity sensor 30 so close that it comes into contact with the adsorption surface 25, and is turned OFF otherwise.

[0040] In the S-pole type magnetic pole element 10S, the magnetization directions of the first magnet 11 and the second magnet 12 are all opposite to those of the N-pole type magnetic pole element 10N. Except for this, the configuration of the S-pole type magnetic pole element 10S is the same as that of the N-pole type magnetic pole element 10N.

[0041] Next, a description will be given of the released state and the locked state of the first magnetic plate 6. The released state can be rephrased as an unclamped state, and the locked state can be rephrased as a clamped state.

[0042] In the released state, the magnetic circuit in the first magnetic plate 6 is formed as shown in FIG. 4. More specifically, in the released state, no current flows through the electromagnetic coil 13. Therefore, when focusing on a certain N-pole type magnetic pole element 10N, the magnetic flux coming out of the N-pole of the first magnet 11 passes through the second magnet 12, then passes through the adjacent S-pole type magnetic pole element 10S, in that order, through the second magnet 12 and the first magnet 11, and enters the S-pole of the first magnet 11 of the original magnetic pole element 10N. In this way, in the released state, the magnetic circuit is formed so as to loop inside the first magnetic plate 6, so that no magnetic flux is generated on the attraction surface 25. Therefore, attraction to the first mold 81 is not performed.

[0043] When a current flows through the electromagnetic coil 13 from the state shown in FIG. 4, the first magnetic plate 6 is switched to the locked state shown in FIG. 5. More specifically, in all magnetic pole elements 10 of the first magnetic plate 6, the polarity of the first magnet 11 is reversed by passing a direct current through the electromagnetic coil 13. Therefore, the magnetic pole of the surface of the first magnet 11 facing the attraction surface 25 side and the magnetic pole of the inner peripheral surface of the second magnet 12 become the same. As a result, when focusing on a certain N-pole type magnetic pole element 10N, the magnetic flux starting from the N-pole of the second magnet 12 passes through the second magnet 12 of the adjacent S-pole type magnetic pole element 10S, then passes through the first die 81 and enters the S-pole of the second magnet 12, which is the starting point. In the same magnetic pole element 10N, the magnetic flux emitted from the N pole of the first magnet 11 in the magnetic pole reversal state passes through the first magnet 11 of the adjacent S-pole type magnetic pole element 10S, then passes through the first die 81 and enters the S pole of the first magnet 11 of the original magnetic pole element 10N. In this state, both the magnetic flux based on the first magnet 11 of the magnetic pole element 10N and the magnetic flux based on the second magnet 12 appear on the attraction surface 25. As a result, the first die 81 is attracted to the attraction surface 25 by magnetic force.

[0044] Once the first die 81 is attracted to the attraction surface 25, the locked state is stably maintained by the above magnetic field lines even if the current to the electromagnetic coils 13 is stopped. This allows energy saving to be achieved. To return the first magnetic plate 6 from the locked state to the released state, a direct current in the opposite direction to the above may be applied to all the electromagnetic coils 13 provided in the first magnetic plate 6.

[0045] The second magnetic plate 7 attracts and holds the second mold 82 on the attraction surface 25 using the same principle as the first magnetic plate 6. The second magnetic plate 7 is configured substantially similarly to the first magnetic plate 6, so a description thereof will be omitted.

[0046] Next, the controller 40 and the operation device 60 will be described.

[0047] The controller 40 is configured as a known computer and includes a CPU, a ROM, a RAM, etc. The controller 40 is electrically connected to the operation device 60 and the molding device controller 90. The molding device controller 90 is a computer that controls each part of the injection molding device 70, and operates in cooperation with the controller 40 of the magnetic clamp device 1.

[0048] The controller 40 includes a current control unit 41 , a current acquisition unit 42 , a proximity sensor state acquisition unit 43 , a clamp state monitoring unit 44 , an abnormality output unit 45 , an interlock control unit 46 , and an avoidance switch 47 .

[0049] The current control unit 41 controls the current flowing through the electromagnetic coils 13 provided in each of the first magnetic plate 6 and the second magnetic plate 7.

[0050] The current acquisition unit 42 acquires the current flowing through the detection coil 14 for each of the first magnetic plate 6 and the second magnetic plate 7. An induced current is generated in the detection coil 14 in a direction that hinders changes in the magnetic flux passing through it. The magnitude of the current acquired by the current acquisition unit 42 is sampled at an appropriate frequency and an integral calculation is performed. As a result, the amount of change in the magnetic flux passing through the detection coil 14 can be obtained.

[0051] The proximity sensor state acquisition unit 43 acquires the state of the proximity sensor 30 provided on each of the first magnetic plate 6 and the second magnetic plate 7.

[0052] The clamp state monitoring unit 44 monitors the clamp state of the first magnetic plate 6 and the second magnetic plate 7 based on the current flowing through the detection coil 14 and the state of the proximity sensor 30.

[0053] The abnormality output unit 45 outputs an abnormality detection signal to the forming apparatus controller 90 when the clamp state monitoring unit 44 detects an abnormality regarding the first magnetic plate 6 and the second magnetic plate 7 .

[0054] The interlock control unit 46 performs interlock control in the magnetic clamp device 1 by exchanging signals between the controller 40 and the forming device controller 90, etc.

[0055] Interlock control regarding clamping of the first mold 81 and the second mold 82 will be described. When the molding device controller 90 detects that the first mold 81 and the second mold 82 are completely clamped, it outputs a clamping completion signal to the controller 40. The clamping state can be detected by a position sensor (not shown) provided in the injection molding device 70. The interlock control unit 46 prohibits the clamping operation and the clamp release operation of the first magnetic plate 6 and the second magnetic plate 7 unless a clamping completion signal is input from the molding device controller 90. This ensures that the first mold 81 and the second mold 82 are removed only in the clamped state, thereby preventing the first mold 81 and the second mold 82 from dropping unintentionally.

[0056] The interlock control related to the proximity sensor 30 will be described. The interlock control unit 46 prohibits the clamping operation of the first magnetic plate 6 unless, for example, the proximity sensor 30 provided in the first magnetic plate 6 detects the first mold 81 and is turned ON. Since it is possible to prevent the clamping operation from being performed when there is a gap between the adsorption surface 25 and the first mold 81, it is possible to stably and strongly clamp the first mold 81.

[0057] Interlock control regarding the evacuation of the heating barrel 75 will be described. When the molding device controller 90 detects that the heating barrel 75 has been sufficiently evacuated in a direction away from the fixed platen 71, it outputs a heating barrel evacuation completion signal to the controller 40. The evacuation state can be detected by a position sensor (not shown) provided in the injection molding device 70. The interlock control unit 46 prohibits the clamping operation and the clamp release operation of the first magnetic plate 6 and the second magnetic plate 7 unless a heating barrel evacuation completion signal is input from the molding device controller 90. This makes it possible to prevent, for example, the first mold 81 and the heating barrel 75 from colliding and being damaged when the first mold 81 is removed.

[0058] Hereinafter, the interlock control related to mold clamping may be referred to as "mold clamping interlock control", and the interlock control related to detection by the proximity sensor may be referred to as "proximity interlock control".

[0059] The avoidance switch 47 is operated to disable the above-mentioned mold clamping interlock control. As shown in FIG. 7, the avoidance switch 47 is configured as a selector switch having three operating positions. By rotating the avoidance switch 47, an operator can select from three settings regarding the mold clamping interlock control and instruct the controller 40. The first operating position corresponds to an instruction to perform the mold clamping interlock control for both the first magnetic plate 6 and the second magnetic plate 7. The second operating position corresponds to an instruction to avoid the mold clamping interlock control for the first magnetic plate 6. The third operating position corresponds to an instruction to avoid the mold clamping interlock control for the second magnetic plate 7. Avoiding the interlock control is not recommended in principle, and the second operating position or the third operating position is selected only in exceptional circumstances.

[0060] The operation device 60 is provided in a location different from the controller 40. The operation device 60 displays various statuses related to the magnetic clamp device 1, and also accepts instructions from an operator for the magnetic clamp device 1. The operation device 60 functions as an input / output device between the controller 40 and the operator.

[0061] As shown in Figures 6 and 8, the operating device 60 includes a display unit 61, a mold exchange switch 62, lock buttons (clamp operating units) 63, 65, release buttons (clamp release operating units) 64, 66, and a reset button (alarm release operating unit) 67.

[0062] The display unit 61 is composed of an LED lamp, a 7-segment LED, etc. The display unit 61 can display information related to the magnetic clamp device 1. The information that can be displayed on the display unit 61 includes an alarm display that indicates that a situation requiring attention has occurred in the magnetic clamp device 1.

[0063] The die change switch 62 is an operating member that allows the operator to instruct the die change. The die change switch 62 can be switched between ON and OFF. The lock buttons 63, 65 and the release buttons 64, 66 are only effective when the die change switch 62 is in the ON state. To prevent operational errors, the die change switch 62 is configured as a key switch that can be operated only when a key is inserted.

[0064] The lock buttons 63, 65 are operation members that allow an operator to instruct the clamping operation. Two lock buttons 63, 65 are provided corresponding to the first magnetic plate 6 and the second magnetic plate 7.

[0065] The release buttons 64, 66 are operation members that allow an operator to instruct the clamp release operation. Similar to the lock buttons 63, 65, two release buttons 64, 66 are provided.

[0066] The reset button 67 is an operating member that allows an operator to instruct the magnetic clamp device 1 to reset an alarm when an alarm occurs.

[0067] Next, a clamping operation will be described when the first mold 81 is fixed to the first magnetic plate 6. In the following, a normal case will be described in which the avoidance switch 47 has selected to perform mold clamping interlock for both the first magnetic plate 6 and the second magnetic plate 7.

[0068] Before the clamping operation is instructed, the injection molding device 70 is in the above-mentioned mold open state in advance by the molding device controller 90. Also, under the control of the molding device controller 90, the heating barrel 75 is moved in advance to the retreat position.

[0069] 4, and the second magnetic plate 7 is also in a released state. In the controller 40 provided in the magnetic clamp device 1, the current control unit 41 controls so that no current flows through the electromagnetic coils 13 in all the magnetic pole elements 10 provided in the first magnetic plate 6 and the second magnetic plate 7.

[0070] Next, the operator suspends the first mold 81 and the second mold 82 by appropriate means (for example, a crane) and carries them into the injection molding device 70 as shown in Fig. 9. After the first mold 81 and the second mold 82 are appropriately aligned, the operator appropriately operates the injection molding device 70 to clamp the molds. As a result, as shown in Fig. 10, the first mold 81 comes into contact with the attraction surface 25 of the first magnetic plate 6, and the second mold 82 comes into contact with the attraction surface 25 of the second magnetic plate 7.

[0071] Next, the operator turns on the die exchange switch 62 of the operating device 60, and further presses the lock button 63 to instruct the controller 40 to switch the first magnetic plate 6 to the locked state.

[0072] When controller 40 detects this button operation, interlock control section 46 confirms the input of a mold clamping completion signal from molding device controller 90.

[0073] When a mold clamping completion signal has been input from the molding device controller 90 to the controller 40, the interlock control unit 46 checks the state of the proximity sensor 30 of the first magnetic plate 6 via the proximity sensor state acquisition unit 43. If the proximity sensor 30 is in the ON state, the interlock control unit 46 permits switching to the locked state.

[0074] When switching to the locked state is possible, the current control section 41 of the controller 40 passes a current through the electromagnetic coil 13 of the first magnetic plate 6. As a result, the first magnetic plate 6 is switched from the released state of Fig. 4 to the locked state of Fig. 5. In this way, a clamped state in which the first magnetic plate 6 holds the first mold 81 by magnetic force is achieved. After the clamping operation is completed, the supply of current to the electromagnetic coil 13 is stopped.

[0075] While a current flows through the electromagnetic coil 13 of the first magnetic plate 6, the amount of change in the magnetic flux passing through the detection coil 14 is calculated based on the current value of the detection coil 14. The obtained amount of magnetic flux change corresponds to the magnitude of the adsorptive force. If the amount of magnetic flux change falls below a predetermined threshold, the controller 40 displays an alarm on the display unit 61.

[0076] Next, the operator presses the lock button 65 to instruct the controller 40 to switch the second magnetic plate 7 to the locked state. The same control as above is performed, and the second magnetic plate 7 is switched to the locked state. In this way, a clamped state in which the second magnetic plate 7 holds the second mold 82 by magnetic force is achieved. After that, the operator returns the mold exchange switch 62 to OFF.

[0077] Thereafter, injection molding using the first mold 81 and the second mold 82 is performed in the injection molding device 70.

[0078] In the state after the clamping operation (including during the injection molding operation), a sufficiently large adhesive force acts between the first mold 81 and the first magnetic plate 6. Therefore, the first mold 81 does not normally move relative to the first magnetic plate 6. However, it is possible that the first mold 81 may move relative to the first magnetic plate 6 or the first magnetic plate 6 may become separated from the first mold 81 for some reason, such as an unexpectedly strong force being applied to the first mold 81.

[0079] After the clamping operation, the current flowing through the detection coil 14 of the first magnetic plate 6 is acquired by the current acquisition unit 42 and constantly monitored by the clamping state monitoring unit 44. When the first die 81 moves relative to the first magnetic plate 6, the magnetic flux passing through the detection coil 14 changes, and an induced current is generated in the detection coil 14. The integral value of the current value indicates the adsorptive force lost due to the movement of the first die 81, etc. When the clamping state monitoring unit 44 detects that the integral value of the current value has reached a predetermined value or more, the abnormality output unit 45 immediately outputs a signal indicating that an abnormality in the clamping state has been detected. The calculation of the integral value of the current value may be omitted, and an abnormality in the clamping state may be determined simply based on the current value.

[0080] In parallel with the above-mentioned monitoring of the current, the state of the proximity sensor 30 of the first magnetic plate 6 is also acquired by the proximity sensor state acquisition unit 43 and is constantly monitored by the clamp state monitoring unit 44. When the first mold 81 moves away from the first magnetic plate 6, the proximity sensor 30 changes from the ON state to the OFF state. When the clamp state monitoring unit 44 detects that the proximity sensor 30 has turned OFF, the abnormality output unit 45 immediately outputs a signal indicating that an abnormality in the clamp state has been detected.

[0081] As for the second magnetic plate 7, the clamping state monitoring unit 44 similarly monitors the clamping state.

[0082] When an abnormality in the clamping state is detected, the display unit 61 of the operating device 60 displays a message indicating that an abnormality has occurred. When the molding device controller 90 receives a signal indicating that an abnormality in the clamping state has been detected from the controller 40, it performs control to immediately stop the injection molding operation, for example. This makes it possible to prevent the first mold 81 from dropping, etc.

[0083] Next, the clamp release operation for removing the first mold 81 from the first magnetic plate 6 will be described.

[0084] The operator mounts the first mold 81 and the second mold 82, which are clamped by the magnetic clamp device 1, on the above-mentioned crane.

[0085] Next, the operator switches the die exchange switch 62 of the operating device 60 to ON, and further presses the release button 64 to instruct the controller 40 to switch the first magnetic plate 6 to the release state.

[0086] When the controller 40 detects this button operation, the interlock control unit 46 confirms completion of mold clamping, completion of retraction of the heating barrel 75, etc. When the interlock control unit 46 permits the clamp release operation, the current control unit 41 passes a current in the opposite direction to the clamp operation to the electromagnetic coil 13 of the first magnetic plate 6. As a result, the first magnetic plate 6 is switched to the release state, and the clamped state is released.

[0087] Next, the operator presses the release button 66 to instruct the controller 40 to switch the second magnetic plate 7 to the released state. The same control as above is performed to switch the second magnetic plate 7 to the released state. In this way, the clamped state of the second magnetic plate 7 is also released.

[0088] In this state, the operator removes the first mold 81 and the second mold 82 suspended by the crane from the injection molding device 70.

[0089] Next, the first special mode relating to avoidance of the mold clamping interlock control will be described.

[0090] Normally, the clamping operation needs to be performed in the mold-clamped state as described above. However, there are cases where mold clamping cannot be performed due to some reason, such as a mold abnormality occurring in the injection molding device 70.

[0091] Even under such circumstances, if it is necessary to cause the first magnetic plate 6 to perform a clamping operation, the operator rotates the avoidance switch 47 in advance to select the avoidance of the mold clamping interlock for the first magnetic plate 6.

[0092] Next, the operator turns on the die exchange switch 62 and presses the lock button 63 for the first magnetic plate 6 .

[0093] According to the setting of the avoidance switch 47, the interlock control unit 46 does not check whether the mold clamping completion signal is input to the controller 40. Therefore, the clamping operation can be performed in a situation where the mold clamping completion signal is not input to the controller 40.

[0094] Next, a second special mode relating to the proximity interlock control will be described.

[0095] Normally, the clamping operation needs to be performed while the proximity sensor 30 is detecting the first mold 81 or the second mold 82. However, due to circumstances such as the punching hole formed in the first mold 81 or the second mold 82 being positioned facing the proximity sensor 30, there may be cases where the proximity sensor 30 does not turn ON even if the mold is in contact with the suction surface 25 at the correct position.

[0096] Even in such a situation, if it is necessary to have the first magnetic plate 6 perform a clamping operation, for example, the operator operates the avoidance switch 47, as in the first special mode described above, and selects to avoid the mold clamping interlock for the first magnetic plate 6. Furthermore, the operator switches the mold exchange switch 62 to ON, and while pressing the reset button 67, presses the lock button 63 for the first magnetic plate 6.

[0097] The controller 40 that detects this special operation permits switching to the locked state, on the condition that the proximity sensor 30 is in the OFF state, contrary to normal operation. Although the avoidance switch 47 is operated to avoid the mold clamping interlock control, this operation is merely for convenience. Therefore, in this second special mode, interlock controls other than the proximity interlock control (including the mold clamping interlock control) are performed in the same manner as normal.

[0098] In the second special mode, the first magnetic plate 6 clamps the first die 81 in a state where the proximity sensor 30 does not detect the first die 81. Therefore, after the clamping operation, the clamp state monitoring unit 44 does not monitor the clamp state based on the detection result of the proximity sensor 30. The clamp state is monitored based only on the current flowing through the detection coil 14.

[0099] This increases the degree of freedom in the shape of the first mold 81, making it possible to flexibly clamp first molds 81 of various shapes.

[0100] The control of the second special mode, in which the clamping operation is permitted on condition that the proximity sensor 30 is OFF, should be performed exceptionally because it reduces the reliability of the clamping. In this respect, the reset button 67 cannot maintain its pressed state unless it is touched with a finger. Therefore, in order to instruct the magnetic clamping device 1 to perform the clamping operation in the second special mode, it is necessary to press the lock button 63 while pressing the reset button 67 each time. Therefore, each time a clamping operation is performed, the operator can be made aware that it is a special operation.

[0101] The above is an operation related to the first magnetic plate 6, but by performing substantially the same operation on the second magnetic plate 7, it is possible to allow switching to the locked state on the condition that the proximity sensor 30 is OFF.

[0102] As described above, the magnetic clamping device 1 holds, for example, the first mold 81 on the attraction surface 25 of the first magnetic plate 6 by magnetism. The magnetic clamping device 1 includes the first magnetic plate 6, the first magnet 11, the second magnet 12, the electromagnetic coil 13, and the proximity sensor 30. The attraction surface 25 is formed on the first magnetic plate 6. The first magnet 11 and the second magnet 12 are arranged on the first magnetic plate 6. The electromagnetic coil 13 reverses the polarity of the first magnet 11 by the flow of current. The proximity sensor 30 detects the state in which the first mold 81 is in proximity to the attraction surface 25. The magnetic clamping device 1 is switched between a clamp release state (FIG. 4) and a clamp state (FIG. 5) by the reversal of the polarity of the first magnet 11. In the clamp release state, the magnetic flux from the first magnet 11 and the magnetic flux from the second magnet 12 do not appear on the attraction surface 25. In the clamped state, the magnetic flux from the first magnet 11 and the magnetic flux from the second magnet 12 appear on the attraction surface 25. When the setting for performing the mold clamping interlock is selected with the avoidance switch 47 and the lock button 63 is pressed, a clamping operation is performed to switch from the clamp release state to the clamped state, provided that the proximity sensor 30 detects the approach of the first mold 81 and is turned ON. When the setting for avoiding the mold clamping interlock for the first magnetic plate 6 is selected with the avoidance switch 47 and the lock button 63 is pressed while pressing the reset button 67, a clamping operation is performed, provided that the proximity sensor 30 does not detect the approach of the first mold 81 and is turned OFF.

[0103] As a result, normally, by simply pressing the lock button 63, the clamping operation is performed on the condition that the contact between the first mold 81 and the suction surface 25 is detected by the proximity sensor 30, thereby realizing reliable clamping. On the other hand, depending on circumstances such as the shape of the first mold 81 and the arrangement of the proximity sensor 30, it may be difficult for the proximity sensor 30 to detect the first mold 81. In this case, by performing the operation described in the above-mentioned second special mode, the clamping operation is performed on the condition that the proximity sensor 30 does not detect the first mold 81. Therefore, the first mold 81 can be flexibly clamped in various situations.

[0104] In the magnetic clamp device 1 of this embodiment, when a setting for performing mold clamping interlock is selected with the avoidance switch 47 and a clamping operation is performed based on the operation of pressing the lock button 63, if the proximity sensor 30 no longer detects the proximity of the first mold 81 after the clamping operation and turns OFF, an abnormality in the clamping state is detected. On the other hand, when a setting for avoiding mold clamping interlock for the first magnetic plate 6 is selected with the avoidance switch 47 and a clamping operation is performed based on the operation of pressing the lock button 63 while pressing the reset button 67, the detection result of the proximity sensor 30 after the clamping operation is ignored in detecting an abnormality in the clamping state.

[0105] This allows for consistent monitoring even after the clamping operation, in accordance with the condition that the proximity sensor 30 does not detect the first mold 81 when the clamping operation is performed by the operation described in the second special mode.

[0106] The magnetic clamping device 1 of this embodiment includes a detection coil 14 that detects a change in magnetic flux when the first mold 81 moves relative to the adsorption surface 25. When a clamping operation is performed based on an operation of pressing the lock button 63 after selecting a setting for performing mold clamping interlock with the avoidance switch 47, an abnormality in the clamping state is detected when the proximity sensor 30 no longer detects the proximity of the first mold 81 and turns OFF after the clamping operation, or when the detection coil 14 detects a change in magnetic flux. When a setting for avoiding mold clamping interlock for the first magnetic plate 6 is selected with the avoidance switch 47, and a clamping operation is performed based on an operation of pressing the lock button 63 while pressing the reset button 67, an abnormality in the clamping state is detected when the detection coil 14 detects a change in magnetic flux after the clamping operation.

[0107] As a result, when the clamping operation is performed simply by pressing the lock button 63, the clamping state can be monitored in a composite manner using both the proximity sensor 30 and the detection coil 14. On the other hand, when the clamping operation is performed by the operation described in the second special mode, the clamping state can be appropriately monitored based on the detection coil 14.

[0108] The injection molding apparatus 70 of this embodiment performs injection molding using a mold fixed by the magnetic clamp device 1.

[0109] This makes it possible to realize an injection molding device that can magnetically hold a mold flexibly in a variety of situations.

[0110] Although the preferred embodiment of the present invention has been described above, the above configuration can be modified, for example, as follows. Each modification may be made alone, or multiple modifications may be made in any combination.

[0111] The magnetic clamping device can be modified to perform the following operation. That is, when the setting for performing the mold clamping interlock is selected with the avoidance switch 47 and then the lock button 63 is pressed, whether the state of the proximity sensor 30 is ON or OFF does not affect permission for the clamping operation (that is, the interlock control unit 46 does not perform the proximity interlock control). After the clamping operation is completed, if the state of the proximity sensor 30 changes from ON to OFF or the detection coil 14 detects a change in magnetic flux, an abnormality in the clamping state is detected. This control is effective in cases where the proximity sensor 30 is often unable to detect the mold before the clamping operation.

[0112] The detection coil 14 may be used in common with the electromagnetic coil 13. The detection coil 14 may be disposed on only a portion of the multiple magnetic pole elements 10.

[0113] The avoidance switch 47 may be provided on the operation device 60. The operation device 60 and the controller 40 may be integrally configured.

[0114] The operation for instructing the magnetic clamping device 1 to clamp is not limited to the above. For example, an operation of pressing the lock button 63 while pressing an appropriate button other than the reset button 67 may be performed.

[0115] The number of magnetic pole elements 10 and the number of proximity sensors 30 may be changed as appropriate. One of the first magnetic plate 6 and the second magnetic plate 7 may be omitted.

[0116] The magnetic clamping device 1 can be applied to machines other than the injection molding device 70. The magnetic clamping device 1 may be configured to magnetically clamp something other than a mold, for example, a workpiece to be processed. [Explanation of symbols]

[0117] 1 Magnetic clamping device 6 First magnetic plate (holding member) 7 Second magnetic plate (holding member) 11 First magnet 12 Second magnet 13 Electromagnetic Coil 14 Detection coil 25 Adsorption surface 30 Proximity Sensor 70 Injection molding equipment 81 First mold (clamp object) 82 Second mold (clamping object)

Claims

1. A magnetic clamping device that magnetically holds an object to be clamped on an attraction surface, a holding member on which the adsorption surface is formed; A first magnet disposed on the holding member; A second magnet disposed on the holding member; an electromagnetic coil that reverses the polarity of the first magnet when a current flows through it; a proximity sensor that detects a state in which the object to be clamped is in proximity to an attraction surface; Equipped with By reversing the polarity of the first magnet, switching is performed between an unclamped state in which the magnetic flux from the first magnet and the magnetic flux from the second magnet are not present on the attraction surface and a clamped state in which the magnetic flux from the first magnet and the magnetic flux from the second magnet are present on the attraction surface, When a first operation is performed, a clamping operation is performed to switch from the clamp release state to the clamped state on condition that the proximity sensor detects the proximity of the clamp object, A magnetic clamping device characterized in that, when a second operation different from the first operation is performed, the clamping operation is performed on the condition that the proximity sensor does not detect the proximity of the object to be clamped.

2. 2. The magnetic clamping device of claim 1, When the clamping operation is performed based on the first operation, if the proximity sensor does not detect the proximity of the clamping object after the clamping operation, an abnormality in the clamping state is detected, A magnetic clamping device, characterized in that, when the clamping operation is performed based on the second operation, the detection result of the proximity sensor after this clamping operation is ignored in detecting an abnormality in the clamping state.

3. 3. The magnetic clamping device according to claim 2, a detection coil for detecting a change in magnetic flux when the clamping object moves relative to the attraction surface; When the clamping operation is performed based on the first operation, if the proximity sensor does not detect the proximity of the object to be clamped after the clamping operation or if the detection coil detects a change in magnetic flux, an abnormality in the clamping state is detected, A magnetic clamping device characterized in that, when the clamping operation is performed based on the second operation, if the detection coil detects a change in magnetic flux after the clamping operation, an abnormality in the clamping state is detected.

4. 4. An injection molding apparatus for performing injection molding using a mold fixed by the magnetic clamp device according to claim 1.

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