JP5823349B2 - Injection molding machine - Google Patents

Description

  The present invention relates to an injection molding machine.

  An injection molding machine manufactures a molded product by solidifying a molten resin filled in a cavity space of a mold apparatus. The mold apparatus includes a fixed mold and a movable mold, and a cavity space is formed between the fixed mold and the movable mold when the mold is clamped. Mold closing, mold clamping, and mold opening of the mold apparatus are performed by a mold clamping apparatus. As a mold clamping device, an apparatus using a linear motor for mold opening / closing operation and an electromagnet for mold clamping operation has been proposed (for example, see Patent Document 1).

  The electromagnet includes a core and a coil wound around the core. When a current is supplied to the coil, a magnetic field is generated in the coil, the core is magnetized, and the magnetic field is strengthened. Then, an attractive force is generated between the electromagnet and the soft magnetic member, and a clamping force is generated by the attractive force.

International Publication No. 2005/090052

  When the electromagnet forms a magnetic field with the soft magnetic member, the magnetic field leaks to the periphery, the peripheral member is magnetized, and a tool or the like may be attracted to the peripheral member. In order to reduce the magnetization of the peripheral members, if a current opposite to the current at the time of clamping is supplied to the coil of the electromagnet, the number of processes increases and the molding cycle (time required for one molding) increases. .

  This invention is made | formed in view of the said subject, Comprising: It aims at provision of the injection molding machine which can suppress the magnetization of a peripheral member and can suppress the prolongation of a molding cycle.

In order to solve the above problems, an injection molding machine according to an aspect of the present invention is provided.
An electromagnet that generates a clamping force for clamping the fixed mold and the movable mold;
A current supply for supplying current to the coil of the electromagnet;
A control unit for controlling the current supply unit,
The controller is characterized in that when the fixed mold and the movable mold are separated, the current supply section supplies a current in the opposite direction to the current at the time of mold clamping to the coil.

  ADVANTAGE OF THE INVENTION According to this invention, the injection molding machine which can suppress the magnetization of a peripheral member and can suppress the prolongation of a molding cycle is provided.

It is a figure which shows the state at the time of mold closing completion of the injection molding machine by one Embodiment of this invention. It is a figure which shows the state at the time of mold opening completion of the injection molding machine by one Embodiment of this invention. It is a figure which shows the control system of the injection molding machine by one Embodiment of this invention. It is a figure which shows an example of the magnetic field which an electromagnet forms at the time of mold clamping. It is a figure which shows the 1st example of the time-dependent change of the electric current supplied to the coil of an electromagnet, a mold clamping force, and a mold opening speed. It is a figure which shows the 2nd example of the time-dependent change of the electric current supplied to the coil of an electromagnet, mold clamping force, and mold opening speed. It is a figure which shows the 1st example of the time-dependent change of the electric current supplied to the coil of an electromagnet, the mold clamping force, and the mold opening speed at the time of continuous operation. It is a figure which shows the 2nd example of the time-dependent change of the electric current supplied to the coil of an electromagnet, the mold clamping force, and the mold opening speed at the time of continuous operation. It is a figure which shows the modification of FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In each of the drawings, the same or corresponding components are denoted by the same or corresponding reference numerals, and description thereof will be omitted. Further, a description will be given assuming that the moving direction of the movable platen when performing mold closing is the front and the moving direction of the movable platen when performing mold opening is the rear.

  FIG. 1 is a view showing a state when mold closing of an injection molding machine according to an embodiment of the present invention is completed. FIG. 2 is a view showing a state when the mold opening of the injection molding machine according to the embodiment of the present invention is completed.

  In the figure, 10 is an injection molding machine, Fr is a frame of the injection molding machine 10, Gd is a guide composed of two rails laid on the frame Fr, and 11 is a fixed platen. The fixed platen 11 may be provided on a position adjustment base Ba that is movable along a guide Gd that extends in the mold opening / closing direction (left-right direction in the drawing). The fixed platen 11 may be placed on the frame Fr.

  A movable platen 12 is disposed facing the fixed platen 11. The movable platen 12 is fixed on the movable base Bb, and the movable base Bb can run on the guide Gd. Thereby, the movable platen 12 is movable in the mold opening / closing direction with respect to the fixed platen 11.

  A rear platen 13 is disposed in parallel to the fixed platen 11 at a predetermined interval from the fixed platen 11. The rear platen 13 is fixed to the frame Fr via the leg portion 13a.

  Between the fixed platen 11 and the rear platen 13, four tie bars 14 (only two of the four tie bars 14 are shown in the figure) are installed as connecting members. The fixed platen 11 is fixed to the rear platen 13 via the tie bar 14. A movable platen 12 is disposed along the tie bar 14 so as to freely advance and retract. A guide hole (not shown) for penetrating the tie bar 14 is formed at a position corresponding to the tie bar 14 in the movable platen 12. In addition, you may make it form a notch part instead of a guide hole.

  A screw portion (not shown) is formed at the front end portion (right end portion in the drawing) of the tie bar 14, and the front end portion of the tie bar 14 is fixed to the fixed platen 11 by screwing and tightening a nut n1 to the screw portion. The rear end of the tie bar 14 is fixed to the rear platen 13.

  A fixed mold 15 is attached to the fixed platen 11, and a movable mold 16 is attached to the movable platen 12. The fixed mold 15 and the movable mold 16 are brought into contact with and separated from each other as the movable platen 12 advances and retreats. Closing, mold clamping and mold opening are performed. As the mold clamping is performed, a cavity space (not shown) is formed between the fixed mold 15 and the movable mold 16, and the cavity space is filled with molten resin. A mold apparatus 19 is configured by the fixed mold 15 and the movable mold 16.

  The suction plate 22 is disposed in parallel with the movable platen 12. The suction plate 22 is fixed to the slide base Sb via the mounting plate 27, and the slide base Sb can travel on the guide Gd. As a result, the suction plate 22 can move back and forth behind the rear platen 13. The adsorption plate 22 may be formed of a soft magnetic material. The attachment plate 27 may not be provided, and in this case, the suction plate 22 is directly fixed to the slide base Sb.

  The rod 39 is connected to the suction plate 22 at the rear end portion and is connected to the movable platen 12 at the front end portion. Therefore, the rod 39 is moved forward as the suction plate 22 moves forward when the mold is closed to move the movable platen 12 forward, and is retracted and moved backward as the suction plate 22 moves back when the mold is opened. Retreat. For this purpose, a rod hole 41 for penetrating the rod 39 is formed in the central portion of the rear platen 13.

  The linear motor 28 is a mold opening / closing drive unit for moving the movable platen 12 forward and backward, and is disposed, for example, between the suction plate 22 connected to the movable platen 12 and the frame Fr. The linear motor 28 may be disposed between the movable platen 12 and the frame Fr.

  The linear motor 28 includes a stator 29 and a mover 31. The stator 29 is formed on the frame Fr in parallel with the guide Gd and corresponding to the movement range of the slide base Sb. The mover 31 is formed at a lower end of the slide base Sb so as to face the stator 29 and over a predetermined range.

  The mover 31 includes a core 34 and a coil 35. The core 34 includes a plurality of magnetic pole teeth 33 that protrude toward the stator 29. The plurality of magnetic pole teeth 33 are arranged at a predetermined pitch in a direction parallel to the mold opening / closing direction. The coil 35 is wound around each magnetic pole tooth 33.

  The stator 29 includes a core (not shown) and a plurality of permanent magnets (not shown) provided on the core. The plurality of permanent magnets are arranged at a predetermined pitch in a direction parallel to the mold opening / closing direction, and the magnetic poles on the side of the mover 31 are alternately magnetized into N and S poles.

  When a predetermined current is supplied to the coil 35 of the mover 31, the mover 31 is advanced and retracted by the interaction between the magnetic field formed by the current flowing through the coil 35 and the magnetic field formed by the permanent magnet. Accordingly, the suction plate 22 and the movable platen 12 are moved back and forth, and the mold closing and mold opening are performed. The linear motor 28 is feedback-controlled based on the detection result of the position sensor 53 that detects the position of the mover 31 so that the position of the mover 31 becomes a target value. The position sensor 53 can detect the distance (mold opening / closing position) between the movable mold 33 and the fixed mold 32 by detecting the position of the movable element 31.

  In the present embodiment, the permanent magnet is disposed on the stator 29 and the coil 35 is disposed on the mover 31, but the coil may be disposed on the stator and the permanent magnet may be disposed on the mover. it can. In this case, since the coil does not move as the linear motor 28 is driven, wiring for supplying power to the coil can be easily performed.

  As the mold opening / closing drive unit, instead of the linear motor 28, a rotary motor, a ball screw mechanism that converts the rotary motion of the rotary motor into a linear motion, or a fluid pressure cylinder such as a hydraulic cylinder or a pneumatic cylinder may be used. .

  The electromagnet unit 37 generates an attracting force between the rear platen 13 and the attracting plate 22. This suction force is transmitted to the movable platen 12 via the rod 39, and a mold clamping force is generated between the movable platen 12 and the fixed platen 11.

  The electromagnet unit 37 includes an electromagnet 49 formed on the rear platen 13 side and a suction portion 51 formed on the suction plate 22 side. The suction portion 51 is formed in a predetermined portion of the suction surface (front end surface) of the suction plate 22, for example, a portion surrounding the rod 39 in the suction plate 22 and facing the electromagnet 49. A groove 45 for accommodating the coil 48 of the electromagnet 49 is formed around a predetermined portion of the attracting surface (rear end surface) of the rear platen 13, for example, around the rod 39. A core 46 is formed inside the groove 45. A coil 48 is wound around the core 46. A yoke 47 is formed at a portion other than the core 46 of the rear platen 13.

  In the present embodiment, the electromagnet 49 is formed separately from the rear platen 13 and the attracting part 51 is formed separately from the attracting plate 22, but the electromagnet is part of the rear platen 13 and the attracting part is part of the attracting plate 22. May be formed. Moreover, the arrangement of the electromagnet and the attracting part may be reversed. For example, the electromagnet 49 may be provided on the suction plate 22 side, and the suction portion 51 may be provided on the rear platen 13 side. Moreover, the number of the coils 48 of the electromagnet 49 may be plural.

  When an electric current is supplied to the coil 48 in the electromagnet unit 37, the electromagnet 49 is driven to attract the attracting part 51 and generate a mold clamping force.

  FIG. 3 is a diagram showing a control system of the injection molding machine according to the embodiment of the present invention. The control unit 60 includes, for example, a CPU and a memory, and controls operations of the linear motor 28 and the electromagnet 49 by processing a control program recorded in the memory by the CPU.

  The control unit 60 controls a current supply unit 70 that supplies current to the coil 48 of the electromagnet 49. The control unit 60 outputs a signal indicating the direction and current value (magnitude) of the current supplied to the coil 48 to the current supply unit 70.

  The current supply unit 70 is configured by, for example, an inverter including a plurality of power modules. The current supply unit 70 supplies a current corresponding to the signal supplied from the control unit 60 to the coil 48 of the electromagnet 49.

  A DC power supply 80 is connected to the current supply unit 70. The DC power supply 80 includes a rectifier 82 such as a diode that converts the AC current of the AC power supply 90 into a DC current, a capacitor 84 that smoothes the DC current output from the rectifier 82, and the like.

  The control unit 60 is connected to a mold clamping force sensor 55 that detects a mold clamping force, and sets a current value so that a predetermined mold clamping force is generated based on the detection result of the mold clamping force sensor 55. Good. The mold clamping force sensor 55 may be, for example, a strain sensor that detects distortion (elongation amount) of the tie bar 14 that expands according to the mold clamping force. As the mold clamping force sensor 55, for example, a load sensor such as a load cell that detects a load applied to the rod 39 or a magnetic sensor that detects the magnetic field of the electromagnet 49 can be used. It may be.

  Next, the operation of the injection molding machine 10 configured as described above will be described. Various operations of the injection molding machine 10 are performed under the control of the control unit 60.

  The controller 60 controls the mold closing process. In the state of FIG. 2 (mold opening completion state), the control unit 60 drives the linear motor 28 to advance the movable platen 12. As shown in FIG. 1, the movable mold 16 comes into contact with the fixed mold 15, and the mold closing process is completed. At this time, a gap δ0 is formed between the rear platen 13 and the suction plate 22, that is, between the electromagnet 49 and the suction portion 51. Note that the force required for mold closing is sufficiently reduced compared to the mold clamping force.

  Subsequently, the control unit 60 controls the mold clamping process. The control unit 60 supplies current to the coil 48 of the electromagnet 49 by the current supply unit 70 in the state of FIG. 1 (mold closing completion state). If it does so, a magnetic field will arise in the coil 48 with the electric current which flows through the coil 48, the core 46 will be magnetized, and a magnetic field will be strengthened. Then, an attracting force is generated between the electromagnet 49 and the attracting part 51 facing each other with a predetermined gap, and this attracting force is transmitted to the movable platen 12 via the rod 39, and the movable platen 12 and the fixed platen 11 are Clamping force is generated between them. The cavity space of the mold apparatus 19 in a mold-clamped state is filled with molten resin, cooled and solidified to form a molded product.

  Next, the control unit 60 controls the mold opening process. The control unit 60 supplies current to the coil 35 of the linear motor 28 to move the movable platen 12 backward. The movable mold 16 is retracted and the mold is opened. After the mold opening, an ejector device (not shown) ejects the molded product from the movable mold 16.

  Thus, the injection molding machine 10 performs a series of processes such as a mold closing process, a mold clamping process, and a mold opening process. The injection molding machine 10 performs a continuous operation for repeatedly producing a molded product by repeatedly performing a series of steps.

  FIG. 4 is a diagram illustrating an example of a magnetic field formed by an electromagnet during mold clamping. In FIG. 4, a thick solid line represents a magnetic field H1 that generates a clamping force, and a thick broken line represents a magnetic field H2 that magnetizes peripheral members.

  When the electromagnet 49 forms a magnetic field H1 with the attracting part 51 as shown by a thick solid line in FIG. 4, the magnetic field H2 leaks to the periphery as shown by a thick broken line in FIG. 4, and the tie bar 14, rod 39, mold Peripheral members such as the device 19 are magnetized.

  Therefore, the control unit 60 controls a demagnetization process for reducing the magnetization of the peripheral members. In the demagnetization process, the current supply unit 70 supplies a current in the opposite direction to the current at the time of clamping to the coil 48 of the electromagnet 49. A magnetic field opposite to that at the time of mold clamping acts on the peripheral member, and magnetization of the peripheral member can be reduced.

  When the fixed mold 15 and the movable mold 16 are separated (not in contact), the control unit 60 supplies the coil 48 with a current opposite to the current at the time of clamping by the current supply unit 70. To do. At least a part of the demagnetization process is performed simultaneously with other processes (for example, the mold opening process), and the lengthening of the molding cycle due to the addition of the demagnetization process can be suppressed.

  FIG. 5 is a diagram showing a first example of changes with time in the current supplied to the coil of the electromagnet, the mold clamping force, and the mold opening speed.

  As shown in FIG. 5, for example, during the mold opening, the control unit 60 supplies a current in the opposite direction to the current at the time of mold clamping to the coil 48 to reduce the magnetization of the peripheral members of the coil 48. This control may be performed when the distance between the fixed mold 15 and the movable mold 16 is equal to or less than a predetermined distance. If the fixed mold 15 and the movable mold 16 are too far apart, the magnetic field penetrating through the mold apparatus 19 is weakened by the air having low magnetic permeability, and the effect of reducing the magnetization of the peripheral members is weakened.

  In FIG. 5, the control unit 60 starts the demagnetization process after the mold opening is started. However, even if the demagnetization process is started at the same time as the mold opening is started, the effect of reducing the magnetization of the peripheral members is remarkably obtained. Good.

  When the distance between the fixed mold 15 and the movable mold 16 (mold opening / closing position) detected by the position sensor 53 reaches a set value, the control unit 60 may end the demagnetization process. As parameters for determining the timing of ending the demagnetization process, in addition to the mold opening / closing position, an elapsed time from the start of the demagnetization process, a measured value of the magnetic field in the vicinity of the mold apparatus 19, and the like can be used.

  FIG. 6 is a diagram showing a second example of the change over time of the current supplied to the coil of the electromagnet, the mold clamping force, and the mold opening speed. In FIG. 6, in the demagnetization step, the direction of the current supplied to the coil 48 is reversed at least once, and in the demagnetization step, the direction of the magnetic field acting on the peripheral member is reversed at least once. Before the reversal of the direction of the magnetic field, the current supply time to the coil 48 is too long, or the current value of the supply current to the coil 48 is too large. , The magnitude of the magnetization of the peripheral member again decreases after the reversal of the direction of the magnetic field. Therefore, the degree of freedom in designing the current pattern such as the current supply time to the coil 48 and the current value of the supply current to the coil 48 is increased.

  In FIG. 6, the maximum current value (current amplitude) is the same before and after the reversal of the current direction, but the maximum current value may be decreased each time the reversal is performed. In FIG. 6, the current supply time is the same before and after the reversal of the current direction, but the current supply time may be reduced each time the reversal is performed. The magnetization of the peripheral member can be reliably reduced.

  FIG. 7 is a diagram illustrating a first example of changes over time in the current supplied to the coil of the electromagnet, the mold clamping force, and the mold opening speed during continuous operation.

  The controller 60 controls the mold clamping process and the demagnetization process a predetermined number of times with the first current pattern P100 during the continuous operation, and then controls the mold clamping process and the demagnetization process a predetermined number of times with the second current pattern P200. For example, the control unit 60 switches the current pattern between the first current pattern P100 and the second current pattern P200 every time the mold clamping process and the demagnetization process are controlled once.

  In the first current pattern P100 and the second current pattern P200, the directions of current at the time of clamping are opposite to each other. During continuous operation, the direction of the magnetic field during mold clamping is repeatedly reversed, so that accumulation of magnetization of peripheral members due to the magnetic field during mold clamping can be suppressed.

  In the first current pattern P100 and the second current pattern P200, the directions of current at the time of clamping are opposite to each other, so that the direction of the current supplied to the coil 48 first in the degaussing process is also opposite.

  The second current pattern P200 may be an inversion of the first current pattern P100. That is, the first current pattern P100 and the second current pattern P200 include (1) the maximum current value in the mold clamping process, (2) the current supply time in the mold clamping process, and (3) the current direction in the demagnetization process. Number of times of reversal, (4) Current supply time after n-th inversion (n is a natural number of 0 or more) in degaussing process, and (5) Maximum after inversion of n-th (n is a natural number of 0 or more) in degaussing process The current value may be the same. During continuous operation, a magnetic field of the same magnitude and opposite direction repeatedly acts on the peripheral member, and the accumulation of magnetization of the peripheral member can be more reliably suppressed.

  In the first and second current patterns P100 and P200 in FIG. 7, the number of inversions in the current direction in the demagnetization process is plural, but may be zero.

  FIG. 8 is a diagram illustrating a second example of changes over time in the current supplied to the coil of the electromagnet, the mold clamping force, and the mold opening speed during continuous operation.

  During the continuous operation, the controller 60 controls the mold clamping process and the demagnetization process a predetermined number of times with the first current pattern P100, and then controls the mold clamping process and the demagnetization process a predetermined number of times with the second current pattern P201. For example, the control unit 60 switches the current pattern between the first current pattern P100 and the second current pattern P201 every time the mold clamping process and the demagnetization process are controlled once.

  Unlike the first example shown in FIG. 7, the first current pattern P100 and the second current pattern P201 have the same direction of current at the time of mold clamping. The direction of the supplied current is the same direction.

  Unlike the first example shown in FIG. 7, the second current pattern P201 has one more inversion of the current direction in the demagnetization process than the first current pattern P100. Therefore, as in the first example shown in FIG. 7, the direction of the current that is finally supplied to the coil 48 in the demagnetization process is opposite in the second current pattern P201 and the first current pattern P100. . Then, during continuous operation, the magnetization direction slightly remaining in the peripheral member after the demagnetization step is repeatedly reversed, so that accumulation of magnetization of the peripheral member can be suppressed.

  The second current pattern P201 may be less in number of inversions in the direction of the current in the demagnetization process than the first current pattern P100, and may be increased or decreased by an odd number of times.

  The second current pattern P201 and the first current pattern P100 may be the same pattern from the start of the mold clamping process to the middle of the demagnetization process.

  Note that the first and second current patterns P100 and P201 in FIG. 8 have a plurality of inversions in the current direction in the demagnetization process, but one of the first and second current patterns P100 and P201 has a demagnetization process. The number of inversions in the current direction at 0 may be zero.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications and substitutions may be made within the scope of the gist of the present invention described in the claims. Is possible.

  For example, in the above embodiment, the current pattern of the coil 48 of the electromagnet 49 is switched every time the mold clamping process and the demagnetization process are controlled once, but each time the mold clamping process and the demagnetization process are controlled a plurality of times. Also good. After the first current pattern is used M times (M is a natural number of 1 or more), the second current pattern is used N times (N is a natural number of 1 or more, where N ≠ M), and the first current pattern is After using the current pattern N times, the second current pattern may be used M times, or this may be repeated. In addition, the magnetization of a peripheral member can be reliably suppressed by switching the electric current pattern used for every time like the said embodiment.

  In the above embodiment, the waveform of the current supplied to the coil 48 of the electromagnet 49 in the demagnetization process is a rectangular wave, but it may be a sine wave as shown in FIG. Is not particularly limited.

  Further, in the above embodiment, the demagnetization process is started after the mold opening is started. However, as long as a current opposite to the current at the time of mold clamping is supplied to the coil 48 after the mold opening is started, the mold opening is performed after the mold clamping is completed. The demagnetization process may be started before the start, and a current opposite to the current at the time of mold clamping may be supplied to the coil 48 before the mold opening is started. After the mold clamping is finished and before the mold opening is started, while the mold clamping force is gradually reduced, a magnetic field opposite to that at the time of mold clamping acts on the core 46 of the electromagnet 49, and the residual magnetization of the core 46 is reduced in a short time. Reduce. The mold clamping force decreases in a short time, and the waiting time until the mold opening starts is shortened. Further, the direction of the supply current to the coil 48 may be reversed one or more times after the mold clamping is finished and before the mold opening is started.

DESCRIPTION OF SYMBOLS 10 Injection molding machine 15 Fixed mold 16 Movable mold 19 Mold apparatus 46 Electromagnet core 48 Electromagnet coil 49 Electromagnet 60 Control part 70 Current supply part

Claims (4)

An electromagnet that generates a clamping force for clamping the fixed mold and the movable mold;
A current supply for supplying current to the coil of the electromagnet;
A control unit for controlling the current supply unit,
The control unit is characterized in that when the fixed mold and the movable mold are separated from each other, the current supply unit supplies a current in a direction opposite to the current at the time of clamping to the coil. Injection molding machine.   2. The injection molding according to claim 1, wherein when the fixed mold and the movable mold are separated from each other, the control unit reverses the direction of the supply current to the coil at least once by the current supply unit. Machine.   3. The injection molding machine according to claim 1, wherein the control unit supplies a current in a direction opposite to a current at the time of mold clamping to the coil by the current supply unit during mold opening. 4. The control unit supplies the coil with a current in a direction opposite to the current at the time of mold clamping by the current supply unit after the mold clamping and before the mold opening starts, and the fixed mold and the movable mold, The injection molding machine according to any one of claims 1 to 3, wherein when the current is separated, the current supply unit supplies a current in a direction opposite to a current at the time of clamping to the coil .

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