JP5726788B2 - Injection molding machine - Google Patents

Description

  The present invention relates to an injection molding machine.

  An injection molding machine manufactures a molded product by filling molten resin into a cavity space of a mold apparatus and solidifying the resin. 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).

WO05 / 090052 pamphlet

  FIG. 6 is a diagram showing a current pattern of an electromagnet of a conventional injection molding machine.

  The electromagnet includes a core and a coil wound around the core. When a direct current is supplied to the coil, a magnetic field is generated in the coil by the direct current flowing through 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 facing each other with a predetermined gap, and a mold clamping force is generated by the attractive force.

  When releasing the mold clamping force, the core is demagnetized. To demagnetize the core, first, a direct current in the opposite direction to that during magnetization is supplied to the coil, and then the direction of the direct current flowing through the coil is reversed, and the maximum current value is gradually set smaller each time the coil is reversed. Is done. The energization time may be set shorter for each inversion. The strength of the magnetic field generated in the coil by the direct current flowing through the coil is attenuated while the direction is reversed. Therefore, the magnetic moment of each magnetic domain of the core becomes random, and the strength of magnetization of the core becomes weak. Due to the demagnetization of the core, the waiting time until the mold opening starts is shortened. Slight magnetization remains in the core after demagnetization.

  In an injection molding machine, mold closing, mold clamping, and mold opening are repeatedly performed, and magnetizing and demagnetizing of the core of the electromagnet are repeatedly performed. From the start of mold opening to the completion of mold closing, current supply to the electromagnet coil is interrupted.

  Conventionally, the direction of the direct current in the magnetization process and the number of inversions in the direction of the direct current in the demagnetization process are the same each time, so that residual magnetization occurs in the same direction every time after demagnetization, and the residual magnetization gradually increases. Therefore, the maintenance work tool is attracted to the core, and the workability of the maintenance work is poor. The increase in remanent magnetization was also observed in members around the core (for example, the soft magnetic member).

  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 increase in a residual magnetization.

In order to solve the above problems, an injection molding machine according to an aspect of the present invention is provided.
In an injection molding machine equipped with an electromagnet that generates a clamping force,
A current supply for supplying a direct current to the coil of the electromagnet;
A control unit for controlling the current supply unit,
The control unit controls the step of magnetizing and demagnetizing the core of the electromagnet a predetermined number of times with the first current pattern, and then controls the step a predetermined number of times with the second current pattern,
The first current pattern and the second current pattern are characterized in that the direction of the direct current supplied to the coil last in the degaussing process is opposite.

  ADVANTAGE OF THE INVENTION According to this invention, the injection molding machine which can suppress the increase in a residual magnetization is provided.

It is a figure which shows the state at the time of mold closing of the injection molding machine by one Embodiment of this invention. It is a figure which shows the state at the time of the mold opening 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. It is a figure which shows the electric current pattern (1) of the electromagnet of the injection molding machine by one Embodiment. It is a figure which shows the electric current pattern (2) of the electromagnet of the injection molding machine by one Embodiment. It is a figure which shows the electric current pattern of the electromagnet of the conventional injection molding machine.

  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 a mold is closed in an injection molding machine according to an embodiment of the present invention. FIG. 2 is a view showing a state when the mold of the injection molding machine according to the embodiment of the present invention is opened.

  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.

  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 a direct 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 direct 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 direct 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 (die opening 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 controls the current supply unit 70 in the state of FIG. 1 (mold closed state) to supply a direct current to the coil 48 of the electromagnet 49. If it does so, a magnetic field will arise in the coil 48 with the direct 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 the mold-clamped state is filled with molten resin, cooled and solidified to form a molded product.

  Subsequently, the control unit 60 controls the current supply unit 70 to demagnetize the core 46 of the electromagnet 49. The demagnetization of the core 46 is performed by first supplying a direct current in the opposite direction to that at the time of magnetization to the coil 48 and then gradually reversing the direction of the direct current supplied to the coil 48 and gradually increasing the maximum current value at each inversion. This is done by setting it to a small value. The energization time may be set shorter for each inversion. The strength of the magnetic field generated in the coil 48 by the direct current flowing through the coil 48 is attenuated while the direction is reversed. Therefore, the magnetic moment of each magnetic domain of the core 46 becomes random, and the strength of magnetization of the core 46 becomes weak. Due to the demagnetization of the core 46, the waiting time until the mold opening starts is shortened. During the demagnetization process, the direction of the direct current is maintained in one direction and does not have to be reversed.

  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.

  In the injection molding machine 10, mold closing, mold clamping, and mold opening are repeatedly performed, and magnetization and demagnetization of the core 46 of the electromagnet 49 are repeatedly performed. From the start of mold opening to the completion of mold closing, the current supply to the coil 48 of the electromagnet 49 is interrupted.

  FIG. 4 is a diagram showing a current pattern (1) of an electromagnet of an injection molding machine according to an embodiment. In FIG. 4, the horizontal axis represents time, and the vertical axis represents the direction and current value of the direct current.

  The control unit 60 controls the process of magnetizing and demagnetizing the core 46 of the electromagnet 49 a predetermined number of times using the first current pattern P100, and then controls the above process a predetermined number of times using the second current pattern P200. For example, the control unit 60 changes the current pattern between the first current pattern P100 and the second current pattern P200 each time the above process is controlled once.

  In the first current pattern P100 and the second current pattern P200, the direction of the direct current that is finally supplied to the coil 48 in the degaussing process is opposite. Since the direction of the magnetic field finally generated by the coil 48 in the demagnetization process is reversed, the direction of the residual magnetization can be reversed, and an increase in the residual magnetization can be suppressed. Therefore, since the adsorption | suction to the core 46 of the tool for maintenance work is suppressed, the workability | operativity of a maintenance work improves. This effect is obtained not only for the core 46 but also for members around the core 46 (for example, the suction plate 22).

  Further, the first current pattern P100 and the second current pattern P200 are opposite in the direction of the direct current supplied to the coil 48 in the magnetization process. Since the magnetization direction of the core 46 is reversed, an increase in residual magnetization can be further suppressed. Note that the first current pattern P100 and the second current pattern P200 have the reverse direction of the direct current supplied to the coil 48 in the magnetizing process, so the direct current supplied to the coil 48 first in the demagnetizing process. The direction of is also reversed.

Further, 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 are: (1) the maximum current value I ₀ of the direct current in the magnetization step, (2) the energization time Δt ₀ of the direct current in the magnetization step, ( 3) Number of times the direction of the direct current is reversed in the demagnetization step, (4) Each energization time Δt _{1 to} Δt ₅ in which a forward or reverse direct current is passed in the demagnetization step, and (5) Each energization time Δt _{1 to} Δt maximum current value _I 1 ~I ₅ may be the same in the _5. The influence of magnetization and demagnetization by the first current pattern P100 is offset by the influence of magnetization and demagnetization by the second current pattern P200.

  In addition, about the 1st and 2nd current pattern P100, P200, during the degaussing process, the direction of the direct current is maintained in one direction and does not need to be reversed.

  FIG. 5 is a diagram showing a current pattern (2) of an electromagnet of an injection molding machine according to an embodiment. In FIG. 5, the horizontal axis represents time, and the vertical axis represents the direction of the direct current and the current value.

  The control unit 60 controls the process of magnetizing and demagnetizing the core 46 of the electromagnet 49 a predetermined number of times with the first current pattern P100, and then controls the above process with the second current pattern P201 a predetermined number of times. For example, the control unit 60 changes the current pattern between the first current pattern P100 and the second current pattern P201 every time the above process is controlled once.

  In the first current pattern P100 and the second current pattern P201, the direction of the direct current that is finally supplied to the coil 48 in the degaussing process is opposite. Since the direction of the magnetic field finally generated by the coil 48 in the demagnetization process is reversed, the direction of the residual magnetization can be reversed, and an increase in the residual magnetization can be suppressed. Therefore, since the adsorption | suction to the core 46 of the tool for maintenance work is suppressed, the workability | operativity of a maintenance work improves. This effect is obtained not only for the core 46 but also for members around the core 46 (for example, the suction plate 22).

  The second current pattern P201 has the same direction of the direct current supplied to the coil 48 in the magnetization process as the first current pattern P100, and the number of inversions of the direct current direction in the demagnetization process is one time. By increasing, the direction of the direct current supplied to the coil 48 last in the degaussing process is reversed. Note that the number of inversions in the direction of the direct current in the demagnetization process may be reduced by one, or may be increased or decreased by an odd number.

The second current pattern P201 is the same pattern as the first current pattern P100 from the start of the magnetization process to the middle of the demagnetization process. That is, the first current pattern P100 and the second current pattern P201 are: (1) the maximum current value I ₀ of the direct current in the magnetization step, (2) the energization time Δt ₀ of the direct current in the magnetization step, ( 3) each weld time flows forward or reverse DC current demagnetization step Δt ₁ ~Δt _5, and (4) become the maximum current value _I 1 ~I ₅ is the same at each weld time Δt ₁ ~Δt ₅ Yes.

  In addition, about any one of the 1st and 2nd electric current patterns P100 and P201, during the degaussing process, the direction of the direct current is maintained in one direction and does not need to be reversed.

  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 changed every time the process of magnetizing and demagnetizing the core 46 of the electromagnet 49 is controlled once. However, every time the process is controlled a plurality of times. You may go to Further, after performing the process M times (M is a natural number of 1 or more) with one current pattern, the process is performed N times (N is a natural number of 1 or more, where N ≠ M) with another current pattern. Further, after that, the process may be performed N times with the one current pattern, and then the process may be performed M times with the other current pattern. It should be noted that an increase in residual magnetization can be reliably suppressed by changing the current pattern each time the process is controlled once.

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)

In an injection molding machine equipped with an electromagnet that generates a clamping force,
A current supply for supplying a direct current to the coil of the electromagnet;
A control unit for controlling the current supply unit,
The control unit controls the step of magnetizing and demagnetizing the core of the electromagnet a predetermined number of times with the first current pattern, and then controls the step a predetermined number of times with the second current pattern,
An injection molding machine, wherein the first current pattern and the second current pattern are opposite in the direction of a direct current supplied to the coil last in the demagnetization step.   In the first current pattern and the second current pattern, the direction of the direct current supplied to the coil in the magnetizing process and the direction of the direct current supplied to the coil in the demagnetizing process are opposite to each other. The injection molding machine according to claim 1.   The injection molding machine according to claim 1 or 2, wherein the second current pattern is obtained by inverting the first current pattern.   Each time the control unit controls the process of magnetizing and demagnetizing the core of the electromagnet once, the control unit changes the current pattern of the current supplied to the coil of the electromagnet in the process with the first current pattern and the first current pattern. The injection molding machine as described in any one of Claims 1-3 changed between 2 electric current patterns.

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