JPWO2009028488A1 - Mold clamping apparatus and mold clamping control method - Google Patents

Abstract

A mold clamping device that applies a mold clamping force by an electromagnet, a first current command generating unit that generates a current command to the electromagnet according to a target mold clamping force, and detecting the mold clamping force by the electromagnet A mold clamping force detection unit; and a second current command generation unit configured to generate a correction command for correcting the current command based on a detection value of the mold clamping force detected by the mold clamping force detection unit. As described above, the mold clamping device capable of appropriately controlling the mold clamping force applied using the electromagnet is provided.

Description

  The present invention relates to a mold clamping device and a mold clamping control method.

  2. Description of the Related Art Conventionally, in an injection molding machine, resin is injected from an injection nozzle of an injection device, filled into a cavity space between a fixed mold and a movable mold, and solidified to obtain a molded product. ing. A mold clamping device is provided for moving the movable mold relative to the fixed mold to perform mold closing, mold clamping, and mold opening.

  The mold clamping device includes a hydraulic mold clamping device that is driven by supplying oil to a hydraulic cylinder, and an electric mold clamping device that is driven by an electric motor. It is widely used because it has high controllability, does not pollute the surroundings, and has high energy efficiency. In this case, by driving the electric motor, the ball screw is rotated to generate a thrust, and the thrust is expanded by a toggle mechanism to generate a large mold clamping force.

  However, since the electric mold clamping device having the above-described configuration uses a toggle mechanism, it is difficult to change the mold clamping force due to the characteristics of the toggle mechanism, and the responsiveness and stability are improved. The mold clamping force cannot be controlled during molding. Therefore, a mold clamping device is provided in which the thrust generated by the ball screw can be directly used as a mold clamping force. In this case, since the torque of the electric motor and the mold clamping force are proportional, the mold clamping force can be controlled during molding.

  However, in the conventional mold clamping device, the load resistance of the ball screw is low and a large mold clamping force cannot be generated, and the mold clamping force fluctuates due to torque ripple generated in the electric motor. In addition, in order to generate the mold clamping force, it is necessary to constantly supply current to the motor, and the power consumption and heat generation amount of the motor increase. Therefore, it is necessary to increase the rated output of the motor by that amount. The cost of the device becomes high.

  Therefore, a mold clamping device using a linear motor for the mold opening / closing operation and utilizing the attractive force of an electromagnet for the mold clamping operation can be considered (for example, Patent Document 1). In such a mold clamping device, feedback control is performed on the mold clamping force in order to keep the mold clamping force constant during the mold clamping process. Conventionally, a control unit that performs such feedback control is configured as follows, for example.

FIG. 1 is a diagram illustrating a configuration example of a conventional control unit. In FIG. 1, reference numeral 100 denotes a mold clamping device. A control unit 160 controls the mold clamping force of the mold clamping device 100. The control unit 160 includes an adder 161, an integrator 162, an amplifier 163, and the like. The adder 161 receives a mold clamping force command (a command indicating the magnitude of the target mold clamping force (target mold clamping force)) from a host controller (not shown), and the mold clamping force of the mold clamping device 100 is added. A detection value of the mold clamping force is input from the detector 155. The adder 161 calculates an error with respect to the target mold clamping force (mold clamping force error) based on the mold clamping force command value and the mold clamping force detection value, and outputs the error to the integrator 162. The integrator 162 calculates a current value that corrects the mold clamping force error by integrating the mold clamping force error, and outputs a current command indicating the current value to the amplifier 163. The amplifier 163 supplies a current having a current value indicated by the current command to the electromagnet 49. Thereafter, the mold clamping force detection value is sequentially input to the adder 161, and feedback control is performed.
JP-A-10-244567

  However, it is difficult to control the clamping force in a desired state simply by performing general feedback control in view of the characteristics of the electromagnet.

  FIG. 2 is a diagram for explaining a mold clamping force obtained by conventional feedback control. In FIG. 2, the horizontal axis indicates the passage of time, and the vertical axis indicates the detected value of the clamping force. A curve L0 indicates the mold clamping force obtained by the above-described feedback control as time elapses.

  Since the start of mold clamping, the slope of the curve L0 is very gentle. This is due to the poor rise response of the electromagnet. That is, even if a current having a certain current value is supplied to the electromagnet, if the distance between the gaps is large, the electromagnetic force is small, so that a force corresponding to the current value cannot be instantaneously applied. Therefore, it takes some time for the detected value of the mold clamping force to reach the target mold clamping force.

  Thus, there is a problem that the target mold clamping force cannot be obtained quickly by simple feedback control. If the time to reach the target mold clamping force becomes longer, the molding cycle becomes longer and the productivity is lowered.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a mold clamping device and a mold clamping control method capable of appropriately controlling the mold clamping force applied using an electromagnet.

  Accordingly, in order to solve the above-described problem, the present invention provides a mold clamping device that applies a mold clamping force with an electromagnet, and a first current command generation unit that generates a current command to the electromagnet according to a target mold clamping force. A mold clamping force detection unit for detecting the mold clamping force by the electromagnet, and a correction command for correcting the current command based on a detection value of the mold clamping force detected by the mold clamping force detection unit. And a second current command generation unit.

  Further, the present invention provides a correction to be supplied to the electromagnet based on the current command generated by the first current command generation unit and the correction command generated by the second current generation command unit. A correction current command calculation unit for calculating a current command is provided.

  In the present invention, the first current command generation unit generates a current command having a rising current command for generating the mold clamping force and a maintenance current command for maintaining the generated mold clamping force. It is characterized by.

  In the present invention, the second current command generation unit may detect an error between a mold clamping force maintained based on the maintenance current command and a detected value of the mold clamping force detected by the mold clamping force detection unit. Based on this, the correction command is generated.

  Further, the present invention is characterized in that the first current command generation unit generates a current command indicating a current value larger than a current corresponding to the target mold clamping force at the start of mold clamping.

  The second current command generation unit may generate the correction command based on an error between the target mold clamping force and the detected value of the mold clamping force.

  In addition, the present invention is characterized by having a switching unit that switches between operation and stop of the second current generation unit based on the detected value of the mold clamping force.

  In addition, according to the present invention, when the switching unit is controlled based on the maintenance current command among the current commands generated by the first current command generation unit, the second current command generation unit is activated and stopped. It is characterized by switching.

  Further, the present invention is characterized in that the switching unit operates the second current command generation unit while the target mold clamping force is to be maintained.

  Further, the present invention is characterized in that the switching unit stops the second current command unit for a predetermined period from the start of mold clamping.

  Further, the present invention is characterized in that the switching unit stops the second current command unit for a predetermined period from the start of the change of the target mold clamping force.

  In the invention, it is preferable that the switching unit stops the second current command unit when the target clamping force is zero.

  ADVANTAGE OF THE INVENTION According to this invention, the mold clamping apparatus and mold clamping control method which can control appropriately the mold clamping force made to act using an electromagnet can be provided.

It is a figure which shows the structural example of the conventional control part. It is a figure for demonstrating the mold clamping force obtained by the conventional feedback control. It is a figure which shows the state at the time of the mold closing of the metal mold apparatus and mold clamping apparatus in embodiment of this invention. It is a figure which shows the state at the time of the mold opening of the metal mold | die apparatus and mold clamping apparatus in embodiment of this invention. It is a figure which shows the structural example of the control part in 1st embodiment. It is a figure for demonstrating the current pattern produced | generated by the current pattern generator. It is a figure for demonstrating control of the mold clamping force by the control part in 1st embodiment. It is a figure which shows the structural example of the control part in 2nd embodiment. It is a figure for demonstrating control of the mold clamping force by the control part in 2nd embodiment. It is a figure which shows the modification of this application which applied the rotary motor which closed the generation | occurrence | production area | region of the magnetic field with the motor frame.

Explanation of symbols

10 Mold Clamping Device 11 Fixed Platen 12 Movable Platen 12a Movable Platen Flange 13 Rear Platen 14 Tie Bar 15 Fixed Mold 16 Movable Mold 17 Injection Device 18 Injection Nozzle 19 Mold Device 21 Guide Post 22 Adsorption Plate 23 Guide Hole 24 Large Diameter Portion 25 Small-diameter portion 28 Linear motor 29 Stator 31 Mover 37 Electromagnet unit 39 Rod 41, 42 Hole 43 Screw 44 Nut 45 Coil placement portion 46 Core 47 Yoke 48 Coil 49 Electromagnet 51 Adsorption portion 55 Mold clamping force detector 71 Ball screw Nut 72 Ball screw shaft 73 Motor support 74 Mold opening / closing motor 75 Position detector 601 Host controller 602 Current pattern generator 603 Integrator 604 Amplifier 605, 606 Adder 607 Changeover monitor Br1 Bearing member Gd Guide Fr Frame n1, n2 N The

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this embodiment, for the mold clamping device, the moving direction of the movable platen when closing the mold is the front, the moving direction of the movable platen when opening the mold is the rear, and the injection device is the injection The description will be made assuming that the moving direction of the screw when performing the measurement is the front and the moving direction of the screw when performing the measurement is the rear.

  FIG. 3 is a view showing a state of the mold device and the mold clamping device when the mold is closed in the embodiment of the present invention, and FIG. 4 is a state when the mold device and the mold clamping device of the embodiment of the present invention are opened. FIG.

  In the figure, 10 is a mold clamping device, Fr is a frame of an injection molding machine, Gd is laid on the frame Fr to form a rail, and supports the mold clamping device 10 as a first guide member for guiding it. The two guides (in the figure, only one of the two guides Gd is shown) 11 is placed on the guide Gd and fixed to the frame Fr and the guide Gd. A fixed platen as a first fixing member, and a rear platen 13 as a second fixing member is disposed at a predetermined distance from the fixed platen 11 and opposed to the fixed platen 11, and the fixed platen A tie bar 14 (only two of the four tie bars 14 are shown in the figure) is laid between 11 and the rear platen 13 as four connecting members. The rear platen 13 is placed on the guide Gd so that it can move slightly with respect to the guide Gd as the tie bar 14 expands and contracts.

  In the present embodiment, the fixed platen 11 is fixed to the frame Fr and the guide Gd, and the rear platen 13 can move slightly with respect to the guide Gd. The fixed platen 11 can be moved slightly with respect to the guide Gd by being fixed with respect to the Fr and the guide Gd.

  A movable platen 12 as a first movable member is disposed along the tie bar 14 so as to face the fixed platen 11 so as to be movable back and forth in the mold opening / closing direction. For this purpose, 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.

  A first screw portion (not shown) is formed at the front end portion of the tie bar 14, and the tie bar 14 is fixed to the fixed platen 11 by screwing the first screw portion and the nut n1. Further, a guide post 21 as a second guide member having an outer diameter smaller than that of the tie bar 14 is protruded rearward from the rear end surface of the rear platen 13 at a predetermined portion at the rear of each tie bar 14, and It is formed integrally with the tie bar 14. A second screw portion (not shown) is formed in the vicinity of the rear end surface of the rear platen 13, and the fixed platen 11 and the rear platen 13 are connected by screwing the second screw portion and the nut n2. The In the present embodiment, the guide post 21 is formed integrally with the tie bar 14, but the guide post 21 may be formed separately from the tie bar 14.

  A fixed mold 15 as a first mold is fixed to the fixed platen 11, and a movable mold 16 as a second mold is fixed to the movable platen 12. Accordingly, the fixed mold 15 and the movable mold 16 are brought into contact with and separated from each other, and mold closing, mold clamping, and mold opening are performed. As the mold clamping is performed, a plurality of cavity spaces (not shown) are formed between the fixed mold 15 and the movable mold 16, and the molding material injected from the injection nozzle 18 of the injection apparatus 17 is used as a molding material. Resin (not shown) is filled in each cavity space. A mold device 19 is configured by the fixed mold 15 and the movable mold 16.

  A suction plate 22 as a second movable member disposed in parallel with the movable platen 12 is disposed behind the rear platen 13 so as to be able to advance and retract along the guide posts 21 and is guided by the guide posts 21. Is done. The suction plate 22 is formed with guide holes 23 through the guide posts 21 at locations corresponding to the guide posts 21. The guide hole 23 is opened at the front end surface, and has a large diameter portion 24 that accommodates the ball nut n2 and a sliding surface that is opened at the rear end surface of the suction plate 22 and is slid with the guide post 21. A small diameter portion 25 is provided. In the present embodiment, the suction plate 22 is guided by the guide post 21, but the suction plate 22 can be guided not only by the guide post 21 but also by the guide Gd.

  By the way, in order to move the movable platen 12 forward and backward, a linear motor 28 as a first drive unit and as a mold opening / closing drive unit is disposed between the movable platen 12 and the frame Fr. The linear motor 28 includes a stator 29 as a first drive element and a mover 31 as a second drive element. The stator 29 is parallel to the guide Gd on the frame Fr. In addition, the movable platen 12 is formed corresponding to the moving range of the movable platen 12, and the movable element 31 is formed at a lower end of the movable platen 12 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 are protruded toward the stator 29 and formed at a predetermined pitch, and the coil 35 is wound around the magnetic pole teeth 33. The magnetic pole teeth 33 are formed in parallel to each other in a direction perpendicular to the moving direction of the movable platen 12. The stator 29 includes a core (not shown) and a permanent magnet (not shown) formed to extend on the core. The permanent magnet is formed by magnetizing the N-pole and S-pole magnetic poles alternately and at the same pitch as the magnetic pole teeth 33.

  Accordingly, when the linear motor 28 is driven by supplying a predetermined current to the coil 35, the movable element 31 is advanced and retracted, and accordingly, the movable platen 12 is advanced and retracted to perform mold closing and mold opening. it can.

  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 is disposed on the stator and the permanent magnet is disposed on the mover. You can also. 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.

  By the way, when the movable platen 12 is moved forward and the movable mold 16 abuts against the fixed mold 15, the mold is closed and subsequently the mold is clamped. In order to perform mold clamping, an electromagnet unit 37 is disposed between the rear platen 13 and the suction plate 22 as a second driving unit and as a mold clamping driving unit. A rod 39 as a clamping force transmission member that extends through the rear platen 13 and the suction plate 22 and connects the movable platen 12 and the suction plate 22 is disposed so as to freely advance and retract. The rod 39 advances and retracts the suction plate 22 in conjunction with the advance and retreat of the movable platen 12 when the mold is closed and opened, and transmits the mold clamping force generated by the electromagnet unit 37 to the movable platen 12 during mold clamping. To do.

  The mold clamping device 10 is configured by the fixed platen 11, the movable platen 12, the rear platen 13, the suction plate 22, the linear motor 28, the electromagnet unit 37, the rod 39, and the like.

  In the mold clamping apparatus 10, the operation of the linear motor 28 as a mold opening / closing drive unit and the operation of the electromagnet unit 37 as a mold clamping drive unit are controlled by a control unit 60. Details of the control unit 60 will be described later.

  The electromagnet unit 37 includes an electromagnet 49 as a first driving member formed on the rear platen 13 side, and an attracting portion 51 as a second driving member formed on the attracting plate 22 side. A predetermined portion of the front end surface of the attracting plate 22, in the present embodiment, is formed in a portion that surrounds the rod 39 and faces the electromagnet 49 in the attracting plate 22. In addition, in the present embodiment, two grooves 45 as coil arrangement portions having a rectangular cross-sectional shape are parallel to each other at a predetermined portion of the rear end surface of the rear platen 13, slightly above and below the rod 39. A core 46 having a rectangular shape is formed between the grooves 45, and a yoke 47 is formed in another portion. A coil 48 is wound around the core 46.

  In addition, although the said core 46 and the yoke 47 are comprised by the integral structure of a casting, they may be formed by laminating | stacking the thin plate which consists of a ferromagnetic material, and may comprise an electromagnetic laminated steel plate.

  In the present embodiment, the electromagnet 49 is formed separately from the rear platen 13, and the attracting portion 51 is formed separately from the attracting plate 22. The electromagnet is formed as a part of the rear platen 13, and the attracting portion is formed as a part of the attracting plate 22. It can also be formed.

  Therefore, in the electromagnet unit 37, when a current (DC current) is supplied to the coil 48, the electromagnet 49 is driven to attract the attracting portion 51 and generate the mold clamping force.

  The rod 39 is connected to the suction plate 22 at the rear end and is connected to the movable platen 12 at the front end. Therefore, the rod 39 is moved forward as the movable platen 12 moves forward when the mold is closed to advance the suction plate 22, and is moved backward as the movable platen 12 is moved backward when the mold is opened. Retreat.

  For this purpose, a hole 41 for penetrating the rod 39 and a hole 42 for penetrating the rod 39 are formed in the central portion of the rear platen 13 and the central portion of the suction plate 22. A bearing member Br1 such as a bush that slidably supports the rod 39 is provided facing the opening. Further, a screw 43 is formed at the rear end of the rod 39, and the screw 43 and a nut 44 as a mold thickness adjusting mechanism supported rotatably on the suction plate 22 are screwed together.

  A large-diameter gear (not shown) is formed on the outer peripheral surface of the nut 44, and a mold thickness adjusting motor (not shown) serving as a mold thickness adjusting drive unit is disposed on the suction plate 22. A small-diameter gear attached to the output shaft is engaged with a gear formed on the outer peripheral surface of the nut 44.

  Then, when the mold thickness adjusting motor is driven according to the thickness of the mold device 19 and the nut 44 is rotated by a predetermined amount with respect to the screw 43, the position of the rod 39 with respect to the suction plate 22 is adjusted, The position of the suction plate 22 with respect to the fixed platen 11 and the movable platen 12 is adjusted, and the gap δ can be set to an optimum value. That is, the mold thickness is adjusted by changing the relative positions of the movable platen 12 and the suction plate 22.

  In the present embodiment, the core 46, the yoke 47, and the suction plate 22 are all made of an electromagnetic laminated steel plate, but the periphery of the core 46 and the suction portion 51 in the rear platen 13 are electromagnetic laminated. You may make it comprise with a steel plate. In the present embodiment, an electromagnet 49 is formed on the rear end surface of the rear platen 13, and the attracting portion 51 is disposed on the front end surface of the attracting plate 22 so as to be capable of moving forward and backward. However, it is possible to dispose the electromagnet on the front end surface of the suction plate 22 so as to be able to advance and retreat, with the suction portion opposed to the suction portion on the rear end surface of the rear platen 13.

Next, details of the control unit 60 will be described. FIG. 5 is a diagram illustrating a configuration example of a control unit in the first embodiment. In the first embodiment, the control unit 60 will be described as the control unit 60a. The control unit 60a includes a host controller 601, a current pattern generator 602, an integrator 603, an amplifier 604, adders 605 and 606, etc. The host controller 601 includes a CPU, a memory, and the like, and is recorded in the memory. The processing of the linear motor 28 and the electromagnet 49 is controlled by processing the program by the CPU. The host controller 601 outputs a command indicating the magnitude of the mold clamping force (mold clamping force command) and a command indicating the position to which the linear motor 28 should move (position command). In the present embodiment, a detailed description of the control of the linear motor 28 is omitted for convenience. Accordingly, the components for controlling the linear motor 28 are also omitted in the figure.

  A mold clamping force command from the host controller 601 is input to the current pattern generator 602. The current pattern generator 602 is constituted by a servo card, for example, and generates a current pattern corresponding to the mold clamping force indicated in the mold clamping force command. Here, the current pattern refers to information indicating time-series current values supplied to the electromagnet 49 (coil 48). The current pattern generator 602 sequentially outputs a signal (current command) indicating a current value supplied to the electromagnet 49 to the adder 606 according to the passage of time in accordance with the generated current pattern.

  The mold clamping force command from the host controller 601 is also input to the adder 605. The adder 605 also receives a detection value (actual value) of the mold clamping force detected by the mold clamping force detector 55 installed in the mold clamping apparatus 10. The adder 605 calculates an error of the actual value (clamping force error) with respect to the mold clamping force command based on the value of the mold clamping force (clamping force command value) and the mold clamping force detection value indicated in the mold clamping force command. calculate. The calculated mold clamping force error is input to the integrator 603. The mold clamping force detector 55 detects a magnetic flux between the sensor for detecting the extension amount of the tie bar 14 or a load detector such as a load cell disposed on the rod 39 or the electromagnet 49 and the attracting portion 51. You may comprise by a sensor.

  The integrator 603 calculates a correction value for the current command by integrating the mold clamping force error in order to eliminate the mold clamping force error, and sequentially outputs a signal (correction command) indicating the correction value to the adder 606. .

  An adder 606 as a correction current command unit converts a current value (current command value) indicated in the current command input from the current pattern generator 602 into a current value (correction) indicated in the correction command input from the integrator 603. (Command value), and a signal (corrected current command) indicating the corrected current value is sequentially output to the amplifier 604.

  The amplifier 604 is constituted by, for example, a driver card, and supplies a current corresponding to the correction current command input from the adder 606 to the electromagnet 49. The electromagnet 49 is driven in response to the supply of the current.

  In the present embodiment, a first current command generation unit 610 is configured by the current pattern generator 602, and a second current command generation unit 620 is configured by the adder 605 and the integrator 603.

  Next, the operation of the mold clamping apparatus 10 having the above configuration will be described.

  The control unit 60 performs a mold opening / closing process, and supplies current to the coil 35 in the state shown in FIG. 4 when the mold is closed. Subsequently, the linear motor 28 is driven, the movable platen 12 is advanced, and the movable mold 16 is brought into contact with the fixed mold 15 as shown in FIG. At this time, an optimum gap δ 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.

  When the movable platen 12 reaches a predetermined position (a position where the movable mold 16 is brought into contact with the fixed mold 15 or a position just before the contact is made), the mold clamping process is started. That is, the host controller 61 outputs a mold clamping force command indicating a preset target value of the mold clamping force (target mold clamping force) to the current pattern generator 602 and the adder 605. The current pattern generator 602 generates a current pattern according to the mold clamping force command, and outputs the current command according to the passage of time according to the current pattern. Here, the current pattern is generated so that the rising response of the clamping force by the electromagnet 49 is improved.

  FIG. 6 is a diagram for explaining a current pattern generated by the current pattern generator. In FIG. 6A, the current pattern L1 is indicated by a dotted broken line. The vertical axis of (A) shows the current value, and the horizontal axis shows the passage of time. On the other hand, in (B), the transition of the mold clamping force obtained when the current value corresponding to the current pattern is supplied to the coil 48 as it is is shown by a curve L2. The vertical axis of (B) shows the mold clamping force, and the horizontal axis shows the passage of time. Note that the passage of time on the horizontal axis of (A) and the horizontal axis of (B) coincide.

  As shown in the figure, the current pattern L1 includes a rising current command for generating a mold clamping force for a predetermined period (t1 to t2) from the start of mold clamping, and thereafter, the mold clamping force is maintained (after t2). Includes maintenance current command. In the rising current command, a current exceeding the current value (rated current) corresponding to the target clamping force, for example, the maximum current (the maximum current value that can be properly supplied by the control unit 60a) is the current command value. It is said that. In the maintenance current command, the rated current is the current command value. Based on such a current pattern, a current that greatly exceeds the rated current is supplied to the coil 48 during the period from t1 to t2. As a result, the slope of the portion (period t1 to t2) indicated by the symbol a in the curve L2 in FIG. That is, the rising response of the electromagnet 49 is improved. As described above, the current pattern generator 601 generates a current pattern that can improve the rising response of the electromagnet 49.

  However, the clamping force obtained by the electromagnet 49 is the same current value due to the influence of hysteresis of the electromagnet 49, the error of the gap δ between the electromagnet 49 and the attracting part 51, the error due to deformation of the resin, and the like. The same size is not always obtained. Therefore, even if the rated current is supplied, the target mold clamping force is not always obtained. As shown in FIG. 5B, the mold clamping force error e is between the target mold clamping force and the actual value. Can occur.

  Therefore, in order to prevent the mold clamping force error e from occurring, the control unit 60a does not supply the current based on the current pattern to the coil 48 as it is, but uses a correction command based on the detection value of the mold clamping force detector 55. The supply current to the coil 48 is corrected by performing control based on the control.

  That is, the adder 605 calculates a mold clamping force error based on the mold clamping force command value and the mold clamping force detection value sequentially input from the mold clamping force detector 55, and outputs it to the integrator 603. The integrator 603 calculates a correction value for the current supplied to the electromagnet 49 in order to eliminate the mold clamping force error by integrating the mold clamping force error from the start of mold clamping, and issues a correction command indicating the correction value. The result is output to the adder 606.

The adder 606 corrects the current value indicated in the current command input from the current pattern generator 602 with the current value indicated in the correction command input from the integrator 603, and a signal ( Correction current command) is output to the amplifier 604. The amplifier 604 supplies a current corresponding to the correction current command input from the adder 606 to the coil 48 of the electromagnet 49. When the current is supplied to the coil 48, the electromagnet 49 is driven, and the attracting unit 51 is connected to the electromagnet 49. Adsorbed by the adsorption force. Along with this, the clamping force is transmitted to the movable platen 12 via the suction plate 22 and the rod 39, and clamping is performed.

  During mold clamping, the mold clamping force is controlled as follows by the control based on the current pattern by the control unit 60a and the control based on the correction command based on the detection value of the mold clamping force detector 55.

  FIG. 7 is a diagram for explaining control of the mold clamping force by the control unit in the first embodiment. In FIG. 7, the same parts as those in FIG.

  In FIG. 6A, a curve L3 shows a transition of the current value of the current actually supplied from the amplifier 604 to the coil 48 based on the correction current command (current value of the correction current command). In FIG. 5B, a curve L4 indicates a clamping force detected as a result of supplying the current indicated by the curve L3 to the coil 48.

  As indicated by the curve L3, the controller 60a supplies the maximum current for a predetermined period (t1 to t3) from the start of mold clamping. This is a result of control based on the rising current command of the current pattern L1. By supplying the maximum current for a while from the start of mold clamping, the rising response of the electromagnet 49 is improved, and the mold clamping force increases rapidly (the part indicated by the symbol a in the curve L4).

  In the first embodiment, the integrator 603 of the control unit 60a starts integrating the mold clamping force error from the time of mold clamping start. That is, in the first embodiment, the control based on the correction command based on the value detected by the mold clamping force detector 55 based on the rising current command is started from the start of mold clamping.

  By the way, as indicated by the curve L3, the controller 60a supplies the maximum current for a longer period (t1 to t3) than the period (t1 to t2) specified in the current pattern L1. This is because the mold clamping force has not reached the target mold clamping force at time t2, and the corresponding mold clamping force error is integrated by the control based on the correction command based on the detection value of the mold clamping force detector 55. This is because the current command based on the current pattern L1 is corrected by the correction command from the integrator 603. Therefore, the maximum current is supplied until t3 when the target mold clamping force is obtained.

  When the target mold clamping force is obtained, the control unit 60a attempts to reduce the supply current to the rated current in accordance with the maintenance current command of the current pattern L1. However, the response of the electromagnet 49 is not good not only at the time of rising but also in the opposite direction (at the time of falling). As shown, the clamping force continues to increase. The resulting mold clamping force error is also controlled based on a correction command based on the detection value of the mold clamping force detector 55, and the integrator 603 integrates the mold clamping force error and outputs a correction command. . As a result, in the adder 606, the sustain current command from the current pattern generator 602 is corrected by the correction command, and a current having a current value lower than the rated current is supplied to the coil 48 as indicated by the symbol c in the curve L3. Is done. The mold clamping force starts to decrease with a drop in the supply current and approaches the target mold clamping force.

  Thereafter, for example, as shown in FIG. 6B, when the target mold clamping force cannot be obtained with the rated current, the integrator 603 outputs a correction command by integrating the mold clamping error e. As the maintenance current command is corrected by the correction command, a current larger than the rated current is supplied to the coil 48 as indicated by the symbol d in the curve L3. As a result, in the drawing, the target clamping force is reached at t4 and a steady state is reached. Even after the steady state is reached, the mold clamping force detection value detected by the mold clamping force detector 55 is sequentially input to the adder 605 during the mold clamping hold, and based on the detection value of the mold clamping force detector 55. The current supplied to the coil 48 is adjusted by the control based on the correction command. As a result, clamping is performed with a stable clamping force.

  During this time, the resin melted in the injection device 17 is injected from the injection nozzle 18 and filled in each cavity space of the mold device 19. As the load detector, a load cell disposed on the rod 39, a sensor for detecting the extension amount of the tie bar 14, or the like can be used.

  When the resin in each cavity space is cooled and solidified, the controller 60a stops supplying current to the coil 48 in the state of FIG. 3 when the mold is opened. Along with this, the linear motor 28 is driven, the movable platen 12 is retracted, and the movable mold 16 is placed at the retract limit position as shown in FIG. 4, and the mold opening is performed.

  As described above, according to the mold clamping device having the control unit 60a in the first embodiment, the current pattern generator 602 generates a current pattern considering the characteristics of the electromagnet, and the mold is based on the current pattern. Control is performed on the clamping force. Therefore, the rising response of the mold clamping force can be improved, and the molding cycle can be shortened. Further, since the integrator 603, the adder 605, the adder 606, and the like perform control based on the correction command based on the detection value of the mold clamping force detector 55 with respect to the mold clamping force, the target mold clamping force is appropriately maintained. can do.

  Next, a second embodiment will be described. In the controller 60a of the first embodiment, as shown in FIG. 7B, a phenomenon that the mold clamping force exceeds the target mold clamping force during the period from t3 to t4 (that is, the mold clamping force is exceeded). Shoot) has occurred. Overshorting of the mold clamping force is not preferable from the viewpoint of mold protection and prevention of defective molding. Therefore, in the second embodiment, an example in which such a problem is solved will be described.

  FIG. 8 is a diagram illustrating a configuration example of a control unit in the second embodiment. In FIG. 8, the same parts as those in FIG. In the second embodiment, the control unit 60 will be described as the control unit 60b.

  The control unit 60b includes a switching monitor 607 as a component in addition to the components of the control unit 60a. The switching monitor 607 switches ON / OFF of the integrator 603, that is, the switching monitor 607 receives the mold clamping force command value input from the host controller 601 and the mold clamping force input from the mold clamping force detector 55. Based on the detected value, the integrator 603 is activated at an appropriate timing and stopped at an appropriate timing. The fact that the integrator 603 is activated means that the control based on the correction command based on the detection value of the mold clamping force detector 55 is activated. Further, the stop of the integrator 603 means that the control based on the correction command based on the detection value of the mold clamping force detector 55 is stopped.

  Hereinafter, control of the mold clamping force by the integrator 60b including the switching monitor 607 will be described. FIG. 9 is a diagram for explaining control of the mold clamping force by the control unit in the second embodiment. 9, parts that are the same as the parts shown in FIG. 7 are given the same reference numerals, and explanation thereof is omitted as appropriate.

  In the second embodiment, the switching monitor 607 stops the integrator 603 by outputting a stop command to the integrator 603 at the beginning of mold clamping. Accordingly, in the figure, the clamping force error is not integrated by the integrator 603 between t1 and t5, and the current command value is corrected based on the rising current command from the current pattern generator 602 by the adder 606. I will not. As a result, as shown in FIG. 5A, a current as shown in the current pattern L1 is supplied to the coil 48 between t1 and t5. In (A), between t1 and t5, the locus of the curve L3 coincides with the current pattern L1, but the solid line indicating the curve L3 is described in consideration of the visibility of the broken line indicating the current pattern L1. Absent.

  Here, the operation of the integrator 603 is stopped until the mold clamping force starts to stabilize. The integration of the mold clamping force error is performed from the beginning of mold clamping. It is because it is mentioned as one of the causes of overshoot. That is, in FIG. 7B, in order to correct the mold clamping force error integrated between t1 and t2, the period for supplying the maximum current is extended, and as a result, when the mold clamping force reaches the target mold clamping force. This is because overshoot occurs after t3. Therefore, in the second embodiment, the switching monitor 607 stops the operation of the integrator 603 during a period (t1 to t5) when the clamping force is unstable after the clamping is started.

  When the clamping force starts to stabilize based on the maintenance current command (t5), the switching monitor 607 outputs an operation command to the integrator 603. The switching monitor 607 detects the stability of the mold magnetic force by monitoring the displacement corresponding to the time of the mold clamping force detection value input from the mold clamping force detector 55. For example, the switching monitor 607 determines that the mold clamping force is stable if the displacement of the mold clamping force detection value is within a predetermined value within a predetermined time.

  The integrator 603 starts the operation (that is, integration of the mold clamping force error) in response to the operation command. In the example of FIG. 9B, the detected value of the mold clamping force based on the maintenance current command at the integration start time t5 is less than the target mold clamping force. Therefore, the integrator 603 outputs a correction command for correcting such a mold clamping force error to the adder 606. The adder 606 corrects the current command value based on the sustain current command from the current pattern generator 602 with the correction command value. As a result, as indicated by the curve L3, the supply current has a value exceeding the rated current. As the supply current increases, the mold clamping force also increases. In FIG. 5B, the target mold clamping force is reached at t6. In the second embodiment, since the mold clamping force error integration is started after the mold clamping force starts to stabilize based on the maintenance current command, the current command value is not rapidly corrected, and the mold clamping is not performed. The possibility of force overshoot is reduced. Therefore, when the target mold clamping force is reached at t6, the steady state is reached as it is. Even after the steady state is reached, the switching monitor 607 operates the integrator 603 while the mold clamping is being held (a period during which the target mold clamping force is to be maintained). Therefore, the current supplied to the coil 48 is adjusted by the control based on the correction command based on the detection value of the mold clamping force detector 55 based on the mold clamping force detection value input to the mold clamping force detector 55. As a result, clamping is performed with a stable clamping force.

  Although omitted in the figure, the clamping force command for reducing the clamping force during the clamping process (that is, a clamping force command indicating a clamping force lower than the current clamping force) is higher. When input from the controller, the switching monitor 607 outputs a stop command to the integrator 603 to stop the integrator 603. Therefore, in this case, a current according to the current pattern generated by the current pattern generator 602 according to the mold clamping force command is supplied to the coil 48 as it is. As a result, the mold clamping force starts to decrease and stabilizes near the mold clamping force indicated by the mold clamping force command. When the clamping force starts to stabilize, the switching monitor 607 activates the integrator 603. Thus, by not integrating the mold clamping force error during the period in which the mold clamping force rapidly decreases, it is possible to prevent the mold clamping force from being reduced more than necessary.

  When the mold clamping process is completed and the mold clamping force indicated by the mold clamping force command from the host controller 601 becomes zero, the switching monitor 607 stops the integrator 603. Thereby, the mold clamping force is increased by the control based on the correction command based on the detected value of the mold clamping force detector 55, even though the current value of the current command output from the current pattern generator 602 is zero. Can be prevented. That is, if the integrator 603 is operated, a correction command is output from the integrator 603 by integrating the mold clamping force error, and a current having a current value indicated by the correction command is supplied to the coil 48. is there. When the current is supplied to the coil 48, the mold clamping force error is further increased, and a correction command having a larger absolute value is output from the integrator 603 to correct the mold clamping force error. This is because a loop in which a current having a large absolute value is supplied to the coil 48 is formed. Since the magnitude of the force is proportional to the square of the current value, even if the current value of the correction command is negative, it does not work in the direction of decreasing the mold clamping force.

  As described above, according to the control unit 60b in the second embodiment, the changeover monitor 607 causes the mold clamping force detector 55 to operate in a period when the mold clamping force is unstable (when rising, falling, etc.). Control based on the correction command based on the detected value is stopped. Therefore, the possibility that the mold clamping force will overshoot can be reduced. As a result, the time to reach the target clamping force can be further shortened compared to the first embodiment, and the molding cycle can be shortened.

  In the present embodiment, since it is desirable to use the mold clamping force detector 55 that detects the load applied to the mold as the mold clamping force detector, the example using the mold clamping force detector 55 has been shown. However, a magnetic flux density detector that detects the magnetic flux density of the electromagnet may be used as the mold clamping force detection unit, or a distance detector that measures the gap δ between the rear platen 13 and the suction plate 22 may be used. Good.

  By the way, the mold clamping apparatus control method in the present embodiment may not be a mold clamping apparatus that performs the mold opening / closing operation by driving the linear motor 28. In particular, in the case of the linear motor 28, there is a possibility that dust or the like adheres because the magnet is exposed on the surface of the frame. For this reason, the modification of this application which applied the rotary type motor which closed the magnetic field generation | occurrence | production area with the motor frame, without using the linear motor 28 as a type | mold opening / closing drive part is shown in FIG.

  The description of the electromagnet unit as the second drive unit is the same as in FIGS. A mold opening / closing motor 74 as a first driving section and as a mold opening / closing driving section (mold opening / closing driving section) is attached to a motor support 73 fixed to the frame so as not to move. Here, as the mold opening / closing motor 74, a rotary motor in which a magnetic field generation region is closed by a motor frame is applied. A motor shaft (not shown) projects from the rotary motor, and the motor shaft is connected to the ball screw shaft 72. The ball screw shaft 72 is engaged with the ball screw nut 71 to constitute a motion direction conversion device that converts the rotational motion generated by the rotary motor into a straight motion. The ball screw nut 71 is non-rotatably disposed on the movable platen flange portion 12 a protruding from the lower portion of the movable platen 12. Thereby, when the mold opening / closing motor 74 rotates, the movable platen 12 moves back and forth, and the mold opening / closing operation of the movable mold 16 can be performed.

  Further, a position detector 75 is attached to the rear end of the mold opening / closing motor 74, and the position of the movable platen 12 can be grasped by reading the rotation angle of the mold opening / closing motor 74. As a result, the mold opening / closing processor 61 controls the mold opening / closing motor 74.

  In this configuration, when the mold clamping force is being applied to the mold apparatus 19 by the electromagnet, more specifically, after the start of pressure increase, the mold opening / closing processing unit 61 is eliminated when there is no risk of occurrence of the mold displacement. Variably controls the supply of current to the mold opening / closing motor 74. Specifically, the supply of current is stopped. Thereby, the influence on the mold clamping force due to the position control of the mold opening / closing motor 74 is eliminated.

  As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to such specific embodiment, In the range of the summary of this invention described in the claim, various deformation | transformation・ Change is possible.

  This international application claims priority based on Japanese Patent Application No. 2007-221573 filed on Aug. 28, 2007, the entire contents of which are incorporated herein by reference.

Claims (14)

A mold clamping device that applies a clamping force by an electromagnet,
A first current command generation unit that generates a current command to the electromagnet according to a target clamping force;
A mold clamping force detection unit for detecting the mold clamping force by the electromagnet;
A mold clamping device comprising: a second current command generation unit configured to generate a correction command for correcting the current command based on a detection value of the mold clamping force detected by the mold clamping force detection unit.   Correction for calculating a correction current command to be supplied to the electromagnet based on the current command generated by the first current command generation unit and the correction command generated by the second current generation command unit The mold clamping apparatus according to claim 1, further comprising a current command calculation unit.   The first current command generation unit generates a current command having a rising current command for generating the mold clamping force and a maintenance current command for maintaining the generated mold clamping force. The mold clamping apparatus according to 1.   The second current command generation unit outputs the correction command based on an error between a mold clamping force maintained based on the maintenance current command and a detected value of the mold clamping force detected by the mold clamping force detection unit. The mold clamping device according to claim 3, wherein the mold clamping device is generated.   2. The mold clamping device according to claim 1, wherein the first current command generation unit generates a current command indicating a current value larger than a current corresponding to the target mold clamping force at the start of mold clamping.   The mold clamping device according to claim 1, wherein the second current command generation unit generates the correction command based on an error between the target mold clamping force and a detected value of the mold clamping force.   The mold clamping device according to claim 1, further comprising a switching unit that switches operation and stop of the second current generation unit based on a detected value of the mold clamping force.   The switching unit switches between operation and stop of the second current command generation unit when controlled based on a maintenance current command among the current commands generated by the first current command generation unit. The mold clamping device according to claim 7.   The mold clamping device according to claim 1, wherein the switching unit operates the second current command generation unit while the target mold clamping force is to be maintained.   2. The mold clamping device according to claim 1, wherein the switching unit stops the second current command unit for a predetermined period from the start of mold clamping.   2. The mold clamping device according to claim 1, wherein the switching unit stops the second current command unit for a predetermined period from the start of the change of the target mold clamping force.   2. The mold clamping apparatus according to claim 1, wherein the switching unit stops the second current command unit when the target mold clamping force is zero. A mold clamping control method in which a clamping force is applied by an electromagnet,
Generate a current command to the electromagnet according to the target clamping force,
Detecting the clamping force by the electromagnet;
A mold clamping control method, comprising: generating a correction command for correcting the current command based on the detected value of the mold clamping force.   The mold clamping control method according to claim 13, wherein a correction current command supplied to the electromagnet is calculated based on the current command and the correction command.

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