JP5778023B2 - Injection molding machine - Google Patents

Description

  The present invention relates to an injection molding machine.

  An injection molding machine molds a molded product by filling molten resin in a cavity space of a mold apparatus and solidifying the resin (for example, see Patent Document 1). 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.

  The mold clamping device is detected by a mold clamping drive unit (for example, an electromagnet, a motor, or a fluid pressure cylinder) that generates a mold clamping force, a mold clamping force detection unit that detects a mold clamping force, and a mold clamping force detection unit. A mold clamping processing unit that controls the operation of the mold clamping drive unit based on the difference between the detected value of the mold clamping force and the target value of the mold clamping force.

WO05 / 090052 pamphlet

  FIG. 5 is a graph showing changes over time in the target value and the detected value of the clamping force in the conventional clamping process. In FIG. 5, the solid line shows the change over time of the target value of the mold clamping force, and the two-dot chain line shows the change over time of the detected value of the mold clamping force.

  At the time of mold clamping start (time t0), the target value of the mold clamping force is discontinuously changed from 0 (zero) to the set value S0. Thereafter, the target value of the mold clamp force is maintained at the set value S0, and the set value S0 A current corresponding to the difference between the detected value and the detected value is supplied to the mold clamping drive unit. The supply current to the mold clamping drive unit is feedback controlled so that a target mold clamping force is generated.

  At the start of mold clamping, in order to improve the rise of the mold clamping force, a current having a current value exceeding the rated current value (current value corresponding to the mold clamping force setting value S0) is supplied to the mold clamping drive unit. After detecting that the mold clamping force has reached the set value S0, the current value of the current supplied to the mold clamping drive unit is lowered to the rated current value.

  By the way, after detecting that the mold clamping force has reached the set value S0, the current value of the current supplied to the mold clamping drive unit does not immediately drop to the rated current value. This is because the supply current is affected by a delay in feedback control. It is known that this feedback control delay is caused by the action of integral control in PI control (proportional control, integral control) for controlling the supply current.

  Even after the mold clamping force reaches the target value, the supply current does not decrease immediately, so the mold clamping force exceeds the set value S0 and overshoots. Therefore, an excessive load is applied to the mold apparatus and the like, and the mold apparatus and the like are easily damaged. Further, since the mold clamping force fluctuates, the quality of the molded product is deteriorated.

On the other hand, at the end of mold clamping, the target value of mold clamping force is discontinuously changed from the set value S0 to 0 (zero). Thereafter, regardless of the difference between the detected value of the mold clamping force and the target value, the current supply to the mold clamping drive unit is cut off, and the mold clamping force decreases at a speed corresponding to the response delay of the mold clamping drive unit. If the reduction speed of the mold clamping force is too fast , the load applied to the mold apparatus or the like is greatly varied, and the impact applied to the mold apparatus or the like is large, so that the mold apparatus or the like is easily damaged. On the other hand, if the reduction rate of the clamping force is too fast, the molded product is peeled off, and the quality of the molded product is deteriorated.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an injection molding machine capable of suppressing damage to a mold apparatus and the like and improving the quality of a molded product when changing the clamping force. And

In order to solve the above problems, an injection molding machine according to an aspect of the present invention is provided.
A mold clamping drive for generating mold clamping force;
A mold clamping force detection unit for detecting the mold clamping force;
A storage unit for storing a data pattern defining a change with time of the target value of the clamping force;
A mold clamping processing unit for controlling the operation of the mold clamping drive unit based on a difference between a detected value of the mold clamping force detected by the mold clamping force detection unit and the target value stored in the storage unit; With
The target value is gradually lower down over time from a first set value to the second set value in the data pattern, then the mold clamping unit is, the direction of the current supplied to the electromagnet for generating the clamping force Is reversed .

  ADVANTAGE OF THE INVENTION According to this invention, when changing mold clamping force, while being able to suppress damage to a mold apparatus etc., the injection molding machine which can improve the quality of a molded product 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 data pattern which defined the time-dependent change at the time of the increase of the target value of the clamping force of the injection molding machine by one Embodiment of this invention. It is a figure which shows the data pattern which defined the time-dependent change at the time of the fall of the target value of the mold clamping force of the injection molding machine by one Embodiment of this invention. It is a figure which shows the time-dependent change of the target value and detection value of the mold clamping force in the conventional mold clamping process.

  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 suction plate 22 may be formed of a 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 are protruded toward the stator 29 and formed at a predetermined pitch, and the coil 35 is wound around each magnetic pole tooth 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 alternately magnetizing the N and S poles. A position sensor 53 that detects the position of the mover 31 is disposed.

  When the linear motor 28 is driven by supplying a predetermined current to the coil 35 of the linear motor 28, the mover 31 is moved forward and backward. Along with this, the suction plate 22 and the movable platen 12 are advanced and retracted, and the mold can be closed and opened. The linear motor 28 is feedback-controlled based on the detection result of the position sensor 53 so that the position of the mover 31 becomes a set 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 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.

  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 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 constitute a mold clamping device.

  The electromagnet unit 37 includes an electromagnet 49 as a mold clamping drive unit formed on the rear platen 13 side, and an adsorption unit 51 formed on the adsorption 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.

  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. Since the operation of the linear motor 28 is general, the description thereof is omitted.

  The control unit 60 includes a mold clamping force detection unit 61 that detects a mold clamping force. The mold clamping force detector 61 is connected to, for example, a strain sensor 55 that detects distortion (elongation amount) of the tie bar 14 that expands according to the mold clamping force, and detects the mold clamping force based on the detection result of the strain sensor 55. To do. For detecting the mold clamping force, a load sensor such as a load cell for detecting the load applied to the rod 39 or a magnetic sensor for detecting the magnetic field of the electromagnet 49 may be used instead of the strain sensor 55. The types of sensors used for force detection may vary widely. For example, the strain sensor can be applied not only to the tie bar 14 but also to the rod 39. This is because the distortion (contraction amount) of the rod 39 is proportional to the clamping force.

  In addition, the control unit 60 includes a storage unit 62 that stores a data pattern that defines a change with time of the target value of the mold clamping force. As the storage unit 62, a general device such as a magnetic storage medium, an optical storage medium, or a memory is used. The data pattern is created in advance by a test or the like and stored in the storage unit 62. The data pattern is read out as necessary, and is used to calculate the current value of the current supplied to the coil 48 of the electromagnet 49. The data pattern may be rewritable by the user.

Further, the control unit 60 controls the operation of the electromagnet 49 based on the difference between the detected value of the clamping force detected by the clamping force detection unit 61 and the target value stored in the storage unit 62. The unit 63 is provided. The mold clamping processing unit 63 performs PI control (proportional) as a current value of the current supplied to the coil 48 of the electromagnet 49 so that the difference between the detected value of the mold clamping force and the target value can be quickly eliminated (corrected). Control and integral control), and outputs a signal indicating the calculated current value to the current supply unit 70. The current value supplied to the electromagnet 49 is calculated in consideration of the response delay of the electromagnet 49. For example, at the start of mold clamping, the electromagnet 49 cannot apply the mold clamping force corresponding to the current supplied immediately due to the influence of eddy current or the like, and it takes some time until the mold clamping force reaches the target value. It is because it requires. Therefore, the current value calculated by the mold clamping processing unit 63 is not a current value uniquely determined corresponding to the difference between the detected value of the mold clamping force and the target value, but is larger than the current value at the start of mold clamping. Can be a value. Although the mold clamping processing unit 63 calculates the current value of the current supplied to the coil 48 of the electromagnet 49 by PI control, it may be calculated by PID control (proportional control, integral control, differential control).

  The current supply unit 70 includes, for example, an inverter including a plurality of power modules, and supplies a current corresponding to a signal supplied from the mold clamping processing unit 63 to the coil 48 of the electromagnet 49. The current supply unit 70 may have a function of changing the direction and strength (magnitude) of a direct current supplied to the coil 48 of the electromagnet 49.

  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 (the state of mold opening), the control unit 60 supplies current to the coil 35 to drive the linear motor 28. The movable platen 12 moves forward, and the movable mold 16 is brought into contact with the fixed mold 15 as shown in FIG. At this time, a 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.

  Subsequently, the control unit 60 controls the mold clamping process by the mold clamping processing unit 63. The mold clamping processing unit 63 supplies current to the coil 48 of the electromagnet 49 and attracts the attracting unit 51 to the electromagnet 49. 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.

  Based on the difference between the detected value of the mold clamping force detected by the mold clamping force detector 61 and the target value of the mold clamping force stored in the storage unit 62, the mold clamping processing unit 63 uses the coil 48 of the electromagnet 49. The current supplied to is adjusted and feedback controlled.

  Molten resin is filled in the cavity space of the mold apparatus 19 in the mold-clamping state. When the resin is cooled and solidified, the mold clamping unit 63 adjusts the current supplied to the coil 48 of the electromagnet 49 to release the mold clamping force.

  Next, the control unit 60 controls the mold opening process. The controller 60 drives the linear motor 28 to retract the movable platen 12, and the movable mold 16 is retracted to open the mold as shown in FIG.

  Next, details of processing by the mold clamping processing unit 63 will be described.

FIG. 3 is a diagram showing a data pattern that defines a change with time when the target value of the clamping force of the injection molding machine according to the embodiment of the present invention is increased . Data patterns P1 to P3 shown in FIG. 3 are used when the mold clamping force is increased from the first set value S1 toward the second set value S2, and are used at the start of mold clamping, for example. In FIG. 3, the horizontal axis indicates the elapsed time from the start of increasing the mold clamping force. In FIG. 3, since the detected value of the mold clamping force substantially overlaps with the target value of the mold clamping force, the illustration is omitted.

  In each of the data patterns P1 to P3, the target value of the mold clamping force gradually increases with time from the first set value S1 (for example, S1 = 0) to the second set value S2 (S2> S1). Therefore, when the mold clamping force is increased, the integrated value of the difference between the target value and the detected value of the mold clamping force is smaller than in the conventional case (see FIG. 5), and the influence of delay in feedback control due to integral control is reduced. The Therefore, it is possible to suppress the actual mold clamping force from exceeding the second set value S2 and overshooting. As a result, it is possible to suppress an excessive load from being applied to the mold apparatus 19 and the like, and it is possible to suppress damage to the mold apparatus 19 and the like. Moreover, the quality of a molded product can be improved.

  In each of the data patterns P1 to P3, the target value of the mold clamping force is such that the increasing speed near the first set value S1 (or / and near the second set value S2) is the first set value S1 and the second set value. It may be set to be smaller than the increasing speed in the middle of S2. The integrated value of the difference between the target value of the mold clamping force and the detected value can be further reduced.

  The plurality of data patterns P1 to P3 differ in the time required to continuously increase the target value of the mold clamping force from the first set value S1 to the second set value S2. The time required for the increase is t1 to t3 (t1 <t2 <t3), respectively.

The injection molding machine 10 may include an input unit 80 that receives a user operation for selecting any one of the plurality of data patterns P1 to P3. The input operation is performed by the user looking at an operation menu image displayed on the display, for example. In the operation menu image, for example, numbers and characters such as “1: short”, “2: medium”, and “3: long” are displayed. Users who viewed the operation menu image, for example by pressing a button indicating "1" in the input unit 80, can be increased to the target value of the clamping force in a short time t1 from the first set value S1 until the second set value S2 I understand. The input unit 80 is configured by a keyboard or the like, for example, and is connected to the mold clamping processing unit 63. The mold clamping processing unit 63 selects one of a plurality of data patterns P1 to P3 based on an operation signal indicating a user operation at the input unit 80, and according to the selected data pattern (for example, the data pattern P1). The current value of the current supplied to the coil 48 of the electromagnet 49 is adjusted. Therefore, the increasing speed of the mold clamping force can be determined by the user's intention.

FIG. 4 is a diagram showing a data pattern that defines a change over time when the target value of the mold clamping force of the injection molding machine according to the embodiment of the present invention is lowered . Data patterns P4 to P6 shown in FIG. 4 are used when the mold clamping force is decreased from the third set value S3 toward the fourth set value S4, and are used, for example, at the end of mold clamping. In FIG. 4, the horizontal axis indicates the elapsed time from the start of the decrease in mold clamping force. In FIG. 4 , since the detected value of the mold clamping force substantially overlaps with the target value of the mold clamping force, the illustration is omitted.

  In each data pattern P4 to P6, the target value of the mold clamping force gradually decreases with time from the third set value S3 (for example, S3 = S2) to the fourth set value S4 (S3> S4> 0). For this reason, when the mold clamping force is reduced, the current value of the current supplied to the coil 48 of the electromagnet 49 gradually decreases, so that the rate of decrease in the mold clamping force becomes gradual compared to the conventional case (see FIG. 5). Therefore, the fluctuation | variation of the load concerning the mold apparatus 19 etc. can be suppressed, and damage to the mold apparatus 19 etc. can be suppressed. Moreover, the quality of a molded product can be improved.

  In each of the data patterns P4 to P6, the target value of the mold clamping force is a decrease rate in the vicinity of the third set value S3 (or / and in the vicinity of the fourth set value S4), the third set value S3 and the fourth set value. It may be set to be smaller than the rate of decrease in the middle of the value S4.

  The plurality of data patterns P4 to P6 differ in the time required for continuously decreasing the target value of the mold clamping force from the third set value S3 to the fourth set value S4. The time required for the decrease is t4 to t6 (t4 <t5 <t6), respectively.

  A user's operation for selecting any one of the plurality of data patterns P4 to P6 is received by the input unit 80. The input operation is performed by the user looking at an operation menu image displayed on the display, for example. For example, numbers and characters such as “4: short”, “5: medium”, and “6: long” are displayed on the operation menu image. For example, if the user who sees the operation menu image presses a button indicating “4” of the input unit 80, the target value of the mold clamping force can be decreased from the third set value S3 to the fourth set value S4 in a short time t4. Recognize.

  The mold clamping processing unit 63 selects any one of a plurality of data patterns P4 to P6 based on an operation signal indicating a user operation at the input unit 80, and according to the selected data pattern (for example, the data pattern P4). The current value of the current supplied to the coil 48 of the electromagnet 49 is adjusted. Therefore, the mold clamping force decreasing speed can be determined by the user's intention.

  When the mold clamping force is less than or equal to the fourth set value S4, the influence of the load variation on the mold apparatus 19 and the like is sufficiently small. Regardless of the current supply, the current supply to the coil 48 of the electromagnet 49 may be stopped. Thereafter, the mold clamping force decreases at a speed corresponding to the response delay of the electromagnet 49. The response delay of the electromagnet 49 is caused by the influence of magnetism remaining on the electromagnet 49 (for example, the core 46).

  When the influence of residual magnetism is large and the rate of decrease in mold clamping force is slow, the mold clamping force is detected after detecting that the mold clamping force has fallen below the fourth set value S4 in order to shorten the waiting time until the mold opening starts. The processing unit 63 may supply a direct current in a direction opposite to a direction in which a predetermined mold clamping force (for example, mold clamping force = S3) is generated, to the coil 48 of the electromagnet 49. Since a magnetic field is formed in a direction that cancels out the magnetic field remaining in the electromagnet 49 (for example, the core 46), it is possible to promote a decrease in mold clamping force.

In order to reduce the influence of residual magnetism more positively, the clamping unit 63 supplies a direct current in the reverse direction to the coil 48 of the electromagnet 49 and then sets the direction of the direct current supplied to the coil 48 of the electromagnet 49 to 1. It may be reversed more than once. The strength (magnitude) of the direct current supplied to the coil 48 of the electromagnet 49 may be set to be small each time it is reversed.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and the like, and various modifications and substitutions are made to the above-described embodiments and the like without departing from the scope of the present invention. Can be added.

  For example, the mold clamping drive unit of the above embodiment is composed of the electromagnet 49, but may be composed of a motor that drives a toggle mechanism or a fluid pressure cylinder (such as a hydraulic cylinder or a pneumatic cylinder). It may be a general configuration used for mold clamping operation.

10 Injection Molding Machine 15 Fixed Mold 16 Movable Mold 49 Electromagnet (Clamping Drive Unit)
51 Suction Unit 55 Strain Sensor 60 Control Device 61 Mold Clamping Force Detection Unit 62 Storage Unit 63 Clamping Processing Unit 70 Current Supply Unit 80 Input Unit

Claims (2)

A mold clamping drive for generating mold clamping force;
A mold clamping force detection unit for detecting the mold clamping force;
A storage unit for storing a data pattern defining a change with time of the target value of the clamping force;
A detection value of the mold clamping force detected by the mold clamping force detector, on the basis of the difference between said stored target value in the storage unit, mold clamping unit for controlling the operation of the mold clamping drive section And
The target value is gradually lower down over time from a first set value to the second set value in the data pattern, then the mold clamping unit is, the direction of the current supplied to the electromagnet for generating the clamping force An injection molding machine characterized by reversing the direction . An input unit that accepts an input operation by a user;
The storage unit stores a plurality of said data patterns having different time during which the target value is required for low down from the first set value to the second set value,
The mold clamping processing unit selects any one of the plurality of data patterns based on an operation signal indicating a user input operation at the input unit, and operates the mold clamping drive unit according to the selected data pattern. The injection molding machine according to claim 1, wherein the injection molding machine is controlled.

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