JP6068174B2 - Rear platen adjustment device for injection molding machine - Google Patents

Description

  The present invention relates to a rear platen adjusting device for an injection molding machine.

  If the mold clamping force can be adjusted accurately when the mold of the injection molding machine is replaced, the next production can be started smoothly, and an improvement in production efficiency can be expected. If accurate mold clamping force can be maintained, stabilization of the quality of the molded product can be expected. When adjusting the mold clamping force in a toggle type mold clamping device, measure the mold clamping force with a mold clamping force sensor, etc., and obtain the rear platen adjustment amount from the difference between the measured mold clamping force and the target mold clamping force. A method of adjusting the mold clamping force by moving the mold is known. For this reason, accurately moving the rear platen with respect to the obtained adjustment amount is important for accurately adjusting the mold clamping force. There is some backlash in the gear train of the drive mechanism that moves the rear platen. Therefore, in order to accurately move the rear platen, it is necessary to correct the movement error caused by this backlash.

  As a technique for correcting the movement error of the rear platen caused by backlash, the position of the rear platen can be controlled regardless of backlash by directly measuring the actual movement distance of the rear platen with a linear sensor, or using a pulse sensor in advance. There is a method of driving a rear platen adjustment motor in consideration of a backlash movement error and moving the rear platen to a target position.

Patent Document 1 discloses a method of controlling a link housing (rear platen) to a target position using a linear sensor when adjusting a mold clamping force.
Patent Document 2 discloses a technique for adjusting a predetermined mold thickness by moving a rear platen by correcting a backlash of a driving system using a pulse coder.
In addition, as a technique for stopping the table of the injection molding machine at the optimal position in the gear train of the table drive mechanism where backlash occurs, the load of the servo motor and changes in current are monitored in the backlash section of the table drive mechanism to monitor the table. A technique for obtaining a stop position is described in Patent Document 3.

Japanese Patent Laid-Open No. 10-80759 JP-A-1-221217 JP 2000-202853 A

As described in the prior art, since there is some backlash in the gear train of the drive mechanism that moves the rear platen, in order to accurately move the rear platen in accordance with the desired adjustment amount, a movement error caused by the backlash must be reduced. It is necessary to correct.
With respect to this problem, Patent Document 1 discloses a method of arranging a linear sensor in order to accurately measure the position of the rear platen. However, the method of arranging the linear sensor described in Patent Document 1 has a problem that the structure of the injection molding machine becomes complicated.
The method of moving the rear platen by correcting the drive system backlash using the pulse coder described in Patent Document 2 corrects the backlash only when the direction of movement of the rear platen is different from the previous time. The contents to the effect that correction of a predetermined correction amount to be performed is performed are described.

  However, backlash may occur in addition to the situation described in Patent Document 2 due to distortion of the drive mechanism in mold clamping, mechanical vibration, and the like. In the case of backlash that occurs in this way, the gear train of the drive mechanism is not always on either side, and the amount of correction required for backlash correction is not always the same. It is also conceivable that the correction amount necessary for correcting the backlash of the gear train changes even with the aging of the gear train of the drive mechanism. For this reason, the method described in Patent Document 2 can deal only with backlash that occurs when the moving direction changes, and it is necessary to determine the amount of correction that changes in various situations, which is troublesome. .

  Therefore, in view of the above-described problems of the prior art, the present invention detects an undriven section of the rear platen caused by backlash of the drive mechanism based on a change in driving current or load of the motor for adjusting the rear platen, and so on. An object of the present invention is to provide a rear platen adjusting device for an injection molding machine that can adjust the clamping force accurately by moving the rear platen by an accurate distance without using a sensor having a complicated structure for mounting.

  In the present invention, the drive current of the rear platen adjustment motor for moving the rear platen at a predetermined speed or the change in the absolute value of the load in the undriven section of the rear platen caused by backlash in the gear train of the drive mechanism for moving the rear platen is changed. It is detected based on this, and the moving distance of a rear platen is controlled accurately.

  When there is a backlash in the gear train of the drive mechanism that moves the rear platen, there is an undriven section in which the rear platen does not move until the gear train rotates by the backlash even if the rear platen adjustment motor is rotated. In the non-drive section, the load applied to the adjustment motor is reduced, and the load applied to the rear platen adjustment motor is increased after the gear train rotates by the backlash and the rear platen starts to move. In other words, when trying to move the rear platen only by a certain target distance, the position where the load on the rear platen adjustment motor has changed significantly is taken as the movement start position of the rear platen, and the rear platen adjustment motor is rotated from that position by the target movement distance. By doing so, it becomes possible to accurately control the movement distance of the rear platen regardless of the backlash state. For the movement of the rear platen from the movement start position, the position is controlled by controlling the amount of movement of the rear platen with a timer, or the position of the rear platen adjustment motor is controlled using a geared motor or servo motor with a position detector. The method is applicable.

  The invention according to claim 1 of the present application is a toggle-type mold clamping device that is disposed between a movable platen to which a rear platen and a movable mold are attached, and moves the movable platen back and forth by a mold clamping drive unit; Rear platen adjustment moving distance for correcting the mold clamping force based on the difference between the mold clamping force measured by the mold clamping force measuring means and the target clamping force measured by the rear platen adjusting motor for moving the rear platen. A rear platen adjusting device for an injection molding machine, comprising: a corrected moving distance calculating means for calculating the rear platen; and a rear platen position correcting means for driving the rear platen adjusting motor to move the rear platen by the corrected moving distance calculated by the corrected moving distance calculating means. The rear platen position correcting means monitors the drive current or load of the rear platen adjusting motor when the rear platen is moved. An injection molding machine characterized in that the rear platen is moved from the rear platen movement start position by the correction movement distance with a position at which the drive current or load has detected a first predetermined change or more as a rear platen movement start position. This is a rear platen adjusting device.

  In the invention according to claim 2, the first predetermined change or more is that the absolute value of the drive current or load of the rear platen adjustment motor exceeds a threshold value, or the unit of drive current or load of the rear platen adjustment motor. The amount of change per time exceeds a threshold value, or the amount of change per unit moving distance of the driving current or load of the rear platen adjustment motor exceeds a threshold value. It is a rear platen adjustment apparatus of the injection molding machine.

  According to a third aspect of the present invention, the rear platen position correcting means moves the rear platen by the correction movement distance, and then moves the rear platen adjustment motor in a direction opposite to the direction in which the rear platen adjustment motor is rotated in the correction. The rotation of the rear platen adjusting motor is stopped at a position where the driving current or the load detects a change greater than or equal to a second predetermined value. It is a rear platen adjustment apparatus of the injection molding machine.

  According to a fourth aspect of the present invention, the second predetermined change is that the absolute value of the drive current or load of the rear platen adjustment motor exceeds a threshold value, or the unit of drive current or load of the rear platen adjustment motor. The amount of change per time exceeds a threshold value, or the amount of change per unit moving distance of the driving current or load of the rear platen adjustment motor exceeds a threshold value. It is a rear platen adjustment apparatus of the injection molding machine.

  The invention according to claim 5 is a pulse coder attached to a geared motor, or a movement amount control by a timer, a position control of a servo motor used for the rear platen adjustment motor, when controlling the movement of the rear platen. It controls, The rear platen adjustment apparatus of the injection molding machine as described in any one of Claims 1-4 characterized by the above-mentioned.

  According to the present invention, a non-driven section of the rear platen resulting from the backlash of the drive mechanism is detected based on a change in driving current or load of the motor for adjusting the rear platen, thereby using a sensor having a complicated structure for mounting a linear scale or the like. In addition, it is possible to provide a rear platen adjusting device for an injection molding machine capable of accurately adjusting the clamping force by moving the rear platen by an accurate distance.

It is a figure explaining the mold clamping apparatus of an injection molding machine. It is a figure explaining a rear platen transmission mechanism. It is a flowchart explaining the process which adjusts a mold clamping force.

  Hereinafter, an embodiment of an injection molding machine of the present invention will be described with reference to the drawings. 1 and 2 are schematic views of an embodiment of an injection molding machine according to the present invention.

  The stationary platen 1 and the rear platen 2 are connected by a plurality of tie bars 4. A movable platen 3 is disposed along the tie bar 4 between the fixed platen 1 and the rear platen 2. A fixed mold 5a is attached to the fixed platen 1, and a movable mold 5b is attached to the movable platen 3 so as to face the fixed mold 5a.

  A toggle mechanism 6 is disposed between the rear platen 2 and the movable platen 3, and a nut (not shown) provided on the cross head 6 a of the toggle mechanism 6 is attached to the rear platen 2 so as to be rotatable and not movable in the axial direction. The ball screw 7 is screwed. The ball screw 7 is driven by a mold clamping servo motor 8 through a transmission mechanism, whereby the movable platen 3 is moved forward and backward in the direction of the fixed platen 1 to open and close the molds 5a and 5b, and thereby perform the toggle. Forms a mold clamping device. The mold clamping servomotor 8 is provided with a position / speed detector 11 for detecting the rotational position and speed of the servomotor such as a pulse encoder. Thus, the position of the cross head 6a and the position of the movable platen 3 (movable side mold 5b) can be detected.

Further, a rear platen adjusting means is configured by a rear platen transmission mechanism (see FIG. 2) including a rear platen adjusting motor 10, a tie bar nut 9, and a gear.
The end of the tie bar 4 on the rear platen 2 side is threaded. The tie bar nut 9 screwed with the screw is rotated by the rear platen adjusting motor 10 via the transmission gears 10 a and 10 b of the transmission mechanism (FIG. 2), so that the rear platen 2 can move forward and backward along the tie bar 4. A position detector is attached to the rear platen adjustment motor 10 so that the position of the rear platen 2 can be adjusted. The rear platen adjusting motor 10 may be a servo motor provided with a position / speed detector. The controller 20 can also be provided with an observer circuit for estimating the load of the rear platen adjusting motor 10.

  The mold clamping force sensor 13 is disposed on at least one of the four tie bars 4. The mold clamping force sensor 13 is a sensor that measures distortion (mainly elongation) of the tie bar 4. When the mold is clamped, the tie bar 4 is applied with a tensile force corresponding to the mold clamping force, and extends slightly in proportion to the mold clamping force. Therefore, by measuring the extension amount of the tie bar 4 with the mold clamping force sensor 13, the mold clamping force actually applied to the molds 5a and 5b can be known.

  Reference numeral 20 denotes a control device for controlling the injection molding machine. FIG. 1 shows only the main part of the control device 20. An axis control circuit 22, an input / output circuit 24, a memory 26, an A / D converter 27 for controlling the position, speed, and current (torque) of the servo motor via a bus 30 to a processor (CPU) 21 that controls the whole. The interface 28 of the display device 29 is connected.

  The axis control circuit 22 includes a processor, a memory, an interface, and the like. The position / speed feedback signal from the position / speed detector 11 attached to the mold clamping servomotor 8 is fed back. A current feedback signal from the current detector 12 that detects the drive current is fed back. A mold clamping servomotor 8 is connected to the shaft control circuit 22 via a servo amplifier 23.

  Further, the rear platen adjusting motor 10 is connected to the input / output circuit 24 via the inverter 25, and the display device 29 is connected to the interface 28. The memory 26 stores a program for controlling the injection molding machine. A program created based on the algorithm of the flowchart for adjusting the clamping force shown in FIG. 3 is also stored in the memory 26.

  The processor 21 controls the injection molding machine based on these programs. Regarding the mold clamping operation, the processor 21 outputs a movement command to the axis control circuit 22 based on the program. A processor (not shown) built in the axis control circuit 22 determines the position and speed based on the movement command and the position / speed feedback signal from the position / speed detector 11 and the current feedback signal from the current detector 12. , And feedback control of current, and drive control of the mold clamping servomotor 8 via the servo amplifier 23 is performed.

  When the mold clamping servomotor 8 is driven, the ball screw 7 is rotated, and the crosshead 6a of the toggle mechanism 6 having a nut (not shown) screwed to the ball screw 7 moves along the ball screw 7, so that the toggle mechanism 6 Is driven, the movable platen 3 moves forward, the movable mold 5b contacts the fixed mold 5a, further moves the movable platen 3, the link of the toggle mechanism 6 extends, and the movable platen 3 reaches a predetermined position. When the lockup position is reached, the mold clamping servomotor 8 is positioned at this position, and the position of the rear platen 2 is adjusted so that the target mold clamping force is generated.

  That is, since the fixed platen 1 and the rear platen 2 are connected by the tie bar 4, when the fixed mold 5a and the movable mold 5b come into contact with each other and the movable platen 3 and the movable mold 5b move forward, the tie bar 4 is extended, and the target mold clamping force is adjusted by the reaction force of the extension of the tie bar 4.

  Because of such a structure, when the molds 5a and 5b are replaced with different mold thicknesses or when the mold clamping force is changed, the position of the rear platen 2 must be moved to adjust the mold clamping force. Don't be. The processor 21 can drive the rear platen adjusting motor 10 via the input / output circuit 24 and rotate the tie bar nut 9 via the transmission mechanism (FIG. 2) to move the position of the rear platen 2.

  In such an injection molding machine that drives a toggle type mold clamping mechanism with the mold clamping servomotor 8, the mold clamping force may fluctuate due to thermal expansion of the molds 5a and 5b during the automatic operation of the injection molding machine. . Therefore, in an injection molding machine having a toggle type mold clamping device, when such a variation in mold clamping force occurs, the mold clamping force is adjusted by moving the rear platen. At that time, it is necessary to accurately control the position of the rear platen.

  In the present invention, in order to accurately control the position of the rear platen 2, a rear platen adjustment motor is detected by detecting an undriven section of the rear platen due to backlash of the transmission mechanism (FIG. 2) from a load applied to the rear platen adjustment motor 10. When the rear platen 2 is moved by adding a correction corresponding to the undriven section with respect to the target moving distance with the rotation amount of 10, accurate position control becomes possible and accurate mold clamping force adjustment becomes possible. In addition, the movement control of the rear platen 2 is attached to a movement amount control by a timer (not shown) provided in the control device 20, a position control of a servo motor used for the rear platen adjustment motor 10, or a geared motor. This can be done based on the output signal from the pulse coder.

FIG. 3 is a flowchart for adjusting the mold clamping force. Hereinafter, it demonstrates according to each step.
[Step SA01] A target mold clamping force is set. More specifically, the value of the target mold clamping force is read from a memory that stores the value of the target mold clamping force preset by the operator.
[Step SA02] Lock up and measure the current clamping force.
[Step SA03] If | target mold clamping force−measured mold clamping force | ≧ α, the process proceeds to step SA04. If | target mold clamping force−measurement mold clamping force | <α, the process is terminated. Α is an allowable error when adjusting to the target clamping force.
[Step SA04] The rear platen adjustment amount is calculated from the difference between the target mold clamping force and the measured mold clamping force.
[Step SA05] The rear platen adjustment motor is driven in the adjustment direction until the absolute value of the motor load ≧ β. Β is a load threshold for detecting an undriven section due to backlash.
[Step SA06] The rear platen adjustment motor is driven by the adjustment amount from the point where the load applied to the rear platen adjustment motor exceeds the threshold value β.
[Step SA07] If the rear platen adjustment direction is the forward direction (direction in which the mold closes), the process returns to Step SA02. If the rear platen adjustment direction is the backward direction (the direction in which the mold opens), the process proceeds to step SA08.
[Step SA08] The rear platen adjustment motor is driven in the opposite direction of adjustment until the absolute value of the motor load ≧ β. Β is a load threshold for detecting an undriven section due to backlash.

The above flowchart will be supplementarily described.
When the rear platen is moved, the driving current or load of the rear platen adjustment motor is monitored, and the position where the driving current or load detects a change of the first predetermined value or more is set as the rear platen movement start position, and the rear platen is moved from the rear platen movement start position. Move it for the correction travel distance.

  In step SA05, β is a load threshold for detecting an undriven section due to backlash (corresponding to the “first or more predetermined change” in claim 1), but the drive current of the rear platen adjustment motor In the case where an undriven section due to backlash is detected based on the above, a threshold value of the drive current is used.

  Alternatively, in step SA05, the change per unit time of the driving current or load of the rear platen adjustment motor exceeds the threshold as the first predetermined change or more, or the unit movement of the driving current or load of the rear platen adjustment motor An undriven section due to backlash may be determined by either the amount of change per distance exceeding a threshold.

  In the process of the flowchart described above, after the rear platen is moved by the correction movement distance, the rear platen adjustment motor is rotated in the direction opposite to the direction in which the rear platen adjustment motor is rotated in the correction, and the drive current of the rear platen adjustment motor is Alternatively, the rotation of the rear platen adjustment motor is stopped at a position where the load detects a change of the second predetermined value or more. For example, when the rear platen adjustment direction is the backward direction (the mold opening direction), after the rear platen is moved to the target position in step SA06, the rear platen adjustment motor is reversely rotated by the backlash performed in step SA08 (the mold is closed). Direction), it is possible to remove the backlash caused by the movement of the rear platen that affects the lock-up. Here, the value of the motor load of the rear platen adjustment motor is used as the second predetermined change or more.

The second predetermined change or more is that the absolute value of the driving current or load of the rear platen adjustment motor exceeds a threshold value, or the amount of change per unit time of the driving current or load of the rear platen adjustment motor exceeds the threshold value. Or the amount of change per unit moving distance of the drive current or load of the rear platen adjusting motor may exceed a threshold value.
Note that the first predetermined change or more and the second predetermined change or more may be the same.

  The load of the rear platen adjustment motor may be obtained from the torque of the rear platen adjustment motor, or an observer circuit that estimates the load of the rear platen adjustment motor may be used.

DESCRIPTION OF SYMBOLS 1 Fixed platen 2 Rear platen 3 Movable platen 4 Tie bar 5a Fixed side metal mold 5b Movable side metal mold 6 Toggle mechanism 6a Cross head 7 Ball screw 8 Mold clamping servo motor 9 Tie bar nut 10 Rear platen adjustment motor 10a Transmission gear a
10b Transmission gear b
11 Position / Speed Detector 12 Current Detector 13 Clamping Force Sensor

DESCRIPTION OF SYMBOLS 20 Control apparatus 21 Processor 22 Axis control circuit 23 Servo amplifier 24 Input / output circuit 25 Inverter 26 Memory 27 A / D converter 28 Interface 29 Display apparatus 30 Bus

Claims (5)

A toggle type mold clamping device that is disposed between a rear platen and a movable platen to which a movable mold is attached and moves the movable platen back and forth by a mold clamping driving means, a rear platen adjustment motor that moves the rear platen, and a mold Clamping force measuring means, corrected moving distance calculating means for calculating a rear platen corrected moving distance for correcting the mold clamping force from the difference between the mold clamping force measured by the mold clamping force measuring means and the target mold clamping force, and the rear platen In a rear platen adjusting device for an injection molding machine, comprising: a rear platen position correcting unit that drives an adjustment motor to move a rear platen by a corrected moving distance calculated by a corrected moving distance calculating unit;
The rear platen position correcting means monitors the drive current or load of the rear platen adjustment motor when the rear platen is moved, and the position where the drive current or load detects a change of a first predetermined value or more is used as the rear platen movement start position. A rear platen adjusting device for an injection molding machine, wherein the rear platen is moved from the rear platen movement start position by the correction moving distance.   The first predetermined change or more is that the absolute value of the driving current or load of the rear platen adjustment motor exceeds a threshold value, or the amount of change per unit time of the driving current or load of the rear platen adjustment motor exceeds the threshold value. 2. The rear platen adjusting device for an injection molding machine according to claim 1, wherein the amount of change per unit moving distance of a driving current or a load of the rear platen adjusting motor exceeds a threshold value. .   The rear platen position correction means moves the rear platen by the correction movement distance, and then rotates the rear platen adjustment motor in a direction opposite to the direction in which the rear platen adjustment motor is rotated in the correction, and the drive current or load 3. The rear platen adjustment device for an injection molding machine according to claim 1, wherein the rotation of the rear platen adjustment motor is stopped at a position where the second predetermined change or more is detected. .   The second predetermined change or more is that the absolute value of the driving current or load of the rear platen adjustment motor exceeds a threshold value, or the amount of change per unit time of the driving current or load of the rear platen adjustment motor exceeds the threshold value. 4. The rear platen adjusting device for an injection molding machine according to claim 3, wherein the amount of change per unit moving distance of a driving current or a load of the rear platen adjusting motor exceeds a threshold value. 5. .   The movement of the rear platen is controlled by a movement amount control by a timer, a position control of a servo motor used for the rear platen adjustment motor, or a pulse coder attached to a geared motor. Item 5. A rear platen adjusting device for an injection molding machine according to any one of Items 1 to 4.

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