JP2011218708A - Method of controlling injection molding machine, and injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve control responsiveness to disturbance when a movable mold or a part of the movable mold is moved in a mold-opening direction by speed-control using a servomotor, in shaping a foamed molding or a hollow molding, to adjust a load of the servomotor or a ball screw mechanism within a preferable range.SOLUTION: A method of controlling an injection molding machine 11 comprises: moving the movable mold 16 or a part of the movable mold in the mold-opening direction to increase the volume of a cavity C while or after injecting a molten resin into the cavity C formed between a fixed mold 14 and the movable mold 16, and shaping the foamed molding or the hollow molded article. When the volume of the cavity C is increased, the movable mold 16 or a part of the movable mold is moved to the mold-opening direction for speed-control by the servomotor 25, and at the same time, in response to the disturbance, the movable mold 16 or a part of the movable mold is pressed to a mold-closing direction by a closed loop control of a fluid mechanism 29.

Description

  The present invention moves the movable mold or a part of the movable mold in the mold opening direction during or after the injection of the molten resin into the cavity formed between the fixed mold and the movable mold, thereby increasing the volume of the cavity. The present invention relates to an injection molding machine control method for expanding and molding a foam molded article or a hollow molded article, and an injection molding machine.

  When molding a foam molded product by an injection molding machine, the movable mold or a part of the movable mold is moved in the mold opening direction to enlarge the volume of the cavity, and the foam molded product is molded. As a control method in that case, methods described in Patent Documents 1 to 3 are known. The injection foam molding machine of Patent Document 1 includes a boost cylinder and controls a servo motor that drives a hydraulic pump, thereby controlling an oil supply amount to the boost cylinder and controlling a movable position control. . However, Patent Document 1 has a problem that the responsiveness is inferior to that in which the speed is controlled by a servo motor because the movable position is performed by a hydraulic cylinder. In addition, it is necessary to separately provide a hydraulic pump driven by a servo motor in order to perform control for foaming in the boost cylinder.

  In Patent Document 2 and Patent Document 3, movement of the movable platen in the mold opening direction during foam molding is performed by speed control of a servo motor. The mold clamping cylinder is filled with hydraulic oil so that a constant force acts in the mold closing direction in opposition to the foaming force of the foamed molded product in the cavity. However, the control methods of Patent Document 2 and Patent Document 3 have the following problems. That is, the foamed molded product in the cavity does not always foam at every molding cycle, and foaming may progress or exceed the set speed of the servo motor. In these cases, there is a problem that an undesired load may be applied to the servo motor, the ball screw, or the like because a constant force always acts in the mold closing direction due to the hydraulic pressure.

Also, when a hollow molded product is molded by an injection molding machine, as shown in Patent Document 4, the cavity volume is increased by moving the movable mold or a part of the movable mold in the mold opening direction. Forming a molded product is performed. Also in this case, when the movable mold is moved in the mold opening direction, the resin injection amount and the gas filling amount are not completely the same. there were.

JP 2002-283425 A (Claim 1, 0023, FIG. 1) JP 2002-321262 A (Claim 1, 0021, FIG. 2) Japanese Patent Laying-Open No. 2005-342935 (Claim 1, 0027, FIG. 1) JP-A-8-267696 (Claim 1, 0027, FIG. 1)

  In the present invention, in view of the above problems, when molding a foam molded product or a hollow molded product, the speed is controlled using a servo motor to move a movable mold or a part of the movable mold in the mold opening direction. An object of the present invention is to provide an injection molding machine control method and an injection molding machine that improve the control response performance with respect to the external disturbance and make the load of the servo motor and the ball screw mechanism within a preferable range.

According to a first aspect of the present invention, there is provided a method for controlling an injection molding machine comprising: one of a movable mold and a movable mold, during or after injection of molten resin into a cavity formed between a fixed mold and a movable mold. In the control method of an injection molding machine that molds a foam molded product or a hollow molded product by moving the part in the mold opening direction, the movable mold or movable mold A part of the movable mold is moved in the mold opening direction by speed control by a servo motor, and the movable mold or a part of the movable mold is closed-loop controlled by a fluid mechanism in response to a disturbance.

  The method of controlling an injection molding machine according to claim 2 of the present invention is the method according to claim 1, wherein the load of the servo motor, the moving speed of the movable mold or a part of the movable mold in the mold opening direction, the resin in the cavity The closed loop control of the fluid mechanism is performed by detecting at least one of the pressure and the retracting force of the movable mold or a part of the movable mold in the mold opening direction.

  According to a third aspect of the present invention, there is provided an injection molding machine in which the movable mold or a part of the movable mold is molded during or after the molten resin is injected into the cavity formed between the fixed mold and the movable mold. In an injection molding machine that expands the cavity volume by moving in the opening direction and molds foam molded products or hollow molded products, the speed of the movable mold or a part of the movable mold is controlled when expanding the cavity volume. And a fluid mechanism capable of pressing the movable mold or a part of the movable mold in the mold closing direction by closed loop control.

  According to a fourth aspect of the present invention, there is provided the injection molding machine according to the third aspect, wherein the detecting means for detecting the load of the servo motor, the movable mold or a moving speed of the movable mold in the mold opening direction is detected. At least one of detection means, detection means for detecting the resin pressure in the cavity, and detection means for detecting the retracting force in the mold opening direction of the movable mold or a part of the movable mold is provided. The closed loop control of the fluid mechanism is performed based on the detected value.

A method for controlling an injection molding machine and an injection molding machine according to the present invention include a movable mold or a part of a movable mold during or after injection of molten resin into a cavity formed between a fixed mold and a movable mold. In the control method of an injection molding machine for foam molded products that expands the volume of the cavity by moving the mold in the mold opening direction and molds the foam molded product, a movable mold or a part of the movable mold is moved by a servo motor in the foaming process. The speed is controlled to move in the mold opening direction, and the movable mold or a part of the movable mold is closed-loop controlled by the fluid mechanism in response to the disturbance, so that the load of the servo motor and the ball screw mechanism is within a preferable range. Therefore, it is possible to realize a good foam molded product or hollow molded product.

It is a front view of the injection molding machine of the foaming molded product of this embodiment. It is a flowchart figure (first half) of the control method of the injection molding machine of the foaming molded product of this embodiment. It is a flowchart figure (latter half) of the control method of the injection molding machine of the foaming molded product of this embodiment. It is a flowchart figure (the first half) of the control method of the injection molding machine of the foaming molded product of another embodiment. It is a flowchart figure (latter half) of the control method of the injection molding machine of the foaming molded product of another embodiment. It is a principal part enlarged view of the injection molding machine of the foaming molded product of another embodiment.

An injection molding machine 11 that performs foam molding according to an embodiment of the present invention will be described with reference to FIG. The injection molding machine 11 includes a basic part including a mold clamping device 12 and an injection device 13 provided on the side thereof. In the mold clamping device 12 of the present embodiment, the movable plate 17 to which the movable die 16 is attached is moved by the die opening / closing mechanism 18 with respect to the fixed plate 15 to which the fixed die 14 is attached, and the half nut 20 of the half nut mechanism 19 is moved. The mold is clamped by the mold clamping mechanism 22 after engaging the engaging portion 21. More specifically, the mold clamping device 12 is provided with a fixed platen 15 and a pressure receiving plate 23 on a bed, and four tie bars 24 are arranged between the fixed platen 15 and the pressure receiving plate 23 in parallel. A movable platen 17 is inserted into the tie bar 24, and the movable platen 17 is movable in the mold opening / closing direction with respect to the fixed platen 15.

Next, the mold opening / closing mechanism 18 will be described. A servo motor 25 of the mold opening / closing mechanism 18 is fixed to the stationary platen 15, and a ball screw 26 is pivotally supported on the stationary platen 15 so as not to move in the mold opening / closing direction and to rotate. The ball screw 26 is connected to be rotated by the rotation of the drive shaft of the servo motor 25. The positions of the movable platen 17 and the movable die 16 with respect to the fixed platen 15 and the fixed die 14 are detected by a rotary encoder 28 which is a position sensor of the servomotor 25 of the die opening / closing mechanism 18. A ball screw nut 27 is fixed to the bracket 17a of the movable platen 17, and a ball screw 26 is rotatably inserted into the ball screw nut 27 to constitute a ball screw mechanism. The other end of the ball screw 26 is rotatably supported by the pressure receiving plate 23. In the present embodiment, the mold opening / closing mechanism 18 is provided diagonally at two locations on the fixed platen 15 and the movable platen 17 on one side lower part and the other side upper part. In addition, the mold opening / closing mechanism 18 may be provided with three or more, preferably four with a large foam molded product or a high precision foam molded product. Furthermore, the mold opening / closing mechanism 18 may be one in which an electric motor such as a servo motor 25 is attached to any of the movable plate 17 and the pressure receiving plate 23 on the bed.

A load cell 40 as a force detection means is attached between the bracket 17a of the movable platen 17 of one mold opening / closing mechanism 18 and the ball screw nut 27. The load cell 40 is a detecting means for detecting a retracting force in the mold opening direction of the movable platen 17 during foam molding. In this embodiment, the load cell 40 is interposed between the ball screw nut 27 of one mold opening / closing mechanism 18 and the bracket 17a of the movable platen 17. Although attached, it may be attached to both mold opening / closing mechanisms 18. Further, the load cell 40 may be attached to another part where the retracting force of the movable mold 16 can be detected, such as between the movable mold 16 and the movable platen 17.

Next, the mold clamping mechanism 22 using a hydraulic mechanism that is a fluid mechanism will be described. The pressure receiving plate 23 is formed with a cylinder 30 of a clamping cylinder 29 that is a return cylinder. A cylindrical mold clamping ram 31 is inserted into the cylinder cylinder 30. A position sensor 36 for detecting the position of the mold clamping ram 31 is attached across both the pressure receiving plate 23 and the mold clamping ram 31. A mold clamping side oil chamber 32 a and a mold opening side oil chamber 32 b are formed between the cylinder cylinder 30 and the mold clamping ram 31. The mold clamping side oil chamber 32a is supplied with hydraulic oil from a pump 33 via a servo valve 34. The servo valve 34 may be connected to both the mold clamping side oil chamber 32a and the mold opening side oil chamber 32b. As the valve for controlling the mold clamping cylinder 29, a valve having a function capable of controlling the flow rate by closed loop control may be used as in the servo valve. Further, the mold clamping mechanism may be one in which mold clamping cylinders each having a tie bar as a rod are provided in the vicinity of four corners of a fixed plate or the like, or a mold clamping or the like by another hydraulic mechanism. Furthermore, the mold clamping device may be opened and closed in the vertical direction.

A half nut mechanism 19 is attached to the distal end side of the mold clamping ram 31. The half nut mechanism 19 includes a pair of opposed half nuts 20 having concave and convex tooth portions, and advances and retreats with respect to the engaging portion 21 of the mechanical ram 37 of the movable platen 17. On the other hand, a cylindrical mechanical ram 37 is fixed at the center of the back surface of the movable platen 17 toward the pressure platen 23 side. On the cylindrical surface around the mechanical ram 37 that is a part of the movable platen 17, there is provided an engaging portion 21 in which a plurality of grooves that engage with the teeth of the half nut 20 are formed.

The injection device 13 is a well-known device and plasticizes resin pellets to form a molten resin. The molten resin is injected into a cavity C formed between the fixed mold 14 and the movable mold 16 by advancing a screw or the like. . The drive source of the injection device 13 may be electric or hydraulic, and may be injected by a plunger other than the screw. In some cases, the nozzle of the injection device 13 may be provided with a valve such as a shut-off valve. In the present embodiment, gas supply means 35 for supplying foaming gas such as nitrogen gas is provided to the heating cylinder of the injection device 13.

In this embodiment, the molding die attached to the mold clamping device 12 is called an inlay structure. Specifically, a cavity whose volume can be changed between the fixed mold 14 and the movable mold 16 by inserting the protruding core block 16 a of the movable mold 16 into the concave cavity block 14 a of the fixed mold 14. C is formed. A small gap is set between the side surface of the core block 14 a of the fixed mold 14 and the side surface of the core block 16 a of the movable mold 16, and the movable mold 16 moves relative to the fixed mold 14. Even the molten resin does not leak. In addition to the above-described inlay structure mold, a flat mold that allows the frame of the movable mold to move in the mold opening / closing direction relative to the core of the movable mold is used for the molding mold. May have been. In the case of the flat mold, the front surface of the frame part is in contact with the surface of the fixed mold, and a cavity with variable volume is formed by the cavity surface of the fixed mold, the inner cavity surface of the frame part, and the cavity surface of the core part. Is done.

The control device 38 of the injection molding machine 11 is connected to the servo motor 25 of the mold opening / closing mechanism 18 via the servo amplifier 41 (connection to one servo motor 25 is not shown in FIG. 1). A command signal is transmitted from the control device 38 to the servo amplifier 41. The control device 38 is connected to a load cell 40 that detects a retracting force of the movable platen 17 in the mold opening direction, and a signal (current value p1) detected by the load cell 40 is input to the control device 38. Yes. Further, the control device 38 is connected to the servo valve 34 via another servo amplifier 42, and a command signal of the servo valve 34 is transmitted from the control device 38 to the servo amplifier 42. The control device 38 is also connected to each valve of a hydraulic circuit (not shown), a drive source such as a servo motor of the injection device 13, a setting screen, and the like, so that the entire injection molding machine 11 is controlled. .

Next, the control method of the injection molding machine 11 of this embodiment is demonstrated. First, the servo motor 25 of the mold opening / closing mechanism 18 is actuated to advance the movable plate 17 and the movable mold 16 in the mold closing direction, and when the mold closing is completed, the tooth portion of the half nut 20 becomes the engagement portion 21 of the mechanical ram 37. Moving forward, the movable platen 17 and the mold clamping ram 31 of the mold clamping cylinder 29 are connected. Then, hydraulic oil is sent to the mold clamping side oil chamber 32a of the mold clamping cylinder 29 to complete the mold clamping, and a volume-variable cavity is formed between the cavity block 14a of the fixed mold 14 and the core block 16a of the movable mold 16. C is formed. On the other hand, the measurement of the molten resin is completed in the heating cylinder of the injection device 13 until the mold clamping is completed. At the time of the metering, a foaming gas such as nitrogen gas is supplied from the gas supply means 35 to the molten resin in the heating cylinder of the injection device 13, and the molten resin contains the foaming gas. In addition, the foaming method when performing foam molding in the cavity C is not limited to the above. For example, a foaming material may be introduced into the heating cylinder together with the material, or a foaming gas may be directly introduced into the nozzle portion or the cavity.

Next, as shown in the flowcharts of FIGS. 2 to 3, the screw of the injection device 13 is advanced to start injection of molten resin into the cavity C (S 1). On the other hand, since the pressure of the molten resin containing the foamed gas injected into the cavity C is lower in the cavity than in the heating cylinder, the foaming proceeds. The progress of foaming at this time slightly changes for each molding cycle due to variations in gas content and injection amount in the molten resin, and also changes during a single molding and becomes a factor of disturbance. Further, when the thermoplastic resin is used, the fixed mold 14 and the movable mold 16 are cooled, so that the molten resin in the cavity C is cooled and solidified from the portion that contacts the cavity surface of the mold.

From here, the foam core back control will be described. Next, it is detected whether or not the screw of the injection device 13 has advanced to reach the set core back start position (S2), and when it reaches, the first half of the movable back movement control (movable mold) of the core back control is detected. Reverse control) starts. The core back start position is preferably set to the holding pressure switching position or the position where the screw has advanced. However, the movable platen retreat control may be started using a timer measured from the start of injection, a resin pressure detection value in the cavity, or the like. When the completion of injection is detected first by means such as a timer different from the detection means for detecting the core back start position (S3), the core back start timer is started (S4) and the time is up. Start moving plate retreat control.

  Regarding the movable platen retreat control, first, mold clamping pressure relief is performed to reduce or temporarily reduce the pressure in the mold clamping side oil chamber 32a of the mold clamping cylinder 29 which is a hydraulic mechanism (S5). Next, the movable platen 17 and the like (including the movable mold 16) are moved from the start position t1 (mold side start position t1) in the mold opening direction. At that time, a command signal corresponding to a preset moving speed is sent from the control device 38 to the servo amplifier 41, the servo motor 25 is closed-loop controlled by speed control, and mold opening of the movable platen 17 and the like is started (S6). . In the present embodiment, the set speed of the movable platen 17 and the like is always a constant speed during the movable platen backward control section t3, but the set speed may be changed or the speed may be changed by a speed curve. Alternatively, the movable platen 17 may be stopped once or a plurality of times in the middle and the movable platen backward control is performed in multiple stages. In this case, the reverse speed may be constant or different. Therefore, moving the movable platen 17 or the like of the present invention in the mold opening direction by controlling the speed by the servo motor 25 includes a step of stopping halfway (or, in some cases, slightly moving forward). It is. The speed control of the servo motor 25 of the present invention is such that the target position is updated every unit time using a timer even if the position control is performed, and the substantial contents are similar to the speed control. Is also included.

During the movable platen retreat control, the mold clamping cylinder 29 performs a closed loop control that follows the speed control by the servo motor 25 of the mold opening / closing mechanism 18 as long as it is assumed that there is no influence of disturbance due to foam molding. . Since the movable platen retreat control is performed by the speed control of the servo motor 25, the movable platen 17 and the like can be moved at a speed substantially in line with the set reverse speed. In this embodiment, the mold clamping cylinder 29 presses the movable platen 17 and the like in the mold closing direction so that the movable platen 17 and the like are opposed to the force to open the mold by the foaming force of the molten resin in the cavity. In addition, low pressure hydraulic oil that works in the mold clamping direction is supplied to the mold clamping side oil chamber 32a. In addition, the contact between the tooth portion of the half nut 20 and the engaging portion 21 of the mechanical ram 37 is maintained as in the case of mold clamping. However, when the foaming force of the molten resin in the cavity C is weak, the mold clamping cylinder 29 is completely free from the beginning or midway (the pressing force by the hydraulic oil in the mold clamping side oil chamber 32a and the mold opening side oil chamber 32b is Closed loop control may be performed on the basis of a balanced state.

A retraction force in the mold opening direction of the movable platen 17 or the like during the movable platen reverse control (force transmitted from the movable platen 17 to the ball screw 26) is a load cell 40 provided between the movable platen 17 and the ball screw nut 27. (In this embodiment, half of the force is detected because one of the two is provided with the load cell 40), and is sent to the control device 38. Then, a load (current value p1) acting on the load cell 40 is compared with a preset mold opening force setting p2 (S7), and a command voltage is sent from the control device 38 to the servo amplifier 42 in a range of plus or minus 10 V, and the servo valve 34 The mold clamping cylinder 29 is closed-loop controlled by adjusting the output to. Specifically, when the load p1 detected by the load cell 40 is larger than the set value p2 of the mold opening force setting, it is determined that the load on the servo motor 25 or the ball screw mechanism is increased due to disturbance such as foaming force of the molten resin. Therefore, the output voltage of the command signal to the servo amplifier 42 that controls the servo valve 34 is increased (S8), and hydraulic oil is additionally supplied to the mold clamping side oil chamber 32a of the mold clamping cylinder 29, thereby the mold clamping side. The oil pressure of the oil chamber 32a is increased, and the pressing force in the mold closing direction of the movable platen 17 and the like is increased. As a result, the value of the load cell 40 that is the load of the servo motor 25 and the ball screw mechanism can be reduced. If the load p1 detected by the load cell 40 is equal to the set value p2 of the mold opening force setting, the output voltage of the command signal to the servo amplifier 42 that controls the servo valve 34 is maintained (S9). Further, when the load (current value p1) detected by the load cell 40 is lower than the set value p2 of the mold opening force setting, the output voltage of the command signal to the servo amplifier 42 that controls the servo valve 3 is decreased (S10). The amount of hydraulic fluid supplied to the mold clamping side oil chamber 32a of the mold clamping cylinder 29 is decreased or is set to 0, or the pressing force of the movable plate 17 and the like in the mold closing direction is lowered or set to 0 by the mold clamping cylinder 29.

In the movable platen backward movement control of the present invention, the speed control by the servo motor 25 is complemented by detecting the disturbance and performing the closed-loop control of the mold clamping cylinder 29 without increasing the load on the servo motor 25 and the ball screw mechanism. The movable platen 17 and the like can be moved substantially along the set speed control value. The control is continued during the movable platen backward control section t3 until the position of the movable platen 17 etc. reaches the core back setting stop position t2, and when the core back setting stop position t3 is reached (S11), the servo motor 25 is reached. The movable platen retreat control by the speed control by is stopped, and the movable platen 17 and the like are stopped by the position control by the servo motor 25 (die speed 0 mm / h) (S12).

Until the core back setting stop position t3 is reached, the volume of the molten resin in the cavity C continues to be expanded, and cooling and solidification sequentially proceeds from the portion in contact with the cavity C. At the stop position t3, the foam molded product has a predetermined shape, but the internal pressure in the cavity C is not 0 because the foaming force still remains in the foam molded product. Therefore, in this embodiment, cooling of the foamed molded product is continued while performing the second half movable platen stop control of the core back control. Since the movable platen stop control is performed using the position control of the servo motor 25, a foam molded product having an accurate thickness can be obtained.

The movable platen stop control will be described with reference to the flowchart of FIG. 3. In the movable platen stop control, the detection value (current value p1) of the load cell 40 at the time of mold stop is continuously sampled (S13), and the detection value p1 is the control device. 38. Then, the detection value (current value p1) of the load cell 40 is compared with the preset setting value p3 of the stopping force setting (S14), and when the detection value (current value p1) of the load cell 40 is larger than the setting value p3, Since it is determined that the load on the servo motor 25 and the ball screw mechanism is high, the output voltage of the command signal to the servo amplifier 42 that controls the servo valve 34 is increased (S15), and the mold clamping side of the mold clamping cylinder 29 is increased. The hydraulic oil is supplied to the oil chamber 32a to increase the hydraulic pressure of the mold clamping side oil chamber 32a, thereby increasing the pressing force of the movable platen 17 in the mold closing direction. When the load (current value p1) detected by the load cell 40 is equal to the set value p3 of the stop force setting, the output voltage of the command signal to the servo amplifier 42 that controls the servo valve 34 is maintained (S16). Further, when the load (current value p1) detected by the load cell 40 is lower than the set value p3 of the stop force setting, the output voltage of the command signal to the servo amplifier 42 that controls the servo valve 34 is decreased (S17). The amount of hydraulic oil supplied to the mold clamping side oil chamber 32a of the clamping cylinder 29 is decreased or is set to 0, and the pressing force of the movable plate 17 and the like in the mold closing direction is decreased or set to 0 by the mold clamping cylinder 29. The control is continued until the time of the cooling time timer is up (S18). When the time is up, the movable platen stop control in the foam core back control is also finished. At this time, the foamed molded product in the cavity C has been cooled and solidified. Then, hydraulic oil is supplied to the mold opening side oil chamber 32b of the mold clamping cylinder 29 from another hydraulic circuit to perform strong mold opening. Then, after releasing the locking of the half nut 20 on the mold clamping cylinder 29 side and the mechanical ram 37 on the movable board 17 side, the servo motor 25 of the mold opening / closing mechanism 18 is operated to move the movable board 17 and the movable mold 16. Is opened to the mold opening completion position (S19). Then, the foamed molded product that has been molded is taken out from the mold.

The foam core back control can be realized by a method other than using the load cell 40. In a mold clamping device of an injection molding machine according to another embodiment described below, the load cell 40 is not provided between the bracket 17 a of the movable platen 17 and the ball screw nut 27. During the reversing control of the movable platen, the retreating speed when the movable platen 17 is retreated with the speed controlled by the servo motor 25 of the mold opening / closing mechanism 18 is measured by the retreating speed detecting means and compared with the set retreating speed. Thus, the pressing force of the mold clamping cylinder 29 of the hydraulic mechanism is controlled. Further, during the subsequent movable platen stop control, the current value to the servo motor 25 is measured, and the current value is controlled to be constant.

With respect to the foam core back control without using the load cell 40, the foam core back control using the previous load cell 40 with reference to the flowchart of the control method of the injection molding machine of the foam molded product of another embodiment shown in FIGS. The difference from the control will be mainly described. Also for the foam core back control of the injection molding machine that does not use the load cell 40, the mold opening is started after the injection or during the injection (S106), and the movable plate 16 or the movable mold 16 is being controlled while the movable platen retract control is performed. The position of the movable platen 17 and the like is detected by the encoder 28 of the servo motor 25 which is a detecting means for detecting the moving speed of a part of the mold in the mold opening direction. At that time, the position of the movable platen 17 is sequentially transmitted to the control device 38, and the actual mold opening speed is calculated. Then, the mold opening speed preset in the controller 38 is compared with the actually measured mold opening speed (S107), and a command voltage is sent from the controller 38 to the servo amplifier 42 in the range of plus or minus 10V based on the comparison result. The output of the servo valve 34 is adjusted, and the mold clamping cylinder 29 is closed-loop controlled.

Specifically, when the measured mold opening speed v1 is faster than the set value v2 of the mold opening speed, the load on the servo motor 25 and the ball screw mechanism is increased due to disturbance such as foaming force. The output voltage of the command signal is increased (S108), hydraulic oil is supplied to the mold clamping side oil chamber 32a of the mold clamping cylinder 29 to increase the hydraulic pressure of the mold clamping side oil chamber 32a, and the mold closing direction of the movable platen 17 is increased. Increase the pressing force to. As a result, the mold opening speed of the movable platen 17 and the like can be reduced to reduce the load on the servo motor 25 and the ball screw mechanism. If the set value v2 of the mold opening speed is equal to the actually measured mold opening speed v1, the output voltage of the command signal to the servo valve 34 is maintained (S109). Further, when the measured mold opening speed v1 is slower than the mold opening speed set value v2, the output voltage of the command signal to the servo valve 34 is decreased (S10), and the mold clamping side oil chamber 32a of the mold clamping cylinder 29 is moved to. The hydraulic fluid supply amount is reduced or zero, and the pressing force of the movable plate 17 and the like in the mold closing direction is lowered by the mold clamping cylinder 29 or the mold opening speed of the movable plate 17 in the mold closing direction is reduced. Make it faster. When the core back setting stop position t3 is reached (S111), the movable platen backward control by the speed control by the servo motor 25 is stopped, and the movable plate 17 and the like are stopped by the position control by the servo motor 25 (die speed 0 mm / h). (S112).

  Next, movable platen stop control is performed as shown in the flowchart of FIG. In the movable platen stop control, the current value a1 of the servomotor 25 at the time of mold stop is continuously sampled by the current value detection means which is a detection means for detecting the load of the servomotor (S113), and the detected current value a1 is It is sent to the control device 38. Then, the detected current value a1 is compared with a predetermined current value a2 set in advance (S114). If the detected current value a1 of the servomotor 25 is larger than the set current value a2, the servomotor Since the load on the ball screw mechanism is increased, the output voltage of the command signal to the servo valve 34 is increased (S115). At this time, the current value a1 to the servo motor 25 is continuously sampled (S118). If the detected current value a1 is still higher than or equal to the predetermined current value a2 set in advance, the mold clamping is performed. The pressing force by the cylinder 29 exceeds the positioning force of the servo motor 25, and it is determined that the movable platen 17 and the like are closer to the mold closing side than the stop position and the servo motor 25 is overloaded. The output voltage of the command signal to the valve 34 is reduced (S119). If the detected current value a1 is lower than the preset predetermined current value a2, the process returns to (S114) until the time measured by the cooling time timer expires (S120), and the detected current value a1. And a predetermined current value a2 set in advance.

If the detected current value a1 is equal to the set current value a2, the output voltage of the command signal to the servo valve 34 is maintained (S116). If the set current value a2 is lower than the detected current value a1, the output voltage of the command signal to the servo valve 34 is decreased (S17), and the mold clamping cylinder 29 is supplied to the mold clamping side oil chamber 32a. The supply amount of the hydraulic oil is decreased or set to 0, and the pressing force of the movable plate 17 and the like in the mold closing direction is decreased or set to 0 by the mold clamping cylinder 29. The control is continued until the time of the cooling time timer is up (S120), and when the time is up, the movable platen stop control of the foam core back control is also finished. At this time, the foamed molded product in the cavity is cooled and solidified. Then, after releasing the engagement between the half nut 20 on the mold clamping cylinder 29 side and the engaging portion 21 of the mechanical ram 37 on the movable board 17 side, the servo motor 25 of the mold opening / closing mechanism 18 is operated to move the movable board 17 and The movable mold 16 is opened (S119). Then, the foamed molded product that has been foamed is taken out from the mold.

In the present invention, the foam core back control may be performed using detection values of the following detection means. That is, the load of the servo motor 25 of the mold opening / closing mechanism 18 at the time of moving plate retraction control is detected by measuring the current value and torque by the detecting means, and the current value and torque change due to a change due to disturbance. The hydraulic mechanism may be subjected to closed loop control. Alternatively, the fluid mechanism such as the hydraulic mechanism may be closed-loop controlled in response to a change in the command voltage value to the servo amplifier 41 that controls the servo motor 25 of the mold opening / closing mechanism 18 due to disturbance. Further, a resin pressure sensor, which is a detecting means for detecting the resin pressure in the cavity, may be mounted in the cavity, and the change in the resin pressure in the cavity depending on the foaming state may be measured to control the hydraulic mechanism in closed loop. Further, at least one detection value of these detection means may be combined and used for closed loop control of the fluid mechanism.

In the present invention, the preset speed set by the servo motor 25 of the mold opening / closing mechanism 18 may be changed by automatic correction or control during one molding cycle or every fixed molding cycle. Specifically, learning is performed when the load detected by the load cell 40 is larger than the set value of the mold opening force setting every time or frequently, or when the measured mold opening speed is faster than the set value of the mold opening speed. Depending on the function, the set speed of the servo motor 25 may be corrected so as to increase during the molding or from the next molding cycle. Conversely, when the load detected by the load cell 40 is smaller than the set value of the mold opening force setting every time or frequently, or when the measured mold opening speed is slower than the set value of the mold opening speed, the learning function is used. The setting speed by the servo motor 25 is corrected so as to be delayed during the molding or from the next molding cycle, or the pressing force applied by the hydraulic mechanism regardless of the closed loop control is reduced during the molding or from the next molding cycle. It may be modified to do so.

  Further, the present invention may be a foam molded product injection molding machine 51 of still another embodiment having a mechanism for moving the core block 64 as shown in FIG. In a mold clamping device 52 of an injection molding machine 51 for foamed molded products according to another embodiment, a fixed mold 54 is attached to the fixed plate 53, and a movable mold 56 is attached to the movable plate 55. A mold opening / closing mechanism 57 is provided between the fixed platen 53 and the movable platen 56. The mold opening / closing mechanism 57 and the mold clamping mechanism of the mold clamping device 52 may be of any type, and may be a toggle mechanism that can serve both as the mold opening / closing mechanism and the mold clamping mechanism. The movable plate 55 is provided with an electric core block moving device 58. The electric core block moving device 58 has a servo motor 59 attached to the back surface of the movable plate 55, and is fixed to the ball screw nut 61, the connecting plate 62, the rod 63, and the rod 63 by the rotation of the ball screw 60 connected by a pulley and a belt. The core block 64 thus moved moves in the mold opening / closing direction so that the volume of the cavity C1 can be changed. The core block 64 which is a part of the movable mold 56 constitutes a part or all of the cavity forming surface on the movable mold 56 side. The moving device 58 of the core block 64 by the servo motor 59 may be a modified ejector device. A cylinder 65 using a hydraulic mechanism is attached inside the movable plate 55 or the movable mold 56, and the rod of the cylinder 65 is fixed to the back surface of the core block 64. The cylinder 65 is connected to a closed-loop flow control valve such as a servo valve (not shown). Note that the fluid used in the cylinder 65 may be compressed air instead of hydraulic pressure, and the present invention is not limited to the hydraulic mechanism, and any fluid mechanism may be used. Although not shown, a resin pressure sensor may be attached to a cavity provided with a load cell between the core block 64 and the rod.

Further, the control method of the injection molding machine 51 of the foam molded product according to another embodiment is substantially the same as the embodiment shown in FIG. Molten resin is injected from the injection device 66 of the injection molding machine 51 into the cavity C1 formed between the fixed mold 54 and the movable mold 56, and the speed of the core block 64 is controlled by the servo motor 59 during or after injection. The foam core back control is started by moving the mold in the mold opening direction. The disturbance at that time is detected by the current value, torque, command value of the servo motor 59, the moving speed of the core block 64 (the encoder value of the servo motor 59), the load cell value, the detection value of the resin pressure sensor, or the like. Then, the detected value is sent to a control device (not shown), and a servo valve or the like connected to the cylinder 65, which is a hydraulic mechanism, is operated by a closed loop, particularly when the disturbance of the core block 64 in the mold opening direction is large. Is pressed in the mold closing direction so that the servo motor 59 is not overloaded and the ball screw mechanism including the ball screw 60 and the ball screw nut 61 is not overloaded.

  The molding material used for the control method of the injection molding machine of the present invention is not limited, and a plurality of resin materials may be used. In addition to foam molding, the present invention may be used for hollow molding or a combination of hollow molding and foam molding as long as the volume of the molded product is expanded in the cavity. In the case of hollow molding, a nozzle for injecting a gas such as nitrogen gas that forms a hollow portion in the nozzle or cavity is provided. Then, after the molten resin is injected into the cavity, the hollow portion is formed by filling the inside of the molded product with gas while delaying cooling and solidification in some cases. At the same time, the core block 53 which is a part of the movable mold 16 or the movable mold 52 is molded by a control method such as the flowchart shown in FIG. 2 to FIG. 3 or the flowchart shown in FIG. Move in the opening direction to enlarge the volume in the cavity. This makes it possible to form a hollow molded product with a clean surface abutting against the cavity.

11, 51 Injection molding machine 12, 52 Mold clamping device 13, 66 Injection device 14, 54 Fixed mold 15, 53 Fixed plate 16, 56 Movable mold 17, 55 Movable plate 18, 57 Mold opening / closing mechanism 25, 59 Servo motor 28 Encoder (detection means)
29 Clamping cylinder (fluid mechanism)
34 Servo valve 38 Control device 40 Load cell (detection means)
41, 42 Servo amplifier 64 Core block (part of movable mold)
C, C1 cavity

Claims (4)

During or after injection of molten resin into the cavity formed between the fixed mold and movable mold, the movable mold or a part of the movable mold is moved in the mold opening direction to expand the cavity volume and foam In a control method of an injection molding machine for molding a molded product or a hollow molded product,
When expanding the volume of the cavity, move the movable mold or part of the movable mold in the mold opening direction by controlling the speed with a servo motor,
A control method for an injection molding machine, wherein closed mold control of a movable mold or a part of a movable mold is performed by a fluid mechanism in response to a disturbance. Servo motor load, moving speed of movable mold or part of movable mold in mold opening direction, resin pressure in cavity, and retracting force of movable mold or part of movable mold in mold opening direction The method for controlling an injection molding machine according to claim 1, wherein at least one is detected and closed loop control of the fluid mechanism is performed. During or after injection of molten resin into the cavity formed between the fixed mold and movable mold, the movable mold or a part of the movable mold is moved in the mold opening direction to expand the cavity volume and foam In an injection molding machine for molding a molded product or a hollow molded product,
A servomotor that moves the movable mold or a part of the movable mold in the mold opening direction when expanding the volume of the cavity; and
An injection molding machine comprising: a movable mold or a fluid mechanism capable of pressing a part of the movable mold in a mold closing direction by closed loop control. Detection means for detecting the load of the servo motor, detection means for detecting the moving speed of the movable mold or a part of the movable mold in the mold opening direction, detection means for detecting the resin pressure in the cavity, and movable mold or The closed loop control of the fluid mechanism is performed according to a detection value of the detection means provided with at least one detection means for detecting a retraction force in a mold opening direction of a part of the movable mold. 3. An injection molding machine according to 3.