JP5404142B2 - Injection molding machine - Google Patents

Description

  The present invention relates to an injection molding machine suitable for injection molding of thin molded products.

  For example, for thin-walled molded products such as light guide plates and connection connectors, only the molded product is discharged from the mold, and the spool and runner are not discharged from the mold. A mold called a spool runnerless mold or a hot runner mold is used. Molding is performed using an injection molding machine provided. For this type of injection molding machine, it is particularly required to increase the injection speed of the molten resin into the mold cavity at the initial stage of the filling process. The reason for this is that if the injection speed of the molten resin is low at the initial stage of filling, the filling resin comes into contact with the mold cavity surface and is cooled to enlarge the skin layer formed on the surface of the filling resin. For relatively thick molded products with a thickness of 5 mm or more, defects such as sink marks and wrinkles occur on the surface, and for relatively thin molded products with a thickness of 0.1 mm to 0.5 mm, enter the mold cavity. This is because the inconvenience that filling of the molten resin becomes impossible is caused.

  The applicant of the present application has previously proposed an injection molding machine equipped with three electric servomotors for injection as an injection molding machine capable of increasing the injection speed of the molten resin into the mold cavity (see, for example, Patent Document 1). .) This injection molding machine can drive the injection device with the combined output of the electric servomotors for each injection, resulting in high injection speed and miniaturization of the individual injection electric servomotors. Since the inertia can be reduced by reducing the weight of the child, the start-up time until the desired high injection speed is reached can be shortened. For example, a very high injection speed of about 1000 mm / sec can be realized, and the actual startup time until the injection speed reaches 1000 mm / sec from the start of injection (injection speed 0) can be shortened to 0.0220 sec. .

  In addition, as an injection molding machine that can perform injection molding of thin molded products without increasing the injection speed of molten resin into the mold cavity, a hydraulic cylinder for holding pressure is driven after the injection is completed, and a heating cylinder That pressurizes the molten resin collected at the tip of the nozzle toward the nozzle side (see, for example, Patent Document 2), or drives the mold after completion of injection to press the filled resin (for example, Patent Document 2) 3) is proposed, but these injection molding machines cannot solve the disadvantages caused by the enlargement of the skin layer.

JP 2007-83600 A JP 2003-266506 A JP 2008-302686A

  The injection molding machine described in Patent Document 1 includes three electric servomotors for injection, which not only increases the number of parts and increases the cost, but also transmits the driving force of each electric servomotor for injection to the injection screw. This complicates the configuration of the timing belt, pulley, and the like, so that there is a problem that the installation space for the injection apparatus also increases. In addition, the injection molding machine described in Patent Document 1 can increase the injection speed of the molten resin into the mold cavity due to the performance of the injection electric servomotor. No consideration is given to the communication speed between the control device that controls and the motor driver circuit that generates and outputs the drive signal of the injection electric servomotor according to the control signal output from the control device, There is room for improvement in this regard.

  The present invention has been made in view of the actual situation of the prior art, and an object of the present invention is to control the injection speed of the molten resin into the mold cavity with high accuracy with an inexpensive and simple configuration. An object of the present invention is to provide an injection molding machine capable of molding a high-quality thin molded product.

  In order to solve the above-mentioned problems, the present invention firstly discharges a thin molded product having a thickness of 0.1 mm or more and 0.5 mm or less and having no spool and runner by injection-filling molten resin into the cavity. A mold, a screw arranged to be movable forward and backward relative to the mold, and injecting molten resin into the cavity when moving forward, an electric servomotor for injection that drives the screw forward and backward, and the electric servo for injection A control device that controls the motor drive and repeatedly executes a series of molding cycles including an injection filling process, and generates and outputs a drive signal of the electric servomotor for injection according to a control signal output from the control device In the injection molding machine provided with a motor driver circuit that performs, as the electric servomotor for injection, one multi-turn three-phase motor is used, and from the control device As the communication line for transmitting the control signal to the serial motor driver circuit, and the configuration of using a material having a higher communication speed 100Mbps.

  A multi-winding three-phase motor is a winding of a plurality of U-phase, V-phase, and W-phase windings having a phase angle of 120 degrees with each other, and is driven by a motor driver circuit provided for each of the windings. As a result, a large output torque can be obtained with a small size. The output torque of this multi-turn three-phase motor varies depending on the motor drive current supplied from the motor driver circuit. When a motor drive current greater than the rated current is supplied to the multi-turn three-phase motor, a torque greater than the rated torque is required. When a motor drive current less than the rated current is supplied to the multi-turn three-phase motor, a torque less than the rated torque can be outputted. However, when driving a multi-turn three-phase motor with an output torque greater than the rated torque, an adverse effect due to heat generation occurs, so the drive time is limited to a short time. In general, a multi-turn three-phase motor can be driven for a maximum torque of 0.3 seconds to 0.5 seconds, so that only a single multi-turn three-phase motor with a relatively low rated torque is used. Time injection filling process can be performed. Further, when the output torque of the multi-turn three-phase motor is reduced after the injection filling process is completed, the driving time of the multi-turn three-phase motor can be extended according to the reduction, so that the multi-winding with a relatively low rated torque. By using only one three-phase motor, a high pressure and long pressure holding process can be executed. Therefore, an injection molding machine that uses one multi-winding three-phase motor as an electric servomotor for injection reduces the size and cost of the injection molding machine by reducing the number of motors and the number of mechanisms that accompany it. It is possible to improve the performance of the injection molding machine by use.

In addition, when a communication line that transmits a control signal from the control device to the motor driver circuit is used with a communication speed of 100 Mbps or more, when the control signal message configuration is 8 bits, 0.08 μsec (1/125 × 10 ³ sec) unit control is possible, so that the drive control of the servo motor for injection is sufficiently accurate even when the start-up time from the start of injection to the predetermined injection speed is as short as 0.0220 sec. Therefore, it is possible to prevent molding defects due to enlargement of the skin layer. Therefore, a thin molded product having a thickness of 0.1 mm or more and 0.5 mm or less can be molded with high accuracy.

  In the present invention, secondly, a multi-turn three-phase motor having a maximum torque of 400% to 500% of the rated torque is used as the electric servomotor for injection.

  Thus, when a multi-turn three-phase motor having a maximum torque of 400% or more and 500% or less of the rated torque is used, an injection molding machine with a higher rank is used by using a small multi-turn three-phase motor having a relatively low rated torque. Since the same injection filling process and pressure holding process can be performed, the cost and size of the injection molding machine can be further reduced.

  Since the injection molding machine of the present invention uses only one multi-turn three-phase motor as an electric servomotor for injection, it is possible to obtain a high injection speed while reducing the size and cost. Further, since a communication line for transmitting a control signal from the control device to the motor driver circuit is used which has a communication speed of 100 Mbps or more, the injection servo motor within the start-up time from the start of injection until the predetermined injection speed is reached. Can be controlled with high accuracy. Therefore, molding defects due to enlargement of the skin layer can be prevented, and a thin molded product having a thickness of 0.1 mm or more and 0.5 mm or less can be molded with high accuracy.

It is a principal part block diagram of the injection molding machine which concerns on embodiment. It is an output characteristic figure of the electric servomotor for injection with which the injection molding machine concerning an embodiment is equipped. It is a graph which shows drive control of the servomotor for injection in the starting time from the injection start of the injection molding machine which concerns on embodiment until it reaches a predetermined injection speed.

  Hereinafter, an embodiment of an injection molding machine according to the present invention will be described with reference to FIGS. 1 to 3. As shown in FIG. 1, the injection molding machine of this example includes a head stock 1 and a motor mounting plate 2 which are disposed on a base board (not shown) opposite to each other at a predetermined distance, and the head stock 1 and the motor mounting plate. A linear motion block 3 that moves forward and backward between 2, a screw shaft 5 that is rotatably held on the motor mounting plate 2 via a bearing 4, and a ball screw mechanism 7 that includes a nut body 6 screwed into the screw shaft 5; A heating cylinder 8 attached to the headstock 1, a screw 9 which is rotatably and reciprocally housed in the heating cylinder 8, and has one end attached to the linear motion block 3, and attached to the outer surface of the motor mounting plate 2. , An injection electric servomotor 10 that rotationally drives the screw shaft 5, and a metering electric servomotor 20 that is attached to the linear motion block 3 and rotationally drives the screw 9. Moreover, the injection molding machine of this example is a fixed side mold 31 and a movable side mold 32 for molding a molten resin injected from a nozzle 8a provided at the tip of the heating cylinder 8, and the entire drive of the injection molding machine. And a control device 40 that executes a series of molding cycles including mold closing, injection filling, pressure holding, mold opening, and product extrusion, and an electric servomotor 10 for injection corresponding to a control signal output from the control device 40 And a motor driver circuit 41 that outputs a driving signal for the electric servomotor 20 for weighing. The control device 40 and the motor driver circuit 41 are connected via a communication line 42 having a communication speed of 100 Mbps or higher. Examples of this type of communication line 42 include Ethernet (registered trademark) and EtherCAT (registered trademark).

  A cavity 33 having a predetermined shape is formed at the interface between the fixed side mold 31 and the movable side mold 32. The fixed side mold 31 includes a nozzle contact portion 34 and the nozzle contact portion 34 toward the cavity 33 side. An extending spool 35 and a runner 36 that connects the tip of the spool 35 and the cavity 33 are formed. As the mold apparatus according to the present embodiment, only the molded product formed by the cavity 33 is discharged from the mold, and the spool 35 and the runner 36 are not discharged from the mold. A mold apparatus called “etc.” is used. The details thereof are matters that belong to the public domain and are not the gist of the present invention, so that the description thereof is omitted. The cavity 33 can be formed in any shape and size, but the present invention can be applied to a thin molded product having a thickness of 0.1 mm or more and 0.5 mm or less, such as a light guide plate or a connection connector. This is particularly effective when molding.

  The electric servomotor 10 for injection includes a casing 11, a cylindrical motor stator 13 fixed to the inner surface of the casing 11, a motor coil 14 wound around the outer periphery of the motor stator 13, and the motor stator 13 A cylindrical motor rotor 15 disposed on the motor rotor 16, a motor magnet 16 attached to the outer surface of the motor rotor 15, and a bearing 17 that rotatably supports the motor rotor 15 and the motor magnet 16 on the casing 11. The rotation of the motor rotor 15 is transmitted to the screw shaft 5 by fitting the screw shaft 5 to the inner periphery of the motor rotor 15. The injection electric servo motor 10 is fastened to the back side of the motor mounting plate 2 by a bolt (not shown).

  As shown in FIG. 2, the electric servomotor 10 for injection has a maximum torque that can be output is 400% to 500% of the rated torque, and a drive time that can be driven with the maximum torque is 0.3 to 0.5 seconds. A certain multi-turn three-phase motor is used. In addition, the multi-turn three-phase motor is a motor driver provided for each of the multiple windings of the U-phase, V-phase, and W-phase windings having a phase angle of 120 degrees. Since it can be driven by the circuit 41, a large output torque can be obtained with a small size.

  The electric servomotor 20 for measurement includes a casing 21, a cylindrical motor stator 22 fixed to the inner surface of the casing 21, a motor coil 23 wound around the outer periphery of the motor stator 22, and the motor stator 22. A bottomed cylindrical motor rotor 24, a motor magnet 25 attached to the outer surface of the motor rotor 24, and a bearing 26 that rotatably supports the motor rotor 24 and the motor magnet 25 on the casing 21. It is composed of A spline hole 24a is formed at the bottom of the motor rotor 24. By inserting the spline 9a formed at the tip of the screw 9 into the spline hole 24a, the rotation of the motor rotor 24 is controlled by the screw 9. To communicate. Further, the nut body 6 of the ball screw mechanism 7 is strongly fitted to the other end side of the motor rotor 24, and the linear motion block 3, the measuring servo motor 20, The screw 9 is guided by the guide rail 30 and moves forward and backward integrally.

  In the injection molding machine of this example configured as described above, when the electric servomotor 20 for metering is rotated in a predetermined direction from the control device 40 via the motor driver circuit 41, the rotation of the motor rotor 24 is caused by the spline holes 24a and 24a. It is transmitted to the screw 9 via the spline 9a, and the screw 9 rotates at a predetermined rotational speed. As a result, the molding material is supplied from a hopper (not shown), and the molding material is plasticized, kneaded and metered in the heating cylinder 8. Further, when the injection electric servo motor 10 is rotationally driven in a predetermined direction from the control device 40 via the motor driver circuit 41, the rotational motion is transmitted to the screw shaft 5 of the ball screw mechanism 7, and the rotational motion of the screw shaft 5 is transmitted to the nut. It is converted into the forward movement of the body 6, and the linear motion block 3, the metering servo motor 20 and the screw 9 advance together. Thereby, injection of the molten resin from the nozzle 8a into the mold cavity 33 is performed.

  In the injection process performed by rotationally driving the injection servo motor 10 in a predetermined direction, when forming a thin molded product having a thickness of 0.1 mm or more and 0.5 mm or less, molding defects due to enlargement of the skin layer 3, a very high injection speed of about 1000 mm / sec is required as shown in FIG. 3, and the injection speed is 1000 mm / sec, which is the target injection speed from the start of injection (injection speed 0). It is required to set the start-up time until reaching to 0.0220 sec. As described above, as the electric servomotor for injection 10, the maximum torque that can be output is 400% to 500% of the rated torque, and the driving time that can be driven with the maximum torque is 0.3 to 0.5 seconds. When a three-phase motor is used, a large output torque can be obtained with a small size, so that an injection speed of about 1000 mm / sec can be achieved, and the start-up time from the start of injection until the injection speed reaches the target injection speed is 0.0220 sec. Can be about. In this case, when the control device 40 and the motor driver circuit 41 are connected via the communication line 42 having a communication speed of 100 Mbps or more, the message configuration of the control signal output from the control device 40 is 8 bits. In this case, since the drive control of the injection electric servomotor 10 can be performed in units of 0.08 μsec, the injection electric motor can be used even when the start-up time from the start of injection to the predetermined injection speed is as short as 0.0220 sec. The drive control of the servo motor 10 can be performed with sufficiently high accuracy, and molding defects due to enlargement of the skin layer can be prevented.

  The present invention can be used for an injection molding machine used for injection molding of a thin molded product.

DESCRIPTION OF SYMBOLS 1 Headstock 2 Motor mounting plate 3 Linear motion block 7 Ball screw mechanism 8 Heating cylinder 8a Nozzle 9 Screw 10 Electric servo motor for injection 20 Electric servo motor for metering 31 Fixed mold 32 Movable mold 33 Cavity 35 Spool 36 Runner 40 Control device 41 Motor driver circuit 42 Communication line

Claims (2)

By injecting and filling molten resin into the cavity, a mold that discharges a thin molded product that has a thickness of 0.1 mm to 0.5 mm and does not have a spool and runner, and can be moved forward and backward relative to the mold And a series of moldings including an injection filling process that controls the drive of the injection servo motor for injecting the molten resin into the cavity during advance, the injection servo motor for driving the screw forward and backward, and the injection servo servo motor. In an injection molding machine comprising a control device that repeatedly executes a cycle, and a motor driver circuit that generates and outputs a drive signal of the electric servomotor for injection according to a control signal output from the control device,
As the electric servomotor for injection, one multi-turn three-phase motor is used, and a communication line for transmitting the control signal from the control device to the motor driver circuit has a communication speed of 100 Mbps or more. Characteristic injection molding machine.   The molding machine according to claim 1, wherein a multi-turn three-phase motor having a maximum torque of 400% to 500% of a rated torque is used as the electric servomotor for injection.

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