TWI668093B - Injection molding machine - Google Patents

Abstract

The present invention provides an injection molding machine capable of suppressing an increase in temperature of a specific phase of a motor. An injection molding machine according to the present invention includes: an AC motor that drives a movable portion; and a controller that controls a speed command value associated with the movable portion, an actual speed value associated with the movable portion, and a protection command for changing a current phase of the AC motor Value to control the aforementioned AC motor.

Description

Injection molding machine

The present application claims priority based on Japanese Patent Application No. 2015-015965, filed on Jan. 29, 2015. The entire contents of this Japanese application are incorporated herein by reference.

The present invention relates to an injection molding machine.

The injection molding machine has a movable portion and an AC motor that drives the movable portion (see, for example, Patent Document 1). As the AC motor, for example, a synchronous motor can be cited.

(previous technical literature) (Patent Literature)

Patent Document 1: Japanese Patent Publication No. 2011-183705

The controller controls the AC motor based on the speed command value of the movable portion and the actual speed value of the movable portion. The rotor of the AC motor rotates following a rotating magnetic field formed by AC power.

However, when the movable portion is driven in a state where the speed of the movable portion is substantially zero during the pressure holding or the mold clamping, the rotor hardly rotates. Therefore, the current is concentrated to one phase, and the temperature of the phase rises.

The present invention has been made in view of the above circumstances, and a main object thereof is to provide an injection molding machine capable of suppressing an increase in temperature of a specific phase of a motor.

In order to solve the above problems, an aspect of the present invention provides an injection molding machine including: an AC motor that drives a movable portion; and a controller that is related to the movable portion according to a speed command value associated with the movable portion The AC motor is controlled by an actual speed value and a protection command value that changes the current phase of the AC motor.

According to an aspect of the present invention, an injection molding machine capable of suppressing temperature rise of a specific phase of a motor can be provided.

10‧‧‧Molding device

12‧‧‧Fixed platen

13‧‧‧ movable platen

18‧‧‧Molding force detector

21‧‧‧Moulding motor

21a‧‧‧Encoder for clamping motor

30‧‧‧Molding device

32‧‧‧Fixed mode

33‧‧‧ movable mold

40‧‧‧Injection device

41‧‧‧Cylinder block

42‧‧‧Nozzles

43‧‧‧ screw

46‧‧‧Injection motor

46a‧‧‧Encoder for injection motor

90, 90A‧‧‧ controller

91, 91A‧‧‧ Pressure Detection Department

93, 93A‧‧‧ Speed Detection Department

94, 94A‧‧‧Speed Command Computing Department

95, 95A‧‧‧Control Command Computing Department

96, 96A‧‧‧ Drive Department

97A‧‧‧Filter Department

Fig. 1 is a view showing an injection molding machine according to an embodiment of the present invention.

Fig. 2 is a view showing a control system of an injection molding machine according to an embodiment of the present invention.

Fig. 3 is a view showing a modification of the control system shown in Fig. 2.

In the following, the embodiments for carrying out the invention will be described with reference to the accompanying drawings, wherein the same or corresponding components are designated by the same or corresponding elements, and the description is omitted.

Fig. 1 is a view showing an injection molding machine according to an embodiment of the present invention. The injection molding machine shown in Fig. 1 has a frame Fr, a mold clamping device 10, an injection device 40, a controller 90, and the like.

First, the mold clamping device 10 will be described. In the description of the mold clamping device 10, the moving direction of the movable platen 13 at the time of mold closing (the right direction in the first drawing) is set to the front, and the moving direction of the movable platen 13 at the time of mold opening (the first drawing) The left direction is set to the rear for explanation.

The mold clamping device 10 performs mold closing, mold clamping, and mold opening of the mold device 30. The mold clamping device 10 has a fixed platen 12, a movable platen 13, a rear platen 15, a tie rod 16, a toggle mechanism 20, a mold clamping motor 21, and a motion conversion mechanism 25.

The fixed platen 12 is fixed to the frame Fr. A fixed die 32 is attached to a surface of the fixed platen 12 that faces the movable platen 13.

The movable platen 13 is freely movable along a guide (for example, a guide rail) 17 laid on the frame Fr, and is movable forward and backward with respect to the fixed platen 12. A movable mold 33 is attached to a surface of the movable platen 13 that faces the fixed platen 12.

The mold closing, the mold clamping, and the mold opening are performed by moving the movable platen 13 forward and backward with respect to the fixed platen 12. The mold is assembled by the fixed mold 32 and the movable mold 33 Set to 30.

The rear pressure plate 15 is coupled to the fixed pressure plate 12 at intervals, and is movably placed on the frame Fr in the mold opening and closing direction. Further, the rear platen 15 may be configured to be movable along a guide laid on the frame Fr. The guide of the rear platen 15 may also be a guide shared with the guide 17 of the movable platen 13.

Further, in the present embodiment, the fixed pressure plate 12 is fixed to the frame Fr, and the rear pressure plate 15 is movable in the mold opening and closing direction with respect to the frame Fr. However, the rear pressure plate 15 may be fixed to the frame Fr, and the fixed pressure plate 12 may be fixed with respect to the frame Fr. It moves freely in the mold opening and closing direction.

The tie rod 16 connects and fixes the pressure plate 12 and the rear pressure plate 15 with a space therebetween. The tie rod 16 can use a plurality of roots. Each of the tie bars 16 is parallel to the mold opening and closing direction and extends by the mold clamping force. A mold clamping force detector 18 is disposed on at least one of the tie bars 16. The mold clamping force detector 18 can be a strain ritual that detects the clamping force by detecting the strain of the tie rod 16.

In addition, the mold clamping force detector 18 is not limited to the strain ceremony, and may be a piezoelectric type, a capacitive type, a hydraulic type, an electromagnetic type, or the like, and the mounting position thereof is not limited to the tie rod 16.

The toggle mechanism 20 is disposed between the movable platen 13 and the rear platen 15. The toggle mechanism 20 is composed of a crosshead 20a, a plurality of links 20b, 20c, and the like. The link 20b on one side is swingably attached to the movable platen 13, and the link 20c on the other side is swingably attached to the rear platen 15. These links 20b and 20c are connected by expansion and contraction by a pin or the like. By advancing and retracting the crosshead 20a, the plurality of links 20b, 20c are expanded and contracted, and the movable platen 13 is opposed to The rear platen 15 advances and retreats.

The mold clamping motor 21 is attached to the rear pressure plate 15, and the movable platen 13 is advanced and retracted by advancing and retracting the crosshead 20a. Between the mold clamping motor 21 and the crosshead 20a, a motion conversion mechanism 25 that converts the rotational motion of the mold clamping motor 21 into a linear motion and transmits it to the crosshead 20a is provided. The motion converting mechanism 25 is constituted by, for example, a ball screw mechanism. The speed of the crosshead 20a is detected by the encoder 21a of the mold clamping motor 21 or the like.

The action of the mold clamping device 10 is controlled by the controller 90. The controller 90 controls the mold closing process, the mold clamping process, the mold opening process, and the like.

In the mold closing process, the movable platen 13 is moved by driving the mold clamping motor 21, and the movable mold 33 is brought into contact with the fixed mold 32.

In the mold clamping process, the mold clamping force can be generated by further driving the mold clamping motor 21. When the mold is closed, a cavity space 34 is formed between the movable mold 33 and the fixed mold 32, and the cavity space 34 is filled with a liquid molding material. The molding material in the cavity space 34 is solidified to be a molded article.

In the mold opening process, the movable mold plate 13 is moved away from the fixed mold 32 by driving the mold clamping motor 21 to retract the movable platen 13.

Further, the mold clamping device 10 of the present embodiment has the mold clamping motor 21 as a drive source, but may have a hydraulic cylinder instead of the mold clamping motor 21. Further, the mold clamping device 10 may have a mold opening and closing linear motor and a mold clamping electromagnet.

Next, the injection device 40 will be described. In the description of the injection device 40, unlike the description of the mold clamping device 10, the moving direction of the screw 43 at the time of filling (the left direction in the first drawing) is set to the front, and the screw at the time of measurement is used. The moving direction of the rod 43 (the right direction in FIG. 1) will be described as the rear.

The injection device 40 is provided on the slide base Sb that is retractable with respect to the frame Fr, and is movable forward and backward with respect to the mold device 30. The injection device 40 is in contact with the mold device 30 to fill the molding material into the mold device 30. The injection device 40 includes, for example, a cylinder 41, a nozzle 42, a screw 43, a metering motor 45, an injection motor 46, and a pressure detector 47.

The cylinder 41 heats the molding material supplied from the supply port 41a. The supply port 41a is formed at the rear of the cylinder 41. A heating source such as a heater is provided on the outer circumference of the cylinder 41.

The nozzle 42 is provided at the front end portion of the cylinder 41 and is pressed against the mold device 30.

The screw 43 is a movable portion that is disposed in the cylinder 41 so as to be retractable. The screw 43 is rotatable in the cylinder 41.

The screw 43 is rotated by the measuring motor 45, and the molding material is sent forward along the spiral groove of the screw 43. The molding material is gradually melted by the heat from the cylinder 41 while being sent forward. As the liquid molding material is sent to the front of the screw 43, it is accumulated in the front portion of the cylinder 41, and the screw 43 is moved backward.

The injection motor 46 is an AC motor that advances and retracts the screw 43. The AC motor is a 3-phase AC motor, but it can also be a 2-phase AC motor. The injection motor 46 advances the screw 43 to fill the cavity forming space 34 of the mold device 30 with the liquid molding material accumulated in front of the screw 43. Thereafter, the injection motor 46 pushes the screw 43 forward to form a molded material in the cavity space 34. The material is applied with pressure. Can supplement an insufficient amount of forming material. Between the injection motor 46 and the screw 43, a motion conversion mechanism that converts the rotational motion of the injection motor 46 into a linear motion of the screw 43 is provided.

The pressure detector 47 is disposed between, for example, the injection motor 46 and the screw 43, and detects the pressure that the screw 43 receives from the molding material, the back pressure to the screw 43, and the like. The pressure that the screw 43 receives from the molding material corresponds to the pressure acting on the molding material from the screw 43.

The action of the injection device 40 is controlled by the controller 90. The controller 90 controls the filling process, the pressing process, the metering process, and the like.

In the filling process, the injection motor 46 is driven to advance the screw 43 at the set speed, and the liquid molding material accumulated in front of the screw 43 is filled into the mold device 30. The position and speed of the screw 43 are detected by, for example, the encoder 46a of the injection motor 46. When the position of the screw 43 reaches a predetermined position, switching from the filling process to the holding process (so-called V/P switching) is performed.

Further, in the filling process, after the position of the screw 43 reaches a predetermined position, the screw 43 is temporarily stopped at the predetermined position, and then V/P switching may be performed. Instead of the stop of the screw 43, the micro speed advancement or the reverse speed of the screw 43 may be performed before the V/P switching.

In the holding process, the drive injection motor 46 pushes the screw 43 forward at a set pressure to apply pressure to the molding material in the mold device 30. Can supplement an insufficient amount of forming material. The pressure of the forming material is detected by, for example, a pressure detector 47. After the press process, the cooling process begins. In the cooling process, the solidification of the molding material in the cavity space 34 is performed. Can also be cold However, the measurement process is carried out in the process.

In the metering process, the metering motor 45 is driven to rotate the screw 43 at a set number of revolutions, and the molding material is sent forward along the spiral groove of the screw 43. The molding material is gradually melted along with this. As the liquid molding material is sent to the front of the screw 43, it is accumulated in the front portion of the cylinder 41, and the screw 43 is moved backward. The number of revolutions of the screw 43 is detected by, for example, the encoder 45a of the metering motor 45.

In the metering process, in order to restrict the sudden retreat of the screw 43, the injection motor 46 can be driven to apply the set back pressure to the screw 43. The back pressure for the screw 43 is detected by, for example, the pressure detector 47. When the screw 43 is retracted to a predetermined position and a predetermined amount of the molding material is accumulated in front of the screw 43, the measuring process is completed.

Next, the controller 90 will be described. The controller 90 is constituted by a microcomputer or the like, and controls the mold clamping device 10 and the injection device 40 by causing a CPU (Central Processing Unit) to execute a program stored in a memory medium such as a memory.

Fig. 2 is a view showing a control system of an injection molding machine according to an embodiment of the present invention. The controller 90 includes a pressure detecting unit 91, a speed detecting unit 93, a speed command calculating unit 94, a control command calculating unit 95, a driving unit 96, and the like.

The pressure detecting unit 91 detects the actual pressure value P of the screw 43. The actual pressure value P of the screw 43 corresponds to the actual pressure value of the forming material, and is detected using, for example, the pressure detector 47.

The speed detecting unit 93 detects the actual speed value V of the screw 43. Screw 43 The actual speed value V corresponds to the actual rotational speed value of the injection motor 46, and is detected using, for example, the encoder 46a of the injection motor 46.

Here, the speed associated with the screw 43 is a positive speed when the screw 43 is advanced, and a negative speed when the screw 43 is retracted.

The speed command calculation unit 94 calculates the speed command value based on the pressure command value Pref and the actual pressure value P. For example, the speed command calculation unit 94 calculates the speed command value Vref such that the deviation between the pressure command value Pref and the actual pressure value P becomes zero. The calculation of the speed command value Vref uses, for example, a PI operation, a PID calculation, or the like.

The control command computing unit 95 generates an output wave of the drive unit 96 based on the speed command value Vref and the actual speed value V. For example, the control command computing unit 95 generates an output wave of the drive unit 96 such that the deviation between the speed command value Vref and the actual speed value V becomes zero. The generation of the output wave of the drive unit 96 is performed by, for example, PI calculation, PID calculation, or the like. The control command computing unit 95 generates a PWM (Pulse Width Modulation) signal by comparing the output wave of the drive unit 96 with the carrier.

Further, although the control command computing unit 95 of the present embodiment generates a PWM signal, it may generate a PAM (Pulse Amplitude Modulation) signal. The control method of the drive unit 96 is not particularly limited.

The drive unit 96 is configured by an inverter or the like that converts direct current power into alternating current power. The inverter has a plurality of bridge arms composed of, for example, two switching elements. The diode is anti-parallel to each switching element. The diode can also be built in each switching element. The inverter converts based on the PWM signal from the control command computing unit 95, and supplies the alternating current to the injection motor 46.

Further, in the holding process, the injection motor 46 is driven to push the screw 43 forward at a set pressure, and pressure is applied to the molding material in the mold device 30. In the holding process, the injection motor 46 may be driven in a state where the actual speed value V is substantially zero.

When the control command calculation unit 95 generates the PWM signal based on only the speed command value Vref and the actual speed value V, if the actual speed value V is within the predetermined range including zero, the injection motor 46 hardly rotates, so the current is concentrated to the injection. One phase of the motor 46 is used.

Then, the control command computing unit 95 generates a PWM signal based on the speed command value Vref, the actual speed value V, and the protection command value Vpc when the actual speed value V is within a predetermined range including zero. The protection command value Vpc is a value that changes the phase of the current of the injection motor 46, and is a value that changes the rotation angle of the injection motor 46. The protection command value Vpc can be used, for example, by reading a value stored in a memory medium such as a memory. By using the protection command value Vpc, it is possible to suppress the concentration of current to one phase of the injection motor 46, and it is possible to suppress the temperature rise of the specific phase of the injection motor 46.

Further, the protection command value Vpc may be used instead of reading a value stored in the memory medium, for example, switching the amount of change at a predetermined time interval.

When the motor 46 is forcibly rotated, the protection command value Vpc is not calculated by adding the pressure command value Pref or the actual pressure value P, but to the speed command value Vref or the actual speed value V, in order to control the rotation with high precision. Plus calculation.

In order to effectively suppress the concentration of the injection current to one phase of the motor 46, the protection command value Vpc can be made to have an electrical angle of each phase of the injection motor 46. The degree changes by about 10°~90°. The direction of the change may be either the direction in which the current phase is advanced, or the direction in which the current phase is shifted backward, or both directions.

The protection command value Vpc may be, for example, a command value that periodically changes the phase of the current of the injection motor 46, or a command value that periodically changes the rotation angle of the injection motor 46. The waveform of the protection command value Vpc may be, for example, any one of a sine wave, a rectangular wave, a triangular wave, and the like. By periodically changing the phase of the current of the injection motor 46, the position of the screw 43 can be vibrated, and the time average value of the actual pressure value P can be maintained at the pressure set value. The vibration center position of the screw 43 is, for example, a position at which the actual pressure value P is equal to the pressure set value.

The fluctuation of the actual pressure value P is slower than the positional change of the screw 43. The protection command value Vpc can periodically change the current phase of the injection motor 46 at a cycle shorter than the time difference. The change in the position of the screw 43 hardly causes a change in the actual pressure value P. The frequency of the protection command value Vpc can be obtained by a test or the like so that the instantaneous value of the actual pressure value P is within ±10% of the pressure command value Pref.

When the protection command value Vpc is periodically changing the phase of the current of the injection motor 46, the protection command value Vpc may be used when the actual speed value V is outside the predetermined range, or the speed command value Vref or the actual speed may be always used. The value V is added for calculation. This is because the time average value of the actual pressure value P can be maintained at the pressure set value. In particular, when the instantaneous value of the actual pressure value P is within the range of ±10% of the pressure command value Pref, the protection command value Vpc may always be the speed command value Vref or The sum is calculated on the velocity value V.

Further, the protection command value Vpc may be a value that advances only the phase of the current of the injection motor 46, or a value that only moves back. In this case, the protection command value Vpc is only used when the actual speed value V is within the above-described predetermined range, and cannot be used when the actual speed value V is outside the predetermined range. It is also possible to use the speed command value Vref instead of the actual speed value V.

Further, the protection command value Vpc may be used only when the actual speed value V is within the above-described predetermined range and the pressure command value Pref is equal to or greater than a predetermined value. When the pressure command value Pref is equal to or greater than a predetermined value, a large current flows, so that a remarkable effect of suppressing current concentration can be obtained. Instead of the pressure command value Pref, the actual pressure value P, the current value of the injection motor 46, and the like can be used. It is also possible to use the speed command value Vref instead of the actual speed value V.

Fig. 3 is a view showing a modification of the control system shown in Fig. 2. The controller 90A includes a filter unit 97A in addition to the pressure detecting unit 91A, the speed detecting unit 93A, the speed command calculating unit 94A, the control command calculating unit 95A, and the driving unit 96A.

The filter unit 97A attenuates a component of at least a predetermined frequency of the actual pressure value P. The predetermined frequency is the frequency of the protection command value Vpc. The fluctuation of the actual pressure value P caused by the protection command value Vpc can be removed. The filter unit 97A is constituted by, for example, a low-pass filter, and attenuates components of a frequency higher than the cutoff frequency. The cutoff frequency of the low pass filter is lower than the frequency of the protection command value Vpc. Further, the filter unit 97A may be constituted by a band rejection filter. The type of the filter is not particularly limited.

The speed command calculation unit 94A calculates the speed command value Vref based on the value obtained by attenuating the component of at least the predetermined frequency of the actual pressure value P and the pressure command value Pref. The speed command calculation unit 94A can remove the fluctuation of the actual pressure value P caused by the protection command value Vpc to calculate the speed command value Vref. Thereby, the time average value of the actual pressure value P can be stably maintained at the pressure set value.

Although the embodiment of the injection molding machine has been described above, the present invention is not limited to the above embodiment, and various modifications and improvements can be made within the scope of the invention as described in the claims.

For example, although the injection device of the above embodiment is a coaxial screw system, it may be a pre-molding method. The injection molding apparatus of the pre-molding method supplies the molding material melted in the plasticizing cylinder to the shooting cylinder, and the molding material is ejected from the shooting cylinder into the mold device. The screw is rotatably or rotatably disposed in the plasticizing cylinder, and the plunger is retractably disposed in the shooting cylinder. In the case where the injection device is a pre-molding method, in the second and third figures, a plunger is used instead of the screw 43. Instead of the injection motor 46, an AC motor that advances and retracts the plunger is used.

Further, the controller 90 shown in FIG. 2 and the controller 90A shown in FIG. 3 are used for the control of the AC motor of the injection device 40, but can also be used for the control of the AC motor of the mold clamping device 10, and the ejector device. Control of the AC motor, control of the AC motor of the die compression device, control of the AC motor of the injection device moving device, and the like.

The mold clamping device 10 has a crosshead 20a as a movable portion and serves as a cross The motor 21 for mold clamping of the flow motor. The actual speed value of the crosshead 20a corresponds to the actual rotational speed value of the mold clamping motor 21, and is detected using, for example, the encoder 21a of the mold clamping motor 21. The actual pressure value of the crosshead 20a corresponds to the actual value of the clamping force, and is detected using, for example, the mold clamping force detector 18. In the mold clamping process, the controller drives the mold clamping motor 21 in a state where the actual speed value of the crosshead 20a is substantially zero.

The ejector device ejects the molded article from the mold. The ejector has an ejector rod as a movable portion and an ejector motor as an AC motor. The ejector rod moves forward and backward relative to the mold (for example, the movable mold). The ejector rod is advanced and retracted by the ejector motor, and the molded article is ejected from the mold. A motion conversion mechanism that converts the rotational motion of the ejector motor into a linear motion of the ejector rod is provided between the ejector motor and the ejector rod. In the ejector process of the molded article, the ejector motor may be driven in a state where the actual speed value of the ejector rod is substantially zero. For example, there is a case where the adhesion between the mold and the molded article is strong, and the mold and the molded article cannot be separated immediately.

The mold compression device compresses the forming material in the cavity space. The mold compression device has a compression mold as a movable portion and a compression motor as an AC motor. The compression mold is movably disposed in the mold unit. The compression motor compresses the molding material in the cavity space by moving the compression mold. A motion conversion mechanism that converts the rotational motion of the compression motor into a linear motion of the compression mold is provided between the compression motor and the compression mold. In the compression process of the molding material, the compression motor may be driven in a state where the actual speed value of the compression mold is substantially zero.

The injection device moving device moves the injection device 40 relative to the frame Fr move. The injection device moving device has a slide base Sb as a movable portion and a movement motor as an AC motor. The moving motor presses the nozzle 42 against the mold (for example, a fixed mold) by moving the slide base Sb. Between the moving motor and the slide base Sb, a motion converting mechanism that converts the rotational motion of the moving motor into a linear motion of the sliding base Sb is provided. In the nozzle contact process in which the nozzle 42 is pressed against the mold, the movement motor may be driven in a state where the actual speed value of the slide base Sb is substantially zero. For example, the moving motor is driven in a state where the nozzle 42 is pressed against the mold, and the nozzle contact pressure is generated.

Further, in the above embodiment, a rotary motor is used as the AC motor, but a linear motor may be used.

Claims (4)

An injection molding machine comprising: an AC motor that drives a movable portion; and a controller that controls a speed command value associated with the movable portion, an actual speed value associated with the movable portion, and a protection command for changing a current phase of the AC motor And controlling the AC motor, wherein the controller controls the AC motor according to the protection command value so that the rotation of the AC motor does not stop during the control of the AC motor, and the controller is based on Calculating the speed command value based on a pressure command value associated with the movable portion and an actual pressure value associated with the movable portion, wherein the controller is configured to attenuate a component of at least a predetermined frequency of the actual pressure value And the pressure command value to calculate the speed command value, wherein the predetermined frequency is a frequency of the protection command value. The injection molding machine according to claim 1, wherein the protection command value periodically changes a current phase of the AC motor. The injection molding machine according to claim 1 or 2, wherein the AC motor is a rotary motor, and the protection command value changes a rotation angle of the AC motor. The injection molding machine according to claim 1 or 2, wherein the controller is controlled by the movable portion, wherein the speed command value and/or the actual speed value is within a predetermined range including zero In the case, the AC motor is controlled based on the speed command value, the actual speed value, and the protection command value.