JP2021167095A - Electric circuit of injection molding machine - Google Patents

Abstract

To provide an electric circuit of an injection molding machine having a simple circuit configuration and capable of increasing a frequency at which the injection molding machine can be continuously operated in an event of a momentary power failure without performing special control.SOLUTION: An injection molding machine comprises an electric circuit 40 having a servo driver 50 that drives and controls a servo motor 36. The electric circuit 40 comprises: a servo driver 50 having a conversion circuit 52 that converts alternating current that has a predetermined voltage and that is input from a commercial alternating current power supply 17 into a voltage and frequency used for controlling the servo motor 36; and a direct current power supply circuit 60 that converts alternating current that has the predetermined voltage and that is input from the commercial alternating current power supply 17 into direct current that has a supply voltage lower than the predetermined voltage to output the current. The conversion circuit 52 comprises: a converter unit 53; a smoothing capacitor 55; and an inverter unit 56. The servo driver 50 and the direct current power supply circuit 60 are connected through a bypass circuit 80 including a backflow prevention circuit 81 that allows a current from the smoothing capacitor 55 to the direct current power supply circuit 60.SELECTED DRAWING: Figure 3

Description

The present invention relates to an electric circuit of an injection molding machine including a motor.

For example, Patent Documents 1 to 4 disclose an electric circuit of an injection molding machine including a servomotor. The injection molding machine includes an electric circuit that drives and controls a servomotor.
In Patent Document 1, an energy holding circuit composed of a capacitor and a power failure detection circuit are provided, a power failure processing operation that protects the molding machine in the event of a power failure is performed, and an electric circuit of the injection molding machine that safely and normally terminates the operation of the molding machine. Is disclosed.

Further, Patent Document 2 discloses an electric circuit of an injection molding machine that saves energy and takes measures against a power failure by charging and discharging a smoothing capacitor of an inverter and a charger in combination.
Further, Patent Document 3 discloses an electric circuit of an injection molding machine that uses a capacitor as a power storage unit and uses a regenerative current accompanying deceleration of the motor to level the electric power required for acceleration control of the motor.

Further, in Patent Document 4, the rectifier and the drive device are provided with a smoothing capacitor, and the control command value is lowered at the time of power failure detection to reduce the pressure and speed to secure the operation continuation function at the time of power failure. The circuit is disclosed.

Japanese Unexamined Patent Publication No. 2004-216829 Japanese Unexamined Patent Publication No. 2001-232672 Japanese Unexamined Patent Publication No. 2000-141440 Japanese Unexamined Patent Publication No. 2015-100996

However, in countries and regions where the power supply situation of the commercial AC power supply is poor, a momentary power outage occurs in which the commercial AC power supply is momentarily stopped due to reasons such as unstable power supply. If a momentary power failure occurs, the operation of the injection molding machine will stop. In the electric circuit of a conventional injection molding machine, it is possible to suppress the stoppage of the operation of the injection molding machine in the event of a momentary power failure, but the structure is complicated and expensive, and special detection and control such as power failure detection and reduction of control command are performed. There is a problem that it is necessary. Therefore, there is a demand for an electric circuit having a simple configuration and capable of continuing the operation of the injection molding machine even in the event of a momentary power failure without performing special control.

An object of the present invention is to provide an electric circuit of an injection molding machine capable of increasing the frequency with which the operation of the injection molding machine can be continued in the event of a momentary power failure.

Hereinafter, means for solving the above problems and their actions and effects will be described.
The electric circuit of the injection molding machine that solves the above problems is an electric circuit of the injection molding machine having a motor driver that drives and controls the motor, and an AC of a predetermined voltage input from a commercial AC power supply is used to control the motor. A motor driver having a conversion circuit for converting voltage and frequency, and a DC power supply circuit for converting AC of a predetermined voltage input from a commercial AC power supply into DC having a control supply voltage lower than the predetermined voltage and outputting the DC power supply circuit. The conversion circuit includes a rectifier, a smoothing capacitor, and a switching circuit, and the motor driver and the DC power supply circuit are connected via a bypass circuit including a backflow prevention circuit that allows a current from the smoothing capacitor to the DC power supply circuit. Has been done.

According to this configuration, in the event of a momentary power failure in which the commercial AC power supply is momentarily stopped, the current due to the electric charge stored in the smoothing capacitor is supplied from the motor driver to the DC power supply circuit via a bypass circuit including a backflow prevention circuit. As a result, the DC power supply circuit can supply a predetermined voltage of DC even during a momentary power failure. As a result, the motor continues to be driven even after the power is restored from the momentary power failure of the commercial AC power supply. Therefore, it is possible to increase the frequency with which the operation of the injection molding machine can be continued by continuing the driving of the motor after the power is restored in the event of a momentary power failure with a simple circuit configuration and without performing special control.

The electric circuit of the injection molding machine further includes a heater circuit that heats a heater by alternating current supplied from the commercial alternating current power supply common to the DC power supply circuit, and the DC power supply circuit receives alternating current from the commercial alternating current power supply. A first rectifying circuit that converts rectification, a switching circuit that converts rectification to alternating current by PWM control, an isolated transformer that converts alternating current frequency, and a second rectifying circuit that converts alternating current at the converted frequency into rectifying current. A smoothing circuit that smoothes the rectification to the direct current of the supply voltage may be provided.

According to this configuration, the rectifier circuit of the DC power supply circuit prevents a part of the current supplied from the smoothing capacitor to the DC power supply circuit from flowing to the heater circuit via the DC power supply circuit at the time of a momentary power failure. Therefore, even if a momentary power failure occurs, the motor can be continuously driven, and the frequency of continuing the operation of the injection molding machine can be further increased.

In the electric circuit of the injection molding machine, a second smoothing capacitor may be externally attached to the motor driver in parallel with the smoothing capacitor.
According to this configuration, the electric charges for a plurality of smoothing capacitors are stored in the event of a momentary power failure of the commercial AC power supply, so that the frequency with which the injection molding machine can be continued can be further increased.

In the electric circuit of the injection molding machine, the motor driver controls a plurality of motors, the conversion circuit includes at least the smoothing capacitor and the switching circuit for each of the plurality of the motors, and the plurality of the smoothing capacitors are provided. It is connected to the DC power supply circuit via the bypass circuit.

According to this configuration, in the event of a momentary power failure of the commercial AC power supply, the current due to the electric charges stored in the plurality of smoothing capacitors is supplied to the DC power supply circuit, so that the operation of the injection molding machine can be continued more frequently.

In the electric circuit of the injection molding machine, the DC power supply circuit is provided with M (where M is a natural number of 2 or more), and the conversion circuit is provided with N (where N is a natural number of 2 or more). The smoothing capacitors are connected to the M DC power supply circuits via the bypass circuit, and the N may be more than the M.

According to this configuration, in the event of a momentary power failure of a commercial AC power supply, the current due to the electric charge stored in the N smoothing capacitors is supplied to the M DC power supply circuits, which are less than N, so that the injection molding machine can be operated. The frequency with which you can continue is even higher.

According to the present invention, it is possible to provide an electric circuit of an injection molding machine capable of increasing the frequency with which the operation of the injection molding machine can be continued in the event of a momentary power failure with a simple circuit configuration.

The schematic diagram which shows the injection molding machine in 1st Embodiment. The block diagram which shows the electric circuit of an injection molding machine. A circuit diagram showing an electric circuit of an injection molding machine. The graph which shows the voltage change at the time of the instantaneous power failure in the comparative example. The graph which shows the voltage change at the time of a momentary power failure in an Example. The circuit diagram which shows the electric circuit of the injection molding machine in 2nd Embodiment. The circuit diagram which shows the electric circuit of the injection molding machine in 3rd Embodiment.

(First Embodiment)
Hereinafter, the injection molding machine and its electric circuit according to the first embodiment will be described with reference to the drawings.

First, a schematic configuration of an electro-hydraulic injection molding machine according to the present embodiment will be described with reference to FIG. The electro-hydraulic injection molding machine 10 is driven by hydraulic oil supplied by driving a hydraulic pump 34 by a servomotor 36.

As shown in FIG. 1, the injection molding machine 10 includes an injection device 11 and a mold clamping device 12. The injection device 11 is arranged at a heating cylinder 21 having an injection nozzle 21n at the front end and a hopper 21h at the rear, a screw 22 inserted inside the heating cylinder 21, and a screw 22 at the rear end of the heating cylinder 21. A screw drive unit 23 for driving the above is provided. The screw drive unit 23 includes an injection cylinder (hydraulic cylinder) 24 containing a single rod type injection ram 24a. The ram rod 24b projecting forward of the injection cylinder 24 is coupled to the rear end of the screw 22. Further, a shaft of a metering motor (oil motor) 25 attached to the injection cylinder 24 is spline-coupled to the rear end of the injection ram 24a. The injection device 11 includes a moving cylinder 26 below the injection device 11 that moves the injection device 11 forward and backward to touch or release the nozzle on the mold 15. Further, a plurality of heaters 27 are attached to the outer peripheral surface of the heating cylinder 21 in a wound state. The injection device 11 touches the mold 15 with the injection nozzle 21n, and injects and fills the molten (plasticized) resin (not shown) in the cavity of the mold 15.

On the other hand, as the mold clamping device 12, a direct pressure type hydraulic mold clamping device that displaces the movable mold 15 m by the drive ram 28a of the mold clamping cylinder (hydraulic cylinder) 28 is used. The mold clamping device 12 has a fixed platen 29 whose position is fixed, and a movable platen 31 which is slidably loaded into a plurality of tie bars 30 erected between the fixed platen 29 and the mold clamping cylinder 28. The tip of the ram rod 28b protruding forward from the mold clamping cylinder 28 is fixed to the movable platen 31. Further, a fixed mold 15c is attached to the fixed plate 29, and a movable mold 15 m is attached to the movable plate 31. The fixed mold 15c and the movable mold 15m form a mold 15. As a result, the mold clamping cylinder 28 opens and closes the mold 15 and clamps the mold. The mold clamping device 12 includes an ejector cylinder 32 that projects a molded product (not shown) adhering to the movable mold 15 m when the mold 15 is opened.

On the other hand, the injection molding machine 10 includes a hydraulic circuit 33. The hydraulic circuit 33 includes a hydraulic pump 34 as a hydraulic drive source and a switching valve circuit 35. The injection molding machine 10 includes a servomotor 36 as an example of a motor that rotationally drives the hydraulic pump 34, and a rotary encoder 37 that detects the rotation speed of the servomotor 36. The hydraulic pump 34 is, for example, a swash plate type piston pump having a variable discharge capacity. The hydraulic pump 34 may be another type of hydraulic pump having a variable discharge capacity, or a hydraulic pump having a constant discharge capacity.

The suction port of the hydraulic pump 34 is connected to the oil tank 38, and the discharge port of the hydraulic pump 34 is connected to the primary side of the switching valve circuit 35. Further, the secondary side of the switching valve circuit 35 is connected to the injection cylinder 24, the measuring motor 25, the mold clamping cylinder 28, the ejector cylinder 32, the moving cylinder 26 and other hydraulic actuators in the injection molding machine 10. The switching valve circuit 35 is an electromagnetic switching having a switching function related to supply, stop, and discharge of hydraulic oil to the injection cylinder 24, the measuring motor 25, the mold clamping cylinder 28, the ejector cylinder 32, the moving cylinder 26, and other hydraulic actuators. It is equipped with a valve (not shown).

By variably controlling the rotation speed of the servomotor 36 and controlling the discharge flow rate and discharge pressure of the hydraulic pump 34, the above-mentioned injection cylinder 24, measuring motor 25, mold clamping cylinder 28, ejector cylinder 32, moving cylinder 26, etc. Is driven and controlled. As a result, each step in the molding cycle of the injection molding machine 10 is controlled. The injection molding machine 10 includes an electric circuit 40 shown in FIG. 2, which includes a control system circuit for controlling a servomotor 36, a heater 27, and the like.

As shown in FIG. 2, the electric circuit 40 includes a servo driver 50 as an example of a motor driver that inputs an AC of a predetermined voltage supplied from a commercial AC power supply 17 to drive and control the servo motor 36, and a commercial AC power supply 17. It is provided with a DC power supply circuit 60 that converts an alternating current of a predetermined voltage supplied from the above into a direct current having a control power supply voltage V0, which is an example of the supply voltage. Further, the electric circuit 40 includes a heater circuit 70 that heats and controls the heater 27 with electric power from the commercial AC power supply 17. Further, the electric circuit 40 includes a plurality of power supply circuits 44, 45, 46, 47 electrically connected to the DC power supply circuit 60, and a main controller 41. Further, the servo driver 50 includes a servo controller 51. The DC of the control power supply voltage V0 output by the DC power supply circuit 60 is transmitted through the power supply circuits 44, 45, 46, 47 to the main controller 41, the sensor 42, the electric actuator 43, the switching valve circuit 35, and the servo controller 51. The voltage is stepped down to a predetermined voltage required at the supply destination and output.

The main controller 41 is electrically connected to the sensor 42, and individually outputs control signals to the drive circuits of the servo controller 51, the electric actuator 43, and the switching valve circuit 35 based on the detection result input from the sensor 42. The servo controller 51 controls the three-phase voltage and frequency supplied to the servomotor 36 via the conversion circuit 52 shown in FIG. 3 that constitutes the servo driver 50 based on the control signal input from the main controller 41. As a result, the servo driver 50 controls the drive / stop of the servomotor 36 and the rotation speed during the drive. Further, the heater circuit 70 is composed of a temperature control circuit that individually turns on / off the currents supplied to the plurality of heaters 27 based on the temperature control signals input from the main controller 41.

Next, with reference to FIG. 3, the main configuration of the electric circuit 40 will be described in detail. In FIG. 3, the main controller 41, a part of the servo controller 51, the sensor 42, the electric actuator 43, the switching valve circuit 35, and the plurality of power supply circuits 44 to 47 are not shown. In FIG. 3, the servo controller 51 shows only the regenerative control circuit 57, which is a part thereof.

As described above, the electric circuit 40 includes a servo driver 50, a DC power supply circuit 60, and a heater circuit 70. The predetermined voltage of the commercial AC power supply 17 is, for example, a predetermined value in the range of 300 to 500 V. In this example, the predetermined voltage is 440V as an example.

The servo driver 50 includes a conversion circuit 52 controlled by the servo controller 51. The conversion circuit 52 converts the AC of a predetermined voltage input from the commercial AC power supply 17 into the voltage and frequency used for controlling the servomotor 36. The conversion circuit 52 includes a converter unit 53 as an example of a rectifier connected to a commercial AC power supply 17 that supplies a three-phase AC, a regenerative circuit 54, a smoothing capacitor 55, and an inverter unit 56 as an example of a switching circuit, in this order. It is connected with. The conversion circuit 52 has a high potential side power supply line (hereinafter referred to as “P line”) Lp and a low potential side power supply line (hereinafter referred to as “N line”) Ln.

The converter unit 53 has six diodes D1 connected in a bridge, and rectifies an alternating current of a predetermined voltage input from the commercial AC power supply 17 to a direct current of a predetermined voltage. In the six diodes D1, three sets of two sets connected in series in the same direction are connected in parallel between the P line Lp and the N line Ln, and two sets are connected in series. Three wires of each phase R, T, and S of three-phase AC from the commercial AC power supply 17 are connected between the diodes D1. Therefore, the P line Lp is applied to a predetermined high potential, and the N line Ln is applied to a predetermined low potential.

The smoothing capacitor 55 smoothes the pulsating current whose alternating current is rectified by the converter unit 53.
The inverter unit 56 includes six arms in which the transistor Q1 and the diode D2 are connected in antiparallel, and there are three sets in which two of the six arms are connected in series between the P line Lp and the N line Ln. The pairs are connected in parallel. In the servomotor 36, the terminals of the three phases U, V, and W of the servomotor 36 are connected between three sets of transistors Q1 connected in series by two in the inverter unit 56, respectively. The inverter unit 56 is controlled by the servo controller 51. That is, the servo controller 51 controls the voltage and frequency supplied to the servomotor 36 by switching the on / off of the six transistors Q1 by, for example, PWM (Pulse Width Modulation) control. As a result, the drive / stop and rotation speed of the servomotor 36 are controlled.

The main controller 41 (see FIG. 2) drives the servomotor 36 when hydraulic oil is required in the hydraulic circuit 33 (see FIG. 1) based on the detection results of the various sensors 42, and the detection results of the various sensors 42 are obtained. Based on this, the drive of the servomotor 36 is stopped when the hydraulic oil in the hydraulic circuit 33 is not required. The servomotor 36 generates electricity in the deceleration process to generate a regenerative current. The electric power generated by the servomotor 36 is stored in the smoothing capacitor 55.

The regenerative circuit 54 includes a resistor R1, a diode D3, and a transistor Q2 connected between the P line Lp and the N line Ln. The resistor R1 and the diode D3 are connected in parallel, the terminal on the low voltage side of the resistor R1 is connected to the collector terminal of the transistor Q2, and the emitter terminal thereof is connected to the N line Ln. The regeneration control circuit 57 inputs a voltage between the P terminal on the P line Lp and the N terminal on the N line Ln. The regeneration control circuit 57 turns off the transistor Q2 when the voltage value between the input PNs is equal to or less than the threshold value, and turns on the transistor Q2 when the voltage value exceeds the threshold value. When the transistor Q2 is off, the regenerative current of the servomotor 36 is stored in the smoothing capacitor 55. When the transistor Q2 is on, the regenerative current of the servomotor 36 is consumed as heat by the resistor R1.

On the other hand, the DC power supply circuit 60 includes a rectifier circuit 61 which is an example of the first rectifier circuit, a capacitor 62 for smoothing, a switching circuit 63, an isolation transformer 64, and a rectifier circuit 65 and a smoothing circuit 66 which are examples of the second rectifier circuit. Be prepared. The isolation transformer 64 is, for example, a high frequency isolation transformer.

The rectifier circuit 61 has four diodes D4 connected by a bridge, and rectifies an alternating current of a predetermined voltage between two phases input from a commercial AC power supply 17 to a direct current of a predetermined voltage. The four diodes D4 are connected in series between two sets of two sets connected in series in the same direction between the high potential side power supply line La and the low potential side power supply line Lb. Two of the two phases of the three-phase AC from the commercial AC power supply 17 are connected between the two diodes D4. Therefore, the high potential side power supply line La is applied to a predetermined high potential, and the low potential side power supply line Lb is applied to a predetermined low potential.

The smoothing capacitor 62 smoothes the pulsating current whose alternating current is rectified by the rectifier circuit 61.
The switching circuit 63 includes four arms in which the transistor Q3 and the diode D5 are connected in antiparallel, and two of the four arms are connected in series between the high potential side power supply line La and the low potential side power supply line Lb. Two sets connected to are connected in parallel. Two terminals of the primary coil of the isolation transformer 64 are connected to each of the two transistors Q3 in each set in which two are connected in series. The base terminals of the four transistors Q3 are connected to the voltage control circuit 69, respectively. The voltage control circuit 69 controls the voltage and frequency output to the primary coil of the isolation transformer 64 by controlling the four transistors Q3 to be turned on and off by PWM control.

The rectifier circuit 65 has four diodes D6 bridge-connected, and rectifies a predetermined voltage and a current of a predetermined frequency input from the secondary coil of the isolation transformer 64 to direct current. The four diodes D6 are connected in series between two sets of two sets connected in series in the same direction between the high potential side power supply line Lc and the low potential side power supply line Ld. The two terminals of the secondary coil of the isolation transformer 64 are connected between the two diodes D6. Therefore, the high potential side power supply line Lc is applied to a predetermined high potential, and the low potential side power supply line Ld is applied to a predetermined low potential.

The smoothing circuit 66 includes a coil 67 connected in series with the high potential side power supply line Lc, and a smoothing capacitor 68 connected between the high potential side power supply line Lc and the low potential side power supply line Ld. Therefore, the high potential side power supply line Lc is applied to the high potential + V volt, and the low potential side power supply line Ld is applied to the low potential −V volt (for example, 0V). Therefore, the DC power supply circuit 60 outputs the voltage between the terminal T1 on the high potential side power supply line Lc and the terminal T2 on the low potential side power supply line Ld as the control power supply voltage V0.

The voltage control circuit 69 inputs the voltage between the two terminals T1 and T2, and when the input voltage is a value exceeding the permissible range with respect to the control power supply voltage V0, PWMs the on / off of the four transistors Q3. Switch by control. As a result, the voltage control circuit 69 controls the voltage and frequency output to the primary coil of the isolation transformer 64, and adjusts the voltage between the terminals T1 and T2 to be the target control power supply voltage V0.

Here, the capacity of the smoothing capacitor 55 is C1, the capacity of the smoothing capacitor 62 is C2, and the capacity of the smoothing capacitor 68 is C3. The magnitude relationship between the capacities C1, C2, and C3 is C1> C2> C3. Since the smoothing capacitor 55 in the servo driver 50 is used for motor control, a large capacity is required. On the other hand, the smoothing capacitors 62 and 68 in the DC power supply circuit 60 need to have a smaller capacity than the smoothing capacitor 55.

In the present embodiment, the servo driver 50 and the DC power supply circuit 60 are electrically connected via a bypass circuit 80 including a backflow prevention circuit 81. The backflow prevention circuit 81 allows the current based on the voltage stored in the smoothing capacitor 55 constituting the servo driver 50 to flow in the direction of being supplied to the DC power supply circuit 60, and blocks the current flowing in the opposite direction. do. Specifically, the bypass circuit 80 includes a first bypass line L1 that connects the P line Lp on the servo driver 50 side and the high potential side power supply line La on the DC power supply circuit 60 side, and an N line Ln on the servo driver 50 side and DC. A second bypass line L2 for connecting to the low potential side power supply line Lb on the power supply circuit 60 side is provided. The backflow prevention circuit 81 is provided on the first bypass line L1 and includes a first diode 82 that allows a current in the direction from the servo driver 50 toward the DC power supply circuit 60 and blocks the current in the reverse direction. ..

Next, the operation of the electric circuit 40 of the injection molding machine 10 in the present embodiment will be described.
When a momentary power failure occurs in the commercial AC power supply 17, the supply of alternating current of a predetermined voltage to the servo driver 50, the DC power supply circuit 60, and the heater circuit 70 is momentarily stopped during the power failure time Tpc. After the start of the instantaneous power failure, the potential of the P line Lp is maintained at a high potential by the electric charge stored in the smoothing capacitor 55 for a predetermined time. On the other hand, in the event of an instantaneous power failure, the high potential of the high potential side power supply line La of the DC power supply circuit 60 precedes the high potential of the P line Lp due to the difference in capacitance between the smoothing capacitor 55 and the smoothing capacitor 62. Descent. As a result, the electric charge stored in the smoothing capacitor 55 causes a current to flow from the P line Lp to the high potential side power supply line Lc of the DC power supply circuit 60 via the bypass circuit 80, and the smoothing capacitor 62 is stored. As a result, in the DC power supply circuit 60, the time for which the potential of the high potential side power supply line La is maintained at a high potential is extended. As a result, the time during which the DC power supply circuit 60 can continue to output the control power supply voltage V0 after the start of the instantaneous power failure is extended.

Further, the current flowing to the high potential side power supply line La of the DC power supply circuit 60 via the bypass circuit 80 is prevented from flowing to the commercial AC power supply 17 side by the diode D4 of the rectifying circuit 61, so that the current flows to the heater circuit. It is avoided that it flows to 70 and is consumed. Therefore, the current from the bypass circuit 80 is efficiently used to keep the high potential side power supply line La of the DC power supply circuit 60 at a high potential. From this point as well, the time during which the DC power supply circuit 60 can continue to output the control power supply voltage V0 from the start of the instantaneous power failure can be extended.

When the injection molding machine 10 is operating normally without a momentary power failure of the commercial AC power supply 17, a current may flow from the DC power supply circuit 60 to the servo driver 50 via the bypass circuit 80 by the backflow prevention circuit 81. No. Therefore, the DC power supply circuit 60 can output a DC with a stable control power supply voltage V0.

By the way, in most cases, the power failure time Tpc of the instantaneous power failure that occurs in a country or region where the power supply condition of the commercial AC power source 17 is poor is in the range of several tens of milliseconds to less than 100 milliseconds. The capacity of the smoothing capacitor 62 in the DC power supply circuit 60 is not sufficient for the power failure time Tpc at the time of a momentary power failure. However, since the current due to the electric charge stored in the large-capacity smoothing capacitor 55 included in the conversion circuit 52 of the servo driver 50 flows to the DC power supply circuit 60 via the bypass circuit 80, the high potential side power supply line of the DC power supply circuit 60 The potential of La is maintained at a high potential. Therefore, the high potential side power supply line La is maintained at the required high potential during the instantaneous power failure.

As a result, the DC power supply circuit 60 can output the required control power supply voltage V0 during the period until the power is restored in the event of a momentary power failure. Therefore, the control during execution by the main controller 41 is not forcibly stopped, and the forcible stop of the injection molding machine 10 is avoided. As a result, the frequency with which the injection molding machine 10 can be continued in the event of a momentary power failure increases. For example, when the injection molding machine 10 is forcibly stopped at the time of a momentary power failure, it takes time for restoration work such as turning the power off and then on again in order to restart the operation of the injection molding machine 10, and the productivity of the injection molding machine 10 is reduced. In particular, if the operator does not notice the forced stop of the injection molding machine 10, the injection molding machine 10 is left stopped, so that the productivity is significantly reduced. Since the injection molding machine 10 of the present embodiment can continue the operation of the injection molding machine 10 at the time of a momentary power failure, the decrease in productivity due to the momentary power failure can be suppressed as much as possible.

An evaluation test of the electric circuit 40 of the present embodiment was performed. In the mold opening process, which is one of the processes with a large load in the molding cycle of the injection molding machine 10, a momentary power failure of about 100 milliseconds is forcibly generated, so that the effect of the injection molding machine 10 at the time of a momentary power failure can be obtained. evaluated. An instantaneous power failure was simulated by performing an operation of momentarily turning off the original power switch and immediately returning it to ON during the mold opening process during the automatic operation of the injection molding machine 10. In most cases, the power failure time Tpc at the time of an actual instantaneous power failure is less than 100 milliseconds.

FIG. 4 is a graph showing the evaluation results of the electric circuit of the comparative example not provided with the bypass circuit 80. Further, FIG. 5 is a graph showing the evaluation results of the electric circuit 40 of the embodiment including the bypass circuit 80. 4 and 5 show the voltages measured at the four measurement points in the electric circuit 40. That is, the measured voltages are the AC input voltage Vac, the servo power supply voltage Vpn, the motor voltage Vm, and the control power supply voltage Vdc. The AC input voltage Vac is a voltage input from the commercial AC power supply 17. The servo power supply voltage Vpn is a voltage between the P line Lp and the N line Ln. The motor voltage Vm is a voltage supplied to the servomotor 36. The control power supply voltage Vdc is the output voltage of the DC power supply circuit 60.

FIG. 4 shows the measurement results of the respective voltages Vac, Vpn, Vm, and Vdc when the power failure time Tpc at the time of a momentary power failure is 114 milliseconds in the comparative example. During a momentary power failure, the power supply from the commercial AC power supply 17 is stopped, so the AC input voltage Vac becomes 0 volt.

The servo power supply voltage VPN gradually decreases from the start of the instantaneous power failure. This is because the electric charge stored in the smoothing capacitor 55 is gradually reduced. The servo power supply voltage Vpn returned to the required high potential after recovering from the instantaneous power failure. However, the motor voltage Vm decreased and became unstable from the start of the instantaneous power failure, and the required motor voltage could not be supplied even after the power was restored from the instantaneous power failure.

The control power supply voltage Vdc is maintained at the required control power supply voltage V0 by the electric charge stored in the smoothing capacitor 62 for a predetermined time from the start of the instantaneous power failure, but then drops to 0 volt. This drop in the control power supply voltage Vdc leads to a drop in the drive voltage of the main controller 41. Therefore, when the main controller 41 detects a drop in the supplied drive voltage, the main controller 41 forcibly stops the control during execution. As a result, the servomotor 36 and the electric actuator 43 are forcibly stopped. That is, the injection molding machine 10 is in an emergency stop.

On the other hand, FIG. 5 shows the measurement results of the respective voltages Vac, Vpn, Vm, and Vdc when the power failure time Tpc at the time of a momentary power failure is 160 milliseconds in the embodiment. During a momentary power failure, the power supply from the commercial AC power supply 17 is stopped, so the AC input voltage Vac becomes 0 volt. When the power is restored from the momentary power failure, the AC input voltage Vac returns to a predetermined voltage (for example, 440V).

The servo power supply voltage VPN gradually decreases from the start of the instantaneous power failure. This is because the electric charge stored in the smoothing capacitor 55 is used to maintain the high potential, but the stored electric charge gradually decreases. The servo power supply voltage Vpn returned to the required high potential after recovering from the instantaneous power failure.

Although the motor voltage Vm decreases and becomes unstable from the start of the instantaneous power failure, the required motor voltage can be supplied after the power is restored from the instantaneous power failure.
The control power supply voltage Vdc flows to the DC power supply circuit 60 via the bypass circuit 80 by the electric charge stored in the smoothing capacitor 62 and the electric charge stored in the smoothing capacitor 55 for a predetermined time from the start of the instantaneous power failure. The current keeps it at the required high potential. As a result, the time for which the control power supply voltage Vdc is maintained at the target control power supply voltage V0 is extended by the amount of the current flowing through the bypass circuit 80 to the DC power supply circuit 60. After that, the control power supply voltage Vdc is maintained at the required control power supply voltage V0 even after the power is restored from the instantaneous power failure. Therefore, the main controller 41 can continue the control during execution, and the servomotor 36 and the electric actuator 43 are continuously driven. That is, the injection molding machine 10 continues to operate without stopping.

As a result of the evaluation test, the injection molding machine 10 cannot continue the operation unless one of the motor voltage Vm and the control power supply voltage Vdc can be restored when the power is restored from the instantaneous power failure. In the embodiment shown in FIG. 5, when the power is restored from the instantaneous power failure, both the motor voltage Vm and the control power supply voltage Vdc can be restored, so that the injection molding machine 10 can continue the operation.

In the evaluation test of the comparative example, the injection molding machine 10 was stopped when the power failure time Tpc was 114 ms, 124 ms, and 148 ms. On the other hand, in the evaluation test of the example, when the power failure time Tpc was 128 ms, 132 ms, 136 ms, 146 ms, or 160 ms, the injection molding machine 10 was used even after a momentary power failure. Continued operation. In the evaluation test of the example, it was confirmed that the operation of the injection molding machine 10 was continued until the power failure time Tpc was 175 milliseconds at the longest. Therefore, according to the injection molding machine 10 of the embodiment, it is effective for an instantaneous power failure of up to about 150 milliseconds. This means that it is effective in preventing the forced stop of the injection molding machine 10 at the time of a momentary power failure in a country or region where the power failure time Tpc at the time of a momentary power failure is less than 100 milliseconds.

As described in detail above, according to this embodiment, the following effects can be obtained.
(1) The electric circuit 40 of the injection molding machine 10 includes a servo driver 50 having a conversion circuit 52 that converts an AC of a predetermined voltage input from a commercial AC power supply 17 into a voltage and a frequency used for controlling the servo motor 36, and a commercial AC. It is provided with a DC power supply circuit 60 that converts an AC of a predetermined voltage input from the AC power supply 17 into a DC having a supply voltage lower than the predetermined voltage and outputs the AC. The conversion circuit 52 includes a converter unit 53, a smoothing capacitor 55, and an inverter unit 56 as an example of a switching circuit. The servo driver 50 and the DC power supply circuit 60 are connected via a bypass circuit 80 including a backflow prevention circuit 81 that allows a current from the smoothing capacitor 55 to the DC power supply circuit 60. Therefore, at the time of a momentary power failure of the commercial AC power supply 17, the current due to the electric charge stored in the smoothing capacitor 55 is supplied from the servo driver 50 to the DC power supply circuit 60 via the backflow prevention circuit 81. Therefore, the DC power supply circuit 60 can supply a predetermined voltage of DC during a momentary power failure. As a result, the servomotor 36 continues to be driven even after the power is restored from the momentary power failure of the commercial AC power supply 17. Therefore, the servomotor 36 is continuously driven after the power is restored in the event of a momentary power failure without providing a complicated and expensive device such as an uninterruptible power supply, with a simple circuit configuration, and without performing special control, and injection molding is performed. The frequency with which the operation of the machine 10 can be continued can be increased.

(2) The electric circuit 40 further includes a heater circuit 70 that heats the heater 27 by alternating current supplied from a commercial alternating current power source 17 common to the direct current power supply circuit 60. The DC power supply circuit 60 includes a first rectifier circuit 61 that converts AC from a commercial AC power supply 17 into rectifier, a switching circuit 63 that converts rectifier into AC by PWM control, and an isolated transformer 64 that converts AC frequency. It includes a second rectifying circuit 65 that converts alternating current of the converted frequency into rectification, and a smoothing circuit 66 that smoothes rectifying to direct current of the supply voltage. Therefore, the current supplied from the smoothing capacitor 55 to the DC power supply circuit 60 at the time of a momentary power failure can be prevented from flowing to the heater circuit 70 via the DC power supply circuit 60 by the backflow prevention function of the diode D4 constituting the rectifier circuit 61. .. Therefore, the current supplied from the smoothing capacitor 55 to the DC power supply circuit 60 at the time of a momentary power failure can be effectively used to extend the time during which the high potential side power supply line La can be held at the required high potential. Therefore, since the servomotor 36 can be continuously driven even after the power is restored from the instantaneous power failure, the frequency with which the injection molding machine 10 can be continuously operated can be further increased.

(Second Embodiment)
Next, the second embodiment will be described with reference to FIG. The second embodiment is different from the first embodiment in that a second smoothing capacitor externally attached in parallel with the smoothing capacitor 55 is provided. The description of the same configuration as that of the first embodiment will be omitted, and only the different configurations will be described. In FIG. 6, the same reference numerals are given to the circuit portions common to those in FIG. 3, and the circuits are shown by one block.

As shown in FIG. 6, the servo driver 50 includes an external unit 58 having terminals that can be connected in parallel with the smoothing capacitor 55. An external second smoothing capacitor 59 is connected to the external unit 58 in parallel with the smoothing capacitor 55 in the servo driver 50. That is, two smoothing capacitors 55 and 59 are connected in parallel between the P line Lp and the N line Ln. As a result, in the event of a momentary power failure, the current due to the two charges stored in the two smoothing capacitors 55 and 59 is supplied to the DC power supply circuit 60 via the bypass circuit 80. Therefore, at the time of a momentary power failure, the time during which the potential of the P line Lp in the servo driver 50 can be held at a higher potential than that of the electric circuit 40 of the first embodiment and the potential of the high potential side power supply line La in the DC power supply circuit 60 are set. The time that can be held at a high potential can be further extended. Therefore, the motor voltage Vm and the control power supply voltage Vdc can be returned to the target voltage after the power is restored from the instantaneous power failure. As a result, the operation of the injection molding machine 10 can be continued even in the event of a momentary power failure.

According to the second embodiment, the following effects can be obtained in addition to the same effects as those of the first embodiment.
(3) A second smoothing capacitor 59 is externally attached to the servo driver 50 in parallel with the smoothing capacitor 55. Therefore, it is possible to further increase the frequency with which the injection molding machine 10 can be continued to operate in the event of a momentary power failure of the commercial AC power supply 17.

(Third Embodiment)
Next, the third embodiment will be described with reference to FIG. 7. The injection molding machine 10 of the first embodiment and the second embodiment is an electro-hydraulic type in which a servomotor 36 drives a hydraulic pump 34, but the injection molding machine 10 of the present embodiment is an electric type. The electric injection molding machine 10 replaces the injection cylinder 24, the weighing motor 25, the mold clamping cylinder 28, the ejector cylinder 32, and the moving cylinder 26 in the first embodiment, and replaces the injection motor, the weighing motor, and the mold clamping motor, respectively. It is equipped with an ejector motor and a moving motor for touching the nozzle. Of these five motors, at least N (N is a natural number of 2 or more) comprises the servomotor 36. In this embodiment, for example, four servomotors 36 are provided. The four servo motors 36 are an injection motor, a weighing motor, a mold clamping motor, and an ejector motor.

As shown in FIG. 7, the electric circuit 40 of the injection molding machine 10 includes a servo driver 50 that controls a plurality of servo motors 36. The conversion circuit 52 included in the servo driver 50 includes a first conversion circuit 521, a second conversion circuit 522, ..., And an Nth conversion circuit 52N that individually controls N servomotors 36. N conversion circuits 521 to 52N are connected in parallel between the common P line Lp and the N line Ln in the conversion circuit 52. The N conversion circuits 521 to 52N include at least a smoothing capacitor 55 and an inverter section 56 for each servomotor 36. Specifically, the first conversion circuit 521 includes a converter unit 53, a regenerative circuit 54, a smoothing capacitor 55, and an inverter unit 56. The remaining second conversion circuit 522, ..., And the Nth conversion circuit 52N include a smoothing capacitor 55 and an inverter section 56, respectively. In the conversion circuit 52, only one converter unit 53 and one regenerative circuit 54 are provided in common between the conversion circuits 521 to 52N. The conversion circuit 52 may include a converter unit 53, a smoothing capacitor 55, and an inverter unit 56 for each servomotor 36.

The P line Lp and the N line Ln are connected to the high potential side power supply line La and the low potential side power supply line Lb in the DC power supply circuit 60 via the bypass circuit 80. That is, the P line Lp is connected to the high potential side power supply line La via the first diode 82 of the backflow prevention circuit 81, and the N line Ln is connected to the low potential side power supply line Lb.

The electric circuit 40 of the present embodiment includes M (where M is a natural number) DC power supply circuits 60. In the example shown in FIG. 7, M = 1, but the electric circuit 40 may include two or more M DC power supply circuits 60 (where M is two or more natural numbers). The configuration of the DC power supply circuit 60 is the same as that of the first embodiment. That is, the DC power supply circuit 60 includes a rectifier circuit 61 as an example of the first rectifier circuit, a smoothing capacitor 62, a switching circuit 63, an isolation transformer 64, and a rectifier circuit 65 and a smoothing circuit 66 as an example of the second rectifier circuit. To be equipped.

Then, in the electric circuit 40, a magnitude relationship of N> M is established between the number N of the servomotors 36 and the number M of the DC power supply circuits 60. Here, the number N of the servomotors 36 is equal to the number of conversion circuits 521 to 52N provided for each servomotor 36, which is equal to the number of smoothing capacitors 55 constituting the conversion circuits 521 to 52N. That is, N smoothing capacitors 55 are connected to M DC power supply circuits 60 via the bypass circuit 80. Specifically, the P line Lp of the conversion circuit 52 is connected to the M high potential side power supply lines La of the M DC power supply circuits 60 by the first bypass line L1 via the first diode 82, and is a conversion circuit. The N line Ln of 52 is connected to M low potential side power supply lines Lb of M DC power supply circuits 60 by a second bypass line L2. Then, the number N of the smoothing capacitors 55 is larger than the number M of the DC power supply circuits 60, and the relationship N> M is established. In the example of M = 1 shown in FIG. 7, if the number N of the smoothing capacitors 55 is, for example, four (N = 4), the number of assigned smoothing capacitors 55 per DC power supply circuit 60 is four.

In the first embodiment, the number N of the servomotors 36 and the number M of the DC power supply circuits 60 are in a relationship of N = M, and the number of smoothing capacitors 55 assigned to each of the DC power supply circuits 60 is one. be. On the other hand, in the present embodiment, when a plurality of DC power supply circuits 60 (M ≧ 2) are provided, the number of smoothing capacitors 55 and the DC power supply circuit 60 satisfies N> M, so that the DC power supply circuit 60 The number of smoothing capacitors 55 allocated to each one exceeds "1". Therefore, the electric circuit 40 of the present embodiment satisfying N> M has a time during which the potentials of the P line Lp and the high potential side power supply line La can be held at a higher potential during a momentary power failure than the electric circuit 40 of the first embodiment. Can be further extended. As a result, the frequency with which the injection molding machine 10 can be continued in the event of a momentary power failure becomes higher.

According to the third embodiment, the following effects can be obtained in addition to the same effects as those of the first embodiment.
(4) The servo driver 50 controls a plurality of servo motors 36. The conversion circuit 52 includes at least a smoothing capacitor 55 and an inverter unit 56 as an example of the switching circuit for each of the plurality of servomotors 36. A plurality of smoothing capacitors 55 are connected to the DC power supply circuit 60 via the bypass circuit 80. Therefore, in the event of a momentary power failure of the commercial AC power supply 17, the current due to the electric charges stored in the plurality of smoothing capacitors 55 is supplied to the DC power supply circuit 60, so that the injection molding machine 10 can be continuously operated in the event of a momentary power failure. It gets higher.

(5) The injection molding machine 10 includes N servomotors 36 (where N is a natural number of 2 or more). The electric circuit 40 includes N conversion circuits 521 to 52N and M (where M is a natural number of 2 or more) DC power supply circuits 60. N smoothing capacitors 55 are connected to M DC power supply circuits 60 via a bypass circuit 80. N is more than M (N> M). Therefore, at the time of a momentary power failure of the commercial AC power supply 17, the current due to the electric charge stored in the N smoothing capacitors 55 is supplied to the M DC power supply circuits 60, which are less than N. Therefore, the frequency with which the injection molding machine 10 can be continuously operated in the event of a momentary power failure is further increased.

The embodiment is not limited to the above, and may be changed to the following aspects.
The conversion circuit 52 may include a rectifier (converter unit 53), a smoothing capacitor 55, and a switching circuit (inverter unit 56), and may not include, for example, a regenerative circuit 54.

-In the second embodiment, the number of externally attached second smoothing capacitors 59 may be plural.
In the electric injection molding machine 10 of the third embodiment, the second smoothing capacitor 59 may be externally connected to the servo driver 50 in parallel with the smoothing capacitor 55 as in the second embodiment. ..

In the third embodiment, the capacity of some of the smoothing capacitors 55 among the plurality of (N) smoothing capacitors each of the plurality of conversion circuits provided for each motor is set to be larger than the capacity of the other smoothing capacitors. By increasing the value, the holding time of the control power supply voltage V0 at the time of a momentary power failure may be extended.

When a plurality of DC power supply circuits 60 are provided in the third embodiment, the combination of the number N of the smoothing capacitors 55 constituting the conversion circuit 52 and the number M of the DC power supply circuits 60 is within the range in which N> M is established. May be changed as appropriate. For example, the combination of N pieces and M pieces may be a combination of 3 pieces and 2 pieces, a combination of 4 pieces and 2 pieces, a combination of 4 pieces and 3 pieces, a combination of 5 pieces and 2 pieces, and the like.

-In the third embodiment, one conversion circuit 52 corresponding to a part of the injection motor, the measuring motor, the mold clamping motor, the ejector motor and the mobile motor, and the other conversion circuit 52 corresponding to the other motor. And may have a P line and an N line individually. In this case, two DC power supply circuits 60 are provided, one conversion circuit 52 and one DC power supply circuit 60 are connected via the first bypass circuit 80, and the other conversion circuit 52 and the other DC power supply circuit 60 are connected. And may be connected via the second bypass circuit 80.

-In the third embodiment, N> M is set, but M> N may be used.
-The servo motor 36 may use any kind of motor, for example, an AC motor or a DC motor. In short, it suffices if the motor driver that drives the motor has a rectifier, a smoothing capacitor, and a switching circuit.

10 ... injection molding machine, 11 ... injection device, 12 ... mold clamping device, 15 ... mold, 21 ... heating cylinder, 17 ... commercial AC power supply, 25 ... metering motor, 27 ... heater, 33 ... hydraulic circuit, 34 ... hydraulic Pump, 35 ... switching valve circuit, 36 ... servo motor as an example of motor, 40 ... electric circuit, 41 ... main controller, 50 ... servo driver as an example of motor driver, 52 ... conversion circuit, 521 ... first conversion circuit , 522 ... 2nd conversion circuit, 52N ... Nth conversion circuit, 53 ... Rectifier circuit as an example of a rectifier, 54 ... Regenerative circuit, 55 ... Smoothing capacitor, 54 ... Regenerative circuit, 56 ... Inverter section as an example of a switching circuit, 57 ... Regenerative control circuit, 59 ... Second smoothing capacitor, 60 ... DC power supply circuit, 61 ... Rectifier circuit as an example of the first rectifier circuit, 62 ... Smoothing capacitor, 63 ... Switching circuit, 64 ... Insulated transformer, 65 ... Rectifier circuit as an example of the second rectifier circuit, 66 ... smoothing circuit, 69 ... voltage control circuit, 70 ... heater circuit, 80 ... bypass circuit, 81 ... backflow prevention circuit, Lp ... P line (high potential side power supply line), Ln ... N line (low potential side power supply line), La ... high potential side power supply line, Lb ... low potential side power supply line, Lc ... high potential side power supply line, Ld ... low potential side power supply line, Vac ... AC input voltage, Vpn ... Servo power supply voltage, Vm ... Motor voltage, Vdc ... Control power supply voltage, V0 ... Control power supply voltage which is an example of supply voltage.

Claims (5)

An electric circuit of an injection molding machine having a motor driver that drives and controls a motor.
A motor driver having a conversion circuit that converts an AC of a predetermined voltage input from a commercial AC power supply into a voltage and frequency used for controlling the motor, and a motor driver.
It is equipped with a DC power supply circuit that converts AC of a predetermined voltage input from a commercial AC power supply into DC of a supply voltage lower than the predetermined voltage and outputs it.
The conversion circuit includes a rectifier, a smoothing capacitor, and a switching circuit.
An electric circuit of an injection molding machine, wherein the motor driver and the DC power supply circuit are connected via a bypass circuit including a backflow prevention circuit that allows a current flowing from the smoothing capacitor to the DC power supply circuit. A heater circuit that heats the heater by alternating current supplied from the commercial alternating current power supply, which is common to the direct current power supply circuit, is further provided.
The DC power supply circuit was converted into a first rectifying circuit that converts AC from the commercial AC power supply into rectification, a switching circuit that converts rectification into AC by PWM control, and an isolated transformer that converts the frequency of AC. The electric circuit of an injection molding machine according to claim 1, further comprising a second rectifying circuit that converts alternating current of frequency into rectification, and a smoothing circuit that smoothes rectifying to DC of a supply voltage. The electric circuit of an injection molding machine according to claim 1 or 2, wherein a second smoothing capacitor is externally attached to the motor driver in parallel with the smoothing capacitor. The motor driver controls a plurality of motors and
The conversion circuit includes at least the smoothing capacitor and the switching circuit for each of the plurality of motors.
The electric circuit of an injection molding machine according to claim 1 or 2, wherein a plurality of the smoothing capacitors are connected to the DC power supply circuit via the bypass circuit. The DC power supply circuit is provided with M (where M is a natural number of 2 or more).
The conversion circuit is provided with N (where N is a natural number of 2 or more).
The N smoothing capacitors are connected to the M DC power supply circuits via the bypass circuit.
The electric circuit of the injection molding machine according to claim 4, wherein the N pieces are more than the M pieces.

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