JP2017217836A - Motor-driven injection molding machine provided with power storage apparatus - Google Patents

Abstract

The power consumption is relatively large and hardly deteriorates so that power consumption in a molding cycle can be smoothed, and the device can be driven to a safe state for a predetermined period of time even in the event of a power failure, or can be stopped continuously. An electric injection molding machine having a storage device is provided. An electric injection molding machine includes an AC / DC transformer (6) and a DC voltage conversion circuit (17). The AC / DC transformer (6) converts a three-phase AC voltage supplied from the outside into a first DC voltage. The DC voltage conversion circuit (17) boosts the first DC voltage to the second DC voltage, and supplies the second DC voltage to the inverter (12, 13, 14, 15) to supply the motor ( M) is driven. In the present invention, the storage battery (28) and the capacitor (29) are connected in parallel to the DC voltage line (9) through which the first DC voltage flows. [Selection] Figure 1

Description

  The present invention relates to an electric injection molding machine in which each device is driven by a motor. More specifically, the present invention stores a DC voltage supplied to an inverter and supplies it as needed to smooth the power. The present invention relates to an electric injection molding machine provided with an electric power storage device.

  As is conventionally known, an injection molding machine includes a mold clamping device for clamping a mold, an injection device for melting resin and injecting it into a mold, and the like. The screw is driven in the axial direction and the rotational direction. In an electric injection molding machine, these devices are driven by a motor. The electric injection molding machine is provided with a converter, and a three-phase AC voltage supplied from a factory is converted into a DC voltage. Each motor is provided with an inverter, and this DC voltage is converted into a three-phase AC voltage of an arbitrary voltage at an arbitrary frequency by the inverter and supplied to the motor to drive the motor. The molding cycle for molding a molded product consists of a weighing process for melting and weighing the resin, a mold clamping process for clamping the mold, an injection process for injecting the resin, etc. The driving motor, that is, the plasticizing shaft consumes electric power for a long time, but the instantaneous electric power is relatively small. On the other hand, the motor that drives the screw in the axial direction in the injection process, that is, the injection shaft has a short drive time, but consumes a large amount of power. That is, the power consumed greatly varies during the molding cycle. Therefore, a power supply device such as a converter of an electric injection molding machine is required to have a sufficient capacity to meet the maximum power consumed. In addition, since the power consumption varies greatly, the load on the power receiving equipment in the factory is large.

JP 2009-241287 A JP 2013-18152 A

  Patent Document 1 describes an electric injection molding machine including a power storage device that can store a DC voltage by a predetermined amount of power. This power storage device is provided on the DC voltage line side of the power supply device of the electric injection molding machine, and is connected in parallel with a servo amplifier that drives each servo motor. This power storage device has a power storage circuit composed of a coil, a capacitor, two switches, and two diodes, and receives power from a DC voltage to store power in a boosted state in the circuit. can do. In an injection process that requires a large amount of power in a short time, the power stored in the circuit is supplied to the DC voltage side. Then, power consumption can be smoothed in the molding cycle. Therefore, the capacity of the power supply device such as a converter is small, and the burden on the power receiving equipment in the factory can be reduced.

  Patent Document 2 describes an electric injection molding machine including a power storage device similar to Patent Document 1. This electric injection molding machine is also equipped with a power storage device on the DC voltage line, stores power in the power storage device in processes that consume relatively little power, and supplies power in processes that require high power, such as the injection process. In addition, power consumption can be smoothed. The electric injection molding machine described in this document is also characterized in that the electric injection molding machine can be safely stopped during a power failure. That is, at the time of a power failure, each motor can be driven for a predetermined time by the power stored in the power storage device, and the control power for the control device that controls these motors is also supplied from the power storage device. Explaining in detail, the control power is obtained by converting the three-phase AC voltage supplied from the factory to a low-voltage DC voltage by a dedicated control power converter at the normal time. Is obtained by stepping down the DC voltage supplied to the power supply by a DC / DC converter for control power. Thus, the electric injection molding machine described in Patent Document 2 is provided with a DC voltage necessary for each inverter even when a power failure occurs, and ensures control power, and each device for a predetermined time. Can be driven. As a result, each apparatus can be stopped in a safe state.

  Since the electric injection molding machine described in Patent Document 1 includes a power storage device in the DC voltage line, it stores power when there is a margin in power, and supplies it to the DC voltage line when large power is required, The power consumed in the entire molding cycle can be smoothed, which is excellent. Moreover, since the electric injection molding machine described in Patent Document 2 is not only equipped with a power storage device but also obtains a control power source from a DC voltage line, it can be controlled even during a power failure. The electric injection molding machine can be stopped in a safe state, which is excellent. However, there is room for improvement in these electric injection molding machines. Specifically, it is a point regarding the electric power which can be stored. In each of the power storage devices described in Patent Documents 1 and 2, an object for storing power is a capacitor, and generally a capacitor can store relatively little power. A large-capacity capacitor such as an electric double layer capacitor can also be used. However, since a high-performance electric injection molding machine in recent years consumes a large amount of power in an injection process, even such a capacitor is not necessarily used. It cannot be said that there is room in capacity. There is also concern about whether sufficient power can be stored to drive each device to a safe state during a power failure.

  Therefore, for example, in the power storage devices described in Patent Documents 1 and 2, if power is stored in the storage battery instead of the capacitor, the problem of the power that can be stored is considered to be solved. This is because a storage battery can generally store a large amount of electric power as compared with a capacitor. However, another problem arises when power is stored in the storage battery. This is a problem that the storage battery deteriorates early. In the electric injection molding machine described in Patent Documents 1 and 2, the power is stored in the power storage device when the power consumption is small in the molding cycle, and the power is supplied from the power storage device when the power consumption is large. It has become. That is, power storage and discharge frequently occur in the power storage device. Although it can be said that the electric power stored and discharged | emitted for every shaping | molding cycle are small electric power compared with the capacity | capacitance of a storage battery, since the frequency of electrical storage and discharge is high, a storage battery will deteriorate early. Then, the storage battery must be replaced early. In general, since a storage battery is expensive, there is a problem that the cost of an electric injection molding machine increases when frequent replacement occurs.

  An object of the present invention is to provide an electric injection molding machine that solves the above-described problems, and specifically includes an electric power storage device that stores electric power or discharges it as necessary, thereby forming the electric machine. In an electric injection molding machine capable of smoothing power consumption in a cycle, an electric injection molding machine provided with an electric power storage device that has a relatively large capacity but hardly deteriorates, and therefore can suppress the cost required for replacement is provided. The purpose is to do.

  In order to achieve the above object, the present invention provides an AC / DC transformer and a DC voltage conversion circuit in an electric injection molding machine. The AC / DC transformer converts a three-phase AC voltage supplied from the outside into a first DC voltage. The DC voltage conversion circuit boosts the first DC voltage to the second DC voltage, and supplies the second DC voltage to the inverter to drive the motor. In the present invention, the storage battery and the capacitor are connected in parallel to the DC voltage line through which the first DC voltage flows.

That is, in order to achieve the above object, the invention according to claim 1 is an AC / DC converter that converts a three-phase AC voltage supplied from the outside into a first DC voltage; and In the electric injection molding machine comprising: a DC voltage conversion circuit for boosting to a second DC voltage, wherein the second DC voltage is supplied to an inverter and the motor is driven. The DC voltage line to which is supplied is configured as an electric injection molding machine characterized in that a storage battery and a capacitor are connected in parallel.
According to a second aspect of the present invention, in the electric injection molding machine according to the first aspect, the DC voltage conversion circuit steps down the second DC voltage and returns it to the first DC voltage as necessary. It is comprised as an electric injection molding machine characterized by becoming.

  As described above, the present invention provides an AC / DC converter that converts a three-phase AC voltage supplied from the outside into a first DC voltage, and a DC voltage conversion circuit that boosts the first DC voltage to a second DC voltage. In the electric injection molding machine in which the second DC voltage is supplied to the inverter and the motor is driven, the DC voltage line to which the first DC voltage is supplied includes a storage battery and a capacitor. Are connected in parallel. Then, the storage battery and the capacitor store electric power and can be supplied as the first DC voltage as required. Therefore, power consumption in the molding cycle can be smoothed, and the apparatus can be driven to some extent even during a power failure. By the way, there is a problem that when storage and discharge frequently occur in the storage battery for each molding cycle, the storage battery deteriorates early. In the present invention, a capacitor is connected in parallel to the storage battery. Therefore, when a relatively small amount of power is required in a short time, the power is preferentially discharged from the capacitor and then charged to the capacitor in a short time, so there is little discharge from the storage battery and power storage in the storage battery. Does not occur. Therefore, deterioration of the storage battery can be prevented. When power is required for a relatively long time, such as driving during a power failure, the power from the storage battery is supplied, so the electric injection molding machine according to the present invention is in a safe state even during a power failure It is possible to drive and stop the apparatus. According to another invention, the DC voltage conversion circuit steps down the second DC voltage and returns it to the first DC voltage as necessary, so that the regenerative power returns from the inverter as the second DC voltage. Then, it can be returned to the first DC voltage and stored in a storage battery or capacitor.

It is a wiring diagram which shows typically the electric power feeding system of the electric injection molding machine which concerns on embodiment of this invention. It is a circuit diagram which shows the electric power storage apparatus of the electric power feeding system of the electric injection molding machine which concerns on embodiment of this invention. It is a graph which shows typically internal resistance which changes with frequency about each of a storage battery and a capacitor.

  Embodiments of the present invention will be described below. The electric injection molding machine according to the embodiment of the present invention is similar to a conventionally known electric injection molding machine, and includes a mold clamping device for clamping a mold, a heating cylinder and a screw, and an injection for melting and injecting resin. The apparatus includes a device, a projecting device for projecting a molded product, and the like, and each of these devices is driven by a motor such as a servo motor. A power supply system 1 for driving these motors is shown in FIG.

  The power supply system 1 includes an AC / DC converter 6 that converts a three-phase AC voltage from a factory power source 2 into a DC voltage, as in the conventional power injection system of an electric injection molding machine, and includes inverters such as an injection shaft and a plasticizing shaft. A DC voltage is supplied to servo amplifiers 12, 13, 14, 15 for driving the motors M, M,. However, the power feeding system 1 according to the present embodiment is characterized in that a power storage device 7 that stores a DC voltage as power or supplies it as necessary is provided, and the configuration of the power storage device 7 is characterized. . The power storage device 7 will be described in detail below. The DC voltage line for sending a DC voltage is divided into first and second DC voltage lines 9 and 10 so that the power storage device 7 can be provided. More specifically, the power feeding system 1 according to the present embodiment is adapted to receive a three-phase AC voltage from the factory power source 2 by the three-phase AC voltage line 4, and the AC / DC converter 6 converts this to the first. It is converted into a DC voltage and supplied to the first DC voltage line 9. The power storage device 7 is connected to the first DC voltage line 9 and the second DC voltage line 10, and boosts the first DC voltage to the second DC voltage to increase the second DC voltage line 10. To supply. Servo amplifiers 12, 13, 14, 15 such as injection shaft, plasticizing shaft, mold opening / closing shaft, and projecting shaft are connected to the second DC voltage line 10 and supplied with a second DC voltage. Yes.

  As shown in FIG. 2, the power storage device 7 includes a so-called chopper circuit that boosts or lowers a DC voltage, that is, a DC voltage conversion circuit 17, and the DC voltage conversion circuit 17 includes first and second DC voltages. It is interposed in voltage lines 9 and 10. The DC voltage conversion circuit 17 includes a single inductor 18, first and second transistors 20 and 21 made of IGBT, and first and second diodes 23 and 24, as in the conventional chopper circuit capable of step-up / step-down. Become. First, the inductor 18 is provided on the positive voltage line P1 of the first DC voltage line 9. The voltage line extending from the inductor 18 branches into two branches, and the first transistor 20 is interposed in one branch. Are connected to the negative voltage line N, and a first diode 23 is interposed in the other branch and connected to the positive voltage line P2 of the second DC voltage line 10. The first transistor 20 is provided so that a current flows from the positive voltage line P 1 to the negative voltage line N when driven, and the first diode 23 is a positive voltage line of the first DC voltage line 9. A current is provided so as to flow from P1 to the positive voltage line P2 of the second voltage line 10. Therefore, when the first transistor 20 is turned ON / OFF, a current flows from the positive voltage line P1 to the negative voltage line N when ON, and magnetic energy is stored in the inductor 18; Electric power is generated, and the first DC voltage flowing through the first DC voltage line 9 is boosted and supplied to the second DC voltage line 10. A second diode 24 and a second transistor 21 are connected in parallel to the first transistor 20 and the first diode 23, respectively. The second diode 24 is provided so that a current flows from the negative voltage line N to the positive voltage line P1, and the second transistor 21 is driven from the positive voltage line P2 of the second voltage line 10 to the first voltage line P2. The first DC voltage line 9 is provided such that a current flows in the direction of the positive voltage line P1. Therefore, when the second transistor 21 is turned on / off, a current flows from the second DC voltage line 10 to the first DC voltage line 9 when the second transistor 21 is turned on, and magnetic energy is stored in the inductor 18. A current flows from the negative voltage line N to the positive voltage line P1 due to the electromotive force generated in the inductor 18. In this way, the second DC voltage of the second DC voltage line 10 can be stepped down and returned to the first DC voltage of the first DC voltage line 9. Such a DC voltage conversion circuit 17 is controlled by the control device 27, and the control device 27 includes a current from a current sensor 26 provided next to the inductor 18, the first and second DC voltage lines 9, 10 voltages are input, and the first and second DC voltages are controlled to be appropriate voltages.

  In the power storage device 7 according to the present embodiment, the second DC voltage line 10 is provided with a smoothing capacitor 27 for smoothing the second DC voltage as conventionally known. The voltage line 9 is characterized in that two power storage devices having different characteristics are provided in parallel. Specifically, a storage battery 28 that chemically stores power and a capacitor 29 that stores power as static electricity. Since the capacitor 29 protects the storage battery 28 from deterioration as will be described below, it can be referred to as a protective capacitor 29.

  In the electric injection molding machine according to the present embodiment, when the three-phase AC voltage from the factory power supply 2 is normally supplied, the power supplied through the molding cycle becomes substantially constant, thereby increasing the maximum power. It can be driven to suppress. This will be explained. In the molding cycle, when the consumed power is relatively small, such as a plasticizing process, a mold opening / closing process, and a protruding process, the power is stored in the power storage device 7. That is, electric power is stored in the storage battery 28 and the protective capacitor 29. In an injection process that requires a large amount of power in a short time, a large amount of current is supplied to the servo amplifier 12 through the second DC voltage line 10, so that the second DC voltage drops instantaneously. In order to maintain the second DC voltage, the control device 27 controls the DC voltage conversion circuit 17 to boost the DC current from the first DC voltage line 9 and supply the current to the second DC voltage line 10. The second DC voltage is maintained. Then, the voltage of the first DC voltage line 9 decreases instantaneously. When the voltage drops, power is supplied from the storage battery 28 and the protective capacitor 29 to the first DC voltage line 9. Incidentally, as shown in FIG. 3, the internal resistance 31 of the storage battery 28 is always larger than the internal resistance 32 of the protective capacitor 29, and the difference between the internal resistances 31 and 32 is particularly large when the frequency is large. It can be said that the state where the first DC voltage fluctuates instantaneously is a state where the frequency is large. As a result, most of the power supplied to the first DC voltage line 9 comes from the protective capacitor 29 having a smaller internal resistance 32. In the instantaneous voltage fluctuation, the power supplied from the storage battery 28 is relatively small. After the injection process is completed, less power is consumed. The protective capacitor 29 supplied with the electric power is supplied with the direct current of the first direct current voltage converted by the alternating current direct current converter 6 to be stored. The electric power is also stored in the storage battery 28 supplied with a small amount of electric power. Thus, the storage battery 28 and the protective capacitor 29 serve as a buffer, and the power consumption in the molding cycle can be smoothed. By the way, as explained above, since the electric power stored in the storage battery 28 or supplied from the storage battery 28 is small in the molding cycle, the storage battery 28 is hardly deteriorated. That is, the deterioration of the storage battery 29 is suppressed by the protective capacitor 29 having a small internal resistance 32.

  The electric injection molding machine according to the present embodiment can drive and stop each device in a safe state during a power failure. This will be explained. The supply of the three-phase AC voltage from the factory power supply 2 is stopped. That is, a power failure occurs. The mold clamping device and the protruding device may damage the mold depending on the position. Therefore, in order to drive the motors M and M of the mold opening / closing shaft and the protruding shaft, it is necessary to drive the servo amplifiers 14 and 15 to be in a safe state. Then, power is consumed at the second DC voltage 10. In order to maintain the second DC voltage, the controller 27 drives the DC voltage conversion circuit 17 to supply power from the first DC voltage line 9 to the second DC voltage line 10. Since the factory power supply 2 has a power failure, there is no supply of three-phase AC voltage, and supply of DC voltage from the AC / DC converter 7 to the first DC voltage line 9 is stopped. Electric power is stored in the capacitor 29. In particular, since a large amount of power is stored in the storage battery 28, sufficient power can be supplied to the first DC voltage line 9. When the clamping device and the protruding device reach a safe position, they are stopped. Stop the electric injection molding machine.

  The electric injection molding machine according to the present embodiment can be variously modified. For example, in the present embodiment, the DC voltage conversion circuit 17 is provided with the second transistor 21 and the second diode 24, which regenerate power from the second DC voltage line 10 to the first DC voltage conversion circuit 17. Since it is for returning to the DC voltage line 9, this invention can be implemented even if it does not exist. Other modifications are possible, and the AC / DC converter 6 has been described as being composed of a PWM converter, but may be composed of a three-phase bridge rectifier circuit. In addition, although the electric injection molding machine according to the present embodiment has been described to drive each device to a safe state at the time of a power failure and then stop, it is not always necessary to stop. That is, since the storage battery 28 can store sufficient electric power, the electric injection molding machine can be continuously operated without stopping by the power supplied from the storage battery 28 even during a power failure.

DESCRIPTION OF SYMBOLS 1 Power supply system 2 Factory power supply 4 Three-phase AC voltage line 6 AC / DC converter 7 Power storage device 9 1st DC voltage line 10 2nd DC voltage line
12, 13, 14, 15 Servo amplifier 17 DC voltage conversion circuit 28 Storage battery 29 Protection capacitor

Claims (2)

An AC / DC converter that converts a three-phase AC voltage supplied from the outside into a first DC voltage; and a DC voltage conversion circuit that boosts the first DC voltage to a second DC voltage. In the electric injection molding machine in which the direct current voltage is supplied to the inverter and the motor is driven,
An electric injection molding machine, wherein a storage battery and a capacitor are connected in parallel to a DC voltage line to which the first DC voltage is supplied.   2. The electric injection molding machine according to claim 1, wherein the DC voltage conversion circuit steps down the second DC voltage and returns it to the first DC voltage as necessary. Electric injection molding machine.

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