JP5801248B2 - Heater power supply method for electric injection molding machine and electric injection molding machine - Google Patents

Description

  The present invention relates to a heater power supply method in an electric injection molding machine and an electric injection molding machine.

  As is well known in the art, an injection molding machine is composed of a pair of molds, a mold clamping device for clamping these molds, an injection device for melting resin and injecting it into the mold, etc. The injection cylinder includes a screw, a plunger, and the like that are driven in the rotation direction and the axial direction in the injection cylinder. In an electric injection molding machine, such a mold clamping device, a screw and the like are driven by servo motors provided independently of each other. Therefore, the electric injection molding machine is provided with a converter, and the three-phase AC voltage supplied to the electric injection molding machine is converted into a predetermined DC voltage. The DC voltage is supplied to an inverter, that is, a servo amplifier provided in association with each servo motor, so that the servo motor is driven.

  There are various types of converters. For example, a diode rectifier circuit including six diodes and a stabilizing capacitor can be employed. The diode rectifier circuit is inexpensive and simple, and can rectify full-wave from a three-phase AC voltage to obtain a direct current. However, the DC voltage to be rectified depends on the voltage value of the three-phase AC voltage. In a factory where an electric injection molding machine is installed, the three-phase AC voltage supplied from the power receiving equipment is various, such as 200 V and 400 V, and the rectified DC voltage value is 282 V, 565 V, and the like. If it does so, it will be necessary to select suitably the inverter suitable for a different DC voltage value, and the product lineup of an electric injection molding machine will increase. There are also other disadvantages, such as the DC voltage being affected by variations in the three-phase AC voltage. On the other hand, a PWM converter provided with a reactor can also be employed as the converter. Since the PWM converter can boost the voltage to a desired voltage, a constant DC voltage can be obtained regardless of the voltage value of the three-phase AC voltage. Then, parts such as inverters can be shared regardless of the three-phase AC voltage in the factory, and the product lineup of electric injection molding machines can be reduced. Furthermore, since a high DC voltage can be obtained, it can be applied to a large and high performance electric injection molding machine that requires a large amount of power.

  Incidentally, a plurality of heaters for heating the injection cylinder are wound around the injection cylinder of the injection device of the electric injection molding machine, and the power supplied to these heaters is the power from the three-phase AC voltage. The electric power from the three-phase AC voltage is turned on / off by a solid state relay or the like, and the electric power is supplied to the heater. At this time, the injection cylinder is controlled to a desired temperature by adjusting the ON / OFF time.

JP 7-329138 A

  Patent Document 1 describes a heater control device for an electric injection molding machine, wherein the power supplied to the heater is power from a DC voltage. In the electric injection molding machine described in Patent Document 1, a three-phase AC voltage is full-wave rectified by a converter and converted into a DC voltage, which is supplied to an inverter for driving a servo motor. Power from voltage is supplied. The heater is energized by a semiconductor switching circuit. Since the power supplied to the heater is from a DC voltage with a constant voltage and current, an effect of stabilizing the heater control can be obtained. In addition, an expensive device such as a solid state relay is not particularly required, and a semiconductor switching circuit can be configured from inexpensive transistors and the like, so that the cost can be reduced.

  Both the conventional method of supplying the power of the three-phase AC voltage to the heater and the method of supplying the DC voltage power rectified in the converter to the heater as described in Patent Document 1 are appropriately used. It is possible to control the temperature by controlling ON / OFF. However, there are also problems to be solved. For example, in the conventional method of supplying electric power of a three-phase AC voltage to the heater, the voltage and current fluctuate due to the AC, so that there is a problem that the control is affected. The three-phase AC voltage may vary depending on the factory where the electric injection molding machine is installed. For example, the three-phase AC voltage may be 200V or 400V as described above. There are also cases such as 220V, 380V, and 415V. Then, if the voltage of the three-phase AC voltage is different, the temperature control must be changed and the cost is increased. Furthermore, in countries and regions where power conditions are poor, the three-phase AC voltage may fluctuate and adversely affect temperature control. A similar problem can be seen in the method described in Patent Document 1. In the electric injection molding machine described in Patent Document 1, the type of converter is not specified, but a three-phase AC voltage is full-wave rectified. Since full-wave rectification is a method of rectifying using six rectifying elements, the converter is presumed to be a diode rectifier circuit. Then, the DC voltage supplied to the heater is determined by the voltage value of the three-phase AC voltage, and the temperature control must be changed according to the voltage value. When the power situation is bad, there is also a problem that the supplied DC voltage is not stable. There are even bigger problems. The standard heater on the market is compatible with a DC voltage of 300V or less, and when the three-phase AC voltage is 220V or more, the DC voltage supplied to the heater is 311V or more. It is not enough and standard products cannot be adopted. In this case, an expensive custom-made heater must be prepared. In addition, a transistor for controlling energization to the heater is required to be compatible with a high voltage, resulting in an increase in cost. Furthermore, there is a problem that the DC voltage supplied to the inverter fluctuates during acceleration / deceleration of the servo motor. If a DC voltage whose voltage fluctuates is used as a power source, temperature control is affected.

  An object of the present invention is to provide a heater power supply method and an electric injection molding machine for an electric injection molding machine that solve the above-described problems, and specifically, a three-phase supplied to the electric injection molding machine. Temperature control is not affected by the voltage value of AC voltage and power quality, that is, the lineup of electric injection molding machines is not increased, and inexpensive standard heaters and inexpensive transistors are used. It is an object of the present invention to provide a heater power supply method for an electric injection molding machine and an electric injection molding machine that can be controlled and the temperature control is not affected even during acceleration / deceleration of a servo motor.

  In the present invention, in order to achieve the above object, the converter of the electric injection molding machine is constituted by a PWM converter provided with a reactor. This PWM converter rectifies the three-phase AC voltage from the outside and boosts it to convert it to a predetermined primary DC voltage. This primary DC voltage is supplied to the servo amplifier that drives the servo motor. A chopper circuit is connected to the voltage line of the primary DC voltage, and the primary DC voltage is stepped down to obtain a secondary DC voltage. The power from the secondary DC voltage is supplied to the heater of the electric injection molding machine.

Thus, in order to achieve the above object, according to the first aspect of the present invention, a three-phase AC voltage supplied from the outside is converted into a primary DC voltage by a PWM converter having a reactor, and the primary DC voltage is converted into a primary DC voltage. In an electric injection molding machine that is supplied to a servo amplifier and driven by a servo motor, a voltage from the primary DC voltage is stepped down by a chopper circuit to obtain a secondary DC voltage, which is controlled by ON / OFF The heater is configured to supply power from the secondary DC voltage as a heater power supply method for an electric injection molding machine.
According to a second aspect of the present invention, in the method according to the first aspect, the primary DC voltage is set to DC 600V or higher, and the secondary DC voltage is set to DC 300V or lower. Configured as a supply method.
According to the third aspect of the present invention, a three-phase AC voltage supplied from the outside is converted into a primary DC voltage by a PWM converter having a reactor, and the servo motor is driven by supplying the primary DC voltage to a servo amplifier. The electric injection molding machine is configured such that a chopper circuit is connected to the voltage line of the primary DC voltage, and a secondary DC that is stepped down by the chopper circuit is connected to a heater controlled by ON / OFF. The electric injection molding machine is configured to be supplied with electric power from a voltage.
According to a fourth aspect of the present invention, in the electric injection molding machine according to the third aspect, the primary DC voltage is DC 600V or more and the secondary DC voltage is DC 300V or less. Configured as a machine.

As described above, according to the present invention, the three-phase AC voltage supplied from the outside is converted into the primary DC voltage by the PWM converter having the reactor, and the primary DC voltage is supplied to the servo amplifier to In the electric injection molding machine that is driven, it is configured as a heater power supply method. Then, since the PWM converter is provided with a reactor, it is intended for an electric injection molding machine that can boost the voltage to a desired voltage when obtaining a primary DC voltage from a three-phase AC voltage. In other words, the electric injection molding machine targeted by the present invention can generate a constant primary DC voltage regardless of the level of the three-phase AC voltage. According to the present invention, the voltage from the primary DC voltage is stepped down by the chopper circuit to obtain the secondary DC voltage, and the power from the secondary DC voltage is supplied to the heater, and the heater is turned on / off. Control by. If it does so, the secondary DC voltage supplied to a heater can also be made into a fixed voltage. Even if the primary DC voltage fluctuates slightly during acceleration / deceleration of the servomotor, the secondary DC voltage can be stabilized by appropriately controlling the chopper circuit. Since electric power is supplied to the heater from such a constant secondary DC voltage, temperature control can be made common and the product lineup of electric injection molding machines can be reduced. In addition, an effect of stabilizing the temperature control can be obtained. This is the maximum effect, but since the secondary DC voltage is a voltage obtained by stepping down from the primary DC voltage, a standard heater can be used, and the switch for turning the heater ON / OFF is also a low voltage. For example. This can reduce the cost.

It is a circuit diagram which shows the power supply device and heater power supply apparatus of the electric injection molding machine which concern on embodiment of this invention.

  Hereinafter, the present embodiment will be described with reference to FIG. The power supply device 1 of the electric injection molding machine according to the present embodiment is also provided with a converter like the conventional power supply device, and rectifies the three-phase AC voltage supplied from the three-phase AC power source 2 and supplies the DC voltage to the servo amplifier 3. However, the converter in the present embodiment includes a PWM converter 5 having reactors 4, 4, and 4. As is well known, the PWM converter 5 includes transistors Tr1, Tr2,... Composed of six IGBTs and six diodes D1, D2,. These diodes D1, D2,... Are arranged in series with two polarities aligned in one direction, and these are arranged in parallel in three rows and connected to positive and negative voltage lines P1, N1 of the primary DC voltage. ing. The voltage line from the three-phase AC power source 2 is connected between the two diodes in each column via the reactors 4, 4, 4. Each of these diodes D1, D2,... Is provided with transistors Tr1, Tr2,..., And when the transistors Tr1, Tr2,... Operate, current flows in the opposite direction to the diodes D1, D2,. ing. As is conventionally known, the transistors Tr1, Tr2,... Can be driven to convert the three-phase AC voltage from the three-phase AC power source 2 into a DC voltage and supply it to the voltage lines P1, N1 of the primary DC voltage. However, it is possible to boost the voltage to a desired DC voltage by the action of the reactors 4, 4, 4. Since the voltage can be boosted in this way, the power of the three-phase AC power supply 2 is 200 V or 400 V in FIG. 1, but the present embodiment can be applied to any of these voltages or any other voltage. In the embodiment, a voltage of 600 V is supplied to the primary DC voltage. As a result, the electric injection molding machine according to the present embodiment is equipped with the servo amplifier 3 for 600 V and is driven by the servo motor M, and can handle any three-phase AC voltage value. It will be possible. Although one servo amplifier 3 and one servo motor M are shown in FIG. 1, actually, a plurality of servo amplifiers 3 are connected to voltage lines P1 and N1 of primary DC voltage, and a plurality of servo amplifiers 3 are connected. The motor M is driven. A capacitor 8 is provided between the positive and negative voltage lines P1 and N1 of the primary DC voltage to suppress the fluctuation of the primary DC voltage.

  Also in the electric injection molding machine according to the present embodiment, the heater 9 heats the injection cylinder of the injection device, but the power supplied to the heater 9 is a DC voltage. More specifically, a step-down chopper circuit 11 is connected to positive and negative voltage lines P1 and N1 of a primary DC voltage that supplies electric power to the servo amplifier 3, and the DC voltage stepped down by the step-down chopper circuit 11 is converted into a heater. 9 is supplied.

  The step-down chopper circuit 11 is conventionally well-known, and includes a transistor 12, a reactor 13, a diode 14, and a capacitor 15, respectively. The transistor 12 is connected to a positive voltage line P1, and a reactor 13 is connected behind the transistor. A diode 14 is provided between the positive voltage line between the transistor 12 and the reactor 13 and the negative voltage line so that a current flows from the negative voltage line to the positive voltage line. A capacitor 15 is provided between the positive voltage line behind the reactor 13 and the negative voltage line. The step-down chopper circuit 15 is connected to the positive and negative voltage lines P2 and N2 of the secondary DC voltage. Although the operation of the step-down chopper circuit 11 is well known in the art and will not be described in detail, when the conduction ratio is controlled by turning the transistor 12 ON / OFF, the primary DC voltage is stepped down in proportion to the conduction ratio. Converted to the next DC voltage. In the present embodiment, the primary DC voltage 600V is converted to a 300V secondary DC voltage. Although not shown in FIG. 1, the secondary DC voltage is monitored by a voltage sensor. Even if the primary DC voltage fluctuates slightly during acceleration / deceleration of the servo motor M, the transistor 12 is appropriately turned on / off. The secondary DC voltage is controlled to be constant by being turned off.

  In the present embodiment, the heater 9 is supplied with power from the stepped down 300 V secondary DC voltage. For example, the heater 9 is connected as follows. One terminal of the heater 9 is connected to the positive voltage line P <b> 2 of the secondary DC voltage, and the other terminal of the heater 9 is connected to a switch 18 for turning ON / OFF the heater 9, i.e., an IGBT transistor 18. It is connected to the negative voltage line N2 of the next DC voltage. Therefore, when the transistor 18 is turned on / off, power can be supplied to the heater 9 or stopped. The transistor 18 is driven to be turned ON / OFF by a signal from a temperature control board 19 which is a controller for controlling the temperature of the injection cylinder. The transistor 18 is provided with a diode 20 in parallel with the transistor 18 for protecting the transistor 18. Although only one heater 9 is shown in FIG. 1, in actuality, a plurality of heaters are connected to the voltage lines P2 and N2 of the secondary DC voltage and are turned on / off independently. It has become.

  In the present embodiment, the heater 9 is supplied with electric power from a secondary DC voltage having a constant voltage. In other words, since the voltage does not change like an AC voltage, the amount of heat generated by the heater 9 is The temperature depends on the ON / OFF time ratio of the transistor 18 and is easy to control. In this embodiment, the primary DC voltage is as high as 600 V in order to drive the servo motor M at high speed and high output, but the secondary DC voltage is as low as 300 V, so the heater 9 A commercially available standard heater can be used. The circuit for driving the heater 9 does not need to take insulation resistance into consideration.

  The electric injection molding machine according to the present embodiment can be variously modified. For example, although the primary DC voltage has been described as being 600 V, other voltages may be used. In an electric injection molding machine that requires a high output, the voltage can be made higher than 600V, and in a relatively inexpensive electric injection molding machine that does not require a high output, a low voltage may be used. Also, the secondary DC voltage can be modified. Considering that most of the standard heaters are 300V or less, there is no problem if the secondary DC voltage is 300V, but if the secondary DC voltage is 300V or less, for example 200V, a heater compatible with 200V is applied. Therefore, there is an advantage that the types of heaters that can be employed are increased.

DESCRIPTION OF SYMBOLS 1 Power supply device 2 Three-phase alternating current power supply 3 Servo amplifier 4 Reactor 5 PWM converter 8 Capacitor 9 Heater 11 Step-down chopper circuit 12 Transistor 13 Reactor 14 Diode 15 Capacitor 18 Transistor 19 Temperature control board 20 Diode Tr1, Tr2, ... Transistor D1, D2, ... Diodes P1, N1 Primary DC voltage line P2, N2 Secondary DC voltage line

Claims (4)

Electric injection in which a three-phase AC voltage supplied from the outside is converted into a primary DC voltage by a PWM converter equipped with a reactor, and the servo motor is driven by supplying the primary DC voltage to a servo amplifier. In the molding machine,
Electric injection molding characterized in that a voltage from the primary DC voltage is stepped down by a chopper circuit to obtain a secondary DC voltage, and electric power from the secondary DC voltage is supplied to a heater controlled by ON / OFF. Power supply method for the heater of the machine.   The method according to claim 1, wherein the primary DC voltage is set to DC 600 V or more, and the secondary DC voltage is set to DC 300 V or less. Electric injection in which a three-phase AC voltage supplied from the outside is converted into a primary DC voltage by a PWM converter equipped with a reactor, and the servo motor is driven by supplying the primary DC voltage to a servo amplifier. A molding machine,
A chopper circuit is connected to the voltage line of the primary DC voltage, and power from the secondary DC voltage stepped down by the chopper circuit is supplied to the heater controlled by ON / OFF. An electric injection molding machine.   4. The electric injection molding machine according to claim 3, wherein the primary DC voltage is DC 600 V or more and the secondary DC voltage is DC 300 V or less. 5.

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