JP5015019B2 - Control method and control device for heater of injection molding machine - Google Patents

Description

  The present invention relates to a control method and a control device for a heater provided in an outer peripheral portion of an injection cylinder, an injection nozzle, etc. of an injection molding machine, and more specifically, a set temperature and a measurement temperature at a required portion of the injection molding machine. A PID calculation unit to which a deviation signal is input, an output processing unit for processing an operation amount signal output from the PID calculation unit, and a heater driving unit to which a correction operation amount signal output from the output processing unit is input And a heater control device for an injection molding machine in which a switching element is driven by an operation control signal output from the heater driving section.

  The molded article of the thermoplastic resin is also molded by an injection molding machine. Such an injection molding machine is well known in the art, and includes a heating cylinder, a screw provided in the heating cylinder so as to be driven in the rotational direction and the axial direction, a screw driving device provided at the rear end of the screw, and the like. It is configured. An injection nozzle is provided at the tip of the heating cylinder, and a hopper is provided near the rear. A plurality of heaters whose heat generation temperatures are individually controlled are provided on the outer peripheral portions of the heating cylinder, injection nozzle, hopper, and the like thus configured. Therefore, when the heat generation temperature of each heater is set and the resin injection molding material is supplied to the predetermined amount from the hopper while the screw is driven to rotate, the resin injection molding material is fed forward. At this time, the resin injection molding material is added from the heater. It is melted by heat, frictional heat generated by the rotation of the screw, etc., and is accumulated in the measuring chamber in front of the heating cylinder. The screw is retracted by the pressure of the accumulated molten resin or suck back. That is, the screw moves in the axial direction. When a predetermined amount is measured, the screw is driven in the axial direction to inject and fill the measured molten resin into the cavity of the mold. Also at this time, the screw moves in the axial direction. When the filled molten resin is cooled and solidified and the mold is opened, a resin molded product is obtained. Such a heater is generally driven by a pulse width modulation method (PWM) using a factory contactor or a solid state relay (SSR) directly from a factory power supply because of equipment cost, configuration, and the like. Further, when the heat capacity of the heating unit is small and driving by the PWM control method causes temperature pulsation, it is driven by phase control using SSR.

  Low-melting-point metal injection molding such as aluminum, magnesium, zinc, bell, bismuth and the like based on a single metal element having a melting point of 700 ° C. or less by an injection molding machine equipped with a heater as described above A metal molded product is formed in the same manner from the material.

  When a molded product is obtained from an injection molding material such as a thermoplastic resin or a low melting point metal having a melting point of 700 ° C. or lower, the temperature of the heating cylinder, injection nozzle, etc. affects the quality of the molded product as described above. For example, if the temperature is low, the flow resistance is large, or the flowability is poor, which may cause molding defects such as short shots and weld lines. As a result, burrs are generated. Therefore, a number of temperature control devices for a heating cylinder of an injection molding machine, that is, an injection cylinder, have been proposed in Patent Documents 1 and 2 and the like. Patent Document 3 proposes a temperature control device for a heater.

JP-A-11-300805 JP2005-22150 JP-A-8-5090

  In Patent Document 1, the injection cylinder is divided into a plurality of temperature control zones in the axial direction, more heaters are provided than the number of temperature control zones, and the selected heater is energized to control the heater range. A temperature control method for an injection cylinder in which is arbitrarily changed is shown. Further, Patent Document 2 discloses a heater energization rate based on a PID calculation result in a control method for turning on / off an AC power supply by feedback control based on a PID operation for a heater provided on an outer peripheral portion of an injection cylinder. Accordingly, there is shown a heating cylinder temperature control method for an injection molding machine in which the minimum time unit of energization ON / OFF is made to coincide with one cycle time of the AC power supply and the heater control is controlled by changing the energization control period itself. Yes.

  Furthermore, Patent Document 3 discloses a temperature control device for a heater, although it is not directly related to an injection molding machine. This temperature control device is equipped with a thermistor for detecting room temperature and power supply voltage detection means, detects the room temperature by the thermistor, determines the variable value according to the room temperature of the pulse width or cycle time according to the set temperature, When the voltage change is detected by the voltage detection means, the variable value of the pulse width or cycle time ON time corresponding to the set temperature is determined. The heater is controlled by adjusting the pulse width or the variable value depending on the room temperature and the voltage change to the pulse width or cycle time ON time corresponding to the set temperature.

In an injection molding machine, the power consumption greatly fluctuates due to operations such as plasticization, injection, pressure holding, and mold opening / closing, and the power supply voltage fluctuates with this fluctuation. Further, when a plurality of injection molding machines are installed, the power supply voltage fluctuates more greatly due to interference with the power consumption of other injection molding machines. Also, the voltage tends to become unstable when using a generator in the factory. When the power supply voltage fluctuates, the temperature stabilizes and the heater output fluctuates and the temperature fluctuates even if the control output is constant. That is, the fluctuation of the power supply voltage hinders the stability of temperature control. The inventions described in each of Patent Documents 1 and 2 can achieve a certain effect, but cannot cope with fluctuations in the power supply voltage. In the invention disclosed in Patent Document 3, when a change in voltage is detected by the power supply voltage detecting means, a variable value of a pulse width or a cycle time corresponding to a set temperature is determined. However, it cannot cope with the change in resistance of the heater due to aging or temperature change.
The present invention has been made in view of the above problems, and a heater control method and control capable of stably controlling the heater even when the power source of the heater of the injection molding machine is unstable. The object is to provide a device. In addition, there is no need to change the characteristics of a controller such as a PID controller created assuming a rated voltage at the time of design, regardless of fluctuations in the power supply voltage of the heater. Another object is to provide a control device.

In order to achieve the above object, the present invention calculates the current heater power from the heater power supply and heater current that supplies power to the heater provided in the main part of the injection molding machine, and calculates the calculated power. Is configured to control the heater output so as to have the same heater power as when driven at the rated voltage. That is, the invention described in claim 1 is a method of controlling a heater provided at a required location of an injection molding machine, and measures the power supply voltage and current of the heater to determine the current power of the heater. It is configured to calculate and to control the output to the heater so that the calculated power becomes the same power as when driven at the rated voltage / current input in advance.
The invention according to claim 2 controls a heater provided in a required portion of an injection molding machine having an injection cylinder and a screw provided in the injection cylinder so as to be driven in a rotational direction and an axial direction. A device that receives a deviation signal between a set temperature and a measured temperature at a required location of an injection molding machine; an output processing unit that processes an operation amount signal output from the PID calculation unit; and the output processing And a heater driving unit to which a correction operation amount signal output from the unit is input, and the switching element is driven by the operation control signal output from the heater driving unit so that the power of the heater is controlled. The correction operation amount signal is obtained by multiplying the operation amount signal by the correction coefficient represented by the following equation in the output processing unit. Configured to be.
Correction coefficient = (V1 · I1) / (V2 · I2)
However, V1 shows the rated voltage of the heater, I1 shows the rated current of the heater,
V2 represents the power supply voltage of the current heater, and I2 represents the current consumption of the heater.
According to a third aspect of the present invention, in the control device according to the second aspect, the operation control signal for driving the switching element is configured to be a pulse width modulation signal.

  As described above, according to the present invention, the output to the heater is made so that the current heater power obtained from the power supply voltage and current of the heater is the same as that when driving at the rated voltage and current. Therefore, even if the power supply voltage of the heater is fluctuated, the temperature of the heater is stabilized and the control is also stabilized. In addition, since the current heater power is controlled so that it becomes the rated power, it can respond to the heater's resistance aging or temperature change, and even if the heater power supply voltage fluctuates, It is also possible to obtain an effect peculiar to the present invention that the characteristics of a controller such as a PID controller created on the assumption of the above is not changed. Without such a correction of the heater power supply voltage fluctuation, for example, if the power supply voltage drops, the output to the heater will drop, the response will be slow, and the response characteristics of the controller at the time of design will not be guaranteed. According to the invention, since the fluctuation of the heater power supply voltage is corrected as described above, the response characteristic is guaranteed. Therefore, the temperature change of the injection cylinder of the injection molding machine in which the screw moves in the axial direction is large and a high response characteristic is required. The present invention can also satisfy this requirement. In addition, since the characteristics of the controller are not changed, an output processing unit can be inserted between the output unit of the conventional controller and the heater driving unit to correct fluctuations in the heater power supply and heater current. . As described above, according to the present invention, since the temperature of the heater is stabilized and the control thereof is also stabilized, a high-quality injection molded product can be obtained.

  Embodiments of the present invention will be described below. An injection molding machine 1 that obtains a molded product from an injection molding material such as a thermoplastic resin or a low-melting-point metal as described above generally rotates in a heating cylinder 2 and the heating cylinder 2 as is well known in the art. It is comprised from the screw 4 provided in the direction and the axial direction so that a drive is possible. And in the outer peripheral part of the injection cylinder 2 and the outer peripheral part of the injection nozzle 3 provided at the tip of the injection cylinder 2, a plurality of heaters 5, 5, ... is provided. These heaters 5, 5,... Are controlled by a heater control device 10 or a control method described below.

  According to the embodiment of the present invention, an AC power regulator (APR) is applied to control the heater. A pulse width modulation control method (PWM) or a phase control method capable of feedback control is applied to the AC power regulator. In the control device 10 to which such a control method is applied, a set temperature and a measured temperature of the injection cylinder 2 are input, an adder 15 that outputs a deviation signal e, and an operation amount calculation that receives the deviation signal e. Unit 20, an output processing unit 25 to which an operation amount u output from the operation amount calculation unit 20 is input, a heater driving unit 30 to which a correction operation amount u ′ output from the output processing unit 25 is input, and the heater The switching unit 35 is configured to have a pulse width or on / off control by an operation control signal s output from the driving unit 30. The adder 15 and the operation amount calculator 20 are connected by signal lines a to g, respectively, and the heater power source D and the heater 5 are connected by a power line E in which a switching unit 35 is interposed.

ただし、Ｋ_ｐ は比例感度を、Ｔ_Ｉ は積分時間を、そしてＴ_Ｄ は微分時間をそれぞれ表している。 The manipulated variable calculation unit 20 can be composed of a proportional operation calculation unit, a proportional integration operation calculation unit, or a proportional differentiation operation calculation unit. In this embodiment, the manipulated variable calculation unit 20 is composed of a proportional integral differentiation operation (PID) calculation unit 20, In this PID calculation unit 20, the operation amount u is calculated by the following equation based on the deviation signal e.

However, K _p is the proportional sensitivity, T _I is the integral time and T _D, represents the derivative time, respectively.

The output processing unit 25 calculates a corrected operation amount u ′ from the operation amount u. The output processing unit 25 stores a heater rated voltage V ₁ and a rated current I ₁ in advance. That is, the heater rated power V ₁ · I ₁ is stored. On the other hand, when the heater 5 is on, the measured heater voltage V ₂ measured by the voltage measuring device 26 of the heater power supply and the consumed heater current I ₂ measured by the current measuring device 27 are input to the output processing unit 25. Is done. Then, the correction operation amount u ′ is calculated by the following equation.

  The heater driving unit 30 outputs a signal pattern for actually turning on / off the heater 5 with respect to the input correction operation amount u ′ (for example, 0 to 100%). That is, when the heater drive unit 30 performs pulse width modulation (PWM) control of the heater 5, the heater drive unit 30 outputs the time corresponding to the input correction operation amount u ′ in the heater drive cycle stored in advance. Operates to turn on. When the phase of the heater 5 is controlled, the phase angle of the power supply voltage is detected, and the output phase angle is adjusted so that the average output power is proportional to the input correction operation amount u ′.

  The switching unit 35 includes switching elements such as an IGBT, a thyristor (SCR), and a solid state relay (SSR), as conventionally known.

  Next, the operation of the above embodiment will be briefly described in terms of image. The heating temperature of each of the heaters 5, 5, ... is set, and the screw 4 is rotationally driven. An injection molding material is supplied from the hopper 6. When the screw 4 is driven to rotate, the injection molding material is melted by frictional heat, shear heat, and heat applied from the heaters 5, 5,. At this time, the screw 4 moves backward by the pressure of the injection molding material in the measuring chamber or by sucking back. When a predetermined amount is measured, the screw 4 is driven in the axial direction to inject and fill the cavity of the mold that is clamped. When the mold is opened after cooling and solidification, a molded product is obtained. Thereafter, molding is performed in the same manner.

When molding as described above, the temperature of the injection nozzle 3 and the temperature of each part of the injection cylinder 2 are individually set. Since the screw 4 also moves in the axial direction, the temperature can be set according to the position of the screw 4. The set temperature and the current temperature at a predetermined location of the injection cylinder 2 are input to the addition point 15, and the deviation signal e is output to the operation amount calculation unit 20. In the operation amount calculation unit 20, the operation amount signal u is calculated as described above and output to the output processing unit 25. If the power supply voltage V ₂ does not change and the resistance value of the heater 5 does not change, the correction coefficient (V ₁ · I ₁ ) / (V ₂ · I ₂ ) does not change. The heater drive unit 30 and thus the switching unit 35 are driven by the operation amount signal u. When the power supply voltage V _2, for example drops, the correction coefficient becomes greater, increased correction manipulated variable signal u 'is output to the heater driving unit 30. From the heater drive unit 30, a pulse width modulation signal s for increasing the pulse width or a phase control signal s for increasing the phase angle is output to the switching unit 35. As a result, the heater 5 is controlled so that the current power of the heater is the same as when it is driven with the rated voltage / current input in advance. At this time, since the current consumption is also measured according to the present embodiment, the output to the heater 5 is constant regardless of the change in the resistance of the heater 5 due to the temperature or the change due to aging. Supply voltage V ₂ is also when high reversed, is controlled to be the same power in the same way.

In the above embodiment, since the correction coefficient is obtained by (V ₁ · I ₁ ) / (V ₂ · I ₂ ), the resistance variation of the heater is compensated, but the resistance variation is small and ignored. When it is possible, or when it is applied to a part where high accuracy is not required, the correction coefficient can be obtained by (V ₁ ² ) / (V ₂ ² ). If this simple heater control device and the heater control device 10 with a correction coefficient of (V ₁ · I ₁ ) / (V ₂ · I ₂ ) are properly used depending on the part of the injection molding machine, the entire injection molding machine The heater control device can be provided at a lower cost.

It is a control block diagram which shows embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection molding machine 2 Injection cylinder 3 Injection nozzle 4 Screw 5 Heater 10 Control apparatus 20 Operation amount calculating part 25 Output processing part 30 Heater drive part 35 Switching part e Deviation signal u Operation amount signal u 'Correction operation amount signal s Operation control Signal (pulse width modulation signal or phase control signal)

Claims (3)

In the heater control method provided at the required location of the injection molding machine, the power supply voltage and current of the heater are measured to calculate the current heater power, and the calculated power is input in advance. A method for controlling a heater of an injection molding machine, wherein an output to the heater is controlled so that the same electric power as that when driving at a rated voltage / current is performed. An apparatus for controlling a heater provided at a required location of an injection molding machine having an injection cylinder and a screw provided in the injection cylinder so as to be able to be driven in a rotational direction and an axial direction includes a set temperature and an injection molding machine. A PID calculation unit to which a deviation signal from a measured temperature at a required position is input, an output processing unit for processing an operation amount signal output from the PID calculation unit, and a corrected operation amount signal output from the output processing unit The heater of the injection molding machine is configured such that the switching element is driven by an operation control signal output from the heater drive unit, and thereby the power of the heater is controlled. A heater control device comprising:
The control device for a heater of an injection molding machine, wherein the correction operation amount signal is obtained by multiplying the operation amount signal by a correction coefficient represented by the following equation in the output processing unit.
Correction coefficient = (V1 · I1) / (V2 · I2)
However, V1 shows the rated voltage of the heater, I1 shows the rated current of the heater,
V2 represents the power supply voltage of the current heater, and I2 represents the current consumption of the heater. The control device according to claim 2, wherein the operation control signal for driving the switching element is a pulse width modulation signal.

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