JP2016022621A - Controller of injection molding machine having power source converter control part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller of an injection molding machine with the pressure increase function of a voltage part where the enlargement of a power source device is prevented, further, the energy loss of an electricity storage part is suppressed, and the elongation of the component life of the electricity storage part can be achieved.SOLUTION: The controller of an injection molding machine comprises a power source converter control part where increasing voltage increasing voltage from a power source is changed in accordance with an energy index value as the index of the energy required for the operation of a movable part. In this way, by making the pressure increasing voltage in the electricity storage part into the one in the requisite minimum not always increasing the voltage to the maximum voltage even in every molding condition, the electricity storage energy is consumed without waste, thus the energy loss of the electricity storage part can be suppressed, and further, the elongation of the component life of the electricity storage part can achieved.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a control device for an injection molding machine, and more particularly, to a control device for an injection molding machine that includes a power converter and a control unit that controls the power converter, and controls the injection molding machine by increasing the voltage from the power source.

  In an injection molding machine in which a shaft is driven by a servo motor, it is necessary to supply large electric power to the motor when the shaft is operated at high speed. In particular, in the case of high-speed injection for thin-wall molding and high-speed mold clamping for compression molding, a large amount of power is temporarily supplied to the motor while the motor operates at high speed for a short time. There has been a problem that the power supply device becomes larger. Therefore, a technology for preventing an increase in the size of the power supply device is known by providing a power storage unit in the DC voltage unit of the drive device that drives the servo motor, and boosting the voltage of the power storage unit to store necessary energy during high-speed operation. ing.

Patent Document 1 has a power storage unit that stores power, stores regenerative power generated by the motor during the deceleration period of the motor in the power storage unit, and uses the stored power stored in the power storage unit during the motor acceleration period as drive power. A technique including a power storage circuit to be supplied is disclosed.
Patent Document 2 discloses a technique for operating a power converter in a forward direction so that a voltage between both electrodes of a DC link becomes a predetermined target voltage only for a predetermined period in a molding cycle of an injection molding machine.

JP 2000-141440 A JP 2012-240199 A

In the techniques disclosed in Patent Documents 1 and 2, the voltage of the power storage unit is detected by a voltage detection circuit, and the output of the power converter is controlled so that the detected voltage becomes the target voltage.
By the way, when storing power from the power source to the power storage unit and then discharging from the power storage unit to the motor drive unit, energy loss during power storage and discharge is less than when power is directly supplied from the power source to the motor drive unit. Occur. Therefore, it is desirable that the amount of energy stored in the power storage unit is the minimum amount of energy required at the time of injection.

  However, the amount of energy required at the time of injection varies depending on the volume of the molded product to be molded and the molding conditions, but the electricity storage unit of the injection molding machine has a capacitance so that it can handle various molded products and molding conditions. It is necessary to provide a large power storage unit. Therefore, when the amount of energy required at the time of injection is small, the remaining stored energy used at the time of injection is gradually discharged and lost by the discharge circuit until the start of the next injection, which causes a problem of large energy loss. there were. However, the conventional techniques and the techniques disclosed in Patent Documents 1 and 2 do not show countermeasures for these problems.

  Accordingly, the present invention provides an injection molding machine having a voltage unit boosting function capable of preventing an increase in size of a power supply device, suppressing energy loss of a power storage unit, and extending the life of a component of the power storage unit. An object is to provide a control device.

  In the invention according to claim 1 of the present application, a movable portion, a servo motor that drives the movable portion, a drive device that drives the servo motor, and a voltage from a power source are boosted to a boosted voltage to power the drive device. In a control device for an injection molding machine having a power converter that supplies power and a power storage unit coupled between the power converter and the drive device, an energy index that is an index of energy required for the operation of the movable part There is provided a control apparatus for an injection molding machine having a power converter control unit that changes the boosted voltage according to a value.

  In the invention according to claim 1, an energy index value that is an index of the amount of energy required during operation of the movable part is obtained in advance, and the boosted voltage of the power storage unit is changed according to the obtained energy index value. For this reason, the boosted voltage of the power storage unit is not always boosted to the maximum voltage under any molding condition, but by using the minimum necessary voltage, the stored energy is consumed without waste, and the energy loss of the power storage unit is reduced. In addition, it is possible to extend the life of the parts of the power storage unit.

In the invention according to claim 2 of the present application, in claim 1, the movable part is an injection part, and the energy index value is the kinetic energy of the injection part, the speed of the injection part, the amount of work given to the resin by the injection part, A control device for an injection molding machine is provided, wherein the control device is at least one of an injection pressure, an injection stroke, and a volume of a molded product.
In the invention according to claim 3 of the present application, in claim 1, the movable part is a mold clamping part, and the energy index value is the kinetic energy of the mold clamping part, the speed of the mold clamping part, the work amount of the mold clamping part, There is provided a control device for an injection molding machine characterized in that it is at least one of mold clamping forces.
In the invention according to claim 4 of the present application, in claim 1, the movable part is an ejector part, and the energy index value includes the kinetic energy of the ejector part, the speed of the ejector part, the work amount of the ejector part, and the ejector compression force. There is provided a control device for an injection molding machine, wherein at least one of them is provided.

In the invention according to claim 5 of the present application, in any one of claims 1 to 4, the power converter control unit changes the boosted voltage according to the energy index value and the capacitance of the power storage unit. A control device for an injection molding machine is provided.
In the invention according to claim 5, when the power converter changes the boost voltage, the electrostatic capacity of the power storage unit is taken into account in addition to the energy index value. The voltage can be obtained.

  According to the present invention, the control of an injection molding machine having a voltage step-up function capable of preventing an increase in the size of a power supply unit, suppressing energy loss of the power storage unit, and extending the life of components of the power storage unit. An apparatus can be provided.

It is the figure which showed the servomotor drive circuit of the injection molding machine in this invention. It is the graph which showed the voltage etc. of the electrical storage part at the time of injection | emission in 1st Embodiment. It is the flowchart which showed the flow of the operation | movement in 1st Embodiment. It is the flowchart which showed the flow of the operation | movement in 1st Embodiment. It is the flowchart which showed the flow of the operation | movement in 2nd Embodiment. It is the flowchart which showed the flow of the operation | movement in 3rd Embodiment.

(First embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a servo motor drive circuit of an injection molding machine according to the present invention. A power converter 12 is connected to the power supply unit 10. The power converter 12 is a device that converts the three-phase AC power supplied from the power supply unit 10 into a DC power, and a known PWM converter or the like can be used. Further, before the AC / DC conversion is performed in the power converter 12, the AC / DC conversion can be performed after the voltage from the power supply unit 10 is boosted by a step-up transformer. Reference numeral 14 denotes a power converter control unit which issues an operation command such as a boost voltage command to the power converter 12. A power storage unit 16 is connected to the power converter 12.

In the present embodiment, the power storage unit 16 includes one or more power storage units that are modularized. The power storage unit 16 is connected to a drive device (22, 24, 26, 28) that drives a servo motor. Each driving device (22, 24, 26, 28) is an inverter that converts a direct current into PWM and outputs three-phase alternating current motor driving power. The power storage unit 16 may be composed of a capacitor built in the drive device (22, 24, 26, 28) or the power converter 12, or in addition to a built-in capacitor, a separate capacitor module or battery module may be used. It may be provided. The power storage unit 16 and the drive device (22, 24, 26, 28) may be directly coupled, or a charge / discharge circuit may be provided between the power storage unit 16 and the drive device (22, 24, 26, 28). It can also be provided.
An injection motor 32 drives the screw in the axial direction, and is driven by the driving device 22. Reference numeral 34 denotes a rotary motor that rotationally drives the screw, and is driven by the driving device 24. Reference numeral 36 denotes a mold opening / closing motor that drives the movable plate to advance and retreat in order to open and close the mold, and is driven by the driving device 26. Reference numeral 38 denotes an ejector motor for ejecting a molded product, which is driven by a driving device 28. Each motor is connected to a position / speed detector (42, 44, 46, 48).

  A voltage detection unit 18 detects a voltage between two lines connecting the power converter 12 and the power storage unit 16 as a voltage of the power storage unit 16. The voltage detection unit 18 may be provided in the power storage unit 16. When the power storage unit 16 and the power converter 12 are directly coupled as in the present embodiment, the voltage values of the power storage unit 16 and the power converter 12 are approximately equal. In order to match, it is also possible to provide a voltage detector 18 in the power converter 12. Further, when the power storage unit 16 and the drive device (22, 24, 26, 28) are directly coupled, the voltage values of the power storage unit 16 and the motor drive unit substantially match, so the drive devices (22, 24, 26, 28) can also be provided with the voltage detector 18. Thus, the installation location of the voltage detection unit 18 can be changed as appropriate as long as the voltage value of the power storage unit 16 can be detected directly or indirectly.

An energy index value calculation unit 20 includes an ejector compression force detection unit 52, a mold clamping force detection unit 54, an injection pressure detection unit 56, and a position / speed detection unit (42, 44, 46, 48) of each motor. Are connected to calculate the energy index value and input it to the power converter control unit 14.
In the present invention, an energy index value that is an index of energy required during operation of the movable unit is obtained in advance by the energy index value calculating unit 20, and the boost voltage of the power storage unit is changed according to the obtained energy index value. And

(First embodiment)
When the movable part is an injection part, the energy Ei required at the time of injection is obtained as follows.
Ei = A + B (1)
A: Kinetic energy of injection part (motor and injection mechanism part) = 0.5 × I × ω ²
I: Inertia (motor and injection mechanism) inertia ω: Angular speed of motor (corresponds to injection speed)
B: Work applied to resin = ∫ (P × S × V) dt
P: Injection pressure S: Screw cross-sectional area V: Screw forward speed

A is the kinetic energy of the injection part (motor and injection mechanism part). The kinetic energy A of the injection part is an energy index value of the injection part. I, which is the inertia of the injection unit, is a unique value of the injection molding machine and is stored in advance in the control device. Ω, which is the angular velocity of the motor, is a value that changes according to the set value of the injection speed, which is one of the molding conditions, and is a value that greatly affects the magnitude of the injection energy amount. Therefore, it is desirable to calculate the energy index value of the injection part based on at least the injection speed, and the injection speed becomes the energy index value of the injection part. Note that the injection rate (cm ³ / s) may be used instead of the injection speed (mm / s).

  B is the amount of work given to the resin during injection. The work amount B given to the resin at the time of injection becomes an energy index value of the injection part. P is an injection pressure, which is a value that changes according to a set value of the injection pressure, which is one of the molding conditions. The injection pressure P is an energy index value of the injection part. S is the cross-sectional area of the screw and is stored in the control device in advance. ∫ (V) dt is a value obtained by time integration of the forward speed of the screw during injection, and corresponds to the injection stroke. The injection stroke is one of the molding conditions, and is a value that changes according to the set values of the injection start position and the injection holding pressure switching position. Instead of the injection stroke, B may be obtained based on the volume of the molded product. The injection stroke and the volume of the molded product are energy index values of the injection part.

  Further, since the work amount B given to the resin at the time of injection is relatively small with respect to the kinetic energy A at the time of injection of the injection motor and the injection mechanism, there is a case where the amount of the injection energy is not greatly affected. Therefore, the work amount B given to the resin at the time of injection may be a predetermined fixed value.

On the other hand, the energy Ec that can be supplied from the power storage unit to the motor drive unit at the time of injection is obtained as follows.
Ec = 1/2 · C · (Vmax ² −Vmin ² ) (2)
C: Capacitance of power storage unit Vmax: Boost voltage Vmin: Minimum voltage required to drive the motor

  C is the capacitance of the power storage unit, and Vmin is the minimum voltage required to drive the motor, and is stored in the control device in advance. Vmax is a boosted voltage at the start of injection. Here, in order to suppress energy loss due to excessive power storage, the boosted voltage may be controlled so that Ei = Ec. The boost voltage required to supply the injection energy amount can be obtained from the above formula as follows.

  Prior to the start of injection, the voltage of the power storage unit is boosted to the value of Vmax obtained in advance in 1 and the power is supplied from the power storage unit to the motor drive unit at the time of injection. Energy loss of the power storage unit can be suppressed. Further, the boosted voltage of the power storage unit is not always boosted to the maximum voltage under any molding conditions, but can be made the minimum necessary voltage, thereby extending the life of the components of the power storage unit. In determining the boosted voltage, a value obtained by adding a margin to the voltage value of Vmax obtained by Equation 1 in consideration of the occurrence of an estimation error of the injection energy amount.

  FIG. 2 is a graph showing the voltage of the power storage unit at the time of injection in the present embodiment. FIG. 2A shows a case where the injection speed is high, and FIG. 2B shows a case where the injection speed is low. It is. As shown in FIG. 2, when the speed of the injection part is high, a large amount of energy is required during operation of the movable part, and when the speed of the injection part is low, it is required during operation of the movable part. The amount of energy is reduced. Therefore, depending on the amount of energy required, as shown in FIG. 2, when the injection speed is high, the boost voltage is set to be high, and when the injection speed is low, By reducing the boosted voltage, it is possible to suppress the energy loss of the power storage unit.

FIG. 3 is a flowchart showing an operation flow in the present embodiment. Hereinafter, each step will be described.
(Step SA1) The kinetic energy A of the injection part is calculated based on the injection speed.
(Step SA2) A work amount B applied to the resin by the injection unit is calculated based on the injection pressure.
(Step SA3) Based on the kinetic energy A and the work amount B, an energy index value is calculated.
(Step SA4) The boost voltage of the power storage unit is calculated based on the energy index value.

(Step SA5) It is determined whether it is a boosting section. If it is in the boosting section (YES), the process proceeds to step SA6. If it is not in the boosting section (NO), step SA5 is repeated to wait for the boosting section.
(Step SA6) Boost the voltage from the power source to the boost voltage.
(Step SA7) An injection operation is performed.
(Step SA8) It is determined whether or not the cycle has ended. If the cycle ends (YES), the process ends. If not (NO), the process returns to step SA1.

  Instead of the flowchart of FIG. 3, the energy index value may be calculated based only on the injection speed, as in the flowchart shown in FIG. 4.

(Second Embodiment)
The present embodiment is an application example in the case where energy necessary for mold clamping is supplied from a power storage unit.
The energy index value of the mold clamping part is obtained by equation (3). C is the kinetic energy of the mold clamping part (motor and mechanism part). D is the work amount of the mold clamping part (energy required for generating the mold clamping force). The kinetic energy C of the mold clamping part and the work amount D of the mold clamping part are energy index values of the mold clamping part.
Ef = M + N (3)
M: Kinetic energy of mold clamping part (motor and mold clamping mechanism part) = 0.5 × I × ω ²
I: Inertia of mold clamping part (motor and mold clamping mechanism) ω: Angular speed of motor (corresponding to mold clamping speed)
N: work of clamping portion (energy required to generate the clamping ^{force) = K · X 2/2} = F 2 / (2K)
F: Mold clamping force K: Elastic coefficient of mold clamping mechanism X: Extension amount of tie bar when mold clamping force F is generated

  Equation (2) can also be applied to the case of mold clamping force, and the boosted voltage required to supply the amount of mold clamping energy is obtained as follows from equations (2) and (3).

Before starting mold clamping, boost the voltage of the power storage unit to the boosted voltage obtained in Equation 2, and supply power from the power storage unit to the motor drive unit at the time of mold clamping. Thus, energy loss of the power storage unit can be suppressed.
The mold clamping force may be provided with a mold clamping force detection unit in the mold clamping unit, or may be obtained from a torque generated by the mold clamping motor, a current value, or the like.
The energy index value of the mold clamping part is preferably calculated based on at least the mold clamping speed, and the mold clamping speed is the energy index value of the mold clamping part. The mold clamping force is also an energy index value of the mold clamping part. Further, the energy N necessary for generating the mold clamping force may be a predetermined fixed value.

FIG. 5 is a flowchart showing an operation flow in the present embodiment. Hereinafter, each step will be described.
(Step SC1) An energy index value is calculated based on the mold clamping force.
(Step SC2) The boost voltage is calculated based on the energy index value.
(Step SC3) It is determined whether it is a boosting interval. If it is in the boosting section (YES), the process proceeds to step SC4. If it is not the boosting section (NO), step SC3 is repeated to wait for the boosting section.

(Step SC4) Boost the voltage from the power source to the boost voltage.
(Step SC5) A mold clamping operation is performed.
(Step SC6) It is determined whether or not the cycle is completed. If the cycle ends (YES), the process ends. If not (NO), the process returns to step SC1.

(Third embodiment)
The present embodiment is an application example in the case of supplying energy required from the power storage unit at the time of ejector compression in which the resin inside the mold is compressed using the ejector.
In this case, in equation (3), the ejector speed (ejector compression speed) may be used instead of the mold clamping speed, the ejector compression force may be used instead of the mold clamping force F, and K may be the elastic coefficient of the resin. G is the kinetic energy of the ejector section (motor and mechanism section). H is the work amount of the ejector part (energy required for generating the compressive force). The kinetic energy G of the ejector part and the work amount H of the ejector part are energy index values of the ejector part.

Ec = G + H (4)
G: Kinetic energy of ejector part (motor and ejector mechanism part) = 0.5 × I × ω ²
I: Inertia of ejector section (motor and ejector mechanism section) ω: Angular speed of motor (corresponding to ejector speed)
H: workload of the ejector unit (energy required to generate the compressive ^{force) = K · X 2/2} = F 2 / (2K)
F: compressive force K: elastic modulus of resin X: elastic deformation amount of resin when compressive force F is generated

Expression (2) can also be applied to the case of ejector compression force, and the necessary boosted voltage can be obtained from Expressions (2) and (4) as in the case of mold clamping force.
The ejector compressive force may be provided with an ejector compressive force detecting unit in the ejector unit, or may be obtained from the generated torque or current value of the ejector motor.
The energy index value of the ejector unit is preferably calculated based on at least the ejector speed, and the ejector speed becomes the energy index value of the ejector unit. The ejector compression force is also an energy index value of the ejector section. Further, the energy required for generating the ejector compression force may be a fixed value determined in advance.

FIG. 6 is a flowchart showing an operation flow in the present embodiment. Hereinafter, each step will be described.
(Step SD1) An energy index value is calculated based on the ejector compression force.
(Step SD2) The boost voltage is calculated based on the energy index value.
(Step SD3) It is determined whether it is a boosting interval. If it is in the boost zone (YES), the process proceeds to step SD4. If it is not in the boost zone (NO), step SD3 is repeated to wait for the boost zone.

(Step SD4) Boost the voltage from the power source to the boost voltage.
(Step SD5) Ejector compression operation is performed.
(Step SD6) It is determined whether or not the cycle is completed. When the cycle ends (YES), the process ends. When the cycle does not end (NO), the process returns to step SD1.

  In the embodiments of the present invention, in each of the embodiments, the boosted voltage is calculated by individually obtaining the energy index values in the injection unit, the mold clamping unit, and the ejector unit, but among the injection unit, the mold clamping unit, and the ejector unit, An energy index value can be obtained using a plurality of locations.

DESCRIPTION OF SYMBOLS 10 Power supply part 12 Power supply converter 14 Power supply converter control part 16 Power storage part 18 Voltage detection part 20 Energy index value calculation part 22, 24, 26, 28 Drive device 32 Injection motor 34 Rotation motor 36 Type opening / closing motor 38 Ejector motor 42, 44, 46, 48 Position / speed detector 52 Ejector compression force detector 54 Mold clamping force detector 56 Injection pressure detector

In the invention according to claim 1 of the present application, a movable portion, a servo motor that drives the movable portion, a drive device that drives the servo motor, and a voltage from a power source are boosted to a boosted voltage to power the drive device. And a power storage unit coupled between the power converter and the drive device, wherein the servo motor is a minimum for operating the movable part. An injection molding machine comprising: a power converter control unit that changes power supplied to the power storage unit by changing the boosted voltage of the power converter according to an energy index value that is an index of a required energy amount A control device is provided.

In the invention according to claim 1, an energy index value that is an index of the amount of energy required during operation of the movable part is obtained in advance , the boost voltage of the power converter is changed according to the obtained energy index value, and the power storage unit Because the power supplied to the power supply is changed, the stored energy is wasted by setting the boosted voltage of the power storage unit to the minimum required voltage instead of always boosting to the maximum voltage under any molding condition. As a result, the energy loss of the power storage unit can be suppressed, and the component life of the power storage unit can be extended.

Claims (5)

Moving parts;
A servo motor for driving the movable part;
A driving device for driving the servo motor;
A power supply converter that boosts a voltage from a power source to a boosted voltage and supplies power to the driving device;
A power storage unit coupled between the power converter and the driving device;
In a control device of an injection molding machine having
A control apparatus for an injection molding machine, comprising: a power converter control unit that changes the boosted voltage in accordance with an energy index value that is an index of energy required for the operation of the movable part.   In Claim 1, the said movable part is an injection | pouring part, and the said energy parameter | index value is the kinetic energy of an injection | pouring part, the speed | velocity | rate of an injection | pouring part, the work amount which the injection | pouring part gave to resin, injection pressure, injection stroke, and the volume of a molded article. A control device for an injection molding machine, wherein the control device is at least one of them.   2. The movable part according to claim 1, wherein the movable part is a mold clamping part, and the energy index value is at least one of a kinetic energy of the mold clamping part, a speed of the mold clamping part, a work amount of the mold clamping part, and a mold clamping force. A control apparatus for an injection molding machine.   2. The movable portion according to claim 1, wherein the movable portion is an ejector portion, and the energy index value is at least one of kinetic energy of the ejector portion, speed of the ejector portion, work amount of the ejector portion, and ejector compression force. Control device for injection molding machine.   5. The injection molding machine control device according to claim 1, wherein the power converter control unit changes the boosted voltage according to the energy index value and a capacitance of a power storage unit. 6.