JPH0426292B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a control device for an injection molding machine, and more particularly to injection process control and holding pressure process control of an injection molding machine.

(Prior Art) When molding a resin molded product using an injection molding machine, control is performed according to the molding process. That is, control is performed in the order of molten resin injection, filling, pressure holding, and cooling. Injection speed control and pressure control are performed at the stages of injection, filling (injection process), and pressure holding (pressure holding process) of molten resin. Conventionally, control at the injection, filling, and pressure holding stages was Speed control and pressure control are each independently PID
This is done using a controller, etc.

(Problems to be Solved by the Invention) As described above, in conventional injection molding machines, speed control and pressure control are performed independently. In other words, speed control or pressure control is performed using only one control variable depending on each process. However, in reality, multiple control variables are interrelated, and therefore the injection speed or pressure may deviate from the set value, making injection speed control or pressure control difficult, and as a result, the quality accuracy of the molded product may deteriorate. The problem is that it gets worse.

An object of the present invention is to provide an injection molding machine that can accurately control the injection process and the pressure holding process.

(Means for Solving the Problems) The control device of the present invention provides an injection molding machine equipped with an injection device that injects molten resin into a mold cavity. A calculator receives a set value and actual measured values of a plurality of controlled variables, and calculates the feedback amount of the manipulated variable by multiplying the actual measured value by a feedback coefficient, and calculates the deviation between the target value and the feedback amount. The present invention is characterized in that it includes a compensator that calculates the deviation, corrects the deviation, and outputs the operation amount of the injection device.

(Example) The present invention will be explained below with reference to Examples.

First, an overview of speed/pressure control of an injection molding machine according to the present invention will be explained with reference to FIG.

The control device 1 of the present invention includes a pattern setter 1a, a compensator 1b, and a feedback amount calculator 1c.

The pressure, specific volume, temperature, and other states of the molten resin filled into the mold cavity change depending on the injection speed and injection pressure of an injection device (not shown). Therefore, as shown in FIG.
A curve (pattern f) is determined as a function of (the screw position of the injection device may be used), injection speed v, injection pressure Pa, etc. That is, a pattern is determined as a function of a plurality of control variables.

The above-mentioned pattern is expressed by the following equation (1) using the coordinates of representative points shown as f ₁ to F ₅ in FIG.

f= ₅ 〓 ⁱ⁼¹ f _i N _i ...(1) However, N _i is t expressed as N _i = _n 〓 ^j=1 a _ij t ^m
(time) (a _ij is a coefficient).

The pattern setter multiplies f shown in equation (1) by a coefficient l to calculate r shown in equation (2) below.

r=l·f (2) This pattern (target value) is stored in advance in the pattern setter 1a. On the other hand, the feedback amount calculator 1c has a plurality of control objects 1b of the injection molding machine.
The control amount is input, and the feedback amount is calculated based on this control amount. The adder 1e of the compensator 1b calculates the deviation between the above-mentioned pattern and the feedback amount, and the compensation element 1f, which is composed of a progress circuit or an integrator, performs gain and phase adjustment, and the control target 1d is calculated as the manipulated variable. is input. (The controlled object is controlled by the manipulated variable that indicates the dynamic characteristics of the injection device).

Next, an injection molding machine using a control device according to the present invention will be explained with reference to FIG.

The injection molding machine includes a mold 2 and an injection device 3. The mold 2 has a movable mold 2a and a fixed mold 2b, and these movable mold 2a and fixed mold 2b
An injection cavity 2c is formed. On the other hand, the injection device 3 includes a heating cylinder 3a having a popper 3c, a screw 3b that rotates within the heating cylinder 3a and moves back and forth, and a pressure actuator 4 that rotates the screw 3b and moves it back and forth.

The screw 3b is held by a piston 4a in the pressure actuator 4 coaxially with the piston and rotatably. A plate member 4 is attached to the piston 4a.
b is attached so as not to interfere with the rotation of the screw 3b and to be freely displaceable together with the screw along the screw axis. A speed detector 5 and a position detector 6 for detecting the position of the screw 3b are connected to the plate member 4b via rods, respectively. These speed detector 5 and position detector 6 are a speed converter 5a and a position converter 6c, respectively.
It is electrically connected to the control device 1 via.

A pressure detector 7 is attached to the chamber 4c of the pressurizing actuator 4, and is electrically connected to the control device 1 via a pressure transducer 7a. This control device 1 is connected to a servo valve 8 via a servo valve driving amplifier 8a, and the servo valve 8 is connected to a chamber 4c via a hydraulic flow path 8b. Note that a hydraulic pump 8c is connected to the servo valve 8.

A pressure detector 9 for measuring molten resin pressure is arranged near the tip of the heating cylinder 3a, and this pressure detector 9 is electrically connected to the control device 1 via a pressure transducer 9a. On the other hand, a pressure detector 1 for detecting the pressure of the injection cavity 2c
0 is arranged in the mold 2, and this pressure sensor 10 is likewise electrically connected to a control device via a pressure transducer 10a.

Then, the control device 1 controls the pressure of the chamber 4a.
Pa, screw speed v, screw position y, heating cylinder pressure Po, and mold cavity pressure
The drive pattern (target pattern) of the servo valve is set in advance as a function of P _T .

First, in the injection process, the chamber 4c
A driving pressure is sent from the servo valve 8 to move the piston 4a, that is, the screw 3b, to the left in the axial direction in FIG. At this time, the control device 1 contains the measured chamber pressure Pa′, the measured screw speed v′,
Measured screw position y′, measured heating cylinder pressure
Po′ and the measured cavity pressure P _T ′ are input,
Based on this, the amount of feedback is calculated. That is, if the amount of feedback is x, then x is expressed by the following equation (3).

x=K ₁ Pa′+K ₂ v′+K ₃ y′+K ₄ Po′+K ₅ P _T ′ (3) where K ₁ to _{K 5} represent feedback coefficients.

Next, the deviation between the target pattern and the amount of feedback is determined, and this deviation is determined by the gain and
The phase is adjusted and output to the servo valve 8 as the operating current i. The servo valve 8 changes the opening degree of the servo valve 8 based on this operating current i, and adjusts the driving pressure of the piston 4a.

When the injection process is completed, the next step is the pressure holding process, and in the pressure holding process, the screw drive is controlled in the same way, taking into account the chamber pressure, screw speed, screw position, heating cylinder pressure, and injection cavity pressure. Ru.

In this way, since the movement of the screw is controlled by considering all the measured values of chamber pressure, screw speed, screw position, heating cylinder pressure, and injection cavity pressure, speed surge,
And it becomes possible to prevent excessive pressure.

(Effects of the Invention) As explained above, in the present invention, a target value pattern is set in advance as a function of a plurality of controlled variables, and the feedback amount is calculated based on the actual measured values of the plurality of controlled variables. Since the above target value pattern is corrected by the feedback amount, that is, the manipulated variable is determined by interrelating multiple control variables, it is possible to control the injection process and the pressure holding process with high precision. can. especially,
When switching from the injection process to the pressure holding process, speed surges and sudden changes in pressure do not occur, pressure and speed can be controlled accurately, and good molded products can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an outline of a control device according to the present invention, FIG. 2 is a diagram showing an example of a setting pattern, and FIG. 3 is a diagram showing an injection molding machine in which the control device according to the present invention is used. DESCRIPTION OF SYMBOLS 1... Control device, 2... Mold, 3... Injection device, 4... Pressure actuator, 5... Speed detector, 6... Position detector, 7... Pressure detector, 8...
...Servo valve, 9...Pressure detector, 10...Pressure detector.

Claims (1)

[Claims] 1. Equipped with a heating cylinder in which molten resin is stored and a screw disposed in the heating cylinder so as to be able to move forward and backward, the screw is driven forward to inject the molten resin into the cavity of a mold to form a molded product. In an injection molding machine, a setting device is set with a target value shown as a multidimensional pattern as a function of a plurality of controlled variables over a molding process including an injection process and a pressure holding process, and an actual measured value of the plurality of controlled variables. is input, a calculator calculates the feedback amount by multiplying the feedback coefficient determined for each control amount by the actual measurement value, calculates the deviation between the target value and the feedback amount, and corrects the deviation. and a compensator that outputs the manipulated variable,
A control device for an injection molding machine, characterized in that the screw is driven and controlled based on the operation amount throughout the molding process.