JPH0577287A - Material supply controlling device of electrically-driven injection molding machine - Google Patents

Abstract

PURPOSE:To avoid unevenness in measurement of material by causing an injection screw to stop precisely at a predetermined measurement completion position. CONSTITUTION:When materials are supplied, pressures of the materials detected by a pressure sensor 25 are inputted into a retraction control means 29 and a rotation control means 30 and back pressure command values Y are, inputted into a speed control circuit 31. In the means 29, a forward and backward motor 23 is controlled by means of a servo-amplifier 39 based on retracting speed, number of revolution, and torque corresponding to the deviation between the values Y and actual pressures. In the means 30, number of revolution corresponding to screw positions obtained by an encoder 27 is set at a screw revolution set circuit 34 and outputted from a rotation control circuit 35, whereby rotation of screw is controlled by a servo-amplifier 41, so that back pressure is controlled. On the other hand, when the screw has been retracted to a predetermined position, a switching circuit 33 is actuated to input position and speed reduction command values from a position control circuit 32 into the circuit 31, whereby the screw is stopped precisely at a predetermined position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material supply control device for an electric injection molding machine which uses an electric motor as a drive source for an injection screw.

[0002]

2. Description of the Related Art In general injection molding machines, an injection screw is reciprocally moved by an actuator such as a hydraulic cylinder.
Material (molten resin) supplied to the tip side of the injection screw by moving the injection screw forward
Is to be injected into the mold.

Further, after the injection, the material is melted and supplied by rotating and retreating the injection screw.

On the other hand, in contrast to the above-mentioned conventional injection molding machine,
An electric injection molding machine that drives an injection screw with an electric motor has also been developed.

This type of electric injection molding machine uses two servomotors, one servomotor for forward and backward movement, and its rotational movement is composed of, for example, a ball screw and a ball nut screwed with the ball screw. Convert to linear motion through the motion conversion mechanism, reciprocate the injection screw by this motion conversion mechanism, and use another servo motor for rotation, and rotate the injection screw by this rotation servo motor. ing.

In the electric injection molding machine, the material is supplied by the control shown in FIG.

That is, the reversing control means 2 is provided for the forward-reverse servo motor 1, and the rotation control means 4 is provided for the rotation servo motor 3 to detect the rotation angle of the forward-reverse servo motor 1. The position of the injection screw is detected by the encoder 5 as means, and based on this position information and the back pressure command value A separately input, the reverse control means 2 causes the speed control circuit M1.
And the torque control circuit M2 compare the pressure feedback signal from the pressure sensor 7 with the back pressure command value A to perform back pressure control according to the back pressure command value A. In addition to controlling the rotation speed of the injection screw driven by the rotation servo motor 3, the rotation control means 4 detects the rotation speed of the rotation servo motor 3 by the encoder 6 as the rotation speed detection means. The speed control circuit M3 and the torque control M4 control the rotation speed of the rotation servomotor 3 based on the rotation speed set value B.

That is, the back pressure applied to the material is controlled by controlling the backward speed of the servomotor 1 for forward and backward movement based on the back pressure command value A to control the material supply process.

Here, in the reverse control means 2,
The pressure of the supplied material is detected by the pressure sensor 7, and the back pressure is feedback-controlled.

[0010]

By the way, in the above-mentioned conventional material supply control, since the back pressure of the material is controlled by an independent control system for the backward speed and the rotational speed of the injection screw, Since the command of the rotation servomotor 3 is turned off based on the position information of the forward / backward movement servomotor 1 to terminate the material supply process by the servomotor 3, the injection screw is accurately stopped at a predetermined measurement completion position. It is not possible to do so, and the measurement of the material is likely to be uneven, and there is a demand for countermeasures for that.

[0011]

SUMMARY OF THE INVENTION The present invention provides a material supply control device for an electric injection molding machine which can effectively solve the above-mentioned problems. By detecting the rotation angle of the forward-backward movement motor, the position detection means for detecting the position of the injection screw, the rotation motor for rotating the injection screw, and the pressure of the material supplied by the injection screw are detected. Based on the pressure sensor to detect, the set back pressure command value and the position information from the position detecting means and the pressure information from the pressure sensor, the back pressure at the time of material supply is controlled by controlling the operation of each of the motors. And a controller for controlling, wherein the controller is a retreat control means for controlling the retreat operation of the injection screw during material supply. , A rotation control means for controlling the rotation of the injection screw, wherein the retreat control means comprises a speed control circuit for controlling the rotation speed of the forward / backward movement motor based on the back pressure command value, and the position detection means. Based on the position information and the measurement completion position command value, a position control circuit for controlling the measurement completion position of the forward / backward movement motor, and when the injection screw is retracted to a predetermined position,
Based on the position information, a speed switching circuit that outputs a position from the position control circuit and a speed command value to the speed control circuit is provided, and the rotation control means determines the rotation speed of the rotation motor based on the position information. Based on the rotation speed setting circuit to be set and the output signal from this rotation speed setting circuit,
Based on a deviation amount between the back pressure command value and the actual back pressure output from the pressure sensor, which is operated by an output signal from the rotation control circuit that controls the rotation speed of the rotation motor and the speed switching circuit. And a rotation switching circuit that outputs a speed command value to the rotation control circuit.

[0012]

The material supply control device according to the present invention supplies the back pressure command value to the retreat control means of the controller at the time of material supply,
The pressure signal of the material and the position signal of the injection screw are input from the pressure sensor, and the position signal of the injection screw is input to the rotation control means.

In the reverse control means, based on the back pressure command value, the speed control circuit outputs the command value of the rotation speed to the forward / backward movement motor to continuously control the reverse speed of the injection screw and to rotate the injection screw. In the control means, the rotation speed based on the position information is set by the rotation speed setting circuit, and the command value is output to the speed control circuit to control the rotation speed of the injection screw.

Thus, the back pressure of the material is controlled by controlling the movement of the injection screw.

Then, when the injection screw is retracted to a predetermined position, the speed switching circuit is operated based on the position information, and the position control circuit of the reverse control means moves the position control circuit to stop the injection screw. The speed command value is output and the injection screw is stopped at a predetermined position.

On the other hand, in the rotation control means, at the same time as the operation of the speed switching circuit, the rotation switching circuit is operated and the speed based on the deviation amount between the back pressure command value and the actual back pressure output from the pressure sensor. The command value is output to the rotation control circuit, and the back pressure is maintained at the set pressure.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
Shows an electric injection molding machine according to the present embodiment.

First, a schematic structure of the electric injection molding machine 10 will be described. A heating cylinder 11 which is supplied while a material is melted, a hopper 12 which is mounted on the heating cylinder 11 and which supplies a raw material, and the heating cylinder. An injection screw 13 rotatably fitted in the heating cylinder 11 so as to be movable in the axial direction of the heating cylinder 11, and a driven pulley 1 integrally attached to the injection screw 13.
4, a drive pulley 16 connected to the driven pulley 14 via a timing belt 15, and a drive pulley 16
And a rotation servomotor 17 for rotating the injection screw 13 about its axis, a slider 18 connected to the rear end of the injection screw 13, and the slider 18 and the injection screw 13. A screw shaft 19 for forward and backward movement screwed coaxially, and a servo motor 23 for forward and backward movement connected to the screw shaft 19 for forward and backward movement via a driven pulley 20, a timing belt 21, and a drive pulley 22. , A load cell 24 mounted on the slider 18 and brought into contact with the injection screw 13
And the heating cylinder 1 connected to this load cell 24
A pressure sensor 25 for detecting the pressure of the molten material in 1.
A first encoder 26 that detects the rotation angle of the rotation servo motor 17, a second encoder 27 that detects the rotation angle of the forward-reverse servo motor 23, and signals from the encoders 26, 27, A controller 28 that outputs a drive signal to the servomotors 17 and 23 is provided.

The controller 28 comprises a retreat control means 29 for controlling the retreat operation of the injection screw 13 at the time of supplying the material, and a rotation control means 30 for controlling the rotation of the injection screw 13, and the retreat control means. Reference numeral 29 denotes the forward / backward traveling servo motor 2 based on a back pressure command value Y separately input by a back pressure setting device (not shown).
A speed control circuit 31 for controlling the rotation speed of No. 3, and the second
Based on the position information from the encoder 27 and the measurement completion position command value Z that is separately input, the position control circuit 32 that controls the measurement completion position of the forward-reverse servomotor 23 and the injection screw 13 retreat to a predetermined position. And a speed switching circuit 33 that outputs the position and speed command value from the position control circuit 32 to the speed control circuit 31 instead of the back pressure command value Y based on the position information, and this speed switching circuit. 33 includes a switch SW1 operated by 33, and the rotation control means 30 includes the second SW
A screw rotation speed setting circuit 34 for setting the rotation speed of the rotation servo motor 17 based on position information from the encoder 27, and the rotation servo motor 17 based on an output signal from the screw rotation speed setting circuit 34.
Based on the deviation amount between the back pressure command value Y and the actual back pressure output from the pressure sensor 25, which is operated by the output signal from the rotation control circuit 35 that controls the rotation speed of the pressure sensor 25. A rotation switching circuit 36 that outputs a speed command value to the rotation control circuit 35 instead of the output signal from the screw rotation speed setting circuit 34.
(Only the switches are shown in the figure).

Further, the reverse control means 29 of the controller 28 includes a torque control circuit 37 for controlling the torque of the forward / backward servomotor 23, a switch SW2 for switching a control command value to the torque control circuit 37, and the switch SW2. A torque switching circuit 38 that switches the switch SW2, a servo amplifier 39 that outputs a drive signal to the forward-reverse servomotor 23 based on an output signal from the torque control circuit 37, and a rotation control means 30 are provided. Includes a torque control circuit 40 for controlling the torque of the rotation servo motor 17, and the rotation servo motor 1 based on a signal from the torque control circuit 40.
7 and a servo amplifier 41 that outputs a drive signal.

Next, the operation of the present embodiment thus constructed will be described below.

When the material supply process is started after the injection is completed, the second encoder 27 detects the rotation angle of the forward / rearward traveling servomotor 23 to detect the position of the injection screw 13, and this position information is used for the backward control. The position control circuit 32 of the means 29, the speed control circuit 31, and the screw rotation speed setting circuit 34 of the rotation control means 30 are input, and the material pressure (actual back pressure) is supplied to each control means 29.
It is fed back to 30, and the switch SW1 is switched by the speed switching circuit 33 to input the back pressure command value Y to the speed control circuit 31.

In this state, the reverse control means 29 outputs the back pressure command value of the injection screw 13 and the actual pressure sensor 25 by the servo amplifier 39 based on the back pressure command value Y and the real back pressure information. The forward / backward servomotor 23 is controlled by the retreat speed, the number of revolutions, and the torque corresponding to the deviation amount from the back pressure, whereby the retreat of the injection screw 13 is controlled.

Further, in the rotation control means 30, the rotation speed corresponding to the position of the injection screw 13 is set in the screw rotation speed setting circuit 34 based on the screw rotation speed setting value, and the rotation speed command based on this rotation speed is set. A value is output from the rotation control circuit 35, a torque command value is output from the torque control circuit 40, and the rotation of the injection screw 13 is controlled by the servo amplifier 41 based on these command values.

By such a backward control and a rotational control of the injection screw 13, the back pressure applied to the material by the injection screw 13 is controlled.

On the other hand, in the final stage of the material supplying process, when the injection screw 13 is retracted to a predetermined position,
Based on the position information from the second encoder 27, the speed switching circuit 33 is operated and the switch SW1
Is switched as shown by the solid line in FIG. 3, and the position and speed command values output from the position control circuit 32 are input to the speed control circuit 31.

The position and speed command values output from the position control circuit 32 are deceleration command values, and are speed command values that set the backward speed of the injection screw 13 at the above-mentioned predetermined position to zero at the final retracted position. is there.

Therefore, by such control, the injection screw 13 is stopped at a predetermined position with high accuracy, and as a result, the accuracy of material measurement is improved.

At the same time when the switch SW1 is switched, the rotation switching circuit 36 of the rotation control means 30 is also operated, so that the rotation control circuit 35 is caused to have the back pressure command value Y and the actual back pressure. The rotation speed command value based on the deviation from is input to the torque control circuit 4 so that the back pressure is set by the back pressure command value Y.
0 drives the rotation servomotor 17 via the servo amplifier 41 to control the rotation of the injection screw 13.

As a result, the back pressure is maintained at the set value even when the injection screw 13 is under deceleration control, and from this point as well, the material measuring accuracy is improved.

On the other hand, the torque command value X and the speed control circuit 3
The torque command value calculated based on the output signal from 1 is compared in the torque switching circuit 38, and the switch SW is activated by the operation of the torque switching circuit 38.
2 is switched so that the smaller torque command value is selectively input to the torque control circuit 37.
Excessive torque is prevented at each control stage.

According to the material supply control device 10 of the electric injection molding machine of the present embodiment configured as described above, the back pressure is controlled by the feedback control based on the actual back pressure from the pressure sensor 25, and Injection screw 13
When the injection screw 1
By performing the speed control of No. 3 based on the position information, the injection screw 13 is accurately stopped at a predetermined position.

Even during the stop operation of the injection screw 13 as described above, the rotation of the injection screw 13 is controlled by comparison with the actual back pressure, and the back pressure is maintained at the set value.

As a result, by these synergistic effects, the accuracy of material measurement is greatly improved, and the injection screw 13 and other components are prevented from being damaged due to the injection screw 13 being retracted more than necessary. To be done.

[0035]

As described above, the material supply control device for the electric injection molding machine according to the present invention is capable of detecting the forward / backward movement motor for moving the injection screw forward and backward and the rotation angle of the forward / backward movement motor. The position detection means for detecting the position of the injection screw, the rotation motor for rotating the injection screw, the pressure sensor for detecting the pressure of the material supplied by the injection screw, and the set back pressure command value. And a controller for controlling the back pressure at the time of material supply by controlling the operation of each of the motors based on the position information from the position detection means and the pressure information from the pressure sensor. Sometimes a retreat control means for controlling the retreat operation of the injection screw and a rotation control means for controlling the rotation of the injection screw. Comprising a control means, the reverse control means, a speed control circuit for controlling the rotation speed of the forward-backward movement motor based on the back pressure command value, the position information from the position detection means and the back pressure command value. Based on the position information, when the injection screw is retracted to a predetermined position, a position and speed command from the position control circuit based on the position information when the injection screw is retracted to a predetermined position. A rotation speed setting circuit for outputting a value to a speed control circuit, wherein the rotation control means sets a rotation speed of the rotation motor based on the position information, and an output from the rotation speed setting circuit. Based on a signal, a rotation control circuit for controlling the rotation speed of the rotation motor and an output signal from the speed switching circuit are operated to operate the back pressure finger. And a rotation switching circuit that outputs a speed command value based on a deviation amount between the value and the actual back pressure output from the pressure sensor to the rotation control circuit, and has the following effects. .

The back pressure is controlled by the feedback control based on the actual back pressure from the pressure sensor, and when the injection screw approaches the most retracted position, the speed control of the injection screw is performed based on the position information. The injection screw can be accurately stopped at a predetermined position.

Even during such an injection screw stopping operation, the rotation of the injection screw can be controlled by comparison with the actual back pressure, and thereby the back pressure can be maintained at the set value.

As a result, due to these synergistic effects, the accuracy of weighing the material can be greatly improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a conventional control device in an electric injection molding machine.

FIG. 2 is a schematic configuration diagram of an electric injection molding machine to which an embodiment of the control device of the present invention is applied.

FIG. 3 is a block diagram showing an embodiment of the present invention.

[Explanation of symbols]

 10 Electric Injection Molding Machine 11 Injection Cylinder 13 Injection Screw 17 Servo Motor for Rotation 23 Servo Motor for Forward / Reverse Travel 25 Pressure Sensor 27 Second Encoder (Position Detection Means) 28 Controller 29 Retraction Control Means 30 Rotation Control Means 31 Speed Control Circuit 32 Position control circuit 33 Speed switching circuit 34 Rotation speed setting circuit 35 Rotation control circuit 36 Rotation switching circuit

Claims (1)

[Claims] 1. A forward / backward motor for advancing and retreating an injection screw, position detecting means for detecting a position of the injection screw by detecting a rotation angle of the forward / backward motor, and rotation for rotating the injection screw. Motors, a pressure sensor for detecting the pressure of the material supplied by the injection screw, each of the motors based on the set back pressure command value, the position information from the position detecting means, and the pressure information from the pressure sensor. The controller comprises a controller for controlling the back pressure at the time of material supply by controlling the operation of, and the controller controls the rotation of the injection screw and the retreat control means for controlling the retreat operation of the injection screw at the time of material supply. Rotation control means for controlling the forward / backward movement based on the back pressure command value. A speed control circuit for controlling the rotation speed of the driving motor, a position control circuit for controlling the measurement completion position of the forward / backward moving motor based on the position information from the position detecting means and the back pressure command value, and the injection screw Is moved to a predetermined position, based on the position information, the position from the position control circuit and a speed switching circuit that outputs a speed command value to the speed control circuit, and the rotation control means, A rotation speed setting circuit that sets the rotation speed of the rotation motor based on position information, a rotation control circuit that controls the rotation speed of the rotation motor based on an output signal from the rotation speed setting circuit, and the speed switching Actuated by the output signal from the circuit,
An electric injection molding machine, comprising: a rotation switching circuit that outputs a speed command value based on a deviation amount between the back pressure command value and an actual back pressure output from a pressure sensor to the rotation control circuit. Material supply control device.