JPH01314130A - Control device of injection molding machine - Google Patents

Abstract

PURPOSE:To perform appropriate positioning control of a material to be controlled, by a method wherein positional control of the material to be controlled is performed until the same arrives at a control target position and when the same arrives at the control target, the position of the same is controlled by monitoring the same always. CONSTITUTION:A signal of a control target position A of completion of filling of a screw 2 is stored in a fixed RAM address of a main control part 3. Pulse signals in accordance with turning angles of a servomotor 7 moving a screw 2 are counted in order with a pulse counter 10 and a present position B of the screw 2 is detected. Driving control of the servomotor 7 is performed so that the deviation value between signals of positions A, B becomes zero. When the screw 2 arrives at the position A, a mode changeover is performed so that a command signal from a deviation counter 9 can be applied to the motor 7. A corrective movement returning the screw 2 to the position A and a correction moving direction are operated by the counter 9 through comparative operation between the signals of the positions A, B, applied to the motor 7 and a rotary direction and rotary angle are controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an injection molding machine that uses, for example, a servo motor as a drive source to drive a screw for plasticizing and metering a molding material while controlling its position.

In particular, it relates to a position control device for the screw (controlled object).

[Conventional technology]

In an injection molding machine, F11 control is performed at the time of completion of filling, the time of completion of suck back after filling, the time of completion of mold opening, the time of completion of eject advance, the time of return to the eject re-advance position, the time of completion of eject retreat, the time of completion of mold clamping, etc. If the controlled object is not positioned correctly at each of these points, problems such as various molding defects will occur and the operation of the molding machine will not proceed smoothly.

Conventionally, the heart method and the software method have been generally used for positioning control of the controlled object.

The above-mentioned hardware method is, for example, inputting a pulse signal from a position sensor that detects the position of the controlled object to a deviation counter, and inputting the command signal to the motor as a count value that increases or decreases depending on the rotation direction of the motor. This is a method for controlling the position (positioning) of a controlled object.

On the other hand, the above-mentioned software method involves, for example, counting pulse signals from a position sensor that detects the position of a controlled object using a pulse counter, and calculating the deviation between the current position and the target position using a microcomputer (CI"'tJ). This method issues motor control commands in a direction that reduces the difference.

[Problem to be solved by the invention]

However, these control methods have the following disadvantages. In other words, in the former hardware method, when changing the mode to other control (for example, pressure control or speed control) during position control, it is necessary to clear the count value of the deviation counter, which makes the control complicated. ,bawl.

On the other hand, in the latter software method, when the controlled object reaches the target position and maintains that position, the CI)U executes many other processing steps after the positioning control processing step and performs positioning again. Since the process returns to the control step, the time interval between the positioning control steps is about 1 millisecond, and during this time the position of the controlled object always fluctuates, albeit slightly, due to disturbances.

The purpose of the present invention is to eliminate such drawbacks of the prior art,
An object of the present invention is to provide a control device for an injection molding machine that can appropriately control the positioning of a controlled object.

[Means to solve the problem]

To achieve the above object, the present invention provides a drive source such as a servo motor for driving a controlled object such as a screw to be positioned.

A position sensor such as a pulse encoder for detecting the current position of the controlled object; and a position setting means such as a keyboard switch for setting the control target position of the controlled object.

Controls each operation of the molding machine, such as mold clamping, injection, holding pressure, mold opening, and ejection, and also commands the amount of movement of the controlled object based on the deviation between the control target position and the current position of the controlled object. The main control means, such as a microcomputer, outputs a signal, and the command signal from the main control means is compared with the detection signal from the position sensor, and the corrected movement amount and corrected movement direction of the controlled object are outputted as position correction signals. For example, a sub-control means such as a deviation counter outputs as follows.

A mode selection means is provided for selecting either mode of control of the position of the controlled object by the main control means or control by the sub-control means.

Then, the position of the controlled object is controlled by the main control means until the position of the controlled object reaches the control target position. When the controlled object reaches the control target position, the mode selection means changes the mode of position control of the controlled object to position control by the sub-control means, and while maintaining the position Wt of the controlled object, the main control means FIG. 1 is a block diagram of a position control device according to an embodiment.

FIG. 2 is a control flowchart of the control device.

The embodiments shown in FIGS. 1 and 2 show examples in which a servo motor is used as a drive source to perform various position controls.

In Fig. 1, 1 is a keyboard for inputting and setting the control position of the screw 2 and other molding conditions;
is the main control unit, which includes a read-only memory (ROM) that stores various operation sequences, a random access memory (RAM) that stores various setting values and data input from the keyboard 1, and a signal arithmetic processing unit. It is equipped with a central processing unit (CR'u) for performing the processing. 4 is a mode selector, 5 is a D/A converter that converts a digital signal into an analog signal, and 6 is a servo amplifier.

7 is a servo motor that moves the screw 2 back and forth, 8 is a pulse encoder connected to the output side of the servo motor 7, and when the screw 2 moves 1 mm, 100
It has the resolution to output a 0 pulse signal. 9 is a deviation counter, and IO is a pulse counter.

The aforementioned keyboard l, screws 2. Main control unit 3, mode selector 4, D/A converter 5 and servo amplifier 7,
The pulse encoder 8 constitutes a position control circuit for the screw 2.

Furthermore, in the figure, 11 is a mode selector, 12 is a D/A converter, 13 is a servo amplifier, 14 is a servo motor for driving the mold opening/closing, 15 is a pulse encoder connected to the output side of the servo motor 14, and 16 is a pulse encoder connected to the output side of the servo motor 14. The deviation counter 17 is a pulse counter. The mold opening/closing position control circuit is controlled by the keyboard 1, main control unit 3, mode selector 11.0/A converter 12, servo amplifier 13° servo motor 14, pulse encoder 15, deviation counter 16, and pulse counter 17. It is configured.

Although not shown in the figure, a servo motor is also used for the eject mechanism, and in the same way as the position control circuit of the screw and mold opening/closing mechanism described above, a mode selector, D/A converter, servo amplifier, servo motor, pulse encoder,
The deviation counter and the pulse counter constitute a position control circuit for the eject mechanism. This control circuit.

The contents are almost the same as the control circuit described above, and one illustration is omitted because the drawing becomes complicated. Therefore, the keyboard 1 and main control section 3 are commonly used in each position control circuit.

FIG. 2 is a flowchart of one-position control.

Next, the control operation will be explained based on this flowchart.

Until a predetermined amount of molding material is filled into the tip of the heating cylinder (not shown) by the rotation of the screw 2 (until the filling is completed), the mode selector 4 switches to the main controller 3 as shown in FIG. The mode setting is such that a command signal from the D/A converter 5 is input to the D/A converter 5.

And in step (hereinafter abbreviated as S) l,
It is determined whether the current operation of the injection molding machine is that the screw is moving forward or backward, and if so, it is determined in S2 whether the screw is moving forward or backward, and if the screw is moving, S2 is executed.
3, a subroutine for acceleration/deceleration operation using the software method is called.

As shown in FIG. 1, the screw 2 is moved forward or backward by the servo motor. In the position control mode using the software method described above, the pulse encoder 8 connected to the servo motor 7 outputs the servo motor A pulse signal is output in accordance with the rotation angle of 7, and this pulse 46 is input to the deviation counter 9 and the pulse counter 10, respectively.

The control indication 1! of the completion of filling in the screw 2 is stored in a predetermined RAM address of the main control unit 3 via the keyboard 1. A signal (see FIG. 3) is stored in advance. By sequentially counting the pulse signals output from the pulse encoder 8 mentioned above with the pulse counter IO,
The current position B of the screw 2 (see FIG. 3) can be detected.

Then, the signal of the target control position 1g1A is sent to the main control section 3 by C.
Read it to the PU, calculate the deviation between it and the signal of the current position B, and rotate at a speed according to the deviation value so that the deviation value becomes zero.In other words, if the deviation value becomes small, it will rotate at a low speed accordingly. The drive control of the servo motor is performed as follows (routine from S2 to 84).

When the aforementioned deviation value becomes zero, in other words, when the screw 2 reaches the control target position mA, the mode selector 4 is driven by the mode switching signal from the main control section 3, and the command signal from the deviation counter 9 is activated. The mode is switched to allow input (S5).

After this mode switching, the screw 2 is positioned (position held) by a hardware method in S6. That is, even if the screw 2 reaches the control target position A, the current position [B] often deviates from the control target position 1fA due to some disturbance.

Therefore, as shown in FIG. 1, the signal of the control target position A from the main control section 3 and the signal of the current position B from the pulse encoder 8 are respectively input to the deviation counter 9, and by comparing the two signals, Control screw 2 to target position flI
The corrected movement amount and corrected movement direction to return to A (if the screw 2 has retreated from the control target position A, the addition (+) direction; if the control target position has moved too far from A, then the subtraction (-) direction). The deviation counter 9 performs calculation processing. Information on the corrected movement amount and corrected movement direction is then input as a position correction signal from the deviation counter 9 to the servo motor 7 via the mode selector 4, D/A converter 5, and servo amplifier 6, and the rotation direction thereof is and the rotation angle is controlled.

When the screw 2 reaches the control target position A in this way, the position control by the main controller 3 is removed and the deviation counter 9
Since the position control (positioning control) of the screw 2 is performed using the above, unlike software-based control, the position of the screw 2 can be constantly corrected and positioning (position maintenance) can be ensured.

In this way, you can use the hard method to get +i! (While the xth operation is being performed, the main control section 3 performs operation control other than the forward and backward movement of the screw according to the operation sequence.

Then, when the operation of the molding machine shifts to the mold opening/closing operation, the keyboard 1, main control section 3, mode selector 11. D
/A converter 12. Servo amplifier 13, mold opening/closing drive servo motor 14, pulse encoder 15, deviation counter 1
A control operation is executed by a mold opening/closing position control circuit constituted by a mold opening/closing position control circuit 6 and a pulse counter 17.

That is, in substantially the same way as the position control of the screw 2 described above, it is determined in S7 whether the mold is being opened or closed, and if so, the main control section 3, mode selector 11. D/A converter 12. Servo amplifier 13, servo motor 14, pulse encoder 15
The control circuit of the pulse counter 17 performs software acceleration and deceleration operations (S8), and it is monitored at step 89 whether or not the mold opening/closing control target position has been reached.

When the control target position is reached, the mode must be switched from the software method to the hard method using SlO, and the mode selector 11. A control circuit including a D/A converter 12, a servo amplifier 13, a servo, a motor 14, a pulse encoder J' 15, and a deviation counter 16 performs positioning (position holding) control using a hardware method.

In the above embodiments, position control of the screw and mold opening/closing was explained. However, the present invention is not limited to these.1 For example, position control during suckback, position control during eject advance or retreat, and other operations may be performed. It can also be applied to positioning control.

Further, in the above embodiment, a servo motor was used as a drive source for the controlled object, but the present invention is not limited to this, and it is also possible to perform position control using other drive sources such as a hydraulic circuit. .

〔Effect of the invention〕

The present invention has the above-described configuration, and until the controlled object reaches the control target position, the position is controlled by the main control means such as a microcomputer, so other control operations (e.g. In the case of switching from the injection process to the pressure holding process to control the pressure, etc.), there is flexibility in the content of control.

Moreover, when the control target position is reached, 81! Since the position of the control body can be constantly monitored and controlled, the position accuracy of the controlled body can be maintained at a high level by increasing the gain of the hardware device, thereby improving molding quality.

[Brief explanation of the drawing]

Fig. 1 is a block diagram for explaining position control of an injection molding machine according to an embodiment of the present invention, Fig. 2 is a flowchart of the control device, and Fig. 3 shows the relationship between the control target position and the current position. It is an explanatory diagram. ■...Keyboard. 2...Screw, 3...Main control unit, 4.11...Mode selector. 7.14... Servo motor, 8.15... Pulse encoder, 9.16...
... Deviation counter, 10.17 ... Pulse counter. A: Control target position, B: Current position. Figure 1

Claims (4)

[Claims] (1) A drive source that drives the controlled object to be positioned, a position sensor that detects the current position of the controlled object, a position setting means that sets the control target position of the controlled object, and controls each operation of the molding machine. A main control means that outputs the movement amount of the controlled object as a command signal based on the deviation between the control target position and the current position of the controlled object, and a control target position from the main control means and a position sensor. a sub-control means that compares the detected current position and outputs the corrected movement amount and corrected movement direction of the controlled object as a position correction signal; and the main control means controls the position control of the controlled object; mode selection means for selecting one of the controls by the sub-control means; the main control means controls the position of the controlled object until the position of the controlled object reaches the control target position; When the body reaches the control target position, the mode selection means changes the mode of position control of the controlled body to position control by the sub-control means, and while maintaining the position of the controlled body,
1. A control device for an injection molding machine, characterized in that the main control means is configured to perform operation control other than position control of the controlled object. (2) The control device for an injection molding machine according to claim (1), wherein the controlled object is a screw for plasticizing and metering the molding material, and the drive source is a servo motor. (3) In claim (1) or claim (2),
The main control means includes a read-only memory that stores operation sequences, a random access memory that stores various setting values and data, and a central processing unit that performs signal arithmetic processing, and the sub-control means includes a deviation counter. A control device for an injection molding machine, comprising: (4) The control device for an injection molding machine according to claim (2), wherein the control target position of the controlled object is a filling completion position.