JPH0667579B2 - Control device of injection molding machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an injection molding machine that drives a screw for plasticizing and measuring a molding material while controlling its position by using a servomotor as a driving source. In particular, it relates to a position control device for the screen (controlled object).

[Conventional technology]

In the injection molding machine, the controllable body is controlled at the completion of filling, the completion of filling after filling, the completion of mold opening, the completion of eject advance, the completion of return of eject re-advance position, the completion of eject retract, and the completion of mold clamping. Must be properly positioned. If the controlled body is not properly positioned at each of these points, problems such as various molding defects and smooth operation of the molding machine occur.

As the positioning control of the controlled object, generally, a hardware method and a software method have been conventionally adopted.

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

On the other hand, the above-mentioned soft method is, for example, the pulse signal from the position sensor that detects the position of the controlled object is counted by the pulse counter, and the deviation between the current position and the target position is calculated by the microcomputer (CPU), This is a method of issuing a motor control command in the direction in which the difference becomes smaller.

[Problems to be Solved by the Invention]

However, these control methods have the following disadvantages. That is, in the former hardware method, when the mode is changed to another 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. .

On the other hand, in the latter soft method, when the controlled object reaches the target position and holds that position, the CPU
After returning to the positioning control step while executing a number of other processing steps after the positioning control processing step, the positioning control step is vacant by about 1 msec. The position of the body changes a little, but always.

The object 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, which is capable of performing proper positioning control of a controlled object.

[Means for Solving the Problems]

In order to achieve the above-mentioned 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, and a position such as a pulse encoder for detecting the current position of the controlled object. A sensor, a position setting means such as a keyboard switch for setting a control target position of the controlled object, and each operation of the molding machine such as mold clamping, injection, pressure holding, mold opening, and eject, Main control means, such as a microcomputer, which 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 the command signal from the main control means and the position sensor. And a correction signal from the controlled object, and outputs the correction movement amount and the correction movement direction of the controlled object as a position correction signal. For example, a sub-control such as a deviation counter. Comprising stages and, and a mode selection means for selecting one of the modes of control performed by the main control unit of the control, or the sub-control means the position control of the controlled device.

The position of the controlled body is controlled by the main control means until the position of the control body reaches the control target position. When the controlled object reaches the control target position, the mode selection means modifies the position control of the controlled object to the position control by the sub control means, and while maintaining the position of the controlled object, the main control means moves the position. It is characterized in that it is configured to perform operation control other than control.

〔Example〕

 Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of the position control device according to the embodiment, and FIG.
The figure is the control flow chart of the controller.

The embodiment shown in FIGS. 1 and 2 shows an example 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 target position of the screen 2 and other molding conditions, and 3
Is a main control unit, which is a read-only memory (ROM) that stores various operation sequences, a random access memory (RAM) that stores various set values and data input from the keyboard 1, and a signal calculation process. It is equipped with a central processing unit (CPU) to perform. 4 is a mode selector, 5 is a D / A converter for converting a digital signal into an analog signal, 6 is a servo amplifier, 7 is a screen 2
, A pulse encoder connected to the output side of the servo motor 7,
Has a resolution such that a signal of 1000 pulses is output by moving 1 mm. Reference numeral 9 is a deviation counter, and 10 is a pulse counter.

The keyboard 1, the screen 2, the main controller 3, the mode selector 4, the D / A converter 5 and the servo amplifier 7 described above,
The pulse encoder 8 constitutes a position control circuit of the screen 2.

Further, in the figure, 11 is a mode selector, 12 is a D / A converter, and 13
Is a servo amplifier, 14 is a mold opening / closing driving servo motor, 15 is a pulse encoder connected to the output side of the servo motor 14, 16 is a deviation counter, and 17 is a pulse counter.
And the above-mentioned keyboard 1, main controller 3, mode selector
11, D / A converter 12, servo amplifier 13, servo motor 1
4, the pulse encoder 15, the deviation counter 16 and the pulse counter 17 constitute a mold opening / closing position control circuit.

Although not shown in the figure, a servomotor is also used in the eject mechanism, and like the position control circuit of the above-mentioned screw and mold opening / closing mechanism, a mode selector, D / A converter, servo amplifier, servomotor, pulse Encoder,
The deviation counter and the pulse counter form a position control circuit of the eject mechanism. This control circuit is almost the same as the above-mentioned control circuit in terms of content, and the drawing is complicated, so that the illustration is omitted. Therefore, the keyboard 1 and the main controller 3 are commonly used in each position control circuit.

FIG. 2 is a position control flow chart. Next, the control operation will be described based on this flow chart.

Until the tip of the heating cylinder (not shown) is filled with a predetermined amount of the molding material by the rotation of the screw 2 (until the filling is completed), the mode selector 4 is mainly controlled as shown in FIG. The mode is set so that the command signal from the unit 3 is input to the D / A converter 5.

Then, in step (hereinafter abbreviated as S) 1, it is determined whether or not the current operation of the injection molding machine is the forward / backward processing of the screw, and if so, it is determined in S2 whether the forward / backward movement of the screw is in progress. If is moving, the process moves to S3, and the acceleration / deceleration operation subroutine by the software method is called.

As shown in FIG. 1, the screw 2 is moved forward or backward by the servo motor 7, but in the case of the position control mode by the above-mentioned software system, the pulse encoder 8 connected to the servo motor 7 Outputs a pulse signal according to the rotation angle of the servo motor 7, and the pulse signal is input to the deviation counter 9 and the pulse counter 10, respectively.

A signal of a control target position A (see FIG. 3) for completion of filling in the screen 2 is stored in advance at a predetermined RAM address of the main control section 3 via the keyboard 1. The current position B (see FIG. 3) of the screen 2 can be detected by sequentially counting the pulse signals output from the pulse encoder 8 with the pulse counter 10. Then, the signal of the target control position A is sent to the CP of the main control unit 3.
Read out to U, calculate the deviation between it and the signal of the current position B, and rotate at a speed corresponding to the deviation value so that the deviation value becomes zero, in other words, if the deviation value becomes small, rotate at a low speed accordingly. As described above, the drive control of the servo motor 7 is performed (routine from S2 to S4).

When the above-mentioned deviation value becomes zero, in other words, when the screen 2 reaches the control target position A, the mode selector 4 is driven by the mode switching signal from the main control unit 3, and the command from the deviation counter 9 is issued. Mode switching is performed so that signals can be input (S5).

After this mode switching, in S6, the operation of positioning (holding) the screen 2 is performed by the hardware method. That is, even if the screen 2 reaches the control target position A, the current position B often deviates from the control target position A due to some disturbance.

Therefore, as shown in FIG. 1, the deviation counter 9 is supplied with the signal of the control target position A from the main control unit 3 and the signal of the current position B from the pulse encoder 8, respectively, and by comparing the two signals, Correction movement amount and correction movement direction for returning the screw 2 to the control target position A [addition (+) direction if the screw 2 is retracted from the control target position A, subtraction if it is too advanced from the control target position A ( −) Direction] is calculated by the deviation counter 9. The information on the corrected movement amount and the corrected movement direction is input as a position correction signal from the deviation counter 9 to the servo motor 7 via the mode selector 4, the D / A converter and the servo amplifier 6, and the rotation direction The rotation angle is controlled.

When the screw 2 reaches the control target position A in this way, the deviation counter 9 performs the position control (positioning control) of the screw 2 apart from the position control by the main control unit 3, which is different from the soft control. , The position of the screen 2 can be corrected at any time, and the positioning (position holding) is sure.

As described above, while the positioning operation is performed by the hardware method, the main control unit 3 controls the operation other than the forward / backward movement according to the operation sequence.

Then, when the operation of the molding machine shifts to the mold opening / closing operation, this time the keyboard 1, the main control unit 3, the mode selector 11, D /
The control operation is executed by a mold opening / closing position control circuit configured by an A converter 12, a servo amplifier 13, a mold opening / closing driving servomotor 14, a pulse encoder 15, a deviation counter 16 and a pulse counter 17. .

That is, almost the same as the position control of the screen 2 described above, it is determined in S7 whether or not the mold is being opened and closed, and if so, the main control unit 3, the mode selector 11, the D / A converter 12, the servo amplifier 13, the servo motor. Whether the control circuit of 14, pulse encoder 15 and pulse counter 17 has performed the software acceleration / deceleration operation (S8) to reach the mold opening / closing control target position.
Monitored by S9.

When the control target position is reached, the mode is switched from the soft method to the hard method in S10, and this time the mode selector
11, D / A converter 12, servo amplifier 13, servo motor 1
4. Positioning (position holding) control by hardware is performed by the control circuits of the pulse encoder 15 and the deviation counter 16.

Although the position control of the screw and the mold opening / closing has been described in the above embodiment, the present invention is not limited to these, and the position control of other operations such as the position control at the time of sucking back and the position control at the time of ejecting forward or backward. It can also be applied to control.

Further, although the servomotor is used as the drive source of the controlled object in the above-mentioned embodiment, the present invention is not limited to this, and the position can be controlled by using another drive source such as a hydraulic circuit. .

〔The invention's effect〕

The present invention is configured as described above, and the position of the controlled object is controlled by the main control means such as a micro computer until the controlled object reaches the control target position. Therefore, another control operation ( For example, it is possible to freely switch to a case where pressure control is performed by switching from the injection process to the pressure holding process, and the control content has a margin.

Further, when the control target position is reached, the position of the controlled object can be constantly monitored and controlled, so that the position accuracy of the controlled object can be maintained high by increasing the gain of the hardware device. Can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining the position control of an injection molding machine according to an embodiment of the present invention, FIG. 2 is a flow chart of its control device, and FIG. 3 is a relationship between a control target position and a current position. It is an explanatory view shown. 1 ... 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.

Claims (4)

[Claims] 1. A drive source for driving a controlled object to be positioned, a position sensor for detecting a current position of the controlled object, a position setting means for setting a control target position of the controlled object, and a molding machine. The main control means that controls the operation and outputs the movement amount of the controlled object as a command signal based on the deviation between the control target position of the controlled object and the current position, and the control target position and position from the main control means. A sub-control unit that compares the current position detected by the sensor and outputs the correction movement amount and the correction movement direction of the controlled object as a position correction signal; and the position control of the controlled object by the main control unit. , Or mode selection means for selecting any of the controls by the sub-control means, the position control of the controlled object by the main control means until the position of the controlled object reaches the control target position, Controlled body is controlled Upon reaching the target position, the position control of the controlled position control by the sub-control means and mode change by the mode selecting means, while performing the position holding of the controlled,
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 body is a screen for plasticizing and measuring a molding material, and the drive source is a servomotor. 3. A read-only memory according to claim 1 or 2, wherein the main control means stores an operation sequence, a random access memory for storing various set values and data, and a signal. And a central processing unit for performing the above-mentioned calculation processing, and the auxiliary control means is constituted by a deviation counter. 4. A control device for an injection molding machine according to claim 2, wherein the control target position of the controlled body is a filling completion position.