JP2576308B2 - Electric injection molding machine control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mode for injecting a molten resin into a mold, a pressure-holding mode for keeping the pressure in the mold at a predetermined value, and a back pressure mode for supplying a raw material to a heating cylinder. The present invention relates to an electric injection molding machine control system in which control in each mode is performed.

[0002]

2. Description of the Related Art FIG.
FIG. 1 is a block diagram showing a conventional control method of an electric injection molding machine disclosed in Japanese Patent Application Publication. In the figure, 1 is a screw, 2
Is a heating cylinder, 3 is a screw shaft, 4 is a limit switch that detects a predetermined position of the screw in the axial direction, 5 is a pressure detector that detects pressure applied to the screw 1, 6 is a screw shaft 3 in the front-rear direction, Is a servo motor for driving the motor in the rotation direction, 7 is a detector provided on the servo motor 6 for detecting the position and moving speed of the screw shaft, 8 is a pressure command, 10 is a position command, and 100 is the driving power of the servo motor 6. Is a servo drive device that supplies

In the servo drive device 100, reference numeral 101 denotes a subtractor for calculating a deviation between an external pressure command 8 and a pressure feedback value indicating the current pressure from the pressure detector 5, and 102.
Is a pressure control gain for amplifying the pressure deviation value from the subtracter 101 to a value obtained by multiplying the pressure deviation value by a predetermined control coefficient, and 103 is a deviation between a position command 10 from the outside and a position feedback value indicating the current position from the detector 7. The subtractor 104 is a subtractor 104.
The position control gain 105 amplifies the position deviation value from 3 to a value obtained by multiplying the value by a predetermined control constant. Reference numeral 105 denotes a deviation between a speed command obtained by the position control gain 104 and a speed feedback value indicating the current speed from the detector 7. A subtractor 106 is a speed control gain for amplifying the speed deviation value from the subtractor 105 to a value multiplied by a predetermined control constant, and 107 is a speed control gain 1
The current control clamp 108 clamps the output from the control signal 06 to a value corresponding to the output value of the pressure control gain 102. The current control clamp 108 outputs the output corresponding to the current command of the servo motor 6 from the current control clamp 107 and the current supply current to the servo motor 6. A subtracter 109 calculates a deviation from the indicated current feedback value. A current control gain 109 amplifies the current deviation value from the subtracter 108 to a value obtained by multiplying the current deviation value by a predetermined control constant.
A power amplifier 111 drives the servo motor 6 with a current corresponding to the output of the reference numeral 9. A current detector 111 detects a drive current of the servo motor 6.

Next, the operation of the electric injection molding machine control system configured as described above will be described. First, in the injection mode, a position command 10 indicating the target position of the screw 1 at the time of injection is input from the outside, and a position feedback value indicating the current position of the screw 1 from the detector 7 connected to the servomotor 6. Is obtained by a subtractor 103, a predetermined control constant is multiplied by a position control gain 104 to obtain a speed command, and a speed feedback indicating the current moving speed of the screw shaft 3 from the detector 7 is provided. A deviation from the value is obtained by a subtractor 105, and this deviation value is multiplied by a predetermined control constant by a speed control gain 106. The current command is applied to a current clamp 107, and the maximum positive and negative values are limited to a predetermined value. Is applied to Here, a deviation from a current feedback value indicating a servo motor driving current from the current detector 111 is obtained, and a predetermined control constant is multiplied by a current control gain 109 to the deviation value, amplified by the power amplifier 110, and the servo motor 6 is driven. Driven. In this manner, the screw 1 is moved at a predetermined speed to a predetermined position while rotating, and the heating cylinder 2 is rotated.
The molten resin in the mold at an appropriate injection speed (not shown)
It is injected inside.

When the mold is filled with the molten resin, the mode is switched from the injection mode to the pressure-holding mode, and thereafter control is performed to set the pressure in the mold to an appropriate value. That is, in the dwell mode,
A pressure command 8 for instructing a target pressure in the mold is input from the outside, and a pressure feedback indicating the pressure applied to the screw shaft 3 from the pressure detector 5 (equal to the pressure in the mold in the pressure holding mode). A deviation from the value is obtained by a subtractor 101, and a predetermined control constant is added to the deviation value by a pressure control gain 1
02 and applied to the current clamp 107. On the other hand, since the screw 1 does not move, the position deviation and the velocity deviation are both 0, and the current command applied to the subtractor 108 via the current clamp 107 is only based on the pressure deviation. The deviation between the current command and the current feedback value from the current detector 111 is added to the current control gain 109 from the subtractor 108, multiplied by a predetermined control constant, amplified by the power amplifier 110, and the servo motor 6 is driven. . In this way, the pressure in the mold, that is, the pressure applied to the screw shaft 3 is controlled to a predetermined value.

When the pressure-holding mode is completed, the cooling and solidification of the molten resin in the mold is started, and a predetermined pressure lower than the pressure in the pressure-holding mode is maintained. The mode is switched to a back pressure mode in which the raw material is melted and supplied into the heating cylinder 2. That is, in the back pressure mode, a pressure command 8 for instructing a target pressure in the heating cylinder 2 is input from outside, and a difference between the pressure command 8 and a pressure feedback value from the pressure detector 5 is obtained by the subtractor 101, and this difference value is obtained. Is multiplied by the pressure control gain 102 in the same manner as in the pressure holding mode, and is applied to the subtractor 108 through the current clamp 107 as a current command corresponding to the pressure deviation.

On the other hand, a position command 10 for instructing a target retreat position of the screw 1 in the back pressure mode is input from the outside,
Based on this and the position feedback value and the speed feedback value from the detector 7, the subtractor 103, the position control gain 104, the subtractor 105, and the speed control gain 106 pass through the current clamp 107 and respond to the position deviation to the subtractor 108. The current command is applied to the subtractor 108. When the servo motor 6 is driven by the power amplifier 110 with the power according to the current command and the current control gain 109, and the back pressure applied to the screw shaft 3 is controlled to a predetermined value, the servo motor 6 moves backward and reaches the final target position. The servomotor 6 is stopped by a signal from the limit switch 4 or the servomotor detector 7.

[0008]

The conventional control method of the electric injection molding machine has the following problems since it is configured as described above. (1) In the conventional method, since the control constant based on the pressure deviation is the same in both the pressure holding mode and the back pressure mode, optimum control cannot be performed in both the pressure holding and the back pressure control. (2) In the conventional method, the current clamp command is used in both the pressure-holding mode and the back-pressure mode. Therefore, particularly in the back-pressure control, the current limitation of the positive and negative polarities cannot be performed. Could not be performed with high precision. (3) In the conventional method, since the pressure holding control and the back pressure control are in the same control loop, when the pressure does not increase to the set pressure during the back pressure control, the screw advances and the injection material comes out. was there. (4) In the conventional method, since the calculated value of the deviation between the pressure command and the pressure feedback is given as the current clamp command, the pressure holding and back pressure modes cannot be switched smoothly.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the control in the pressure-holding mode and the control in the back-pressure mode can be performed with optimum and high accuracy. It is an object of the present invention to provide an electric injection molding machine control system capable of smoothly switching between pressure holding and back pressure modes without advancing a screw.

[0010]

According to the first aspect of the present invention, a control constant for multiplying the pressure deviation in the pressure holding mode and a control constant for multiplying the pressure deviation in the back pressure mode are different values. thereby to switch when switching the pressure holding mode and the back pressure mode, when the holding pressure mode and back pressure mode, the position command value and the final target position of each mode, until the screw reaches the final target position Is to prevent the deviation output between the position command value and the position feedback value, and stop the reversal of the servomotor by the position deviation output whose polarity has been reversed when the final target position has elapsed.

According to a second aspect of the present invention, a pressure
Control constant that multiplies the pressure deviation during
The control constant multiplied by the pressure deviation is set as a different value,
When switching between pressure holding mode and back pressure mode
In addition, in the back pressure mode, when the pressure feedback value becomes equal to or less than the pressure command value, the pressure deviation output is prevented.

According to a third aspect of the present invention, a pressure
Control constant that multiplies the pressure deviation during
The control constant multiplied by the pressure deviation is set as a different value,
When switching between pressure holding mode and back pressure mode
In addition, a value obtained by adding the position deviation to the deviation between the pressure command value and the pressure feedback value is used as the servo motor speed command.

[0013] The invention described in claim 4 of the present invention is the present invention.
In the invention described in the third aspect, a speed limiter for clamping a speed command value within a predetermined range is provided.

[0014]

According to the first aspect of the present invention, the control is performed with different control constants in the pressure holding mode and the back pressure mode having different pressure command values, so that the pressure can be stabilized without being affected by the mechanical system or the injection material. the control of the optimum is performed, when the holding pressure mode and back pressure mode, the screw although until reaching the final target position servo motor depending only on the pressure deviation is controlled, beyond the final target position when the polarity inversion position The deviation output is added to the pressure deviation output to suddenly stop the servo motor, thereby preventing the screw from going too far.

According to the second aspect of the present invention, when the back pressure applied to the screw in the back pressure mode is less than the pressure command value, the pressure deviation output is prevented. Occasionally, the screw is prevented from advancing and the injection material is prevented from leaking.

According to the third aspect of the present invention, the position is determined by the pressure deviation.
Since the value obtained by adding the deviation is used as a speed command, pressure control can be performed with high accuracy until the pressure becomes zero even when affected by a mechanical member acting as a load.

According to the fourth aspect of the present invention, since the speed command value is clamped within a predetermined range, even if an erroneous command value is given and erroneous control is performed, the screw moves at high speed and collides with the cylinder. Can be prevented.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention, in which 1 is a screw, 2 is a heating cylinder,
3 is a screw shaft, 5 is a pressure detector that detects pressure on the screw 1, 6 is a servomotor that drives the screw shaft 3 and the screw 1, and 7 is a detector that detects the position and moving speed provided on the servomotor 6. , 8 are pressure commands, 1
0 is a position command, and the above is the same as the conventional example shown in FIG. 9 is a speed limit command, and 100 is a servo drive device corresponding to 100 in FIG.

In the servo drive device 100, 101 is a pressure deviation subtractor, 103 is a position deviation subtractor, 104
Is a position control gain, 105 is a speed deviation subtractor, 106 is
Is a speed control gain, 108 is a current deviation subtractor, 109
Is a current control gain, 110 is a power amplifier, 111 is a current detector, and the above is the same as the conventional example shown in FIG. Reference numeral 112 denotes a pressure control gain in the pressure holding mode (hereinafter referred to as pressure holding control gain), 113 denotes a pressure control gain in the back pressure mode (hereinafter referred to as back pressure control gain), and 114 denotes a pressure holding / gain.
A back pressure switch 115 is a pressure deviation blocker that blocks output when the pressure deviation output from the back pressure control gain 113 is positive.
16 is a positive position deviation blocker that blocks output when the position deviation output from the position control gain 104 is positive, 117 is a negative position deviation blocker that blocks output when the position deviation output from the position control gain 104 is negative, 118 is a holding pressure / back pressure switching device 11
An adder 119 for adding the pressure deviation output and the position deviation output from No. 4 is a speed limiter for clamping the maximum positive or negative value of the deviation output as the speed command from the adder 118 to the value of the speed limit command 9.

Next, the operation of this embodiment will be described.
First, in the injection mode, the holding pressure / back pressure switch 114 is switched to the contacts ad and eh, and a position command 10 indicating the target position of the screw 1 at the time of injection is inputted from the outside, and this is detected. The deviation from the position feedback value from the unit 7 is obtained by the subtractor 103, and this deviation value is multiplied by a predetermined control constant by the position control gain 104, and the contact he of the pressure-holding / back-pressure switch 114 is turned off. Adder 118
Is applied to One input terminal of the adder 118
Since zero output is applied through the contact point da of the back pressure switch 114, only the output from the position control gain 104 is limited to the maximum positive / negative value to the value of the speed limit command 9 via the speed limiter 119. The speed command is applied to the subtractor 105.

The difference between the speed command and the speed feedback value is obtained by the subtracter 105, and this difference is multiplied by a predetermined control constant by a speed control gain 106 to become a current command, which is applied to the subtracter 108. Here, a deviation from a current feedback value indicating a servo motor driving current from the current detector 111 is obtained, and a predetermined control constant is multiplied by a current control gain 109 to the deviation value, amplified by the power amplifier 110, and the servo motor 6 is driven. Driven. In this manner, the screw 1 is moved at a predetermined speed to a predetermined position while rotating, and the molten resin in the heating cylinder 2 is injected into a mold (not shown) at an appropriate injection speed.

Next, in the pressure holding mode, the pressure / back pressure selector 114 is switched to the contacts ab, ef, and the pressure command 8 for instructing the target pressure in the mold and the final pressure of the screw 1 from the outside. A position command 10 indicating a target position is input. It is also assumed that the screw 1 has not reached the final target position. The difference between the input pressure command 8 and the pressure feedback value from the pressure detector 5 is obtained by the subtractor 101, and this difference is multiplied by a predetermined control constant by the holding pressure control gain 112 to switch between the holding pressure and the back pressure. The signal is applied to the adder 118 via the contact ba of the adder 114. On the other hand, the difference between the position command 10 and the position feedback value from the detector 7 is obtained by the subtractor 103, and this difference is multiplied by a predetermined control constant by the position control gain 104 and applied to the positive position deviation preventer 116. You. However, until the screw 1 reaches the final target position, this position deviation output is positive, and is blocked by the positive position deviation blocker 116 and is not applied to the adder 118. Therefore, the holding pressure control gain 11
Only the output from 2 is applied to the subtractor 105 via the speed limiter 119 as a speed command whose maximum positive / negative value is limited to the value of the speed limit command 9. The servo motor 6 is controlled to a speed corresponding to the speed command, and advances toward the final target position until the pressure applied to the screw shaft 3 reaches the command value, and the pressure is controlled to a predetermined value.

Here, it is assumed that even if the screw 1 reaches the final target position, the pressure does not become the command value and the screw 1 tries to keep moving forward. At this time, the position deviation value from the subtractor 103 becomes negative, and is multiplied by a predetermined control constant by the position control gain 104, passes through the positive position deviation prevention unit 116, and contacts f-e of the pressure holding / back pressure switching unit 114. Is applied to the adder 118, where the negative position deviation value is applied to the holding pressure control gain 112.
Is subtracted from the pressure deviation value from, and becomes zero, the speed command becomes zero and the servo motor 6 stops, and the screw 1 stops at the final target position. Therefore, when the holding pressure mode is mistakenly entered without the injection material in the heating cylinder 2,
Even if the screw 1 moves forward, the pressure does not increase and a maximum pressure deviation always occurs. However, the speed limiter 119 limits the speed of the screw 1 to a predetermined value. Since a deviation occurs and the servomotor 6 stops rapidly, the screw 1 does not move forward at a high speed due to an erroneous operation, and it is safe without passing the final target position.

Next, in the back pressure mode, the pressure-holding / back pressure switching device 114 is switched to the contacts ac, eg, and the pressure command 8 for instructing the target back pressure in the heating cylinder 2 from the outside and the pressure command 8 from the outside. A position command 10 for instructing the final reverse target position of the screw 1 is input. It is also assumed that the screw 1 has not retreated to the final target position. The difference between the input pressure command 8 and the pressure feedback value from the pressure detector 5 due to the back pressure generated by the rotation of the screw 1 is obtained by the subtractor 101, and a predetermined control constant is used as the back pressure control gain. Multiplied by 113 and applied to pressure deviation blocker 115. Normally, since the target back pressure is smaller than the back pressure feedback value and the back pressure deviation becomes negative, the back pressure deviation output passes through the pressure deviation prevention device 115 and is added via the contact ca of the pressure holding / back pressure switching device 114. Applied to the vessel 118.
At this time, if the pressure command 8 rises for some reason or if the back pressure applied to the screw 1 suddenly decreases, the output of the back pressure control gain 113 becomes positive. Thus, the screw 1 is prevented from moving forward.

On the other hand, the difference between the position command 10 and the position feedback value from the detector 7 is obtained by the subtractor 103, and a predetermined control constant is added to the difference by a position control gain 10
Multiplied by 4 and applied to the negative position deviation blocker 117. However, this position deviation output becomes negative until the screw 1 reaches the final retreat target position, and is blocked by the negative position deviation blocker 117 and is not applied to the adder 118.
Therefore, only the output from the back pressure control gain 113 is applied to the subtractor 105 via the speed limiter 119 as a speed command whose maximum positive and negative values are limited to the value of the speed limit command 9.
The servo motor 6 is controlled at a speed corresponding to the speed command, and the screw 1 retreats while rotating toward the final target position until the back pressure applied to the screw reaches the command value, and a predetermined amount of the injection material is heated. 2 filled.

Here, when the screw 1 reaches the final target position, its rotation is stopped. At this time, the position deviation output is inverted from a negative value to a positive value, so that the negative position deviation blocker 117 operates, the sum of the position deviation output and the negative back pressure deviation output becomes zero, and a zero speed command is issued. Stop at the final target position.

[0027]

As described above, according to the first aspect of the present invention, the control constant in the pressure-holding mode and the control constant in the back-pressure mode are set to different values, and as it switched when switching back pressure mode, when the holding pressure mode and back pressure mode, until the screw reaches the final target position blocks the differential output of the position feedback value and position command value, the final target position has elapsed The servo motor is reversing stopped by the position deviation output whose polarity has been reversed, so that the pressure can be stabilized without being affected by the mechanical system or injection material.
In addition, the optimal control is performed, and the screw can be stopped with high accuracy , so that the screw can be effectively prevented from going too far.

According to the invention described in claim 2 of the present invention,
The control constants in the dwell mode and the back pressure mode
Different values are used to switch between the dwell mode and back pressure mode.
As it switched during recombination, back pressure mode, since the pressure feedback value was made to prevent the pressure differential output becomes below the pressure command value, affected by the mechanical system and an injection material
Stable and optimal control of pressure
In addition, the servomotor is stopped until the pressure rises, and the screw can be prevented from erroneously advancing in the back pressure mode to prevent leakage of the injection material.

According to the third aspect of the present invention,
The control constants in the dwell mode and the back pressure mode
Different values are used to switch between the dwell mode and back pressure mode.
As switched during recombination, since the value obtained by adding the position deviation of a deviation between the pressure command value and the pressure feedback value to the speed command of the servo motor, affected by the mechanical system and an injection material
Stable and optimal control of pressure
Furthermore, even if the load is affected by a mechanical member, there is an effect that pressure control can be performed with high accuracy until the pressure becomes zero.

According to the invention described in claim 4 of the present invention,
In addition to the effect of the third aspect of the present invention, a speed limiter that clamps the speed command value within a predetermined range is provided, so that even if a wrong command value is given and erroneous control is performed, the screw speed is increased. This has the effect of not moving.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional control method of an electric injection molding machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screw 2 Heating cylinder 3 Screw shaft 5 Pressure detector 6 Servomotor 7 Detector 8 Pressure command 10 Position command 100 Servo drive 104 Position control gain 106 Speed control gain 109 Current control gain 110 Power amplifier 111 Current detector 112 Pressure holding Control gain 113 Back pressure control gain 114 Holding pressure / back pressure switching device 115 Pressure deviation blocker 116 Positive position deviation blocker 117 Negative position deviation blocker 119 Speed limiter

Continuation of front page (56) References JP-A-3-45326 (JP, A) JP-A-1-280522 (JP, A) JP-A-62-264924 (JP, A) JP-A-2-120020 (JP) JP-A-62-97818 (JP, A) JP-A-2-196614 (JP, A)

Claims (4)

(57) [Claims] In an injection mode for injecting a molten resin into a mold, the screw is advanced to a predetermined position at a speed corresponding to a deviation between a position command value and a screw position feedback value detected by a position detector, In the pressure-holding mode in which the pressure in the mold is maintained at a predetermined value, a value obtained by multiplying a deviation between a pressure-holding pressure command value and a pressure feedback value applied to the screw detected by the pressure detector by a predetermined control constant is used. Energize the servo motor for screw drive with electric power,
A value obtained by multiplying a deviation between a predetermined back pressure command value lower than the above holding pressure command value and a pressure feedback value detected by the pressure detector by a predetermined control constant in a back pressure mode for supplying a raw material to the heating cylinder. In the electric injection molding machine control system in which the servo motor is energized to retract the screw to a predetermined position by the electric power according to the control constant for multiplying the pressure deviation in the pressure holding mode and the pressure deviation in the back pressure mode, And the control constant to be multiplied by the pressure are set to different values when switching between the pressure holding mode and the back pressure mode .
In addition, in the pressure holding mode and the back pressure mode,
Set the position command value as the final target position in each mode,
Position command value until the screw reaches this final target position
Output of deviation between the position feedback value and
Servo mode is output by the position deviation output whose polarity has been reversed
A motor-driven injection molding machine control system, characterized in that the motor is stopped in reverse . 2. An injection mode for injecting a molten resin into a mold.
At times, the position command value and the script detected by the position
Above at a speed corresponding to the deviation from the
Advance the screw to the specified position and set the pressure in the mold to the specified value.
Pressure command value and pressure detector
Pressure feed on the screw detected by
According to the value obtained by multiplying the deviation from the back value by a predetermined control constant
Energize the servo motor for screw drive with electric power,
In the back pressure mode where the raw material is supplied to the heating cylinder,
Predetermined back pressure pressure command value lower than pressure pressure command value and pressure detection
Deviation from the pressure feedback value detected by the
The above servo mode is operated with the power corresponding to the value multiplied by the constant control constant.
Control to retract the screw to the specified position
In the control method of the electric injection molding machine controlled by
Control constant that multiplies the pressure deviation during
The control constant multiplied by the force deviation is stored as a different value.
To switch between pressure mode and back pressure mode.
Pressure feedback in back pressure mode.
When the torque value falls below the pressure command value, the pressure deviation output is blocked.
A control method for an electric injection molding machine , characterized in that: 3. An injection mode for injecting a molten resin into a mold.
At times, the position command value and the script detected by the position
Above at a speed corresponding to the deviation from the
Advance the screw to the specified position and set the pressure in the mold to the specified value.
Pressure command value and pressure detector
Pressure feed on the screw detected by
According to the value obtained by multiplying the deviation from the back value by a predetermined control constant
Energize the servo motor for screw drive with electric power,
In the back pressure mode where the raw material is supplied to the heating cylinder,
Predetermined back pressure pressure command value lower than pressure pressure command value and pressure detection
Deviation from the pressure feedback value detected by the
The above servo mode is operated with the power corresponding to the value multiplied by the constant control constant.
Control to retract the screw to the specified position
In the control method of the electric injection molding machine controlled by
Control constant that multiplies the pressure deviation during
The control constant multiplied by the force deviation is stored as a different value.
To switch between pressure mode and back pressure mode.
And the deviation between the pressure command value and the pressure feedback value.
The value obtained by adding the position deviation to the difference is used as the servo motor speed command.
A control method for an electric injection molding machine. 4. A speed command value is clamped within a predetermined range.
4. The control system according to claim 3, further comprising a speed limiter .