JP3091262B2 - Injection control method and apparatus in electric injection molding machine - 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 control method and apparatus in an electric injection molding machine.

[0002]

2. Description of the Related Art In an injection control of an injection molding machine, a screw is driven with an injection speed priority at an initial stage of injection, and the screw is driven at a set injection pressure from a stage where the screw reaches a specific switching position and resin filling is completed. The resin is pressed to maintain a certain resin pressure to maintain the pressure.

[0003] Injection control in an electric injection molding machine equipped with a servomotor is performed in a similar manner. That is, as disclosed in Japanese Unexamined Patent Publication No. 62-97813,
After the start of injection, injection control is first performed, and when the pressure-holding step is started, feedback control is performed so that the detected resin pressure from the sensor for detecting the resin pressure becomes the set injection pressure (set pressure-holding). I do.

[0004]

However, if such pressure control is performed, it becomes impossible to control the screw position and speed during this time. Therefore, when the resin pressure in the cylinder does not reach the set injection pressure due to insufficient filling of the resin or backflow, even if the screw reaches the most advanced position, the screw is driven strongly. As a result of the force acting, there was a risk of causing various damages such as a collision of the screw with the tip of the cylinder.

An object of the present invention is to provide an injection control method and apparatus in an electric injection molding machine which can perform predetermined pressure control and can prevent screw collision beforehand.

[0006]

An injection control method and apparatus according to the first and fourth aspects of the electric injection molding machine according to the present invention comprise a pressure sensor for detecting an injection pressure, a set injection pressure and the pressure sensor. a speed command means for outputting a speed command based on the deviation between the detected current injection pressure, the servo control hand
Comparing means for comparing the output of the position loop of the stage with the output from the speed command means; and a speed command input to the speed loop of the servo control means based on a signal from the comparing means. Switching means for switching to an output from the speed command means, wherein the switching means inputs the smaller output of the position loop output and the speed command means output to the speed loop. Achieved.

In the second and fifth aspects, a pressure sensor for detecting an injection pressure and a torque for outputting a torque command based on a deviation between a set injection pressure and a current injection pressure detected by the pressure sensor. Command means and the servo control means
Comparing means for comparing the output of the speed loop of the stage with the output from the torque command means; and outputting the torque command input to the injection servomotor based on the signal from the comparing means to the speed loop output or the torque. Switching means for switching to the output from the command means, wherein the switching means is configured to input the smaller one of the output of the speed loop and the output of the torque command means to the injection servomotor. Achieved.

[0008]

According to the first and fourth aspects of the present invention, a command for moving to the screw target position is output to the injection servomotor to start injection, and output based on the deviation between the set injection pressure and the current injection pressure. The magnitude relation between the velocity command output from the position loop and the velocity command output from the position loop is sequentially compared, and the velocity loop control is performed based on the smaller velocity command to drive the injection servomotor.

At the stage immediately after the start of injection, the resin is not completely filled, so that the deviation between the set injection pressure and the current injection pressure is large, and the value of the speed command output based on the deviation between the set injection pressure and the current injection pressure is large. Relatively large. On the other hand, as a result of the resin pressure obstructing the driving of the injection servomotor acting on the screw and the injection servomotor moving following the movement command, the value of the speed command output from the position loop is relatively small. Therefore, at the stage immediately after the start of injection, the injection servomotor is controlled with speed priority by the speed command output from the position loop.

[0010] During this time, when the filling of the resin is completed and the resin pressure increases, the deviation between the set injection pressure and the current injection pressure gradually decreases, and is output based on the deviation between the set injection pressure and the current injection pressure. The value of the speed command becomes relatively small.
On the other hand, since the resin pressure that hinders the drive of the injection servomotor acts on the screw and the deviation of the position loop increases,
The value of the speed command output from the position loop becomes relatively large. Then, when the value of the speed command output from the position loop exceeds the value of the speed command output based on the deviation between the set injection pressure and the current injection pressure, and the filling of the resin is confirmed, the injection servomotor is turned on. Pressure priority control with the set injection pressure as the target value is performed by a speed command output based on the deviation between the set injection pressure and the current injection pressure.

When the resin is not sufficiently filled or a backflow occurs, the reaction force of the resin pressure does not act on the screw, and the deviation between the set injection pressure and the current injection pressure does not become small. The speed command based on the above maintains a large value. However, as a result of the injection servomotor moving following the movement command, the value of the speed command output from the position loop does not increase, so that the drive of the injection servomotor is directly controlled by the speed command output from the position loop. You.
As a result, since the speed command output from the position loop is not output beyond the screw target position, the overtravel of the screw is prevented beforehand, and the collision is prevented.

In the second and fifth aspects, the magnitude relationship between a torque command output based on a deviation between a set injection pressure and a current injection pressure and a torque command output from a speed loop are sequentially compared to determine a value. The same applies to the case where the injection servomotor is driven based on the smaller torque command of the above, and since the filling of the resin is not completed immediately after the start of injection, the deviation between the set injection pressure and the current injection pressure is large, While the value of the torque command output based on the deviation between the set injection pressure and the current injection pressure becomes relatively large, the resin pressure that prevents the drive of the injection servomotor does not act, and the injection servomotor responds to the movement command. Since it follows, the value of the torque command output from the speed loop is relatively small. Therefore, at the stage immediately after the start of injection, the injection servomotor is controlled with speed priority by the torque command output from the speed loop.

When the filling of the resin is completed during this time, the difference between the set injection pressure and the current injection pressure gradually decreases, and the value of the torque command output based on the difference between the set injection pressure and the current injection pressure becomes relative. On the other hand, the resin pressure that hinders the driving of the injection servomotor acts to increase the deviation of the speed loop, and the value of the torque command output from the speed loop becomes relatively large. When the value of the torque command output from the speed loop exceeds the value of the torque command output based on the deviation between the set injection pressure and the current injection pressure, and the resin is confirmed to be filled, the injection servomotor sets the injection. Pressure priority control is performed with the set injection pressure as a target value according to a torque command output based on the deviation between the pressure and the current injection pressure.

If the resin is not sufficiently filled or a backflow occurs, the deviation between the set injection pressure and the current injection pressure does not decrease, and the value of the torque command output from the speed loop does not increase. The drive of the injection servomotor is directly controlled by the torque command output from the speed loop, but since the torque command output from the speed loop is not output beyond the screw target position,
Overtravel of the screw is prevented beforehand and collision is prevented.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a main part of an electric injection molding machine according to an embodiment to which the method of the present invention is applied. Only an injection shaft of the injection molding machine is shown, and a mold clamping shaft, a screw rotating shaft, and the like are shown. Not.

1 is a screw, 2 is an injection servomotor for injecting resin by moving the screw in the axial direction, 3 is a pulse coder for detecting the position and speed of the injection servomotor 2, and 4 is a counteracting force acting on the screw. A pressure sensor 5 for detecting a force as a resin pressure is a cylinder.

Reference numeral 10 denotes a control device for controlling the injection molding machine. The control device 10 includes an NC CPU 11 and a PMC
A ROM 17 storing a control program and a RAM 18 used for temporary storage of data are connected to the NC CPU 11 by a bus 25.
The MC CPU 12 has a ROM 19 storing a sequence program and an RA used for temporarily storing data.
M20 is connected by bus 25. 14 is BAC,
Shared RAM 15 for storing NC programs and various setting values
The NC CPU 11 and the PMC CPU 12 are connected by a bus 25 to control a bus used by the BAC 14. A CRT / MDI 22 is connected to the BAC 14 via an operator panel controller 21.

Reference numeral 13 denotes a servo CPU which constitutes a part of a digital servo circuit for controlling the output torque, speed and position of the servo motor of each axis of the injection molding machine. The CPU 13 is used by the bus 25 for temporarily storing data. A RAM 23, an input / output circuit 24, and a servo common RAM 16 for storing a control program for servo control, setting values, and the like are connected. The NC CPU 11 is bus-connected to the servo common RAM 16.

A power amplifier 6 is connected to the input / output circuit 24 via a driver 7 having a D / A converter. The output of the power amplifier 6 drives the injection servomotor 2. The input / output circuit 24 has a power amplifier 6
, Ie, the drive current of the injection servomotor 2 is A /
The drive current value data converted by the D converter 9, the pressure data obtained by converting the output of the pressure sensor 4 into a digital signal by the A / D converter 8, and the pulse output from the pulse coder 3 are input.

In the above configuration, when the injection molding machine is operated, the PMC CPU 12 performs sequence control by the sequence program in the ROM 19,
The C CPU 11 controls each operation of the injection molding machine according to the NC program in the shared RAM 15 and outputs a movement command to the servo motor of each axis. This movement command is temporarily stored in the servo shared RAM 16 and In response to the movement command for each axis, the servo CPU 13 executes the processing of the position and speed loops in the processing for each predetermined cycle to perform position control, speed control, and torque control of the servo motor for each axis.

FIG. 2 shows the servo CPU 1 during injection control.
3 is a flowchart of the first embodiment showing an outline of a process executed for each position / speed loop processing cycle. Hereinafter, FIG.
The processing operation of the first embodiment of the present invention corresponding to claims 1 and 3 will be described with reference to FIG.

The servo CPU 13 further divides the movement command to the screw most forward position output from the NC CPU 11 for each distribution cycle and outputs the movement command to the screw most forward position, and the movement command θr divided for each position / speed loop processing cycle and the feedback from the pulse coder 3. A position loop process is performed by a pulse in the same manner as in the related art to calculate a speed command Vc (step S1). Further, a deviation between the set injection pressure Ps stored in the servo shared RAM 16 and the current injection pressure Pf detected by the pressure sensor 4 is obtained, and the deviation is multiplied by a proportional gain Kx to calculate a speed command Pc based on the pressure deviation. (Step S2).

The servo CPU 13 having calculated the speed command Vc by the position loop processing and the speed command Pc based on the pressure deviation compares the magnitudes of the two (step S3), and determines the value of the speed command Pc based on the pressure deviation as the speed of the position loop. If the value is relatively smaller than the value of the command Vc, the speed command Pc based on the pressure deviation performs the same speed loop processing as the conventional one (step S4), while the value of the speed command Vc by the position loop processing becomes the pressure deviation. If the value is relatively smaller than the value of the base speed command Pc, the speed loop processing is executed in the same manner as in the related art with the speed command Vc by the position loop processing (step S5). That is, PI (proportional or integral) control is performed from the speed command Vc or Pc and the detected actual speed of the servomotor obtained from the feedback pulse from the pulse coder 3 in the same manner as in the related art to obtain the torque command value Tr. Then, the torque command value Tr is transferred to the current loop (step S6), and the processing of the position / speed loop processing cycle ends. Also,
In the current loop, a current loop process similar to the conventional one is performed based on the torque command value Tr and the drive current value of the injection servomotor 2 input via the A / D converter 9, and the result is supplied to the power amplifier 6 via the driver 7. Output and drive-controls the injection servomotor 2.

At the stage immediately after the start of injection, since the filling of the resin into the mold has not been completed, the deviation between the set injection pressure Ps and the current injection pressure Pf is large, and the deviation between the set injection pressure Ps and the current injection pressure Pf is large. The value of the speed command Pc calculated based on this becomes relatively large. On the other hand, since the injection servomotor 2 follows the movement command from the NC CPU 11 without applying the resin pressure that hinders the driving of the injection servomotor 2 to the screw 1, the position deviation is small and the speed command Vc by the position loop processing is small. The values are relatively small. Therefore, at the stage immediately after the start of injection, the injection servomotor 2 is controlled by the speed command Vc in the position loop process with speed priority.

When the filling of the resin into the mold is completed while the screw 1 moves forward, the reaction force of the resin acts on the screw 1 so that the deviation between the set injection pressure Ps and the current injection pressure Pf gradually decreases. , The value of the speed command Pc based on the pressure deviation becomes relatively small. In addition, as a result of preventing the screw 1 from moving forward, the position deviation increases, and the value of the speed command Vc by the position loop process becomes relatively large. When the speed command Vc by the position loop processing exceeds the value of the speed command Pc based on the pressure deviation, the injection servomotor 2 outputs the speed command Pc based on the deviation between the set injection pressure Ps and the current injection pressure Pf. Thus, pressure priority control with the set injection pressure Ps as the target value is performed. If there is no problem such as resin backflow, leakage, or poor filling, the pressure is maintained for a predetermined time with the set injection pressure Ps while a certain amount of deviation remains in the position loop, and the injection control is completed. P
s, a good pressure holding process is performed.

On the other hand, if the resin is insufficiently filled or a backflow occurs between the screw 1 and the cylinder 5, the resin pressure in the cylinder 5 does not increase, so that the set injection pressure Ps and the current injection pressure Pf Does not become small, and the speed command Pc based on the pressure deviation shows a large value.
On the other hand, since the resin pressure that hinders the driving of the injection servomotor 2 does not act on the screw 1, the injection servomotor 2
Follows the movement command from the NC CPU 11, the position deviation does not increase greatly, and the speed command Vc by the position loop processing
Does not increase. Therefore, the injection servomotor 2
Is driven to the final stage by the speed command Vc output from the position loop. Since the output of the speed command Vc by the position loop processing is automatically stopped when the screw 1 has moved to the most forward position and the positional deviation has disappeared, overtravel of the screw 1 is prevented beforehand, and the tip of the cylinder 5 is prevented. Collision with is prevented.

FIG. 3 is a flowchart of a second embodiment schematically showing processing executed in each position / speed loop processing cycle in the injection control of the servo CPU 13. The configuration of the injection molding machine is the same as that of the first embodiment. Thereafter, as in the first embodiment, the servo CPU 13 performs a position loop process to calculate a speed command Vc (step T1),
Further, based on the position loop speed command Vc and the current speed of the injection servomotor 2 obtained from the feedback pulse Vf from the pulse coder 3, the same speed loop processing as that of the related art is executed to obtain the torque command value Tr. (Step T2). Further, a deviation between the set injection pressure Ts stored in the servo shared RAM 16 and the current injection pressure Tf detected by the pressure sensor 4 is obtained, and the deviation is multiplied by a proportional gain Ky to calculate a torque command Tc based on the pressure deviation. (Step T3).

Servo CPU 1 which calculates torque command Tr based on torque command Tr and pressure deviation by speed loop processing
3 compares the magnitude relation between the two (step T4). If the value of the torque command Tc based on the pressure deviation is relatively smaller than the value of the torque command Tr from the speed loop, the torque command Tc based on the pressure deviation is determined. The process is passed to the current loop (step T5), and the processing of the position / velocity loop processing cycle ends. On the other hand, if the value of the torque command Tr by the speed loop processing is relatively smaller than the value of the torque command Tc based on the pressure deviation, the torque command Tr from the speed loop is transferred to the current loop (step T6), and the position -End the processing of the speed loop processing cycle. In the current loop, a current loop process is performed by the torque command value Tc and the drive current value of the injection servomotor 2 input via the A / D converter 9 in the same manner as in the prior art, and the current is processed by the power amplifier 6 via the driver 7. Output and drive-controls the injection servomotor 2.

Since the value of the torque command Tr from the speed loop depends on the position deviation and the speed deviation, the phenomenon that occurs during the injection control is the same as in the first embodiment.

That is, in the stage immediately after the start of injection, the deviation between the set injection pressure Ts and the current injection pressure Tf is large, and the value of the torque command Tc calculated based on the pressure deviation becomes relatively large. Since the resin pressure that hinders the driving of the motor 2 does not act, the injection servomotor 2 is driven by the NC CP.
Following the movement command from U11, the value of the torque command Tr from the speed loop becomes relatively small. Therefore, at the stage immediately after the start of the injection, the injection servomotor 2 is preferentially controlled by the torque command Tr of the speed loop.

When the filling of the resin into the mold is completed while the screw 1 is moving forward, the reaction force of the resin acts on the screw 1 so that the deviation between the set injection pressure Ts and the current injection pressure Tf gradually decreases. And the torque command Tc based on the pressure deviation
Is relatively small, and as a result, the forward movement of the screw 1 is hindered. As a result, the speed decreases, the position deviation and the speed deviation increase, and the value of the torque command Tr from the speed loop relatively increases. When the torque command Tr of the speed loop exceeds the value of the torque command Tc based on the pressure deviation,
The injection servomotor 2 performs priority control using the set injection pressure Ts as a target value by a torque command Tc output based on the deviation between the set injection pressure Ts and the current injection pressure Tf. If there is no problem such as resin backflow, leakage, or poor filling, injection pressure is controlled by the set injection pressure Ts for a predetermined time while a certain amount of position deviation and speed deviation remain in the position loop and speed loop. Is completed, and a good pressure holding process based on the set injection pressure Ts is performed.

On the other hand, if the resin is insufficiently filled or backflow occurs, the resin pressure in the cylinder 5 does not increase, so that the deviation between the set injection pressure Ts and the current injection pressure Tf does not become small. Torque command T based on the resulting pressure deviation
c increases. On the other hand, as a result of the injection servomotor 2 following the movement command from the NC CPU 11, the position deviation,
The speed deviation does not increase and the torque command Tr from the speed loop
Does not increase. Therefore, the injection servomotor 2
Is controlled to the final stage by the torque command Tr output from the speed loop. Then, the output of the torque command Tr is automatically stopped when the screw 1 has moved to the most advanced position and the positional deviation has disappeared, so that the overtravel of the screw 1 is prevented beforehand, and the output from the tip of the cylinder 5 is prevented. Collisions are prevented.

Next, the case where the injection servomotor 2 is driven by applying a conventional analog servo circuit instead of the digital servo circuit including the servo CPU 13, the RAM 23, the servo shared RAM 16, and the like. An example will be described.

FIG. 4 is a block diagram of a third embodiment schematically showing the configuration of a servo circuit relating to the servomotor 2 for injection. The configuration itself of the main part relating to the injection molding machine and the control device 10 is the same as that of the above-described first and second embodiments, and the components 13 and 1 constituting the digital servo circuit in FIG.
6, 23, 24, etc. are merely replaced with conventionally known analog servo circuits.

Reference numeral 26 denotes a block constituting a position loop, which comprises an error register including a reversible counter, a D / A converter, an amplifier, etc., accumulates the distribution pulse θr from the NC CPU 11 and outputs a pulse from the pulse coder 3. The position-dependent feedback pulse θf is subtracted, and this value, that is, the value of the error amount with respect to the position command, is successively calculated as D / A
Converted and output as speed command Vc. Reference numeral 27 denotes a block constituting a speed loop, which is composed of an error amplifier or the like. The speed deviation between the input speed command and the current speed Vf obtained by F / V converting the feedback pulse θf from the pulse coder 3 is represented by PI ( (Proportional, integral) control to amplify and output a torque command Tr. Numeral 28 denotes a block constituting a current loop, which comprises an error amplifier and the like. The deviation of the input torque command Tr and the drive current from the power amplifier 29 flowing through the injection servomotor 2 is output to the power amplifier 29 to output the injection servo. The drive of the motor 2 is controlled.

Reference numeral 4 denotes a pressure sensor similar to those of the first and second embodiments, and detects a reaction force acting on the screw 1 constituting a part of the injection mechanism as a resin pressure. These configurations are the same as those of the conventional electric injection molding machine. However, in the present embodiment, the set injection pressure Ps set by the NC CPU 11 and the current injection pressure Pf detected by the pressure sensor 4 are further reduced. Of the speed command Pc
A differential amplifier 30 is provided as a speed command means for outputting as a speed command. Further, between the position loop 26 and the speed loop 27, an input to the speed loop 27 is input to the speed command Pc from the differential amplifier 30 and the position loop. A changeover switch 32 that switches between the speed command Vc and the speed command Vc is provided. The changeover switch 32 is switched by the output of the comparator 31 which compares the magnitude relationship between the speed command Pc from the differential amplifier 30 and the speed command Vc from the position loop 26, and when the speed command Pc is smaller than the speed command Vc. Has a differential amplifier 3
On the other hand, when the speed command Vc is smaller than the speed command Pc, it is connected to the position loop 26 side.

When the servo circuit of the third embodiment is applied,
The phenomenon that occurs during the injection control is the same as that of the first embodiment.

That is, at the stage immediately after the start of injection, since the filling of the resin into the mold has not been completed, the deviation between the set injection pressure Ps and the current injection pressure Pf is large, and the difference between the set injection pressure Ps and the current injection pressure Pf is large. While the value of the speed command Pc output from the differential amplifier 30 based on the deviation becomes relatively large,
The screw 1 does not receive any resin pressure that hinders the driving of the injection servomotor 2 and the injection servomotor 2 is driven by the NC CPU.
11, the value of the speed command Vc from the position loop 26 becomes relatively small. At the stage immediately after the start of injection, the changeover switch 32 is connected to the position loop 26 side, and the injection servo motor 2 Is controlled by the speed command Vc from the position loop 26 with speed priority.

When the filling of the resin into the mold is completed while the screw 1 moves forward, the reaction force of the resin acts on the screw 1 so that the deviation between the set injection pressure Ps and the current injection pressure Pf gradually decreases. The value of the speed command Pc output from the differential amplifier 30 based on the pressure deviation becomes relatively small, while the forward movement of the screw 1 is hindered, the position deviation increases, and the speed command Vc of the position loop 26 is reduced. The value becomes relatively large. When the speed command Vc from the position loop 26 exceeds the value of the speed command Pc from the differential amplifier 30, the changeover switch 32 is connected to the differential amplifier 30 side, and the injection servomotor 2 is output from the differential amplifier 30. Speed command P
According to c, pressure feedback control with the set injection pressure Ps as the target value is performed, and pressure priority control is performed. If there is no problem such as resin backflow, leakage, or poor filling, the pressure is maintained for a predetermined time with the set injection pressure Ps while a certain amount of deviation remains in the position loop 26, and the injection control is completed. Good pressure holding processing by the pressure Ps is performed.

On the other hand, if the filling of the resin is insufficient or the backflow occurs, the resin pressure does not increase. Therefore, the difference between the set injection pressure Ps and the current injection pressure Pf, that is, the differential amplifier 3
The value of the speed command Pc from 0 is maintained at a large value. Further, since the injection servomotor 2 follows the movement command from the NC CPU 11, the speed command Vc from the position loop 26 does not increase. Therefore, the changeover switch 32 remains connected to the position loop 26, and the injection servomotor 2 outputs the speed command Vc output from the position loop 26.
As a result, the drive is controlled until the final stage. The speed command Vc from the position loop 26 is automatically stopped because the position deviation becomes 0 when the screw 1 moves to the most forward position, so that the overtravel of the screw 1 is prevented beforehand, and Collisions are prevented.

FIG. 5 is a block diagram of a fourth embodiment of the present invention using an analog servo circuit. The fourth embodiment has almost the same configuration as the third embodiment, and the difference is that
While the changeover switch is provided between the position loop and the speed loop in the third embodiment, the changeover switch is provided between the speed loop and the current loop in the fourth embodiment, and the torque input to the current loop is provided. The point is that the command is switched from the speed loop to the output of the differential amplifier. That is, the changeover switch 34
Is the torque command Tc from the differential amplifier 33 and the speed loop 2
7 is switched by a comparator 35 which compares the magnitude relationship with the torque command Tr from the controller 7. If the torque command Tc is smaller than the torque command Tr, the comparator 35 is connected to the differential amplifier 33, while the torque command Tr is If it is smaller than Tc, it is connected to the speed loop 27 side.

At the stage immediately after the start of injection, the set injection pressure Ts
And the current injection pressure Tf is large, and the value of the torque command Tc output from the differential amplifier 33 is relatively large based on the pressure deviation. On the other hand, the injection servomotor 2 is N
Since it follows the movement command from the C CPU 11, the value of the torque command Tr from the speed loop 27 becomes relatively small, and at the stage immediately after the start of injection, the injection servomotor 2 is controlled by the torque command Tr from the speed loop 27. Priority control is performed.

When the filling of the resin into the mold is completed while the screw 1 advances, the reaction force of the resin acts on the screw 1 and the deviation between the set injection pressure Ts and the current injection pressure Tf gradually decreases. The differential amplifier 3 based on the pressure deviation.
3, the value of the torque command Tc output from the speed loop 27 increases, and the value of the torque command Tr from the speed loop 27 increases. growing. When the torque command Tr from the speed loop 27 exceeds the value of the torque command Tc from the differential amplifier 33, the injection servomotor 2
Priority control with the target injection pressure Ts as the target value is performed by the torque command Tc output based on the deviation between the target injection pressure Ts and the current injection pressure Tf. If there is no problem such as resin backflow, leakage, or poor filling, the holding pressure by the set injection pressure Ts is performed for a predetermined time while the position loop 26 and the speed loop 27 have some positional deviation and speed deviation. The injection control is completed, and a good pressure holding process based on the set injection pressure Ts is performed.

On the other hand, if the resin is insufficiently filled or a backflow occurs, the resin pressure in the cylinder 5 does not increase, so the differential amplifier 33 is set based on the deviation between the set injection pressure Ts and the current injection pressure Tf. The torque command Tc output from the motor is not reduced, and the injection servomotor 2
Since it follows the movement command from the PU 11, the speed loop 2
Since the value of the torque command Tr from No. 7 does not increase, the changeover switch 34 is connected to the speed loop side. Therefore,
The drive of the injection servomotor 2 is controlled to the final stage by the torque command Tr output from the speed loop 27. Since the output of the torque command Tr is automatically stopped when the screw 1 has moved to the most advanced position and the positional deviation has disappeared, overtravel of the screw 1 is prevented beforehand, and collision with the tip of the cylinder 5 is prevented. Will be blocked.

[0045]

According to the present invention, a speed command or a torque command output based on a deviation between a set injection pressure and a current injection pressure in an injection control stage, and a speed command from a position loop for controlling an injection servomotor. And the torque command from the speed loop are successively compared, and the injection servomotor is driven based on the smaller command value, so priority control of the speed at the injection start stage and injection to press the filling resin The pressure control in the second half can be performed smoothly as before, and if the resin pressure in the second half of injection does not reach the set value due to insufficient resin filling, Sudden speed by speed control based on speed command from loop
A smooth operation without change is obtained. Also, for position control
Since the screw stops automatically at the commanded target position, overtravel of the screw and a collision accident due to poor filling or the like are prevented beforehand.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of an electric injection molding machine according to one embodiment in which a method of the present invention is applied to a digital servo.

FIG. 2 is a flowchart of a first embodiment showing an outline of processing executed by a servo CPU at each position / speed loop processing cycle during injection control in the electric injection molding machine of the embodiment.

FIG. 3 is a flowchart of a second embodiment showing an outline of processing executed by the servo CPU at each position / speed loop processing cycle during injection control in the electric injection molding machine of the embodiment.

FIG. 4 is a functional block diagram of a third embodiment showing an analog servo circuit of an electric injection molding machine to which the method of the present invention is applied.

FIG. 5 is a functional block diagram of a fourth embodiment showing an analog servo circuit of an electric injection molding machine to which the method of the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screw 2 Injection servomotor 3 Pulse coder 4 Pressure sensor 10 Control device 13 Servo CPU 30 Differential amplifier as speed command means 31 Comparator 32 Changeover switch 33 Differential amplifier as torque command means 34 Changeover switch 35 Comparator

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tetsuaki Neko 3580 Kobaba, Oshino-mura, Oshino-mura, Minamitsuru-gun, Yamanashi FANUC CORPORATION Product Development Laboratory (56) References JP-A-3-43227 (JP, A JP-A-61-195819 (JP, A) JP-A-62-198426 (JP, A) JP-A-3-243321 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/76-45/84 B29C 45/48-45/50

Claims (5)

(57) [Claims] 1. A servo motor for injection, a detector for detecting the position and speed of the screw, and a pressure sensor for detecting the pressure, position loop, performs control of the velocity loop servo the injection Electric injection molding machine that controls the motor
The Oite, move to the target position to the servo motor for the injection
Output a movement command, and the position
Finds the speed command by loop control and sets the
Calculated based on the deviation from the injection pressure detected by the pressure sensor.
Speed command and the speed finger obtained by the above position loop control.
Command, and performs speed loop control based on the smaller speed command to drive the injection servomotor and set the target position.
An injection control method in an electric injection molding machine, characterized in that control is performed so as not to exceed the limit. [2 claim] a servomotor for injection, a detector for detecting the position and speed of the screw, and a pressure sensor for detecting the pressure, position loop and performs control of the velocity loop servo the injection Electric injection molding machine that controls the motor
The Oite, move to the target position to the servo motor for the injection
Output a movement command, and the position
Calculate the torque command by the position loop control and the speed loop control.
Output based on the deviation between the set injection pressure and the current injection pressure.
Torque command and the above position loop control and speed loop
Successive ratio of magnitude relationship with torque command obtained by control
Compare, and injection control method in an electric injection molding machine, characterized in that by driving the injection servomotor is controlled so as not to exceed the target position based on the torque command the smaller. 3. The target position is a screw forward position.
The electric injection molding machine according to claim 1 or 2,
Injection control method . 4. An injection control device for an electric injection molding machine, comprising: an injection servomotor , a detector for detecting the position and speed of a screw, and servo control means having a position loop and a speed loop. a pressure sensor for detecting a speed command means for outputting a speed command based on the deviation between the set injection pressure and the current injection pressure, the servo
Comparing means for comparing the output of the position loop of the control means with the output of the speed command means; and outputting the speed command input to the speed loop of the servo control means based on the signal from the comparing means to the position loop output. Switching means for switching between an output from the speed command means and an output from the speed command means, wherein the switching means inputs the smaller one of the output of the position loop and the output of the speed command means to the speed loop. Control device in the machine. 5. An injection control apparatus for an electric injection molding machine, comprising: an injection servomotor , a detector for detecting the position and speed of a screw, and servo control means having a position loop and a speed loop. a pressure sensor for detecting a torque command means for outputting a torque command based on a deviation between the current injection pressure detected by the set injection pressure and the pressure sensor, the output and the speed command for the speed loop of the servo control means Comparing means for comparing the output with the means, and switching means for switching a torque command input to the injection servomotor to the speed loop output or the output from the torque command means based on a signal from the comparing means. Wherein the switching means inputs the smaller one of the output of the speed loop and the output of the torque command means to the injection servomotor. An injection control device in an electric injection molding machine.