JPH04369520A - Method and device for controlling injection in electrical injection molding machine - Google Patents

Abstract

PURPOSE:To prevent the collision of a screw at the time of injection. CONSTITUTION:The magnitude relationship of a speed command Pc outputted from a diffential amplifier 30 on the basis of the deviation of set injection pressure Ps and current injection pressure Pf and a speed command Vc from a positional loop 26 is compared successively by a comparator 31. The speed command having a small value in the speed command Pc and the speed command Vc is input to a speed loop 27 by operating a changeover switch 32 by an output from the comparator 31, and a servomotor 2 for injection is driven. When a resin is filled insufficiently, resin pressure in the latter half of injection reaches the set value Ps, the speed command Vc<the speed command Pc holds. Since the speed command Vc from the positional loop 26 reaches zero at a step when a screw 1 reaches a most forward position and a positional deviation reaches zero, the screw 1 is stopped automatically at the most forward position, thus preventing the collision of the screw against a cylinder.

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 for an electric injection molding machine.

0002

[Prior Art] In injection control in an injection molding machine, the screw is driven with priority given to the injection speed at the initial stage of injection, and from the stage when the screw reaches a specific switching position and resin filling is completed, the screw is driven at the set injection pressure. Hold pressure by pressing to maintain constant resin pressure.

Injection control in an electric injection molding machine equipped with a servo motor is performed in a similar manner. That is, as disclosed in Japanese Patent Application Laid-Open No. 62-97813,
After injection starts, injection control is performed first, and when the pressure holding process begins, feedback control is performed so that the resin pressure detected by the sensor that detects resin pressure becomes the set injection pressure (set holding pressure). I do.

0004

However, when such pressure control is performed, it becomes impossible to control the screw position and speed during this period. Therefore, if the resin pressure in the cylinder does not reach the set injection pressure due to insufficient resin filling or backflow, the screw will not be driven with a strong force even after the screw reaches its fully advanced position. As a result, there was a risk that the screw would collide with the tip of the cylinder, causing various damage.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an injection control method and apparatus for an electric injection molding machine that can perform predetermined pressure control and prevent screw collisions.

[0006]

[Means for Solving the Problems] The injection control method and device of the first and third aspects of the electric injection molding machine of the present invention include a pressure sensor for detecting injection pressure, a set injection pressure, and the pressure sensor. a speed command means for outputting a speed command based on the detected deviation from the current injection pressure; a comparison means for comparing the output of the position loop of the servo circuit with the output from the speed command means; switching means for switching the speed command input to the speed loop of the servo circuit based on a signal between the position loop output and the output from the speed command means, the switching means switching between the output of the position loop and the speed command means; The above objective has been achieved by a configuration in which the smaller output of the outputs is inputted to the speed loop.

Further, in the second and fourth inventions, a pressure sensor that detects the injection pressure, and a torque sensor that outputs a torque command based on the deviation between the set injection pressure and the current injection pressure detected by the pressure sensor. a command means, a comparison means for comparing the output of the speed loop of the servo circuit with the output from the torque command means, and a torque command input to the injection servo motor based on the signal from the comparison means. A switching means is provided for switching between the speed loop output and the output from the torque command means, and the switching means inputs the smaller of the output of the speed loop and the output of the torque command means to the injection servo motor. The above objectives were achieved with this configuration.

[0008]

[Operation] In the first and third inventions, a command to move the screw to the most advanced position is output to the injection servo motor to start injection, and an output is made based on the deviation between the set injection pressure and the current injection pressure. The magnitude relationship between the speed command output from the position loop and the speed command output from the position loop is successively compared, and speed loop control is performed based on the speed command with the smaller value to drive the injection servo motor.

Immediately after injection starts, resin filling is not completed, so the deviation between the set injection pressure and the current injection pressure is large, and the value of the speed command that is output based on the deviation between the set injection pressure and the current injection pressure is becomes relatively large. On the other hand, the resin pressure that prevents the driving of the injection servo motor does not act on the screw, and the injection servo motor moves following the movement command, so that the value of the speed command output from the position loop is relatively small. Therefore, immediately after the start of injection, the injection servo motor is controlled with speed priority based on the speed command output from the position loop.

During this time, when the resin filling is completed and the resin pressure increases, the deviation between the set injection pressure and the current injection pressure gradually decreases, and the output is based on the deviation between the set injection pressure and the current injection pressure. The speed command value becomes relatively small. On the other hand, resin pressure acts on the screw and prevents the injection servo motor from driving, increasing the deviation of the position loop.
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 resin filling is confirmed, the injection servo motor Pressure priority control is performed using the set injection pressure as a target value based on a speed command output based on the deviation between the set injection pressure and the current injection pressure.

[0011] Furthermore, if the resin is insufficiently filled or a backflow occurs, the reaction force of the resin pressure will not act on the screw, and the deviation between the set injection pressure and the current injection pressure will not become small. The speed command based on this maintains a large value. However, as the injection servo motor follows the movement command and moves, the value of the speed command output from the position loop does not increase, so the injection servo motor is directly driven and controlled by the speed command output from the position loop. Ru. As a result, the speed command output from the position loop is never output beyond the most advanced position of the screw, so overtravel of the screw is prevented and a collision is prevented.

In the second and fourth inventions, the magnitude relationship between the torque command output based on the deviation between the set injection pressure and the current injection pressure and the torque command output from the speed loop is successively compared and the value is determined. The case where the injection servo motor is driven based on the smaller torque command is similar to the above, and since resin filling is not completed immediately after injection starts, 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 injection servo motor from acting does not act and the injection servo motor responds to the movement command. Because of this, the value of the torque command output from the speed loop is relatively small. Therefore, immediately after the start of injection, the injection servo motor is controlled with priority given to speed by the torque command output from the speed loop.

During this time, when the resin filling is completed, the deviation between the set injection pressure and the current injection pressure gradually decreases, and the value of the torque command output based on the deviation between the set injection pressure and the current injection pressure becomes relative. However, the deviation of the speed loop increases due to the resin pressure that prevents the injection servo motor from driving, 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 resin filling is confirmed, the injection servo motor starts the set injection. Pressure priority control is performed using a set injection pressure as a target value using a torque command output based on the deviation between the pressure and the current injection pressure.

[0014] Furthermore, if resin filling is insufficient or backflow occurs, the deviation between the set injection pressure and the current injection pressure will not become smaller, and the value of the torque command output from the speed loop will not increase. The injection servo motor is directly driven and controlled by the torque command output from the speed loop, but since the torque command output from the speed loop is never output beyond the screw's most forward position, screw overtravel is prevented. is prevented and collisions are prevented.

[0015]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the main parts of an electric injection molding machine according to an embodiment of the present invention, in which only the injection shaft of the injection molding machine is shown, and the mold clamping shaft, screw rotation shaft, etc. are not shown. Not yet.

1 is a screw, 2 is an injection servo motor that moves the screw in the axial direction to inject resin, 3 is a pulse coder that detects the position and speed of the injection servo motor 2, and 4 is a reaction device that acts on the screw. A pressure sensor 5 is a cylinder that detects force as resin pressure.

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

A servo CPU 13 constitutes a part of a digital servo circuit that controls the output torque, speed, and position of the servo motor for each axis of the injection molding machine.The CPU 13 has a bus 25 that is used for temporary storage of data. The RAM 23 is connected to the input/output circuit 24 and a servo shared RAM 16 that stores control programs and setting values for servo control, and the NC CPU 11 is connected to the servo shared RAM 16 via a bus.

A power amplifier 6 is connected to the input/output circuit 24 via a driver 7 having a D/A converter, and the output of the power amplifier 6 drives the injection servo motor 2. In addition, the input/output circuit 24 includes a power amplifier 6.
In other words, the drive current of the injection servo motor 2 is A/
Drive current value data converted by the D converter 9, pressure data converted from the output of the pressure sensor 4 into digital signals by the A/D converter 8, and 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 based on the sequence program in the ROM 19, while the N
The C CPU 11 controls each operation of the injection molding machine using the NC program in the shared RAM 15, outputs a movement command to the servo motor of each axis, and this movement command is temporarily stored in the servo shared RAM 16. In response to movement commands for each axis, the servo CPU 13 executes position and speed loop processing at predetermined intervals 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 the processing executed in each position/velocity loop processing cycle. Below, Figure 2
The processing operation of the first embodiment of the present invention corresponding to claims 1 and 3 will be explained with reference to FIG.

The servo CPU 13 receives the movement command θr, which is obtained by further dividing the movement command to the most advanced position of the screw, which is divided and outputted from the NC CPU 11 for each distribution period, into each position/velocity loop processing period, and the feedback from the pulse coder 3. Position loop processing is performed using pulses in the same manner as in the prior art, and a speed command Vc is calculated (step S1). Further, the 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 determined, and this deviation is multiplied by a proportional gain Kx to calculate the speed command Pc based on the pressure deviation. (Step S2).

The servo CPU 13 that has calculated the speed command Vc based on the position loop processing and the speed command Pc based on the pressure deviation compares the magnitude relationship between the two (step S3), and the value of the speed command Pc based on the pressure deviation is determined to be the speed of the position loop. If it is relatively small compared to the value of the command Vc, the same speed loop processing as before is executed using the speed command Pc based on the pressure deviation (step S4), while the value of the speed command Vc based on the position loop processing is changed to the pressure deviation. If the value is relatively small compared to the value of the base speed command Pc, the speed loop processing is executed in the same way as in the past using the speed command Vc based on the position loop processing (step S5). That is, from the detected actual speed of the servo motor determined from the speed command Vc or Pc and the feedback pulse from the pulse coder 3, PI (proportional, integral) control is performed as in the conventional method to determine the torque command value Tr. Then, the torque command value Tr is delivered to the current loop (step S6), and the processing of the position/velocity loop processing cycle is ended. Also,
In the current loop, the torque command value Tr and the drive current value of the injection servo motor 2 inputted via the A/D converter 9 are used to perform current loop processing similar to the conventional one, and are then sent to the power amplifier 6 via the driver 7. It outputs and drives and controls the injection servo motor 2.

Immediately after the start of injection, filling of the mold with resin is not completed, so 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, the resin pressure that prevents the injection servo motor 2 from acting on the screw 1 does not act on the screw 1, and the injection servo motor 2 follows the movement command from the NC CPU 11, so the position deviation is small and the speed command Vc due to position loop processing is small. The value is relatively small. Therefore, immediately after the start of injection, the injection servo motor 2 is controlled with speed priority based on the speed command Vc based on position loop processing.

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, and the deviation between the set injection pressure Ps and the current injection pressure Pf gradually becomes smaller. , the value of the speed command Pc based on the pressure deviation becomes relatively small. Further, as a result of the screw 1 being prevented from moving forward, the positional deviation increases and the value of the speed command Vc obtained by the position loop processing becomes relatively large. Then, when the speed command Vc by the position loop process exceeds the value of the speed command Pc based on the pressure deviation, the injection servo motor 2 outputs the speed command Pc based on the deviation between the set injection pressure Ps and the current injection pressure Pf. Pressure priority control is performed with the set injection pressure Ps as the target value. If there are no problems such as resin backflow, leakage, or filling defects, the injection control is completed by holding pressure at the set injection pressure Ps for a predetermined time with a certain degree of deviation remaining in the position loop, and the set injection pressure P
Good pressure holding treatment is performed by s.

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 will not increase, so the set injection pressure Ps and the current injection pressure Pf will differ. The deviation of the pressure deviation will not become small, and the speed command Pc based on the pressure deviation will show a large value. On the other hand, since the resin pressure that prevents the injection servo motor 2 from acting on the screw 1 does not act on the screw 1, the injection servo motor 2
follows the movement command from the NC CPU 11, the positional deviation does not increase significantly, and the speed command Vc by position loop processing
The value of does not become large. Therefore, the injection servo motor 2
is driven and controlled up to the final stage by the speed command Vc output from the position loop. The output of the speed command Vc by position loop processing is automatically stopped when the screw 1 moves to the most advanced position and there is no position deviation, so overtravel of the screw 1 is prevented and the tip of the cylinder 5 is Collisions with are prevented.

FIG. 3 is a flowchart of the second embodiment schematically showing the processing executed in each position/velocity loop processing period in the injection control of the servo CPU 13. The structure of the injection molding machine itself is the same as that of the first embodiment described above. Thereafter, similarly to the first embodiment, the servo CPU 13 performs position loop processing to calculate the speed command Vc (step T1),
Furthermore, the torque command value Tr is determined by executing the same speed loop processing as in the past based on the speed command Vc of the position loop and the current speed of the injection servo motor 2 determined from the feedback pulse Vf from the pulse coder 3. (Step T2). Furthermore, the 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 determined, and this deviation is multiplied by a proportional gain Ky to calculate the torque command Tc based on the pressure deviation. (Step T3).

[0028] The servo CPU 1 calculates the torque command Tr based on the speed loop processing and the torque command Tc based on the pressure deviation.
3 compares the magnitude relationship between the two (step T4), and 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 set. The current loop is handed over to the current loop (step T5), and the processing of the position/velocity loop processing cycle is ended. On the other hand, if the value of the torque command Tr based on the speed loop process is relatively small compared to the value of the torque command Tc based on the pressure deviation, the torque command Tr from the speed loop is passed to the current loop (step T6), and the position - Finish the processing of the speed loop processing cycle. In the current loop, the torque command value Tc and the drive current value of the injection servo motor 2 inputted via the A/D converter 9 are used to perform current loop processing in the same way as in the conventional method, and are then sent to the power amplifier 6 via the driver 7. It outputs and drives and controls the injection servo motor 2.

Since the value of the torque command Tr from the speed loop depends on the positional deviation and the speed deviation, the phenomenon occurring during injection control is the same as in the first embodiment described above.

That is, 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 prevents the drive of the motor 2 does not act, the injection servo motor 2 is used as the NC CP.
Following the movement command from U11, the value of the torque command Tr from the speed loop becomes relatively small. Therefore, immediately after the start of injection, the injection servo motor 2 is preferentially controlled by the torque command Tr of the speed loop.

[0031] Furthermore, 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, and the deviation between the set injection pressure Ts and the current injection pressure Tf gradually decreases. The torque command Tc based on the pressure deviation is
As the value of becomes relatively small, the forward movement of the screw 1 is hindered, and 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 becomes relatively large. Then, when the torque command Tr of the speed loop exceeds the value of the torque command Tc based on the pressure deviation,
The injection servo motor 2 is controlled with priority so that the set injection pressure Ts is a target value based on the torque command Tc output based on the deviation between the set injection pressure Ts and the current injection pressure Tf. If there are no problems such as resin backflow, leakage, or filling defects, there will be a certain degree of positional deviation in the position loop and velocity loop.
Pressure holding using the set injection pressure Ts is performed for a predetermined time while the speed deviation remains, and the injection control is completed, and good pressure holding processing using 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 will not increase, so the deviation between the set injection pressure Ts and the current injection pressure Tf will not become smaller. Torque command T based on resultant pressure deviation
c becomes larger. On the other hand, as a result of the injection servo motor 2 following the movement command from the NC CPU 11, positional deviation,
The speed deviation does not increase and the torque command Tr from the speed loop
The value of does not become large. Therefore, the injection servo motor 2
is driven and controlled up to the final stage by the torque command Tr output from the speed loop. The output of the torque command Tr is automatically stopped when the screw 1 moves to the most advanced position and there is no position deviation, so overtravel of the screw 1 is prevented.
Collision with the tip of the cylinder 5 is prevented.

Next, when the injection servo motor 2 is driven by applying a conventional analog type servo circuit instead of the digital servo circuit consisting of the servo CPU 13, RAM 23, servo shared RAM 16, etc. An example will be described.

FIG. 4 is a block diagram of a third embodiment schematically showing the configuration of a servo circuit related to the injection servo motor 2. As shown in FIG. The configuration of the main parts related to the injection molding machine and the control device 10 is the same as that of the first and second embodiments described above, and in FIG.
6, 23, 24, etc. are simply replaced with conventionally known analog servo circuits, and since they are conventionally well known, the details will be omitted.

A block 26 constitutes a position loop, which is composed of an error register including a reversible counter, a D/A converter, an amplifier, etc., and integrates the distributed pulse θr from the NC CPU 11, as well as integrates the distributed pulse θr from the pulse coder 3. The feedback pulse θf regarding the position is subtracted, and this value, that is, the value of the error amount for the position command, is sequentially D/A converted and output as the speed command Vc. 27 is a block constituting a speed loop, which includes an error amplifier and the like, and calculates the speed deviation between the input speed command and the current speed Vf obtained by F/V conversion of the feedback pulse θf from the pulse coder 3 by PI( (proportional, integral) control to amplify and output torque command Tr. 28 is a block constituting a current loop, which is composed of an error amplifier and the like, and is connected to the input torque command Tr and the power amplifier 2 that flows to the injection servo motor 2.
The injection servo motor 2 is driven and controlled by outputting the deviation of the drive current from the servo motor 9 to the power amplifier 29.

Reference numeral 4 designates a pressure sensor similar to the first and second embodiments described above, which detects the reaction force acting on the screw 1 forming a part of the injection mechanism as resin pressure. These configurations are the same as those of a conventional electric injection molding machine, but in this 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 also used. The deviation of speed command Pc
A differential amplifier 30 is provided between the position loop 26 and the speed loop 27 as a speed command means for outputting the speed command Pc from the differential amplifier 30 and the position loop 27. A changeover switch 32 for switching between the speed command Vc and the speed command Vc from 26 is provided. The changeover switch 32 is switched by the output of a comparator 31 that 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
0, while if 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 phenomena occurring during injection control are the same as in the first embodiment described above.

That is, immediately after the start of injection, filling of the resin into the mold is not completed, so 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,
There is no resin pressure acting on the screw 1 that prevents the injection servo motor 2 from driving, and the injection servo motor 2 is connected to the NC CPU.
11, the value of the speed command Vc from the position loop 26 becomes relatively small. 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 priority given to speed.

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, and the deviation between the set injection pressure Ps and the current injection pressure Pf gradually becomes smaller. , 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 from the position loop 26 becomes smaller. The value becomes relatively large. When the speed command Vc from the position loop 26 exceeds the speed command Pc from the differential amplifier 30, the changeover switch 32 is connected to the differential amplifier 30 side, and the injection servo motor 2 is output from the differential amplifier 30. Speed command Pc
Pressure feedback control is performed using the set injection pressure Ps as a target value, and pressure priority control is performed. If there are no problems such as resin backflow, leakage, or filling defects, the injection control is completed by holding the set injection pressure Ps for a predetermined time with some deviation remaining in the position loop 26, and the set injection is completed. A good pressure holding process is performed using the pressure Ps.

On the other hand, if the resin is insufficiently filled or a backflow occurs, the resin pressure will not increase, so the difference between the set injection pressure Ps and the current injection pressure Pf, that is, the difference
The value of the speed command Pc from 0 is maintained at a large value. Further, since the injection servo motor 2 follows the movement command from the NC CPU 11, the speed command Vc from the position loop 26 does not become large. Therefore, the changeover switch 32 remains connected to the position loop 26 side, and the injection servo motor 2 is controlled by the speed command Vc output from the position loop 26.
The drive will be controlled until the final stage. The speed command Vc from the position loop 26 is automatically stopped when the screw 1 moves to the most advanced position, and the position deviation becomes 0. Therefore, overtravel of the screw 1 is prevented, and the connection with the tip of the cylinder 5 is prevented. Collisions are prevented.

FIG. 5 is a block diagram of a fourth embodiment of the present invention using an analog servo circuit. This fourth embodiment has almost the same configuration as the third embodiment, and the difference is that in the third embodiment, a changeover switch is provided between the position loop and the speed loop, whereas in this fourth embodiment, the changeover switch is provided between the position loop and the speed loop. In the fourth embodiment, it is provided between the speed loop and the current loop, and the torque command input to the current loop is switched between the speed loop and the output of the differential amplifier. That is, the changeover switch 34 selects the torque command Tc from the differential amplifier 33 and the speed loop 27.
When the torque command Tc is smaller than the torque command Tr, it is connected to the differential amplifier 33; If it is smaller than , it is connected to the speed loop 27 side.

[0042] Immediately after the start of injection, the set injection pressure Ts
The deviation between the current injection pressure Tf and the current injection pressure Tf is large, and the value of the torque command Tc output from the differential amplifier 33 based on the pressure deviation becomes relatively large. On the other hand, the injection servo motor 2 is N
Since the movement command from the C CPU 11 is followed, the value of the torque command Tr from the speed loop 27 becomes relatively small, and immediately after the start of injection, the injection servo motor 2 is driven by the torque command Tr from the speed loop 27. Priority control is applied.

Furthermore, 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, and the deviation between the set injection pressure Ts and the current injection pressure Tf gradually decreases. Then, based on the pressure deviation, the differential amplifier 3
As the value of the torque command Tc output from the speed loop 27 becomes relatively small, the forward movement of the screw 1 is hindered, and as a result, the position deviation and speed deviation increase, and the value of the torque command Tr from the speed loop 27 becomes relatively small. growing. Then, 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 servo motor 2
Priority control is performed using the set injection pressure Ts as a target value based on the torque command Tc output based on the deviation between the set injection pressure Ts and the current injection pressure Tf. If there are no problems such as resin backflow, leakage, or filling defects, pressure holding at the set injection pressure Ts is performed for a predetermined period of time with a certain degree of position deviation and speed deviation remaining in the position loop 26 and speed loop 27. Injection control is completed, and good pressure holding processing is performed using the set injection pressure Ts.

On the other hand, if resin filling is insufficient or a backflow occurs, the resin pressure in the cylinder 5 will not increase, so the differential amplifier 33 The torque command Tc output from the injection servo motor 2 does not become small, and the injection servo motor 2
Since it follows the movement command from PU11, speed loop 2
Since the value of the torque command Tr from 7 does not become large, the changeover switch 34 is connected to the speed loop side. Therefore,
The injection servo motor 2 is driven and controlled by the torque command Tr output from the speed loop 27 until the final stage. The output of the torque command Tr is automatically stopped when the screw 1 moves to the most advanced position and there is no position deviation, so overtravel of the screw 1 is prevented and collision with the tip of the cylinder 5 is prevented. thwarted.

[0045]

Effects of the Invention The present invention provides speed commands and torque commands that are output based on the deviation between the set injection pressure and the current injection pressure at the stage of injection control, and speed commands from the position loop that controls the injection servo motor. The torque command from the speed loop and the torque command are compared one after another, and the injection servo motor is driven based on the smaller command value, so priority control of speed at the injection start stage and injection that presses the filled resin are performed. Holding 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, position control due to position deviation can be performed. The screw automatically stops at the most advanced position due to the speed command from the loop and the torque command based on this speed command.
Screw overtravel and collision accidents due to insufficient filling etc. are prevented.

[Brief explanation of drawings]

[Fig. 1] A block diagram showing the main parts of an electric injection molding machine according to an embodiment in which the method of the present invention is applied to a digital servo.

[Figure 2
] A flowchart of the first embodiment showing an outline of the processing executed by the servo CPU in each position/velocity loop processing cycle during injection control in the electric injection molding machine of the same embodiment.

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

1 Screw 2 Servo motor for injection 3 Pulse coder 4 Pressure sensor 10 Control device 13 Servo CPU 30 Differential amplifier 31 as speed command means Comparator 32 Changeover switch 33 Differential amplifier 34 as torque command means Changeover switch 35 Comparator

Claims (4)

[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 injection pressure, and controlling at least a position loop and a speed loop to control the injection servo motor. In an injection control method for an electric injection molding machine that controls a motor, the injection servo motor is driven by outputting a movement command to the screw most advanced position, and the injection control method is performed based on the deviation between the set injection pressure and the current injection pressure. The magnitude relationship between the output speed command and the speed command output from the position loop is successively compared,
An injection control method for an electric injection molding machine characterized by performing speed loop control based on a speed command having a smaller value to drive an injection servo motor. 2. A servo motor for injection, a detector for detecting the position and speed of the screw, and a pressure sensor for detecting the injection pressure, and controlling at least a position loop and a speed loop to control the injection servo motor. In an injection control method for an electric injection molding machine that controls a motor, the injection servo motor is driven by outputting a movement command to the screw most advanced position, and the injection control method is performed based on the deviation between the set injection pressure and the current injection pressure. An electric injection molding machine that successively compares the magnitude relationship between an output torque command and a torque command output from a speed loop, and drives an injection servo motor based on the torque command with a smaller value. injection control method. 3. An electric injection molding machine comprising an injection servo motor, a detector for detecting the position and speed of a screw, and a servo circuit having a position loop and a speed loop for controlling the injection servo motor. The injection control device includes a pressure sensor that detects injection pressure, a speed command means that outputs a speed command based on a deviation between a set injection pressure and a current injection pressure detected by the pressure sensor, and a position loop of the servo circuit. a comparison means for comparing the output of the output from the speed command means with the output from the speed command means, and a speed command input to the speed loop of the servo circuit based on the signal from the comparison means, from the position loop output or the speed command means. an injection control device for an electric injection molding machine, wherein the switching means inputs the smaller of the output of the position loop and the output of the speed command means to the speed loop. 4. An electric injection molding machine comprising an injection servo motor, a detector for detecting the position and speed of a screw, and a servo circuit having a position loop and a speed loop for controlling the injection servo motor. The injection control device includes a pressure sensor that detects injection pressure, a torque command means that outputs a torque command based on a deviation between a set injection pressure and a current injection pressure detected by the pressure sensor, and a speed loop of the servo circuit. and a comparison means for comparing the output from the torque command means with the output from the torque command means; An injection control device for an electric injection molding machine, wherein the switching means inputs the smaller of the output of the speed loop and the output of the torque command means to the injection servo motor. .