JP2001038787A - Overload avoiding method in motor-operated injection molding machine and motor-operated injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel method capable of advantageously avoiding the generation of the thermal overload state in a or the driver thereof while avoiding the adverse effect on a molding cycle to the utmost in an electromotive injection molding machine. SOLUTION: At a point of time when the thermal load value of a motor or driver reaches a reference value just before reaching an immediate current stop level, at least one overload avoiding operation among first overload avoiding operation wherein a weighing process is omitted if the weighing of a molding material is not started or immediately stopped if the molding material is being weighted or a next weighing process is omitted if weighing is furnished to complete the present molding cycle and, if the molding material remains in a heating cylinder, it is discharged out of a mold to set the mold to a closed state and a molding cycle is interrupted, second overload avoiding operation wherein at least one of a mold closing speed and a mold opening speed is lowered and third overload avoiding operation wherein the delay time from the completion of mold closing to the start of the injection of the molding material is increased is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine employing at least one electric motor as a driving means of an injection device, while minimizing or preventing an adverse effect on a molding cycle. The present invention relates to a method for avoiding overload in an electric injection molding machine, which can advantageously avoid occurrence of an overload state.

[0002]

2. Description of the Related Art Conventionally, as a type of injection molding machine, an injection screw or an injection plunger inserted into a heating cylinder is driven by an electric motor, so that the molding material heated and melted and measured in the heating cylinder is clamped. An electric injection molding machine that injects and fills into the mold cavity of the mold closed by the device, holds the pressure, cools, opens the mold, releases the mold, and removes it to form the desired molded product. As compared to a hydraulic injection device using a hydraulic motor, there is no need for a hydraulic circuit etc., maintenance is easy, and a decrease in control accuracy due to a temperature change of hydraulic oil is avoided. In addition, since closed-loop control can be easily realized, it is suitably used particularly for molding relatively small resin products that require high control accuracy during molding.

[0003] In such an electric injection molding machine, the required driving force of the injection screw and the like greatly differs in each of the steps of measuring, injecting, and holding pressure of the molding material. For this reason, in general, an electric motor having a capacity such that the driving current supplied to the electric motor at the time of supplying the maximum driving force exceeds the continuous rated current value in consideration of efficiency, economy, and the like. However, when such an electric motor is employed, the electric motor or its power supply driver may reach a thermal overload state depending on molding conditions. Therefore, an electric motor or the like is generally provided with its own protection circuit. When a thermal overload state is reached, power supply to the electric motor or the like is immediately stopped, and the electric motor and the driver and the like are stopped. Circuits and electrical devices are being protected.

[0004] However, during molding by an electric injection molding machine, if the power supply is suddenly stopped when the electric motor or the like is thermally overloaded, the operation of the injection molding machine itself is immediately stopped. In some cases, the molding cycle was adversely affected, particularly at the start of molding after the thermal overload condition was resolved. If the power is stopped during the injection process, the operation will stop in a short shot state,
If the power supply is stopped during the pressure-holding process after injection, the operation will stop with the resin material remaining in the molding cavity. In any case, if the resin material remains in the molding cavity, the molded product adheres to the molding die due to heat shrinkage during cooling because the operation stops in a state where the resin material remains. Failure to do so will make it extremely difficult to remove it later, and if resin material remains in the heating cylinder, thermal decomposition due to overheating of the resin material will cause defects during subsequent molding. is there.

[0005] Furthermore, when the power supply is stopped and the injection molding machine is stopped in a mold open state in a molded product removal process or the like, a defect such as a short shot is likely to occur in the recovered molded product. . This is considered to be due to the fact that the surface temperature of the mold is significantly reduced by being stopped and left in the mold open state. In addition, there is a problem that a long time is required due to overheating of the mold at the start of molding after recovery.

[0006]

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an electric injection molding machine with a thermal overheat in an electric motor and its driver. The occurrence of a load condition can be advantageously avoided while minimizing or preventing the adverse effects on the molding cycle now and after recovery.
It is to provide a new overload avoidance method.

Further, the present invention advantageously avoids the occurrence of a thermal overload condition in an electric motor or its driver while minimizing or preventing the adverse effects on the molding cycle at present and after recovery. It is another object of the present invention to provide a motor-driven injection molding machine having a novel structure capable of performing the above-described operations.

[0008]

An embodiment of the present invention which has been made to solve such a problem will be described below. In addition, each aspect described below can be adopted in any combination. Further, aspects or technical features of the present invention are described in the entire specification and the drawings without being limited to those described below.
Alternatively, it should be understood that the present invention is recognized based on the inventive concept that can be grasped by those skilled in the art from the description thereof.

First, a feature of the present invention relating to an overload avoiding method is that electric injection molding in which a molding material is measured, injected, and held by an injection device using at least one electric motor. A thermal load value at the electric motor and / or its driver is determined at least at a time interval shorter than the molding cycle, and the thermal load value is preset at a value smaller than the instantaneous current stop level. When the reference value is exceeded, at least one of the following first, second and third overload avoiding operations is executed. (A) If the thermal load value exceeds the reference value before the injection device starts measuring the molding material for the next molding, the measuring step of the molding material for the next molding is omitted and the current step is omitted. While the molding cycle is completed and the molding cycle is interrupted after closing the mold, if the thermal load value exceeds the reference value during the measurement of the molding material for the next molding by the injection device, such a molding for the next molding is performed. If the measurement of the molding material is stopped and the thermal load value exceeds the reference value after the injection device measures the molding material for the next molding, the current molding cycle is completed and the mold is closed. In addition, a first overload avoidance operation for interrupting the molding cycle after discharging the measured molding material out of the mold. (B) A second overload avoidance operation for reducing at least one of the mold closing speed and the mold opening speed. (C) A third overload avoidance operation for increasing a delay time from completion of mold closing to start of injection of molding material.

According to the method of the present invention, the overload avoiding operation is performed at a level before the thermal load value of the electric motor or the driver reaches the instantaneous current stop level, and In a situation where the thermal overload state has not yet been reached, by performing a specific thermal overload avoidance operation, the adverse effect on the molding process of the resin material is reduced as much as possible, and the thermal overload is reduced. The occurrence of the state can be prevented beforehand.

In this case, the first, second and third overload avoiding operations are employed alone or in combination as the thermal overload avoiding operation. Even in the case where the molding material is left inside the molding die or the heating cylinder in the injection device, it is not interrupted, etc. There is no problem such as thermal decomposition.

In addition, no matter which of the first, second and third overload avoiding operations is executed, the mold opening state of the mold is not continuously maintained for a long time. Therefore, the occurrence of inconveniences such as molding failure due to a decrease in the temperature of the mold can be advantageously reduced or avoided.

In particular, if the first overload avoiding operation is selected, the cooling time is secured by interrupting the molding cycle, so that the thermal overload state can be avoided more reliably and promptly. Furthermore, if only the second and / or third overload avoidance operation is selected, the average load rate during one molding cycle can be reduced without interrupting the molding cycle, and the molding cycle is interrupted. Since there is no need, there is an advantage that a special operation is not required and it is possible to respond more easily.

Furthermore, these first, second and third overload avoiding operations can be employed in any combination. In that case, for example, it is also effective to employ a combination of the second and / or third overload avoidance operation with respect to the first overload avoidance operation,
(I) By performing the second and / or third overload avoiding operation in the process up to the completion of the current molding cycle in the first overload avoiding operation, the heat up to the completion of the current molding cycle can be obtained. Or (ii) when the first overload avoidance operation is completed and the molding cycle is restarted, the second and / or third By performing the overload avoiding operation, it is possible to minimize the interruption time of the molding cycle in the first overload avoiding operation.

The electric injection molding machine to which the method of the present invention is applied may be any type as long as the driving means necessary for the injection molding operation includes at least one electric motor. For example, a hydraulic cylinder other than the electric motor may be provided for the specific operation. Also,
In the present invention, as the electric motor, generally, a servo motor using a synchronous motor or the like is preferably suitably used, but is not particularly limited, and according to an intended use.
A known electric motor can be appropriately selected and adopted. Furthermore, the driver is a power supply device for the electric motor, and generally includes an amplifier configured by a transistor or the like,
Various types of structures that generate a drive current from a control signal of the electric motor and supply power to the electric motor may be employed. When the electric motor and the driver are both more than one, the thermal load value may be obtained separately for each of the electric motor and the driver. In such a case, a thermal load value may be obtained for one of the electric motor and its driver, or a thermal load value may be obtained for a specific electric motor or driver.

Here, the thermal load value is preferably obtained by time-integrating a torque command value of the electric motor by the driver. Although it is possible to cover and integrate the current value actually supplied to the electric motor with time, it is easier to use the torque command value obtained by calculation in the driver than to use it. This is because there is an advantage. Although the thermal load value can be obtained as an instantaneous value of a command value or a supply current value to the electric motor, adopting an integral value has advantages such as high-precision control and the like. is there. Further, when obtaining the thermal load value as an instantaneous value or as an integral value, a sufficiently short time interval of preferably 20 ms or less, more preferably 2 ms or less, for example, by an interrupt routine or the like in a control program. It is desirable to perform detection periodically.

The instantaneous current stop level is an allowable limit value for protection set for an electric device or an electric circuit, which is generally set to prevent physical damage. In consideration of the amount of heat and the like generated due to the overload avoidance operation, the occurrence of the thermal overload state is set to a value smaller than the immediate current stop level so that the overload avoidance operation can be effectively avoided. Is set. Where
The reference value is desirably changed and set as appropriate. For example, the reference value may be set directly by manual input from the outside, or may be automatically set from various molding conditions.

Another feature of the present invention relating to the electric injection molding machine is that an electric injection molding machine in which at least one electric motor is used for measuring, injecting, and holding pressure of a molding material by an injection device. In the molding machine, (a) means for detecting a thermal load value of the electric motor and / or its driver at least at a time interval shorter than a molding cycle; and (b) a thermal load value obtained by the detecting means. The thermal load value is compared with a preset reference value at a value smaller than the instantaneous current stop level, and when the thermal load value exceeds the reference value, an alarm that outputs an alarm signal before overload is output. (C) execution instruction means for issuing an overload avoidance operation execution instruction signal to the controller of the injection molding machine when the pre-overload alarm signal is output by the alarm issuing means; The overload avoiding operation instructed by the execution command means to the controller of the injection molding machine includes: (a) before the injection device starts measuring the molding material for the next molding, the thermal load value is set to the reference value. In the case of exceeding the above, the measuring step of the molding material for the next molding is omitted, the current molding cycle is completed, and the molding cycle is interrupted after the mold is closed, while the molding device for the next molding is injected by the injection device. If the thermal load exceeds the reference value during weighing,
If the measurement of the molding material for the next molding is stopped and the thermal load value exceeds the reference value after the measurement of the molding material for the next molding by the injection device, the current molding cycle is completed. A first overload avoiding operation for closing the mold and interrupting the molding cycle after discharging the measured molding material out of the mold, and (b) a second for reducing at least one of the mold closing speed and the mold opening speed. Overload avoidance operation of
(C) a third overload avoiding operation for increasing a delay time from completion of mold closing to start of injection of molding material, and operation selecting means for selectively setting one or more of the operations. It is in.

In the electric injection molding machine having such a structure according to the present invention, the thermal load value of the electric motor or the driver is monitored by the detecting means, and the thermal load value immediately reaches the current stop level. Also, when the predetermined level is reached by a predetermined amount, a warning signal is issued by the warning issuing means. Then, based on this alarm signal, an execution command signal of the overload avoiding operation is issued to the controller of the injection molding apparatus by the execution command means, and the same as that employed in the above-described overload avoiding method according to the present invention. At least one of the first, second and third overload avoiding operations selected by the operation selecting means is executed.

Therefore, in such an injection molding machine, the overload avoiding method according to the method of the present invention as described above can be advantageously carried out, whereby the adverse effect on the molding cycle is reduced or avoided as much as possible. On the other hand, the effects based on the method of the present invention as described above, such as the occurrence of a thermal overload state can be effectively prevented.

Further, in the electric injection molding machine having the structure according to the present invention, the first setting means for changing and setting the magnitude of the reference value in the alarm issuing means is preferably employed. By adopting such a first setting means, the stability of the molding cycle and the avoidance of thermal overload can be further improved in accordance with various set molding conditions and the adopted overload avoidance operation. It is possible to achieve both. The change setting of the magnitude of the reference value in the first setting means may be automatically performed based on a set molding condition or the like, in addition to a manual input from the outside.

Further, in the electric injection molding machine having the structure according to the present invention, the amount of decrease in the speed in the second overload avoiding operation and the amount of increase in the delay time in the third overload avoiding operation. The second setting means for changing and setting at least one of the sizes is preferably adopted. If such a second setting means is employed, the molding cycle can be stabilized in the case where the second overload avoiding operation or the third overload avoiding operation is employed, corresponding to various set molding conditions and the like. Thus, it is possible to achieve a higher degree of compatibility between performance and avoidance of thermal overload.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, in order to clarify the present invention more specifically, embodiments of the present invention will be described in detail with reference to the drawings.

First, FIG. 1 schematically shows a hardware configuration of an electric injection molding machine as one embodiment of the present invention. Such an injection molding machine includes an injection molding machine main body 10 and a controller 12 thereof. The injection molding machine body 10 includes a plurality of servomotors 14 as electric motors as drive sources, and the controller 12 controls a servo amplifier 16 as a driver for supplying a drive current to each of the servomotors 14.
Are provided.

More specifically, the main body 10 of the injection molding machine can be constituted by a known device having a mold clamping device 18 and an injection device 20, for example, as shown in FIG. That is, the mold clamping device 18 includes a mold clamping mechanism 22 such as a hydraulic type or an electric type.
The mold is opened and closed with each other to form a molding cavity between the mold mating surfaces. On the other hand, the injection device 20 is constituted by an electric injection device having a heating cylinder 28 in which an injection screw is inserted and arranged, and guides the resin material supplied from the hopper 30 into the heating cylinder 28, and performs a servomotor for measurement. 14
By rotating and driving the injection screw at -1, the resin material is heated and melted, fed forward and weighed while applying back pressure, and then driven by the injection servo motor 14-2 to project the injection screw in the axial direction. A predetermined amount of the molten resin material is injected from a nozzle, and is filled in a molding cavity of a molding die matched by the mold clamping device 18. Then, after holding and cooling the molten resin filled in the molding cavity, the molding die is opened by the mold clamping device 18, whereby the intended molded product is released and removed. It is. In the injection device 20, in addition to the servo motor 14-1 for measurement and the servo motor 14-2 for injection, various driving motors such as a servo motor for holding the resin material filled in the molding cavity, and the like. Servo motors can be employed.

The mold clamping device 18 and the injection device 20
Is controlled by the controller 12 to thereby control the mold clamping device 1.
The mold opening / closing speed, mold clamping pressure, etc. in 8, and the injection speed, holding pressure, etc. in the injection device 20 are controlled according to time charts, respectively, so that the desired molding operation is repeatedly performed. The operation control of the injection molding machine main body 10 by the controller 12 is performed in such a manner that a control signal: S1 to various driving devices constituting the injection molding machine main body 10 is detected by various sensors, limit switches, and the like. This is advantageously performed by feedback control that is controlled based on the detection signal: S2.

In addition, drive currents I-1 to I-I are supplied to various drive servomotors 14-1 to 14-n such as a measuring servomotor and an injection servomotor in the injection device 20.
Each of the servo amplifiers 16-1 to 16-n for supplying −n includes a CPU in addition to the power transistor for amplification, and constitutes a lower-level controller of the controller 12. Then, based on the control signals S3-1 to S3-n, such as torque commands, required by the upper controller 12 for the drive servomotors 14-1 to 14-n, the drive servomotors 14-1 to 14-n are used. By determining the supply current to 14-n, the operation of the injection molding machine main body 10 is controlled.

In this case, each of the servo amplifiers 16-1 to 16-1
16-n are torque commands (control signals) input from the host controller 12, respectively: S3-1 to S3-n
Or the driving servo motors 14-1 to 14-n and the servo amplifier 1 based on the driving currents I-1 to In supplied to the driving servo motors 14-1 to 14-n.
The thermal load value of at least one of 6-1 to 16-n is determined. When the obtained thermal load value exceeds a preset reference value, the pre-overload alarm signals: S4-1 to S4-n are transmitted to the injection molding machine main body 1.
0 is output to the upper-level controller 12 that controls the operation.
The controller 12 receiving 1 to S4-n outputs a drive signal: S1 for executing a predetermined overload avoiding operation to the injection molding machine main body 10.

The reference value can be manually input directly to the controller 12, for example.
It is set to a value smaller than the instantaneous current stop level in the servo amplifiers 16-1 to 16-n. Specifically, for example, 90 to 95% of the immediate current stop level
Can be advantageously set for the value of Note that the immediate current stop level is generally recognized as a maximum allowable current level set to avoid physical damage such as burnout in a power element such as a motor or a power transistor due to heating.

The overload avoiding operation is, specifically, (a) a first overload avoiding operation for temporarily interrupting a molding cycle, and (b) at least one of a mold closing speed and a mold opening speed. A second overload avoidance action to reduce
And (c) a third overload avoiding operation for increasing the delay time from the completion of the closing of the mold to the start of injection of the molding material. This is performed by being output as Any of these (a), (b), and (c) can be used alone, but any two of them may be used in any combination, or all three may be used. May be.

The time required for opening and closing the mold is increased by executing the second overload avoiding operation, or the time required for starting the injection is increased by executing the third overload avoiding operation. As a result, the average load ratio during one molding cycle is reduced. That is, in the second and third overload avoiding operations, it is possible to avoid the occurrence of the overload state while continuing the molding cycle without being temporarily stopped.

The injection of the molding material is started after the mold closing speed and the mold opening speed are reduced when the second overload avoiding operation is performed, and when the mold closing is completed when the third overload avoiding operation is performed. The amount of increase in the delay time until can be set manually, for example, directly to the controller 12 by considering the difference between the instantaneous current stop level and the reference value, molding conditions, and the like. Further, considering whether the second overload avoiding operation or the third overload avoiding operation is employed alone or in combination with the other, the occurrence of a thermal overload state is considered. Is set to be able to be avoided.

On the other hand, the first overload avoiding operation temporarily interrupts the molding cycle. In particular, the first overload avoiding operation is specially performed so that adverse effects on the molding cycle after recovery are avoided as much as possible. Operation mode is adopted. One specific form of the first overload avoiding operation will be described more specifically below with reference to flowcharts shown in FIGS.

First, during the injection operation of the injection molding machine body 10 by the controller 12, the overload detection processing as shown in FIG. 3 is repeatedly performed at a predetermined interval shorter than one molding cycle. The overload detection process is performed, for example, by a higher-level controller 1 that controls the operation of the injection molding machine body 10.
In 2, it is possible to execute the interrupt routine by executing it at predetermined time intervals.

That is, in the overload detection process, when started, in steps: Q1 to Q4, a pre-overload alarm detection flag (Q1) indicating that a pre-overload alarm signal has been issued from any of the servo amplifiers 16 is issued. ), A measurement omitting flag (Q2) indicating that a signal for omitting the measuring step has been issued in the injection device 20,
And a discharge flag (Q4) indicating that a signal for discharging the molten resin measured by the injection device 20 from the heating cylinder 28 has been issued. ) And
Set to OFF and reset.

Next, in step Q5, a warning signal before overload is issued from any of the servo amplifiers 16 (O).
N) It is determined whether or not it has been performed. If the pre-overload alarm signal has not been issued, the overload detection flow is immediately terminated, and a normal molding cycle is executed.

On the other hand, if the pre-overload alarm signal has been issued, the process proceeds to step Q6, where the detection flag of the overload alarm signal is set to ON, and in step Q7, the present time is set to the molding material for the next molding. It is determined whether or not the weighing is started before. If the weighing is not started, the weighing omission flag for omitting the weighing of the molding material for the next molding is set to ON in step Q8, while the weighing is started. If it is later, in step Q9, a discharge flag for discharging the already measured molten resin is set ON. Furthermore,
In the following step Q10, it is determined whether or not the present time is during the weighing of the molding material for the next molding. If the weighing is not being performed, the overload detection processing is terminated as it is.
In step Q11, a weighing interruption flag for interrupting the weighing is set to ON, and thereafter, the overload detection process ends.

Then, according to the execution result of such overload detection processing, that is, ON / O of the alarm detection flag before overload, the weighing omission flag, the weighing interruption flag and the discharge flag.
According to the FF state, the first overload avoidance operation is incorporated and executed in each of (i) the plasticizing and measuring step of the molding material and (ii) the starting step of the molding cycle during the execution of the molding cycle. Becomes

That is, in the plasticizing / metering process of the molding material in the injection molding machine, the plasticizing process control process according to FIG. 4 is executed, so that the first process is performed according to the execution result of the overload detecting process as described above. An overload avoiding operation is incorporated and executed.

In the plasticizing process control process, first, when the plasticizing and measuring process starts, the process proceeds to Step P1.
, The ON / OFF state of the measurement omission flag is determined, and if the measurement omission flag is ON, the plasticization / metering process is immediately terminated without plasticizing / metering the molding material. On the other hand, if the measurement omission flag is in the OFF state, the process proceeds to Step P2, and the injection device 20 starts the measurement. During the weighing, the determination of the completion of the weighing in Step P3 and the determination of the ON / OFF state of the weighing suspension flag in Step P4 are executed in a subroutine at a predetermined processing interval.

In the plasticizing / metering step, if the measurement suspending flag is turned on, the plasticizing / metering step is immediately terminated. On the other hand, if the measurement suspending flag is maintained in the off state, the metering is completed. finish.

Further, for the start step of the molding cycle in the injection molding machine, the start processing of the molding cycle according to FIG. 5 is executed, and according to the execution result of the overload detection processing as described above (see FIG. 3). , The first overload avoidance operation is incorporated and executed.

In the start processing of the molding cycle, first, when the molded article is released from the mold and taken out, the current molding cycle is completed and the start processing of the next molding cycle is started. The ON / OFF state of the detection flag is determined. If the pre-overload alarm detection flag is OFF, the molding cycle is continued, the molding cycle start step is immediately terminated, and the next molding cycle is immediately started.

On the other hand, if the pre-overload alarm detection flag is ON, the routine proceeds to step R2, where the mold clamping device 18 performs a mold closing operation to mold the fixed mold 24 and the movable mold 26 together. In step R3, the injection device 2
0, a nozzle retreat operation is performed, and the heating cylinder 28 is retreated in a direction away from the molding die.
Is moved away from the mold. Further, in the following step R4, the ON / OFF state of the discharge flag is determined.
In step 5, the injection device 20 executes an injection process to
After the molten resin remaining in the inside is discharged out of the molding cavity, in step R6, the molding cycle is stopped, a temporary interruption state is entered to avoid an overload state, and the molding cycle start step is ended. . On the other hand, if the discharge flag is in the OFF state, the process immediately proceeds to step R6,
The molding cycle is stopped, a temporary interruption state is entered to avoid an overload state, and the molding cycle start process is terminated.

That is, according to the first overload avoiding operation incorporated in the molding cycle according to the plasticizing process control process and the molding cycle start process, the pre-overload alarm signal is generated at any point during the execution of the molding cycle. Even when the output is made, the resin material is discharged from both the inside of the heating cylinder 28 of the injection device and the inside of the molding cavity of the mold clamping device 18, and the fixed mold 24 and the movable mold 26 of the mold clamping device 18 are closed. In this state, a temporary interruption of the molding cycle is executed.

Therefore, even when the first overload avoiding operation is performed, a molding defect after the recovery of the molding cycle due to the thermal decomposition of the resin material remaining in the heating cylinder 28 is avoided, and the inside of the molding cavity is prevented. It is possible to completely avoid the difficulty in releasing the molded product due to the heat shrinkage of the resin material remaining in the mold. Further, during the period in which the molding cycle is interrupted, the fixed mold 24 and the movable mold 26 are closed. Since the state is maintained, molding defects after the molding cycle recovery due to supercooling of the dies 24 and 26 can be advantageously reduced or avoided.

In particular, considering the thermal overload state of the servomotor 14 in each step in the injection molding cycle,
Even during weighing, if the pre-overload alarm is output until the completion of weighing, the weighing is immediately stopped, so that the occurrence of a thermal overload state can be extremely advantageously avoided, If the pre-overload alarm is output after the completion of weighing, the molding cycle is interrupted after the weighed resin material has been molded without performing weighing for the next molding. The amount of disposal etc. can be reduced as much as possible.

As is apparent from the above description, in the present embodiment, the thermal load value detecting means and the alarm issuing means for issuing the pre-overload alarm signal are both arithmetic processing by the CPU of the servo amplifier. The execution instruction means for issuing an execution instruction signal of the overload avoidance operation is realized by the operation of the host controller 12 which generates the control signal of the injection molding machine main body 10. The operation selection means for selectively setting the first, second, and third overload avoidance operations is realized by external input means for the controller 12 using a keyboard or the like, and the magnitude of the reference value is set. First setting means for changing and setting, and second setting for changing and setting the amount of decrease in speed in the second overload avoiding operation and the amount of increase in delay time in the third overload avoiding operation. The means is also realized by external input means for the controller 12.

Although the embodiments of the present invention have been described in detail above, these are merely examples, and the present invention is not to be construed as being limited by the specific description in the embodiments.

For example, in an injection molding machine provided with a plurality of servomotors 14, the overload state may be monitored for only some servomotors 14 and the drivers that are likely to be overloaded. When a three-phase electric motor is employed, the overload state can be monitored for each phase based on the supply current value for each phase and the like.

The above-described processing for avoiding thermal overload can be applied not only to the electric motor in the injection device 20 but also to the electric motor in the mold clamping mechanism 22.

Further, in order to determine the thermal overload state of the electric motor or the driver, not only the instantaneous value and the integral value such as the command torque value and the supply current value to the electric motor, but also the differential value is considered. It is also possible to realize a more appropriate overload avoidance operation corresponding to the actual injection molding operation. Specifically, for example, when the command torque value or the supply current value to the electric motor suddenly increases, the reference value may be changed to a smaller value, or the first overload avoidance operation may be employed to form the molding cycle. If the command torque value or the supply current value to the electric motor is increasing slowly, change the reference value to a large value, or use only the second and / or third overload avoidance operation. It is conceivable to take measures while continuing the molding cycle.

In addition, although not enumerated one by one, the present invention
Based on the knowledge of those skilled in the art, the present invention can be implemented in a form in which various changes, modifications, improvements, and the like are made.
It goes without saying that all such embodiments are included in the scope of the present invention without departing from the spirit of the present invention.

[0054]

As is apparent from the above description, according to the method of the present invention, a specific thermal overload avoidance operation is performed in a situation where a thermal overload state has not yet been reached. The occurrence of a thermal overload state is prevented beforehand, and in particular, by performing the operation of avoiding the thermal overload, the molding material is left inside the molding die or the heating cylinder in the injection device. Since there is no interruption or the like, and since the mold is not interrupted in the mold open state, adverse effects on the molding cycle are reduced or avoided as much as possible, and good moldability is advantageously achieved. It can be maintained.

Further, according to the electric injection molding machine having the structure according to the present invention, the method of the present invention can be advantageously carried out, and the first, second, and third superconductors can be operated by the operation selecting means. By selectively adopting the load avoiding operation, an overload avoiding operation that is more highly responsive to molding conditions and the like can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a hardware configuration of an electric injection molding machine as one embodiment of the present invention.

FIG. 2 is a schematic view showing a specific configuration example of an injection molding machine main body constituting the electric injection molding machine shown in FIG.

FIG. 3 is a flowchart illustrating an overload detection process for executing the overload avoidance method according to the present invention in the electric injection molding machine shown in FIG. 1;

FIG. 4 is a flowchart illustrating a plasticizing process control process for executing the overload avoidance method according to the present invention in the electric injection molding machine shown in FIG. 1;

FIG. 5 is a flowchart illustrating a molding cycle start process for executing the overload avoidance method according to the present invention in the electric injection molding machine shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Injection molding machine main body 12 Controller 14 Servo motor 16 Servo amplifier 18 Mold clamping device 20 Injection device 24 Fixed mold 26 Movable mold

Continued on the front page F term (reference) 4F206 AM08 AM09 AM19 AR08 AR11 AR16 JA07 JL02 JM01 JM02 JM04 JM05 JP15 JT01 JT05 JT32

Claims (5)

[Claims] 1. An injection device for measuring, injecting, and measuring a molding material.
In an electric injection molding machine in which holding pressure or the like is performed using at least one electric motor, a thermal load value of the electric motor and / or its driver is obtained at least at a time interval shorter than a molding cycle, When the thermal load value exceeds a preset reference value at a value smaller than the instantaneous current stop level, at least one of the following first, second and third overload avoiding operations is executed. A method for avoiding overload in an electric injection molding machine, characterized in that: Before the start of measuring the molding material for the next molding by the injection device, if the thermal load value exceeds the reference value,
The current molding cycle is completed by omitting the step of measuring the molding material for the next molding, and the molding cycle is interrupted after further closing the mold, while the thermal load value is measured during the measurement of the molding material for the next molding by the injection device. When the value exceeds the reference value, the measurement of the molding material for the next molding is stopped, and when the thermal load value exceeds the reference value after the measurement of the molding material for the next molding by the injection device. Is the first overload avoidance operation in which the current molding cycle is completed, the mold is closed, and the molding cycle is interrupted after the measured molding material is discharged out of the mold. A second overload avoidance operation for reducing at least one of the mold closing speed and the mold opening speed. Third overload avoidance operation that increases the delay time from completion of mold closing to start of injection of molding material. 2. The overload avoiding method in an electric injection molding machine according to claim 1, wherein said thermal load value is obtained by integrating a torque command value of said electric motor by said driver with time. 3. A method of measuring, injecting, and measuring a molding material by an injection device.
An electric injection molding machine configured to perform pressure holding or the like using at least one electric motor, wherein a thermal load value of the electric motor and / or its driver is obtained at least at a time interval shorter than a molding cycle. Load value detection means, and comparing the thermal load value obtained by the detection means with a reference value preset at a value smaller than the instantaneous current stop level, wherein the thermal load value exceeds the reference value. Alarming means for outputting a pre-overload alarm signal in the event of an overload, and, when the pre-overload alarm signal is output by the alarm issuing means, instructing a controller of the injection molding machine to execute an overload avoidance operation. Execution instruction means for issuing a signal; and an overload avoidance operation instructed by the execution instruction means to the controller of the injection molding machine. If the thermal load value exceeds the reference value before starting the measurement of the material, the current molding cycle is completed by omitting the step of measuring the molding material for the next molding, and the molding is performed after the mold is closed. While interrupting the cycle,
If the thermal load value exceeds the reference value during the measurement of the molding material for the next molding by the injection device, the measurement of the molding material for the next molding is stopped, and If the thermal load value exceeds the reference value after the molding material is measured, the current molding cycle is completed, the mold is closed, and the molding cycle is interrupted after discharging the measured molding material out of the mold. A first overload avoiding operation, (b) a second overload avoiding operation for reducing at least one of the mold closing speed and the mold opening speed, and (c) a delay time from completion of mold closing to start of injection of molding material. An electric injection molding machine, comprising: a third overload avoiding operation for increasing the pressure; and operation selecting means for selectively setting one or more of the operations. 4. The electric injection molding machine according to claim 3, further comprising first setting means for changing and setting the magnitude of the reference value in said alarm issuing means. 5. A second control device for changing and setting at least one of a speed reduction amount in the second overload avoiding operation and an increase amount of a delay time in the third overload avoiding operation. The electric injection molding machine according to claim 3 or 4, further comprising a setting means.