JPH0751306B2 - Motor protection device for 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 a motor protection device suitable for overload protection of a servomotor of an electric injection molding machine.

[0002]

2. Description of the Related Art Conventionally, in an electric injection molding machine,
Overload protection of electric servomotors has been performed by monitoring the load factor (electronic thermal monitoring) within the servo amplifier. FIG. 5 is a block diagram of an overload protection device for an electric servomotor in a conventional electric injection molding machine.
The sequence controller unit 1 receives the speed command V from the command unit 3 in accordance with the sequence input from the numeric keypad 2 or the like.
Output C. This speed command VC is supplied to the amplifier 5 in the servo amplifier 4 and supplied to the electric motor 6 as a predetermined current value. Power is externally supplied to the amplifier 5. The electric motor 6 is provided with an encoder (not shown), and the encoder supplies an output proportional to the actual speed V of the electric motor 6 to the servo amplifier 4.
In the servo amplifier 4, the output from the encoder is the speed command V
Control the electric motor to reach the value of C.

In the control system described above, the servo amplifier 4
Is provided with an arithmetic unit 7, which monitors the output value (current value) of the amplifier 5. Electric motor 6
When an overload is applied to, the abnormality is detected by utilizing the fact that the output value of the amplifier 5 becomes large. In the case of overload, the arithmetic unit 7 stops the output of the amplifier 5 and supplies the alarm signal ARM to the sequence controller 1. The sequence controller 1 sends a warning message to the CRT 8 according to the alarm signal ARM.
Is displayed or a warning sound is generated.

[0004]

By the way, during the speed control, the above-mentioned load factor of the electric motor 6 may exceed 100% not only during an abnormal condition but also during a gear shift of 100% or more. In this case, it is not necessary to stop the electric motor. Further, generally, the allowable overload rate differs depending on the control in which process.

For example, FIGS. 6 (a) and 6 (b) are time charts showing the output of each part in the pressure-holding control step. In each figure, the speed V and the output current (percentage) of the electric motor are shown in order from the top of the drawing. ) Is shown. In the speed control process, as shown in FIG. 6A, P1 at start-up and P2 at speed change
And at the time of stop P3, the output current of the electric motor is 100
%, Otherwise the load factor is 100%.
If not below, it is considered to be a mechanical abnormality. Therefore, when starting P1, shifting P2 and stopping P3,
It is not necessary to stop even if it exceeds 00%. On the other hand, except for P1 at start, P2 at shift, and P3 at stop,
When it exceeds 100%, it is necessary to stop immediately. FIG. 6B is a diagram showing an example in the case of an abnormal stop, and is an example of stopping by a mechanical collision at the abnormal stop point P4. At the abnormal stop point P4, the output current of the electric motor exceeds 100% and reaches 300%.

FIG. 7 is a time chart showing the output of each part in the pressure-holding control step, showing pressure and output current (percentage) of the electric motor in order from the top of the drawing. In the figure, in the pressure-holding control step, even if the output current of the electric motor is 100% or more, it may be normal depending on the duration T1 or T2, so is it abnormal according to the duration of the overload? It is necessary to judge whether or not.

However, in the conventional overload protection device for the electric servomotor, when the overload is detected, the output of the amplifier 5 is cut off, so that the electric motor 6 is mechanically stopped. In order to restore the electric motor 6, the power supply of the servo amplifier 4 has to be reset. For this reason, the work for restoration becomes complicated and takes time. In addition, it is difficult to know when the electric motor 6 will stop, which is a serious problem in automatic operation.

The present invention has been made in view of the above circumstances, and the allowable load factor of the motor can be set according to the process.
Moreover, it is an object of the present invention to provide an electric motor protection device that can monitor a load state and can protect the electric motor without completely stopping the electric motor.

[0009]

In order to solve the above-mentioned problems, in the present invention, load detecting means for detecting a load factor of an electric motor for driving a driven member such as an injection screw of an injection molding machine, An allowable load factor is set according to the process in which the electric motor is used, the allowable load factor is compared with the load factor detected by the load detection means, and the load of the electric motor is determined based on the comparison result. The first control means for monitoring the state and the absolute permissible load factor of the electric motor are set, the absolute permissible load factor is compared with the load factor detected by the load detecting means, and the load factor is A second control means for stopping the operation of the electric motor when the absolute allowable load factor is exceeded.

[0010]

According to the present invention, the load factor of the electric motor is detected by the load detecting unit, and the load factor detected by the load detecting unit and the preset allowable load factor according to the process in which the electric motor is used. Are compared by the first control means, and the load state of the electric motor is monitored based on the comparison result. On the other hand, the preset absolute allowable load factor of the electric motor and the load factor detected by the load detecting unit are compared by the second control unit, and when the load factor exceeds the absolute allowable load factor, Stop the operation of the electric motor.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In this figure, constituent elements having the same functions as those of the conventional servomotor overload protection device shown in FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted. The sequence controller 10 includes a command unit 11 and a calculation unit 12. The command unit 11 outputs the speed command value VC to the servo amplifier 13 according to the speed data input from the numeric keypad. Further, the arithmetic unit 12 detects the motor current MA to the electric motor 6 output from the servo amplifier 13, performs a predetermined arithmetic operation based on the motor current MA to calculate a load factor and the like, and supplies it to the CRT 8. .

The servo amplifier 13 is composed of an amplifier 14 and an arithmetic unit 15. The amplifier 14 supplies the motor current MA to the electric motor 6 according to the speed command value VC. A current detector 16 is provided at the output terminal of the amplifier 14, and the current detector 16 supplies the detected motor current MA to the arithmetic unit 12 of the sequence controller 10 and the arithmetic unit 15 of the servo amplifier 13. . Computing unit 1
Reference numeral 5 controls the output of the amplifier 14 so as not to be overloaded according to the motor current MA, and outputs an alarm signal ARM to the sequence controller 10 when overloaded. Further, the electric motor 6 is provided with the encoder 17 as in the conventional case,
The rotation speed V is measured by the encoder 17. The rotation speed V is supplied to the servo amplifier 13.

Next, the structure of the above-mentioned electric motor protection device applied to an electric injection molding machine will be described in detail with reference to FIG. In the figure, an electric injection molding machine 20
Is composed of a drive unit 21, an injection screw 22, and a heating cylinder 23. The electric motor 6 is attached to the drive unit 21, and rotation of the electric motor 6 is controlled by the belt 25.
Is transmitted to the pulleys 26a, 26b and 26c. Further, the ball screws 27, 27 are respectively the pulley 26
The pulleys 26a and 26b are fitted around the shafts a and 26b about the axis, and the rotation of the pulleys 26a and 26b is transmitted to the ball nuts 28 and 28. The ball nuts 28, 28 are screwed into the ball screws 27, 27, respectively.
Converts the rotational motion of to linear motion. Next, the injection screw 22 is provided with one end at the center of the connecting portion of the ball nuts 28, 28 and is inserted into the heating cylinder 23, and is illustrated in accordance with the linear movement of the ball nuts 28, 28. It is designed to move back and forth in the direction of arrow A and to rotate about the axis.

The heating cylinder 23 is heated to a predetermined temperature by a heater (not shown) and has an injection hole 30 at its tip and a material supply section 31 at its side surface. Has been. The material put in the material supply unit 31 is introduced into the heating cylinder 23 and melted, and the injection screw 22 is rotated to rotate the injection hole 3
It is transported to the 0 side. The material conveyed to the tip of the heating cylinder 23 is pressed by the linear movement of the injection screw 22 in the direction of the arrow A, and the mold 4 is pushed through the injection hole 30.
It is designed to be ejected to 0.

Next, the ten-key input section 10a is a buffer for allocating the data input by the ten-key 2 to the command section 11 and the arithmetic section 12. The command unit 11 of the sequence controller 10 is composed of a speed command unit 11a and a pressure command unit 11b, and its output end is
A switch SW1 for allocating which output is output to the servo amplifier 13 is provided. Speed command unit 11
a outputs the data supplied from the ten-key input unit 10a as speed command data VC for speed control of the electric motor 6. Further, the pressure command unit 11b is the ten-key input unit 10a.
The data supplied from is output as pressure command data PC for pressure control of the electric motor 6. The switch SW1
Operates under the control of the process control unit 10b, selects the speed command unit 11a side when controlling the speed of the electric motor 6, and selects the speed command unit 11a side when controlling the pressure.
Select.

Next, the computing unit 12 of the system controller 10 includes a motor load factor setting unit 12a for the speed process, a motor load factor comparing unit 12b for the speed process, a motor load factor comparing unit 12c for the pressure process, and a pressure process. Motor load factor setting unit 12d for time, motor overload allowable time setting unit 1 for pressure process
2e, motor load factor calculator 12f, OR gate 12g,
It is composed of switches SW2 and SW3. The motor load factor setting value VE during the speed step of the electric motor 6 supplied via the ten-key input section 10a is set in the speed setting section 12a, and the motor load during the speed step is set. The rate setting value VE is supplied to the motor load rate comparison unit 12b during the speed process. The motor load factor set value VE during the speed process is set to a value, for example, where the load factor slightly exceeds 100%. The motor load factor comparison unit 12b in the speed process compares the motor load factor set value VE in the speed process with the motor load factor CT1 calculated by the motor load factor calculation unit 12f (details will be described later).
It is determined whether or not the electric motor 6 is overloaded, and if it is exceeded, a signal of "1" is supplied to one input end of the OR gate 12g.

Further, the motor load factor setting unit 1 during the pressure process
In 2d, the motor load factor set value PE during the pressure step supplied via the ten-key input unit 10a is set. Further, the motor overload permissible time setting section 12e for the pressure step is set with the motor overload permissible time PT for the pressure step supplied via the ten-key input section 10a. The motor load factor comparison unit 12c at the time of the pressure process determines the motor load factor set value PE at the time of the pressure process.
And the motor load factor calculated by the motor load factor calculator 12f are compared, and when it is determined that the motor is overloaded,
By comparing the overload duration time with the motor overload allowable time PT during the pressure step, it is determined whether or not an abnormality has occurred, and the overload duration time is calculated as the motor overload allowable time PT during the pressure step. If it exceeds, it is determined that an abnormality has occurred and a signal of "1" is supplied to the other input terminal of the OR gate 12g.

Motor load factor comparison unit 12 during the above speed process
A switch SW2 is provided at the input end of the motor load factor comparison unit 12c during the pressure step b and the pressure process for allocating the output of the motor load factor calculation unit 12f. The switch SW2 operates under the control of the process control unit 10b. When controlling the speed of the electric motor 6, the switch SW2 selects the motor load factor comparison unit 12b side during the speed process, and when controlling the pressure, the pressure SW2 is selected. The comparison unit 12c side is selected.

The OR gate 12g sets the output to "1" when one of the signals supplied to the input terminal becomes "1", and the switch SW3 and the CRT control section 10c.
Supply to. The switch SW3 is normally on, and when the signal of "1" is supplied, it is turned off. Further, the OR gate 1 is included in the CRT controller 10c.
In addition to the 2 g output signal, the alarm signal ARM from the servo amplifier 13 is supplied, and when any of the signals is supplied, a message corresponding to the signal is supplied to the CRT 8.

Next, the arithmetic unit 15 of the servo amplifier 13
The calculation unit 15a, the comparison unit 15b, and the setting unit 15c are included. The calculation unit 15a calculates the count value CT2 based on the overload protection characteristic diagram (one example) shown in FIG. 3 according to the monitor current MA detected by the current detector 16, and supplies this to the comparison unit 15b. . Also, the setting unit 1
In 5c, a set value CT3 corresponding to a load factor of 300% is set in advance for overload detection. The comparison unit 15b uses the count value CT2 and the set value CT.
3 and the count value CT2 exceeds the set value CT3, the alarm signal ARM is output to the switch SW4 and the CRT controller 10c described above. Switch SW4
Is normally on, and when an output signal is supplied from the comparison section 15b, it is turned off and cuts off the motor current MA supplied from the amplification section 14 to the electric motor 6.

Next, the operation of the above-mentioned configuration will be described with reference to FIG.
This will be described with reference to the flowchart shown in FIG. When the electric injection molding machine 20 and the control device are turned on, the control device operates according to the flowchart shown in FIG. First, in the case of a speed process, the process management unit 10b
The switch SW1 is turned on to the speed command unit 11a side, and the switch SW2 is turned to the motor load factor comparison unit 12b side during the speed process. As a result, the data input from the numeric keypad 2 is supplied from the speed command unit 11a as the speed command value VC to the amplification unit 14 of the servo amplifier 13 via the switch SW3 (steps S1 and S2). Amplifier 1
4 outputs a motor current MA corresponding to the speed command value VC to the electric motor 6 via the switch SW4. The electric motor 6 is driven according to the motor current MA. The injection screw 2 is driven by driving the electric motor 6.
2 operates, and the material is injected from the injection hole 30 at the tip of the heating cylinder 23.

The motor current MA output by the amplifier 14 is
The current is detected by the current detector 16 and supplied as a monitor current MA to the motor load factor calculation unit 12f of the sequence controller 10 and the calculation unit 15a of the servo amplifier 13. The motor load factor calculation unit 12f determines the motor load factor CT1.
Is calculated (step S3). Motor load factor calculator 12
The motor load factor CT1 output by f is supplied to the motor load factor comparison unit 12b during the speed process via the switch SW2, and the motor load factor comparison unit 12b during the speed process and the motor load factor CT1 and the speed time setting. The motor load factor set value VE set in the section 12a is compared (step S
4, S5). As a result, when the motor load factor set value VE is larger than the motor load factor CT1, it is determined that the motor is not overloaded yet, and the operation is continued without stopping the electric motor 6 (step S6). After that, the monitor current MA detected by the current detector 16 is converted into the motor load factor CT1 and the motor load factor CT1 and the motor load factor set value V are converted.
The operation is continued while monitoring whether or not an overload has occurred by comparing with E (steps S3 to S6). On the other hand, also in the servo amplifier 13, the comparison unit 15b compares the set value CT3 with the count value CT2 output by the count calculation unit 15a to monitor the load factor of the electric motor 6.

During operation of the above speed process, the motor load factor comparison unit 12b of the sequence controller 10 during the speed process.
, The motor load factor CT1 is the motor load factor set value V
When it becomes larger than E, it is judged that an abnormality has occurred (step S5), and the output of the OR gate 12g becomes "1". Therefore, the switch SW3 is turned off (step S
7) And the message that an anomaly was detected is CR
It is displayed at T8 (step S8). Speed command value VC
Is not supplied to the servo amplifier 13 when the switch SW3 is turned off. However, since the electric motor 6 is driven by the servo amplifier 13, it does not stop immediately as a result of the above abnormality. Further, the motor load factor CT1 exceeds the motor load factor set value VE, and further, in the servo amplifier 13, the count value C
When T2 exceeds the set value CT3, the switch SW4 is turned off by the alarm signal ARM output from the comparison unit 15b, and the motor current MA to the electric motor 6 is cut off.
As a result, the electric motor 6 stops completely.

On the other hand, in the case of the pressure process, the process control section 1
By 0b, the switch SW1 is turned on to the pressure command unit 11b side, and the switch SW2 is turned to the motor load factor comparison unit 12c side during the pressure process. As a result, the data input from the numeric keypad 2 is supplied from the pressure command unit 11b as the pressure command value PC to the amplification unit 14 of the servo amplifier 13 via the switch SW3 (steps S1 and S).
9). The amplifier 14 outputs the motor current MA corresponding to the pressure command value PC to the electric motor 6 via the switch SW4. The electric motor 6 is driven according to the motor current MA. By driving the electric motor 6,
The injection screw 22 injects the material at a predetermined pressure through the injection hole 30 at the tip of the heating cylinder 23.

The motor current MA output by the amplifier 14 is
The sequence controller 10 and the servo amplifier 1 are detected as the monitor current MA by the current detector 16.
3 is supplied to the motor load factor calculation units 12f and 15a.
The motor load factor calculator 12f calculates the load factor CT1 of the motor (step S3). The motor load factor CT1 output from the motor load factor calculation unit 12f is supplied to the motor load factor comparison unit 12c during the pressure process via the switch SW2 (step S4). Then, the motor load factor comparison unit 12c during the pressure process compares the motor load factor CT1 with the motor load factor set value PE set in the motor load factor setting unit 12d during the pressure process (step S10). . As a result, the motor load factor set value PE is equal to the motor load factor CT1.
If it is larger, it is determined that the overload has not yet occurred, and the motor overload allowable time setting unit 12e during the pressure process is set.
After resetting (step S11), the operation is continued without stopping the electric motor 6 (step S6). After that,
The monitor current MA detected by the current detector 16 is converted into a motor load factor CT1, and the motor load factor CT1 and the motor load factor set value PE are compared to monitor whether or not an overload has occurred, thereby performing the operation. Continue (Step S
3 to S6). On the other hand, also in the servo amplifier 13, the set value CT3 and the count calculation unit 15 are compared by the comparison unit 15b.
The count value CT2 output by a is compared and the load factor of the electric motor 6 is monitored.

During the operation of the pressure process, the motor load factor comparison unit 12c of the sequence controller 10 during the pressure process is performed.
, The motor load factor CT1 is the motor load factor set value P
When it becomes larger than E (step S10), first, counting is started (step S12). Then, the count value is compared with the motor overload allowable time PT of the motor overload allowable time setting unit 12e during the pressure step (step S1).
3) If the count value is smaller than the motor overload allowable time PT, it is determined that there is no abnormality, and the operation is continued without stopping the electric motor 6 (step S6). Thereafter, the monitor current MA detected by the current detector 16 is converted into the motor load factor CT1 and the motor load factor CT1 is compared with the motor load factor set value PE to monitor whether or not an overload has occurred. Continue driving (steps S3 ~ S
6).

On the other hand, during the operation of the pressure process, the motor load factor CT1 becomes larger than the motor load factor set value PE in the motor load factor comparison section 12c of the sequence controller 10 during the pressure process (step S10), and When the count value of the motor load factor comparison unit 12c during the pressure process is larger than the motor overload allowable time PT of the motor overload allowable time setting unit 12e during the pressure process, it is determined that an abnormality has occurred, The output of the OR gate 12g becomes "1". Therefore, the switch SW3 is turned off (step S7), and a message that an abnormality is detected is displayed on the CRT 8 (step S8). The pressure command value PC is not supplied to the servo amplifier 13 when the switch SW3 is turned off. However, since the electric motor 6 is driven by the servo amplifier 13, it does not stop immediately as a result of the above abnormality.
When the motor load factor CT1 exceeds the motor load factor set value PE and the count value CT2 exceeds the set value CT3 in the servo amplifier 13, the switch SW4 is turned off by the alarm signal ARM output from the comparison unit 15b. The motor current MA to the electric motor 6 is cut off. As a result, the electric motor 6 stops completely.

To summarize the above, the motor current output from the servo amplifier 13 is converted into a motor load factor CT1 and the motor load factor CT1 is compared with a preset set value to determine the electric motor 6 The motor current is also monitored by the sequence controller 10 (electronic thermal), and the operation of the injection molding machine is stopped by the sequence controller 10 before the servo amplifier 13 determines that it is overloaded, thereby protecting the electric motor 6 without stopping it. To do. Further, it is possible to issue a warning of the load factor in advance.

[0029]

As described above, according to the present invention, the load detecting means detects the load factor of the electric motor, and the load factor detected by the load detecting means and the preset electric motor are provided. The allowable load factor according to the process used is compared by the first control means, the load state of the electric motor is monitored based on the comparison result, while the preset absolute allowable value of the electric motor is determined. The load factor and the load factor detected by the load detecting unit are compared by the second control unit, and when the load factor exceeds the absolute allowable load factor, the operation of the electric motor is stopped. It is possible to set an allowable load factor according to the process to be performed, to monitor the load state, and to protect the electric motor according to the load state without completely stopping the electric motor. Cormorants advantages are obtained.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a configuration when the electric motor protection device of the embodiment is applied to an electric injection molding machine.

FIG. 3 is a protection characteristic diagram showing an operation duration time of an electric motor in an overload operation.

FIG. 4 is a flowchart for explaining the operation of the electric motor protection device according to the embodiment.

FIG. 5 is a block diagram showing a configuration of a conventional overload protection device for a servo electric motor.

FIG. 6A is a time chart showing a speed and a motor current in a speed control step, and FIG. 6B is a time chart showing an electric motor speed and a motor current for explaining when an abnormality occurs. .

FIG. 7 is a time chart showing pressure and motor current in a pressure control process.

[Explanation of symbols]

 10 Sequence Controller (First Control Means) 13 Servo Amplifier (Second Control Means) 16 Current Detection Means (Load Detection Means)

Claims (1)

[Claims] 1. A load detecting means for detecting a load factor of an electric motor for driving a driven member such as an injection screw of an injection molding machine, and an allowable load factor according to a process in which the electric motor is used. First control means for comparing the allowable load factor with the load factor detected by the load detecting means and monitoring the load state of the electric motor based on the comparison result; and an absolute allowable load of the electric motor. A rate is set, the absolute allowable load rate is compared with the load rate detected by the load detecting means, and when the load rate exceeds the absolute allowable load rate, the operation of the electric motor is stopped. And a control means of the motor protection device in an electric injection molding machine.