JPH0577299A - Detecting device for belt abnormality of electrically-driven injection molding machine - Google Patents

Abstract

PURPOSE:To make it possible to exactly detect if there is any abnormality of belt or not without performing complicated inspection. CONSTITUTION:A pressure controller 11 outputs a pressure control signal to a servo amplifier 10 based on a dwelling set value and actual dwelling pressure. A comparator 12 compares the magnitude relationship between the dwelling set value and actual dwelling pressure and if the actual dwelling pressure is not in a range, the comparator outputs a timer count signal to an abnormality detection timer 13. The timer 13 outputs a time-up signal to an output unit 15 when the timer count signal reaches an abnormal pressure detecting time set value. A waveform monitor controller 14 displays a monitor waveform on CRT 16 based on a fuctuation width set value and the actual dwelling pressure. The output unit 15 causes an alarm device 17 to generate a belt abnormality alarm based on the time-up signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt abnormality detecting device for an electric injection molding machine, and more particularly to an electric injection molding capable of accurately detecting the presence or absence of abnormality of a belt connecting an injection screw drive mechanism and a drive motor. The present invention relates to a belt abnormality detection device.

[0002]

2. Description of the Related Art Conventionally, in an electric injection molding machine, an injection screw drive mechanism using a linear motion mechanism consisting of a ball screw and a ball nut screwed with the ball screw is driven by a servo motor via a belt. The injection screw is moved in the axial direction, and the molten injection material plasticized in the heating cylinder is injected into the mold by the injection nozzle to obtain a molded product. In the injection process, the control unit is operated and controlled and driven based on the set value determined by the injection condition, and the movement of the injection screw is controlled. In this case, after the molten injection material is filled in the mold cavity (after the completion of the filling step), in the pressure holding step for compensating for the shrinkage caused by the cooling and solidification of the molten injection material until the gate sealing is completed, The pressure control is performed by feeding back the detected actual holding pressure to the control unit.

[0003]

However, in the conventional electric injection molding machine as described above, the feedback control of the pressure is performed especially in the pressure holding step, so that the injection screw drive mechanism and the drive motor are connected. When the belt stretches, it is impossible to control the injection screw stably, so there is a problem that the injection molded product will be defective, and abnormal vibration occurs with the belt stretch. However, there is a problem that it leads to damage of each machine part such as the injection screw drive mechanism. Therefore, in order to prevent the above-mentioned problems, the belt is regularly checked for tension by measuring the belt elongation with a tension meter or by removing the belt from the injection molding machine and measuring the belt length. However, there is a problem that the inspection work is extremely complicated.

The present invention solves the above-mentioned problems, and it is possible to accurately detect the presence or absence of an abnormality in the belt connecting the injection screw drive mechanism and the servomotor, without performing a complicated inspection as in the prior art. It is an object of the present invention to provide a belt abnormality detection device for an electric injection molding machine.

[0005]

According to the present invention, there is provided an injection screw, an injection motor for driving the injection screw, a belt for transmitting a driving force of the injection motor to a drive mechanism for the injection screw, and a holding pressure. In an electric injection molding machine equipped with a pressure sensor for detecting, a warning means for warning that the belt has an abnormality, a setting means for setting a holding pressure setting range having a predetermined fluctuation range, and the pressure Comparison means for comparing and judging whether the actual holding pressure output from the sensor is within the holding pressure setting range set by the setting means or outside the holding pressure setting range, and the actual holding pressure is set by the comparing means. If it is determined that the belt is out of the range, the alarm means is provided to issue an alarm indicating that the belt has an abnormality.

[0006]

According to the present invention, after the start of injection, it is constantly monitored whether the actual holding pressure is within the holding pressure setting range or outside the holding pressure setting range, and when the actual holding pressure is outside the holding pressure setting range, A belt abnormality is issued from the alarm means.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing an injection screw drive mechanism and a control system of an injection molding machine of this embodiment. The injection screw drive mechanism is a heating cylinder 1 for heating and melting an injection material supplied from a hopper, and the heating cylinder 1 An injection screw 2 that is disposed inside the heating cylinder 1 and moves forward in the axial direction of the heating cylinder 1 to inject the molten injection material from an injection nozzle; and a holding pressure / back pressure that is provided at the rear end of the injection screw 2. Pressure sensor (load cell) 3 for detecting the pressure, a pair of ball screws 4.4 arranged in the injection screw drive mechanism, and the ball screws 4.4.
Ball nuts 4a, 4a which are screwed together to convert the rotational movement into linear movement, a drive plate 4b fixed to the ball nuts 4a, 4a for supporting the injection screw 2 via the pressure sensor 3, and a ball screw portion. A pulley 5 mounted on the end of the injection screw, an injection servomotor 6 for driving the injection screw 2, and a belt 7 wound between the output shaft of the injection servomotor 6 and the pulley 5. It is configured to have. Then, the injection servomotor 6 is driven in the forward direction and the reverse direction to perform an injection process and a supply / non-rotation backward process in the injection molding machine.

On the other hand, the control system of the injection molding machine includes a setting device 8 including a holding pressure set value device 8a, a holding pressure fluctuation width setting device 8b, and an abnormal pressure detection time setting device 8c, a pressure controller 11, and a comparator. 1
2. The control device 9 includes an abnormal pressure detection timer 13, a waveform monitor controller 14, an output unit 15, and a servo amplifier 10. The holding pressure setting device 8a sets the holding pressure stepwise at time intervals, and the set value S1 thereof is input to the pressure controller 11. The fluctuation range setting device 8b sets an upper limit value and a lower limit value of the allowable fluctuation range value with respect to the holding pressure setting value S1 in the holding pressure setting device 8a. It is adapted to be inputted to the comparator 12 and the waveform monitor controller 14. The pressure controller 11 outputs a pressure control signal to the servo amplifier 10 based on the holding pressure set value set by the setting device 8 and the actual holding pressure output by the pressure sensor 3. Further, the comparator 12 is a setting device 8
The holding pressure set value set from is compared with the actual holding pressure output from the pressure sensor 3, and the actual holding pressure is within a predetermined range (lower limit pressure setting value ≧ actual holding pressure ≧ upper limit pressure setting value). If there is not, a timer count signal is output to the abnormality detection timer 13. Further, the abnormal pressure detection timer 13 outputs a time-up signal to the output unit 15 when the timer count signal output from the comparator 12 reaches the abnormal pressure detection time set value set by the setter 8. It has become. Further, the waveform monitor controller 14 constantly monitors the pressure control value during the pressure holding control, and the fluctuation range set value set by the setter 8 and the actual holding pressure output from the pressure sensor 3 are set. Based on the monitor waveform (see, for example, FIG.
(See FIG. 5) is displayed on the CRT 16. Further, the output unit 15 is configured to generate an alarm from the alarm device 17 that the belt 7 has an abnormality based on the time-up signal output from the abnormality detection timer 13. The servo amplifier 10 subtracts the actual holding pressure output from the pressure sensor 3 from the pressure control signal output from the pressure controller 11, amplifies the subtraction result, and outputs it as a command value to the injection servo motor 6. It is supposed to do.

Here, the relationship between the holding pressure set value set by the setter 8 and the time (the holding pressure set value changes with time) is as shown in FIG. 2, and the holding pressure set value and the upper limit alarm setting width The relationship between (the upper limit setting width as the alarm output reference) and the lower limit alarm setting width (the lower limit setting width as the alarm output reference) is as shown in FIG. The relationship between the pressure set value when the belt 7 is normal and the actual pressure value / upper limit alarm setting width / lower limit alarm setting width is as shown in FIG. 4, and the pressure set value and the actual pressure value when the belt 7 is abnormal. The relationship between the upper limit alarm setting width and the lower limit alarm setting width is as shown in FIG.

That is, in the injection molding machine of the present embodiment, the holding pressure that can be set to have a width above and below the holding pressure control setting value (holding pressure setting value in FIG. 3) during holding pressure control. Whether the pressure control value is within the holding pressure control detection width is provided by setting the control detection width (upper limit alarm setting width / lower limit alarm setting width in FIG. 3) and constantly monitoring the pressure control value during the pressure holding control. It is designed to detect And the belt 7
If the expansion of the pressure does not affect the pressure control, the pressure control is performed within the pressure control detection width (upper limit alarm setting width / lower limit alarm setting width in Fig. 4) so as to follow the pressure maintaining control command value. It has become. On the other hand, when the belt 7 is stretched, there is a time lag between the rotation of the injection servomotor 6 and the operation of the injection screw 2, so that the holding pressure control becomes unstable when the vibration occurs. As a result of the pressure control value (actual pressure value in FIG. 5) deviating from the pressure holding control detection width (upper limit alarm setting width in FIG. 5), an abnormal state of the belt 7 is detected. In this case, when the abnormal pressure detection timer 13 keeps the unstable state for a set time (abnormal pressure detection time set value) or more, it is determined that the belt 7 is stretched.

Next, the belt abnormality detection processing in the injection molding machine of the present embodiment having the above-mentioned configuration will be described with reference to FIG. After starting the injection operation by the injection screw 2 of the injection molding machine, the pressure controller 11 of the control device 9 determines whether or not the pressure is being held based on the presence or absence of the output of the pressure sensor 3 (step S1). If it is determined that the pressure is not in the middle, the belt abnormality detection processing is ended, while if it is determined that the pressure is being maintained, the actual pressure holding fed back from the pressure sensor 3 is read (step S2). Then, the comparator 12 of the controller 9
Determines whether the actual holding pressure is within the upper limit pressure setting value (step S3). If it is determined that the actual holding pressure is not within the upper limit pressure setting value, the process proceeds to step S6, which will be described later. When it is determined that the actual holding pressure is within the upper limit pressure setting value, it is determined whether the actual holding pressure is within the lower limit pressure setting value (step S4). If the comparator 12 determines that the actual holding pressure is within the lower limit pressure setting value, it is determined that the belt 7 has no abnormality, and after resetting the abnormal pressure detection timer 13 (step S5), the process of step S1 is performed. On the other hand, if it is determined that the actual holding pressure is not within the lower limit pressure setting value, the process proceeds to step S6 described later. If the comparator 12 determines in step S3 that the actual holding pressure is not within the upper limit pressure setting value, or in step S4 that the actual holding pressure is not within the lower limit pressure setting value, the belt 7 is abnormal. It is determined that there is, and the abnormality detection timer 13 of the control device 9 starts counting time (step S6). After the start of the time count, the abnormality detection timer 13 determines whether or not the time count has reached the abnormal pressure detection time set value set by the setter 8 (step S7). This abnormal pressure detection timer is reset when the read value of the feedback pressure falls within the upper limit pressure setting value and the lower limit pressure setting value before time up. Abnormality detection timer 13
When it is determined that the time measurement time has not reached the abnormal pressure detection time set value, the process returns to step S1 to determine again whether the pressure is being held, while the time measurement time has reached the abnormal pressure detection time set value. If it is determined that the time-out signal is output to the output unit 15. As a result, the output unit 15 causes the alarm 1
An alarm indicating that there is an abnormality in the belt 7 is output from 7 (step S8). The belt abnormality detection process is completed by the series of processes described above.

[0012]

As described above, according to the present invention, the effects of the following items can be obtained. By utilizing the phenomenon that stable pressure holding control becomes impossible when the belt that transmits the driving force of the injection motor to the drive mechanism of the injection screw stretches, the stability of the pressure holding control is constantly monitored. It is possible to accurately detect whether the belt is stretched, that is, whether the belt is abnormal. As described above, since it is possible to prevent defects such as defective injection-molded products due to belt elongation and damage to mechanical parts due to abnormal vibration, it is possible to achieve preventive maintenance of the injection molding machine. It will be possible.

[Brief description of drawings]

FIG. 1 is a block diagram of an injection screw mechanism and a control system of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is a diagram showing a holding pressure set value according to the present embodiment.

FIG. 3 is a diagram showing a relationship between a holding pressure setting value and an upper limit alarm setting width / lower limit alarm setting width in the present embodiment.

FIG. 4 is a diagram showing a relationship between a pressure setting value and an actual pressure value / upper limit alarm setting width / lower limit alarm setting width when the belt is normal in the present embodiment.

FIG. 5 is a diagram showing a relationship between a pressure setting value and an actual pressure value / upper limit alarm setting width / lower limit alarm setting width when a belt is abnormal in the present embodiment.

FIG. 6 is a flowchart of belt abnormality detection processing of the present embodiment.

[Explanation of symbols]

 1 Heating Cylinder 2 Injection Screw 3 Pressure Sensor 4 Ball Screw (Drive Mechanism) 5 Pulley 6 Injection Servo Motor (Injection Motor) 7 Belt 8 Setting Device (Setting Means) 9 Controller 10 Servo Amplifier 11 Pressure Controller 12 Comparator ( Comparison means) 13 Abnormality detection timer (warning control means) 14 Waveform monitor controller 15 Output section 16 CRT 17 Alarm device (warning means)

Claims (1)

[Claims] 1. An injection screw, an injection motor for driving the injection screw, a belt for transmitting a driving force of the injection motor to a drive mechanism for the injection screw, and a pressure sensor for detecting a holding pressure. In the electric injection molding machine, the warning means for warning that there is an abnormality in the belt, the setting means for setting a holding pressure setting range having a predetermined fluctuation range, and the actual holding pressure output from the pressure sensor And a comparing means for comparing and determining whether the holding pressure is within the holding pressure setting range set by the setting means or outside the holding pressure setting range, and the comparison means determines that the actual holding pressure is outside the holding pressure setting range. And an alarm control unit for issuing an alarm from the alarm unit that the belt has an abnormality, a belt abnormality detection device for an electric injection molding machine.