JP5179993B2 - Injection molding machine equipped with a method for determining the closed state of the backflow prevention valve of the injection molding machine and its discrimination function - Google Patents

Description

  The present invention relates to a method for determining a closed state of a backflow prevention valve when a screw provided with the backflow prevention valve of the injection molding machine is driven in an injection direction, and an injection molding machine provided with the determination function.

  2. Description of the Related Art Conventionally, an injection molding machine having an injection mechanism having a backflow prevention valve at a screw tip in order to prevent a backflow of resin at the time of injection, such as an inline screw type injection molding machine, has been used.

  FIG. 1 is an example of this check valve. A check ring 3 is disposed in a reduced diameter portion provided between the screw head 2 provided at the tip of the screw 1 and the main body portion of the screw 1 so as to be movable in the screw axial direction. On the main body side of the screw 1, there is provided a check sheet 4 that comes into contact with and close to the check ring 3 and closes the resin passage. Resin pellets supplied from behind the screw 1 into the cylinder 7 are shear heat generated by the rotation of the screw 1 during measurement, and a heater (not shown) provided outside the cylinder 7 in which the screw 1 is inserted. It is melted by the heat from. The molten resin raises the resin pressure behind the check ring 3 and generates a force pushing the check ring 3 forward. When the check ring 3 is pushed forward, the rear resin flows through the gap between the check ring 3 and the reduced diameter portion and flows into the front of the check ring 3 to increase the pressure in the cylinder in front of the screw head 2.

  When the pressure in front of the check ring 3 exceeds a predetermined pressure (back pressure), the screw 1 is pushed backward, and the pressure in front of the check ring 3 is reduced. Further, since the screw 1 further rotates, the pressure behind the check ring 3 becomes higher than the pressure ahead of the check ring 3, so that the continuously melted resin is sent to the front of the check ring 3. When the screw 1 moves backward to a predetermined amount, the screw rotation is stopped and the measurement is finished.

  Next, the injection process starts, but when the screw 1 moves forward to fill the resin, the resin pressure accumulated in front of the screw head 2 increases, so that the check ring 3 moves backward to come into close contact with the check sheet 4 and the resin passage. And the molten resin is prevented from flowing backward in the screw retracting direction due to the filling pressure.

  The backflow prevention valve at the time of injection is closed when the pressure of the front of the check ring 3 becomes higher than the pressure of the rear by the advance of the screw 1, but the back of the backflow prevention valve just before the injection is in the groove 6 between the flights 5. There is a problem that pressure is received from the accumulated resin in the compressed state, and the closing timing varies due to the pressure. Since the back flow of the resin occurs from the front to the back of the back flow prevention valve from the start of injection to the back flow prevention valve closing, the change in the closing timing causes a change in the injection volume for each cycle, and the molded product to be molded. Affects the quality of the. Therefore, a means for allowing the check ring 3 to be closed at a stable timing every cycle is considered, and a method for monitoring the timing at which the check ring 3 is actually closed has been proposed. Then, by detecting the screw position where the check ring 3 is closed and the time from the start of injection, setting of molding conditions such as the switching position from the injection speed control to the holding pressure control, the speed switching position, etc., and the quality determination of the molded product And other materials.

  For example, a pressure sensor for detecting the resin pressure in the cylinder is provided at a position behind the backflow prevention valve, and during the advancement of the screw, the closing of the backflow prevention valve is detected based on the pressure change detected by the pressure sensor. An invention is known in which the quality of a molded product is determined and the molding conditions are adjusted based on the detected backflow prevention valve closing position (see Patent Documents 1 and 2).

In addition, a conductive member is disposed so as to face the ring valve behind the ring valve of the backflow prevention valve, and by detecting the electrostatic capacitance between the ring valve and the conductive member, the position of the ring valve, That is, what detects when the resin flow path is closed by the ring valve is known (see Patent Document 3).
Further, Patent Document 4 does not detect the closing timing of the backflow prevention valve during injection, but detects rotational torque that acts on the screw during injection, and this detection torque causes damage to the backflow prevention valve. What detects an abnormality is described.

  Furthermore, when the injection is started with the screw being freely rotatable, the resin flows backward to rotate the screw, but the reverse flow prevention valve is closed, and when the reverse flow of the resin stops, the rotation of the screw stops. There is also known an invention in which the screw rotation stop is detected as the closing timing of the backflow prevention valve, and the injection speed switching position and the pressure switching position are corrected based on the detected backflow prevention valve closing position. (See Patent Document 5).

  Further, Patent Document 6 describes that when the servo lock is performed so that the screw does not rotate during the injection process, the peak occurrence time of the screw rotation angle can be regarded as the closing time of the check valve.

JP-A-4-53720 JP-A-4-201225 JP-A-3-92321 JP-A-1-168421 JP 2004-216808 A JP 2008-126533 A

  The techniques disclosed in Patent Documents 1 and 2 described above detect the pressure change in the cylinder to detect the closing of the check valve, and in this method, it is necessary to add a pressure sensor behind the check valve. There is. It is necessary to dispose the pressure sensor at least a distance greater than the maximum injection stroke from the tip of the cylinder. For this reason, a difference occurs in the distance between the backflow prevention valve and the pressure sensor due to the size of the injection stroke, resulting in a difference in detection accuracy.

  In addition, it is desirable that the inner wall surface of the cylinder has a smooth flow path without a step so as not to generate carbides due to resin stagnation. However, if a pressure sensor that directly contacts the resin is attached, the cylinder inner wall surface will become minute. It is inevitable that a stepped portion is generated, and adverse effects such as mixing of carbides due to resin retention into the molded product cannot be avoided.

  Further, in the pressure sensor that detects the pressure of the resin by indirectly detecting the distortion of the cylinder without directly contacting the resin, the detection accuracy is sacrificed. In addition, any type of pressure sensor is expensive and complicated to handle, and there are many problems that require regular maintenance and calibration.

  In the method of detecting the capacitance and detecting the closing timing of the ring valve as in the technique disclosed in Patent Document 3 described above, a conductive member for detecting the capacitance is arranged on the screw. At the center of the screw, a means for measuring the electrostatic capacity, such as machining a hole for passing the wiring and arranging a slip ring for taking out the measurement signal, must be added to the screw. There is a disadvantage that the configuration becomes complicated.

  The technique disclosed in Patent Document 5 detects that the rotation of the screw that has been freely rotated during injection is stopped, focusing on the component force Fθ in the screw rotation direction of the force of the resin that flows backward on the flight. It detects the closing of the check valve. According to the technique disclosed in Patent Document 5, it is possible to determine whether the backflow prevention valve is closed based on the stop of rotation. However, since the rotatable screw is rotated by the backflow resin, the screw rotation angle is maintained. Compared to the case, the back flow rate of the resin is greatly increased, and the resin filling amount by injection may be decreased, or the resin filling amount may be unstable.

  The technique disclosed in Patent Document 6 considers the peak occurrence time of the screw rotation angle as the closing time of the check valve. In actual injection molding, when the screw rotation angle does not change, the waveform of the screw rotation angle is trapezoidal and no peak occurs, or the backflow prevention valve closes even if the peak occurs in the screw rotation angle May not have. It has not been known in the past to determine the closed state of the check valve when such a rotation angle waveform is observed.

  Therefore, an object of the present invention is to provide an injection molding that can easily and more accurately determine the closed state of the backflow prevention valve provided in the screw without using a special device and without increasing the backflow of the resin. The present invention is to provide an injection molding machine having a backflow prevention valve closed state determination method and a backflow prevention valve closed state determination function.

In the invention according to claim 1 of the present application , the screw rotation angle is controlled to be maintained at a predetermined angle during the forward movement of the screw, the rotational angle of the screw is detected during the forward movement of the screw, and the change in the detected rotational angle is detected. An injection molding machine that displays a waveform on the screen of a display device with the passage of time during screw position or screw advance, and determines the closed state of the backflow prevention valve based on the waveform pattern displayed on the screen of the display device. It is a backflow prevention valve closed state discrimination method.

The invention according to claim 2 controls the screw rotation angle to be maintained at a predetermined angle during the forward movement of the screw, detects the rotational angle of the screw during the forward movement of the screw, and displays a change in the detected rotational angle. A waveform is displayed on the screen of the screw as time elapses during screw position or screw advance, and in the rotation angle waveform displayed on the screen of the display device, the rotation angle at a predetermined time point during screw advance is read, and the read rotation angle is When the angle is equal to or greater than the first predetermined angle, it is determined that the backflow prevention valve has not been closed by a predetermined time, and when the read rotation angle is smaller than the first predetermined angle, the backflow prevention valve has been closed by the predetermined time This is a method for determining the closed state of the backflow prevention valve of the injection molding machine.

  In the invention according to claim 3, the predetermined time point is a time point when the screw has been advanced, a time point when the injection speed is switched, a time point when the speed control is switched to the pressure control, or a time point when the screw is advanced by the movable stroke of the check valve. The backflow prevention valve closed state determination method for an injection molding machine according to claim 2, wherein:

The invention according to claim 4 controls the screw rotation angle to be maintained at a predetermined angle during the forward movement of the screw, detects the rotational angle of the screw during the forward movement of the screw, and displays a change in the detected rotational angle. A waveform is displayed on the screen of the screw position or with the lapse of time during the screw advance, and in the rotation angle waveform displayed on the screen of the display device, the detected rotation angle is shown in all sections from the start of the screw advance to the completion. When the second predetermined angle is not exceeded, the backflow prevention valve closed state determination method of the injection molding machine is configured to determine that the backflow prevention valve is closed at the start of screw advancement.

The invention according to claim 5 controls the screw rotation angle to be maintained at a predetermined angle during the forward movement of the screw, detects the rotational angle of the screw during the forward movement of the screw, and displays a change in the detected rotational angle. A waveform is displayed on the screen of the screw position or with the lapse of time during the screw advance, and in the rotation angle waveform displayed on the screen of the display device, the detected rotation angle is shown in all sections from the start of the screw advance to the completion. When the third predetermined angle is exceeded, the backflow prevention valve closed state determination method of the injection molding machine is configured to determine that the backflow prevention valve is closed abnormally.

According to a sixth aspect of the present invention, there is provided a control loop for maintaining a screw rotation angle at a predetermined angle during screw advancement, a rotation angle detection means for detecting a screw rotation angle during the screw advancement, and a predetermined time point during screw advancement. When the rotation angle is detected, and when the detected rotation angle is equal to or greater than the first predetermined angle, it is determined that the check valve has not been closed by the predetermined time, and the read rotation angle is smaller than the first predetermined angle Is an injection molding machine equipped with a check function for determining the closed state of the backflow prevention valve, characterized in that the backflow prevention valve is provided with a discriminating means for discriminating that the backflow prevention valve is closed by a predetermined time.

According to a seventh aspect of the invention, the predetermined time point is any of a screw advance completion time point, an injection speed switching time point, a time point when switching from speed control to pressure control, or a time point when the screw is advanced by the movable stroke of the backflow prevention valve. The injection molding machine having a backflow prevention valve closed state determination function according to claim 6 , wherein the time point is at one time point.

According to an eighth aspect of the present invention, there is provided a control loop for maintaining a screw rotation angle at a predetermined angle during screw advancement, a rotation angle detection means for detecting a screw rotation angle during the screw advancement, and a screw advancement start to completion. The comparison means for sequentially comparing the detected rotation angle and the second predetermined angle, and the detected rotation angle does not exceed the second predetermined angle in all sections from the start of screw advance to completion Is an injection molding machine having a check function for determining a closed backflow prevention valve, characterized in that the check valve is provided with a determining means for determining that the check valve is closed at the start of screw advancement.

According to a ninth aspect of the present invention, there is provided a control loop for maintaining a screw rotation angle at a predetermined angle during screw advancement, a rotation angle detecting means for detecting a screw rotation angle during the screw advancement, and a screw advancement start to completion. Comparing means for sequentially comparing the detected rotation angle and the third predetermined angle in all the sections, and when the detected rotation angle exceeds the third predetermined angle, the check valve is abnormally closed. An injection molding machine having a check function for determining a closed state of a backflow prevention valve provided with a determining means for determining that there is a valve.

The invention according to claim 1 0, check valve closure according to any one of claims 6-9, characterized in that to display the closed state of the check valve which is determined by said determination means on a display device An injection molding machine having a state discrimination function.

The invention according to claim 1 1, according to any one of claims 6-9, characterized in that performing the quality determination of the molded article based on the closed state of the check valve which is determined by said determining means It is an injection molding machine provided with a backflow prevention valve closed state discrimination function.

Invention, the discriminating means check valve according to any one of claims 6-9, characterized in that outputs an alarm based on the closed state of the check valve which is determined by according to claim 1 2 An injection molding machine having a closed state discrimination function.

According to the present invention, the backflow prevention of the injection molding machine can easily and more accurately determine the closed state of the backflow prevention valve provided in the screw without using a special device and without increasing the backflow of the resin. An injection molding machine provided with a valve closed state determining method and a backflow prevention valve closed state determining function can be provided.
Using the fact that the waveform of the rotational force applied to the screw when the screw moves forward changes depending on the closed state of the backflow prevention valve, this waveform is displayed on the screen of the display device, and the backflow prevention valve is closed by this display waveform pattern Can be easily grasped.

First, the principle of the method for determining the closed state of the check valve of the present invention will be described.
The present invention discriminates the closed state of the backflow prevention valve provided in the screw by using the change waveform of the rotation angle of the screw that is rotated by the rotational force acting on the screw at the time of injection.

  After completion of the metering and before the start of injection, the axial movement of the screw 1 and the screw rotation are in a stopped state, and a control loop is configured to maintain the screw rotation angle at a predetermined angle so that the screw rotation angle is maintained. . At this time, the flight 5 of the plasticized portion of the screw 1 is in a compressed state in which compression is applied to unmelted / semi-melted resin.

  The screw 1 receives the rotational force Fθ in the screw rotation direction as shown in FIG. 1 from the resin in the compressed state of the grooves 6 between the flights 5. When the injection is started and the screw 1 starts to move forward, the back flow of the molten resin starts from the gap between the check ring 3 and the check sheet 4 as the screw 1 starts moving forward. The molten resin flowing backward is a part of the molten resin measured in the measuring step. The pressure of the molten resin that has flowed back acts on the flight 5 of the screw 1 to apply a rotational force that rotates the screw 1, and the rotational force Fθ increases.

  Eventually, the check ring 3 moves and comes into close contact with the check seat 4 to close the check valve. Since the backflow of the molten resin is eliminated by closing the backflow prevention valve, the rotational force starts to decrease. As a result, when the backflow prevention valve is closed, the rotational force takes a peak value, and thereafter, only the rotational force received from the resin in the compressed state accumulated in the groove 6 between the flights 5 is obtained.

  Of the rotational force described above, during the period from the start of injection until the backflow prevention valve is closed, a force in the direction of rotating the screw reversely acts by the backflowed molten resin, and the screw is rotated in the reverse rotation direction. The reverse rotation direction is a rotation direction opposite to the rotation direction in which the screw rotates in the weighing process.

  After the time point when the backflow prevention valve is closed, the backflow of the molten resin is eliminated, so that the rotational force does not act on the screw, and the screw cannot be rotated in the reverse rotation direction. Therefore, the closed state of the backflow prevention valve can be determined based on the rotation angle waveform indicating the rotation angle of the screw from the start of injection provided in the injection molding machine.

  FIG. 2 shows a waveform pattern of the screw rotation angle from the start of injection. 2A to 2D, the horizontal axis represents the elapsed time from the start of injection, and the vertical axis represents the screw rotation angle.

  FIG. 2 (a) shows a waveform pattern when the check valve is closed during injection. This waveform pattern has a peak value. FIG. 2B also shows a waveform pattern when the check valve is closed during injection. Even if the backflow prevention valve is closed after the start of injection, depending on the type of resin and molding conditions, a waveform pattern (pattern) that turns to a gradual monotonic increase after a monotonic increase as shown in FIG. 1) A waveform pattern (pattern 2) that does not change after monotonic increase and then decreases rapidly, or a waveform pattern (pattern 3) that starts to decrease slightly after monotonous increase and then decreases rapidly may be obtained.

  FIG. 2 (c) shows a waveform pattern when the check valve is not closed during injection. The backflow prevention valve closes by the end of the injection due to abnormalities in the backflow prevention valve such as breakage or wear of the backflow prevention valve, or unmelted resin hindering the closing of the backflow prevention valve due to a failure in molding conditions, etc. May not. In such a case, since the screw is rotated in the reverse direction in the entire section from the start to the completion of injection, the waveform pattern is monotonically increasing (pattern 4), the waveform pattern is not changing after monotonically increasing (pattern 5), or A waveform pattern (pattern 6) that slightly decreases after a monotonous increase is obtained.

  FIG. 2D shows a waveform pattern when the backflow prevention valve is closed at the start of injection. When the control for closing the backflow prevention valve in advance from the completion of the measurement to the start of injection is performed, the backflow prevention valve may be already closed at the start of injection. In this case, since the screw cannot be reversely rotated during injection, a waveform pattern in which the rotation angle does not change is obtained as shown in FIG. 2D (displayed as a minute waveform in FIG. 2D).

As described above, the waveform pattern of the screw rotation angle varies depending on the state of the check valve. Therefore, the closed state of the backflow prevention valve can be determined by reading the waveform pattern of the rotation angle of the screw.
2 (a) to 2 (d), the horizontal axis may be the screw position (screw axial position) or the screw advance distance from the start of injection, instead of the elapsed time from the start of injection. Good.

Next, an embodiment will be described in which a predetermined reference value is set to determine the closed state of the check valve.
FIG. 3 is a diagram illustrating an embodiment for determining the closed state of the check valve with reference to the first predetermined angle. Using FIG. 3, the rotation angle at a predetermined time after the start of injection is read from the screen of the display device of the injection molding machine, and the closed state of the backflow prevention valve at the predetermined time is determined from the read rotation angle value of the screw. Will be explained.

  FIG. 3 shows that the predetermined time point is set to the time point when the screw is moved by the movable stroke of the check valve. When the backflow prevention valve is closed at a predetermined time, the rotational force caused by the backflowed molten resin does not act on the screw, so the rotational angle of the screw is a small value. In addition, when the backflow prevention valve is not closed at a predetermined time, the rotational force of the backflowed molten resin acts on the screw, causing the screw to reversely rotate, and the rotation angle has a large value.

  Therefore, in order to determine whether or not the backflow prevention valve is normally closed, the screw rotation angle at a predetermined time point is read, and when the read rotation angle is smaller than the first predetermined angle, It is determined that the backflow prevention valve is closed, and if the read rotation angle is larger than the first predetermined angle, it is determined that the backflow prevention valve is not closed at a predetermined time.

  Here, one example of setting the first predetermined angle will be described. When the rotation angle at the predetermined time when the check valve is normally closed and the rotation angle at the predetermined time when the check valve is not normally closed are known, the rotation at the normal time and the abnormal time An intermediate value of the angles can be set as the first predetermined angle.

  Actually, the screw rotation angle when the backflow prevention valve is not normally closed due to an abnormality is large, and the screw rotation angle when the backflow prevention valve is normally closed is almost zero. Therefore, the first predetermined angle may be set to a rotation angle having a substantially zero value.

  As described above, FIG. 3 shows that the predetermined time point is set to the time point when the screw moves by the movable stroke of the check valve. Alternatively, if the normal check point of the backflow prevention valve is known for each molding condition or each molded product, the known closing time is taken as a predetermined point and the rotation angle at that point is read. Good.

  In addition to the time when the screw has advanced by the movable stroke of the backflow prevention valve, the time point for determining the closed state of the backflow prevention valve is not only when the injection speed is switched, when the screw advance is completed, or from the speed control. It is good also as the time of switching to pressure control.

  Usually, the backflow prevention valve is often closed from the start of injection to the time when the screw moves forward by the movable stroke of the backflow prevention valve. If for some reason the backflow prevention valve is not closed properly, the backflow prevention valve will not close even if the screw has moved forward by the amount of movable stroke of the backflow prevention valve from the start of injection. Or the check valve may not close to the end.

  Therefore, in order to determine whether or not the check valve is normally closed, the rotation angle when the screw has advanced by the movable stroke of the check valve is read, and the read rotation angle is the first predetermined angle. If smaller, it is determined that the check valve is normally closed. If the read rotation angle is larger than the first predetermined angle, it is determined that the check valve is abnormally closed.

  FIG. 4 is a diagram for explaining an embodiment for determining the closed state of the check valve with reference to the second predetermined angle. When the control for closing the backflow prevention valve in advance is performed from the completion of measurement to the start of injection, the backflow prevention valve may be already closed at the start of injection. In such a case, since the screw cannot be rotated in reverse during the injection, the rotation angle of the screw does not change as shown in FIG.

Therefore, if it can be read that the detected rotation angle is greater than or equal to the second predetermined angle between the start of screw advance and completion, it is determined that the backflow prevention valve was not closed before the start of screw advance. If it can be read that the detected rotation angle is not greater than or equal to the second predetermined angle, it can be determined that the backflow prevention valve has been closed before the start of screw advancement.
As shown in FIG. 2D, when the backflow prevention valve is closed at the start of injection, the screw rotation angle is almost zero, so the second predetermined angle is set to a value of almost zero. You may make it set to a rotation angle.

  FIG. 5 is a diagram for explaining an embodiment in which the closed state of the check valve is determined based on the third predetermined angle. When the backflow prevention valve does not operate normally and the backflow prevention valve does not close, the back flow rate of the molten resin may become extremely large. In this case, since the rotational force acting on the screw is increased, the screw is greatly rotated in the reverse rotation direction.

Therefore, when it can be read that the detected rotation angle is equal to or greater than the third predetermined angle from the start to the completion of the screw advance, it is determined that the check valve is closed abnormally and the detected value is detected. When it can be read that the rotation angle does not exceed the third predetermined angle, it can be determined that the check valve is normally closed.
Even when the backflow prevention valve is closed during injection, the screw is rotated by a predetermined angle. The third predetermined angle is set by selecting a value exceeding the rotation angle that rotates when the screw is normally closed.

FIG. 6 is a main part block diagram of an embodiment of an injection molding machine to which the method for determining the closed state of the check valve of the present invention is applied.
A nozzle 9 is attached to the tip of the cylinder 7 in which the screw 1 is inserted, and a hopper 15 for supplying resin pellets into the cylinder 7 is attached to the rear end of the cylinder 7. As shown in FIG. 1, the screw 1 is provided with a check valve 3 including a check ring 3 and a check seat 4. The screw 1 is rotationally driven via a transmission mechanism 12 by a screw rotating servo motor 10 as rotational driving means for rotationally driving the screw 1. Further, the injection servo motor 11 as an axial driving means for driving the screw 1 in the axial direction causes the screw 1 to move in the axial direction by a conversion mechanism 14 that converts the rotational motion of the transmission mechanism 13 and the ball screw / nut into linear motion. And injection and back pressure control.

  Position / speed detectors 16 and 17 for detecting the rotational position / speed are attached to the screw rotation servo motor 10 and the injection servo motor 11, and the rotational position / speed of the screw 1 is detected by the position / speed detector. The speed, the position of the screw 1 (position in the screw axis direction), and the moving speed (injection speed) can be detected. Further, a pressure sensor 18 such as a load cell for detecting the pressure from the molten resin applied to the screw 1 is provided.

  The control device 20 for controlling this injection molding machine is connected by a bus 36 to a CNC CPU 22 which is a numerical control microprocessor, a PMC CPU 21 which is a programmable machine controller microprocessor, and a servo CPU 25 which is a servo control microprocessor. Has been.

  A ROM 26 storing a sequence program for controlling the sequence operation of the injection molding machine and a RAM 27 used for temporary storage of calculation data are connected to the PMC CPU 21, and a program for controlling the injection molding machine as a whole is connected to the CNC CPU 22. A stored ROM 28 and a RAM 29 used for temporary storage of calculation data are connected.

  The servo CPU 25 is connected to a ROM 31 that stores a control program dedicated to servo control that performs processing of a position loop, a speed loop, and a current loop, and a RAM 32 that is used for temporary storage of data.

  Further, a servo amplifier 34 for the screw rotation servomotor 10 and a servo amplifier 35 for the injection servomotor 11 are connected to the servo CPU 25, and position / speed detectors 16, 17 are connected to the servomotors 10, 11. Are attached, and the outputs of the position / velocity detectors 16 and 17 are fed back to the servo CPU 25.

  The servo CPU 25 is positioned based on the movement command to each axis (screw rotation servo motor 10 or injection servo motor 11) commanded from the CNC CPU 22 and the detection position and speed fed back from the position / speed detectors 16 and 17. In addition to performing speed feedback control, current feedback control is also performed to drive and control the servo motors 10 and 11 via the servo amplifiers 34 and 35, respectively. Further, a current position register for storing the rotational positions of the screw rotation servomotor 10 and the injection servomotor 11 fed back from the position / speed detectors 16 and 17 is provided. Depending on the rotational position of the servomotors 10 and 11, The rotational position of the screw 1 (hereinafter referred to as “rotational angle”) and the axial position (injection position) can be detected. The servo CPU 25 receives a detection resin pressure (resin pressure applied to the screw 1) obtained by converting the detection signal from the pressure sensor 18 into a digital signal by the A / D converter 33.

  A servo motor and a servo amplifier for driving the mold clamping mechanism and the ejector mechanism are also provided, but these are not directly related to the present invention and are omitted in FIG.

  An input device 30 with a display device composed of a liquid crystal or a CRT is connected to a bus 36 via a display circuit 24. Further, a molding data storage RAM 23 composed of a non-volatile memory is also connected to the bus 36, and the molding data storage RAM 23 stores molding conditions, various set values, parameters, macro variables, etc. relating to the injection molding operation.

  With the above-described configuration, the PMC CPU 21 controls the sequence operation of the entire injection molding machine, and the CNC CPU 22 instructs the servo motors for each axis to move based on the operating program in the ROM 28 and the molding conditions stored in the molding data storage RAM 23. Servo CPU 25 detects the movement command distributed to each axis (servo motor of each drive axis such as screw rotation servomotor 10 and injection servomotor 11) and a position / speed detector. Based on the position and velocity feedback signals, servo control such as position loop control, velocity loop control, and current loop control is performed in the same manner as in the past, and so-called digital servo processing is executed.

  The above-described configuration is the same as that of a conventional electric injection molding machine control device. The difference from the conventional control device is that the rotation angle and position of the screw 1 are measured and stored in association with each other during screw advancement, and displayed. A function realized by processing of a flowchart showing an algorithm described later, such as a rotation angle display function to be performed, is added.

FIG. 7 is a flowchart showing an algorithm for measurement of the screw rotation angle during screw advance and its display processing, which is executed in an embodiment of the present invention.
When injection is started, the CNC CPU 22 of the control device 20 executes screw rotation angle measurement and display processing shown in FIG. The screw rotation angle can be detected by a position / speed detector 16 attached to the screw rotation servomotor 10. Actually, as described in FIG. 6, the value of the current position register that stores the rotational position of the screw rotation servomotor 10 is read (step SA1).

  The read screw rotation angle is stored in the RAM 29 in time series (step SA2). Then, it is determined whether or not the screw movement is finished (step SA3). If the screw movement has not ended, the process returns to step SA1, and the above-described processing of step SA1 to step SA3 is executed for each predetermined sampling period. Accordingly, the screw rotation angle is stored in the RAM 29 in time series at intervals of the sampling period.

  When the screw movement is completed, the screw rotation angle stored in the RAM 29 is displayed on the display screen of the display device / input device 30, the horizontal axis is the time axis, and the screw rotation angle is the vertical axis, as shown in FIG. The waveform of the rotation angle is displayed (step SA4), and this process is terminated.

  The operator determines the closed state of the check valve from the displayed waveform pattern of the screw rotation angle. That is, as shown in FIGS. 2 (a) to 2 (d), the waveform pattern of the screw rotation angle changes depending on the closed state of the backflow prevention valve. The closed state of the check valve can be determined.

  The waveform display may be drawn by overlapping the waveform pattern of the screw rotation angle for a plurality of molding cycles.In this case, the waveform in the latest molding cycle is displayed by changing display attributes such as the display color, It is sufficient to clarify that the waveform is the latest.

  In the embodiment described above, the waveform of the screw rotation angle is displayed with the horizontal axis as the time axis. However, the waveform of the screw rotation angle may be displayed together with the position of the screw moving forward as a function of the position. .

  In this case, the screw position is read from the current position register that stores the rotation position of the servo motor 11 for injection, the screw position and the screw rotation angle are associated with each other and stored in the RAM 29, and the horizontal axis represents the screw position. The waveform of the screw rotation angle is displayed.

  In the above-described embodiment, the example in which the screw rotation angle from the start of injection is measured and stored has been described. However, the control for advancing the screw before the start of injection is performed and the check valve is closed. Sometimes it is done. In such a case, the screw rotation angle may be measured during the screw advancement process before injection, and the waveform thereof may be displayed.

Next, a processing algorithm for determining the closed state based on the first predetermined angle, the second predetermined angle, and the third predetermined angle will be described with reference to FIGS.
FIG. 8 is a flowchart showing an algorithm of processing for determining the closed state of the check valve with reference to the first predetermined angle. Hereinafter, it demonstrates according to each step.

When the injection is started, the CNC CPU 22 of the control device 20 starts the processing of the flowchart of the algorithm shown in FIG.
The screw position is read from the current position register, and it is determined whether or not the read screw position is a predetermined time. If it is not the predetermined time, the process returns to step SB1, and if it is the predetermined time, the screw rotation angle is read from the current position register. (Step SB1 to Step SB3).

  Next, it is determined whether or not the screw rotation angle acquired in step SB3 is smaller than the first predetermined angle. If it is smaller, it is determined that the backflow prevention valve is closed while moving to a predetermined time, and is not small. In this case, it is determined that the backflow prevention valve has not been closed during the movement to the predetermined time point, the determination result in each case is displayed, and the process is terminated (steps SB4 to SB7).

  As described above, the predetermined time is the time when the screw is moved by the movable stroke of the backflow prevention valve, or when the backflow prevention valve is closed normally at each molding condition or for each molded product. A known closing time, screw advance completion time, injection speed switching time, or speed control to pressure control switching time may be set as the predetermined time.

Next, a flow chart showing an algorithm of processing for determining the closed state of the check valve with reference to the second predetermined angle shown in FIG. 9 will be described. Hereinafter, it demonstrates according to each step.
When the injection is started, the CNC CPU 22 of the control device 20 starts the processing of the flowchart of the algorithm shown in FIG.
The screw position and the rotation angle of the screw are read from the corresponding current position registers, respectively, and it is determined whether or not the screw rotation angle is smaller than the second predetermined angle. If it is determined that the screw rotation angle is smaller, it is determined whether or not the screw movement is finished. If the screw movement is not finished, the process returns to step SC1, and the above-described processing of step SC1 to step SC4 is executed for each predetermined sampling period (step SC1 to step SC4).

  When it is determined in step SC3 that the angle is not smaller than the second predetermined angle (in other words, when it is determined that the angle is equal to or larger than the second predetermined angle), it is determined that the backflow prevention valve is not closed at the start of injection. Then, the process proceeds to step SC6 (step SC7). If it is determined in step SC4 that the screw movement has ended, it is determined that the backflow prevention valve has been closed at the start of injection, and the process proceeds to step SC6 (step SC5). Then, the determination result at step SC5 or the determination result at step SC7 is displayed on the display device, and the process is terminated (step SC6).

Next, a flowchart illustrating an algorithm of processing for determining the closed state of the check valve with reference to the third predetermined angle shown in FIG. 10 will be described. Hereinafter, it demonstrates according to each step.
When the injection is started, the CNC CPU 22 of the control device 20 starts the processing of the flowchart of the algorithm shown in FIG.

  The screw position and the rotation angle of the screw are read from the corresponding current position registers, respectively, and it is determined whether or not the screw rotation angle is smaller than the third predetermined angle. If the screw movement is not completed, the process returns to step SD1, and the above-described processing of step SD1 to step SD4 is executed for each predetermined sampling period (step SD1 to step SD4).

  If it is determined in step SD3 that the angle is not smaller than the third predetermined angle (in other words, if it is determined that the angle is equal to or greater than the third predetermined angle), it is determined that the check valve has not closed during the injection; The process proceeds to step SD6 (step SD7). If it is determined in step SD4 that the screw movement has ended, it is determined that the backflow prevention valve is closed during the injection, and the process proceeds to step SD6 (step SD5). Then, the determination result in step SD5 or the determination result in step SD7 is displayed on the display device, and the process is terminated (step SD6).

  As the display of the determination result in FIGS. 7, 8, 9, and 10 described above, a display that can be distinguished such as “normal / abnormal”, “closed / not closed”, or “◯ / ×”. Any method can be used.

  Moreover, in the flowchart shown by FIG.7, FIG.8, FIG.9 and FIG.10 mentioned above, although the display of a screw rotation angle or the closing condition of a backflow prevention valve is performed, in addition to this, You may add the determination which determines the quality of a molded article based on the closed state of a backflow prevention valve, and the step which outputs the determination result. When the backflow prevention valve does not close normally, the resin filling amount during injection decreases from the measured resin amount, or the resin filling amount becomes unstable for each shot. Therefore, when the backflow prevention valve is not normally closed, the molded product in the molding cycle can be determined as a defective product. In addition, a step of outputting an alarm based on the closed state of the check valve may be added. The alarm allows the operator to quickly recognize an abnormal closing of the check valve.

  Further, in each of the above-described embodiments, it is desirable to provide a control system having an action of returning the screw rotation angle to the original rotation angle when the backflow prevention valve is closed and the rotational force does not act on the screw. For example, a control system that constitutes a position loop with respect to the screw rotation angle may be provided, or a control system that constitutes a speed loop including an integrator with respect to the screw rotation speed may be provided.

  Furthermore, although each embodiment mentioned above demonstrated in the example of the injection molding machine which rotates a screw with an electric motor, this invention is applicable also when rotating a screw with a hydraulic motor.

It is explanatory drawing explaining the backflow of the resin which generate | occur | produces during the injection | pouring and the backflow prevention valve provided in the screw front-end | tip. It is explanatory drawing of the waveform pattern of the screw rotation angle from the injection start. It is a figure explaining embodiment which discriminate | determines the closed state of a backflow prevention valve on the basis of a 1st predetermined angle. It is a figure explaining embodiment which discriminate | determines the closed state of a backflow prevention valve on the basis of a 2nd predetermined angle. It is a figure explaining embodiment which discriminate | determines the closed state of a backflow prevention valve on the basis of the 3rd predetermined angle. It is a principal part block diagram of one Embodiment of the injection molding machine which applies the closed state discrimination | determination method of the backflow prevention valve of this invention. It is a flowchart which shows the algorithm of the measurement of the screw rotation angle during screw advance, and the display process performed in one Embodiment of this invention. It is a flowchart which shows the algorithm of the process which discriminate | determines the closed state of a backflow prevention valve on the basis of a 1st predetermined angle. It is a flowchart which shows the algorithm of the process which discriminate | determines the closed state of a backflow prevention valve on the basis of a 2nd predetermined angle. It is a flowchart which shows the algorithm of the process which discriminate | determines the closed state of a backflow prevention valve on the basis of the 3rd predetermined angle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screw 2 Screw head 3 Check ring 4 Check sheet 5 Flight 6 Groove part 7 Cylinder 10 Servo motor for screw rotation 11 Servo motor for injection 20 Control apparatus

Claims (12)

The screw rotation angle is controlled to be maintained at a predetermined angle during the forward movement of the screw, the rotational angle of the screw is detected during the forward movement of the screw, and the change of the detected rotational angle is displayed on the screen of the display device on the screw position or screw. A method for determining a closed state of a backflow prevention valve in an injection molding machine, wherein a waveform is displayed with the passage of time during forward movement, and the closed state of the backflow prevention valve is determined based on a waveform pattern displayed on the screen of the display device. The screw rotation angle is controlled to be maintained at a predetermined angle during the forward movement of the screw, the rotational angle of the screw is detected during the forward movement of the screw, and the change of the detected rotational angle is displayed on the screen of the display device on the screw position or screw. When a waveform is displayed with the passage of time during advance and the rotation angle waveform displayed on the screen of the display device reads the rotation angle at a predetermined point in time when the screw is moving forward, and the read rotation angle is greater than or equal to the first predetermined angle An injection molding machine that determines that the backflow prevention valve has not been closed by a predetermined time and determines that the backflow prevention valve has been closed by a predetermined time when the read rotation angle is smaller than the first predetermined angle Of determining the closed state of the backflow prevention valve.   3. The predetermined time point is a time point when the screw advances, a time point when the injection speed is switched, a time point when the speed control is switched to the pressure control, or a time point when the screw moves forward by the movable stroke of the check valve. A method for determining a closed state of a check valve for an injection molding machine according to claim 1. The screw rotation angle is controlled to be maintained at a predetermined angle during the forward movement of the screw, the rotational angle of the screw is detected during the forward movement of the screw, and the change of the detected rotational angle is displayed on the screen of the display device on the screw position or screw. In the rotation angle waveform displayed on the screen of the display device with the passage of time during the advancement, the detected rotation angle exceeds the second predetermined angle in all sections from the start of screw advancement to completion. When there is no backflow prevention valve, the backflow prevention valve is closed at the start of screw advancement. The screw rotation angle is controlled to be maintained at a predetermined angle during the forward movement of the screw, the rotational angle of the screw is detected during the forward movement of the screw, and the change of the detected rotational angle is displayed on the screen of the display device on the screw position or screw. In the rotation angle waveform displayed on the screen of the display device with the passage of time during advance, the detected rotation angle exceeds the third predetermined angle in all sections from the start of screw advance to the end. A method for determining the closed state of the backflow prevention valve of the injection molding machine, in which it is determined that the backflow prevention valve is closed abnormally. A control loop for maintaining the screw rotation angle at a predetermined angle during the screw advance, and a rotation angle detection means for detecting the screw rotation angle during the screw advance ,
A rotation angle at a predetermined time point during the forward movement of the screw is detected. If the detected rotation angle is equal to or greater than the first predetermined angle, it is determined that the backflow prevention valve has not been closed by the predetermined time point. An injection molding machine equipped with a check function for determining whether or not a check valve is closed, comprising: a determining means for determining that the check valve is closed by a predetermined time when it is smaller than a predetermined angle of 1 . The predetermined time point may be any one of the time point when the screw advance is completed, the time when the injection speed is switched, the time point when the speed control is switched to the pressure control, or the time when the screw moves forward by the movable stroke of the check valve. An injection molding machine provided with the backflow prevention valve closed state discrimination function according to claim 6 . A control loop for maintaining the screw rotation angle at a predetermined angle during the screw advance, and a rotation angle detection means for detecting the screw rotation angle during the screw advance,
Comparison means for sequentially comparing the detected rotation angle and the second predetermined angle between the start and completion of the screw advancement;
And a discriminating means for discriminating that the backflow prevention valve is closed at the start of the screw advance when the detected rotation angle does not exceed the second predetermined angle in the entire section from the start to the completion of the screw advance. An injection molding machine equipped with a check function for determining a closed state of a backflow prevention valve. A control loop for maintaining the screw rotation angle at a predetermined angle during the screw advance, and a rotation angle detection means for detecting the screw rotation angle during the screw advance,
Between TEDA to completion from the screw starts moving forward, and comparing means for comparing the rotation angle and the third predetermined angle and the detected sequentially,
An injection molding machine provided with a check function for determining whether or not the check valve is closed, including a check means for determining that the check valve is closed abnormally when the detected rotation angle exceeds a third predetermined angle . 10. The injection molding machine having a backflow prevention valve closed state determination function according to any one of claims 6 to 9, wherein the closed state of the backflow prevention valve determined by the determination means is displayed on a display device. . The backflow prevention valve closed state determination function according to any one of claims 6 to 9 , wherein the quality of the molded product is determined based on the closed state of the backflow prevention valve determined by the determination means. Injection molding machine. 10. The injection molding with the backflow prevention valve closed state determination function according to any one of claims 6 to 9 , wherein an alarm is output based on the closed state of the backflow prevention valve determined by the determination means. Machine.

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