JP2007196391A - Injection molding machine and method for detecting abnormality of pressure detector set in injection molding machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily confirm the abnormality of a pressure detector without detaching it from an injection molding machine. <P>SOLUTION: The injection molding machine 1 includes driving parts 29 and 46, driven parts 23 and 52 to which axial force is transmitted by the driving parts 29 and 46 and which are moved forward/backward, regulation means 5, 11, and 70 for restricting the forward/backward movement of the driven parts, pressure detectors 35 and 48 for detecting the axial force transmitted to the driven parts 23 and 52 as pressure, and a controller 45 for calculating driving force on the basis of a current value given to the driving parts 29 and 46 in order to control the movement of the driving parts 29 and 46 while the forward/backward movement of the driven parts 23 and 52 is restricted by the regulation means 5, 11, and 70. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an injection molding machine and a method for detecting an abnormality of a pressure detector provided in the injection molding machine, and more specifically, to an injection molding machine equipped with a pressure detector such as a load cell and the injection molding machine. The present invention relates to a method for detecting an abnormality in a detected pressure detector.

  In an injection molding machine including an injection device, a mold device, and a mold clamping device, the resin is heated and melted in a heating cylinder of the injection device. The molten resin is injected at a high pressure and filled in the cavity of the mold apparatus. The resin is cooled and solidified in the cavity of the mold apparatus to form a molded product.

  The mold apparatus includes a fixed mold and a movable mold. By closing and moving the movable mold along the tie bar with respect to the fixed mold by the mold clamping device, mold closing, mold clamping and mold opening are performed.

  When mold clamping of the mold apparatus is completed and the injection apparatus is advanced, the nozzle of the heating cylinder is pressed against the sprue bush provided on the back surface of the fixed mold through the nozzle passage hole formed in the fixed platen. .

  Subsequently, the resin melted by the injection device is pressurized by the screw in the heating cylinder and injected from the nozzle. The injected molten resin is filled into a cavity formed between the fixed mold and the movable mold through the sprue bush and the sprue.

  In addition, the screw drive mechanism of the injection device is provided with a load cell as a pressure detector for detecting the pressure of the molten resin applied to the screw (reaction force of the molten resin).

  Further, the tie bar of the mold clamping device is provided with a tie bar sensor as a pressure detector for measuring the mold clamping force of the movable mold and the fixed mold.

  In the injection molding machine having such a configuration, if the above-described pressure detector fails, the pressure of the molten resin or the clamping force cannot be accurately detected. Due to a malfunction (abnormal operation) of the pressure detector, the pressure of the molten resin or the mold clamping force exceeds a predetermined pressure, and as a result, the quality of the molded product is impaired, and further, the mold is damaged. There was a fear.

  In addition, when the amount of pressure change per specified movement amount of the injection shaft is detected based on the output of the pressure detector, and this pressure change amount is compared with a reference value having a predetermined range in the comparison unit and is not within the reference value range. An aspect that is regarded as a failure of the pressure detector has been proposed (see Patent Document 1).

There is also an aspect in which an abnormality of the pressure detection sensor is determined by comparing the output value detected and output by the pressure detection sensor with the setting value of the setting device set to be the same as the setting value of the pressure control valve. It has been proposed (see Patent Document 2).
Japanese Utility Model Publication No. 6-9924 Japanese Utility Model Publication No. 5-53918

  However, in the conventional injection molding machine, there is no separate detection means for detecting the pressure of the molten resin applied to the screw and the mold clamping force other than the above-described load cell or tie bar sensor. Therefore, it has been difficult to grasp abnormal operation such as abnormal output of the load cell or tie bar sensor.

  Therefore, each time the pressure detector is inspected, a service person is called to disassemble the injection molding machine, remove the pressure detector from the injection molding machine, and apply a reference pressure by a predetermined diagnostic device or the like to apply pressure. It is inconvenient because it is determined whether or not the detector is operating correctly, and it is necessary to stop the injection molding machine each time the determination is made.

  The present invention has been made in view of the above-described problems, and is provided in an injection molding machine and an injection molding machine that can easily check the abnormality of the pressure detector without removing the pressure detector from the injection molding machine. Another object of the present invention is to provide a method for detecting an abnormality of a pressure detector.

  According to one aspect of the present invention, a driving unit, a driven unit that is advanced and retracted when an axial force is transmitted by the driving unit, a restricting unit that restricts forward or backward movement of the driven unit, and the driven A pressure detector for detecting the axial force transmitted to the part as a pressure, and the drive part for controlling the movement of the drive part in a state where the forward or backward movement of the driven part is restricted by the restricting means. An injection molding machine comprising: a control device that calculates a driving force based on a current value given to

  The control device compares the current value given to the drive unit with a detection value detected by the pressure detector in a state where the forward or backward movement of the driven unit is restricted by the restriction unit. It is good.

  In the injection molding machine, a difference between a current value given to the driving unit and a detection value detected by the pressure detector in a state where the forward or backward movement of the driven unit is restricted by the regulating unit is determined in advance. If the value is larger than the above value, it may be displayed on the display unit of the control device that the pressure detector is abnormal.

  In the injection molding machine, the drive unit may be an injection motor, and the driven unit may be a screw. The driving unit may be a mold clamping motor, and the driven unit may be a movable platen.

  According to another aspect of the present invention, there is provided a method for detecting an abnormality of a pressure detector provided in an injection molding machine, wherein the injection molding machine is moved forward and backward by an axial force transmitted by a drive unit. A driving unit; and a restricting unit that restricts the forward or backward movement of the driven unit. The axial force transmitted to the driven unit is detected as a pressure by a pressure detector, and the driving unit detects the axial force transmitted to the driven unit. In the state where forward or backward movement is restricted, the method is provided in which the driving force is calculated based on the current value applied to the driving unit in order to control the movement of the driving unit.

  In the method, the current value given to the driving unit is compared with the detection value detected by the pressure detector in a state where the forward or backward movement of the driven unit is restricted by the restriction unit. Also good.

  In the method, a difference between a current value given to the driving unit and a detection value detected by the pressure detector in a state where the forward or backward movement of the driven unit is restricted by the regulating unit is a predetermined value. If larger, the display unit of the control device may display that the pressure detector is abnormal.

  According to the present invention, it is possible to easily check the abnormality of the pressure detector without removing the pressure detector from the injection molding machine, and to detect the abnormality of the pressure detector provided in the injection molding machine. A method can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, an outline of an injection molding machine to which the present invention is applied will be described with reference to FIG.

  Here, FIG. 1 is a diagram showing a schematic configuration of a screw type electric injection molding machine as an example of an injection molding machine to which the present invention is applied.

  The electric injection molding machine 1 shown in FIG. 1 includes a frame 10, an injection device 20 and a mold clamping device 50 arranged on the frame 10.

  The injection device 20 includes a heating cylinder 21, and the heating cylinder 21 is provided with a hopper 22. A heater 21 a for heating the heating cylinder 21 is provided on the outer periphery of the heating cylinder 21. A screw 23 is provided in the heating cylinder 21 so as to be movable forward and backward and rotatable. The rear end of the screw 23 is rotatably supported by the movable support portion 24.

  A measuring motor 25 such as a servo motor is attached to the movable support portion 24 as a drive portion. The rotation of the metering motor 25 is transmitted to the screw 23 of the driven part via a timing belt 26 attached to the output shaft 31.

  A rotation detector 32 is connected to the rear end of the output shaft 31. The rotation detector 32 detects the rotation speed or the rotation amount of the metering motor 25 to detect the rotation speed of the screw 23.

  The injection device 20 has a ball screw shaft 27 parallel to the screw 23. The ball screw shaft 27 is screwed with the ball screw nut 90 to constitute a motion direction conversion mechanism that converts rotational motion into linear motion.

  When the injection motor 29 that is a drive unit is driven and the ball screw shaft 27 is rotated via the timing belt 28, the movable support 24 and the support 30 fixed to the ball screw nut 90 move forward and backward. As a result, the screw 23 which is a driven part can be moved back and forth.

  The position detector 34 connected to the rear end of the output shaft 33 of the injection motor 29 detects the position of the screw 23 indicating the drive state of the screw 23 by detecting the rotation speed or rotation amount of the injection motor 29.

  Further, a load cell 35 as a pressure detecting device for detecting the pressure of the resin applied to the screw 23 is provided between the movable support portion 24 and the support 30.

  The injection device 20 includes a plasticizing movement device 40 as a drive mechanism that drives the injection device 20 and applies a nozzle touch pressure. The plasticizing movement device 40 includes a plasticizing movement driving unit 91 and an injection device guide unit 92. The injection device guide portion 92 is engaged with the movable support portion 24, the support 30, and the front flange 93 that constitute the injection device 20.

  Therefore, the injection apparatus 20 including the heating cylinder 21 can be moved horizontally on the frame 10 of the injection molding machine along the injection apparatus guide section 92 while the plasticizing movement driving section 91 is driven. By driving the plasticizing moving device 40 described above, the injection device 20 is moved forward at a predetermined timing to bring the nozzle of the heating cylinder 21 into contact with the fixed mold 53 and perform nozzle touch.

  The heating cylinder 21 is supported by the front flange 93. At the rear end of the front flange 93, a contact portion 5 that functions as a restricting means for restricting the forward or backward movement of the screw 23 is provided. When the screw 23 is in the most advanced state, the contact portion 5 performs forward movement on the apparatus side so that the tip portion of the screw 23 does not contact and damage a nozzle portion (not shown) provided in front of the heating cylinder 21. It is also a stopper for regulating. Therefore, in the stroke advance limit of the screw 23, the contact portion 5 comes into contact with the movable support portion 24.

  At this time, the reaction force of all axial forces given by the injection motor 29 is detected by the load cell 35. In this case, the characteristics of the mechanism unit alone of the injection device can be grasped by the contact portion 5 and the movable support portion 24 contacting each other. The contact portion 5 is not necessarily provided at the rear end of the front flange 93, and the rear end of the heating cylinder 21 may be used as the contact portion 5.

  As another form of the restricting means, the forward end of the screw 23 is restricted by closing the tip of the heating cylinder 21, and the reaction force is detected with the load plate 11 functioning as the restricting means. Good. The advancement of the screw 21 is restricted while the resin is filled in the heating cylinder 21. Accordingly, the resin pressure applied to the resin in the heating cylinder 21 by the injection motor 29, that is, the reaction force of the total axial force is detected by the load cell 35 which is the pressure detector described above.

  In this case, not only the characteristics of the mechanism part carrier of the injection apparatus 20 but also the characteristics of the entire injection apparatus 20 including the influence of the plasticizing part such as the screw 23 and the heating cylinder 21 such as the breakage of the screw 23 can be grasped. . Furthermore, by using the characteristics of the mechanism carrier detected by the contact portion 5 and the characteristics of the entire injection device 20 detected by the load plate 11, the characteristics of the plasticized carrier can be calculated.

  The weighing motor 25, the rotation detector 32, the injection motor 29, the position detector 34, and the load cell 35 are connected to the control device 45. Detection signals output from the rotation detector 32, the position detector 34, and the load cell 35 are sent to the control device 45. The control device 45 controls the operations of the metering motor 25 and the injection motor 29 based on the detection signal.

  In addition, the control apparatus 45 may be provided independently and may be provided as a part of control part which manages control of the whole injection molding machine.

  The mold clamping device 50 includes a fixed platen 54 as a fixed mold support device fixed to the frame 10, and a base plate disposed so as to be movable with respect to the frame 10 with a predetermined distance between the fixed platen 54. And a toggle support 56 as shown in FIG. The toggle support 56 functions as a toggle type mold clamping device support device. A plurality of (for example, four) tie bars 55 as guide means extend between the fixed platen 54 and the toggle support 56.

  The movable platen 52 is disposed so as to face the fixed platen 54 and functions as a movable mold support device disposed so as to be capable of moving back and forth (moving in the horizontal direction in the drawing) along the tie bar 55. Thus, the movable platen 52 moves along the tie bar 55, and mold closing, mold clamping and mold opening are performed.

  The mold apparatus 70 includes a fixed mold 53 and a movable mold 51.

  The fixed mold 53 is attached to a mold mounting surface of the fixed platen 54 that faces the movable platen 52. On the other hand, the movable mold 51 is attached to a mold mounting surface of the movable platen 52 that faces the fixed platen 54.

  A drive device for moving an ejector pin (not shown) may be attached to the rear end (left end in the figure) of the movable platen 52.

  A toggle mechanism 57 as a toggle type mold clamping device is attached between the movable platen 52 and the toggle support 56. A mold clamping motor 46 as a mold clamping drive source for operating the toggle mechanism 57 is disposed at the rear end of the toggle support 56.

  The mold clamping motor 46 includes a motion direction conversion device (not shown) including a ball screw mechanism that converts a rotational motion into a reciprocating motion. Can be activated.

  The mold clamping motor 46 is preferably a servo motor, and includes a mold opening / closing position sensor 47 as an encoder for detecting the rotation speed.

  The toggle mechanism 57 can be actuated by driving the mold clamping motor 46, which is a drive unit, to move the cross head 60 back and forth. In this case, when the cross head 60 is moved forward (moved in the right direction in the figure), the movable platen 52 that is the driven portion is moved forward to perform mold closing. Then, a mold clamping force obtained by multiplying the propulsive force of the mold clamping motor 46 by the toggle magnification is generated, and the mold clamping is performed by the mold clamping force.

  A mold thickness motor 41 as a mold clamping position adjusting drive source is disposed at an upper portion of the rear end of the toggle support 56.

  The mold thickness motor 41 is preferably a servo motor, and includes a mold clamping position sensor 42 as an encoder that detects the number of rotations.

  In the present embodiment, a tie bar sensor 48 is provided as a pressure detector in one of the tie bars 55. The tie bar sensor 48 is a sensor that detects distortion (mainly elongation) of the tie bar 55. The tie bar 55 is applied with a tensile force corresponding to the mold clamping force at the time of mold clamping, and extends slightly in proportion to the mold clamping force.

  Therefore, by detecting the extension amount of the tie bar 55 by the tie bar sensor 48, the mold clamping force actually applied to the mold apparatus 70 can be known. When the fixed mold 53 and the movable mold 51 are brought into contact with each other, the reaction force of the total axial force applied by the mold clamping motor 46 that is a drive unit is detected by a tie bar sensor 48 that is a pressure detector. That is, since the forward movement of the movable platen 52 is regulated by the fixed mold 53, the fixed mold 53 functions as a regulating means.

  The tie bar sensor 48, the mold opening / closing position sensor 42, the mold clamping motor 46 and the mold thickness motor 41 are connected to the control device 45, and detection signals output from the tie bar sensor 48 and the mold opening / closing position sensor 42 are sent to the control device 45. It is done. The control device 45 controls the operations of the mold clamping motor 46 and the mold thickness motor 41 based on the detection signal.

  Next, the operation | movement at the time of normal shaping | molding of the injection molding machine provided with this structure is demonstrated.

  When the mold clamping motor 46 is driven in the forward direction, the ball screw shaft 59 rotates in the forward direction and moves forward (moves in the right direction in FIG. 1). Along with this, when the cross head 60 moves forward and the toggle mechanism 57 is actuated, the movable platen 52 moves forward.

  When the movable mold 51 attached to the movable platen 52 comes into contact with the fixed mold 53, the mold clamping process is started. In the mold clamping process, a mold clamping force is generated in the mold apparatus 70 by the toggle mechanism 57 by further driving the mold clamping motor 46 in the forward direction.

  When the screw 23 is rotated in the heating cylinder 21, the resin pellets which are molding materials supplied from the hopper 22 are melted by the heater 21 a provided in the heating cylinder 21. The molten resin is stored at the tip of the screw 23, injected from the nozzle at the tip of the heating cylinder 21, and filled into the cavity space formed in the mold apparatus 70.

  When performing mold opening, the mold clamping motor 46 is driven in the reverse direction, and the ball screw shaft 59 rotates in the reverse direction. Along with this, when the cross head 60 moves backward and the toggle mechanism 57 is operated, the movable platen 52 moves backward.

  When the mold opening process is completed, an ejector driving unit (not shown) is driven, and the ejector device attached to the movable platen 52 is operated. Thereby, the ejector pin is protruded, and the molded product in the movable mold 51 is protruded from the movable mold 51.

  Next, a basic concept of an embodiment of a method for detecting an abnormality of a pressure detector provided in an injection molding machine according to the present invention will be described with reference to FIGS.

  Here, FIG. 2 is a flowchart showing a basic concept of an embodiment of a method for detecting an abnormality of a pressure detector provided in an injection molding machine according to the present invention. FIG. 3 is a graph showing the correlation between the input axial force of the drive unit and the detection value of the pressure detector described in the flowchart shown in FIG.

  Referring to FIG. 2, when inspecting the pressure detector in order to grasp an abnormal operation such as an output abnormality of the pressure detector such as the load cell 35 or the tie bar sensor 48 (see FIG. 1), first, the pressure The driven parts, such as the screw 23 and the movable platen 52, which are advanced and retracted by the driving part are stopped so that all the axial forces of the driving parts such as the injection motor 29 and the mold clamping motor 46 are applied to the detector (step S1). Details of how to stop the driven parts such as the screw 23 and the cross head 60 will be described later.

Under this state, based on the value (current value) of a predetermined current supplied to the drive unit in order to control the movement of the drive unit, the control unit 45 calculates an input axial force F _IN of the driving part (Step S2).

Then, the comparing means of the control device 45 compares the actual detection value F _LC detected by the pressure detector is transmitted to the driven parts by the driving unit, the value of the calculated input shaft force F _IN, the (Step S3).

Then, to calculate the difference between the input shaft force F _IN of the calculated and the detection value F _LC of the detected pressure detector driving unit. If the difference is within the predetermined allowable range X shown in FIG. 3, the pressure detector is determined to be normal, and if the difference exceeds the predetermined allowable range X, the pressure detector is abnormal. Is displayed on the display unit of the control device 45 (see FIG. 1). Here, the allowable range may be set, for example, as a theoretical value, that is, about ± 5% of the calculated value of the input axial force _FIN .

Next, in the injection device 20 of the electric injection molding machine 1 shown in FIG. 1, a step of stopping the driven portion so that all the axial force of the driving portion is applied to the pressure detector (step S <b> 1 in FIG. 2) and the driving portion. the value of the predetermined current supplied step of calculating an input axial force F _iN of the driving unit (current value) based on (step S2 in FIG. 2) will be described with reference to FIGS. 1 and 4.

  Here, FIG. 4 is a diagram for explaining step S2 shown in FIG. 2 in the injection apparatus 20 shown in FIG.

  As described with reference to FIG. 1, at the rear end of the front flange 93, the contact portion 5 that functions as a restricting means that restricts the forward or backward movement of the screw 23 that is the driven portion is provided. The injection device 20 is in the most advanced state, and the contact portion 5 is brought into contact with the front end surface of the movable support portion 24 to form a state in which the screw 23 cannot advance (step S1 in FIG. 2).

In this state, a constant torque is applied by the injection motor 29 in order to drive the screw 23 to move forward at a substantially constant speed in the injection direction. Filled resin pressure of the molten resin at this time, i.e., reaction force of the entire axial force applied by the injection motor 29 is detected as the detected value F _LC shown in step S4 by the load cell 35.

  Alternatively, as described above, the fixed platen 54 may be provided with the load plate 11 that functions as a restricting unit that blocks the tip of the heating cylinder 21 and restricts the forward or backward movement of the screw 23 that is the driven portion. The cavity formed in the molds 53 and 54 is filled with molten resin, and the load plate 11 is used to block the tip of the heating cylinder 21, thereby inhibiting the movement of the molten resin and restricting the forward or backward movement of the screw 23. (Step S1 in FIG. 2).

Under such a condition, a constant torque is applied by the injection motor 29 in order to drive the screw 23 forward at a constant speed in the injection direction. Filled resin pressure of the molten resin at this time, i.e., reaction force of the entire axial force applied by the injection motor 29 is detected as the detected value F _LC shown in step S4 by the load cell 35.

Is compared with the detected value F _LC according in step S3 shown in FIG. 2, the input shaft force F _IN of the injection motor 29 is calculated as follows (step S2 in FIG. 2).

Referring to FIG. 4, based on a signal input in control device 45, current command value T _cmd, which is a command for causing a predetermined value of current to flow from current control unit 100, is given to power module (PM) 101. In the power module (PM) 101, a voltage value corresponding to the current command value T _cmd is set, and the injection motor 29 is operated. Further, the measured value I _m of the current input to the injection motor 29 is detected by the optimum sensor gain CT by the current sensor not shown, and feedback control so that the deviation becomes zero.

In addition, the “current value” described in the claims means both the current command value T _cmd and the current value detected by the current sensor and feedback-controlled.

A motor output torque T _IJ is calculated from the voltage value and a motor physical model 110 representing conversion characteristics for converting electrical energy in the injection motor 29 into mechanical energy. Furthermore, the motor output torque T _IJ, the mechanical transfer function 120 which represents the mechanical transfer characteristics such as a belt 28 and a motion direction converting mechanism, the input shaft force F _IN of the injection motor 29 is calculated by.

Comparison means of the controller 45 compares the value of the thus input axial force F _IN that is calculated, actually the detected value F _LC detected by transmitted to the screw 23 the load cell 35 by the injection motor 29, the Te (step S3 in FIG. 2), calculates the difference between the input shaft force _{F iN} of the injection motor 29 and the calculated detection value _{F LC} of the load cell 35.

The difference is a predetermined allowable range, for example, the load cell 35 if ± about 5% within the calculated value of the input shaft force F _IN is determined to be normal and, if exceeding the allowable range The load cell 35 is determined to be abnormal.

Specifically, the display unit of the control device 45, both the detected value F _LC detected by the current command value T _cmd and the load cell 35 described above is displayed, or, the injection motor 29 as shown in FIG. 3 correlation between the detection value _{F LC} detected by the input shaft force _{F iN} or a current command value _{T cmd} and the load cell 35 is displayed.

  In this way, the operator of the injection molding machine 1 can easily perform abnormal operations such as abnormal output of the load cell 35 without disassembling the injection molding machine 1 by calling a serviceman or the like and removing the load cell 35 from the injection molding machine 1. Can grasp.

  Furthermore, by accumulating such correlation data, it is possible to grasp the respective characteristics of the mechanical part and the plasticizing part of the injection apparatus 20, and it is easy to trouble not only the load cell 35 but also other components. Can grasp.

  Moreover, although the example which advances the screw 23 was shown in this Embodiment, this invention is not restricted to this, You may reverse the screw 23. FIG. In this case, a portion where the support 30 and the injection device guide 92 contact each other (a portion indicated by hatching in the injection device guide 92 shown in FIG. 1) functions as the contact portion 5 so as to restrict the backward movement of the support 30. .

Further, the input shaft force F _IN and the load cell 35 that is calculated may also be displayed on the screen of the display device and a detection value F _LC detected. In this case, without calculating the difference between the input axial force _FIN and the detected value _FLC in the control device 45, the operator can determine whether or not there is an abnormality by looking at the screen.

Next, in the mold clamping device 50 of the electric injection molding machine 1 shown in FIG. 1, the step of stopping the driven portion so that the axial force of the driving portion is applied to the pressure detector (step S1 in FIG. 2) and the driving portion. the value of the predetermined current supplied step of calculating an input axial force F _iN of the driving unit (current value) based on (step S2 in FIG. 2), the description with reference to FIGS. 1, 5 and 6 To do.

  Here, FIG. 5 is a diagram for explaining step S2 shown in FIG. 2 in the mold clamping apparatus 50 shown in FIG. FIG. 6 is a graph showing the relationship between the reduction ratio of the toggle mechanism 57 shown in FIG. 1 and the position of the movable platen 52.

  As described with reference to FIG. 1, the fixed mold 53 and the movable mold 51 come into contact with each other to form a state in which the forward or backward movement of the crosshead 60 that is the driven part is restricted (in FIG. 2). Step S1).

Under such a state, the reaction force of the total axial force in the direction (from the left to the right in FIG. 1) applied by the mold clamping motor 46 which is a drive unit to drive the movable platen 52 forward at a substantially constant speed is a pressure. is detected as the detected value F _LC shown in step S4 by the tie bar sensor 48 is a detector.

It is compared with the detected value F _LC according in step S3 shown in FIG. 2, the input shaft force F _IN of the mold clamping motor 46 is calculated as follows (step S2 in FIG. 2).

Referring to FIG. 5, based on a signal input in control device 45, current command value T _cmd, which is a command for flowing a current having a predetermined value, is given to power module (PM) 201 from current control unit 200. . In the power module (PM) 201, a voltage value corresponding to the current command value T _cmd is set, and the mold clamping motor 46 is operated. It also detects the mold clamping measured value of the current input to the motor 46 I _m optimal sensor gain CT by the current sensor not shown, and is feedback controlled so that the deviation becomes zero.

In addition, the “current value” described in the claims means both the current command value T _cmd and the current value detected by the current sensor and feedback-controlled.

As in the case of the injection motor 29 shown in FIG. 4, the motor output torque T _MO is calculated from the voltage value and the motor physical model 210 representing the conversion characteristics for converting the electrical energy in the mold clamping motor 46 into mechanical energy. The

If the mold clamping motor 46 is decelerated by the toggle mechanism 57 (see FIG. 1), further, the reduction ratio K _B of the toggle mechanism 57, as shown in FIG. 6 changes the position P _OS of the movable platen 52. That is, the reduction ratio K _B of the toggle mechanism 57 more (the movement in the direction from left to right in FIG. 1) is raised forward movable platen 52, the mold clamping motor 46 is decelerated. That is, when calculating the input shaft force F _IN from the motor output torque T _MO, as shown in FIG. 5, not only the mechanical transfer function 220 represents the mechanical transfer characteristics such as a belt 28 and a motion direction converting mechanism, reduction ratio K _B must also be considered.

Therefore, to calculate the position P _OS of the movable platen 52 from the rotational angle of the mold clamping motor 46, the input shaft force F _IN is calculated also using the same.

That is, the motor output torque _{T MO} is generated in proportion to the current command value _{T cmd,} the input shaft force _{F IN} of the mold clamping motor 46 from the position _{P OS} of such motor output torque _{T MO} movable platen 52 is calculated.

Comparison means of the controller 45 compares the value of the thus input axial force F _IN which is calculated, and the actually detected value F _LC detected by the tie bar sensor 48 is transmitted to the crosshead 60 by a mold clamping motor 46, comparing (step S3 in FIG. 2), calculates the difference between the input shaft force F _iN of the mold clamping motor 46 and the calculated detection value F _LC of the tie bar sensor 48.

The difference is a predetermined allowable range, for example, tie bar sensor 48 if ± about 5% within the calculated value of the input shaft force F _IN is determined to be normal, and has exceeded the permissible range Therefore, it is determined that the tie bar sensor 48 is abnormal.

Specifically, the display unit of the control unit 45, displays both the detected value F _LC detected by the current command value T _cmd and tie bar sensor 48 described above, or mold clamping motor as shown in FIG. 3 correlation between the detection value _{F LC} detected by the input shaft force _{F iN} or a current command value _{T cmd} and tie bar sensor 48 of 46 is displayed.

  Thereby, the operator of the injection molding machine 1 can easily perform abnormal operations such as abnormal output of the tie bar sensor 48 without calling a serviceman to disassemble the injection molding machine 1 and detaching the tie bar sensor 48 from the injection molding machine 1. Can grasp.

  By the way, it is desirable to execute the above-described processing for detecting the abnormality of the load cell 35 and the tie bar sensor 48 after the origin adjustment of the load cell 35 and the tie bar sensor 48 and whenever the origin adjustment is performed. A process for detecting an abnormality in the load cell 35 and the tie bar sensor 48 is performed each time the origin is adjusted, and the result is stored as a history, which can be used as a material for periodic diagnosis of the injection molding machine.

  Although the embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment, and various modifications and changes are within the scope of the gist of the present invention described in the claims. It can be changed.

  In the above-described embodiment, the structure in which the mold clamping force of the mold apparatus 70 is detected by the tie bar sensor 48 is described as an example, but the present invention is not limited to this structure. For example, the present invention can be applied to the structure shown in FIG.

  Here, FIG. 7 is a diagram showing a schematic configuration of another example of a mold clamping device of an injection molding machine to which the present invention is applied. In addition, the same code | symbol is attached | subjected to the same location as the location shown in FIG. 1, and the description is abbreviate | omitted.

  Referring to FIG. 7, in this example, the movable mold 51 is attached to the movable mold mounting plate 150. A load cell 151 is provided between the movable mold mounting plate 150 and the movable platen 52. The load cell 151 detects the mold clamping force actually applied to the mold apparatus 70 in the same manner as the tie bar sensor 48 shown in FIG.

The detection value F _LC detected by the load cell 151, and the value of the calculated input shaft force F _IN, compares the difference between them is, the load cell 151 if it is within a predetermined allowable range is determined to be normal If the difference exceeds the predetermined allowable range, it is determined that the load cell 151 is abnormal, and a message to that effect is displayed on the display unit of the control device 45.

  Accordingly, also in this example, the operator of the injection molding machine 1 calls up a service person etc. to disassemble the injection molding machine 1 and remove the load cell 151 from the injection molding machine 1 without causing an abnormality such as an output abnormality of the load cell 151. The operation can be easily grasped.

It is a figure showing a schematic structure of a screw type electric injection molding machine as an example of an injection molding machine to which the present invention is applied. It is the flowchart which showed the basic concept of embodiment of the method of detecting the abnormality of the pressure detector provided in the injection molding machine by this invention. It is a graph showing the correlation between the detection value F _LC input axial force F _IN and the pressure detector of the drive unit in according to the flowchart shown in FIG. It is a figure for demonstrating step S2 shown in FIG. 2 in the injection device in FIG. It is a figure for demonstrating step S2 shown in FIG. 2 in the mold clamping apparatus shown in FIG. It is the graph which showed the relationship between the reduction ratio of the toggle mechanism shown in FIG. 1, and the position of a movable platen. It is a figure which shows schematic structure of the other example of the mold clamping apparatus of the injection molding machine to which this invention is applied.

Explanation of symbols

5 Contact portion 11 Load plate 20 Injection device 23 Screw 29 Injection motor 35 Load cell 45 Control device 46 Mold clamping motor 48 Tie bar sensor 50 Mold clamping device 51 Movable mold 52 Movable platen 53 Fixed mold

Claims (14)

A drive unit;
A driven part that is advanced and moved backward by an axial force transmitted by the driving part;
Restriction means for restricting forward or backward movement of the driven part;
A pressure detector that detects the axial force transmitted to the driven part as a pressure;
A control device that calculates a driving force based on a current value applied to the driving unit in order to control the movement of the driving unit in a state where the forward or backward movement of the driven unit is restricted by the restricting unit; An injection molding machine characterized by comprising. An injection molding machine according to claim 1,
The control device compares the current value given to the drive unit with a detection value detected by the pressure detector in a state where the forward or backward movement of the driven unit is restricted by the restriction unit. An injection molding machine characterized by An injection molding machine according to claim 2,
When the difference between the current value given to the drive unit and the detection value detected by the pressure detector in a state where the forward or backward movement of the driven unit is restricted by the regulating means is larger than a predetermined value In the injection molding machine, the display unit of the control device displays that the pressure detector is abnormal. An injection molding machine according to claim 3,
In the display unit of the control device, a current value given to the driving unit, a detection value detected by the pressure detector in a state where the forward or backward movement of the driven unit is restricted by the regulating unit, Is displayed on the injection molding machine. An injection molding machine according to claim 4,
In the display unit of the control device, a current value given to the driving unit, a detection value detected by the pressure detector in a state where the forward or backward movement of the driven unit is restricted by the regulating unit, An injection molding machine characterized in that the correlation between the two is displayed. An injection molding machine according to any one of claims 1 to 5,
The injection molding machine according to claim 1, wherein the axial force detected as the pressure by the pressure detector is an axial force in a direction in which the driven portion is advanced. An injection molding machine according to claim 6,
An injection molding machine characterized in that a speed at which the driven part advances is substantially constant. An injection molding machine according to any one of claims 1 to 7,
The injection is characterized in that the current value is a current value supplied from the current control unit to the driving unit or a current value feedback-controlled based on an actual measurement value of the current supplied to the driving unit. Molding machine. An injection molding machine according to any one of claims 1 to 8,
2. The injection molding machine according to claim 1, wherein the driving unit is an injection motor and the driven unit is a screw. An injection molding machine according to any one of claims 1 to 8,
An injection molding machine, wherein the driving unit is a mold clamping motor, and the driven unit is a movable platen. A method for detecting an abnormality in a pressure detector provided in an injection molding machine,
The injection molding machine includes a driven part that moves forward and backward when an axial force is transmitted by a driving part, and a restriction unit that restricts the forward or backward movement of the driven part,
The axial force transmitted to the driven part is detected as a pressure by a pressure detector,
A driving force is calculated based on a current value given to the driving unit in order to control the movement of the driving unit in a state where the forward or backward movement of the driven unit is restricted by the restricting means. The method. A method for detecting an abnormality of a pressure detector provided in an injection molding machine according to claim 11,
The current value given to the drive unit is compared with a detection value detected by the pressure detector in a state where the forward or backward movement of the driven unit is restricted by the restriction unit. Method. A method for detecting an abnormality of a pressure detector provided in an injection molding machine according to claim 12,
When the difference between the current value and the detected value detected by the pressure detector is larger than a predetermined value, the fact that the pressure detector is abnormal is displayed on the display unit of the control device. The method characterized by the above. A method for detecting an abnormality in a pressure detector provided in an injection molding machine according to claim 10,
The method is performed after the origin adjustment of the pressure detector.

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