TW201536518A - Injection molding machine - Google Patents

Abstract

The present invention provides an injection molding machine, which can improve the stability of the action. The injection molding machine of the present invention comprises: a detector for outputting a plurality of signals corresponding to a control amount; and a control device for computing an operation amount used in actual control according to a part of outputs from the plurality of outputs of the detector. In addition, the operation amount computed according to each output of the detector by the control device is uniform. Preferably, when computing the operation amount used in actual control, the control device enables the operation amount computed according to each output of the detector to be uniform.

Description

Injection molding machine

The present invention relates to an injection molding machine.

In the injection molding machine, a molding material is filled in a cavity space in a mold device, and a molded product is formed by curing the filled molding material (for example, see Patent Document 1). The injection molding machine includes a detector that outputs a signal corresponding to a control amount (for example, pressure), and a control device that calculates an operation amount (for example, a motor current value) based on the detected value and the set value of the detector.

(previous technical literature) (Patent Literature)

Patent Document 1: Japanese Laid-Open Patent Publication No. 2008-73874

The detector has a detection circuit that generates a signal corresponding to the control amount, and a variable amplifier that amplifies the signal of the detection circuit and outputs the signal to the control device. The gain of the variable amplifier can be changed depending on the type of the process, the magnitude of the control amount, and the like.

However, once the gain of the variable amplifier included in the detector changes, the signal from the detector changes, causing the correspondence between the signal and the detected value to change.

Therefore, the control device has a variable amplifier that amplifies the signal from the detector. The gain of the variable amplifier can be varied depending on the gain of the variable amplifier included in the detector. Thereby, the correspondence between the signal and the detected value can be maintained.

Conventionally, variations in the gain of the detector and the control device may occur, and an error may occur in the detected value, and the operation of the injection molding machine may become unstable.

The present invention has been made in view of the above problems, and an object thereof is to provide an injection molding machine capable of improving the stability of an operation.

In order to solve the above problems, according to the present invention, there is provided an injection molding machine comprising: a detector for outputting a plurality of signals corresponding to a control amount; and a control device according to one of a plurality of outputs selected from the foregoing detectors Part of the output, calculating the amount of operation for actual control.

According to the same aspect of the invention, an injection molding machine capable of improving the stability of the operation is provided.

10‧‧‧Molding device

11‧‧‧Frame

12‧‧‧Fixed platen

13‧‧‧ movable platen

15‧‧‧ rear platen

16‧‧‧ tied

18‧‧‧ Pressure detector

30‧‧‧Molding device

32‧‧‧Fixed mode

33‧‧‧ movable mold

50‧‧‧Injection device

51‧‧‧Cylinder

52‧‧‧ screw

53‧‧‧Measuring motor

54‧‧‧Injection motor

55‧‧‧ Pressure detector

56‧‧‧Strain gauge

57‧‧‧1st amplifier

58‧‧‧2nd amplifier

59‧‧‧Nozzles

60‧‧‧Ejecting device

70‧‧‧Control device

71‧‧‧1st Control Computing Department

72‧‧‧2nd Control Computing Department

73‧‧‧Inverter

Fig. 1 is a view showing an injection molding machine according to an embodiment of the present invention.

Fig. 2 is a view showing a control device and its peripheral devices according to an embodiment of the present invention.

In the following, the embodiments for carrying out the invention will be described with reference to the accompanying drawings, wherein the same or corresponding components are designated by the same or corresponding elements, and the description is omitted.

Fig. 1 is a view showing an injection molding machine according to an embodiment of the present invention. For example, as shown in Fig. 1, the injection molding machine includes a mold clamping device 10, an injection device 50, an ejection device 60, and a control device 70 (see Fig. 2). The mold clamping device 10 performs a mold closing process, a mold clamping process, and a mold opening process. The mold closing process is a process of closing the mold device 30, the mold clamping process is a process of fastening the mold device 30, and the mold opening process is a process of opening the mold device 30. The injection device 50 performs a filling process, a pressing process, and a metering process. The filling process is a process in which the cavity space 34 in the mold device 30 is filled with a liquid forming material, and the pressing process is a process of applying pressure to the forming material in the cavity space 34, and the measuring process is metering for forming the next injection. Process of materials. The ejector unit 60 performs an ejecting process. The ejecting process is a process of ejecting a molded article from the mold device 30 after the mold opening.

The injection molding machine performs automatic closing, for example, a mold closing process, a mold clamping process, a filling process, a press process, a cooling process, a metering process, and an open molding process. Process and launch process, automatic remanufacturing of molded products. The cooling process is a process for curing the forming material in the cavity space 34. In order to shorten the forming cycle, the metering process can be performed in the cooling process. For example, a mold closing process, a mold clamping process, a filling process, a press process, a cooling process, a metering process, a mold opening process, and a roll-out process are performed in one molding cycle.

Next, the mold clamping device 10 will be described. In the description of the mold clamping device 10, the moving direction of the movable platen 13 at the time of mold closing (the right direction in the first drawing) is set to the front, and the moving direction of the movable platen 13 at the time of mold opening (in the first drawing is The left direction is set to the rear for explanation.

For example, as shown in Fig. 1, the mold clamping device 10 has a frame 11, a fixed platen 12, a movable platen 13, a rear platen 15, a tie rod 16, a toggle mechanism 20, and a mold clamping motor 26.

The fixed platen 12 is fixed to the frame 11. A fixed mold 32 is attached to the opposing surface of the fixed platen 12 and the movable platen 13.

The movable platen 13 is freely movable along a guide (e.g., a guide rail) 17 laid on the frame 11, and is movable forward and backward with respect to the fixed platen 12. A movable mold 33 is attached to the opposing surface of the movable platen 13 and the fixed platen 12.

By moving the movable platen 13 forward and backward with respect to the fixed platen 12, mold closing, mold clamping, and mold opening are performed. The mold device 30 is constituted by the fixed mold 32 and the movable mold 33.

The rear platen 15 is coupled to the fixed platen 12 via a plurality of (for example, four) tie bars 16, and is movably placed on the frame 11 in the mold opening and closing direction. In addition, the rear platen 15 can also move freely along the guides laid on the frame 11. The guide of the rear pressure plate 15 can also be connected to the guide of the movable pressure plate 13 17 shared.

Further, in the present embodiment, the fixed platen 12 is fixed to the frame 11, and the rear platen 15 is movable in the mold opening and closing direction with respect to the frame 11, but the platen 15 may be fixed to the frame 11 later, and the fixed platen 12 may be opened and closed with respect to the frame 11. The direction moves freely.

The tie rod 16 is parallel to the mold opening and closing direction and extends in accordance with the mold clamping force. A pressure detector 18 that detects a mold clamping force is provided on at least one of the tie bars 16. The pressure detector 18 detects the mold clamping force by detecting the deformation of the tie rod 16, and outputs a signal indicating the mold clamping force to the control device 70. The control device 70 performs feedback control so that the deviation between the detected value of the mold clamping force and the set value becomes zero.

The toggle mechanism 20 is disposed between the movable platen 13 and the rear platen 15 and is attached to the movable platen 13 and the rear platen 15, respectively. The movable platen 13 advances and retracts with respect to the rear platen 15 by the expansion and contraction of the toggle mechanism 20 in the mold opening and closing direction.

The mold clamping motor 26 is a driving portion that drives the movable platen 13 by driving the toggle mechanism 20. A ball screw mechanism is provided between the mold clamping motor 26 and the toggle mechanism 20, and the ball screw mechanism is transmitted to the motion converting portion of the toggle mechanism 20 as a linear motion that converts the rotational motion of the mold clamping motor 26.

The mold clamping motor 26 has an encoder 26a. The encoder 26a detects the rotation angle of the output shaft of the mold clamping motor 26, and outputs a signal indicating the rotation angle to the control device 70. The control device 70 performs feedback control so that the deviation between the detected value of the rotation angle and the set value becomes zero.

Next, the operation of the mold clamping device 10 will be described. Clamping device 10 The action is controlled by the control device 70. The control device 70 has a storage unit such as a memory and a CPU, and controls the operation of the mold clamping device 10 by executing a control program stored in the storage unit in the CPU.

In the mold closing process, the mold clamping motor 26 is driven to operate the toggle mechanism 20 and advance the movable platen 13. The movable mold 33 approaches the fixed mold 32.

In the mold clamping process, the mold clamping motor 26 is driven in a state where the movable mold 33 is in contact with the fixed mold 32, and the mold clamping force generated by the mold clamping motor 26 multiplied by the toggle ratio is generated. A cavity space 34 is formed between the fixed die 32 and the movable die 33 in the mold clamping state. In the mold clamping process, the filling process, the pressing process, the cooling process, and the metering process can be performed.

In the mold opening process, the mold clamping motor 26 is driven to operate the toggle mechanism 20 and the movable platen 13 is retracted. The roll-out process can then be carried out.

Further, the mold clamping device 10 may have a hydraulic cylinder instead of the mold clamping motor 26 as a driving portion of the movable platen 13. Further, the mold clamping device 10 has a linear motor for mold opening and closing, and may have an electromagnet for mold clamping. The pressure detector 18 is not limited to the strain gauge, and may be a piezoelectric type, a capacity type, a hydraulic type, an electromagnetic type or the like, and the mounting position is not limited to the tie rod 16.

Next, the injection device 50 will be described with reference to Fig. 1 again. In the description of the injection device 50, unlike the description of the mold clamping device 10, the moving direction of the screw 52 at the time of filling (the left direction in the first drawing) is set to the front, and the moving direction of the screw 52 at the time of measurement (the first) In the figure, the right direction is set to the rear to be described.

The injection device 50 has a pressure cylinder 51, a screw 52, a metering motor 53, The motor 54 and the pressure detector 55 are injected.

The pressure cylinder 51 heats the molding material supplied from the supply port 51a. The supply port 51a is formed at the rear of the cylinder 51. A heating source such as a heater is provided on the outer circumference of the cylinder 51. A nozzle 59 is provided at the front end of the pressure cylinder 51.

The screw 52 is disposed in the cylinder 51 so as to be rotatable and freely retractable.

The metering motor 53 is a driving portion that rotates the screw 52. The metering motor 53 can have an encoder 53a. The encoder 53a detects the rotational speed of the output shaft of the metering motor 53, and outputs a signal indicating the rotational speed to the control device 70. The control device 70 can perform feedback control during the metering process so that the deviation between the detected value of the rotational speed and the set value becomes zero.

The injection motor 54 is a drive unit that advances and retracts the screw 52. A motion converting portion that converts the rotational motion of the injection motor 54 into a linear motion of the screw 52 is provided between the screw 52 and the injection motor 54. The injection motor 54 can have an encoder 54a. The encoder 54a detects the forward speed of the screw 52 by detecting the rotational speed of the output shaft of the injection motor 54, and outputs a signal indicating the forward speed of the screw 52 to the control device 70. The control device 70 can perform feedback control during the filling process so that the deviation between the detected value of the forward speed of the screw 52 and the set value becomes zero.

The pressure detector 55 is disposed, for example, between the injection motor 54 and the screw 52, and outputs a signal corresponding to the pressure acting on the pressure detector 55 to the control device 70. The pressure acting on the pressure detector 55 corresponds to the back pressure of the screw 52, the pressure of the molding material pressed by the screw 52, and the like.

In the filling process, the injection motor 54 is driven to advance the screw 52, and the liquid molding material accumulated in front of the screw 52 is filled in the mold. The cavity space 34 of 30 is placed. The set value of the advance speed of the screw 52 may be constant, or may be changed depending on the screw position or the elapsed time. If the screw 52 is advanced to a predetermined position (so-called V/P switching position), the pressurization process is started. In addition, if the elapsed time after the start of the filling process reaches a predetermined time, the pressurization process can also be started.

In the holding process, the injection motor 54 is driven to push the screw 52 forward, and pressure is applied to the molding material in the cavity space 34. Can add insufficient forming materials. The set value of the pressure of the forming material may be constant, or may be gradually changed depending on the elapsed time or the like. The inlet of the cavity space 34 (so-called gate) is sealed, and after the backflow of the molding material from the cavity space 34 is prevented, the cooling process is started. The metering process can be performed during the cooling process.

In the metering process, the metering motor 53 is driven to rotate the screw 52, and the molding material is sent to the front along a spiral groove formed in the screw 52. The forming material is gradually melted. As the liquid molding material is sent to the front of the screw 52 and accumulated in the front portion of the cylinder 51, the screw 52 is forced to retreat. The set value of the rotational speed of the screw 52 can be constant, or can be changed depending on the screw position or the elapsed time.

In the metering process, in order to restrict the screw 52 from retreating abruptly, the injection motor 54 can be driven to apply a back pressure to the screw 52. The injection motor 54 is driven to set the back pressure to a set value. When the screw 52 is retracted to a predetermined position and a predetermined amount of the molding material is accumulated in front of the screw 52, the measurement process is terminated.

Further, although the injection device of the present embodiment is a coaxial screw system, it may be a screw pre-molding method. The screw pre-molding injection device supplies the molding material melted in the plasticizing cylinder to the shooting cylinder, and the molding material is ejected The cylinder is ejected into the mold unit. A screw is disposed in the plasticizing cylinder so as to be freely rotatable and rotatable, and a plunger is disposed in the injection cylinder.

Next, the control device 70 and its peripheral devices will be described with reference to Fig. 2 . Fig. 2 is a view showing a control device and its peripheral devices according to an embodiment of the present invention.

The control device 70 includes, for example, a first control computing unit 71, a second control computing unit 72, and an inverter 73. The control device 70 is connected to the injection motor 54 and the pressure detector 55. The control amount is the pressure acting on the pressure detector 55, and the amount of operation is the electric power supplied to the injection motor 54.

The pressure detector 55 detects the pressure acting on the pressure detector 55. This pressure indicates the back pressure of the screw 52 and the pressure of the forming material urged by the screw 52. The pressure detector 55 has a strain gauge 56 as a detecting circuit, a first amplifier 57, and a second amplifier 58.

The strain gauge 56 constitutes a bridge circuit in which a plurality of resistance wires are combined. When the pressure acts on the bridge circuit, the respective resistance wires are deformed, and the resistance values of the respective resistance wires are changed. The voltage corresponding to the pressure is output from the bridge circuit. When the input voltage of the bridge circuit is constant, the output voltage of the bridge circuit is substantially proportional to the pressure acting on the bridge circuit.

The first amplifier 57 and the second amplifier 58 amplify the output voltages from the strain gauges 56, respectively, and output them to the control device 70. The gain of the first amplifier 57 is different from the gain of the second amplifier 58, and the pressure detector 55 outputs a plurality of pressure signals having different gains to the control device 70.

The pressure detector 55 has a plurality of amplifiers due to amplification from each The output of the pressure signal is different from the case where a plurality of variable signals are outputted by one variable amplifier in the past, and a plurality of pressure signals can be output at the same time. Therefore, it is possible to eliminate the problem that the gain is changed at the time of the change of the gain in the pressure detector 55 and the control device 70 as in the related art.

Further, the pressure detector 55 of the present embodiment has one bridge circuit and a plurality of amplifiers connected to the bridge circuit, but may have a combination of a plurality of bridge circuits and amplifiers. Further, the number of amplifiers included in the pressure detector 55 may be two or three or more. More than three pressure signals can be output from the pressure detector 55.

The control device 70 calculates the power supplied to the injection motor 54 for actual control based on a portion of the plurality of outputs selected from the pressure detector 55.

The first control calculation unit 71 calculates the electric power supplied to the injection motor 54 based on the first deviation of the output of the first amplifier 57 and the first pressure command. For example, as shown in Fig. 2, the first control computing unit 71 includes a first proportionalizer 71a that outputs a value proportional to the first deviation, and a first integrator 71b that outputs a time integral for the constant multiple of the first deviation. The value. The output A of the first control computing unit 71 is the sum of the output A1 of the first proportionalizer 71a and the output A2 of the first integrator 71b (A = A1 + A2). Further, the first control computing unit 71 may further include a first differentiator that outputs a value that temporally differentiates a constant multiple of the first deviation.

Similarly, the second control computing unit 72 calculates the electric power supplied to the injection motor 54 based on the second deviation of the output of the second amplifier 58 and the second pressure command. For example, as shown in FIG. 2, the second control computing unit 72 has The second proportionalizer 72a outputs a value proportional to the second deviation, and the second integrator 72b outputs a value obtained by integrating the constant multiple of the second deviation. The output B of the second control computing unit 72 is the sum of the output B1 of the second proportionalizer 72a and the output B2 of the second integrator 72b (B=B1+B2). Further, the second control computing unit 72 may further include a second differentiator that outputs a value that differentiates the constant multiple of the second deviation by time.

The first pressure command and the second pressure command may be the same or different.

The inverter 73 supplies electric power of the AC power source to the injection motor 54 in accordance with the output of the first control computing unit 71 or the output of the second control computing unit 72. Which of the outputs of the output of the first control computing unit 71 and the output of the second control computing unit 72 is determined according to the type of the process and the magnitude of the control amount.

However, the output voltage of the bridge circuit is substantially proportional to the pressure acting on the bridge circuit. However, there is a slight variation in the zero point and nonlinearity, and an error occurs in the output A of the first control computing unit 71 and the output B of the second control computing unit 72.

Therefore, the control device 70 causes the output A of the first control computing unit 71 to match the output B of the second control computing unit 72. Regardless of which of the plurality of outputs of the pressure detector 55 is used, the electric power supplied to the injection motor 54 is the same, and therefore the stability of the operation of the injection device 50 can be improved.

The output A and the second control of the first control computing unit 71 of the control device 70 One of the corrections in the output B of the system calculation unit 72 is not used.

When the control device 70 uses the output A of the first control computing unit 71, the output B of the second control computing unit 72 is corrected to match the output A of the first control computing unit 71. For example, the control device 70 does not obtain the output B2 of the second integrator 72b from the second deviation, but obtains it by the equation of B2=A-B1 and stores it in the memory of the second integrator 72b.

Similarly, when the control device 70 uses the output B of the second control computing unit 72, the output A of the first control computing unit 71 is corrected to match the output B of the second control computing unit 72. For example, the control device 70 does not obtain the output A2 of the first integrator 71b from the first deviation, but obtains it by the equation of A2=B-A1 and stores it in the memory of the first integrator 71b.

When the calculation of the operation amount includes the integral calculation, the control device 70 can make the operation amounts calculated in accordance with the respective outputs of the pressure detector 55 coincide by correcting the integral value.

The control device 70 can switch the output selected from the plurality of outputs of the pressure detector 55 in one molding cycle. The pressure acting on the pressure detector 55 in the metering process is much less than the pressure acting on the pressure detector 55 during the filling process, and the resolution of the pressure required in the metering process and the filling process is different. Therefore, the output from the amplifier with a larger gain is selected in the metrology process, and the output from the amplifier with a smaller gain is selected in the filling process.

Further, the pressure detector 55 of the present embodiment is of a strain gauge type, but may be a piezoelectric type, a capacity type or the like.

The embodiment of the injection molding machine has been described above, but this The invention is not limited to the above-described embodiments and the like, and various modifications and improvements can be made within the scope of the invention as set forth in the appended claims.

For example, although the pressure detector of the above embodiment detects the pressure of the injection device, it is also possible to detect the pressure of the mold clamping device (the clamping force acting on the mold device), the pushing force of the ejection device, and the like.

Further, although the amount of control in the above embodiment is pressure, it may be, for example, a position, a number of revolutions, or the like, and the detector for detecting the amount of control may be a position detector, a rotation speed detector, or the like.

Further, in the calculation device of the above-described embodiment, when the amount of operation is calculated, the amount of operation calculated based on each output of the detector is matched, but before the amount of operation is calculated, the amount of control indicated by each output of the detector may be used. Integration, so that the amount of operation calculated based on each output of the detector is consistent. For example, the control device calibrates the amount of control indicated by the remaining outputs to match the amount of control indicated by the output of one of the plurality of outputs selected from the detector. This correction is performed in accordance with a preset formula or the like. At this time, the number of control calculation units for calculating the operation amount may be one.

54‧‧‧Injection motor

55‧‧‧ Pressure detector

56‧‧‧Strain gauge

57‧‧‧1st amplifier

58‧‧‧2nd amplifier

70‧‧‧Control device

71‧‧‧1st Control Computing Department

71a‧‧‧1st scaler

71b‧‧‧1st integrator

72‧‧‧2nd Control Computing Department

72a‧‧‧2nd scaler

72b‧‧‧2nd integrator

73‧‧‧Inverter

Claims (8)

An injection molding machine characterized by comprising: a detector for outputting a plurality of signals corresponding to the control amount; and a control device for calculating the actual output according to a part of the plurality of outputs selected from the detectors The amount of operation. The injection molding machine according to claim 1, wherein the control device matches an operation amount calculated in accordance with each output of the detector. The injection molding machine according to claim 1 or 2, wherein the control device matches the operation amounts calculated in accordance with the respective outputs of the detectors when calculating the operation amount for actual control. The injection molding machine according to any one of claims 1 to 3, wherein the calculation of the operation amount includes an integral operation, and the control device calculates the operation based on the respective outputs of the detector by correcting the integral value. The amount is the same. The injection molding machine according to any one of claims 1 to 4, wherein the control device integrates the control amount indicated by each output of the detector before calculating the operation amount, thereby The calculated amount of operation is the same for each output of the detector. The injection as described in any one of claims 1 to 5 And the control device corrects an operation amount calculated using the remaining outputs to match an operation amount calculated according to one of the plurality of outputs selected from the detectors. The injection molding machine according to any one of claims 1 to 6, wherein the detector has a plurality of amplifiers for amplifying and outputting signals, and the control device is based on a partial amplifier selected from a plurality of amplifiers. The output is used to calculate the amount of operation for actual control, and the amount of operation calculated based on the output of each amplifier is made uniform. The injection molding machine according to any one of claims 1 to 7, wherein the control device switches the output of the plurality of outputs selected from the detectors in one molding cycle.