Control device for injection molding machine, injection molding machine, and control method for injection molding machine

Abstract

The present invention relates to a control device of an injection molding machine, an injection molding machine, and a control method of an injection molding machine, which reduces power consumption in a holding process and simplifies control operation in the holding process. The control device is a control device of an injection molding machine having an injection unit and an injection drive source. The control device has an injection control section that controls the injection drive source in a holding process of controlling pressure of a molding material applied by the injection unit, based on a set value of the pressure and an actual value of the pressure. The injection control section uses a value obtained by subtracting the set value of the pressure over time instead of the set value of the pressure, or uses a value obtained by adding the actual value of the pressure over time instead of the actual value of the pressure, to gradually reduce the actual value of the pressure with respect to the set value of the pressure.

Description

Technical Field

[0001] This application claims priority based on Japanese Patent Application No. 2022-148559, filed on September 16, 2022. The entire contents of that Japanese application are incorporated herein by reference.

[0002] This invention relates to a control device for an injection molding machine, an injection molding machine, and a control method for an injection molding machine. Background Technology

[0003] Patent Document 1 describes an injection molding machine comprising a screw that pushes the molding material, an injection motor that moves the screw, and a control device that controls the injection motor. In the pressure holding process, which controls the pressure exerted on the molding material by the screw, the control device limits the input to the injection motor according to a pressure setting mode to reduce the power consumption of the injection motor. The pressure setting mode is set to reduce the pressure from a first moment to a second moment. The specific structure of the control device is not disclosed in Patent Document 1, but a conventional control device consists of multiple components such as a subtraction unit, an addition unit, and a compensation unit (for example, see Patent Document 2).

[0004] Patent Document 1: Japanese Patent No. 4266224

[0005] Patent Document 2: Japanese Patent Application Publication No. 2001-252957

[0006] Patent Document 1 describes a method for limiting the input to the injection motor according to a pressure setting mode during the pressure holding process to reduce the power consumption of the injection motor, but it does not disclose the specific structure of the control device. Typically, a control device consists of multiple components such as a subtraction unit, an addition unit, and a compensation unit (see Patent Document 2). Therefore, from the viewpoint of simplifying control calculations, the structure of the control device can be improved. Summary of the Invention

[0007] One aspect of the present invention provides a technique for reducing power consumption in the pressure holding process and simplifying control operations in the pressure holding process.

[0008] One aspect of the present invention relates to a control device for an injection molding machine comprising an injection component that pushes molding material and an injection drive source that moves the injection component. The control device includes an injection control unit that, in a pressure holding process that controls the pressure acting on the molding material from the injection component, controls the injection drive source based on a set pressure value and the actual pressure value. The injection control unit replaces the set pressure value with a value obtained by subtracting it from the set pressure value over time, so that the actual pressure value gradually decreases relative to the set pressure value; or it replaces the actual pressure value with a value obtained by adding it to the actual pressure value over time, so that the actual pressure value gradually decreases relative to the set pressure value.

[0009] The effects of the invention

[0010] According to one aspect of the present invention, power consumption in the pressure holding process can be reduced, and control operations in the pressure holding process can be simplified. Attached Figure Description

[0011] Figure 1 This is a diagram showing the state of an injection molding machine at the end of mold opening according to one embodiment.

[0012] Figure 2 This is a diagram showing the state of the injection molding machine during mold closing according to one embodiment.

[0013] Figure 3 This is a diagram illustrating an example of how function blocks represent the components of a control device.

[0014] Figure 4 This is a diagram illustrating an example of a process in the molding cycle.

[0015] Figure 5 This is a diagram illustrating the change in the dimensions of the molding material over time during the holding pressure process, and the change in the pressure exerted on the molding material from the injection unit over time during the holding pressure process.

[0016] Figure 6 This is an example of a screen showing the pressure setting during the pressure holding process.

[0017] Figure 7 This is a diagram showing the injection control unit according to the first embodiment.

[0018] Figure 8 This is a diagram showing the injection control unit involved in the second embodiment.

[0019] Figure 9 This is a diagram showing the injection control unit according to the third embodiment.

[0020] Figure 10 This is a diagram showing the injection control unit according to the fourth embodiment.

[0021] Figure 11 This is a diagram showing the injection control unit involved in the reference example.

[0022] Explanation of symbols

[0023] 10-Injection molding machine, 330-Screw (injection component), 350-Injection motor (injection drive source), 700-Control device, 713-Injection control unit, 800-Mold device. Detailed Implementation

[0024] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, in the drawings, the same or corresponding structures are sometimes labeled with the same symbols, and descriptions are omitted.

[0025] (Injection molding machine)

[0026] Figure 1 This is a diagram showing the state of an injection molding machine at the end of mold opening according to one embodiment.

[0027] Figure 2 This diagram illustrates the mold-closing state of an injection molding machine according to one embodiment. In this specification, the X-axis, Y-axis, and Z-axis are mutually perpendicular directions. The X-axis and Y-axis represent horizontal directions, and the Z-axis represents vertical directions. When the mold-closing device 100 is horizontal, the X-axis represents the mold opening and closing direction, and the Y-axis represents the width direction of the injection molding machine 10. The negative side of the Y-axis is referred to as the operating side, and the positive side of the Y-axis is referred to as the opposite side of the operating side.

[0028] like Figures 1-2 As shown, the injection molding machine 10 includes: a mold clamping device 100, a mold opening and closing device 800; an ejection device 200 for ejecting the molded article formed by the mold device 800; an injection device 300 for injecting molding material into the mold device 800; a moving device 400 for moving the injection device 300 forward and backward relative to the mold device 800; a control device 700 for controlling the various components of the injection molding machine 10; and a frame 900 for supporting the various components of the injection molding machine 10. The frame 900 includes a mold clamping device frame 910 supporting the mold clamping device 100 and an injection device frame 920 supporting the injection device 300. The mold clamping device frame 910 and the injection device frame 920 are respectively mounted on the base plate 2 via horizontal adjusting casters 930. The control device 700 is arranged in the internal space of the injection device frame 920. The various components of the injection molding machine 10 will be described below.

[0029] (Mold closing device)

[0030] In the description of the mold closing device 100, the moving direction of the movable pressure plate 120 when the mold is closed (e.g., the positive X-axis direction) is set to forward, and the moving direction of the movable pressure plate 120 when the mold is opened (e.g., the negative X-axis direction) is set to rearward.

[0031] The mold closing device 100 performs mold closing, pressurization, mold closing, depressurization, and mold opening of the mold device 800. The mold device 800 includes a fixed mold 810 and a moving mold 820.

[0032] The mold closing device 100 is, for example, horizontal, and the mold opening and closing direction is horizontal. The mold closing device 100 has a fixed pressure plate 110 for mounting the fixed mold 810, a movable pressure plate 120 for mounting the moving mold 820, and a moving mechanism 102 for moving the movable pressure plate 120 relative to the fixed pressure plate 110 in the mold opening and closing direction.

[0033] The fixed pressure plate 110 is fixed relative to the mold closing device frame 910. The fixed mold 810 is installed on the surface of the fixed pressure plate 110 opposite to the movable pressure plate 120.

[0034] The movable pressure plate 120 is configured to move freely relative to the mold clamping device frame 910 in the mold opening and closing direction. A guide member 101 for guiding the movable pressure plate 120 is laid on the mold clamping device frame 910. A movable mold 820 is mounted on the surface of the movable pressure plate 120 opposite to the fixed pressure plate 110.

[0035] The moving mechanism 102 performs mold closing, pressurization, mold clamping, demolding, and mold opening of the mold device 800 by moving the movable pressure plate 120 forward and backward relative to the fixed pressure plate 110. The moving mechanism 102 includes an toggle seat 130 spaced apart from the fixed pressure plate 110, a connecting rod 140 connecting the fixed pressure plate 110 and the toggle seat 130, an toggle mechanism 150 that moves the movable pressure plate 120 relative to the toggle seat 130 in the mold opening and closing direction, a mold clamping motor 160 that operates the toggle mechanism 150, a motion conversion mechanism 170 that converts the rotational motion of the mold clamping motor 160 into linear motion, and a mold thickness adjustment mechanism 180 that adjusts the distance between the fixed pressure plate 110 and the toggle seat 130.

[0036] The toggle seat 130 is spaced apart from the fixed pressure plate 110 and is mounted on the mold clamping device frame 910 so as to move freely in the mold opening and closing direction. Furthermore, the toggle seat 130 can be configured to move freely along a guide laid on the mold clamping device frame 910. The guide of the toggle seat 130 can be interchangeable with the guide 101 of the movable pressure plate 120.

[0037] In addition, in this embodiment, the fixed pressure plate 110 is fixed relative to the mold clamping device frame 910, and the toggle seat 130 is configured to move freely relative to the mold clamping device frame 910 in the mold opening and closing direction. However, it is also possible that the toggle seat 130 is fixed relative to the mold clamping device frame 910, and the fixed pressure plate 110 is configured to move freely relative to the mold clamping device frame 910 in the mold opening and closing direction.

[0038] Connecting rod 140 connects the fixed pressure plate 110 and the toggle seat 130 at a distance L in the mold opening and closing direction. Multiple connecting rods 140 can be used (e.g., four). The multiple connecting rods 140 are configured parallel to the mold opening and closing direction and extend according to the clamping force. A connecting rod strain detector 141 for detecting the strain of the connecting rod 140 can be provided on at least one connecting rod 140. The connecting rod strain detector 141 sends a signal indicating its detection result to the control device 700. The detection result of the connecting rod strain detector 141 is used for detecting the clamping force, etc.

[0039] In this embodiment, a connecting rod strain gauge 141 is used as the clamping force detector for detecting the clamping force, but the present invention is not limited to this. The clamping force detector is not limited to a strain gauge and may also be piezoelectric, capacitive, hydraulic, or electromagnetic, etc., and its installation position is not limited to the connecting rod 140.

[0040] A toggle mechanism 150 is positioned between a movable pressure plate 120 and a toggle seat 130, allowing the movable pressure plate 120 to move relative to the toggle seat 130 in the mold opening and closing direction. The toggle mechanism 150 has a crosshead 151 that moves in the mold opening and closing direction and a pair of linkages that extend and retract with the movement of the crosshead 151. Each linkage has a first linkage 152 and a second linkage 153 connected by pins or the like, allowing for free extension and retraction. The first linkage 152 is mounted by pins or the like to allow for free oscillation relative to the movable pressure plate 120. The second linkage 153 is mounted by pins or the like to allow for free oscillation relative to the toggle seat 130. The second linkage 153 is mounted to the crosshead 151 via a third linkage 154. When the crosshead 151 moves forward or backward relative to the toggle seat 130, the first linkage 152 and the second linkage 153 extend and retract, causing the movable pressure plate 120 to move forward or backward relative to the toggle seat 130.

[0041] Furthermore, the structure of the toggle mechanism 150 is not limited to... Figure 1 and Figure 2 The structure shown. For example, in Figure 1 and Figure 2 In this configuration, each link group has 5 nodes, but it can be 4, or it can be the node where one end of the third link 154 is connected to the first link 152 and the second link 153.

[0042] The clamping motor 160 is mounted on the toggle seat 130 and operates the toggle mechanism 150. The clamping motor 160 moves the crosshead 151 forward and backward relative to the toggle seat 130, causing the first link 152 and the second link 153 to extend and retract, thereby moving the movable pressure plate 120 forward and backward relative to the toggle seat 130. The clamping motor 160 is directly connected to the motion conversion mechanism 170, but it can also be connected to the motion conversion mechanism 170 via a belt, pulley, etc.

[0043] The motion conversion mechanism 170 converts the rotary motion of the mold clamping motor 160 into the linear motion of the crosshead 151. The motion conversion mechanism 170 includes a lead screw shaft and a lead screw nut screwed to the lead screw shaft. Balls or rollers may be located between the lead screw shaft and the lead screw nut.

[0044] Under the control of the control device 700, the mold closing device 100 performs the mold closing process, the pressure raising process, the mold closing process, the pressure release process, and the mold opening process.

[0045] In the mold closing process, the mold closing motor 160 is driven to advance the crosshead 151 to the mold closing end position at a set speed, causing the movable pressure plate 120 to advance so that the moving mold 820 contacts the fixed mold 810. For example, a mold closing motor encoder 161 is used to detect the position and speed of the crosshead 151. The mold closing motor encoder 161 detects the rotation of the mold closing motor 160 and sends a signal indicating its detection result to the control device 700.

[0046] Furthermore, the crosshead position detector for detecting the position of the crosshead 151 and the crosshead movement speed detector for detecting the movement speed of the crosshead 151 are not limited to the mold clamping motor encoder 161; conventional detectors can be used. Similarly, the movable platen position detector for detecting the position of the movable platen 120 and the movable platen movement speed detector for detecting the movement speed of the movable platen 120 are not limited to the mold clamping motor encoder 161; conventional detectors can be used.

[0047] In the pressurization process, the mold clamping motor 160 is further driven to advance the crosshead 151 from the mold closing end position to the mold closing position, thereby generating a mold clamping force.

[0048] During the mold closing process, the mold closing motor 160 is driven to maintain the position of the crosshead 151 in the mold closing position. During the mold closing process, the mold closing force generated during the pressurization process is maintained. During the mold closing process, a cavity space 801 (see reference) is formed between the moving mold 820 and the fixed mold 810. Figure 2 The injection unit 300 fills the cavity space 801 with liquid molding material. The filled molding material is then cured to obtain a molded product.

[0049] The number of cavity spaces 801 can be one or more. In the latter case, multiple molded articles can be obtained simultaneously. An insert can be configured in a part of the cavity space 801, and the other part of the cavity space 801 can be filled with molding material. A molded article in which the insert and the molding material are integrated can be obtained.

[0050] During the depressurization process, the crosshead 151 is retracted from the mold-closing position to the mold-opening start position by driving the mold-closing motor 160, thereby causing the movable pressure plate 120 to retract and reducing the mold-closing force. The mold-opening start position and the mold-closing end position can be the same position.

[0051] In the mold opening process, the crosshead 151 is retracted from the mold opening start position to the mold opening end position at a set moving speed by driving the mold closing motor 160, causing the movable pressure plate 120 to retract, so that the moving mold 820 separates from the fixed mold 810. Then, the ejector device 200 ejects the molded product from the moving mold 820.

[0052] The setting conditions in the mold closing process, the pressure raising process, and the mold closing process are set uniformly as a series of setting conditions. For example, the moving speed, position (including the mold closing start position, moving speed switching position, mold closing end position, and mold closing position) and mold closing force of the crosshead 151 in the mold closing process and the pressure raising process are set uniformly as a series of setting conditions. The mold closing start position, moving speed switching position, mold closing end position, and mold closing position are arranged sequentially from back to front, and represent the start and end points of the range for setting the moving speed. The moving speed is set for each range. There can be one or more moving speed switching positions. The moving speed switching position can be omitted. Only the mold closing position and the mold closing force can be set.

[0053] The settings for the depressurization and mold opening processes are also set in the same way. For example, the moving speed and position (mold opening start position, moving speed switching position, and mold opening end position) of the crosshead 151 in the depressurization and mold opening processes are set uniformly as a series of settings. The mold opening start position, moving speed switching position, and mold opening end position are arranged sequentially from front to back, and represent the start and end points of the range for setting the moving speed. The moving speed is set for each range. There can be one or more moving speed switching positions. A moving speed switching position may not be set. The mold opening start position and the mold closing end position can be the same position. Furthermore, the mold opening end position and the mold closing start position can be the same position.

[0054] In addition, the moving speed and position of the movable pressure plate 120 can be set instead of the moving speed and position of the crosshead 151. Furthermore, the clamping force can be set instead of the position of the crosshead (e.g., the mold closing position) and the position of the movable pressure plate.

[0055] However, the toggle mechanism 150 amplifies the driving force of the clamping motor 160 and transmits it to the movable pressure plate 120. This amplification factor is also known as the toggle ratio. The toggle ratio varies depending on the angle θ (hereinafter also referred to as "link angle θ") formed by the first link 152 and the second link 153. The link angle θ is determined by the position of the crosshead 151. The toggle ratio reaches its maximum when the link angle θ is 180°.

[0056] When the thickness of the mold assembly 800 changes due to replacement of the mold assembly 800, temperature changes of the mold assembly 800, etc., mold thickness adjustment is performed to obtain the specified mold closing force during mold closing. In mold thickness adjustment, for example, the distance L between the fixed pressure plate 110 and the toggle seat 130 is adjusted so that at the moment of mold contact when the moving mold 820 contacts the fixed mold 810, the connecting rod angle θ of the toggle mechanism 150 becomes the specified angle.

[0057] The mold clamping device 100 includes a mold thickness adjustment mechanism 180. The mold thickness adjustment mechanism 180 adjusts the distance L between the fixed pressure plate 110 and the toggle seat 130, thereby adjusting the mold thickness. Furthermore, the timing of the mold thickness adjustment is, for example, during the period from the end of the molding cycle to the start of the next molding cycle. The mold thickness adjustment mechanism 180 includes, for example: a lead screw shaft 181 formed at the rear end of the connecting rod 140; a lead screw nut 182 held in the toggle seat 130 for free rotation and immobility; and a mold thickness adjustment motor 183 that rotates the lead screw nut 182 screwed to the lead screw shaft 181.

[0058] Each connecting rod 140 is provided with a lead screw shaft 181 and a lead screw nut 182. The rotational driving force of the die thickness adjustment motor 183 can be transmitted to multiple lead screw nuts 182 via the rotational driving force transmission unit 185. Multiple lead screw nuts 182 can be rotated synchronously. In addition, by changing the transmission path of the rotational driving force transmission unit 185, multiple lead screw nuts 182 can also be rotated individually.

[0059] The rotary drive force transmission unit 185 is composed of, for example, gears. In this case, driven gears are formed on the outer periphery of each lead screw nut 182, drive gears are mounted on the output shaft of the die thickness adjustment motor 183, and intermediate gears that mesh with multiple driven gears and drive gears are kept rotatably in the center of the toggle seat 130. Alternatively, instead of gears, the rotary drive force transmission unit 185 may also be composed of belts, pulleys, etc.

[0060] The operation of the die thickness adjustment mechanism 180 is controlled by the control device 700. The control device 700 drives the die thickness adjustment motor 183 to rotate the lead screw nut 182. As a result, the position of the toggle seat 130 relative to the connecting rod 140 is adjusted, and the distance L between the fixed pressure plate 110 and the toggle seat 130 is adjusted. Alternatively, multiple die thickness adjustment mechanisms can be used in combination.

[0061] The die thickness adjustment motor encoder 184 is used to detect the interval L. The die thickness adjustment motor encoder 184 detects the rotation amount and direction of the die thickness adjustment motor 183 and sends a signal indicating the detection result to the control device 700. The detection result of the die thickness adjustment motor encoder 184 is used for monitoring and controlling the position and interval L of the toggle seat 130. However, the toggle seat position detector for detecting the position of the toggle seat 130 and the interval detector for detecting the interval L are not limited to the die thickness adjustment motor encoder 184; conventional detectors can be used.

[0062] The mold clamping device 100 may have a mold temperature regulator for adjusting the temperature of the mold assembly 800. The mold assembly 800 has a flow path for a temperature regulating medium inside it. The mold temperature regulator adjusts the temperature of the temperature regulating medium supplied to the flow path of the mold assembly 800, thereby regulating the temperature of the mold assembly 800.

[0063] In addition, the mold closing device 100 in this embodiment is a horizontal type with the mold opening and closing direction in the horizontal direction, but it can also be a vertical type with the mold opening and closing direction in the vertical direction.

[0064] Furthermore, the mold clamping device 100 of this embodiment includes a mold clamping motor 160 as a drive unit, but a hydraulic cylinder may be used instead of the mold clamping motor 160. Also, the mold clamping device 100 includes a linear motor for mold opening and closing, and may also include an electromagnet for mold clamping.

[0065] (Ejection device)

[0066] In the description of the ejector device 200, similar to the description of the mold closing device 100, the moving direction of the movable pressure plate 120 when the mold is closed (e.g., the positive X-axis direction) is set to forward, and the moving direction of the movable pressure plate 120 when the mold is opened (e.g., the negative X-axis direction) is set to rearward.

[0067] Ejection device 200 is mounted on movable pressure plate 120 and moves forward and backward together with movable pressure plate 120. Ejection device 200 includes: ejection rod 210 for ejecting molded article from mold device 800; and drive mechanism 220 for moving ejection rod 210 along the moving direction (X-axis direction) of movable pressure plate 120.

[0068] Ejector rod 210 is configured to move freely in and out of the through hole in movable pressure plate 120. The front end of ejector rod 210 contacts ejector plate 826 of moving mold 820. The front end of ejector rod 210 may or may not be connected to ejector plate 826.

[0069] The drive mechanism 220 includes, for example, an ejector motor and a motion conversion mechanism that converts the rotational motion of the ejector motor into the linear motion of the ejector rod 210. The motion conversion mechanism includes a lead screw and a lead screw nut screwed to the lead screw. Balls or rollers may be located between the lead screw and the lead screw nut.

[0070] The ejection device 200 performs the ejection process under the control of the control device 700. In the ejection process, the ejector rod 210 is moved forward from the standby position to the ejection position at a set speed, causing the ejector plate 826 to move forward and eject the molded product. Then, the ejection motor is driven to move the ejector rod 210 backward at a set speed, causing the ejector plate 826 to return to the original standby position.

[0071] For example, an ejector motor encoder is used to detect the position and speed of the ejector rod 210. The ejector motor encoder detects the rotation of the ejector motor and sends a signal indicating its detection result to the control device 700. In addition, the ejector rod position detector for detecting the position of the ejector rod 210 and the ejector rod speed detector for detecting the speed of the ejector rod 210 are not limited to the ejector motor encoder, and conventional detectors can be used.

[0072] (Injection device)

[0073] In the description of the injection device 300, unlike the description of the mold clamping device 100 and the description of the ejection device 200, the direction of movement of the screw 330 during filling (e.g., the negative X-axis direction) is set to forward, and the direction of movement of the screw 330 during metering (e.g., the positive X-axis direction) is set to rearward.

[0074] An injection unit 300 is mounted on a sliding base 301, which is configured to move freely forward and backward relative to the injection unit frame 920. The injection unit 300 is also configured to move freely forward and backward relative to the mold assembly 800. The injection unit 300 contacts the mold assembly 800 and fills the cavity space 801 within the mold assembly 800 with molding material. The injection unit 300 includes, for example, a cylinder 310 for heating the molding material, a nozzle 320 disposed at the front end of the cylinder 310, a screw 330 configured to move freely forward and backward and rotate freely within the cylinder 310, a metering motor 340 for rotating the screw 330, an injection motor 350 for moving the screw 330 forward and backward, and a load detector 360 for detecting the load transmitted between the injection motor 350 and the screw 330.

[0075] The cylinder body 310 heats the molding material supplied to it from the supply port 311. The molding material includes, for example, resin. The molding material is formed in granular form and supplied to the supply port 311 in a solid state. The supply port 311 is formed at the rear of the cylinder body 310. A cooler 312, such as a water-cooled cylinder, is provided on the outer periphery of the rear of the cylinder body 310. A first heater 313, such as a belt heater, and a first temperature detector 314 are provided on the outer periphery of the cylinder body 310, further forward than the cooler 312.

[0076] The cylinder block 310 is divided into multiple regions along its axial direction (e.g., the X-axis direction). A first heater 313 and a first temperature detector 314 are respectively provided in each of the multiple regions. A set temperature is set for each of the multiple regions, and the control device 700 controls the first heater 313 so that the temperature detected by the first temperature detector 314 becomes the set temperature.

[0077] The nozzle 320 is located at the front end of the cylinder 310 and presses against the mold assembly 800. A second heater 323 and a second temperature detector 324 are provided on the outer periphery of the nozzle 320. The control device 700 controls the second heater 323 so that the detected temperature of the nozzle 320 becomes the set temperature.

[0078] The screw 330 is configured to rotate freely and move forward and backward within the cylinder 310. When the screw 330 is rotated, the molding material is conveyed forward along the spiral grooves of the screw 330. As the molding material is conveyed forward, it is gradually melted by heat from the cylinder 310. As the liquid molding material is conveyed forward and accumulates at the front of the cylinder 310, the screw 330 retracts. Then, when the screw 330 is moved forward, the liquid molding material accumulated at the front of the screw 330 is injected from the nozzle 320 and fills the mold assembly 800.

[0079] The check ring 331 is installed at the front of the screw 330 so that it can move freely forward and backward. The check ring 331 acts as a check valve to prevent the molding material from flowing backward from the front of the screw 330 when the screw 330 is pushed forward.

[0080] When the screw 330 is advanced, the check ring 331 is pushed backward by the pressure of the molding material in front of the screw 330, and retracts relative to the screw 330 to a closed position that blocks the flow path of the molding material (see reference). Figure 2 This prevents the molding material accumulated in front of the screw 330 from flowing backward.

[0081] On the other hand, when the screw 330 is rotated, the check ring 331 is pushed forward by the pressure of the molding material being conveyed forward along the spiral groove of the screw 330, and advances relative to the screw 330 to the open position where the flow path of the molding material is opened (see reference). Figure 1Thus, the molding material is conveyed to the front of the screw 330.

[0082] The check ring 331 can be either a cotransformer that rotates with the screw 330 or a non-cotransformer that does not rotate with the screw 330.

[0083] Additionally, the injection device 300 may have a drive source that moves the check ring 331 back and forth relative to the screw 330 between an open position and a closed position.

[0084] The metering motor 340 rotates the screw 330. The drive source for rotating the screw 330 is not limited to the metering motor 340; for example, it could be a hydraulic pump.

[0085] The injection motor 350 moves the screw 330 forward and backward. A motion conversion mechanism is provided between the injection motor 350 and the screw 330 to convert the rotational motion of the injection motor 350 into the linear motion of the screw 330. This motion conversion mechanism may include, for example, a lead screw shaft and a lead screw nut screwed to the lead screw shaft. Ball bearings, rollers, etc., may be provided between the lead screw shaft and the lead screw nut. The drive source for moving the screw 330 forward and backward is not limited to the injection motor 350; for example, it may be a hydraulic cylinder.

[0086] Load detector 360 detects the load transmitted between injection motor 350 and screw 330. The detected load is converted into pressure by control device 700. Load detector 360 is positioned along the load transmission path between injection motor 350 and screw 330, and detects the load acting on load detector 360.

[0087] The load detector 360 sends the detected load signal to the control device 700. The load detected by the load detector 360 is converted into the pressure acting between the screw 330 and the molding material, and is used for the control and monitoring of the back pressure of the screw 330 and the pressure acting from the screw 330 on the molding material.

[0088] Furthermore, the pressure detector for detecting the pressure of the molding material is not limited to the load detector 360; conventional detectors can be used. For example, a nozzle pressure sensor or a mold pressure sensor can be used. The nozzle pressure sensor is located at the nozzle 320. The mold pressure sensor is located inside the mold assembly 800.

[0089] The injection unit 300 performs metering, filling, and pressure holding processes under the control of the control unit 700. The filling and pressure holding processes can be collectively referred to as the injection process.

[0090] In the metering process, the metering motor 340 drives the screw 330 to rotate at a set speed, conveying the molding material forward along the spiral grooves of the screw 330. As a result, the molding material is gradually melted. As the molten molding material is conveyed forward of the screw 330 and accumulates at the front of the cylinder 310, the screw 330 retracts. For example, a metering motor encoder 341 is used to detect the rotational speed of the screw 330. The metering motor encoder 341 detects the rotation of the metering motor 340 and sends a signal indicating its detection result to the control device 700. However, the screw speed detector for detecting the rotational speed of the screw 330 is not limited to the metering motor encoder 341; conventional detectors can be used.

[0091] In the metering process, to limit the rapid retraction of the screw 330, the injection motor 350 can be driven to apply a set back pressure to the screw 330. For example, a load detector 360 can be used to detect the back pressure on the screw 330. If the screw 330 retracts to the metering end position and a specified amount of molding material accumulates in front of the screw 330, the metering process ends.

[0092] The position and speed of the screw 330 in the metering process are uniformly set as a series of preset conditions. For example, the metering start position, speed switching position, and metering end position are set. These positions are arranged sequentially from front to back and represent the start and end points of the set speed interval. The speed is set for each interval. There can be one or more speed switching positions. Alternatively, no speed switching position can be set. Furthermore, the back pressure is set for each interval.

[0093] In the filling process, the injection motor 350 is driven to advance the screw 330 at a set speed, filling the cavity space 801 within the mold assembly 800 with the liquid molding material accumulated in front of the screw 330. For example, an injection motor encoder 351 is used to detect the position and speed of the screw 330. The injection motor encoder 351 detects the rotation of the injection motor 350 and sends a signal indicating its detection result to the control device 700. If the screw 330 reaches the set position, a switch is made from the filling process to the holding pressure process (so-called V / P switching). The position where the V / P switching occurs is also called the V / P switching position. The set speed of the screw 330 can be changed according to the position of the screw 330, time, etc.

[0094] The position and moving speed of the screw 330 in the filling process are uniformly set as a series of preset conditions. For example, the filling start position (also called the "injection start position"), the moving speed switching position, and the V / P switching position are set. These positions are arranged sequentially from back to front and represent the start and end points of the set moving speed interval. The moving speed is set for each interval. There can be one or more moving speed switching positions. It is also possible not to set any moving speed switching positions.

[0095] The upper limit of the pressure of the screw 330 is set for each range of the screw 330's moving speed. The pressure of the screw 330 is detected by the load detector 360. When the pressure of the screw 330 is below the set pressure, the screw 330 moves forward at the set moving speed. On the other hand, when the pressure of the screw 330 exceeds the set pressure, in order to protect the mold, the screw 330 moves forward at a slower moving speed than the set moving speed, so that the pressure of the screw 330 falls below the set pressure.

[0096] Furthermore, during the filling process, after the screw 330 reaches the V / P switching position, it can be paused at the V / P switching position before the V / P switch is performed. Alternatively, instead of stopping the screw 330, it can be moved forward or backward at a slight speed before the V / P switch is about to occur. Moreover, the screw position detector for detecting the position of the screw 330 and the screw speed detector for detecting the movement speed of the screw 330 are not limited to the injection motor encoder 351; conventional detectors can be used.

[0097] During the holding pressure process, the injection motor 350 pushes the screw 330 forward, maintaining the pressure of the molding material at the front end of the screw 330 (hereinafter also referred to as "holding pressure") at a set pressure, and pushing the remaining molding material in the cylinder 310 towards the mold assembly 800. This replenishes any insufficient molding material in the mold assembly 800 due to cooling shrinkage. For example, a load detector 360 is used to detect the holding pressure. The set value of the holding pressure can be changed according to the elapsed time since the start of the holding pressure process. The holding pressure and the holding time for each of the multiple holding pressure processes can be set separately, or they can be set uniformly as a series of setting conditions.

[0098] During the holding pressure process, the molding material in the cavity space 801 within the mold assembly 800 is gradually cooled. At the end of the holding pressure process, the inlet of the cavity space 801 is blocked by the solidified molding material. This state is called gate sealing, which prevents the backflow of molding material from the cavity space 801. After the holding pressure process, the cooling process begins. During the cooling process, the molding material within the cavity space 801 solidifies. To shorten the molding cycle time, a metering process can be performed during the cooling process.

[0099] Furthermore, the injection device 300 in this embodiment is a coaxial screw type, but it can also be a pre-plasticizing type, etc. In a pre-plasticizing type injection device, molten molding material in a plasticizing cylinder is supplied to the injection cylinder, and the molding material is injected from the injection cylinder into the mold device. In the plasticizing cylinder, the screw is configured to rotate freely but not retract, or the screw is configured to rotate freely and retract freely. On the other hand, in the injection cylinder, the plunger is configured to retract freely.

[0100] Furthermore, the injection device 300 in this embodiment is horizontal with the cylinder 310's axis in the horizontal direction, but it can also be vertical with the cylinder 310's axis in the vertical direction. The mold clamping device combined with the vertical injection device 300 can be either vertical or horizontal. Similarly, the mold clamping device combined with the horizontal injection device 300 can be either horizontal or vertical.

[0101] (Mobile device)

[0102] In the description of the moving device 400, similarly to the description of the injection device 300, the direction of movement of the screw 330 during filling (e.g., the negative X-axis direction) is set to forward, and the direction of movement of the screw 330 during metering (e.g., the positive X-axis direction) is set to rearward.

[0103] The moving device 400 causes the injection device 300 to move forward and backward relative to the mold device 800. Furthermore, the moving device 400 presses the nozzle 320 relative to the mold device 800 to generate nozzle contact pressure. The moving device 400 includes a hydraulic pump 410, a motor 420 as a drive source, and a hydraulic cylinder 430 as a hydraulic actuator.

[0104] The hydraulic pump 410 has a first port 411 and a second port 412. The hydraulic pump 410 is a bidirectional rotating pump, generating hydraulic pressure by switching the rotation direction of the motor 420, drawing in working fluid (e.g., oil) from either the first port 411 or the second port 412 and discharging it from the other port. Alternatively, the hydraulic pump 410 can also draw working fluid from a tank and discharge working fluid from either the first port 411 or the second port 412.

[0105] Motor 420 operates hydraulic pump 410. Motor 420 drives hydraulic pump 410 by means of rotational direction and torque corresponding to control signals from control device 700. Motor 420 can be an electric motor or an electric servo motor.

[0106] The hydraulic cylinder 430 has a cylinder body 431, a piston 432, and a piston rod 433. The cylinder body 431 is fixed relative to the injection device 300. The piston 432 divides the interior of the cylinder body 431 into a front chamber 435, which is a first chamber, and a rear chamber 436, which is a second chamber. The piston rod 433 is fixed relative to the fixed pressure plate 110.

[0107] The front chamber 435 of the hydraulic cylinder 430 is connected to the first port 411 of the hydraulic pump 410 via a first flow path 401. Working fluid ejected from the first port 411 is supplied to the front chamber 435 via the first flow path 401, thereby propelling the injection device 300 forward. As the injection device 300 advances, the nozzle 320 is pressed against the fixed mold 810. The front chamber 435 functions as a pressure chamber, generating the nozzle contact pressure of the nozzle 320 through the pressure of the working fluid supplied from the hydraulic pump 410.

[0108] On the other hand, the rear chamber 436 of the hydraulic cylinder 430 is connected to the second port 412 of the hydraulic pump 410 via the second flow path 402. The working fluid ejected from the second port 412 is supplied to the rear chamber 436 of the hydraulic cylinder 430 via the second flow path 402, thereby pushing the injection device 300 backward. The injection device 300 retracts and the nozzle 320 separates from the fixed mold 810.

[0109] In addition, in this embodiment, the moving device 400 includes a hydraulic cylinder 430, but the present invention is not limited thereto. For example, instead of the hydraulic cylinder 430, an electric motor and a motion conversion mechanism that converts the rotational motion of the electric motor into the linear motion of the injection device 300 may also be used.

[0110] (Control device)

[0111] The control device 700 is, for example, composed of a computer, such as Figures 1-2 As shown, the device includes a CPU (Central Processing Unit) 701, a storage medium 702 such as a memory, an input interface 703, and an output interface 704. The control device 700 performs various controls by having the CPU 701 execute a program stored in the storage medium 702. Furthermore, the control device 700 receives signals from external sources through the input interface 703 and sends signals to external sources through the output interface 704.

[0112] The control device 700 repeatedly manufactures molded products by repeatedly performing metering, mold closing, pressurizing, mold closing, filling, pressure holding, cooling, depressurizing, mold opening, and ejection processes. The series of actions used to obtain the molded product, such as the actions from the start of the metering process to the start of the next metering process, is also called "material injection" or "molding cycle." Furthermore, the time required for one material injection is also called "molding cycle time" or "cycle time."

[0113] A typical molding cycle may include, for example, the following steps in sequence: metering, mold closing, pressure increase, mold closing, filling, pressure holding, cooling, pressure release, mold opening, and ejection. This sequence refers to the order in which each step begins. The filling, pressure holding, and cooling steps occur during the mold closing step. Alternatively, the start of the mold closing step can coincide with the start of the filling step. The end of the pressure release step can coincide with the start of the mold opening step.

[0114] Furthermore, to shorten the molding cycle time, multiple processes can be performed simultaneously. For example, the metering process can be performed during the cooling process of the previous molding cycle or during the mold closing process. In this case, the mold closing process can be set to be performed at the very beginning of the molding cycle. The filling process can also begin during the mold closing process. Furthermore, the ejection process can begin during the mold opening process. When an on / off valve is provided for the flow path of the nozzle 320, the mold opening process can begin during the metering process. This is because even if the mold opening process begins during the metering process, as long as the on / off valve closes the flow path of the nozzle 320, the molding material will not leak from the nozzle 320.

[0115] In addition, a single molding cycle can include processes other than metering, mold closing, pressurization, mold closing, filling, pressure holding, cooling, depressurization, mold opening, and ejection.

[0116] For example, a pre-metering backfeeding process can be performed after the pressure holding process ends and before the metering process begins, causing the screw 330 to retract to a pre-set metering start position. This reduces the pressure of the molding material accumulated in front of the screw 330 before the metering process begins, thus preventing the screw 330 from retracting abruptly when the metering process begins.

[0117] Furthermore, a post-metering back suction process can be performed after the metering process is completed and before the filling process begins, retracting the screw 330 to a pre-set filling start position (also known as the "injection start position"). This reduces the pressure of the molding material accumulated in front of the screw 330 before the filling process begins, thus preventing leakage of the molding material from the nozzle 320 before the filling process begins.

[0118] The control device 700 is connected to the operation device 750, which receives user input, and the display device 760, which displays a screen. The operation device 750 and the display device 760 are, for example, composed of a touch panel 770, and can be integrated. The touch panel 770, as the display device 760, displays a screen under the control of the control device 700. Information such as the settings of the injection molding machine 10 and the current status of the injection molding machine 10 can be displayed on the screen of the touch panel 770. Furthermore, operation sections such as buttons and input fields for receiving user input can be displayed on the screen of the touch panel 770. The touch panel 770, as the operation device 750, detects user input on the screen and outputs a signal corresponding to the input operation to the control device 700. Thus, for example, the user can simultaneously check the information displayed on the screen and operate the operation sections on the screen to set the injection molding machine 10 (including inputting setting values). Furthermore, by operating the operation sections on the screen, the user can cause the injection molding machine 10 corresponding to the operation sections to operate. Furthermore, the operation of the injection molding machine 10 can include, for example, the operation (including stopping) of the mold clamping device 100, the ejection device 200, the injection device 300, the moving device 400, etc. Also, the operation of the injection molding machine 10 can include switching the screen displayed on the touch panel 770, which is a display device 760.

[0119] Furthermore, while the operation device 750 and display device 760 of this embodiment are integrated into a touch panel 770, they can also be provided independently. Additionally, multiple operation devices 750 can be provided. The operation device 750 and display device 760 are disposed on the operation side (negative Y-axis direction) of the mold clamping device 100 (more specifically, the fixed pressure plate 110).

[0120] (Detailed description of the control device)

[0121] Next, refer to Figure 3 An example of the constituent elements of the control device 700 will be described. Furthermore, Figure 3 The functional blocks illustrated are conceptual and do not necessarily need to be physically configured as shown. All or part of each functional block can be functionally or physically distributed / integrated in any unit. All or any part of the processing functions performed by each functional block can be implemented by a program executed by the CPU or by hardware based on wiring logic.

[0122] like Figure 3 As shown, the control device 700 includes, for example, a mold closing control unit 711, an ejection control unit 712, an injection control unit 713, a metering control unit 714, and a display control unit 715. The mold closing control unit 711 controls the mold closing device 100 and performs... Figure 4The diagram shows the mold closing process, pressure boosting process, mold closing process, pressure release process, and mold opening process. The ejection control unit 712 controls the ejection device 200 and performs the ejection process. The injection control unit 713 controls the injection drive source of the injection device 300 and performs the injection process. The injection drive source is, for example, an injection motor 350, but it could also be a hydraulic cylinder, etc. The injection process includes a filling process and a holding pressure process. The injection process is performed during the mold closing process. The metering control unit 714 controls the metering drive source of the injection device 300 and performs the metering process. The metering drive source is, for example, a metering motor 340, but it could also be a hydraulic pump, etc. The metering process is performed during the cooling process. The display control unit 715 controls the display device 760.

[0123] The filling process is a process of controlling the injection drive source in such a way that the actual value of the movement speed of the injection component disposed inside the cylinder 310 is a set value. The filling process is a process of filling the mold device 800 with liquid molding material (e.g., resin) accumulated in front of the injection component by moving the injection component forward. The injection component is, for example, a screw 330, but it can also be a plunger.

[0124] The movement speed of the injection unit is detected using a speed detector. The speed detector is, for example, an injection motor encoder 351. During the filling process, the injection unit advances, thereby increasing the pressure exerted by the injection unit on the molding material. The filling process, preceding the holding pressure process, may include a process that pauses the injection unit or a process that retracts the injection unit.

[0125] The holding pressure process is a process of controlling the injection drive source in a way that makes the actual value of the pressure acting on the molding material from the injection component a set value. The holding pressure process is a process of replenishing the amount of molding material in the mold assembly 800 that is insufficient due to cooling shrinkage by pushing the injection component forward. Pressure is detected using a pressure detector such as a load detector 360. A nozzle pressure sensor or a mold pressure sensor can be used as the pressure detector.

[0126] Next, refer to Figure 5 An example is given regarding the change in the dimensions of the molding material (e.g., resin) over time during the holding pressure process, and the change in the pressure (hereinafter also referred to as "pressure") exerted on the molding material from the injection unit over time during the holding pressure process. For example... Figure 5 As shown, during the pressure holding process, the resin cools and solidifies, and the resin shrinks (its size decreases). The shrinkage rate is expressed as (L0-L1) / L0. Here, L0 is the size before shrinkage, and L1 is the size after shrinkage.

[0127] As the resin cools and cures, the pressure required to prevent backflow gradually decreases. Therefore, maintaining a constant pressure from the beginning to the end of the holding pressure process can lead to excessive pressure from the middle of the process onwards, resulting in wasted electricity. Figure 5 As shown, if the pressure is reduced over time starting from the middle of the pressure holding process, power consumption will be reduced.

[0128] Here, it is possible to divide the pressure holding process into n (n is an integer greater than 2) processes and set the pressure for each process. However, if a smooth pressure reduction is desired, the number of divisions (n) would be too large, making the settings complex. Therefore, the injection control unit 713 is used in... Figure 6 The settings entered in the settings screen 761 shown are used to smoothly reduce stress.

[0129] Setting screen 761 is used, for example, to continuously reduce the actual pressure value from the middle of the pressure holding process to the end of the pressure holding process. In addition, when the pressure holding process is divided into n (n is an integer of 2 or more) processes, setting screen 761 can also be used to continuously reduce the pressure from the middle of the k-th process (k is an integer of 1 or more and n less) to the end of the k-th process.

[0130] The setting screen 761 is displayed on the display device 760 by the display control unit 715. The setting screen 761, for example, has a first input field 762 and a second input field 763. The first input field 762 is for input... Figure 5 The column showing the start time t1 of the pressure reduction is shown. The second input column, 763, is for input... Figure 5 The column showing the pressure P1 at the end of the pressure reduction at time t0 is shown.

[0131] While observing the setting screen 761, the operator inputs values ​​into the first input field 762 and the second input field 763. The start time t1 is entered, for example, as a percentage (%) relative to the end time t0. The start time t1 and end time t0 are entered with the start of the pressure holding process (or the start of the kth process) as a reference (zero). The pressure P1 at the end time t0 is entered, for example, as a percentage (%) relative to the pressure P0 at the start time t1.

[0132] Additionally, as described above, the setting screen 761 can also be used to continuously reduce pressure from the middle of the k-th process (k is an integer greater than or equal to 1 and less than or equal to n) to the end of the k-th process. When k is an integer of (n-1), the pressure P1 at the end time t0 of the k-th process can be automatically set based on the pressure setting value in the (k+1)-th process, for example, it can be automatically set to be equal to the pressure setting value in the (k+1)-th process. Furthermore, the input to the second input field 763 can be restricted so that the pressure P1 at the end time t0 of the k-th process is not lower than the pressure setting value in the (k+1)-th process.

[0133] Next, in reference Figures 7-10 Before describing the injection control units 713A to 713D according to the first to fourth embodiments, refer to Figure 11 The injection control unit 713E involved in the reference example will be described. The injection control units 713A to 713D involved in the first to fourth embodiments use the settings input in the setting screen 761 to perform the pressure holding process. In contrast, the injection control unit 713E involved in the reference example does not use the settings input in the setting screen 761 to perform the pressure holding process.

[0134] like Figure 11 As shown, the injection control unit 713E includes, for example, a first calculation unit 771, a speed command creation unit 772, a third calculation unit 773, a current command creation unit 774, a second calculation unit 775, and a voltage command creation unit 776.

[0135] The first calculation unit 771 calculates the difference Pdev (Pdev = Pref - Pdet) between the resin pressure setpoint Pref and the actual pressure value Pdet. The actual pressure value Pdet is obtained from a pressure detector. As described above, the pressure detector can be, for example, a load detector 360, a nozzle pressure sensor, or a mold pressure sensor.

[0136] Alternatively, the first calculation unit 771 can calculate either the pressure setpoint Pref or the actual pressure value Pdet. For example, it can also calculate the ratio of the pressure setpoint Pref to the actual pressure value Pdet.

[0137] The speed command creation unit 772 generates a speed command value Vref for the screw 330 to reduce the difference Pdev calculated by the first calculation unit 771 (preferably to zero). For example, PI or PID calculations are used in generating the speed command value Vref.

[0138] The third calculation unit 773 calculates the difference Vdev (Vdev = Vref - Vdet) between the speed command value Vref and the actual speed value Vdet. The actual speed value Vdet is obtained by the speed detector. As described above, the speed detector can be, for example, an injection motor encoder 351.

[0139] Alternatively, the third calculation unit 773 can calculate either the speed command value Vref or the actual speed value Vdet. For example, it can also calculate the ratio of the speed command value Vref to the actual speed value Vdet.

[0140] The current command creation unit 774 generates a current command value Iref for the injection motor 350 to reduce the difference Vdev calculated by the third calculation unit 773 (preferably to zero). For example, PI or PID calculations are used in generating the current command value Iref.

[0141] The second calculation unit 775 calculates the difference Idev (Idev = Iref - Idet) between the current command value Iref and the actual current value Idet. The actual current value Idet is obtained by a current detector. The current detector is installed, for example, in the inverter 781 or the injection motor 350.

[0142] Alternatively, the second calculation unit 775 can calculate either the current command value Iref or the actual current value Idet. For example, it can also calculate the ratio of the current command value Iref to the actual current value Idet.

[0143] The voltage command creation unit 776 generates a voltage command value to reduce the difference Idev calculated by the second calculation unit 775 (preferably to zero). The inverter 781 supplies alternating current to the injection motor 350 according to the voltage command value generated by the voltage command creation unit 776.

[0144] Alternatively, the injection control unit 713E may not have this feature. Figure 11 This is part of the constituent components shown. For example, the speed command creation unit 772 and the third calculation unit 773 may be omitted, and the current command creation unit 774 may generate the current command value Iref of the injection motor 350 so that the difference Pdev calculated by the first calculation unit 771 is reduced (preferably to zero).

[0145] Furthermore, the injection control unit 713E can also have the function of... Figure 11 The components are not shown in the figure. For example, the injection control unit 713E may have a torque command creation unit (not shown) instead of the current command creation unit 774. This is because the torque of the injection motor 350 is approximately proportional to the current of the injection motor 350.

[0146] The torque command creation unit generates a torque command value Tref for the injection motor 350 to reduce the difference Vdev calculated by the third calculation unit 773 (preferably to zero). The second calculation unit 775 calculates the difference Tdev (Tdev = Tref - Tdet) between the torque command value Tref and the actual torque value Tdet. The voltage command creation unit 776 generates a voltage command value to reduce the difference Tdev calculated by the second calculation unit 775 (preferably to zero).

[0147] like Figure 11 As shown, the injection control unit 713E is composed of multiple components. If the pressure is to be continuously reduced from the middle of the pressure holding process to the end of the pressure holding process (or from the middle of the k-th process to the end of the k-th process), further components are required. From the viewpoint of simplifying the control calculations of the injection control unit 713, there is room for improvement in the location and function of the components used for continuously reducing pressure.

[0148] Next, refer to Figure 7 The injection control unit 713A according to the first embodiment will be described. Hereinafter, the differences from the injection control unit 713E according to the reference example will be mainly described. The injection control unit 713A uses a value Prefa, which is a value obtained by subtracting the pressure set value Pref from the pressure set value Pref over time, instead of the pressure set value Pref, so that the actual pressure value Pdet of the resin gradually decreases relative to the pressure set value Pref of the resin.

[0149] For example, the injection control unit 713A has a first instruction restriction unit 791. The first instruction restriction unit 791 inputs the value Prefa (Pref = P0) which is the result of subtraction of the pressure setting value Pref over time into the first calculation unit 771 according to the settings input in the setting screen 761.

[0150] The subtraction amount (Pref-Prefa) performed by the first instruction restriction unit 791 increases over time, for example, by a constant rate Kp (Kp>0). For example, the following equations (1) to (2) hold true.

[0151] Pref-Prefa=Kp×(t-t1)……(1)

[0152] Kp=(P0-P1) / (t0-t1)……(2)

[0153] In equation (1) above, t is greater than or equal to t1 and less than or equal to t0 (t1≤t≤t0). Furthermore, when t is greater than or equal to 0 and less than or equal to t1 (0≤t≤t1), Prefa and Pref are equal.

[0154] As described above, the first command limiting unit 791 inputs the value Prefa, which is the result of subtracting the pressure setpoint Pref over time, into the first calculation unit 771. The first calculation unit 771 calculates the difference Pdeva (Pdeva = Prefa - Pdet) between the subtracted value Prefa and the actual pressure value Pdet. The speed command creation unit 772 generates the speed command value Vref of the screw 330 to reduce the difference Pdeva calculated by the first calculation unit 771 (preferably to zero).

[0155] According to this embodiment, the first instruction limiting unit 791 inputs the pressure setting value Pref (Pref = P0) into the first calculation unit 771 instead of the pressure setting value Pref (Pref = P0) by subtracting the pressure setting value Pref from the pressure setting value Pref over time. This allows the pressure setting value Pref to gradually decrease, and the actual pressure value Pdet to gradually decrease relative to the pressure setting value Pref. Therefore, the power consumption of the injection motor 350 can be reduced.

[0156] Furthermore, according to this embodiment, the value input to the first calculation unit 771 is corrected, thus simplifying the control calculation of the injection control unit 713 compared to correcting the value output from the first calculation unit 771 (i.e., the difference Pdev). This is because PI or PID calculations are performed during the process of creating a command value (e.g., the speed command value Vref) to reduce the difference Pdev, but setting correction terms in these calculations is more complicated.

[0157] Next, refer to Figure 8 The injection control unit 713B according to the second embodiment will be described. Hereinafter, the differences from the injection control unit 713E according to the reference example will be mainly described. The injection control unit 713B uses a value Pdeta, which is the result of adding the actual pressure value Pdet over time, instead of the actual pressure value Pdet, so that the actual pressure value Pdet gradually decreases relative to the pressure set value Pref.

[0158] For example, the injection control unit 713B has a first numerical addition unit 792. The first numerical addition unit 792 adds a value ΔPdet to the actual pressure value Pdet input to the first calculation unit 771 according to the settings input in the setting screen 761. The added value ΔPdet increases over time, for example, at a constant rate Kp (Kp > 0). For example, the following equation (3) holds.

[0159] ΔPdet=Kp(t-t1)……(3)

[0160] In equation (3) above, t is greater than or equal to t1 and less than or equal to t0 (t1≤t≤t0). In addition, when t is greater than or equal to 0 and less than or equal to t1 (0≤t≤t1), ΔPdet is zero.

[0161] As can be clearly seen from equations (3) and (1) above, the addition amount ΔPdet in this embodiment is equal to the subtraction amount (Pref-Prefa) in the first embodiment above. Therefore, in both this embodiment and the first embodiment above, the difference calculated by the first calculation unit 771 is the same, Pdeva. Therefore, according to this embodiment, similarly to the first embodiment above, the actual pressure value Pdet gradually decreases relative to the pressure set value Pref. Therefore, the power consumption of the injection motor 350 can be reduced. Furthermore, according to this embodiment, similarly to the first embodiment above, the value input to the first calculation unit 771 is corrected, thus simplifying the control calculation compared to correcting the value output from the first calculation unit 771 (i.e., the difference Pdev).

[0162] Next, refer to Figure 9 The injection control unit 713C according to the third embodiment will be described. Hereinafter, the differences from the injection control unit 713E according to the reference example will be mainly described. The injection control unit 713C uses the value Irefa, which is the result of subtracting the current command value Iref over time, instead of the current command value Iref, so that the actual pressure value Pdet gradually decreases relative to the pressure set value Pref.

[0163] For example, the injection control unit 713C has a second instruction restriction unit 793. The second instruction restriction unit 793 inputs the value Irefa, which is the result of subtracting the current instruction value Iref over time, into the second calculation unit 775 according to the settings input in the setting screen 761.

[0164] The subtraction amount (Iref-Irefa) performed by the second instruction restriction unit 793 increases over time, for example, by a constant rate Ki (Ki>0). For example, the following equations (4) to (5) hold true.

[0165] Iref-Irefa=Ki(t-t1)……(4)

[0166] Ki=a×Kp……(5)

[0167] In equation (4) above, t is greater than t1 and less than t0 (t1≤t≤t0). Additionally, when t is greater than 0 and less than t1 (0≤t≤t1), Irefa and Iref are equal. In equation (5) above, a is a constant. The greater the current of the injection motor 350, the greater the torque of the injection motor 350, and the greater the pressure of the resin. The pressure of the resin is approximately proportional to the current of the injection motor 350. The ratio of current to pressure (current / pressure) is approximately constant. The representative value of this ratio is a.

[0168] As described above, the second instruction limiting unit 793 inputs the value Irefa, obtained by subtracting the current instruction value Iref over time, to the second calculation unit 775. The second calculation unit 775 calculates the difference Ideva (Ideva = Irefa - Idet) between the subtracted value Irefa and the actual current value Idet. The voltage instruction creation unit 776 generates a voltage instruction value to reduce the difference Ideva calculated by the second calculation unit 775 (preferably to zero).

[0169] According to this embodiment, unlike the first embodiment described above, the value Irefa, obtained by subtracting the current command value Iref over time, is input to the second calculation unit 775. Here, the current is approximately proportional to the pressure. Therefore, according to this embodiment, similar to the first embodiment described above, the actual pressure value Pdet gradually decreases relative to the pressure set value Pref. Thus, the power consumption of the injection motor 350 can be reduced.

[0170] Furthermore, according to this embodiment, the value input to the second calculation unit 775 is corrected, thus simplifying the control operation compared to correcting the value output from the second calculation unit 775 (i.e., the difference Idev). This is because calculations are performed during the process of generating a voltage command value to reduce the difference Idev, but setting the correction term in that calculation is more complicated.

[0171] Similarly to the injection control unit 713E, the injection control unit 713C may also have a torque command creation unit (not shown) instead of the current command creation unit 774. In this case, the second command limiting unit 793, according to the settings input in the setting screen 761, inputs the value Trefa, which is the result of subtracting the torque command value Tref over time, into the second calculation unit 775 instead of the torque command value Tref.

[0172] The subtraction amount (Tref-Trefa) performed by the second instruction restriction unit 793 increases over time, for example, at a constant rate Kt (Kt>0). For example, the following equations (6) to (7) hold.

[0173] Tref-Trefa=Kt(t-t1)……(6)

[0174] Kt=b×Kp……(7)

[0175] In equation (6) above, t is greater than t1 and less than t0 (t1≤t≤t0). Furthermore, when t is greater than 0 and less than t1 (0≤t≤t1), Trefa and Tref are equal. In equation (7) above, b is a constant. The greater the torque of the injection motor 350, the greater the resin pressure. The resin pressure is approximately proportional to the torque of the injection motor 350. The ratio of torque to pressure (torque / pressure) is approximately constant. The representative value of this ratio is b.

[0176] As described above, the second command limiting unit 793 inputs the value Trefa, which is the result of subtracting the torque command value Tref over time, into the second calculation unit 775. The second calculation unit 775 calculates the difference Tdeva (Tdeva = Trefa - Tdet) between the subtracted value Trefa and the actual torque value Tdet. The voltage command creation unit 776 generates a voltage command value to reduce the difference Tdeva calculated by the second calculation unit 775 (preferably to zero).

[0177] Torque and pressure are approximately proportional. Therefore, even though the value Trefa, which is the result of subtracting the torque command value Tref over time, is input to the second calculation unit 775, similarly to the first embodiment described above, the actual pressure value Pdet gradually decreases relative to the pressure setpoint Pref. Therefore, the power consumption of the injection motor 350 can be reduced. Furthermore, by correcting the value input to the second calculation unit 775, the control calculation can be simplified compared to correcting the value output from the second calculation unit 775 (i.e., the difference Tdev).

[0178] Next, refer to Figure 10 The injection control unit 713D according to the fourth embodiment will be described. Hereinafter, the differences from the injection control unit 713E according to the reference example will be mainly described. The injection control unit 713D uses the value Iteta, which is the result of adding the actual current value Itet over time, instead of the actual current value Itet, so that the actual pressure value Pdet gradually decreases relative to the pressure set value Pref.

[0179] For example, the injection control unit 713D has a second numerical addition unit 794. The second numerical addition unit 794 adds a value ΔIdet to the actual current value Idet input to the second calculation unit 775 according to the settings input in the setting screen 761. The added value ΔIdet increases over time, for example, at a constant rate Ki (Ki>0). For example, the following equation (8) holds.

[0180] ΔIdet=Ki(t-t1)……(8)

[0181] In equation (8) above, t is greater than t1 and less than t0 (t1≤t≤t0). In addition, when t is greater than 0 and less than t1 (0≤t≤t1), ΔIdet is zero.

[0182] As clearly shown in equations (8) and (4) above, the addition amount ΔIdet in this embodiment is equal to the subtraction amount (Iref-Irefa) in the third embodiment above. Therefore, in both this embodiment and the third embodiment above, the difference calculated by the second calculation unit 775 is the same Ideva. Therefore, according to this embodiment, similarly to the third embodiment above, the actual pressure value Pdet gradually decreases relative to the pressure set value Pref. Therefore, the power consumption of the injection motor 350 can be reduced. Furthermore, according to this embodiment, similarly to the third embodiment above, the value input to the second calculation unit 775 is corrected, thus simplifying the control calculation compared to correcting the value output from the second calculation unit 775 (i.e., the difference Idev).

[0183] Similarly to the injection control unit 713E, the injection control unit 713D may also have a torque command creation unit (not shown) instead of the current command creation unit 774. In this case, the second numerical addition unit 794 adds a value ΔTdet to the actual torque value Tdet input to the second calculation unit 775 according to the settings input in the setting screen 761. The added value ΔTdet increases over time, for example, at a constant rate Kt (Kt > 0). For example, the following equation (9) holds.

[0184] ΔTdet=Kt(t-t1)……(9)

[0185] In equation (9) above, t is greater than or equal to t1 and less than or equal to t0 (t1≤t≤t0). In addition, when t is greater than or equal to 0 and less than or equal to t1 (0≤t≤t1), ΔTdet is zero.

[0186] As clearly shown in equations (9) and (6) above, the addition amount ΔTdet in this embodiment is equal to the subtraction amount (Tref-Trefa) in the third embodiment above. Therefore, when the actual torque value Tdet input to the second calculation unit 775 is added to the value ΔTdet, the actual pressure value Pdet gradually decreases relative to the pressure set value Pref, just as in the third embodiment above. Therefore, the power consumption of the injection motor 350 can be reduced. Furthermore, by correcting the value input to the second calculation unit 775, the control calculation can be simplified compared to correcting the value output from the second calculation unit 775 (i.e., the difference Tdev).

[0187] However, pressure is roughly proportional to current or torque, but not perfectly proportional. Therefore, based on continuously reducing resin pressure with high precision, the injection control unit 713A of the first embodiment (see reference) Figure 7 Compared to the injection control unit 713C of the third embodiment (see reference) Figure 9 More preferably, the injection control unit 713B of the second embodiment (see reference) Figure 8 Compared to the injection control unit 713D of the fourth embodiment (reference 4), Figure 10 (More preferred.)

[0188] Furthermore, the operation direction of adding the actual pressure value Pdet to the actual pressure value Pdet with the aim of gradually reducing the actual pressure value Pdet is opposite in terms of purpose and means, making it difficult to understand intuitively. Therefore, the injection control unit 713A of the first embodiment (see reference) Figure 7 Compared to the injection control unit 713B of the second embodiment (see reference) Figure 8 More preferably, the injection control unit 713C of the third embodiment (see reference) Figure 9 Compared to the injection control unit 713D of the fourth embodiment (reference 4), Figure 10 (More preferred.)

[0189] The above describes the embodiments of the control device, injection molding machine, and control method for the injection molding machine involved in this invention. However, this invention is not limited to the above embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations can be made within the scope described in the technical solution. These, of course, also fall within the technical scope of this invention.

Claims

1. A control device for an injection molding machine, the injection molding machine comprising an injection component for pressing molding material and an injection drive source for moving the injection component, the control device for the injection molding machine comprising: The injection control unit divides the pressure holding process, which controls the pressure exerted by the injection component on the molding material, into n processes. In each process, a speed command value for the injection component is generated based on the set pressure value and the actual pressure value. A current command value for the injection drive source is generated based on the speed command value of the injection component. The injection drive source is controlled based on the current command value of the injection drive source. n is an integer greater than or equal to 2. The injection control unit is, The set value of the kth pressure is replaced by the value obtained by subtracting the set value of the kth pressure over time, so that in the kth process, the actual value of the kth pressure gradually decreases from the set value of the kth pressure toward the set value of the (k+1)th pressure, where k is an integer greater than 1 and less than (n-1).

2. The control device for the injection molding machine according to claim 1, comprising: The display control unit displays a setting screen on the display device that sets the actual value of the k-th pressure to be lower than the set value of the k-th pressure.

3. An injection molding machine comprising the control device, the injection component, and the injection drive source as described in claim 1.

4. A control method for an injection molding machine, the injection molding machine comprising an injection component for pressing molding material and an injection drive source for moving the injection component, the control method for the injection molding machine comprising: The injection control process divides the pressure holding process, which controls the pressure exerted by the injection component on the molding material, into n processes. In each process, a speed command value for the injection component is generated based on the set pressure value and the actual pressure value. A current command value for the injection drive source is generated based on the speed command value of the injection component. The injection drive source is then controlled based on the current command value of the injection drive source. Here, n is an integer greater than or equal to 2. The injection control process includes the following steps: The set value of the kth pressure is replaced by the value obtained by subtracting the set value of the kth pressure over time, so that in the kth process, the actual value of the kth pressure gradually decreases from the set value of the kth pressure toward the set value of the (k+1)th pressure, where k is an integer greater than 1 and less than (n-1).

5. The control method for an injection molding machine according to claim 4, comprising: The display control process displays a setting screen on the display device that sets the actual value of the k-th pressure to be lower than the set value of the k-th pressure.

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