Injection molding device and mold clamping device

Abstract

The invention provides an injection molding device and a mold clamping device, which can restrain the change of the mold clamping force every time the mold is clamped. The injection molding apparatus includes an injection unit, a mold clamping unit, and a control unit. The mold clamping unit includes: a toggle fixing plate; fixing the mold assembly part; a movable mold fitting part provided between the toggle fixing plate and the fixed mold fitting part so as to be capable of advancing and retreating in the mold clamping direction; a motor; a ball screw assembled on the toggle fixing plate and driven by the motor to rotate; a crosshead that moves between the toggle fixing plate and the movable mold fitting part by rotation of the ball screw; a toggle section connected to the toggle fixing plate, the movable mold fitting section, and the crosshead, the movable mold fitting section being moved in a mold clamping direction by movement of the crosshead; and a position detection unit that detects the position of the crosshead, and the control unit controls the position of the crosshead by driving the motor on the basis of the detection result of the position detection unit, thereby operating the toggle unit and clamping the fixed mold and the movable mold.

Description

Technical Field

[0001] This disclosure relates to injection molding apparatus and mold clamping apparatus. Background Technology

[0002] Patent document 1 discloses an electric toggle-type mold clamping device that can control the upper limit of the mold opening force by mastering and setting the toggle ratio at the mold opening position corresponding to the mold clamping force.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2010-162805

[0004] In the clamping action of a toggle-type clamping device, the motor that moves the crosshead is sometimes controlled based on a set torque value. In this case, due to factors such as thermal expansion of the components constituting the clamping device or the molding die, even if the set torque value is the same, the stopping position of the crosshead may change in order to perform clamping. The clamping force of the toggle-type clamping device is determined based on the stopping position of the crosshead; therefore, the clamping force may vary in order to perform clamping. Summary of the Invention

[0005] According to a first aspect of this disclosure, an injection molding apparatus is provided. This injection molding apparatus is an injection molding apparatus that uses a molding die consisting of a fixed die and a movable die to injection mold an article. It comprises: an injection unit for injecting material of the article into the molding die; a mold closing unit for assembling and closing the molding die; and a control unit for controlling the injection unit and the mold closing unit, the mold closing unit having: a toggle plate; a fixed die assembly part for assembling the fixed die; a movable die assembly part disposed retractably between the toggle plate and the fixed die assembly part in the mold closing direction for assembling the movable die; a motor; and a ball screw for assembling... The toggle plate is rotated by the motor; the crosshead moves between the toggle plate and the movable mold assembly by the rotation of the ball screw; the toggle section is connected to the toggle plate, the movable mold assembly, and the crosshead, and the movable mold assembly moves along the mold closing direction by the movement of the crosshead; and the position detection unit detects the position of the crosshead, and the control unit controls the position of the crosshead by driving the motor based on the detection result of the position detection unit, thereby causing the toggle section to move and close the fixed mold and the movable mold.

[0006] According to a second aspect of this disclosure, a mold closing device is provided. This mold closing device includes: a toggle plate; a fixed mold assembly for mounting a fixed mold whose position is fixed during mold closing; a movable mold assembly for being retractably disposed between the toggle plate and the fixed mold assembly in the mold closing direction, and for mounting a movable mold that moves relative to the fixed mold during the mold closing action; a motor; a ball screw mounted on the toggle plate and rotated by the motor; a crosshead that moves between the toggle plate and the movable mold assembly by the rotation of the ball screw; a toggle section connected to the toggle plate, the movable mold assembly, and the crosshead, and whose movement causes the movable mold assembly to move along the mold closing direction; a position detection unit for detecting the position of the crosshead; and a control unit that controls the position of the crosshead by driving the motor based on the detection result of the position detection unit, thereby actuating the toggle section and closing the fixed mold and the movable mold. Attached Figure Description

[0007] Figure 1 This is an explanatory diagram showing the general structure of an injection molding apparatus.

[0008] Figure 2 This is a cross-sectional view showing the general structure of the injection unit.

[0009] Figure 3 This is a three-dimensional view showing the outline of a flat-head screw.

[0010] Figure 4 This is a top view of the feed cylinder.

[0011] Figure 5 This is an explanatory diagram showing the general structure of the mold clamping unit.

[0012] Figure 6 This is an explanatory diagram showing the general structure of the mold clamping unit.

[0013] Figure 7 This is an explanatory diagram showing the general structure of the mold clamping unit.

[0014] Figure 8 It is a graph illustrating the time-varying torque value of the motor during the mold closing and opening actions.

[0015] Figure 9 This is a graph illustrating the time variation of the motor's torque value when the control unit drives the motor based on the torque value setpoint.

[0016] Figure 10 This is a graph illustrating the time variation of the motor torque value during the mold closing and mold opening operations in the second embodiment.

[0017] Figure 11 This is an explanatory diagram showing the outline configuration of the mold-closing unit in the third embodiment.

[0018] Figure 12 This is a graph illustrating the time variation of the motor torque value during the mold closing and mold opening operations in the third embodiment.

[0019] Explanation of reference numerals in the attached figures

[0020] 10…Injection molding unit, 11…Base, 20…Injection unit, 21…Plasticizing section, 22…Suction and delivery section, 23…Nozzle, 30, 30c…Mold clamping unit, 40…Control section, 50…Hopper, 90…Molding die, 91…Fixed die, 92…Modible die, 110…Flat-headed screw, 111…Screw box, 112…Drive motor, 121…Gutter forming surface, 122…Central section, 123…Gutter, 124…Material inlet, 125…Raised section, 130…Barrel, 131…Connecting hole, 132…Check valve, 133…Opposing surface, 134…Guide groove, 140…Heater, 151…Injection cylinder, 152…Plunger, 153…Plunger drive section, 170… Flow path, 201…pull rod, 210…toggle fixing plate, 220…fixed mold assembly, 230…movable mold assembly, 240…motor, 250…ball screw, 251…screw shaft, 252…ball screw nut, 260…crosshead, 270…toggle, 271…first component, 272…second component, 273…third component, 280…position detection unit, 290…fixed plate moving part, 291…base, 292…first gear, 293…second gear, AX…axis, BX1…first rotating shaft, BX2…second rotating shaft, BX3…third rotating shaft, BX4…fourth rotating shaft, BX5…fifth rotating shaft, C…bending angle, RX…rotation shaft. Detailed Implementation

[0021] A. First implementation method:

[0022] Figure 1 This is an explanatory diagram showing the general configuration of the injection molding apparatus 10. Figure 1 The diagram shows arrows representing the X, Y, and Z directions, which are mutually orthogonal. The X and Y directions are parallel to the horizontal plane. The Z direction is parallel to the vertical direction. Figure 1 The X, Y, and Z directions in this diagram indicate the same direction as the X, Y, and Z directions in other diagrams. When the orientation is determined, the positive direction indicated by the arrow is marked with "+", and the negative direction indicated by the arrow is marked with "-", and positive and negative signs are used in the direction marking.

[0023] The injection molding apparatus 10 includes an injection unit 20, a mold clamping unit 30, and a control unit 40. The injection molding apparatus 10 uses a molding die 90 mounted on the mold clamping unit 30 to perform injection molding of the molded article. The injection unit 20 and the mold clamping unit 30 are fixed on a base 11. The injection molding apparatus 10 is a horizontal injection molding apparatus, with the injection unit 20 and the mold clamping unit 30 arranged horizontally. The control unit 40 is housed in the base 11.

[0024] The control unit 40 controls the injection unit 20 and the mold closing unit 30. The control unit 40 is configured as a computer equipped with one or more processors, a memory, and an input / output interface for inputting and outputting signals to external devices. The control unit 40 performs various functions, such as processing the molding of the molded article, by executing programs or commands read from the main storage device through the processor. Alternatively, the control unit 40 may be configured not as a computer, but as a combination of multiple circuits that implement at least some of the functions.

[0025] A metal molding die 90 is mounted on the mold closing unit 30. The metal molding die 90 is also referred to as a die. The molding die 90 consists of a fixed die 91 and a movable die 92. The fixed die 91 is the die whose position is fixed during the mold closing operation. The movable die 92 is the die that moves relative to the fixed die 91 during the mold closing operation. The movable die 92 moves relative to the fixed die 91 in the mold closing direction via the mold closing unit 30. In this embodiment, the mold closing direction is the -X direction. Furthermore, the molding die 90 is not limited to being made of metal; it can also be made of resin or ceramic.

[0026] The injection unit 20 is connected to a hopper 50 for feeding material into the molded article. The material for the molded article may be, for example, a thermoplastic resin formed in granular form. Examples of thermoplastic resins that can be used include ABS (acrylonitrile butadiene styrene), PC (polycarbonate), POM (polyacetal), PP (polypropylene), and PBT (polybutylene terephthalate). In addition to thermoplastic resins, the material of the molded article may also include metals and ceramics. The supply of material to the injection unit 20 is not limited to the hopper 50; for example, it may be supplied via a material feeding tube.

[0027] The injection unit 20 plasticizes at least a portion of the material supplied from the hopper 50 to generate a molding material, and injects the generated molding material into the molding die 90. In this specification, "plasticization" refers to a process that includes melting, a change from a solid to a fluid state. Specifically, in the case of materials undergoing a glass transition, plasticization means setting the material temperature above the glass transition point. In the case of materials not undergoing a glass transition, plasticization means setting the material temperature above the melting point.

[0028] Figure 2 This is a cross-sectional view showing the general configuration of the injection unit 20. The injection unit 20 includes a plasticizing section 21, a suction and delivery section 22, and a nozzle 23.

[0029] The plasticizing unit 21 plasticizes at least a portion of the material supplied from the hopper 50 to generate a molding material. The plasticizing unit 21 includes a flat-head screw 110, a barrel 130, and a heater 140. The flat-head screw 110 is housed in a screw housing 111. The flat-head screw 110 may also be referred to as a rotor, or simply a screw. The flat-head screw 110 is driven to rotate within the screw housing 111 by a drive motor 112 about a rotation axis RX. In this embodiment, the direction of the rotation axis RX is along the X direction. A connecting hole 131 is formed at the center of the barrel 130. The connecting hole 131 forms at least a portion of the flow path 170 through which the molding material flows. The connecting hole 131 is connected to the injection cylinder 151, described later. A check valve 132 is provided upstream of the injection cylinder 151 from the connecting hole 131. The rotation of the flat-head screw 110 by the drive motor 112 and the heating by the heater 140 are controlled by a control unit 40.

[0030] Figure 3 This is a perspective view showing the general structure of the flat-head screw 110. The flat-head screw 110 has a generally cylindrical shape, with its height smaller than its diameter along its central axis. A vortex-shaped groove 123 is formed on the groove forming surface 121 of the flat-head screw 110, opposite the barrel 130, with a central portion 122 as its center. The groove 123 communicates with a material inlet 124 formed on the side of the flat-head screw 110. Material supplied from the hopper 50 is supplied to the groove 123 through the material inlet 124. The groove 123 is formed by being separated by protrusions 125. Figure 3 The example shown has three grooves 123, but the number of grooves 123 can be one or more. In addition, the grooves 123 are not limited to a spiral shape, but can also be a spiral or an involute curve shape, or can be a shape that extends from the central portion 122 toward the outer periphery in an arc.

[0031] Figure 4This is a schematic top view of the barrel 130. The barrel 130 has a facing surface 133 opposite to the groove forming surface 121 of the flat-head screw 110. A connecting hole 131 is formed in the center of the facing surface 133. A plurality of guide grooves 134 are formed in the facing surface 133, which are connected to the connecting hole 131 and extend outward from the connecting hole 131 in a vortex shape. The material supplied to the groove 123 of the flat-head screw 110 is plasticized between the flat-head screw 110 and the barrel 130 by the rotation of the flat-head screw 110 and the heating of the heater 140. At the same time, the material flows along the groove 123 and the guide grooves 134 by the rotation of the flat-head screw 110 and is guided towards the central portion 122 of the flat-head screw 110. The material flowing into the central portion 122 flows out from the connecting hole 131 provided in the center of the barrel 130 to the suction delivery portion 22. Alternatively, the guide groove 134 may not be provided in the barrel 130. Furthermore, the guide groove 134 may not be connected to the connecting hole 131.

[0032] like Figure 2 As shown, the suction delivery unit 22 includes an injection cylinder 151, a plunger 152, and a plunger drive unit 153. The suction delivery unit 22 functions to inject molding material from the injection cylinder 151 into a cavity divided between the fixed mold 91 and the movable mold 92. Under the control of the control unit 40, the suction delivery unit 22 controls the injection volume, injection speed, and injection pressure of the molding material from the nozzle 23. The injection cylinder 151 is a generally cylindrical component connected to the communication hole 131 of the barrel 130, and has a plunger 152 inside. The plunger 152 slides inside the injection cylinder 151, pressing the molding material from the injection cylinder 151 to the nozzle 23 in the injection unit 20. The plunger 152 is driven by a plunger drive unit 153, which is powered by an electric motor.

[0033] A flow path 170 is formed in the nozzle 23. The plunger 152 pressurizes the molding material in the injection cylinder 151 to the nozzle 23, thereby injecting the molding material from the nozzle 23 into the molding die 90. The nozzle 23 can be configured as either an open gate nozzle or a valve gate nozzle.

[0034] Figures 5 to 7 This is an explanatory diagram showing the general structure of the mold closing unit 30. The mold closing unit 30 will be assembled with the molding die 90 to close the mold. Figure 5 The image shows the state where the molding die 90 has been opened. Figure 6 and Figure 7 The image shows the mold 90 in the closed state. The mold closing unit 30 includes a toggle plate 210, a fixed mold assembly 220, a movable mold assembly 230, a motor 240, a ball screw 250, a crosshead 260, a toggle section 270, and a position detection section 280.

[0035] A fixed mold assembly 220 is fixed to the -X direction end of a pull rod 201 extending in the X direction. A fixed mold 91 is assembled in the fixed mold assembly 220. A toggle plate 210 is fixed to the pull rod 201 on the +X direction side of the fixed mold assembly 220. A movable mold assembly 230 is movably disposed between the fixed mold assembly 220 and the toggle plate 210 along the extension direction of the pull rod 201. That is, the movable mold assembly 230 is disposed to move forward and backward in the mold closing direction. A movable mold 92 is assembled in the movable mold assembly 230 in a manner opposite to the fixed mold 91.

[0036] Motor 240 rotates the ball screw 250, which will be described later. Motor 240 is, for example, a servo motor. Motor 240 is controlled by control unit 40.

[0037] A ball screw 250 is disposed between the toggle plate 210 and the movable mold assembly 230. The ball screw 250 has a lead screw shaft 251 and a ball screw nut 252. The lead screw shaft 251 is mounted to the toggle plate 210 in a manner protruding from the toggle plate 210 in the -X direction. The lead screw shaft 251 is connected to the output shaft of a motor 240 via a coupling (not shown). The lead screw shaft 251 rotates about its axis AX under the drive of the motor 240. The direction along which the axis AX is located is the X direction. The ball screw nut 252 moves in the X direction as the lead screw shaft 251 rotates.

[0038] The crosshead 260 is fixed to the ball screw nut 252. Therefore, when the ball screw nut 252 moves in the X direction as the screw shaft 251 rotates, the crosshead 260 also moves in the X direction along with the ball screw nut 252. That is, the crosshead 260 moves in the X direction between the toggle plate 210 and the movable mold assembly 230 due to the rotation of the ball screw 250.

[0039] The toggle joint 270 is connected to the toggle joint fixing plate 210, the movable mold assembly 230, and the crosshead 260. The toggle joint 270 has a first component 271, a second component 272, and a third component 273. The first component 271, the second component 272, and the third component 273 are symmetrically arranged about a horizontal plane including the axis AX of the lead screw shaft 251.

[0040] The first component 271 is connected to the toggle fixing plate 210 via the first rotating shaft BX1. The axis of the first rotating shaft BX1 is along the Y direction. The first component 271 is rotatably arranged in the XZ plane with the first rotating shaft BX1 as the center. The first component 271 is also referred to as a crank.

[0041] One end of the second component 272 is connected to the first component 271 via a second rotating shaft BX2, and the other end is connected to the movable mold assembly 230 via a third rotating shaft BX3. The axes of the second rotating shaft BX2 and the third rotating shaft BX3 are aligned in the Y direction. The second component 272 is rotatably mounted relative to the first component 271 in the XZ plane with the second rotating shaft BX2 as its center. Furthermore, the second component 272 is rotatably mounted relative to the movable mold assembly 230 in the XZ plane with the third rotating shaft BX3 as its center. The second component 272 is also referred to as a connecting rod.

[0042] One end of the third component 273 is connected to the first component 271 via the fourth rotating shaft BX4, and the other end is connected to the crosshead 260 via the fifth rotating shaft BX5. The axes of the fourth rotating shaft BX4 and the fifth rotating shaft BX5 are aligned in the Y direction. The third component 273 is rotatably mounted relative to the first component 271 in the XZ plane with the fourth rotating shaft BX4 as its center. Additionally, the third component 273 is rotatably mounted relative to the crosshead 260 in the XZ plane with the fifth rotating shaft BX5 as its center. The third component 273 is also referred to as a connecting rod.

[0043] When the crosshead 260 moves in the -X direction, each component of the toggle joint 270 rotates around its respective axis, thereby moving the movable mold assembly 230 in the -X direction. This causes the molding die 90 to close. When the crosshead 260 moves in the +X direction, each component of the toggle joint 270 rotates around its respective axis, thereby moving the movable mold assembly 230 in the +X direction. This causes the molding die 90 to open. In other words, the toggle joint 270 moves the movable mold assembly 230 along the mold-closing direction by moving the crosshead 260. Hereinafter, the rotation of each component of the toggle joint 270 around its respective axis will also be referred to as the operation of the toggle joint 270.

[0044] The position detection unit 280 detects the position of the crosshead 260. The position detection unit 280 may be, for example, an encoder installed on the motor 240. The position detection unit 280 indirectly detects the position of the crosshead 260 in the mold closing direction by detecting the rotational speed or rotation angle of the motor 240. Alternatively, the position detection unit 280 may not be an encoder, but rather an optical sensor or the like that directly detects the position of the crosshead 260 in the mold closing direction.

[0045] The control unit 40 drives the motor 240 based on the detection results of the position detection unit 280 to control the position of the crosshead 260, thereby actuating the toggle unit 270 to perform mold closing and opening of the fixed mold 91 and the movable mold 92. In this disclosure, controlling the position of the crosshead 260 by driving the motor 240 based on the detection results of the position detection unit 280 is also referred to as position control.

[0046] Figure 8 This is a graph illustrating the time-varying torque value of motor 240 during the mold closing and opening actions. Figure 8 In the diagram, the horizontal axis represents time. The vertical axis represents the measured torque value of motor 240. See below for reference. Figures 5 to 8 This will explain the mold closing and mold opening actions.

[0047] exist Figure 5 The diagram shows the state of the mold closing unit 30 at time T1. At time T1, the fixed mold 91 and the movable mold 92 are separated. Hereinafter, the position of the crosshead 260 at time T1 will be referred to as the first position.

[0048] From time T1 to time T2, the control unit 40 drives the motor 240 to move the crosshead 260 in the -X direction, causing it to move to a second position, which is a predetermined position. This moves the movable mold assembly unit 230 in the -X direction. Here, the second position refers to the position where the fixed mold 91 and the movable mold 92 are in contact. Whether the crosshead 260 has moved to the second position is determined based on the detection result of the position detection unit 280. The movement of the crosshead 260 to the second position is completed at time T2. That is, the fixed mold 91 and the movable mold 92 are in contact at time T2. Figure 6 The diagram shows the state of the mold-closing unit 30 at time T2. In the second position, the angle C formed by the line L1 connecting the center of the first rotating shaft BX1 and the center of the second rotating shaft BX2, and the line L2 connecting the center of the second rotating shaft BX2 and the center of the third rotating shaft BX3, i.e., the bending angle, is preferably 150° or more and 175° or less. Here, the bending angle C refers to the angle on the side farther from the ball screw 25° in the Z direction among the angles formed by lines L1 and L2. Furthermore, as... Figure 8 As shown, the torque value of motor 240 is M2 and is fixed between time T1 and time T2.

[0049] From time T2 to time T3, the control unit 40 drives the motor 240 to move the crosshead 260 in the -X direction, causing it to move to a predetermined third position. The third position is a position closer to the -X direction than the second position, where the bending angle C is 180°. In other words, the third position is a position where the directions of lines L1 and L2 are in the same direction. Whether the crosshead 260 has moved to the third position is determined based on the detection result of the position detection unit 280. The movement of the crosshead 260 to the third position is completed at time T3. Figure 7The diagram shows the state of the mold-closing unit 30 at time T3. From time T2 to time T3, the crosshead 260 moves from the second position to the third position, thereby closing the fixed mold 91 and the movable mold 92. Additionally, as... Figure 8 As shown, from time T2 to time T3, the torque value of motor 240 increases from M2 to M3. In this embodiment, the torque value of motor 240 between time T2 and time T3 is also referred to as the first torque. That is, between time T2 and time T3, the fixed mold 91 and the movable mold 92 are closed with the first torque. The first torque is a value greater than M2 and less than M3. The period between time T2 and time T3 is also referred to as the mold closing period.

[0050] From time T3 to time T4, the control unit 40 drives the motor 240 such that the crosshead 260 is held in a third position. By holding the crosshead 260 in the third position, the fixed mold 91 and the movable mold 92 are closed at a higher pressure than during the mold closing period. The period from time T3 to time T4 is also referred to as the high-pressure mold closing period. During the high-pressure mold closing period, the injection unit 20 injects molding material into the molding die 90. The mold closing period and the high-pressure mold closing period are the periods during which the fixed mold 91 and the movable mold 92 are closed. Figure 8 As shown, the torque value of motor 240 between time T3 and time T4 is M1 and is fixed. The torque value M1 is smaller than the torque value M2 of motor 240 between time T1 and time T2 and the torque value M3 of motor 240 at time T3. Hereinafter, the torque value of motor 240 between time T3 and time T4 will also be referred to as the second torque. That is, from time T3 to time T4, the fixed mold 91 and the movable mold 92 are closed with the second torque. The second torque is a value smaller than the first torque.

[0051] From time T4 to time T5, the control unit 40 drives the motor 240 to move the crosshead 260 in the +X direction, causing it to move to the first position. This moves the movable mold assembly unit 230 in the +X direction. Whether the crosshead 260 has moved to the first position is determined based on the detection result of the position detection unit 280. The movement of the crosshead 260 to the first position is completed at time T5. That is, from time T4 to time T5, the molding die 90 is opened.

[0052] According to the first embodiment described above, the control unit 40 controls the position of the crosshead 260 by driving the motor 240 based on the detection result of the position detection unit 280, which detects the position of the crosshead 260. This causes the toggle unit 270 to actuate and close the fixed mold 91 and the movable mold 92. Therefore, compared to the case where the control unit 40 controls the position of the crosshead 260 by driving the motor 240 based on a torque value setpoint, the stopping position of the crosshead 260 during mold closing can be controlled more precisely. The mold closing force is determined based on the stopping position of the crosshead 260, thus suppressing fluctuations in the mold closing force during repeated mold closing and improving mold closing accuracy.

[0053] Figure 9 This diagram illustrates the time variation of the torque value of the motor 240 during mold closing and mold opening operations, when the control unit 40 drives the motor 240 to control the position of the crosshead 260 based on a torque value setpoint. In this disclosure, controlling the position of the crosshead 260 by driving the motor 240 based on a torque value setpoint is also referred to as torque control. Figure 9 In the example shown, the torque value is set to M2 and is fixed between time T1 and time T2, increases from M2 to M3 between time T2 and time T3, is set to M3 and is fixed between time T3 and time T4, and is set to M2 and is fixed between time T4 and time T5. During the high-pressure mold closing period from time T3 to time T4, the control unit 40 drives the motor 240 such that its torque value is M3. In this case, the crosshead 260, in contact with a component (not shown) configured not to move further in the -X direction than the third position, is pushed in the -X direction by the drive of the motor 240 and thus held in the third position. That is, the torque value of the motor 240 during the high-pressure mold closing period is greater than in the first embodiment. In contrast, the injection molding apparatus 10 of the first embodiment can reduce the torque value of the motor 240 during the high-pressure mold closing period compared to the above case. Therefore, the lifespan of the motor 240 can be further extended.

[0054] Furthermore, in this embodiment, during high-pressure mold closing, the control unit 40 controls the position of the crosshead 260 such that the line L1 connecting the center of the first rotating shaft BX1 and the center of the second rotating shaft BX2 is in the same direction as the line L2 connecting the center of the second rotating shaft BX2 and the center of the third rotating shaft BX3. Therefore, during high-pressure mold closing, the bending angle C can be easily maintained at 180°. Consequently, the toggle joint 270 can easily and stably receive the force applied to the toggle joint 270 when the molding material is injected into the molding die 90, further extending the lifespan of the toggle joint 270.

[0055] Furthermore, in this embodiment, during the mold closing process of the fixed mold 91 and the movable mold 92, the control unit 40 controls the position of the crosshead 260 such that after the fixed mold 91 and the movable mold 92 are closed with a first torque, they are closed with a second torque that is smaller than the first torque. Therefore, the lifespan of the motor 240 can be further extended.

[0056] Furthermore, in this embodiment, the crosshead 260 is located on the -X direction side during high-pressure mold closing compared to the mold closing period. Therefore, the mold closing pressure during high-pressure mold closing is greater than the mold closing pressure during the mold closing period. Consequently, in injection molding with high injection pressure, the possibility of insufficient mold closing between the fixed mold 91 and the movable mold 92 can be reduced.

[0057] B. Second implementation method:

[0058] In the second embodiment, the control method of the motor 240 by the control unit 40 is different from that in the first embodiment. The configuration of each part of the injection molding apparatus 10 in the second embodiment is the same as that in the first embodiment.

[0059] Figure 10 This is a diagram illustrating the time variation of the torque value of the motor 240 during the mold closing and mold opening operations in the second embodiment. In the second embodiment, the control unit 40 drives the motor 240 based on a set torque value during the mold closing period. For periods other than the mold closing period, the control unit 40, similar to the first embodiment, drives the motor 240 based on the detection results of the position detection unit 280. That is, the control unit 40 performs torque control during the mold closing period and position control during periods other than the mold closing period.

[0060] From time T1 to time T2, the control unit 40, in the same manner as in the first embodiment, drives the motor 240 to move the crosshead 260 in the -X direction, causing the crosshead 260 to move to the second position. This brings the fixed mold 91 into contact with the movable mold 92. In other words, the control unit 40, based on the detection result of the position detection unit 280, drives the motor 240 to control the position of the crosshead 260, thereby actuating the toggle joint 270 and bringing the fixed mold 91 into contact with the movable mold 92. In this disclosure, the above-described control is also referred to as first control. That is, the control unit 40 performs first control from time T1 to time T2.

[0061] Control unit 40 drives motor 240 from time T2 to time T3 in a manner that increases the torque value of motor 240 from M2 to M3. Here, M2 and M3 are predetermined torque value settings. In the second embodiment, the torque at time T2 is referred to as the third torque, and the torque at time T3 is referred to as the fourth torque. The value of the third torque is M2. The value of the fourth torque is M3. That is, after the fixed mold 91 and the movable mold 92 are closed with the third torque, they are closed with the fourth torque, which is greater than the third torque. Control unit 40 controls the torque value of motor 240 by controlling the torque value to gradually increase from M2 to M3, so that the fixed mold 91 and the movable mold 92 are closed with the third torque and then with the fourth torque. In this disclosure, the above control is also referred to as the second control. That is, after performing the first control, control unit 40 performs the second control from time T2 to time T3. Control unit 40 performs the second control, thereby moving crosshead 260 from the second position to the third position.

[0062] From time T3 to time T4, the control unit 40 drives the motor 240 in the same manner as in the first embodiment, so that the crosshead 260 is held in the third position. The torque value of the motor 240 between time T3 and time T4 is M1 and is fixed. M1 is a value smaller than M2 and M3. In the second embodiment, the torque between time T3 and time T4 is also referred to as the fifth torque. The value of the fifth torque is M1. In other words, the control unit 40 controls the position of the crosshead 260 by driving the motor 240 based on the detection result of the position detection unit 280, so that the fixed mold 91 and the movable mold 92 are closed with a fifth torque smaller than the third torque. In this disclosure, the above-described control is also referred to as the third control. That is, the control unit 40 performs the third control from time T3 to time T4 after performing the second control.

[0063] From time T4 to time T5, the control unit 40, similar to the first embodiment, drives the motor 240 to move the crosshead 260 in the +X direction so that the crosshead 260 moves to the first position. This causes the molding die 90 to open.

[0064] According to the second embodiment described above, the control unit 40 sequentially performs a first control as position control, a second control as torque control, and a third control as position control. In the second control, the control unit 40 controls the torque value of the motor 240 such that the fixed mold 91 and the movable mold 92 are closed with a third torque and then with a fourth torque, causing the crosshead 260 to move from the second position to the third position. Therefore, even in mold closing operations that require a large closing force, the crosshead 260 can be easily moved to the third position, thus reducing the possibility that the mold closing of the fixed mold 91 and the movable mold 92 will be insufficient.

[0065] C. Third implementation method:

[0066] Figure 11 This is an explanatory diagram showing the general configuration of the mold clamping unit 30c according to the third embodiment. In the third embodiment, the mold clamping unit 30c further includes a fixing plate moving part 290 that moves the toggle fixing plate 210 along the mold clamping direction. The configurations of the injection unit 20 and the control unit 40 in the third embodiment are the same as those in the first embodiment.

[0067] The fixed plate moving part 290 has a base 291, a first gear 292, a second gear 293, and a fixed plate moving motor (not shown). The base 291 is mounted on the +X direction side of the fixed plate moving part 290. The first gear 292 and the second gear 293 are mounted on the +X direction side of the base 291 with their axes along the X direction. The first gear 292 is connected to the fixed plate moving motor and rotates about its axis by the drive of the fixed plate moving motor. The fixed plate moving motor is controlled by the control unit 40. The second gear 293 meshes with the first gear 292. The second gear 293 has a through hole that extends through the second gear 293 in the X direction. Threaded teeth are formed on the inner surface of the through hole. The pull rod 201 is located in the through hole. The threaded teeth on the inner surface of the through hole engage with the threaded groove formed on the surface of the pull rod 201. Therefore, the first gear 292 rotates about its axis, thereby causing the second gear 293 to rotate about its axis, and the fixed plate moving part 290 moves along the tie rod 201 in the X direction. As a result, the toggle fixed plate 210 moves along the mold closing direction.

[0068] Figure 12 This is a diagram illustrating the time variation of the torque value of the motor 240 during the mold closing and mold opening operations in the third embodiment. The control unit 40 performs position control in the same manner as in the first embodiment. During the period when the fixed mold 91 and the movable mold 92 are closed, the control unit 40 also controls the fixed plate moving part 290 to move the toggle fixed plate 210 in the direction where the mold closing pressure increases. The direction where the mold closing pressure increases refers to the -X direction, which is the mold closing direction. From time T3 to time T6, which is the time between time T3 and time T4, the control unit 40 controls the fixed plate moving part 290 to move the toggle fixed plate 210 in the -X direction. That is, the control unit 40 controls the fixed plate moving part 290 to move the toggle fixed plate 210 in the -X direction during the high-pressure mold closing period. Therefore, in the third embodiment, the mold closing force during the high-pressure mold closing period is greater than that in the first embodiment. Furthermore, the timing at which the control unit 40 controls the fixed plate moving unit 290 to move the toggle fixed plate 210 in the -X direction is not limited to time T3 to time T6, but may be any other time during the high-pressure mold closing period.

[0069] According to the third embodiment described above, the mold clamping unit 30c has a fixed plate moving part 290 that moves the toggle fixing plate 210 along the mold clamping direction. During the period when the fixed mold 91 and the movable mold 92 are closed, the control unit 40 controls the fixed plate moving part 290 to move the toggle fixing plate 210 in the direction where the mold clamping pressure increases. Therefore, the mold clamping force of the mold clamping unit 30c can be further improved. In addition, if the size or thickness of the molding die 90 mounted in the mold clamping unit 30c changes, the mold clamping force can be adjusted to a suitable value for the molding die 90 mounted in the mold clamping unit 30c.

[0070] D. Other implementation methods:

[0071] (D-1) In the above embodiment, the third position is a position where the bending angle C is 180°. However, the third position is not limited to a position where the bending angle C is 180°. Preferably, the third position is a position where the bending angle C is 178° or more and 180° or less. That is, at the third position, lines L1 and L2 may not be completely parallel.

[0072] (D-2) In the above embodiment, during the closing of the fixed mold 91 and the movable mold 92, the control unit 40 controls the position of the crosshead 260 such that the line L1 connecting the center of the first rotation axis BX1 and the center of the second rotation axis BX2 is in the same direction as the line L2 connecting the center of the second rotation axis BX2 and the center of the third rotation axis BX3. Alternatively, during the closing of the fixed mold 91 and the movable mold 92, the control unit 40 controls the position of the crosshead 260 in a manner that the directions of the lines L1 and L2 are not in the same direction.

[0073] (D-3) In the above embodiment, during the period when the fixed mold 91 and the movable mold 92 are closed, the control unit 40 controls the position of the crosshead 260 in a manner that the fixed mold 91 and the movable mold 92 are closed with a first torque and then with a second torque that is smaller than the first torque. Alternatively, the control unit 40 may not control the position of the crosshead 260 in a manner that the fixed mold 91 and the movable mold 92 are closed with a first torque and then with a second torque during the period when the fixed mold 91 and the movable mold 92 are closed.

[0074] (D-4) In the above embodiment, the injection molding apparatus 10 is a horizontal injection molding apparatus. Alternatively, the injection molding apparatus 10 may also be a vertical injection molding apparatus.

[0075] (D-5) The above disclosure may also be implemented not as injection molding apparatus 10, but as a mold clamping device having mold clamping unit 30 and control unit 40.

[0076] E. Other methods:

[0077] This disclosure is not limited to the embodiments described above, and can be implemented in various ways without departing from its spirit. For example, this disclosure can also be implemented in the following ways. The technical features in the above embodiments corresponding to the technical features in the various methods described below can be appropriately replaced or combined to solve part or all of the problems of this disclosure, or to achieve part or all of the effects of this disclosure. In addition, if such technical features are not described as necessary in this specification, they can be appropriately deleted.

[0078] (1) According to a first aspect of this disclosure, an injection molding apparatus is provided. This injection molding apparatus is an injection molding apparatus that uses a molding die consisting of a fixed die and a movable die to perform injection molding of a molded article, comprising: an injection unit for injecting material of the molded article into the molding die; a mold closing unit for assembling the molding die and closing the molding die; and a control unit for controlling the injection unit and the mold closing unit, the mold closing unit having: a toggle plate; a fixed die assembly part for assembling the fixed die; a movable die assembly part disposed retractably between the toggle plate and the fixed die assembly part in the mold closing direction for assembling the movable die; a motor; and a ball screw for assembling... The toggle plate is rotated by the motor; the crosshead moves between the toggle plate and the movable mold assembly by the rotation of the ball screw; the toggle section is connected to the toggle plate, the movable mold assembly, and the crosshead, and the movable mold assembly moves along the mold closing direction by the movement of the crosshead; and the position detection unit detects the position of the crosshead, and the control unit controls the position of the crosshead by driving the motor based on the detection result of the position detection unit, thereby causing the toggle section to move and close the fixed mold and the movable mold.

[0079] In this way, compared to the case where the control unit drives the motor to control the position of the crosshead based on a torque setpoint, the stopping position of the crosshead during mold closing can be controlled more precisely. Therefore, fluctuations in the mold closing force during repeated mold closing can be suppressed.

[0080] (2) In the above-described manner, the toggle section may also have: a first component connected to the toggle fixing plate via a first rotating shaft; a second component connected to the first component via a second rotating shaft and connected to the movable mold assembly via a third rotating shaft; and a third component connected to the crosshead and connected to the first component via a fourth rotating shaft. During the period when the fixed mold and the movable mold are closed, the control unit controls the position of the crosshead in such a way that the line connecting the center of the first rotating shaft and the center of the second rotating shaft is in the same direction as the line connecting the center of the second rotating shaft and the center of the third rotating shaft.

[0081] In this way, the toggle joint can easily and stably accept the force applied to the toggle joint when the material of the molded part is injected into the molding die.

[0082] (3) In the above method, the control unit may control the position of the crosshead in such a way that the fixed mold and the movable mold are closed with a first torque and then closed with a second torque that is smaller than the first torque during the period when the fixed mold and the movable mold are closed.

[0083] This method can further extend the lifespan of the motor.

[0084] (4) In the above method, the control unit may also perform: a first control, which controls the position of the crosshead by driving the motor based on the detection result of the position detection unit, thereby causing the toggle to move and the fixed mold to contact the movable mold; a second control, which, after the first control, controls the torque value of the motor so that the fixed mold and the movable mold are closed with a third torque and then closed with a fourth torque greater than the third torque; and a third control, which, after the second control, controls the position of the crosshead by driving the motor based on the detection result of the position detection unit so that the fixed mold and the movable mold are closed with a fifth torque less than the third torque.

[0085] In this way, even for mold closing actions that require large clamping forces, the crosshead can be easily moved to the position where the fixed mold and the movable mold are closed.

[0086] (5) In the above method, the mold closing unit may also have a fixed plate moving part that moves the toggle fixed plate along the mold closing direction, and the control unit controls the fixed plate moving part during the period of closing the fixed mold and the movable mold, so that the toggle fixed plate moves in the direction where the mold closing pressure increases.

[0087] In this way, the clamping force of the mold clamping unit can be further improved.

[0088] (6) According to a second aspect of this disclosure, a mold closing device is provided. The mold closing device comprises: a toggle plate; a fixed mold assembly for mounting a fixed mold whose position is fixed during the mold closing action; a movable mold assembly for being disposed between the toggle plate and the fixed mold assembly in the mold closing direction and for mounting a movable mold that moves relative to the fixed mold during the mold closing action; a motor; a ball screw mounted on the toggle plate and rotated by the drive of the motor; a crosshead that moves between the toggle plate and the movable mold assembly by the rotation of the ball screw; a toggle section connected to the toggle plate, the movable mold assembly, and the crosshead, for moving the movable mold assembly along the mold closing direction by the movement of the crosshead; a position detection unit for detecting the position of the crosshead; and a control unit for controlling the position of the crosshead by driving the motor based on the detection result of the position detection unit, thereby actuating the toggle section and closing the fixed mold and the movable mold.

[0089] In this way, compared to the case where the control unit drives the motor to control the position of the crosshead based on a torque setpoint, the stopping position of the crosshead during mold closing can be controlled more precisely. Therefore, fluctuations in the mold closing force during repeated mold closing can be suppressed.

Claims

1. An injection molding apparatus characterized by comprising: An injection molding apparatus for injection molding of a molded product using a molding die composed of a fixed die and a movable die, the injection molding apparatus comprising: an injection unit that injects a material of the molded product into the molding die; a die assembling unit that assembles the molding die and closes the molding die; and a control unit that controls the injection unit and the die assembling unit, the die assembling unit having: a toggle fixing plate; a fixed die assembling portion that assembles the fixed die; a movable die assembling portion that is provided between the toggle fixing plate and the fixed die assembling portion so as to be able to advance and retreat in a closing direction, and assembles the movable die; a motor; a ball screw that is assembled to the toggle fixing plate and rotates by driving of the motor; a cross head that moves between the toggle fixing plate and the movable die assembling portion by rotation of the ball screw; a toggle portion that is connected to the toggle fixing plate, the movable die assembling portion, and the cross head, and moves the movable die assembling portion in the closing direction by movement of the cross head; and a position detecting portion that detects a position of the cross head, the control unit controlling the position of the cross head by driving the motor based on a detection result of the position detecting portion, thereby causing the toggle portion to operate and closing the fixed die and the movable die.

2. The injection molding apparatus according to claim 1, wherein the toggle portion has: a first member that is connected to the toggle fixing plate via a first turning axis; a second member that is connected to the first member via a second turning axis, and is connected to the movable die assembling portion via a third turning axis; and a third member that is connected to the cross head, and is connected to the first member via a fourth turning axis, the control unit controlling the position of the cross head so that a line that links a center of the first turning axis and a center of the second turning axis and a line that links the center of the second turning axis and a center of the third turning axis are in the same direction during closing of the fixed die and the movable die.

3. The injection molding apparatus according to claim 1, wherein the control unit controls the position of the cross head so that the fixed die and the movable die are closed with a first torque and then are closed with a second torque smaller than the first torque during closing of the fixed die and the movable die.

4. The injection molding apparatus according to claim 1, wherein the control unit performs: first control that controls the position of the cross head by driving the motor based on a detection result of the position detecting portion, thereby causing the toggle portion to operate and causing the fixed die and the movable die to contact each other; second control that controls a torque value of the motor so that the fixed die and the movable die are closed with a third torque and then are closed with a fourth torque larger than the third torque after the first control; and ​ ​ ​ A third control, after the second control, drives the motor based on a result of detection by the position detection section to control the position of the cross head in such a manner that the fixed mold and the movable mold are clamped with a fifth torque that is smaller than the third torque.

5. The injection molding apparatus according to claim 1, wherein the clamping unit has a fixed plate moving section that moves the toggle fixed plate in the clamping direction, the control section controls the fixed plate moving section to move the toggle fixed plate in a direction in which the pressure of the clamping of the fixed mold and the movable mold increases during the clamping of the fixed mold and the movable mold.

6. A clamping apparatus characterized by comprising: provided with: a toggle fixed plate; a fixed mold fitting section that fits the fixed mold whose position is fixed during a clamping operation; a movable mold fitting section that is provided between the toggle fixed plate and the fixed mold fitting section so as to be able to advance and retreat in the clamping direction and that fits the movable mold that moves relative to the fixed mold during the clamping operation; a motor; a ball screw that is fitted to the toggle fixed plate and that rotates by driving of the motor; a cross head that moves between the toggle fixed plate and the movable mold fitting section by the rotation of the ball screw; a toggle section that is connected to the toggle fixed plate, the movable mold fitting section, and the cross head and that moves the movable mold fitting section in the clamping direction by the movement of the cross head; a position detection section that detects the position of the cross head; and a control section that controls the position of the cross head by driving the motor based on a result of detection by the position detection section to cause the toggle section to operate and to clamp the fixed mold and the movable mold. ​

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