Injection molding equipment and mold clamping devices

Abstract

To provide a technique capable of suppressing fluctuations in mold clamping force every time mold clamping is performed. [Solution] The injection molding apparatus comprises an injection unit, a clamping unit, and a control unit. The clamping unit has a toggle fixing plate, a fixed mold mounting portion, a movable mold mounting portion arranged between the toggle fixing plate and the fixed mold mounting portion so as to be able to move back and forth in the clamping direction, a motor, a ball screw attached to the toggle fixing plate and rotated by the motor, a crosshead that moves between the toggle fixing plate and the movable mold mounting portion by rotation of the ball screw, a toggle portion connected to the toggle fixing plate, the movable mold mounting portion, and the crosshead, and moving the movable mold mounting portion along the clamping direction by movement of the crosshead, and a position detection portion that detects the position of the crosshead. The control unit drives the motor to control the position of the crosshead based on the detection results of the position detection portion, thereby operating the toggle portion and clamping the fixed mold and movable mold.

Description

[Technical Field]

[0001] The present disclosure relates to an injection molding apparatus and a mold clamping device. [Background technology]

[0002] Patent Document 1 discloses a toggle-type electric mold clamping device that can control the upper limit of the mold opening force by determining the toggle magnification at the mold opening position corresponding to the set mold clamping force. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-162805 Summary of the Invention [Problem to be solved by the invention]

[0004] In mold clamping operations using a toggle-type mold clamping unit, the motor that moves the crosshead may be controlled based on a torque setting. In this case, the crosshead stop position may change each time the mold is clamped, even if the torque setting is the same, due to factors such as thermal expansion of the components that make up the mold clamping unit and the mold. Because the clamping force of a toggle-type mold clamping unit is determined by the crosshead stop position, there is a possibility that the clamping force may fluctuate each time the mold is clamped. [Means for solving the problem]

[0005] According to a first aspect of the present disclosure, there is provided an injection molding apparatus for injection molding a molded product using a mold consisting of a fixed mold and a movable mold, the injection molding apparatus comprising: an injection unit for injecting material for the molded product into the mold, a mold clamping unit to which the mold is attached and which clamps the mold, and a control unit for controlling the injection unit and the mold clamping unit, the mold clamping unit comprising: a toggle fixing plate; a fixed mold mounting part to which the fixed mold is attached; a movable mold mounting part provided between the toggle fixing plate and the fixed mold mounting part so as to be movable in the mold clamping direction and to which the movable mold is attached; a motor; a ball screw that rotates when driven by the motor, a crosshead that moves between the toggle fixing plate and the movable mold mounting portion when the ball screw rotates, a toggle portion that is connected to the toggle fixing plate, the movable mold mounting portion, and the crosshead and that moves the movable mold mounting portion in the mold clamping direction when the crosshead moves, and a position detection portion that detects the position of the crosshead, and the control portion drives the motor based on the detection result of the position detection portion to control the position of the crosshead, thereby operating the toggle portion and clamping the fixed mold and the movable mold.

[0006] According to a second aspect of the present disclosure, there is provided a mold clamping apparatus comprising: a toggle fixing plate, a fixed mold mounting portion to which a fixed mold whose position is fixed during a mold clamping operation is mounted, a movable mold mounting portion that is provided between the toggle fixing plate and the fixed mold mounting portion so as to be movable forward and backward in the mold clamping direction and to which a movable mold that moves relative to the fixed mold during the mold clamping operation is mounted, a motor, a ball screw attached to the toggle fixing plate and rotated by driving of the motor, a crosshead that moves between the toggle fixing plate and the movable mold mounting portion by rotation of the ball screw, a toggle portion connected to the toggle fixing plate, the movable mold mounting portion, and the crosshead, and that moves the movable mold mounting portion in the mold clamping direction by movement of the crosshead, a position detection portion that detects the position of the crosshead, and a control portion that drives the motor to control the position of the crosshead based on the detection result of the position detection portion, thereby operating the toggle portion and clamping the fixed mold and the movable mold. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is an explanatory diagram showing a schematic configuration of an injection molding device. [Figure 2] FIG. 2 is a cross-sectional view showing a schematic configuration of an injection unit. [Figure 3] FIG. 2 is a perspective view showing a schematic configuration of a flat screw. [Figure 4] FIG. 2 is a schematic plan view of the barrel. [Figure 5] FIG. 2 is an explanatory diagram showing a schematic configuration of a mold clamping unit. [Figure 6] FIG. 2 is an explanatory diagram showing a schematic configuration of a mold clamping unit. [Figure 7] FIG. 2 is an explanatory diagram showing a schematic configuration of a mold clamping unit. [Figure 8] 10A and 10B are diagrams illustrating the change over time in the torque value of the motor during the mold clamping operation and the mold opening operation. [Figure 9] 10A and 10B are diagrams illustrating changes in the torque value of a motor over time when a control unit drives the motor based on a set value of the torque value. [Figure 10]10A to 10C are diagrams illustrating the change over time in the torque value of the motor during the mold clamping operation and mold opening operation of the second embodiment. [Figure 11] FIG. 10 is an explanatory view showing a schematic configuration of a mold clamping unit in a third embodiment. [Figure 12] 10A to 10C are diagrams illustrating the change over time in the torque value of the motor during the mold clamping operation and mold opening operation of the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. First embodiment: FIG. 1 is an explanatory diagram showing the schematic configuration of an injection molding apparatus 10. FIG. 1 shows arrows representing mutually orthogonal X, Y, and Z directions. The X and Y directions are parallel to a horizontal plane. The Z direction is parallel to the vertical direction. The X, Y, and Z directions in FIG. 1 and the X, Y, and Z directions in other figures indicate the same directions. When specifying a direction, positive and negative signs are used in combination to indicate the direction, with "+" indicating the positive direction indicated by the arrow and "-" indicating the negative direction opposite to the direction indicated by the arrow.

[0009] Injection molding apparatus 10 includes an injection unit 20, a clamping unit 30, and a control unit 40. Injection molding apparatus 10 performs injection molding of a molded product using a molding die 90 attached to the clamping unit 30. Injection unit 20 and clamping unit 30 are fixed onto a base 11. Injection molding apparatus 10 is a horizontal injection molding apparatus, and injection unit 20 and clamping unit 30 are aligned horizontally. Control unit 40 is housed in base 11.

[0010] The control unit 40 controls the injection unit 20 and the mold clamping unit 30. The control unit 40 is configured by a computer equipped with one or more processors, a memory, and an input / output interface for inputting and outputting signals to and from the outside. The control unit 40 performs various functions, such as executing the process of molding a molded product, by the processor executing programs and instructions loaded onto the main memory. Note that instead of being configured by a computer, the control unit 40 may be realized by a configuration combining multiple circuits for realizing at least some of the functions.

[0011] A metal molding die 90 is attached to the clamping unit 30. The metal molding die 90 is also called a mold. The molding die 90 is composed of a fixed die 91 and a movable die 92. The fixed die 91 is a die whose position is fixed during the clamping operation. The movable die 92 is a die that is moved relative to the fixed die 91 during the clamping operation. The movable die 92 is moved in the clamping direction relative to the fixed die 91 by the clamping unit 30. In this embodiment, the clamping direction is the -X direction. Note that the molding die 90 is not limited to being made of metal, and may be made of resin or ceramic.

[0012] A hopper 50 into which the material for the molded article is introduced is connected to the injection unit 20. The material for the molded article may be, for example, a thermoplastic resin formed into pellets. Examples of the thermoplastic resin include ABS (acrylonitrile butadiene styrene), PC (polycarbonate), POM (polyacetal), PP (polypropylene), and PBT (polybutylene terephthalate). The material for the molded article may contain metal or ceramic in addition to the thermoplastic resin. The material may be supplied to the injection unit 20 not only through the hopper 50 but also, for example, via a tube through which the material is pressure-fed.

[0013] The injection unit 20 plasticizes at least a portion of the material supplied from the hopper 50 to produce a molding material, and then injects the produced molding material into the mold 90. In this specification, the term "plasticization" includes melting and refers to changing a material from a solid to a fluid state. Specifically, for a material that undergoes glass transition, plasticization refers to raising the temperature of the material above its glass transition point. For a material that does not undergo glass transition, plasticization refers to raising the temperature of the material above its melting point.

[0014] 2 is a cross-sectional view showing a schematic configuration of the injection unit 20. The injection unit 20 includes a plasticizing section 21, a suction delivery section 22, and a nozzle .

[0015] The plasticizing unit 21 plasticizes at least a portion of the material supplied from the hopper 50 to produce a molding material. The plasticizing unit 21 includes a flat screw 110, a barrel 130, and a heater 140. The flat screw 110 is housed in a screw case 111. The flat screw 110 is also called a rotor or simply a screw. The flat screw 110 is driven to rotate around a rotation axis RX within the screw case 111 by a drive motor 112. In this embodiment, the direction of the rotation axis RX is aligned with the X direction. A communication hole 131 is formed in the center of the barrel 130. The communication hole 131 forms at least a portion of a flow path 170 through which the molding material flows. An injection cylinder 151, which will be described later, is connected to the communication hole 131. A check valve 132 is provided in the communication hole 131 upstream of the injection cylinder 151. The rotation of the flat screw 110 by the drive motor 112 and the heating by the heater 140 are controlled by the control unit 40 .

[0016] FIG. 3 is a perspective view showing a schematic configuration of the flat screw 110. The flat screw 110 has a generally cylindrical shape with a height along its central axis that is smaller than its diameter. A spiral groove 123 is formed around a central portion 122 on a groove-forming surface 121 of the flat screw 110 that faces the barrel 130. The groove 123 communicates with a material inlet 124 formed on the side surface of the flat screw 110. Material supplied from the hopper 50 is supplied to the groove 123 through the material inlet 124. The grooves 123 are formed by being separated by ridge portions 125. While FIG. 3 shows an example in which three grooves 123 are formed, the number of grooves 123 may be one or more. The groove 123 is not limited to a spiral shape, but may also be a spiral shape or an involute curve shape, or may have a shape extending in an arc from the central portion 122 to the outer periphery.

[0017] FIG. 4 is a schematic plan view of the barrel 130. The barrel 130 has an opposing surface 133 that faces the groove-forming surface 121 of the flat screw 110. A communication hole 131 is formed in the center of the opposing surface 133. The opposing surface 133 is formed with a plurality of guide grooves 134 that are connected to the communication hole 131 and extend spirally from the communication hole 131 toward the outer periphery. The material supplied to the groove 123 of the flat screw 110 is plasticized between the flat screw 110 and the barrel 130 by the rotation of the flat screw 110 and the heating of the heater 140. Then, the material flows along the groove 123 and the guide groove 134 due to the rotation of the flat screw 110 and is guided to the central portion 122 of the flat screw 110. The material that flows into the central portion 122 flows out from the communication hole 131 provided in the center of the barrel 130 to the suction delivery section 22. Note that the barrel 130 does not necessarily have to be provided with the guide groove 134. Furthermore, the guide groove 134 does not have to be connected to the communication hole 131 .

[0018] As shown in FIG. 2, the suction and delivery unit 22 includes an injection cylinder 151, a plunger 152, and a plunger driver 153. The suction and delivery unit 22 injects the molding material in the injection cylinder 151 into a cavity defined between the fixed mold 91 and the movable mold 92. Under the control of the control unit 40, the suction and delivery unit 22 controls the injection amount, injection speed, and injection pressure of the molding material from the nozzle 23. The injection cylinder 151 is a substantially cylindrical member connected to the communication hole 131 of the barrel 130 and includes a plunger 152 therein. The plunger 152 slides inside the injection cylinder 151 and pressure-feeds the molding material in the injection cylinder 151 to the nozzle 23 provided in the injection unit 20. The plunger 152 is driven by a plunger driver 153, which is configured by a motor.

[0019] Nozzle 23 is formed with a flow path 170. Plunger 152 pressure-feeds the molding material in injection cylinder 151 to nozzle 23, causing the molding material to be injected from nozzle 23 into mold 90. Nozzle 23 may be configured as an open-gate type nozzle or as a valve-gate type nozzle.

[0020] 5 to 7 are explanatory diagrams showing the schematic configuration of the clamping unit 30. The clamping unit 30 clamps the molding die 90 attached to the clamping unit 30. FIG. 5 shows the molding die 90 in an open state, while FIGS. 6 and 7 show the molding die 90 in a clamped state. The clamping unit 30 has a toggle fixing plate 210, a fixed mold mounting part 220, a movable mold mounting part 230, a motor 240, a ball screw 250, a crosshead 260, a toggle part 270, and a position detection part 280.

[0021] The fixed mold mounting part 220 is fixed to the end of the tie bar 201 extending in the X direction on the -X direction side. A fixed mold 91 is attached to the fixed mold mounting part 220. The toggle fixing plate 210 is fixed to the tie bar 201 on the +X direction side of the fixed mold mounting part 220. The movable mold mounting part 230 is provided between the fixed mold mounting part 220 and the toggle fixing plate 210 so as to be movable along the direction in which the tie bar 201 extends. In other words, the movable mold mounting part 230 is provided so as to be able to advance and retreat in the mold clamping direction. A movable mold 92 is attached to the movable mold mounting part 230 so as to face the fixed mold 91.

[0022] The motor 240 rotates a ball screw 250 (described later). The motor 240 is, for example, a servo motor. The motor 240 is controlled by the control unit 40.

[0023] The ball screw 250 is provided between the toggle fixing plate 210 and the movable die mounting portion 230. The ball screw 250 has a screw shaft 251 and a ball screw nut 252. The screw shaft 251 is attached to the toggle fixing plate 210 so as to protrude from the toggle fixing plate 210 in the -X direction. The screw shaft 251 is connected to the output shaft of the motor 240 via a coupling (not shown). The screw shaft 251 rotates around its axis AX when driven by the motor 240. The direction along the axis AX is the X direction. The ball screw nut 252 moves in the X direction as the screw shaft 251 rotates.

[0024] The crosshead 260 is fixed to the ball screw nut 252. Therefore, when the ball screw nut 252 moves in the X direction in accordance with the rotation of the screw shaft 251, the crosshead 260 also moves in the X direction together with the ball screw nut 252. In other words, the crosshead 260 moves in the X direction between the toggle fixing plate 210 and the movable die mounting portion 230 due to the rotation of the ball screw 250.

[0025] The toggle part 270 is connected to the toggle fixing plate 210, the movable die mounting part 230, and the crosshead 260. The toggle part 270 has a first member 271, a second member 272, and a third member 273. The first member 271, the second member 272, and the third member 273 are provided symmetrically with respect to a horizontal plane including the axis line AX of the screw shaft 251.

[0026] The first member 271 is connected to the toggle fixing plate 210 via a first rotation shaft BX1. The direction along the axis of the first rotation shaft BX1 is the Y direction. The first member 271 is provided so as to be rotatable within the XZ plane around the first rotation shaft BX1. The first member 271 is also called a crank.

[0027] One end of the second member 272 is connected to the first member 271 via a second rotation axis BX2, and the other end is connected to the movable mold attachment part 230 via a third rotation axis BX3. The direction along the axes of the second rotation axis BX2 and the third rotation axis BX3 is the Y direction. The second member 272 is provided so as to be rotatable relative to the first member 271 in the XZ plane around the second rotation axis BX2. The second member 272 is also provided so as to be rotatable relative to the movable mold attachment part 230 in the XZ plane around the third rotation axis BX3. The second member 272 is also called a connecting rod.

[0028] One end of the third member 273 is connected to the first member 271 via a fourth rotation axis BX4, and the other end is connected to the crosshead 260 via a fifth rotation axis BX5. The direction along the axes of the fourth rotation axis BX4 and the fifth rotation axis BX5 is the Y direction. The third member 273 is provided so as to be rotatable relative to the first member 271 in the XZ plane around the fourth rotation axis BX4. The third member 273 is also provided so as to be rotatable relative to the crosshead 260 in the XZ plane around the fifth rotation axis BX5. The third member 273 is also called a link.

[0029] When the crosshead 260 moves in the -X direction, each member of the toggle unit 270 rotates around each rotation axis, causing the movable mold mount 230 to move in the -X direction. This causes the molding die 90 to be clamped. When the crosshead 260 moves in the +X direction, each member of the toggle unit 270 rotates around each rotation axis, causing the movable mold mount 230 to move in the +X direction. This causes the molding die 90 to be opened. In other words, the toggle unit 270 moves the movable mold mount 230 in the clamping direction by moving the crosshead 260. Hereinafter, the rotation of each member of the toggle unit 270 around each rotation axis is also referred to as the toggle unit 270 operating.

[0030] The position detection unit 280 detects the position of the crosshead 260. The position detection unit 280 is, for example, an encoder provided in the motor 240. The position detection unit 280 indirectly detects the position of the crosshead 260 in the mold clamping direction by detecting the number of rotations and rotation angle of the motor 240. Note that the position detection unit 280 may be an optical sensor or the like that directly detects the position of the crosshead 260 in the mold clamping direction, instead of an encoder.

[0031] The control unit 40 drives the motor 240 to control the position of the crosshead 260 based on the detection result of the position detection unit 280, thereby operating the toggle unit 270 and clamping and opening the fixed mold 91 and the movable mold 92. In the present disclosure, controlling the position of the crosshead 260 by driving the motor 240 based on the detection result of the position detection unit 280 is also referred to as position control.

[0032] Fig. 8 is a diagram illustrating the change over time in the torque value of the motor 240 during the mold clamping operation and mold opening operation. In Fig. 8, the horizontal axis represents time, and the vertical axis represents the measured torque value of the motor 240. The mold clamping operation and mold opening operation will be described below with reference to Figs. 5 to 8.

[0033] 5 shows the state of the mold clamping unit 30 at time T1. At time T1, the fixed mold 91 and the movable mold 92 are separated from each other. Hereinafter, the position of the crosshead 260 at time T1 will be referred to as the first position.

[0034] Between time T1 and time T2, the control unit 40 drives the motor 240 to move the crosshead 260 in the -X direction so that the crosshead 260 moves to a second position, which is a predetermined position. This causes the movable mold attachment unit 230 to move in the -X direction. Here, the second position is a position where the fixed mold 91 and the movable mold 92 come into contact with each other. Whether the crosshead 260 has moved to the second position is determined based on the detection result of the position detection unit 280. The crosshead 260 completes moving to the second position at time T2. That is, the fixed mold 91 and the movable mold 92 come into contact with each other at time T2. FIG. 6 shows the state of the mold clamping unit 30 at time T2. At the second position, the bending angle C, which is the angle between a line L1 connecting the center of the first rotating shaft BX1 and the center of the second rotating shaft BX2 and a line L2 connecting the center of the second rotating shaft BX2 and the center of the third rotating shaft BX3, is preferably 150° or more and 175° or less. Here, the bending angle C is the angle between the line L1 and the line L2 on the side farther from the ball screw 250 in the Z direction. Furthermore, as shown in FIG. 8, the torque value of the motor 240 is constant at M2 between time T1 and time T2.

[0035] From time T2 to time T3, the control unit 40 drives the motor 240 to move the crosshead 260 in the −X direction so that the crosshead 260 moves 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 lines L1 and L2 are aligned 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 crosshead 260 completes its movement to the third position at time T3. FIG. 7 shows the state of the mold clamping unit 30 at time T3. As the crosshead 260 moves from the second position to the third position from time T2 to time T3, the fixed mold 91 and the movable mold 92 are clamped together. As shown in FIG. 8, the torque value of the motor 240 increases from M2 to M3 from time T2 to time T3. In this embodiment, the torque value of the motor 240 from time T2 to time T3 is also referred to as the first torque. That is, from time T2 to time T3, the fixed mold 91 and the movable mold 92 are clamped with the first torque. The first torque has a value equal to or greater than M2 and equal to or less than M3. The period from time T2 to time T3 is also referred to as the mold clamping period.

[0036] From time T3 to time T4, the control unit 40 drives the motor 240 so that the crosshead 260 maintains the third position. By maintaining the crosshead 260 at the third position, the fixed mold 91 and the movable mold 92 are clamped at a pressure higher than that during the clamping period. The period from time T3 to time T4 is also referred to as the high-pressure clamping period. The injection unit 20 injects molding material into the molding mold 90 during the high-pressure clamping period. The clamping period and the high-pressure clamping period are periods during which the fixed mold 91 and the movable mold 92 are clamped together. As shown in FIG. 8 , the torque value of the motor 240 from time T3 to time T4 is constant at M1. The torque value M1 is smaller than the torque value M2 of the motor 240 from time T1 to time T2 and the torque value M3 of the motor 240 at time T3. Hereinafter, the torque value of the motor 240 from time T3 to time T4 is also referred to as the second torque. That is, from time T3 to time T4, the fixed mold 91 and the movable mold 92 are clamped with the second torque, which is smaller than the first torque.

[0037] Between time T4 and time T5, control unit 40 drives motor 240 to move crosshead 260 in the +X direction so that crosshead 260 moves to the first position. This causes movable mold mount 230 to move in the +X direction. Whether crosshead 260 has moved to the first position is determined based on the detection result of position detection unit 280. Crosshead 260 completes moving to the first position at time T5. In other words, between time T4 and time T5, forming mold 90 is opened.

[0038] According to the first embodiment described above, the control unit 40 drives the motor 240 to control the position of the crosshead 260 based on the detection result of the position detection unit 280, which detects the position of the crosshead 260, thereby operating the toggle unit 270 and clamping the fixed mold 91 and the movable mold 92. Therefore, the stopping position of the crosshead 260 during clamping can be controlled more precisely than when the control unit 40 drives the motor 240 based on a set torque value to control the position of the crosshead 260. Because the clamping force is determined by the stopping position of the crosshead 260, fluctuations in the clamping force can be suppressed when clamping is performed repeatedly, and the accuracy of clamping can be improved.

[0039] FIG. 9 is a diagram illustrating the change over time in the torque value of the motor 240 during mold clamping and mold opening operations when the control unit 40 drives the motor 240 based on a set torque value to control the position of the crosshead 260. In this disclosure, controlling the position of the crosshead 260 by driving the motor 240 based on a set torque value is also referred to as torque control. In the example shown in FIG. 9, the set torque value is constant at M2 from time T1 to time T2, increases from M2 to M3 from time T2 to time T3, remains constant at M3 from time T3 to time T4, and remains constant at M2 from time T4 to time T5. The control unit 40 drives the motor 240 so that the torque value of the motor 240 is M3 during the high-pressure mold clamping period from time T3 to time T4. In this case, the crosshead 260 is kept at the third position by being pressed in the -X direction against a member (not shown) that is provided to prevent the crosshead 260 from moving further in the -X direction than the third position, by being driven by the motor 240. That is, the torque value of the motor 240 during the high-pressure clamping period is greater than in the first embodiment. In contrast, the injection molding apparatus 10 in the first embodiment can reduce the torque value of the motor 240 during the high-pressure clamping period compared to the above-mentioned case. This can extend the life of the motor 240.

[0040] Furthermore, in this embodiment, control unit 40 controls the position of crosshead 260 during the high-pressure clamping period so that line L1 connecting the center of first rotation axis BX1 and the center of second rotation axis BX2 and line L2 connecting the center of second rotation axis BX2 and the center of third rotation axis BX3 are aligned in the same direction. This makes it easier to maintain bending angle C at 180° during the high-pressure clamping period. This makes it easier for toggle portion 270 to stably withstand the force applied to toggle portion 270 when molding material is injected into molding die 90, thereby extending the life of toggle portion 270.

[0041] Furthermore, in this embodiment, during the period in which the fixed mold 91 and the movable mold 92 are clamped together, the control unit 40 controls the position of the crosshead 260 so that the fixed mold 91 and the movable mold 92 are clamped together with a first torque and then clamped together with a second torque smaller than the first torque. This makes it possible to extend the life of the motor 240.

[0042] Furthermore, in this embodiment, the crosshead 260 is positioned further in the -X direction during the high-pressure mold clamping period than during the mold clamping period. Therefore, the mold clamping pressure during the high-pressure mold clamping period is greater than the mold clamping pressure during the mold clamping period. Therefore, it is possible to reduce the possibility of insufficient mold clamping between the fixed mold 91 and the movable mold 92 during injection molding with high injection pressure.

[0043] B. Second embodiment: The second embodiment differs from the first embodiment in the method of controlling the motor 240 by the control unit 40. The configuration of each part of the injection molding apparatus 10 in the second embodiment is the same as that in the first embodiment.

[0044] 10 is a diagram illustrating the change over time in the torque value of the motor 240 during the mold clamping operation and mold opening operation of the second embodiment. In the second embodiment, the control unit 40 drives the motor 240 based on the set torque value during the mold clamping period. During periods other than the mold clamping period, the control unit 40 drives the motor 240 based on the detection results of the position detection unit 280, as in the first embodiment. That is, the control unit 40 performs torque control during the mold clamping period and position control during periods other than the mold clamping period.

[0045] As in the first embodiment, the control unit 40 drives the motor 240 to move the crosshead 260 in the −X direction from time T1 to time T2 so that the crosshead 260 moves to the second position. This brings the fixed mold 91 and the movable mold 92 into contact with each other. In other words, the control unit 40 drives the motor 240 to control the position of the crosshead 260 based on the detection result of the position detection unit 280, thereby operating the toggle unit 270 and bringing the fixed mold 91 and the movable mold 92 into contact with each other. In the present disclosure, the above-described control is also referred to as first control. That is, the control unit 40 performs the first control from time T1 to time T2.

[0046] The control unit 40 drives the motor 240 so that the torque value of the motor 240 increases from M2 to M3 from time T2 to time T3. Here, M2 and M3 are predetermined torque setting values. 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, the fixed mold 91 and the movable mold 92 are clamped with the third torque and then clamped with a fourth torque greater than the third torque. The control unit 40 controls the torque value of the motor 240 by gradually increasing the torque value from M2 to M3, so that the fixed mold 91 and the movable mold 92 are clamped with the third torque and then clamped with the fourth torque. In the present disclosure, the above-described control is also referred to as second control. That is, after performing the first control, the control unit 40 performs the second control from time T2 to time T3. The control unit 40 performs the second control, whereby the crosshead 260 moves from the second position to the third position.

[0047] As in the first embodiment, the control unit 40 drives the motor 240 from time T3 to time T4 so that the crosshead 260 maintains the third position. The torque value of the motor 240 from time T3 to time T4 is constant at M1. M1 is a value smaller than M2 and M3. In the second embodiment, the torque from time T3 to time T4 is also referred to as a fifth torque. The value of the fifth torque is M1. In other words, the control unit 40 drives the motor 240 to control the position of the crosshead 260 based on the detection result of the position detection unit 280 so that the fixed mold 91 and the movable mold 92 are clamped with a fifth torque smaller than the third torque. In the present disclosure, the above-described control is also referred to as a third control. That is, after performing the second control, the control unit 40 performs the third control from time T3 to time T4.

[0048] Similar to the first embodiment, from time T4 to time T5, control unit 40 drives motor 240 to move crosshead 260 in the +X direction so that crosshead 260 moves to the first position, thereby opening forming mold 90.

[0049] According to the second embodiment described above, the control unit 40 performs the first control, which is a position control, the second control, which is a torque control, and the third control, which is a position control, in this order. In the second control, the control unit 40 controls the torque value of the motor 240 so that the fixed mold 91 and the movable mold 92 are clamped together with a third torque and then clamped with a fourth torque, thereby moving the crosshead 260 from the second position to the third position. Therefore, even in a clamping operation that requires a large clamping force, the crosshead 260 can be easily moved to the third position, thereby reducing the possibility of insufficient clamping between the fixed mold 91 and the movable mold 92.

[0050] C. Third embodiment: 11 is an explanatory diagram showing a schematic configuration of a mold clamping unit 30c in the third embodiment. In the third embodiment, the mold clamping unit 30c further includes a fixed plate moving unit 290 that moves the toggle fixed plate 210 along the mold clamping direction. The configurations of the components of the injection unit 20 and the control unit 40 in the third embodiment are the same as those in the first embodiment.

[0051] The fixed plate moving unit 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 attached to the +X direction side of the fixed plate moving unit 290. The first gear 292 and the second gear 293 are attached to the +X direction side of the base 291 so that their axes are aligned in the X direction. The first gear 292 is connected to the fixed plate moving motor and rotates around its axis when driven by 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 passes through the second gear 293 in the X direction. A screw thread is formed on the inner surface of the through hole. A tie bar 201 is located within the through hole. The screw thread on the inner surface of the through hole is threaded into a screw groove formed on the surface of the tie bar 201. Therefore, when the first gear 292 rotates about its axis, the second gear 293 rotates about its axis, and the fixed plate moving part 290 moves in the X direction along the tie bars 201. As a result, the toggle fixed plate 210 moves in the mold clamping direction.

[0052] FIG. 12 is a diagram illustrating the change over time in the torque value of the motor 240 during the mold clamping operation and mold opening operation of the third embodiment. The control unit 40 performs position control in the same manner as in the first embodiment. The control unit 40 further controls the fixed plate moving unit 290 to move the toggle fixed plate 210 in a direction in which the mold clamping pressure increases during the period in which the fixed mold 91 and the movable mold 92 are clamped. The direction in which the mold clamping pressure increases is the −X direction, which is the mold clamping direction. The control unit 40 controls the fixed plate moving unit 290 to move the toggle fixed plate 210 in the −X direction from time T3 to time T6, which is a time between time T3 and time T4. That is, the control unit 40 controls the fixed plate moving unit 290 to move the toggle fixed plate 210 in the −X direction during the high-pressure mold clamping period. As a result, in the third embodiment, the mold clamping force during the high-pressure mold clamping period is greater than that in the first embodiment. The time when 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 the time from time T3 to time T6, but may be any other time within the high pressure mold clamping period.

[0053] According to the third embodiment described above, the clamping unit 30c has the fixed plate moving part 290 that moves the toggle fixed plate 210 in the clamping direction, and the control part 40 controls the fixed plate moving part 290 to move the toggle fixed plate 210 in a direction that increases the clamping pressure during the period when the fixed mold 91 and the movable mold 92 are clamped together. This makes it possible to further improve the clamping force of the clamping unit 30c. Furthermore, if the size or thickness of the molding mold 90 attached to the clamping unit 30c changes, the clamping force can be adjusted to an appropriate value for the molding mold 90 attached to the clamping unit 30c.

[0054] D. Other Embodiments: (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°. The third position is preferably a position where the bending angle C is 178° or more and 180° or less. In other words, at the third position, the lines L1 and L2 do not have to be completely parallel.

[0055] (D-2) In the above embodiment, the control unit 40 controls the position of the crosshead 260 so that the line L1 connecting the center of the first rotation axis BX1 and the center of the second rotation axis BX2 and the line L2 connecting the center of the second rotation axis BX2 and the center of the third rotation axis BX3 are aligned in the same direction during the period when the fixed mold 91 and the movable mold 92 are clamped together. In contrast, the control unit 40 does not have to control the position of the crosshead 260 so that the line L1 and the line L2 are aligned in the same direction during the period when the fixed mold 91 and the movable mold 92 are clamped together.

[0056] (D-3) In the above embodiment, the control unit 40 controls the position of the crosshead 260 during the period in which the fixed mold 91 and the movable mold 92 are clamped together with a first torque, and then clamped with a second torque smaller than the first torque. In contrast, the control unit 40 does not have to control the position of the crosshead 260 during the period in which the fixed mold 91 and the movable mold 92 are clamped together with a first torque, and then clamped with a second torque.

[0057] (D-4) In the above embodiment, the injection molding apparatus 10 is a horizontal injection molding apparatus. However, the injection molding apparatus 10 may be a vertical injection molding apparatus.

[0058] (D-5) The above disclosure may be implemented in the form of a mold clamping device including a mold clamping unit 30 and a control unit 40, instead of the injection molding device 10.

[0059] E. Other forms: The present disclosure is not limited to the above-described embodiments and can be realized in various forms without departing from the spirit thereof. For example, the present disclosure can also be realized in the following forms. The technical features in the above embodiments corresponding to the technical features in each form described below can be appropriately replaced or combined to solve some or all of the problems of the present disclosure or to achieve some or all of the effects of the present disclosure. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted.

[0060] (1) According to a first aspect of the present disclosure, there is provided an injection molding apparatus for injection molding a molded product using a mold consisting of a fixed mold and a movable mold, the injection molding apparatus comprising: an injection unit for injecting material for the molded product into the mold, a mold clamping unit to which the mold is attached and which clamps the mold, and a control unit for controlling the injection unit and the mold clamping unit, the mold clamping unit comprising: a toggle fixing plate; a fixed mold mounting part to which the fixed mold is attached; a movable mold mounting part provided between the toggle fixing plate and the fixed mold mounting part so as to be movable in the mold clamping direction and to which the movable mold is attached; a motor; and a controller attached to the toggle fixing plate. the control unit has a ball screw that rotates when driven by the motor, a crosshead that moves between the toggle fixing plate and the movable mold mounting portion when the ball screw rotates, a toggle portion that is connected to the toggle fixing plate, the movable mold mounting portion, and the crosshead and that moves the movable mold mounting portion in the mold clamping direction when the crosshead moves, and a position detection portion that detects the position of the crosshead, and the control unit drives the motor based on the detection result of the position detection portion to control the position of the crosshead, thereby operating the toggle portion and clamping the fixed mold and the movable mold. According to this configuration, the stopping position of the crosshead during mold clamping can be controlled more precisely than when the control unit controls the position of the crosshead by driving the motor based on the set torque value, and therefore fluctuations in the mold clamping force can be suppressed when mold clamping is performed repeatedly.

[0061] (2) In the above embodiment, the toggle portion has a first member connected to the toggle fixing plate via a first pivot axis, a second member connected to the first member via a second pivot axis and connected to the movable mold mounting portion via a third pivot axis, and a third member connected to the crosshead and connected to the first member via a fourth pivot axis, and the control unit may control the position of the crosshead so that, during the period in which the fixed mold and the movable mold are clamped, the direction of a line connecting the center of the first pivot axis and the center of the second pivot axis and the direction of a line connecting the center of the second pivot axis and the center of the third pivot axis are along the same direction. According to this configuration, the toggle portion can stably receive the force applied to the toggle portion when the material for the molded product is injected into the mold.

[0062] (3) In the above embodiment, the control unit may control the position of the crosshead during the period in which the fixed mold and the movable mold are clamped together so that the fixed mold and the movable mold are clamped together with a first torque and then clamped together with a second torque smaller than the first torque. This configuration can extend the life of the motor.

[0063] (4) In the above embodiment, the control unit may perform a first control in which the motor is driven to control the position of the crosshead based on the detection result of the position detection unit, thereby operating the toggle unit and bringing the fixed mold and the movable mold into contact; a second control in which, after the first control, the torque value of the motor is controlled so that the fixed mold and the movable mold are clamped with a third torque and then clamped with a fourth torque greater than the third torque; and a third control in which, after the second control, the motor is driven to control the position of the crosshead based on the detection result of the position detection unit so that the fixed mold and the movable mold are clamped with a fifth torque smaller than the third torque. According to this configuration, even in a clamping operation that requires a large clamping force, the crosshead can be easily moved to a position where the fixed mold and the movable mold are clamped.

[0064] (5) In the above embodiment, the mold clamping unit has a fixed plate moving part that moves the toggle fixed plate along the mold clamping direction, and the control part may control the fixed plate moving part to move the toggle fixed plate in a direction in which the mold clamping pressure increases during the period in which the fixed mold and the movable mold are clamped. According to this configuration, the clamping force of the clamping unit can be further improved.

[0065] (6) According to a second aspect of the present disclosure, there is provided a mold clamping device comprising: a toggle fixing plate; a fixed mold mounting portion to which a fixed mold whose position is fixed during a mold clamping operation is mounted; a movable mold mounting portion that is provided between the toggle fixing plate and the fixed mold mounting portion so as to be movable forward and backward in the mold clamping direction and to which a movable mold that moves relative to the fixed mold during the mold clamping operation is mounted; a motor; a ball screw attached to the toggle fixing plate and rotated by driving of the motor; a crosshead that moves between the toggle fixing plate and the movable mold mounting portion by rotation of the ball screw; a toggle portion connected to the toggle fixing plate, the movable mold mounting portion, and the crosshead and that moves the movable mold mounting portion in the mold clamping direction by movement of the crosshead; a position detection portion that detects the position of the crosshead; and a control portion that drives the motor to control the position of the crosshead based on the detection result of the position detection portion, thereby operating the toggle portion and clamping the fixed mold and the movable mold. According to this configuration, the stopping position of the crosshead during mold clamping can be controlled more precisely than when the control unit controls the position of the crosshead by driving the motor based on the set torque value, and therefore fluctuations in the mold clamping force can be suppressed when mold clamping is performed repeatedly. [Explanation of symbols]

[0066] 10...injection molding apparatus, 11...base, 20...injection unit, 21...plasticizing section, 22...suction delivery section, 23...nozzle, 30, 30c...mold clamping unit, 40...control section, 50...hopper, 90...molding mold, 91...fixed mold, 92...movable mold, 110...flat screw, 111...screw case, 112...drive motor, 121...groove forming surface, 122...center section, 123...groove, 124...material inlet, 125...ridge section, 130...barrel, 131...communicating hole, 132...check valve, 133...opposing surface, 134...guide groove, 140...heater, 151...injection cylinder, 152...plunger, 153...plunger Jar drive unit, 170...flow path, 201...tie bar, 210...toggle fixing plate, 220...fixed mounting unit, 230...movable mounting unit, 240...motor, 250...ball screw, 251...screw shaft, 252...ball screw nut, 260...crosshead, 270...toggle unit, 271...first member, 272...second member, 273...third member, 280...position detection unit, 290...fixed plate moving unit, 291...base, 292...first gear, 293...second gear, AX...axis, BX1...first rotating axis, BX2...second rotating axis, BX3...third rotating axis, BX4...fourth rotating axis, BX5...fifth rotating axis, C...bending angle, RX...rotating axis

Claims

1. An injection molding apparatus for injection molding a molded product using a mold consisting of a fixed mold and a movable mold, an injection unit that injects material for the molded article into the mold; a mold clamping unit to which the molding die is attached and which clamps the molding die; a control unit that controls the injection unit and the mold clamping unit, The mold clamping unit includes: A toggle fixing plate; a fixed mold mounting portion to which the fixed mold is attached; a movable mold mounting portion provided between the toggle fixing plate and the fixed mold mounting portion so as to be movable back and forth in a mold clamping direction, and to which the movable mold is attached; A motor and a ball screw attached to the toggle fixing plate and rotated by the drive of the motor; a crosshead that moves between the toggle fixing plate and the movable die mounting portion by rotation of the ball screw; a toggle portion connected to the toggle fixing plate, the movable mold mounting portion, and the crosshead, and configured to move the movable mold mounting portion along the mold clamping direction in response to movement of the crosshead; a position detection unit that detects the position of the crosshead, the control unit drives the motor to control the position of the crosshead based on the detection result of the position detection unit, thereby operating the toggle unit and clamping the fixed mold and the movable mold together. Injection molding equipment.

2. 2. The injection molding apparatus according to claim 1, The toggle portion is a first member connected to the toggle fixing plate via a first rotation shaft; a second member connected to the first member via a second rotation shaft and connected to the movable die mounting portion via a third rotation shaft; a third member connected to the crosshead and connected to the first member via a fourth rotation shaft; the control unit controls the position of the crosshead so that a line connecting the center of the first rotation shaft and the center of the second rotation shaft and a line connecting the center of the second rotation shaft and the center of the third rotation shaft are aligned in the same direction during a period in which the fixed mold and the movable mold are clamped together. Injection molding equipment.

3. 2. The injection molding apparatus according to claim 1, the control unit controls the position of the crosshead so that, during a period in which the fixed mold and the movable mold are clamped together, the fixed mold and the movable mold are clamped together with a first torque and then clamped together with a second torque smaller than the first torque. Injection molding equipment.

4. 2. The injection molding apparatus according to claim 1, The control unit a first control that drives the motor to control the position of the crosshead based on the detection result of the position detection unit, thereby operating the toggle unit and bringing the fixed die and the movable die into contact with each other; a second control that controls a torque value of the motor so that, after the first control, the fixed mold and the movable mold are clamped with a third torque and then clamped with a fourth torque greater than the third torque; After the second control, a third control is performed in which the motor is driven based on the detection result of the position detection unit to control the position of the crosshead so that the fixed mold and the movable mold are clamped with a fifth torque smaller than the third torque. Injection molding equipment.

5. 2. The injection molding apparatus according to claim 1, the mold clamping unit has a fixing plate moving part that moves the toggle fixing plate along the mold clamping direction, the control unit controls the fixed plate moving unit to move the toggle fixed plate in a direction in which the clamping pressure increases during a period in which the fixed mold and the movable mold are clamped together. Injection molding equipment.

6. A toggle fixing plate; a fixed mold mounting portion to which a fixed mold whose position is fixed during a mold clamping operation is mounted; a movable mold mounting portion provided between the toggle fixing plate and the fixed mold mounting portion so as to be movable back and forth in a mold clamping direction, and to which a movable mold is attached which is moved relatively to the fixed mold during the mold clamping operation; A motor and a ball screw attached to the toggle fixing plate and rotated by the drive of the motor; a crosshead that moves between the toggle fixing plate and the movable die mounting portion by rotation of the ball screw; a toggle portion connected to the toggle fixing plate, the movable mold mounting portion, and the crosshead, and configured to move the movable mold mounting portion along the mold clamping direction in response to movement of the crosshead; a position detection unit that detects the position of the crosshead; a control unit that drives the motor to control the position of the crosshead based on the detection result of the position detection unit, thereby operating the toggle unit and clamping the fixed mold and the movable mold. Mold clamping device.

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