Patent Publication Number: US-2022234263-A1

Title: Injection Molding Apparatus And Molding Die For Injection Molding

Description:
The present application is based on, and claims priority from JP Application Serial Number 2021-008562, filed Jan. 22, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an injection molding apparatus and a molding die for injection molding. 
     2. Related Art 
     JP-A-2020-157635 (PTL 1) discloses an injection molding apparatus including an ejector device for pushing out a molded article from a movable mold. In this injection molding apparatus, the ejector device includes an ejector pin and an ejector motor that is a component that moves the ejector pin. The ejector device is attached to a movable platen. When the ejector motor drives, the ejector pin advances into a cavity, and the molded article is pushed out from the movable mold. 
     In the injection molding apparatus as described in PTL 1, when a shape of the molded article is changed, it is necessary to change not only the molding die but also the component that moves the ejector pin, and therefore, it takes time and cost to change the shape of the molded article. 
     SUMMARY 
     According to a first aspect of the present disclosure, an injection mold apparatus is provided. The injection molding apparatus includes a fixed mold, a movable mold facing the fixed mold, a mold clamping unit configured to move the movable mold with respect to the fixed mold, and an injection unit configured to inject a molten material into a cavity defined by the fixed mold and the movable mold. At least one of the fixed mold and the movable mold is formed with a flow path communicating with the cavity, and a working fluid that pressurizes and pushes out a molded article in the cavity flows through the flow passage. 
     According to a second aspect of the present disclosure, a molding die for injection molding is provided. The molding die includes a fixed mold and a movable mold facing the fixed mold and configured to move with respect to the fixed mold. The fixed mold and the movable mold define a cavity to be filled with a molten material. At least one of the fixed mold and the movable mold is formed with a plurality of flow paths communicating with the cavity, and a working fluid that pressurizes and pushes out a molded article in the cavity flows through the plurality of flow paths. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view showing a schematic configuration of an injection molding apparatus according to a first embodiment. 
         FIG. 2  is a cross-sectional view showing the schematic configuration of the injection molding apparatus according to the first embodiment. 
         FIG. 3  is a perspective view showing a schematic configuration of a flat screw. 
         FIG. 4  is a plan view showing a schematic configuration of a barrel. 
         FIG. 5  is a cross-sectional view showing a schematic configuration of a molding die according to the first embodiment. 
         FIG. 6  is a plan view showing a schematic configuration of a movable mold according to the first embodiment. 
         FIG. 7  is a first view showing a state in which a molded article is pushed out. 
         FIG. 8  is a second view showing a state in which the molded article is pushed out. 
         FIG. 9  is a third view showing a state in which the molded article is pushed out. 
         FIG. 10  is a front view showing a schematic configuration of an injection molding apparatus according to a second embodiment. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     A. First Embodiment 
       FIG. 1  is a front view showing a schematic configuration of an injection molding apparatus  10  according to a first embodiment.  FIG. 1  shows arrows indicating X, Y, and Z directions that are orthogonal. The X direction and the Y direction are directions parallel to a horizontal plane, and the Z direction is a direction opposite to the gravity direction. X, Y, Z directions shown in  FIG. 2  and subsequent drawings correspond to the X, Y, Z directions shown in  FIG. 1 . In the following description, when a direction is specified, indicates a positive direction that is a direction indicated by an arrow, “−” indicates a negative direction that is a direction opposite to the direction indicated by the arrow, and positive and negative symbols are used together to indicate the directions. 
     The injection molding apparatus  10  includes an injection unit  100 , a mold clamping unit  200 , a molding die  300 , and a control unit  500 . In the present embodiment, the injection unit  100 , the mold clamping unit  200 , and the control unit  500  are fixed to a base  20 . The molding die  300  is attached to the mold clamping unit  200 . 
     A hopper  101  into which a molding material, which is a material of a molded article, is fed is coupled to the injection unit  100 . As the molding material, for example, a thermoplastic resin formed in a pellet shape is used. The molding material is processed into, for example, a pellet shape. 
     The injection unit  100  plasticizes at least a part of the molding material supplied from the hopper  101  to generate a molten material, and injects the molten material into the molding die  300 . The term “plasticize” means that heat is applied to the molding material having thermoplasticity to melt the molding material. The term “melt” means not only that the molding material having thermoplasticity is heated to a temperature equal to or higher than a melting point to be a liquid, but also means that the molding material having thermoplasticity is softened by being heated to a temperature equal to or higher than a glass transition point and exhibits fluidity. The molten material injected into the molding die  300  is cooled and solidified in the molding die  300  to form a molded article. 
     The control unit  500  is constituted by a computer including one or a plurality of processors, a main storage device, and an input and output interface that inputs a signal from the outside and outputs a signal to the outside. The control unit  500  controls the injection unit  100  and the mold clamping unit  200  by the processor reading and executing a program on the main storage device to manufacture a molded article. 
       FIG. 2  is a cross-sectional view showing the schematic configuration of the injection molding apparatus  10 .  FIG. 2  shows cross sections of the injection unit  100 , the mold clamping unit  200 , and the molding die  300 . The injection unit  100  includes a plasticizing unit  110 , an injection control mechanism  120 , and a nozzle  130 . 
     The plasticizing unit  110  has a function of plasticizing at least a part of the pellet-shaped molding material supplied from the hopper  101 , generating a paste-like molten material having fluidity, and supplying the molten material to the injection control mechanism  120 . In the present embodiment, the plasticizing unit  110  includes a screw driving unit  111 , a screw case  113 , a flat screw  115 , a barrel  116 , and a plasticizing heater  117 . 
     The screw driving unit  111  includes a motor and a speed reducer. The screw driving unit  111  is driven under the control of the control unit  500 . The screw driving unit  111  is coupled to the flat screw  115 . 
     The flat screw  115  is accommodated in a space surrounded by the screw case  113  and the barrel  116 . The flat screw  115  accommodated in the space is rotated by a rotational driving force from the screw driving unit  111 . 
     A communication hole  118  penetrating the barrel  116  is provided in a central portion of the barrel  116 . An injection cylinder  121 , which will be described later, is coupled to the communication hole  118 . The communication hole  118  is provided with a check valve  124  upstream of the injection cylinder  121 . 
     The plasticizing heater  117  is embedded in the barrel  116 . The plasticizing heater  117  is supplied with electric power and generates heat. A temperature of the plasticizing heater  117  is controlled by the control unit  500 . 
       FIG. 3  is a perspective view showing a schematic configuration of the flat screw  115 . The flat screw  115  has a substantially columnar shape. A height of the flat screw  115  in a direction along a central axis RX is smaller than a diameter of the flat screw  115 . The flat screw  115  has a groove forming surface  150  facing the barrel  116 . The groove forming surface  150  is formed with grooves  152  extending spirally around a central portion  151 . The grooves  152  communicate with a material inlet  153  formed in a side surface of the flat screw  115 . The molding material supplied from the hopper  101  is introduced into the grooves  152  from the material inlet  153 . In the present embodiment, three grooves  152  are formed in the groove forming surface  150 . The grooves  152  are separated by ridge portions  154 . The number of grooves  152  is not limited to three, and may be one, two, four, or more. A shape of the grooves  152  is not limited to a spiral shape, and may be a spiral shape or an involute curve shape, or may be a shape drawing an arc from the central portion  151  toward an outer periphery. 
       FIG. 4  is a plan view showing a schematic configuration of the barrel  116 . The barrel  116  has a facing surface  160  facing the groove forming surface  150  of the flat screw  115 . The communication hole  118  is provided at a center of the facing surface  160 . The communication hole  118  is provided on an extension line of the central axis RX of the flat screw  115 . A plurality of guide grooves  161  coupled to the communication hole  118  and extending in a spiral shape from the communication hole  118  toward the outer periphery are formed in the facing surface  160 . The guide grooves  161  provided in the facing surface  160  may not be coupled to the communication hole  118 . The guide grooves  161  may not be provided in the facing surface  160 . 
     The molding material supplied to the grooves  152  of the flat screw  115  is plasticized between the flat screw  115  and the barrel  116  by the rotation of the flat screw  115  and the heating from the plasticizing heater  117 , flows along the grooves  152  and the guide grooves  161  by the rotation of the flat screw  115 , and is guided to the central portion  151  of the flat screw  115 . The molten material flowing into the central portion  151  is guided from the communication hole  118  to the injection control mechanism  120 . 
     As shown in  FIG. 2 , the injection control mechanism  120  includes the injection cylinder  121 , a plunger  122 , and a plunger drive unit  123 . The injection control mechanism  120  has a function of injecting the molten material supplied from the plasticizing unit  110  into the injection cylinder  121  from the nozzle  130 . The molten material injected from the nozzle  130  is filled in a cavity Cv of the molding die  300  to be described later. 
     The injection cylinder  121  is a substantially cylindrical member coupled to the communication hole  118  of the barrel  112 , and includes the plunger  122  therein. The plunger  122  slides in the injection cylinder  121  by the plunger drive unit  123  constituted by a motor, and pressure-feeds the molten material in the injection cylinder  121  to the nozzle  130 . The plunger drive unit  123  is driven under the control of the control unit  500 . 
     The molding die  300  includes a fixed mold  310  and a movable mold  320  facing the fixed mold  310 . When the fixed mold  310  and the movable mold  320  come into contact with each other, the cavity Cv is defined between the fixed mold  310  and the movable mold  320 . The cavity Cv is a space having a shape corresponding to the shape of the molded article. The molten material is injected into the cavity Cv from the nozzle  130 . The molten material filled in the cavity Cv is cooled and solidified to become the molded article. In the present embodiment, the molding die  300  is provided with a guide pin  305  that prevents positional deviation of the movable mold  320  with respect to the fixed mold  310 . The guide pin  305  may not be provided. 
     The mold clamping unit  200  has a function of moving the movable mold  320  with respect to the fixed mold  310 , that is, a function of opening and closing the molding die  300 . In the present embodiment, the mold clamping unit  200  includes a fixed platen  210 , a movable platen  220 , a tie bar  230 , a ball screw portion  240 , and a mold driving unit  250 . 
     The injection unit  100 , the fixed platen  210 , and the movable platen  220  are arranged in this order along the X direction. The fixed platen  210  is fixed to a distal end portion of the tie bar  230  provided along the X direction. The fixed mold  310  is fixed to a surface of the fixed platen  210  on a movable platen  220  side by, for example, bolts or clamps. 
     The movable platen  220  is movable along the tie bar  230 . The movable platen  220  is coupled to the ball screw portion  240  provided along the X direction. The movable mold  320  is fixed to the surface of the movable platen  220  on the fixed platen  210  side by, for example, bolts or clamps. 
     The mold driving unit  250  includes a motor and a speed reducer. The mold driving unit  250  is driven under the control of the control unit  500 . The mold driving unit  250  is coupled to the movable mold  320  via the ball screw portion  240 . The mold driving unit  250  opens and closes the molding die  300  by rotating the ball screw portion  240  and moving the movable mold  320  fixed to the movable platen  220  with respect to the fixed mold  310  fixed to the fixed platen  210 . 
       FIG. 5  is a cross-sectional view showing a schematic configuration of the molding die  300 .  FIG. 6  is a plan view showing a schematic configuration of the movable mold  320 .  FIG. 5  shows the molding die  300  in a clamped state. In the present embodiment, the molding die  300  includes the fixed mold  310 , the movable mold  320 , and a pressurizing unit  340 . 
     In the present embodiment, the movable mold  320  includes a nested portion  321  and an accommodating portion  322 . The accommodating portion  322  has a cylindrical shape. The nested portion  321  is accommodated inside the accommodating portion  322 . The nested portion  321  includes a concave portion  325  on a surface facing the fixed mold  310 . When the fixed mold  310  and the nested portion  321  come into contact with each other, the cavity Cv is defined by the fixed mold  310  and the concave portion  325 . The fixed mold  310  is provided with a through hole into which the nozzle  130  is inserted, and the molten material is injected into the cavity Cv from the nozzle  130 . 
     The nested portion  321  has a plurality of flow paths  330  communicating with the cavity Cv. In the present embodiment, as shown in  FIG. 6 , sixteen flow paths  330  are provided in the nested portion  321 . As shown in  FIG. 5 , each flow path  330  penetrates the nested portion  321  along the X direction. The opening shape of each flow path  330  is circular. An opening portion on a cavity Cv side of each flow path  330  has a size capable of preventing the molten material injected into the cavity Cv from flowing into the flow path  330 . In the present embodiment, a diameter of the opening portion of each flow path  330  on the cavity Cv side is a few micrometers to hundreds of micrometers. It is preferable that the smaller the viscosity of the molten material injected into the cavity Cv, the smaller the diameter of the opening portion of each flow path  330  on the cavity Cv side. The number of the flow paths  330  is not limited to two or more, and may be one. The opening shape of the flow path  330  may not be circular, and may be, for example, an elliptical shape or a polygonal shape such as a square shape. 
     In each of the flow paths  330 , a working fluid that pressurizes and pushes out the molded article molded in the cavity Cv flows toward the cavity Cv. In the present embodiment, compressed air is used as the working fluid. As the working fluid, a gas other than the compressed air or a liquid such as oil may be used. 
     The pressurizing unit  340  includes a cylinder portion  341 , a piston portion  342 , an ejector plate  343 , a return pin  344 , and a return spring  345 . The cylinder portion  341  is disposed on an opposite side of the cavity Cv with respect to the nested portion  321  and the accommodating portion  322 . The cylinder portion  341  is fixed to the accommodating portion  322  by, for example, a bolt. The cylinder portion  341  has a cylindrical shape. An internal space of the cylinder portion  341  communicates with the flow path  330  provided in the nested portion  321 . 
     The piston portion  342  is disposed in the internal space of the cylinder portion  341 . The piston portion  342  has an outer shape along an inner wall surface  349  of the cylinder portion  341 . The piston portion  342  moves relatively with respect to the cylinder portion  341  in the X direction. In the present embodiment, the inner wall surface  349  of the cylinder portion  341  has a cylindrical shape, and the piston portion  342  has a columnar shape. The inner wall surface  349  of the cylinder portion  341  may be formed in a prismatic shape, and the piston portion  342  may be formed in a prismatic shape. 
     The ejector plate  343  is disposed on an opposite side of the cavity Cv with respect to the cylinder portion  341 . The ejector plate  343  is disposed with a gap between the ejector plate  343  and the cylinder portion  341 . The piston portion  342  is fixed to a central portion of the ejector plate  343 . The return pin  344  is fixed to an outer peripheral portion of the ejector plate  343 . 
     The return pin  344  is a rod-shaped member provided along the X direction. The return pin  344  is inserted through a through hole provided in the cylinder portion  341  and the accommodating portion  322  of the movable mold  320 . The ejector plate  343  and the return pin  344  relatively move in the X direction with respect to the cylinder portion  341  together with the piston portion  342 . 
     The return spring  345  is disposed between the cylinder portion  341  and the ejector plate  343 . The return spring  345  is a compression coil spring that expands and contracts along the X direction. The return spring  345  is provided along the return pin  344 . One end of the return spring  345  is in contact with the cylinder portion  341 , and the other end of the return spring  345  is in contact with the ejector plate  343 . The return spring  345  pushes back the ejector plate  343  that approached the cylinder portion  341 . 
     In the present embodiment, the fixed mold  310  and the accommodating portion  322  of the movable mold  320  are formed of a metal material. The fixed mold  310  and the accommodating portion  322  are manufactured by performing cutting, electric discharge machining, or the like on a mass of a metal material. As a metal material for forming the fixed mold  310  and the accommodating portion  322 , for example, tool steel or stainless steel can be used. The fixed mold  310  may be formed of a resin material or a ceramic material instead of a metal material. The accommodating portion  322  may be formed of a resin material or a ceramic material instead of a metal material. 
     In the present embodiment, the nested portion  321  of the movable mold  320  is formed of a resin material. The nested portion  321  is manufactured by stacking layers of a resin material using a three-dimensional shaping device. Therefore, the nested portion  321  has a structure in which a plurality of layers are stacked. As the resin material for forming the nested portion  321 , for example, a cyclic olefin copolymer (COC), polybenzimidazole (PBI), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), or polyacetal (POM), polyamide (PA66) can be used. When the molding material is a crystalline resin material, the nested portion  321  is preferably formed of a crystalline resin material having a higher melting point than a melting point of the molding material or an amorphous resin material having a higher glass transition point than the melting point of the molding material. When the molding material is an amorphous resin material, the nested portion  321  is preferably formed of a crystalline resin material having a higher melting point than a glass transition point of the molding material or an amorphous resin material having a higher glass transition point than the glass transition point of the molding material. The nested portion  321  may be manufactured without using the three-dimensional shaping device. The nested portion  321  may be formed of a metal material or a ceramic material instead of a resin material. The nested portion  321  and the accommodating portion  322  may be formed of the same material. 
     In the present embodiment, the cylinder portion  341 , the piston portion  342 , the ejector plate  343 , and the return pin  344  are formed of a metal material. As a metal material for forming the cylinder portion  341 , the piston portion  342 , the ejector plate  343 , and the return pin  344 , for example, tool steel or stainless steel can be used. The cylinder portion  341 , the piston portion  342 , the ejector plate  343 , and the return pin  344  may be formed of a resin material or a ceramic material instead of a metal material. 
       FIG. 7  is a first view showing a state in which a molded article MD is pushed out.  FIG. 8  is a second view showing a state in which the molded article MD is pushed out.  FIG. 9  is a third view showing a state in which the molded article MD is pushed out. 
     As shown in  FIG. 5 , before the molten material is injected into the cavity Cv, the cavity Cv and an inside of the cylinder portion  341  communicate with each other via the flow paths  330 . In this state, pressure of the air in the cylinder portion  341  is the same as the atmospheric pressure. 
     As shown in  FIG. 7 , when the molten material is injected into the cavity Cv from the nozzle  130 , the opening portions on the cavity Cv side of the flow paths  330  are closed by the molten material. Thereafter, the molten material of the cavity Cv is cooled and solidified to become the molded article MD. 
     As shown in  FIG. 8 , when the molding die  300  is opened, the movable mold  320  and the cylinder portion  341  move away from the fixed mold  310  by the movement of the movable platen  220  of the mold clamping unit  200 . At this time, the piston portion  342 , the ejector plate  343 , and the return pin  344  are biased by the return spring  345  and move together with the movable mold  320  and the cylinder portion  341 . 
     As shown in  FIG. 9 , when the ejector plate  343  comes into contact with the distal end portion of the ball screw portion  240 , the piston portion  342 , the ejector plate  343 , and the return pin  344  stop moving. In contrast, the movable mold  320  and the cylinder portion  341  move further away from the fixed mold  310  by the movement of the movable platen  220 . Therefore, the piston portion  342  slides on the inner wall surface  349  of the cylinder portion  341 . Since the opening portions on the cavity Cv side of the flow paths  330  are closed by the molded article MD, air in the cylinder portion  341  and the flow path  330  is compressed by relative movement of the piston portion  342  with respect to the cylinder portion  341 . The molded article MD is pushed toward the fixed mold  310  by the pressure from the compressed air in the flow path  330 . When the pressure of the compressed air exceeds a predetermined pressure, the molded article MD is released. The molded article MD that has been released is transported by, for example, a take-out robot installed adjacent to the injection molding apparatus  10 . 
     When the molded article MD is taken out of the concave portion  325 , the opening portions on the cavity Cv side of the flow paths  330  are opened, so that the pressure of the air in the flow path  330  and the cylinder portion  341  returns to the same pressure as the atmospheric pressure. When the molding die  300  is clamped again, the piston portion  342 , the ejector plate  343  and the return pin  344  are pushed back by the return spring  345  and return to the state shown in  FIG. 5 . 
     According to the injection molding apparatus  10  of the present embodiment described above, the molded article MD can be released by being pressurized by the compressed air flowing through the flow path  330  provided in the movable mold  320  without using an ejector pin. When changing the shape of the molded article MD, the molded article MD after change can be molded and released only by changing the movable mold  320  without changing the pressurizing unit  340 . Therefore, when the shape of the molded article MD is changed, it is possible to prevent the labor and cost for changing components other than the fixed mold  310  and the movable mold  320 . In particular, in the present embodiment, the flow paths  330  are provided in the nested portion  321  having a surface that defines the cavity Cv in the movable mold  320 . Therefore, when the shape of the molded article MD is changed, the accommodating portion  322  can be used, so that the material cost for manufacturing the movable mold  320  can be reduced. 
     In the present embodiment, since the movable mold  320  is provided with the plurality of flow paths  330 , it is possible to pressurize a plurality of portions of the molded article MD. Therefore, the molded article MD can be effectively released. 
     In the present embodiment, the compressed air can be pumped to the flow paths  330  by the relative movement between the cylinder portion  341  and the piston portion  342 . Therefore, the molded article MD can be released with a simple configuration. In particular, in the present embodiment, the mold clamping unit  200  moves the movable mold  320 , so that the piston portion  342  relatively moves with respect to the cylinder portion  341  fixed to the movable mold  320 , and the compressed air is pumped to the flow paths  330 . Therefore, the compressed air can be pumped to the flow paths  330  without separately providing a device for relatively moving the piston portion  342  with respect to the cylinder portion  341 . 
     B. Second Embodiment 
       FIG. 10  is a side view showing a schematic configuration of an injection molding apparatus  10   b  according to a second embodiment. The second embodiment is different from the first embodiment in that the pressurizing unit  340  shown in  FIG. 5  is not attached to the movable mold  320  and compressed air is supplied to the flow paths  330  by a pressurizing pump  400 . Other configurations are the same as those of the first embodiment unless otherwise specified. 
     In the present embodiment, the pressurizing pump  400  is coupled to the flow paths  330  via a flexible tube  410 . The pressurizing pump  400  is fixed in the base  20 . The pressurizing pump  400  is driven under the control of the control unit  500 . In the present embodiment, the compressed air is used as a working fluid, and therefore, for example, a centrifugal compressor or a turbo compressor can be used as the pressurizing pump  400 . When a liquid such as oil is used as the working fluid, for example, a spiral pump, a gear pump, or a piston pump may be used as the pressurizing pump  400 . When the mold is opened, the control unit  500  drives the pressurizing pump  400  to pressure-feed the compressed air to the flow paths  330 , thereby releasing the molded article MD molded in the cavity Cv. The pressurizing pump  400  may be referred to as a pressurizing unit. 
     According to the injection molding apparatus  10   b  of the present embodiment described above, the compressed air is pressure-fed to the flow paths  330  by the pressurizing pump  400  driven under the control of the control unit  500 , and the molded article MD can be released. In particular, in the present embodiment, the control unit  500  can adjust the pressure of the compressed air supplied to the flow paths  330  by adjusting an output of the pressurizing pump  400 . 
     C. Other Embodiments 
     (C1) In the injection molding apparatuses  10  and  10   b  of the above-described embodiments, the flow paths  330  through which the working fluid flows toward the cavity Cv are provided in the movable mold  320 . Alternatively, the flow paths  330  may be provided in the fixed mold  310 . In this case, for example, the molded article can be pressurized and pushed out by pressure-feeding the working fluid to the flow paths  330  provided in the fixed mold  310  using the pressurizing pump  400  shown in  FIG. 10 . In addition, the flow paths  330  may be provided in the fixed mold  310  and the movable mold  320 . The working fluid can be pressure-fed to the flow paths  330  provided in the fixed mold  310  by using, for example, the pressurizing pump  400 . The working fluid can be pressure-fed to the flow paths  330  provided in the movable mold  320  by using, for example, the pressurizing unit  340  or the pressurizing pump  400 . By pressure-feeding the working fluid to the flow paths  330  provided in one of the fixed mold  310  and the movable mold  320  to which the molded product is attached, the molded article can be pressurized and pushed out. 
     (C2) In the injection molding apparatuses  10  and  10   b  in the above-described embodiments, the pressurizing unit  340  and the pressurizing pump  400  may not be provided in the injection molding apparatuses  10  and  10   b . In this case, for example, a pipeline in a factory through which the compressed air flows and the flow paths  330  of the molding die  300  may be coupled via a valve that is opened and closed under the control of the control unit  500 , and the compressed air that is the working fluid may be supplied to the flow paths  330  by opening the valve. 
     (C3) In the injection molding apparatuses  10  and  10   b  of the embodiments described above, the movable mold  320  has a nested structure in which the movable mold  320  is divided into the nested portion  321  and the accommodating portion  322 . In contrast, the movable mold  320  may not have a nested structure. That is, the nested portion  321  and the accommodating portion  322  may be integrated. The nested portion  321 , the accommodating portion  322 , and the cylinder portion  341  may be integrated, or the nested portion  321  and the accommodating portion  322  may not be integrated, and the accommodating portion  322  and the cylinder portion  341  may be integrated. The fixed mold  310  may have a nested structure. 
     (C4) In the injection molding apparatuses  10  and  10   b  of the embodiments described above, the movable mold  320  is manufactured by a three-dimensional shaping device, and has a structure in which a plurality of layers made of a resin material are stacked. In contrast, the movable mold  320  may not have a structure in which a plurality of layers are stacked. The fixed mold  310  may have a structure in which a plurality of layers made of a resin material are stacked by being manufactured by a three-dimensional shaping device. 
     D. Other Embodiments 
     The present disclosure is not limited to the embodiments described above, and can be implemented in various forms without departing from the scope of the present disclosure. For example, the present disclosure can be implemented in the following aspects. In order to solve a part or all of problems of the present disclosure, or to achieve a part or all of effects of the present disclosure, technical features in the above-described embodiments corresponding to technical features in the following aspects can be replaced or combined as appropriate. Unless described as necessary in the present specification, the technical characteristics can be deleted as appropriate. 
     (1) According to a first aspect of the present disclosure, an injection mold apparatus is provided. The injection molding apparatus includes a fixed mold, a movable mold facing the fixed mold, a mold clamping unit configured to move the movable mold with respect to the fixed mold, and an injection unit configured to inject a molten material into a cavity defined by the fixed mold and the movable mold. At least one of the fixed mold and the movable mold is formed with a flow path communicating with the cavity, and a working fluid that pressurizes and pushes out a molded article in the cavity flows through the flow passage. 
     According to the injection molding apparatus of this aspect, the molded article can be pressurized and pushed out by the working fluid flowing through the flow path provided in the fixed mold or the working fluid flowing through the flow path provided in the movable mold without using an ejector pin. Therefore, when the shape of the molded article is changed, it is possible to prevent the labor and cost for changing components other than the fixed mold and the movable mold. 
     (2) In the injection molding apparatus according to the above aspect, a plurality of flow paths may be formed in at least one of the fixed mold and the movable mold. 
     According to the injection molding apparatus of this aspect, since a plurality of portions of the molded article can be pressurized, the molded article can be effectively pushed out. 
     (3) The injection molding apparatus according to the above aspect may further include a pressurizing unit configured to pressure-feed the working fluid to the flow path. 
     According to the injection molding apparatus of this aspect, the molded article can be pushed out by pressure-feeding the working fluid from the pressurizing unit to the flow path. 
     (4) In the injection molding apparatus according to the aspect described above, the pressurizing unit may include a cylinder portion communicating with the flow path and a piston portion disposed in the cylinder portion, and may pressure-feed the working fluid to the flow path by relative movement of the piston portion with respect to the cylinder portion. 
     According to the injection molding apparatus of this aspect, the working fluid can be pressure-fed to the flow path by the relative movement between the cylinder portion and the piston portion. 
     (5) In the injection molding apparatus of the above aspect, the flow path may be formed in the movable mold, and the mold clamping unit may relatively move the piston portion with respect to the cylinder portion by moving the cylinder portion together with the movable mold. 
     According to the injection molding apparatus of this aspect, the cylinder portion and the piston portion can be relatively moved by the mold clamping unit without separately providing a device for relatively moving the cylinder portion and the piston portion. 
     (6) In the injection molding apparatus according to the aspect described above, at least one of the fixed mold and the movable mold may include a nested portion that defines the cavity and an accommodating portion that accommodates the nested portion. 
     According to the injection molding apparatus of this aspect, when shapes of molded articles are made different, components other than the nested portion can be used. 
     (7) In the injection molding apparatus according to the above aspect, at least one of the fixed mold and the movable mold may have a structure in which a plurality of layers are stacked. 
     According to the injection molding apparatus of this aspect, a fixed mold or a movable mold in which a plurality of layers are stacked can be manufactured using a three-dimensional shaping device. 
     (8) According to a second aspect of the present disclosure, a molding die for injection molding is provided. The molding die includes a fixed mold and a movable mold facing the fixed mold and configured to move with respect to the fixed mold. The fixed mold and the movable mold define a cavity to be filled with a molten material. At least one of the fixed mold and the movable mold is formed with a plurality of flow paths communicating with the cavity, and a working fluid that pressurizes and pushes out a molded article in the cavity flows through the plurality of flow paths. 
     According to the molding die of this aspect, the molded article can be pressurized and pushed out by the working fluid flowing through the flow paths provided in the fixed mold or the working fluid flowing through the flow paths provided in the movable mold without using an ejector pin. Therefore, when the shape of the molded article is changed, it is possible to prevent the labor and cost for changing components other than the fixed mold and the movable mold. 
     The present disclosure can be implemented in various aspects other than the injection molding apparatus. For example, the present disclosure can be implemented in the form of a molding die for injection molding or the like.