Injection molding machine

Abstract

The invention relates to an injection molding machine capable of suppressing the pressure of a first injection member when a molding material is extruded. An injection molding machine (1) is provided with: a storage cylinder (10) to which molten resin is supplied; a first injection member (12) provided in the reservoir cylinder (10) so as to be capable of advancing and retreating; an injection cylinder (20) to which the molten resin extruded from the storage cylinder (10) is supplied; a second injection member (22) provided inside the injection cylinder (20) so as to be capable of advancing and retreating; and a control unit (80) that controls the operation of the first injection member (12) and the second injection member (22). The control unit (80) controls a metering step in which the molten resin is supplied to the injection cylinder (20) by the advancement of the first injection member (12), and in the metering step, the second injection member (22) is retracted in accordance with the advancement of the first injection member (12).

Description

Technical Field

[0001] This application claims priority based on Japanese Patent Application No. 2023-174293 filed on October 6, 2023. The entire contents of the Japanese Patent Application are incorporated herein by reference.

[0002] The invention relates to an injection molding machine. Background Art

[0003] Injection molding machines that use two cylinders to inject molding material into a mold device are known in the past. For example, Patent Document 1 discloses an injection molding machine that includes a first cylinder (storage cylinder) and a second cylinder (injection cylinder) to which molten resin, a molding material, is supplied.

[0004] The injection molding machine is a machine that discharges molten resin from the front end of the first cylinder by advancing the first injection component (first plunger) of the first cylinder, and accumulates the molten resin in front of the internal space of the second cylinder. Then, the injection molding machine advances the second injection component (second plunger) of the second cylinder to inject the molten resin accumulated in front of the second cylinder into the mold device.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2022-27158

[0006] However, in the injection molding machine having two cylinders as described above, when the molding material is supplied from the first cylinder to the second cylinder, the second injection part is moved backward by the pressure of the molding material flowing into the second cylinder. At this time, in addition to the force of squeezing the molten resin from the first cylinder, the first injection part also needs a force to move the second injection part backward, and the pressure applied to the first injection part increases. In the injection molding machine, due to the increase in the pressure of the first injection part, the first injection part or the first cylinder is easily damaged (durability is reduced), and other undesirable conditions occur. Summary of the invention

[0007] The present invention provides an injection molding machine capable of suppressing the pressure of a first injection part during extrusion of a molding material.

[0008] According to one embodiment of the present invention, there is provided an injection molding machine, comprising: a first cylinder body, to which molten resin is supplied; a first injection component, which is arranged in the first cylinder body so as to be able to move forward and backward; a second cylinder body, to which the molten resin extruded from the first cylinder body is supplied; a second injection component, which is arranged in the second cylinder body so as to be able to move forward and backward; and a control unit, which controls the movement of the first injection component and the second injection component, the control unit controls a metering process for supplying the molten resin to the second cylinder body by advancing the first injection component, and in the metering process, the second injection component is retreated in correspondence with the advancement of the first injection component.

[0009] Effects of the Invention

[0010] According to one embodiment, the pressure of the first injection component during extrusion of the molding material can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a side view showing the overall structure of the injection molding machine system according to the first embodiment.

[0012] Figure 2 It is a cross-sectional view schematically showing an injection device of the injection molding machine according to the first embodiment.

[0013] Figure 3 This is a flowchart showing the operation of the injection device in the injection molding machine.

[0014] Figure 4 (A) is a cross-sectional view showing the operation of the metering process of the injection device. Figure 4 (B) is a diagram showing the operation of the injection process of the injection device.

[0015] Figure 5 It is a cross-sectional view showing the operation of discharging molten resin in the injection device.

[0016] Figure 6 (A) is a timing chart showing the operation of each plunger in the metering process of the injection device according to the embodiment. Figure 6 (B) is a timing chart showing the operation of each plunger in the metering process of the injection device according to the reference example.

[0017] Figure 7 It is a cross-sectional view schematically showing an injection device of an injection molding machine according to a second embodiment.

[0018] Explanation of symbols

[0019] 1, 1A-injection molding machine, 10-storage cylinder, 12, 13-first injection component, 20-injection cylinder, 22-second injection component, 80-control unit. DETAILED DESCRIPTION

[0020] Hereinafter, the mode for implementing the present invention will be described with reference to the drawings. In each of the drawings, the same components are denoted by the same reference numerals, and repeated description may be omitted.

[0021] <Injection molding machine system S>

[0022] Figure 1 1 is a side view showing the overall structure of the injection molding machine system S according to the first embodiment. Figure 1As shown, the injection molding machine system S according to the first embodiment includes an injection molding machine 1 , a molten resin supply device 6 , a molten resin supply path 7 , and a control valve 8 .

[0023] The injection molding machine 1 includes a clamping device 2 for opening and closing a mold device (not shown) and an injection device 3 for injecting a molding material into a cavity space of the mold device. In addition, the injection molding machine 1 has an ejector device (not shown) for ejecting a molded product molded by the mold device, a moving device (not shown) for moving the injection device 3 forward and backward relative to the mold device, and a frame 5 for supporting various components of the injection molding machine 1. In addition, the injection molding machine 1 has a controller 4 for controlling various components of the injection molding machine 1.

[0024] The mold clamping device 2 sequentially performs a mold closing process for bringing the movable mold into contact with the fixed mold, a pressurizing process for increasing the mold clamping force, a mold clamping process for maintaining the mold clamping force, a depressurizing process for reducing the mold clamping force, and a mold opening process for separating the movable mold from the fixed mold according to control instructions from the controller 4.

[0025] The injection device 3 performs metering, filling, and pressure-maintaining steps according to control instructions from the controller 4. Hereinafter, the filling and pressure-maintaining steps are collectively referred to as injection steps. The operation of the injection device 3 will be described in detail later.

[0026] The ejector device performs the following ejection process according to the control command of the controller 4: the ejector rod (not shown) is moved forward from the standby position to the ejection position to eject the molded product, and then the ejector rod is moved back to the original standby position.

[0027] The moving device moves the injection device 3 forward and backward relative to the mold device. When the injection device 3 is moved forward toward the mold device, the injection device 3 is pressed against the fixed mold of the mold device. When the injection device 3 is moved backward, the injection device 3 is away from the fixed mold of the mold device.

[0028] The controller 4 repeatedly manufactures the molded product by repeatedly performing the above-mentioned metering process, mold closing process, pressure increasing process, mold closing process, filling process, pressure holding process, cooling process, pressure releasing process, mold opening process and ejection process. A series of actions for obtaining a molded product, such as the action from the start of a metering process to the start of the next metering process, is also referred to as a molding cycle. In addition, the time required for one molding cycle is also referred to as the molding cycle time.

[0029] For example, a molding cycle sequentially performs metering process, mold closing process, pressure increasing process, mold closing process, filling process, pressure holding process, cooling process, pressure releasing process, mold opening process and ejection process. The order here is the order in which each process starts. The filling process, pressure holding process and cooling process are performed during the mold closing process. The start of the mold closing process can coincide with the start of the filling process. The end of the pressure releasing process coincides with the start of the mold opening process.

[0030] In addition, in order to shorten the molding cycle time, multiple processes can be performed simultaneously. For example, the metering process can be performed during the cooling process of the previous molding cycle, or during the mold closing process. In this case, the mold closing process can be performed at the beginning of the molding cycle. In addition, the filling process can be started during the mold closing process. In addition, the ejection process can be started during the mold opening process. A reversing valve 50 is provided in the injection device 3 (refer to Figure 2 ), the mold opening process can be started in the metering process. The reason is that even if the mold opening process is started in the metering process, if the reversing valve 50 closes the flow path of the injection device 3, the molding material will not leak from the nozzle 40 of the injection device 3.

[0031] In addition, a primary molding cycle may include processes other than the metering process, the mold closing process, the pressure increasing process, the mold clamping process, the filling process, the pressure holding process, the cooling process, the pressure releasing process, the mold opening process, and the ejection process.

[0032] The molten resin supply device 6 supplies the molten molding material, i.e., molten resin (liquid molding material), to the injection device 3. Specifically, the molten resin supply device 6 melts the solid recovered resin (for example, a resin obtained by pelletizing a resin containing polyethylene terephthalate (PET)) while stirring it, and supplies it to the downstream molten resin supply path 7. In addition, the molten resin supply device 6 may be a pressure-feeding device that continuously feeds the molten resin to the molten resin supply path 7, thereby applying a pressure-feeding force to the fed molten resin to pressure-feed the molten resin.

[0033] The molten resin supply path 7 is a path for supplying molten resin from the molten resin supply device 6 to the injection device 3. The molten resin supply path 7 may include, for example, a pipe through which the molten resin flows, an insulating material covering the pipe, a heater for keeping the molten resin flowing in the pipe warm, and the like.

[0034] The control valve 8 is provided on the molten resin supply path 7, is communicably connected to the controller 4, and switches supply and stop of the molten resin to the injection device 3. As the control valve 8, for example, an on-off valve can be applied.

[0035] In addition, Figure 1 The middle figure shows a structure in which one injection molding machine 1 is connected to the molten resin supply path 7, but the present invention is not limited thereto, and the injection molding machine system S may also be a structure in which a plurality of injection molding machines 1 are connected to the molten resin supply path 7. Figure 1The middle figure shows a structure in which one molten resin supply device 6 is connected to the molten resin supply path 7 , but the present invention is not limited thereto, and the injection molding machine system S may also have a structure in which a plurality of molten resin supply devices 6 are connected to the molten resin supply path 7 .

[0036] <Structure of injection device 3 according to first embodiment>

[0037] Next, refer to Figure 2 The injection device 3 of the injection molding machine 1 will be described. Figure 2 It is a cross-sectional view schematically showing the injection device 3 of the injection molding machine 1 according to the first embodiment.

[0038] The injection device 3 of the injection molding machine 1 uses two cylinders to inject the molding material, i.e., molten resin, into the above-mentioned mold device. Specifically, the injection device 3 includes a storage cylinder (first cylinder) 10, a first injection component 12, an injection cylinder (second cylinder) 20, and a second injection component 22. In addition, the injection device 3 includes a first injection component driving unit 15 that operates the first injection component 12 and a second injection component driving unit 25 that operates the second injection component 22. In addition, the injection device 3 has a supply connector 30, a connecting unit 35, a nozzle 40, a reversing valve 50, a discharge unit 60, a discharge valve 70, and a control unit 80.

[0039] The storage cylinder 10 is formed in a cylindrical shape extending in the horizontal direction. A discharge valve 70 is connected to the front end of the storage cylinder 10, and a first injection member driving unit 15 is provided at the base end of the storage cylinder 10. The molten resin is supplied from the front end to the internal space of the storage cylinder 10 through the discharge valve 70. A heating device (not shown) for keeping or heating the molten resin supplied to the internal space may be provided on the cylinder wall constituting the storage cylinder 10.

[0040] The first injection component 12 is formed as a solid rod component and is configured as a plunger that is arranged in the internal space of the storage cylinder 10 so as to be able to move forward and backward. The axis of the first injection component 12 is coaxial with the axis of the storage cylinder 10. The outer peripheral surface of the first injection component 12 is a smooth curved surface, and its outer diameter is set to be the same as or slightly smaller than the inner diameter of the storage cylinder 10. As a result, the first injection component 12 can move forward and backward (slide) relative to the storage cylinder 10. The first injection component 12 moves the molten resin supplied to the internal space of the storage cylinder 10 as it moves forward and backward.

[0041] The first injection member driving unit 15 closes the base end of the storage cylinder 10 and holds the base end of the first injection member 12. The first injection member driving unit 15 includes an advance / retract motor 16, an encoder 17, and a pressure detection unit 18, for example.

[0042] The advance / retract motor 16 advances / retracts the first injection component 12 along the axis of the storage cylinder 10. A motion conversion mechanism is provided between the first injection component 12 and the advance / retract motor 16 to convert the rotational motion of the advance / retract motor 16 into the linear motion of the first injection component 12. The motion conversion mechanism may be, for example, a ball screw.

[0043] The encoder 17 detects the rotation of the forward / retract motor 16 and sends the detection signal to the control unit 80. The control unit 80 calculates the position and moving speed of the first injection component 12 based on the detection signal of the encoder 17 and controls the operation of the first injection component 12 using the calculation results.

[0044] The pressure detection unit 18 is provided on the transmission path between the advance / retract motor 16 and the first injection component 12, detects the force transmitted between the advance / retract motor 16 and the first injection component 12, and sends the detection signal thereof to the control unit 80. The control unit 80 calculates the pressure of the first injection component 12 based on the detected force, and adjusts or monitors the pressure received by the first injection component 12 from the molten resin (back pressure on the first injection component 12), the pressure acting on the molten resin from the first injection component 12, and the like.

[0045] On the other hand, the injection cylinder 20 is formed into a cylindrical shape extending parallel to (horizontally) the storage cylinder 10. A reversing valve 50 is connected to the front end of the injection cylinder 20, and a second injection member driving unit 25 is provided at the base end of the injection cylinder 20. The molten resin is supplied from the front end side to the internal space of the injection cylinder 20 through the reversing valve 50. A heating device (not shown) for keeping or heating the molten resin supplied to the internal space may be provided on the cylinder wall constituting the injection cylinder 20.

[0046] Similar to the first injection component 12, the second injection component 22 is formed as a solid rod component and is disposed in the internal space of the injection cylinder 20 so as to be able to move forward and backward. The axis of the second injection component 22 is coaxial with the axis of the injection cylinder 20. The outer peripheral surface of the second injection component 22 is a smooth curved surface, and its outer diameter is set to be the same as or slightly smaller than the inner diameter of the injection cylinder 20. Thus, the second injection component 22 can move forward and backward (slide) relative to the injection cylinder 20. The second injection component 22 moves the molten resin supplied to the internal space of the injection cylinder 20 as it moves forward and backward.

[0047] The second injection member driving unit 25 closes the base end of the injection cylinder 20 and holds the base end of the second injection member 22. Similar to the first injection member driving unit 15, the second injection member driving unit 25 also includes an advance / retract motor 26, an encoder 27, and a pressure detector 28.

[0048] The advance / retract motor 26 advances / retracts the second injection component 22 along the axis of the injection cylinder 20. A motion conversion mechanism is provided between the second injection component 22 and the advance / retract motor 26 to convert the rotational motion of the advance / retract motor 26 into the linear motion of the second injection component 22. The motion conversion mechanism can be, for example, a ball screw.

[0049] The encoder 27 detects the rotation of the forward / retract motor 26 and sends the detection signal to the control unit 80. The control unit 80 calculates the position and moving speed of the second injection member 22 based on the detection signal of the encoder 27 and controls the operation of the second injection member 22 using the calculation results.

[0050] The pressure detection unit 28 is provided on the transmission path between the advance / retract motor 26 and the second injection component 22, detects the force transmitted between the advance / retract motor 26 and the second injection component 22, and sends the detection signal thereof to the control unit 80. The control unit 80 calculates the pressure of the second injection component 22 based on the detected force, and adjusts or monitors the pressure (back pressure relative to the second injection component 22) received by the second injection component 22 from the molten resin, the pressure applied to the molten resin from the second injection component 22, and the like.

[0051] The supply connector 30 connects the molten resin supply path 7 (reference Figure 1 ) is connected to the discharge valve 70. The supply connector 30 allows the molten resin supplied from the molten resin supply device 6 to flow into the discharge valve 70.

[0052] The connection portion 35 is a pipe provided between the switching valve 50 and the discharge valve 70 , and allows the molten resin to flow through an internal flow path.

[0053] The nozzle 40 is provided on the reversing valve 50 at a position on the opposite side of the injection cylinder 20 and is formed as a cylindrical body connected to a flow path (such as a runner) of the mold device. The nozzle 40 allows the molten resin extruded from the injection cylinder 20 through the reversing valve 50 to flow and be injected into the mold device. The mold device molds a molded product by solidifying the molten resin filled into the cavity space from the nozzle 40.

[0054] The switching valve 50 is provided between the connection part 35, the injection cylinder 20 and the nozzle 40 to switch the flow of the molten resin. The switching valve 50 includes a valve body 51, a valve core 52 and a valve core driving part (not shown).

[0055] The valve body 51 is formed into a substantially rectangular parallelepiped and accommodates a valve core 52. The valve body 51 has a supply-side connection port 53 communicating with the flow path of the connection portion 35, an injection cylinder connection port 54 communicating with the internal space of the injection cylinder 20, and a nozzle connection port 55 communicating with the inside of the nozzle 40. The injection cylinder connection port 54 and the nozzle connection port 55 are provided, for example, on surfaces on opposite sides of the rotation center line of the valve core 52. The supply-side connection port 53 is provided, for example, on a surface in a direction orthogonal to the axis connecting the injection cylinder connection port 54 and the nozzle connection port 55.

[0056] The reversing valve 50 is switched between the first state and the second state by the rotation of the valve core 52 inside the valve body 51. In the first state, the valve core 52 connects the supply side connection port 53 and the injection cylinder connection port 54, and closes the nozzle connection port 55. In the second state, the valve core 52 connects the injection cylinder connection port 54 and the nozzle connection port 55, and closes the supply side connection port 53 (see also Figure 4 (B)). Thus, in the first state, the molten resin can be moved from the connection portion 35 toward the injection cylinder 20. In the second state, the molten resin can be moved from the injection cylinder 20 toward the nozzle 40.

[0057] The valve core driving unit switches the first state and the second state by rotating the valve core 52 in the valve body 51. In addition, the state of the valve core 52 is not limited to the first state and the second state. For example, the valve core 52 can be in a state where the supply side connection port 53, the injection cylinder connection port 54, and the nozzle connection port 55 are closed at the same time. In addition, the valve core 52 can be in a state where the supply side connection port 53 and the nozzle connection port 55 are connected and the injection cylinder connection port 54 is closed.

[0058] The discharge unit 60 is a connector provided on the discharge valve 70 and connected to a discharge path (not shown). The discharge unit 60 discharges the molten resin to the outside of the injection device 3 through the discharge path 61 in accordance with the switching of the discharge valve 70 .

[0059] The discharge valve 70 is provided between the molten resin supply path 7, the storage cylinder 10, the connection part 35 and the discharge part 60, and switches the flow of the molten resin. The discharge valve 70 includes a valve body 71, a valve element 72 and a valve element driving part (not shown).

[0060] The valve body 71 is formed into a substantially rectangular parallelepiped and accommodates a valve core 72. The valve body 71 has a supply-side connection port 73 communicating with the interior of the supply connector 30, a storage cylinder connection port 74 communicating with the internal space of the storage cylinder 10, a connection-side connection port 75 communicating with the flow path of the connection portion 35, and a discharge-side connection port 76 communicating with the interior of the discharge portion 60. For example, the storage cylinder connection port 74 and the discharge-side connection port 76 are provided on surfaces on the opposite sides of the rotation center line of the valve core 72. Furthermore, the supply-side connection port 73 and the connection-side connection port 75 are provided on surfaces on the opposite sides of the rotation center line of the valve core 72, which are orthogonal to a virtual line connecting the storage cylinder connection port 74 and the discharge-side connection port 76.

[0061] The valve core 72 rotates inside the valve body 71 and switches between the first state and the second state. In the first state, the valve core 72 communicates with the supply side connection port 73, the storage cylinder connection port 74, and the connection part side connection port 75, and closes the discharge side connection port 76. In the second state, the valve core 72 communicates with the supply side connection port 73, the storage cylinder connection port 74, and the discharge side connection port 76, and closes the connection part side connection port 75 (see also Figure 5 ).

[0062] The valve core driving unit switches the first state and the second state by rotating the valve core 72 in the valve body 71. In addition, the state of the valve core 72 is not limited to the first state and the second state. For example, the valve core 72 can be in a state where the supply side connection port 73, the connection part side connection port 75 and the discharge side connection port 76 are connected, and the storage cylinder connection port 74 is closed. In addition, the valve core 72 can be in a state where the storage cylinder connection port 74, the connection part side connection port 75 and the discharge side connection port 76 are connected, and the supply side connection port 73 is closed.

[0063] The functions of the control unit 80 can be implemented by any hardware, software or a combination thereof. For example, the control unit 80 can be applied to a computer having a processor, memory, input / output interface and communication interface not shown in the figure. The processor is a processor that combines one or more of a CPU (central processing unit), a GPU (graphics processing unit), an ASIC (application-specific integrated circuit), an FPGA (field programmable gate array), a circuit composed of multiple discrete semiconductors, etc., and executes a program stored in the memory. The memory includes a main storage device composed of a semiconductor memory, etc., and an auxiliary storage device composed of a disk or a semiconductor memory (flash memory), etc.

[0064] The control unit 80 controls the operation of each structure of the injection device 3 (the first injection component driving unit 15, the second injection component driving unit 25, the switching valve 50, the discharge valve 70, etc.) according to various instructions of the controller 4 that controls the entire injection molding machine system S. In addition, the injection molding machine system S may be configured such that the controller 4 also serves as the control unit 80 of the injection device 3 (that is, directly controls the injection device 3).

[0065] The control unit 80 constructs a first injection component control unit 81, a second injection component control unit 82, and a flow path switching processing unit 83 therein by the processor reading and executing the program in the memory. The first injection component control unit 81 controls the operation of the first injection component 12. The second injection component control unit 82 controls the operation of the second injection component 22. The flow path switching processing unit 83 switches the flow direction of the molten resin by controlling the states of the reversing valve 50 and the discharge valve 70.

[0066] <Operation of the injection device 3>

[0067] Next, use Figure 3 The operation of the injection device 3 of the injection molding machine 1 will be described. Figure 3 1 is a flowchart showing the operation of the injection device 3 in the injection molding machine 1. The injection device 3 performs the following operations in sequence under the control of the control unit 80: Figure 3 The metering step (step S101), the filling step (step S102) and the pressure holding step (step S103) shown are performed and these steps are repeated.

[0068] In the metering process, the injection device 3 accumulates a specified amount of molten resin at the front end side of the internal space of the injection cylinder 20 (in front of the second injection part 22). In the filling process, the injection device 3 fills the molten resin accumulated in the metering process into the cavity space of the mold device through the nozzle 40 by advancing the second injection part 22 of the injection cylinder 20. In the pressure holding process, the injection device 3 extrude the molten resin remaining in the injection cylinder 20 toward the mold device while maintaining the pressure of the molten resin in front of the second injection part 22 (holding pressure) at a set pressure. In addition, the injection molding machine 1 starts a cooling process after the pressure holding process to solidify the molten resin in the cavity space. In order to shorten the molding cycle time, the injection molding machine 1 can perform a metering process in the cooling process.

[0069] Next, refer to Figure 4 The specific actions in each process are described. Figure 4 (A) is a cross-sectional view showing the operation of the injection device 3 in the metering process. Figure 4 (B) is a diagram showing the operation of the injection process of the injection device 3.

[0070] When the metering process (step S101) is started, the flow path switching processing unit 83 of the control unit 80 controls the valve core driving unit of the switching valve 50 so that the valve core 52 is in the first state. That is, the flow path of the connection part 35 and the internal space of the injection cylinder 20 are in communication via the switching valve 50, and the molten resin can flow from the connection part 35 to the injection cylinder 20. In addition, the flow path switching processing unit 83 of the control unit 80 controls the valve core driving unit of the discharge valve 70 so that the valve core 72 is in the first state. That is, the internal space of the storage cylinder 10, the interior of the supply connector 30, and the flow path of the connection part 35 are in communication via the discharge valve 70, and the molten resin can flow from the storage cylinder 10 to the connection part 35.

[0071] Furthermore, in the metering process, the first injection component control unit 81 of the control unit 80 drives the advance / retract motor 16 to advance the first injection component 12. At this time, the first injection component control unit 81 calculates the position or moving speed of the first injection component 12 based on the detection value of the encoder 17, and controls the moving speed of the first injection component 12. The first injection component 12 discharges the molten resin accumulated in front of the first injection component 12 in the internal space of the storage cylinder 10 from the front end of the storage cylinder 10. The molten resin in the storage cylinder 10 moves to the connection part 35 via the discharge valve 70. At this time, the supply connector 30 side of the discharge valve 70 prevents the molten resin from flowing back in the molten resin supply path 7 by closing the control valve 8. Therefore, the molten resin in the storage cylinder 10 moves smoothly to the connection part 35 side. The molten resin extruded from the storage cylinder 10 flows into the internal space from the front end of the injection cylinder 20 via the connection part 35 and the reversing valve 50.

[0072] Furthermore, in the injection device 3 according to the first embodiment, in the metering process, the second injection unit control unit 82 of the control unit 80 drives the advance / retract motor 26 to retract the second injection unit 22. That is, when the molten resin extruded from the storage cylinder 10 flows into the injection cylinder 20, the second injection unit 22 actively retracts in the injection cylinder 20 without depending on the molten resin. Thus, compared with the case where the molten resin supplied to the injection cylinder 20 pushes the second injection unit 22 to retract the second injection unit 22, the pressure of the molten resin in the injection cylinder 20 can be greatly reduced.

[0073] The second injection component control unit 82 of the control unit 80 calculates the position of the second injection component 22 based on the detection value of the encoder 27 when the second injection component 22 is retreating, and retreats the second injection component 22 while suppressing a sharp retreat through the advance and retreat motor 26. In this way, an appropriate pressure is applied to the molten resin supplied to the injection cylinder 20, and the internal space of the injection cylinder 20 can be prevented from becoming negative pressure. In addition, the injection device 3 can monitor the pressure of the molten resin through a pressure detection unit 28 such as a force sensor instead of the detection of the encoder 27 (or in combination with the detection of the encoder 27), and control the pressure so that it does not drop excessively. At this time, it is also possible to prevent the internal space of the injection cylinder 20 from becoming negative pressure.

[0074] After the above-mentioned metering process, the control unit 80 starts the filling process (step S102). Figure 4 As shown in (B), the flow path switching processing unit 83 of the control unit 80 controls the valve core driving unit of the switching valve 50 to make the valve core 52 enter the second state. That is, the internal space of the injection cylinder 20 and the flow path of the nozzle 40 are connected through the switching valve 50, and the flow path of the connecting part 35 is blocked.

[0075] Furthermore, in the filling process, the second injection component control unit 82 of the control unit 80 drives the advance / retract motor 26 to advance the second injection component 22 to a predetermined position. At this time, the second injection component control unit 82 calculates the position or moving speed of the second injection component 22 based on the detection value of the encoder 27, and controls the moving speed of the second injection component 22. The second injection component 22 discharges the molten resin accumulated in front of the second injection component 22 in the internal space of the injection cylinder 20 from the front end of the injection cylinder 20. The molten resin of the injection cylinder 20 moves to the nozzle 40 via the reversing valve 50, flows in the flow path of the nozzle 40, and is filled into the cavity space of the mold device.

[0076] Furthermore, the injection device 3 according to the embodiment is configured such that, in the filling process of injecting molten resin into the mold device by the injection cylinder 20, a process of supplying molten resin to the internal space of the storage cylinder 10 (a storage process in the storage cylinder) is performed. Therefore, the flow path switching processing unit 83 of the control unit 80 maintains the valve core 72 of the discharge valve 70 in the first state. Thus, in the storage process in the storage cylinder, the molten resin pressure-fed from the molten resin supply device 6 through the molten resin supply path 7 flows from the front end of the storage cylinder 10 into the internal space via the supply connector 30 and the discharge valve 70. In the reversing valve 50, the connection portion 35 is closed by the valve core 52, so that the molten resin supplied from the molten resin supply device 6 when the control valve 8 is opened does not flow toward the connection portion 35, but flows smoothly into the storage cylinder 10.

[0077] The first injection component 12 of the storage cylinder 10 is pushed by the supplied molten resin and relatively retreats with respect to the storage cylinder 10. Alternatively, the first injection component control unit 81 of the control unit 80 may control the advance / retract motor 16 according to the pressure of the molten resin pressure-fed from the molten resin supply device 6 during the storage process of the storage cylinder so as to retreat the first injection component 12. For example, the first injection component control unit 81 may adjust the retreat speed of the first injection component 12 so that the pressure of the molten resin detected by the pressure detection unit 18 is consistent with the target pressure.

[0078] After the above-mentioned filling process, the control unit 80 starts the pressure holding process (step S103). At this time, the second injection unit control unit 82 of the control unit 80 controls the rotation of the advance / retract motor 26 and advances the second injection unit 22 according to the detection value of the pressure detection unit 28, so as to maintain the pressure (maintaining pressure) of the molten resin extruded by the second injection unit 22 at the set pressure. By advancing the second injection unit 22, the second injection unit 22 can extrude the molten resin remaining in the internal space of the injection cylinder 20 toward the mold device. In addition, during the pressure holding process, the control unit 80 can also continue the above-mentioned reservoir storage process.

[0079] As described above, the injection molding machine 1 can repeatedly manufacture molded products by linking the mold clamping device 2, the ejection device, and the moving device while performing the metering process, the filling process, and the pressure holding process in the injection device 3. In addition, the control unit 80 of the injection device 3 can determine whether the storage cylinder 10 can receive the molten resin, and control the discharge of the molten resin when it cannot receive the molten resin. Figure 5 It is a cross-sectional view showing the operation of discharging molten resin in the injection device 3 .

[0080] When discharging the molten resin, the flow path switching processing unit 83 of the control unit 80 controls the valve core driving unit of the discharge valve 70 so that the valve core 72 is in the second state. That is, the internal space of the storage cylinder 10, the interior of the supply connector 30, and the interior of the discharge unit 60 are in a state of communication via the discharge valve 70, and the molten resin can be discharged through the discharge unit 60. For example, in the reservoir storage process, in a state where a set volume of molten resin is supplied to the internal space of the storage cylinder 10, the molten resin supplied from the molten resin supply device 6 will not flow toward the storage cylinder 10. Therefore, the molten resin is discharged from the discharge unit 60 and the discharge path 61 to the outside of the injection device 3. As a result, it is possible to suppress the occurrence of molten resin blockage in the storage cylinder 10 or the discharge valve 70.

[0081] Next, refer to Figure 6 (A) and Figure 6 (B) will explain the significance of the operation of retracting the second injection member 22 in the metering step of supplying molten resin to the injection cylinder 20 . Figure 6(A) is a timing chart showing the operation of each injection component in the metering process of the injection device 3 according to the first embodiment. Figure 6 (B) is a timing chart showing the operation of each plunger in the metering process of the injection device according to the reference example.

[0082] First, the injection device involved in the reference example is described. Figure 6 As shown in (B), the injection device involved in the reference example advances the first plunger from the retracted position toward the forward position (discharge valve) at the time t1 when the metering process starts. As a result, the molten resin in the storage cylinder is squeezed out by the first plunger to be supplied to the connected injection cylinder. The second plunger located in the forward position in the internal space of the injection cylinder is subjected to the pressure of the molten resin supplied from the storage cylinder. Moreover, at the time t2 when the pressure of the molten resin reaches a predetermined pressure or more, the second plunger starts to retreat from the forward position.

[0083] That is, the second plunger receives the pressure of the first plunger extruding the molten resin, and thus retreats in the internal space of the injection cylinder. Therefore, the pressure applied to the first plunger by the advance and retreat motor of the first plunger rises sharply from time t1 to time t2, and becomes gentle from time t2 when the second plunger retreats. However, at time t2, the pressure of the first plunger extrude the molten resin at a very high pressure value (for example, 30MPa to 40MPa). This is because, in addition to the force for extruding the molten resin, a force is also required to retreat the second plunger.

[0084] The high pressure applied to the first plunger continues until the time t3 when the second plunger reaches the retracted position, during which the first plunger continues to be subjected to the high pressure. As a result, the first plunger is subjected to the high pressure for a long time throughout the metering process. As a result, the injection device involved in the reference example is prone to the following undesirable conditions: damage to the first plunger, the need to apply a large amount of energy to drive the first plunger, etc.

[0085] On the other hand, Figure 6 As shown in (A), similarly to the injection molding machine of the reference example, the injection molding machine 1 of the first embodiment moves the first injection component 12 from the retracted position to the advanced position at the time t1 when the metering process is started. As a result, the molten resin in the storage cylinder 10 is squeezed out by the first injection component 12 and supplied to the connected injection cylinder 20.

[0086] However, the injection molding machine 1 operates the advance / retract motor 26 at time t1 (simultaneously with the start of the advance of the first injection component 12) so as to retract the second injection component 22 from the advance position toward the retracted position. In other words, the second injection component 22 is retracted in correspondence with the advance of the first injection component 12 before the second injection component 22 starts to retract due to the pressure of the molten resin supplied from the storage cylinder 10. Thus, the injection molding machine 1 is capable of suppressing the increase in the pressure of the molten resin caused by the stop of the second injection component 22 until the second injection component 22 starts to retract relative to the molten resin supplied to the injection cylinder 20 due to the pressure of the molten resin. For example, the pressure applied to the first injection component 12 by the molten resin from the injection cylinder 20 to the storage cylinder 10 increases slightly until time t2, but its magnitude is about 10 MPa. In this metering process, this pressure (about 10 MPa) continues until time t3, and the load applied to the first injection component 12 in the entire metering process is reduced. In addition, the injection molding machine 1 may start the retreat of the second injection component 22 after the pressure of the molten resin in the injection cylinder 20 increases slightly as the first injection component 12 advances.

[0087] As a result, the injection molding machine 1 can suppress the reduction of durability due to damage or the like in the first injection part 12 and the storage cylinder 10. In addition, the injection molding machine 1 can promote the weight reduction and cost reduction of the first injection part 12 itself or its related components by reducing the force of the first injection part 12. In particular, when the recycled resin is used as the molten resin, in order to suppress the deterioration of the molten resin, a device is used to supply the molten resin from the front end of the storage cylinder 10 to the internal space and extrude it from the front end. When the molten resin is supplied from the front end of the storage cylinder 10 and the molten resin is extruded from the front end, a part of the path for supplying the molten resin overlaps a part of the path for extruding the molten resin inside the discharge valve 70. The path for supplying the molten resin (molten resin supply path 7, supply side connection port 73) has a high pressure due to the presence of the supplied molten resin, and most of the molten resin flows to the path for extruding the molten resin (connection part 35, connection part side connection port 75). However, when the pressure on the downstream side of the extrusion path is high, the molten resin of the storage cylinder 10 may flow back to the molten resin supply path 7, which may become a problem. However, as described above, the pressure of the molten resin on the downstream side decreases due to the retreat of the injection cylinder 20, so that the molten resin flows into the injection cylinder 20 more easily than flowing back to the molten resin supply path 7. Therefore, the injection molding machine 1 can control the flow of the molten resin without providing the discharge valve 70, for example.

[0088] Furthermore, in the metering process, the control unit 80 starts the retreat of the second injection unit 22 in correspondence with the start of the advancement of the first injection unit 12. In addition, depending on the difference in the pressure of the resin existing on the path where the molten resin is supplied from the front end of the storage cylinder 10 to the internal space of the injection cylinder 20, the retreat of the second injection unit 22 may be started before the first injection unit 12 advances. At this time, in order to suppress the temperature drop of the molten resin and the mixing of bubbles into the molten resin accompanying the pressure drop, it is necessary to study the structure and control. Since the injection molding machine 1 can easily maintain the pressure of the molten resin stably at a positive pressure, it is preferable to control (or include such setting) so that the retreat of the second injection unit 22 starts after the advancement of the first injection unit 12. Alternatively, in the case where the second injection unit 22 is retreated before the first injection unit 12 advances, the injection molding machine 1 can monitor the pressure of the molten resin through the detection of the pressure detection unit 28 such as a load cell, and control so that the pressure does not drop excessively. As a result, the second injection unit 22 can be smoothly retreated while accurately maintaining the pressure (positive pressure) of the internal space of the injection cylinder 20.

[0089] Furthermore, the control unit 80 preferably sets the retreat speed of the second injection component 22 to be lower than the forward speed of the first injection component 12 in the metering process. That is, the control unit 80 retreats the second injection component 22 in a manner that matches the theoretical supply amount of the molten resin supplied to the injection cylinder 20. For example, the control unit 80 controls the forward speed of the first injection component 12 and the retreat speed of the second injection component 22 to be the same speed. In this way, it is possible to suppress a significant increase in the pressure of the molten resin while maintaining the pressure of the molten resin flowing into the internal space of the injection cylinder 20 at a positive pressure. Furthermore, for example, the control unit 80 makes the retreat speed of the second injection component 22 a speed that is slightly slower than the forward speed of the first injection component 12, thereby reliably preventing the second injection component 22 from retreating faster than the inflow of the molten resin. At this time, since the interval between the first injection component 12 and the second injection component 22 is relatively narrowed, the speed of the second injection component 22 may temporarily exceed the speed of the first injection component 12. Therefore, the average speed of the second injection component 22 or the integrated value after the second injection component 22 starts to move is preferably controlled to be smaller than the average speed or integrated value of the first injection component 12. The control unit 80 can control the speeds of the first injection component 12 and the second injection component 22 using information related to the relative positional relationship between the first injection component 12 and the second injection component 22, such as the speed, acceleration or position.

[0090] Alternatively, the control unit 80 may control the retreat speed of the second injection unit 22 while monitoring the pressure of the first injection unit 12 by the pressure detection unit 18. In this case, the pressure of the first injection unit 12 pressing the molten resin can also be reduced. Furthermore, the control unit 80 may control the retreat speed of the second injection unit 22 while monitoring the pressure of the second injection unit 22 by the pressure detection unit 28. Thus, the pressure of the injection cylinder 20 can be controlled not to drop excessively, and negative pressure of the injection cylinder 20 can be prevented.

[0091] Furthermore, the control unit 80 stops the retreat of the second injection unit 22 as the forward movement of the first injection unit 12 stops during the metering process. For example, the retreat of the second injection unit 22 is stopped at the same time as the forward movement of the first injection unit 12 stops, or at a time slightly later than the forward movement of the first injection unit 12 stops. This makes it easy to avoid the internal space of the injection cylinder 20 from becoming negative pressure.

[0092] In addition, the timing of retracting the second injection component 22 may not be the same as the timing of the start of the advancement of the first injection component 12, but may be a timing that is later than the timing t1. In other words, the retraction of the second injection component 22 is set to be after the start of the advancement of the first injection component 12. For example, the control unit 80 may perform the following control: the retraction of the second injection component 22 begins after a predetermined period has passed relative to the timing t1 at which the first injection component 12 starts to advance. Alternatively, the control unit 80 may monitor the pressure applied to the second injection component 22 by the pressure detection unit 28, and retract the second injection component 22 at the timing when the pressure of the second injection component 22 begins to rise. As a result, the injection device 3 can more stably prevent the internal pressure of the injection cylinder 20 from becoming a negative pressure, and can prevent the temperature drop of the molten resin and the mixing of bubbles caused by the negative pressure.

[0093] <Structure and Operation of Injection Device 3A According to Second Embodiment>

[0094] Figure 7 1 is a cross-sectional view schematically showing an injection device 3A of an injection molding machine 1A according to a second embodiment. The injection molding machine 1A according to the second embodiment is different from the injection molding machine 1 according to the first embodiment in that a screw is applied to the storage cylinder 10 as the first injection component 13, and molten resin is supplied to the internal space of the storage cylinder 10 from a position further back than the front end of the first injection component 13. In addition, since the structures of the injection cylinder 20, the nozzle 40 and the reversing valve 50 of the injection device 3A are the same as those of the injection device 3 according to the first embodiment, their detailed description is omitted.

[0095] The storage cylinder 10 has a hole 10h at the base end for introducing molten resin into the internal space. A supply connector 30 connected to the molten resin supply path 7 is provided in the hole 10h. A heating device (not shown) for keeping or heating the molten resin supplied to the internal space may be provided on the wall of the cylinder 10.

[0096] The first injection component 13 is configured to be rotatable around the axis in the storage cylinder 10 by a rotary motor 19 provided in the first injection component driving unit 15. A spiral scraper 131 is protrudingly formed on the outer peripheral surface of the first injection component 13. A screw head 132, a backflow prevention ring 133, a sealing ring 134, etc. are provided at the front end of the first injection component 13. The first injection component 13 rotates around the axis in the storage cylinder 10, thereby kneading the molten resin supplied from the hole 10h while moving it to the front, and the molten resin can be supplied to the internal space further forward than the screw head 132.

[0097] Furthermore, a connection portion 36 is provided at the front end of the storage cylinder 10 in place of the discharge valve 70, which connects the storage cylinder 10 and the switching valve 50 without switching the flow path. The connection portion 36 has a flow path inside that communicates with the supply-side connection port 53 of the switching valve 50. Thus, the injection device 3 can supply molten resin to the injection cylinder 20 via the connection portion 36 and the switching valve 50.

[0098] The control unit 80 blocks the supply side connection port 53 by the valve core 52 of the reversing valve 50 in the reservoir storage process, thereby accumulating the molten resin on the front end side of the storage cylinder 10. In addition, in the metering process of the injection cylinder 20, the control unit 80 controls the advance / retract motor 16 to advance the first injection component 13, thereby discharging the molten resin from the storage cylinder 10. At this time, similarly to the first embodiment, the control unit 80 controls the advance / retract motor 26 to retreat the second injection component 22 of the injection cylinder 20 in accordance with the advance of the first injection component 13, thereby smoothly supplying the molten resin while suppressing the pressure applied to the first injection component 13.

[0099] Furthermore, in the injection process (filling process, pressure holding process) after the metering process, the control unit 80 discharges the molten resin from the front end of the injection cylinder 20 by advancing the second injection member 22 to fill the cavity space of the mold device with the molten resin.

[0100] Therefore, in the injection molding machine 1A according to the second embodiment, the pressure applied to the first injection part 13 during the extrusion of the molten resin can also be reduced. As a result, the injection molding machine 1A can improve the durability of the first injection part 13 and the storage cylinder 10, and can reduce the energy required for the first injection part 13 to extrude the molten resin.

[0101] In addition, the injection device 3A according to the second embodiment can supply a solid (for example, granulated) molding material as the molding material supplied to the storage cylinder 10, and form a molten resin in the storage cylinder 10 by heating the storage cylinder 10. In addition, the injection molding machine 1A can be configured so that the molten resin is pressed from the molten resin supply device 6 to the injection device 3, thereby moving the molten resin in the storage cylinder 10 by the pressure. In this case, the first injection part 13 can be configured not to have a scraper.

[0102] As described above, in the injection molding machine 1A according to the second embodiment in which the storage cylinder 10 is provided with the first injection member 13 as a screw, the same control as that of the injection molding machine 1 according to the first embodiment can be performed. In particular, the injection device 3A is configured to supply molten resin from the base end of the storage cylinder 10 to the internal space and to extrude the molten resin from the front end of the storage cylinder 10. Thus, the injection device 3A can omit the configuration of the discharge valve 70 for switching the flow path, and can smoothly extrude the molten resin from the front end of the storage cylinder 10 to the injection cylinder 20 according to the advancement of the first injection member 13.

[0103] Furthermore, in the metering process, the control unit 80 does not rely on the pressure of the molten resin supplied from the storage cylinder 10, but moves the second injection component 22 backward in accordance with the advancement of the first injection component 13, thereby suppressing the increase in the molten resin pressure caused by the stop of the second injection component 22. As a result, the injection molding machine 1A can suppress the reduction in durability caused by damage to the first injection component 13 and the storage cylinder 10. In addition, the injection molding machine 1A can promote the weight reduction and cost reduction of the first injection component 13 itself or its related components (screw head 132, backflow prevention ring 133, seal ring 134) by reducing the force of the first injection component 13.

[0104] Furthermore, in the injection device 3A, it is also preferable to control (or set) the second injection component 22 to start retreating after the first injection component 13 advances so as to stably maintain the pressure of the molten resin at a positive pressure. However, in the injection device 3A, the second injection component 22 may start retreating before the first injection component 13 advances, depending on the pressure of the resin existing in the path for supplying the molten resin from the front end of the storage cylinder 10 to the internal space of the injection cylinder 20.

[0105] The control unit 80 may control the movement of the first injection component 13 and the second injection component 22 in a manner that matches the theoretical supply amount of the molten resin supplied to the injection cylinder 20. For example, the control unit 80 controls the forward speed of the first injection component 13 and the retreat speed of the second injection component 22 to be the same speed. In this way, the pressure of the molten resin flowing into the internal space of the injection cylinder 20 can be maintained at a positive pressure while suppressing a significant increase in the pressure of the molten resin. In addition, the control unit 80 can reliably prevent the second injection component 22 from retreating faster than the inflow of the molten resin by making the retreat speed of the second injection component 22 slightly higher than the forward speed of the first injection component 13. In addition, the average speed of the second injection component 22 or the integrated value after the second injection component 22 starts to move is preferably controlled to be smaller than the average speed or integrated value of the first injection component 13. The control unit 80 can control the speed of the first injection component 13 and the second injection component 22 using information related to the relative positional relationship between the first injection component 13 and the second injection component 22, such as the speed, acceleration or position. Alternatively, the control unit 80 may control the retreat speed of the second injection unit 22 while monitoring the pressure of the second injection unit 22 by the pressure detection unit 28. This can control the pressure of the injection cylinder 20 not to drop excessively, and prevent negative pressure in the injection cylinder 20.

[0106] The injection molding machines 1 and 1A disclosed this time are only illustrative and not restrictive. The embodiments can be modified and improved in various ways without departing from the scope and purpose of the attached technical solutions. The matters recorded in the above-mentioned various embodiments can adopt other structures within the scope of non-contradiction, and can be combined within the scope of non-contradiction.

Claims

1. An injection molding machine comprising: The first cylinder is supplied with molding material; A first injection component is disposed in the first cylinder body so as to be able to move forward and backward; a second cylinder body to which the molding material extruded from the first cylinder body is supplied; a second injection component, which is disposed in the second cylinder body so as to be able to move forward and backward; and a control unit for controlling the actions of the first injection unit and the second injection unit, The control unit controls a metering step of supplying the molding material to the second cylinder as the first injection component advances, and in the metering step, the second injection component is retracted in accordance with the advancement of the first injection component.

2. The injection molding machine according to claim 1, wherein: The control unit starts retracting the second injection member after starting advancing the first injection member in the metering step.

3. The injection molding machine according to claim 1, wherein: The control unit stops the retreat of the second injection member as the advancement of the first injection member stops in the metering step.

4. The injection molding machine according to claim 1, wherein: The control unit sets a retreat speed of the second injection member to be less than or equal to a forward speed of the first injection member in the metering step.

5. The injection molding machine according to any one of claims 1 to 4, wherein: The first cylinder body supplies the molding material to the inner space of the first cylinder body from the front of the first cylinder body to accumulate the molding material in front of the first injection component, and discharges the molding material from the front of the first cylinder body as the first injection component moves forward. The second cylinder supplies the molding material from the front of the second cylinder to the inner space of the second cylinder to store the molding material in front of the second injection part, and discharges the molding material from the front of the second cylinder as the second injection part moves forward.

6. The injection molding machine according to claim 5, wherein: The first injection member is a plunger that slides relatively with respect to the first cylinder to squeeze out the molding material accumulated in front.

7. The injection molding machine according to any one of claims 1 to 4, wherein: The first cylinder body supplies the molding material to the inner space of the first cylinder body from a position further rearward than the front end of the first injection component, accumulates the molding material in front of the first injection component, and discharges the molding material from the front of the first cylinder body as the first injection component moves forward. The second cylinder supplies the molding material from the front of the second cylinder to the inner space of the second cylinder to store the molding material in front of the second injection part, and discharges the molding material from the front of the second cylinder as the second injection part moves forward.

8. The injection molding machine according to claim 7, wherein: The first injection component is a screw having a spiral scraper on its outer peripheral surface and relatively rotating in the internal space of the first cylinder, and the molding material is accumulated in front of the first injection component by the rotation.

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