extruder

Abstract

An extruder according to an embodiment includes a first control valve connected to a decompression path connecting a ventilation tank provided in a cylinder to a decompression pump, the first control valve being configured to operate based on a first control signal; a second control valve for atmospheric release connected to the decompression path, the second control valve being configured to operate based on a second control signal; a pressure sensor configured to detect a pressure in the decompression path; and a controller configured to output the first control signal and the second control signal based on the pressure detected by the pressure sensor, and to perform feedback control of the opening degree of the respective first control valve and second control valve.

Description

Background Technology

[0001] This disclosure pertains to extruders.

[0002] As disclosed in Patent Document 1, the inventors developed an automatic control method that is executed when the extruder is started.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2023-065731 Summary of the Invention

[0004] The inventors encountered various problems while developing the extruder.

[0005] For example, when the extruder is started, after the barrel (cylinder) is filled with molten resin, the pressure inside the vent box is reduced. At this time, to prevent vent-up (resin buildup) from the molten resin rising into the vent box, the operator manually operates the valves while visually inspecting the state of the molten resin in the vent box. In other words, the valve opening cannot be automatically controlled when the pressure inside the vent box is reduced.

[0006] Other issues and novel features will become apparent from the description in this specification and the accompanying drawings.

[0007] An extruder according to one embodiment includes: a first control valve connected to a pressure reduction path of a pressure reducing pump via a ventilation box disposed in a barrel, the first control valve being configured to operate based on a first control signal; a second control valve for atmospheric release connected to the pressure reduction path, the second control valve being configured to operate based on a second control signal; a pressure sensor configured to detect pressure in the pressure reduction path; and a controller configured to output the first control signal and the second control signal based on the pressure detected by the pressure sensor, and to perform feedback control on the opening degree of the respective first control valve and the second control valve.

[0008] According to this embodiment, an extruder can be provided that can automatically control the valve opening while reducing the number of times material overflow occurs.

[0009] The above and other objects, features and advantages of this disclosure will become more fully understood from the detailed description and accompanying drawings given below. Attached Figure Description

[0010] Figure 1 This is a schematic cross-sectional view showing the overall structure of the extrusion molding apparatus using an extruder according to the first embodiment;

[0011] Figure 2 This is a block diagram illustrating details of the pressure reduction control in the ventilation box V2 of the extruder according to the first embodiment;

[0012] Figure 3 This is a block diagram showing the details of the pressure reduction control in the ventilation box V2 of the extruder according to the modified example 1 of the first embodiment;

[0013] Figure 4 This is a block diagram showing the details of the pressure reduction control in the ventilation box V2 of the extruder according to Modified Example 2 of the first embodiment;

[0014] Figure 5 This is a block diagram illustrating details of the pressure reduction control in the ventilation box V2 of the extruder according to the second embodiment; and

[0015] Figure 6 This is a block diagram illustrating the details of the decompression control in the ventilation box V2 of the extruder according to the third embodiment. Detailed Implementation

[0016] Specific embodiments will be described in detail below with reference to the accompanying drawings. However, this disclosure is not limited to the following embodiments. Furthermore, for clarity, the following description and drawings have been appropriately simplified.

[0017] (First Implementation)

[0018] <Overall Structure of Extrusion Molding Equipment>

[0019] First, refer to Figure 1 The overall structure of the extrusion molding apparatus using an extruder according to the first embodiment will be described. Figure 1 This is a schematic cross-sectional view showing the overall structure of an extrusion molding apparatus using an extruder according to a first embodiment. By using the extrusion molding apparatus according to this embodiment, a resin compound in which filler is dispersed in a resin is extruded, for example. The shape of the resin compound extruded by the extrusion molding apparatus according to this embodiment is, for example, a strip shape. However, it is not limited to a specific shape; for example, it can be a film shape instead.

[0020] like Figure 1 As shown, the extrusion molding apparatus according to the first embodiment includes a resin feeder F1, a filler feeder F2, an extruder 10, and a hard die 20.

[0021] Notice, Figure 1 The right-handed XYZ orthogonal coordinates shown in the other figures are merely for the convenience of explaining the positional relationships between components. Generally, the positive Z-axis is vertically upward, and the XY plane is a horizontal plane; this direction and plane are the same in all figures.

[0022] The resin feeder F1 is a feeder used to supply resin raw materials into the cylinder 11 of the extruder 10. The resin raw materials are the main raw materials for resin compounds. Figure 1 The resin feeder F1 shown is a screw-type feeder and includes a feeder hopper FH1, a feeder screw FS1, and a feeder motor FM1.

[0023] Resin raw materials include, for example, resin granules made from polypropylene, polyethylene, polyamide, polyethylene terephthalate, etc. However, they are not limited to specific materials.

[0024] Resin raw material is fed into and stored in the feeder hopper FH1. When the feeder screw FS1 is driven to rotate by the feeder motor FM1, the resin raw material in the feeder hopper FH1 is supplied to the inside of the extruder 10 through the hopper 13. For example, the amount of resin raw material supplied from the resin raw material feeder F1 to the extruder 10 can be controlled by performing feedback control on the rotation of the feeder motor FM1 while measuring the change in the mass of the resin raw material in the feeder hopper FH1.

[0025] A controller (not shown) controls the amount of resin feedstock supplied from the resin feedstock feeder F1 to the extruder 10. Although Figure 1 The resin feeder F1 shown is a screw-type feeder, but as an alternative, a vibratory or other type of feeder can be used, in which the amount of resin raw material to be supplied can be controlled by a controller, i.e., a computer.

[0026] The filler feeder F2 is a feeder used to supply the fillers that constitute the resin compound into the cylinder 11 of the extruder 10. Figure 1 The packing feeder F2 shown is a screw-type feeder and includes a feeder hopper FH2, a feeder screw FS2, and a feeder motor FM2.

[0027] Fillers include, for example, talc, calcium carbonate powder, glass fiber, and carbon powder. However, they are not limited to specific materials.

[0028] The filler is fed into and stored in the feeder hopper FH2. When the feeder screw FS2 is driven to rotate by the feeder motor FM2, the filler in the feeder hopper FH2 is supplied to the inside of the extruder 11 through the side feed port 14 (side feed port) of the extruder 10. For example, the amount of filler supplied from the filler feeder F2 to the extruder 10 can be controlled by performing feedback control on the rotation of the feeder motor FM2 while measuring the change in the mass of the filler in the feeder hopper FH2.

[0029] A controller (not shown) controls the amount of packing supplied from the packing feeder F2 to the extruder 10. Although Figure 1The feeder F2 shown is a screw-type feeder, but as an alternative, a vibratory or other type of feeder can be used, in which the amount of packing to be supplied can be controlled by a controller, i.e., a computer.

[0030] Note that the side feeder (side feeder) can be positioned between the filler feeder F2 and the side feed port 14, and the filler sent from the filler feeder F2 can be fed into the side feed port 14 via the side feeder. Alternatively, the filler can be supplied from the filler feeder F2 through the hopper 13 of the extruder 10 instead of the side feed port 14 into the cylinder 11.

[0031] Extruder 10 is a screw extruder. Figure 1 In the extruder 10 shown, a screw 12 extending along the X-axis is housed within a barrel 11 extending along the X-axis. A hopper 13 for supplying resin raw material from the resin raw material feeder F1 into the barrel 11 is positioned above the upstream end (negative X-axis side) of the barrel 11 in the extrusion direction. A side feed port 14 for supplying filler from the filler feeder F2 is positioned on the side surface of the barrel 11 on the downstream side (positive X-axis side) of the hopper 13 in the extrusion direction, i.e., on the side of the die 20. In the following description, the upstream side in the extrusion direction within the barrel 11 is simply referred to as the "upstream side," and the downstream side in the extrusion direction is simply referred to as the "downstream side."

[0032] The screw motor SM is connected to the base of the screw 12 via a reduction gear RG. The screw motor SM is the drive source for driving the screw 12. For example, the rotational speed of the screw 12 can be controlled by controlling the rotational speed of the screw motor SM.

[0033] Note that the number of screws 12 can be one or more. For example, an extruder 10 that includes one screw 12 is called a "single-screw extruder", while an extruder 10 that includes two screws 12 is called a "twin-screw extruder".

[0034] The resin feedstock supplied from hopper 13 is conveyed from the base of screw 12, which is rotated by screw motor SM, to its front end, i.e., from the upstream side to the downstream side. Inside cylinder 11, the resin feedstock is heated, sheared by the rotating screw 12, and melted.

[0035] Note that, although not shown, a heater for heating the interior of cylinder 11 is provided on approximately the entire outer circumferential surface of cylinder 11 along its length.

[0036] Note that the shearing and melting of the resin raw material supplied from hopper 13 mainly occurs in... Figure 1 The kneading process is carried out in the kneading zone KZ1 of the extruder 10 shown.

[0037] Furthermore, a ventilation box V1 is disposed on the upper surface of the cylinder 11 on the downstream side near the kneading zone KZ1. For example, air and volatile components contained in the resin raw material are discharged through the ventilation box V1.

[0038] Downstream of the ventilation box V1, a side feed port 14 for supplying filler is provided on the side surface of the cylinder 11. The filler supplied from the side feed port 14 is conveyed downstream together with the molten resin raw material. The kneading zone KZ2 of the extruder 10 is provided downstream of the side feed port 14. In the kneading zone KZ2, the molten resin raw material and the filler are kneaded, and the filler is uniformly distributed in the molten resin raw material.

[0039] Note that the ventilation box V1 is not required.

[0040] Downstream of the kneading zone KZ2, a ventilation box V2 is disposed on the upper surface of the cylinder 11. The ventilation box V2 is depressurized by a vacuum pump VP via a control valve CV1. For example, air and volatile components contained in the resin raw material are further exhausted through the ventilation box V2.

[0041] Note that the pressure reduction control in the fume chamber V2 using control valve CV1 and vacuum pump VP will be described later.

[0042] like Figure 1 As shown, the rigid die 20 is attached to the front end (the end on the positive side of the x-axis) of the extruder 10. The resin raw material and filler kneaded in the extruder 10 are molded into a resin compound, for example, in the shape of a strip, through the rigid die 20. That is, the strip-shaped resin compound is produced by the extrusion molding equipment according to this embodiment.

[0043] Note that by cutting the strip-shaped resin compound, granules can be obtained to serve as raw materials for resin-molded products. Furthermore, a hard mold 20 is not necessary, and the resin raw material and filler can be extruded without molding.

[0044] <Details of decompression control in ventilation box V2>

[0045] Next, we will refer to Figure 2 Details of the pressure reduction control in the ventilation box V2 of the extruder according to the first embodiment are described. Figure 2 This is a block diagram illustrating details of the decompression control in the ventilation box V2 of the extruder according to the first embodiment. Figure 2 It also shows Figure 1 The diagram shows a cross-sectional view of the barrel 11 and screw 12 of the extruder 10.

[0046] like Figure 2 As shown, the extruder 10 according to this embodiment, except for Figure 1In addition to the ventilation box V2, vacuum pump VP, and control valve CV1 shown, it also includes control valve CV2, pressure sensor P1, and controller CTR.

[0047] Vacuum pump VP is connected to ventilation box V2 via control valve CV1, and reduces the pressure inside ventilation box V2. Vacuum pump VP is a type of pressure reducing pump.

[0048] like Figure 2 As shown, the control valve (first control valve) CV1 is a pressure-reducing valve installed in the pressure-reducing path of the ventilation box V2 connected to the vacuum pump VP, and is operated based on a control signal (first control signal) output from the controller CTR. More specifically, the control valve CV1 is driven, for example, by a motor (electric motor) such as a servo motor, or by air pressure, and its opening degree is controlled based on the control signal output from the controller CTR.

[0049] exist Figure 2 In the configuration shown, during the operation of the vacuum pump VP, the pressure in the fume box V2 is reduced by increasing the opening of the control valve CV1. That is, the pressure inside the fume box V2 is reduced.

[0050] In addition, the control valve CV1 is, for example, a ball valve that includes a V-port valve.

[0051] like Figure 2 As shown, control valve (second control valve) CV2 is a valve for atmospheric release connected to a pressure-reducing path. Similar to control valve CV1, control valve CV2 is operated based on a control signal (second control signal) output from controller CTR. More specifically, control valve CV2 is driven, for example, by a motor such as a servo motor, or by air pressure, and its opening degree is controlled based on the control signal output from controller CTR.

[0052] exist Figure 2 In the configuration shown, during the operation of the vacuum pump VP, the pressure in the fume box V2 is reduced by decreasing the opening degree of the control valve CV2 while the control valve CV1 is open. That is, the pressure inside the fume box V2 is reduced.

[0053] Furthermore, similar to control valve CV1, control valve V2 is, for example, a ball valve that includes a V-port valve.

[0054] like Figure 2 As shown, according to this embodiment, the pressure sensor (first pressure sensor) P1 is positioned closer to the ventilation box V2 than the control valve CV1, and detects the pressure in the ventilation box V2. Figure 2 As shown, pressure sensor P1 is connected to controller CTR via wired or wireless means, and the pressure detected by pressure sensor P1 is transmitted to controller CTR.

[0055] Figure 2 The pressure sensor P1 shown is positioned in the pressure reduction path between the ventilation box V2 and the control valve CV1. However, the pressure sensor P1 only needs to detect the pressure in the pressure reduction path, and alternatively, it could be positioned, for example, in the ventilation box V2.

[0056] The controller CTR outputs control signals to control valves CV1 and CV2 based on the pressure detected by pressure sensor P1, thereby controlling the opening degree of the respective control valves CV1 and CV2. For example, when the controller CTR starts the vacuum pump VP, it controls the opening degree of control valves CV1 and CV2 so that the pressure reduction (vacuum degree) detected by pressure sensor P1 becomes a predetermined pressure reduction degree. More preferably, as described later, the controller CTR controls the opening degree of control valves CV1 and CV2 to target a pressure reduction degree at a predetermined pressure reduction rate (time change rate of pressure reduction), at which no material overflow occurs.

[0057] also, Figure 2 The controller CTR shown also controls the operation of the vacuum pump VP. However, this disclosure is not specifically limited thereto.

[0058] Note that, although not shown, the controller CTR includes an arithmetic unit such as a central processing unit (CPU) and memory such as random access memory (RAM) and read-only memory (ROM), in which various types of programs and data are stored. In other words, the controller CTR functions as a computer and controls control valves CV1 and CV2 and the vacuum pump VP based on the aforementioned programs.

[0059] therefore, Figure 2 The controller CTR shown can be configured in hardware using the aforementioned CPU, memory, and other circuitry. Furthermore, the controller CTR can be implemented in software using a program stored in memory or the like. In other words, the controller CTR can be implemented in various forms using hardware, software, or a combination thereof.

[0060] Note that the controller CTR can... Figure 1 The entire extruder 10, or even the entire extrusion molding equipment, is controlled as shown.

[0061] Note that because the opening degree of a ball valve has a non-linear relationship with its flow rate, swaying may occur when the opening degree is controlled using PID control, which includes proportional control (P control), integral control (I control), and derivative control (D control). Therefore, when the control valves CV1 and CV2 are ball valves, it is preferable to use proportional-integral control (so-called PI control or IP control) that only includes P control and I control in the controller CTR, and particularly preferably, a two-degree-of-freedom proportional-integral control (IP control) is used.

[0062] Next, the operation of the pressure reduction control performed by the controller CTR will be described.

[0063] First, such as Figure 2 As shown, when the extruder 10 is started and a sufficient amount of resin raw material is fed into the barrel 11, the upstream and downstream sides of the ventilation box V2 are filled with molten resin due to the structure of the screw 12, thus maintaining the airtightness of the ventilation box V2.

[0064] Subsequently, the controller CTR starts the vacuum pump VP. At this time, the control valve CV1 for depressurization is closed, the control valve CV2 for atmospheric release is open, and the interior of the ventilation box V2 is at atmospheric pressure.

[0065] Next, the controller CTR gradually increases the opening of the closed control valve CV1, causing the pressure reduction rate detected by the pressure sensor P1 to become a predetermined pressure reduction rate. Note that the predetermined pressure reduction rate is the rate at which molten resin does not rise into the vent box V2 and overflow occurs. Overflow occurs when the pressure reduction rate is too high and the pressure in the vent box V2 drops sharply. Furthermore, the predetermined pressure reduction rate does not need to be constant and can be expressed by some function, etc.

[0066] More specifically, when the pressure in the ventilation box V2 drops sharply, the volatile components contained in the molten resin evaporate simultaneously near the ventilation box V2, and the molten resin foams and expands. Furthermore, when the expanded molten resin rises into the interior of the ventilation box V2, overflow occurs. Moreover, when the molten resin is drawn into the depressurization path, it adheres to the depressurization path.

[0067] To prevent overflow, the valve is manually operated by the operator while visually inspecting the state of the molten resin in the ventilation box V2.

[0068] Conversely, in the extruder 10 according to the first embodiment, the controller CTR controls the opening of the closed control valve CV1 to gradually increase it, so that the decompression rate of the pressure detected by the pressure sensor P1 becomes a predetermined decompression rate that prevents material overflow.

[0069] Note that the extruder 10 according to this embodiment includes a control valve CV2 for atmospheric release, and the control valve CV2 is opened when the opening of the control valve CV1 is gradually increased after the vacuum pump VP is started. Therefore, in the extruder 10 according to this embodiment, when the opening of the control valve CV1 is gradually increased, the decompression rate can be more easily controlled to a predetermined decompression rate that prevents material overflow compared to the case where the control valve CV2 is not set.

[0070] Then, after the controller CTR fully opens the control valve CV1, the controller CTR controls the opening of the open control valve CV2 to gradually reduce it, so that the pressure reduction rate detected by the pressure sensor P1 becomes the predetermined pressure reduction rate.

[0071] In this way, the opening degree of control valves CV1 and CV2 can be automatically controlled by the controller CTR, while reducing the number of times material overflow occurs.

[0072] Note that control valve CV1 can be an on / off valve that only controls its opening and closing. In this specification, it is assumed that when control valve CV1 is an on / off valve, the control of the opening of control valve CV1 performed by controller CTR includes both opening and closing control.

[0073] In this scenario, after starting the vacuum pump VP, the controller CTR opens the closed control valve CV1. Then, the controller CTR gradually decreases the opening of the open control valve CV2, causing the pressure reduction rate detected by the pressure sensor P1 to become a predetermined pressure reduction rate.

[0074] Furthermore, since atmospheric air passes through the control valve CV2 for atmospheric release, the selection of the control valve CV2 is less restrictive compared to the control valve CV1 for pressure reduction, which passes through the gaseous components in the molten resin. For example, as the control valve CV2, a shut-off valve or similar valve that can more easily control the flow rate than a ball valve can be selected, and its diameter can also be reduced. Therefore, when using the control valve CV2, the pressure reduction rate can be easily controlled to a predetermined pressure reduction rate that prevents material overflow.

[0075] <Modification Example 1 of the First Embodiment>

[0076] Next, we will refer to Figure 3 The extruder according to Modified Example 1 of the first embodiment will be described. Figure 3 This is a block diagram showing the details of the decompression control in the ventilation box V2 of the extruder according to the modified example 1 of the first embodiment. Figure 3 and Figure 2 Correspondingly.

[0077] exist Figure 2In the extruder shown, control valve CV2 is positioned closer to the ventilation box V2 compared to control valve CV1. Conversely, as Figure 3 As shown, control valve CV2 is positioned closer to vacuum pump VP than control valve CV1.

[0078] The decompression control operation performed by the controller CTR, and other configurations besides those described above. Figure 2 The operation and construction of the extruder 10 according to the first embodiment shown are similar, so its description is omitted.

[0079] <Modified Example 2 of the First Embodiment>

[0080] Next, we will refer to Figure 4 The extruder according to Modified Example 2 of the first embodiment will be described. Figure 4 This is a block diagram showing the details of the decompression control in the ventilation box V2 of the extruder according to Modified Example 2 of the first embodiment. Figure 4 and Figure 2 Correspondingly.

[0081] like Figure 4 As shown, with Figure 2 Compared to the extruder 10 shown, the extruder 10 according to Modified Example 2 further includes an extrusion sensor S for detecting extrusion.

[0082] like Figure 4 As shown, the molten resin overflow sensor S is positioned at a predetermined height above the inlet of the ventilation box V2 (the connection between the cylinder 11 and the ventilation box V2) and detects molten resin that has entered the ventilation box V2. The molten resin overflow sensor S is, for example, an object detection sensor, such as a non-contact proximity sensor or a contact limit switch. However, it is not limited to a specific sensor.

[0083] like Figure 4 As shown, the overflow sensor S is connected to the controller CTR via wired or wireless means, and the overflow detection signal from the overflow sensor S is transmitted to the controller CTR. Specifically, when the overflow sensor S detects overflow, the controller CTR closes the control valve CV1. At this time, the controller CTR can also fully open the control valve CV2 and stop the vacuum pump VP.

[0084] With the above construction, in the extruder 10 according to the modified example, the number of times molten resin is drawn into the decompression path when overflow has already occurred can be reduced.

[0085] Constructions other than those described above Figure 2 The extruder 10 shown according to the first embodiment has a similar construction, therefore its description will be omitted. Furthermore, Figure 4 The modified example 2 shown can be applied to Figure 3 The modified example shown is 1.

[0086] (Second Implementation)

[0087] Next, we will refer to Figure 5 An extruder according to the second embodiment will be described. Figure 5 This is a block diagram illustrating the details of the decompression control in the ventilation box V2 of the extruder according to the second embodiment. Figure 5 and Figure 3 Correspondingly.

[0088] like Figure 5 As shown, the extruder 10 according to this embodiment includes a pressure sensor P2, instead of... Figure 3 The pressure sensor P1 is included in the extruder 10 according to the modified example 1 of the first embodiment. Figure 3 The pressure sensor P1 shown is positioned closer to the ventilation box V2 than the control valve CV1. Conversely, Figure 5 The pressure sensor (second pressure sensor) P2 shown is positioned closer to the vacuum pump VP than the control valve CV1.

[0089] Pressure sensor P2 is similar to pressure sensor P1. Pressure sensor P2 detects the pressure in the pressure reduction path between control valve CV1 and vacuum pump VP. Note that when control valve CV1 is open, pressure sensor P2 can also detect the pressure in fume box V2.

[0090] Therefore, in this embodiment, the control valve CV1 is, for example, an on / off valve that only controls its opening and closing.

[0091] Next, the operation of the pressure reduction control performed by the controller CTR will be described.

[0092] First, such as Figure 5 As shown, when the extruder 10 is started and a sufficient amount of resin raw material is fed into the barrel 11, the upstream and downstream sides of the ventilation box V2 are filled with molten resin due to the structure of the screw 12, thus maintaining the airtightness of the ventilation box V2.

[0093] Subsequently, the controller CTR starts the vacuum pump VP. At this time, the control valve CV1 for depressurization is closed, the control valve CV2 for atmospheric release is open, and the interior of the ventilation box V2 is at atmospheric pressure.

[0094] After the vacuum pump VP is started, the controller CTR opens the closed control valve CV1. Note that the extruder 10 according to this embodiment also includes a control valve CV2 for atmospheric release, and this control valve CV2 is open when control valve CV1 is opened after the vacuum pump VP is started. Therefore, when control valve CV1 is open, the pressure in the vent box V2 decreases more slowly compared to when control valve CV2 is not set, thereby reducing the frequency of material overflow.

[0095] Furthermore, after the controller CTR opens the control valve CV1, the controller CTR controls the opening degree of the opened control valve CV2 to gradually reduce it, so that the pressure reduction rate detected by the pressure sensor P2 becomes the predetermined pressure reduction rate.

[0096] Furthermore, after the controller CTR starts the vacuum pump VP, but before the controller CTR opens the control valve CV1, the controller CTR can reduce the opening of the control valve CV2 until the pressure detected by the pressure sensor P2 reaches a predetermined pressure. Note that the predetermined pressure is the pressure at which material overflow does not occur when the control valve CV1 is opened.

[0097] In this way, similarly, in the extruder 10 according to the second embodiment, the number of times material overflow can be reduced while the opening degree of control valves CV1 and CV2 is automatically controlled by the controller CTR.

[0098] Constructions other than those described above Figure 3 The extruder 10 shown is similar in construction to the modified example 1 according to the first embodiment, therefore its description will be omitted. Furthermore, Figure 4 The material feed sensor S shown can be applied to Figure 5 The extruder 10 shown is according to the second embodiment.

[0099] (Third Implementation)

[0100] Next, we will refer to Figure 6 An extruder according to the third embodiment will be described. Figure 6 This is a block diagram illustrating the details of the decompression control in the ventilation box V2 of the extruder according to the third embodiment. Figure 6 and Figure 3 Correspondingly.

[0101] like Figure 6 As shown, the extruder 10 according to this embodiment has a configuration in which a pressure sensor (second pressure sensor) P2, which is positioned closer to the vacuum pump VP than the control valve CV1, is added to... Figure 3 The extruder 10 shown is a modified example 1 according to the first embodiment.

[0102] Next, the operation of the pressure reduction control performed by the controller CTR will be described.

[0103] First, such as Figure 6 As shown, when the extruder 10 is started and a sufficient amount of resin raw material is fed into the barrel 11, the upstream and downstream sides of the ventilation box V2 are filled with molten resin due to the structure of the screw 12, thus maintaining the airtightness of the ventilation box V2.

[0104] Subsequently, the controller CTR starts the vacuum pump VP. At this time, the control valve CV1 for depressurization is closed, the control valve CV2 for atmospheric release is open, and the interior of the ventilation box V2 is at atmospheric pressure.

[0105] In the extruder 10 according to this embodiment, after the controller CTR starts the vacuum pump VP, and before the controller CTR opens the control valve CV1, the controller CTR reduces the opening of the control valve CV2 until the pressure (second pressure) detected by the pressure sensor P2 reaches a predetermined pressure. Note that the predetermined pressure is the pressure at which material overflow does not occur when the control valve CV1 is opened.

[0106] Next, after the second pressure reaches the predetermined pressure, the controller CTR gradually increases the opening of the closed control valve CV1, so that the pressure reduction rate of the pressure (first pressure) detected by the pressure sensor P1 becomes the predetermined pressure reduction rate that prevents material leakage.

[0107] Note that the extruder 10 according to this embodiment also includes a control valve CV2 for atmospheric release, and the control valve CV2 is opened when the opening of the control valve CV1 is gradually increased after the vacuum pump VP is started. Therefore, in the extruder 10 according to this embodiment, when the opening of the control valve CV1 is gradually increased, the decompression rate can be more easily controlled to a predetermined decompression rate that prevents material overflow compared to the case where the control valve CV2 is not set.

[0108] Then, after the controller CTR fully opens the control valve CV1, the controller CTR controls the opening of the open control valve CV2 to gradually reduce it further, so that the pressure reduction rate detected by the pressure sensor P2 becomes the predetermined pressure reduction rate. At this time, the pressure detected by the pressure sensor P2 is basically the same as the pressure detected by the pressure sensor P1.

[0109] In this way, the controller CTR automatically controls the opening of the control valve CV1 based on the pressure detected by the pressure sensor P1, and automatically controls the opening of the control valve CV2 based on the pressure detected by the pressure sensor P2, thereby reducing the number of times material overflow occurs.

[0110] Constructions other than those described above Figure 3 The extruder 10 shown is similar in construction to the modified example 1 according to the first embodiment, therefore its description will be omitted. Furthermore, Figure 4 The material feed sensor S shown can be applied to Figure 6 The extruder 10 shown is according to the third embodiment.

[0111] Based on the present disclosure as described herein, it is apparent that implementations of the present disclosure can be modified in many ways. Such modifications should not be considered as departing from the spirit and scope of the present disclosure, and all such modifications that will be apparent to those skilled in the art are considered to be included within the scope of the following claims.

Claims

1. An extruder in which a screw housed in a barrel kneads and extrudes molten resin, the extruder comprising: A ventilation box, which is disposed inside the cylinder; A pressure reducing pump, which is connected to the ventilation box; A first control valve is disposed in a pressure reduction path that connects the ventilation box to the pressure reduction pump, and the first control valve is configured to operate based on a first control signal. A second control valve for atmospheric release is connected to the pressure reduction path, and the second control valve is configured to operate based on a second control signal; A pressure sensor configured to detect pressure in the pressure reduction path; as well as The controller is configured to output the first control signal and the second control signal based on the pressure detected by the pressure sensor, and to perform feedback control on the opening degree of the corresponding first control valve and the second control valve.

2. The extruder according to claim 1, wherein, The pressure sensor is a first pressure sensor that is positioned closer to the ventilation box than the first control valve. When the pressure reducing pump is started, the first control valve is closed, while the second control valve is open. After the controller starts the pressure reducing pump, the controller controls the opening of the closed first control valve to increase it, thereby changing the pressure reduction degree of the first pressure detected by the first pressure sensor to a predetermined pressure reduction degree. After the controller fully opens the first control valve, the controller controls the opening of the second control valve to reduce it, thereby reducing the pressure of the first pressure to a predetermined pressure.

3. The extruder according to claim 1, wherein, The pressure sensor is a second pressure sensor that is positioned closer to the pressure reducing pump than the first control valve. When the pressure reducing pump is started, the first control valve is closed, while the second control valve is open. The first control valve is an on / off valve. After the controller starts the pressure reducing pump, the controller opens the first control valve, and After the controller opens the first control valve, the controller gradually reduces the opening of the second control valve, thereby changing the pressure reduction degree of the second pressure detected by the second pressure sensor to a predetermined pressure reduction degree.

4. The extruder according to claim 3, wherein, The second control valve is positioned closer to the pressure reducing pump than the first control valve, and After the controller starts the pressure reducing pump, and before the controller opens the first control valve, the controller reduces the opening of the second control valve until the second pressure reaches a predetermined pressure.

5. The extruder according to claim 1, wherein, The pressure sensor includes: A first pressure sensor is positioned closer to the ventilation box than the first control valve; and A second pressure sensor is positioned closer to the pressure reducing pump than the first control valve. The second control valve is positioned closer to the pressure reducing pump than the first control valve. The controller performs feedback control on the opening degree of the first control valve based on the first pressure detected by the first pressure sensor, and The controller performs feedback control on the opening degree of the second control valve based on the second pressure detected by the second pressure sensor.

6. The extruder according to claim 5, wherein, When the pressure reducing pump is started, the first control valve is closed, while the second control valve is open. After the controller starts the pressure reducing pump, the controller reduces the opening of the second control valve until the second pressure reaches the predetermined pressure. After the second pressure reaches the predetermined pressure, the controller gradually increases the opening of the closed first control valve, thereby reducing the pressure of the first pressure to the predetermined pressure. After the controller fully opens the first control valve, the controller further gradually reduces the opening of the second control valve, thereby reducing the pressure of the second pressure to a predetermined pressure.

7. The extruder according to any one of claims 1 to 6, further comprising a material overflow sensor configured to detect material overflow in the ventilation box. in, When the overflow sensor detects overflow, the controller closes the first control valve.

8. The extruder according to claim 7, wherein, When the overflow sensor detects overflow, the controller fully opens the second control valve.

9. The extruder according to any one of claims 1 to 6, wherein, The first control valve and the second control valve are ball valves, and The controller controls the opening degree of the ball valve using proportional-integral control.

10. The extruder according to claim 9, wherein, The controller controls the opening degree of the ball valve using a two-degree-of-freedom proportional-integral control.

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