JP2008143022A - Injection device and operating method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection device capable of easily and effectively performing degassing for a molten material with a simple constitution, and an operating method thereof. <P>SOLUTION: The injection device 1 includes a heating cylinder 3 which plasticizes a molding material 27 supplied from a rear end part in cooperation with a screw 4 to make the molten material 28, the screw 4 rotatably and reciprocatably inserted and fitted to an inner hole 29 of the heating cylinder 3, a rotating means 16 which plasticizes the molding material 27 by rotationally driving the screw 4 and depressurizes the molten material 28 by rotating the screw 4 by a predetermined rotation angle in the opposite direction to the plasticizing rotational direction immediately after the plasticization is finished, an advancing and retreating means 9 which advances and retreats the screw 4 and holds the screw 4 so as not to move it in depressurizing the molten material 28, and an exhausting means 21 for exhausting the exhaust gas generating in depressurizing the molten material 28. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an injection apparatus that plasticizes a molding material into a molten material, and an operation method of the injection apparatus.

  In injection molding in which a molding material such as resin is plasticized in a heating cylinder fitted with a screw to form a molten material, which is injected into a mold cavity, in the plasticizing process, gas and moisture are generated as the molding material melts. appear. As a result of being injected into the mold cavity together with the molten material, problems such as causing silver streaks on the surface of the molded product, causing discoloration of the molded product, and attaching foreign substances consisting of gas components to the mold cavity surface, etc. Will occur. Therefore, conventionally, a vent type in which a decompression portion is provided in the middle portion of the screw and a vent port is provided in the heating cylinder wall corresponding to the position to deaerate has been adopted. However, in the vent type, the screw and the heating cylinder are complicated and the cost is increased, and the retention of the molding material based on the complicated configuration becomes a problem.

  For example, Patent Document 1 discloses a solution to such a vent type problem. In Patent Document 1, a suction hole is provided in a resin material supply portion at the base end of a heating cylinder which is built in such a manner that the screw can rotate forward and backward and move back and forth in the axial direction, and this suction hole and an external vacuum suction device are connected to a pipe. When the resin material is kneaded or plasticized, the screw is rotated forward / backward and reverse / forward repeatedly to induce the gas generated from the resin material to the heating cylinder base end, and from the base end through the suction hole, the heating cylinder The present invention relates to a vent mechanism of a screw type injection molding machine that discharges to the outside. However, according to the technique of Patent Document 1, since the gas generated from the resin material is released by repeating forward / reverse and reverse / forward during the plasticization, the plasticizing action becomes unstable and uniform melting. A resin material cannot be obtained.

Moreover, there exists patent document 2 in what reversely rotates a screw after a measurement process like this invention, for example. Patent Document 2 discloses a screw that is rotatably and reciprocally disposed in a heating cylinder, a screw head that is disposed at the tip of the screw, and a screw head that is disposed around the screw head. A non-return ring for preventing back flow of the resin at the time, advancing / retreating drive means for advancing and retreating the screw, a rotation driving means for rotating the screw forward and backward, and a control device. A reverse rotation means for reversely rotating the screw with a delay of a set period from the completion of the process to the start of the injection process, and a screw position holding means for holding the screw position while the screw is reversely rotated It is related with an injection device provided with these. However, in Patent Document 2, even when the molten resin is accurately measured, when the molten resin is injected, the molten resin flows backward during the movement to the seal of the check ring and is actually injected. In order to prevent the amount of the molten resin from fluctuating, the check ring is moved in advance to the sealing position by reversing the screw after a delay time from the completion of the metering. Therefore, Patent Document 2 makes its purpose and configuration different from that of the present invention.
Japanese Patent Publication No. 7-102596 Japanese Patent No. 2966679

  The present invention was invented in view of the above-described circumstances, and an object thereof is to provide an injection apparatus that can easily and effectively perform degassing of a molten material with a simple configuration and an operation method thereof. To do.

  The present invention comprises a heating cylinder that plasticizes a molding material supplied from a rear end portion into a molten material in cooperation with a screw, and the screw that is rotatably inserted into an inner hole of the heating cylinder, Rotating the screw to plasticize the molding material, and immediately after the plasticization is completed, the screw is rotated by a predetermined rotation angle in a direction opposite to the plasticizing rotation direction to decompress the molten material. An injection device comprising: means, forward / reverse means for moving the screw forward and backward and holding the screw so as not to move when the molten material is depressurized, and exhaust means for discharging an exhaust body generated when the molten material is depressurized About.

  According to the injection device and the operating method of the present invention, it is possible to easily and effectively realize the degassing of the molten material with a simple configuration.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of an injection apparatus showing a state during plasticization. FIG. 2 is a cross-sectional view showing the state of the heating cylinder and the screw when the screw is driven in reverse rotation. FIG. 3 is a flowchart showing the operation method of the injection apparatus of the present invention.

  The injection device 1 includes an inner hole 29 having a through hole through which a molding material 27 supplied from a drop port 17 is passed and a nozzle 2 is screwed to a front end surface and communicated from the through hole to the nozzle 2. On the heating cylinder 3, a screw 4 fitted in the inner hole 29 of the heating cylinder 3 so as to be able to rotate and reciprocate, a housing 8 in which the heating cylinder 3 is fixed to the front surface and a drop port 17 is perforated, and an upper surface of the housing 8 The adjusting means 31 that is fixed so as to communicate with the dropping port 17 and adjusts the conveyance amount of the molding material 27 and the molding material 27 that is fixed to the upper surface of the adjusting means 31 and communicates with the adjusting means 31 while maintaining airtightness. Supply means 22 for supplying to means 31, movable board 15 for attaching screw 4 so as to be rotatable and non-movable in the axial direction, and fixed to the rear surface of movable board 15, its output shaft being connected to screw 4 to drive screw 4 to rotate. Servo motor A rotating means 16 comprising: a ball screw 13 screwed into a ball nut 14 provided on the movable plate 15 and attached to the housing 8 so as to be rotatable and axially immovable; and the ball screw 13 is connected to the pulleys 10 and 12 and the belt 11. And a forward / reverse means 9 comprising a servo motor or the like that is rotationally driven via the.

  The supply means 22 has a cylindrical supply cylinder 23 having a material inlet 26 on the upper surface and an opening communicating with the adjustment means 31 on the lower surface, and moves horizontally in the upper and lower portions of the supply cylinder 23 to supply the supply cylinder 23. The shutters 24 and 25 divide the internal space in a freely openable and closable manner. The molding material 27 charged from the material charging port 26 is deposited on the upper surface of the closed shutter 24. Next, after closing the shutter 25, the molding material 27 deposited on the upper surface of the shutter 24 is dropped and deposited on the upper surface of the shutter 25 by opening the shutter 24. Then, after closing the shutter 24, the molding material 27 deposited on the upper surface of the shutter 25 is supplied to the adjusting means 31 by opening the shutter 25. As described above, since either the shutter 24 or the shutter 25 is closed, the supply unit 22 can supply the molding material 27 to the adjusting unit 31 while being always airtight.

  The adjusting means 31 has an upper opening that communicates with the supply means 22, a lower opening that communicates with the opening of the drop port 17 on the upper surface of the housing 8, and an exhausting means 21 that is a through-hole drilled in the opposing portion of the lower opening. A feed screw 19 is rotatably inserted into the transport cylinder 18. The feed screw 19 is driven by a motor 20 so as to be variable in speed, and the molding material 27 that has flowed in from the supply means 22 reaches the dropping port 17 according to the material and type of the molding material 27 or the molten state in the inner hole 29 of the heating cylinder 3. The rotation is controlled at an appropriately set rotation speed. That is, the molding material 27 having a high viscosity of the molten material is controlled at a relatively low speed, and the bulky molding material 27 is controlled at a relatively high speed. In any case, the unmelted molding material 27 in the rear part of the screw 4 in the inner hole 29 of the heating cylinder 3 is supplied by being controlled and controlled by the adjusting means 31. There is only a small amount compared to the case where the material 27 is deposited.

  The screw 4 has an outer diameter slightly smaller than the inner diameter of the inner hole 29 on the outer periphery of the screw shaft 5 composed of a small-diameter base, a large-diameter tip, and an intermediate portion in which the small-diameter and the large-diameter are connected in a tapered shape. In this way, the flight 6 is continuously wound in a spiral shape. The base portion is referred to as a feed zone, the intermediate portion is referred to as a compression zone, and the tip portion is referred to as a metering zone.

  Next, the plasticizing process will be described in detail while adding the process numbers in the flowchart of FIG. When the plasticization starts (S1), the molding material 27 supplied to the feed zone hardly exists above the screw shaft 5 as shown in FIG. In this state, the molding material 27 is kneaded while receiving heat from the flight 6 and the wall surface of the inner hole 29 that advance in the forward direction (AN) in the forward direction of the screw 4 that rotates in the forward direction (RN) and is conveyed to the compression zone. The molding material 27 starts to melt before and after reaching the compression zone and is compressed in the compression zone to become the molten material 28, and the ratio increases as the conveyance proceeds. Since the molten material 28 receives the conveying force from the wall surface in the forward traveling (AN) direction of the flight 6, it is concentrated on the wall surface. When the molten material 28 reaches the metering zone, substantially the whole is in a molten state and fills the space formed by the wall surfaces of the screw shaft 5, the flight 6, and the inner hole 29 without a gap.

  In such a plasticizing process, the molten material 28 is pushed forward of the screw 4 and the nozzle 2 is brought into contact with a mold (not shown) or closed with a shaft off valve (not shown). 28 is stored in the inner hole 29 in front of the screw 4. As described above, since the molten material 28 has a pressure based on the forward travel (AN) of the flight 6, the screw 4 moves backward against the back pressure generated by the forward / backward moving means 9. This retreat distance is set in advance according to the volume of the molded product, and when the screw 4 reaches its measurement set value (S2), the forward rotation (RN) is stopped and plasticization is completed (S3). . Immediately thereafter, the screw 4 starts to rotate in the reverse rotation (RR) rotation direction opposite to the normal rotation (RN) rotation direction during plasticization (S4). This rotation angle is preferably 360 degrees or more. For this reason, the control device 30 has a set value that considers 1 when the signal from the rotation angle detector provided in the rotation means 16 corresponds to the rotation angle 360 degrees of the screw 4, and this set value can be set as an integer. I did it. Therefore, the screw 4 can reversely rotate (RR) by a predetermined number of rotations set by the control device 30. With this configuration, the setting value required for three or more digits is only one digit, and it is easy to understand conceptually. Therefore, it is very easy to set the reverse rotation angle of the screw.

  When the screw 4 is rotated in the reverse direction (RR), the servo motor as the forward / rearward moving means 9 is positioned and servo-locked so that the screw 4 does not move forward and backward and maintains the plasticized position (S5). When the forward / backward moving means 9 is not a servo motor but a hydraulic cylinder device, the two chambers defined by the pistons of the hydraulic cylinder are sealed with pressure oil or the positioning is controlled by a servo valve. Otherwise, the reversely rotating (RR) screw 4 is moved forward by the molten material 28 in a female screw state.

  When the screw 4 rotates in the reverse direction (RR), as shown in FIG. 2, the flight 6 proceeds in the reverse traveling (AR) direction. Thereby, the accumulated pressure of the molten material 28 is released, and the molten material 28 concentrated and deposited on the front surface of the flight 6 in the forward traveling (AN) direction is separated from the surface while being kneaded. Therefore, exhaust bodies such as gas, air, and moisture contained in the molten material 28 are released. As an example, the rotational speed of the reverse rotation (RR) of the screw 4 is 60 RPM, but the exhaust body tends to be released more when the rotational speed is higher. The discharged exhaust body flows to the rear part of the screw 4 having a gap between the flights 6 and is discharged from the exhaust means 21 via the drop port 17. At this time, if an inert gas such as nitrogen gas is pressurized and supplied from the gas supply port 7 provided in the intermediate portion of the heating cylinder 3 corresponding to the compression zone position of the screw 4, the exhaust passage of the exhaust body is easy. And is effective in preventing the oxidation / burning phenomenon of the molten material 28. Further, in order to reduce the deposition amount of the molding material 27 in the feed zone and facilitate the passage of the exhaust body, the rotation speed of the feed screw 19 of the adjusting means 31 has reached the predetermined distance before the measurement set value by the screw 4. Sometimes it is effective to switch to a relatively low speed.

  A vacuum pump (not shown) is connected to the exhaust means 21. A seal portion 32 is provided at a portion where the screw shaft 5 protrudes from the housing 8, and the supply unit 22 is airtightly fixed to an adjustment unit 31 that is configured to hermetically seal the inside of the transport cylinder 18. The heating cylinder 3 and the adjusting means 31 are fixed to the housing 8 so as to be airtight. Therefore, the molding material 27 is executed under a reduced pressure atmosphere reduced by a vacuum pump from the time it is charged until melting. The exhaust body may be directly discharged from the exhaust means 21 to the atmosphere without connecting a vacuum pump. In that case, the supply means 22 and the seal part 32 become unnecessary. When the seal portion 32 is not provided, the inner hole 29 opens to the rear surface of the housing 8 as an extension thereof, and serves as an exhaust means that can exhaust the exhaust body from the opening. Furthermore, the adjustment means 31 can be omitted. At this time, the molding material 27 fills the feed zone, but the molding material 27 is in an unmelted state, and the exhaust body can be discharged through the gap between the pellets of the molding material 27. The exhaust means 21 at this time is the opening of the inner hole 29 as described above (when no vacuum pump is provided) or a hole drilled in the housing 8 so as to communicate with the drop port 17 (when a vacuum pump is provided). )

  When the rotation angle of the reverse rotation (RR) of the screw 4 is detected by a signal of a rotation angle detector provided in the rotation means 16 and the value reaches a set value (S6), the reverse rotation (RR) of the screw 4 is detected. Stop (S7). Thereafter, in order to prevent the molten material 28 from dripping from the nozzle 2, a suck back for slightly retracting the screw 4 is performed as necessary. In order to promote the discharge of the exhaust body from the molten material 28, immediately after the plasticization is finished, the screw 4 is rotated in the reverse rotation (RR) direction by a predetermined rotation angle, and then again forward rotation (RN) and reverse rotation ( RR) may be repeated a predetermined number of times. Even during forward rotation (RN) and reverse rotation (RR) at this time, the screw 4 is held by the forward-reverse means 9 so as not to be able to move forward and backward.

  The present invention is not limited to the embodiment described above, and various modifications can be added and implemented without departing from the spirit of the invention.

It is sectional drawing of the injection device which shows the state under plasticization. It is sectional drawing which shows the state of a heating cylinder and a screw when a screw is reversely driven. It is a flowchart which shows the operating method of the injection device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection device 2 Nozzle 3 Heating cylinder 4 Screw 5 Screw shaft 6 Flight 7 Gas supply port 8 Housing 9 Forward / reverse means 10, 12 Pulley 11 Belt 13 Ball screw 14 Ball nut 15 Movable plate 16 Rotating means 17 Drop port 18 Transport cylinder 19 Feed screw 20 Motor 21 Exhaust means 22 Supply means 23 Supply cylinder 24, 25 Shutter 26 Material input port 27 Molding material 28 Melted material 29 Inner hole 30 Controller 31 Adjusting means 32 Seal part RN Forward rotation RR Reverse rotation AN Forward travel AR Reverse Progression

Claims (10)

  A heating cylinder that plasticizes the molding material supplied from the rear end portion into a molten material in cooperation with the screw, the screw that is fitted in the inner hole of the heating cylinder so as to be able to rotate and reciprocate, and the screw. A rotating means for driving to plasticize the molding material and immediately after the plasticization is completed, to rotate the screw by a predetermined rotation angle in a direction opposite to the rotation direction of the plasticization to depressurize the molten material; Injection comprising: a forward / reverse means for moving the screw back and forth and holding the screw so as not to move when the molten material is depressurized; and an exhaust means for discharging an exhaust body generated when the molten material is depressurized. apparatus.   The injection apparatus according to claim 1, further comprising an adjusting unit that adjusts an amount of the molding material supplied to a rear end portion of the heating cylinder.   The injection apparatus according to claim 1 or 2, wherein a vacuum pump is connected to the exhaust means.   The injection device according to any one of claims 1 to 3, wherein a gas supply port is provided in an intermediate portion of the heating cylinder. An injection device having a heating cylinder that plasticizes a molding material supplied from a rear end portion into a molten material in cooperation with a screw, and the screw that is inserted into an inner hole of the heating cylinder so as to be able to rotate and reciprocate. In driving method,
Immediately after the end of plasticization, the screw is rotated by a predetermined rotation angle in the reverse rotation direction opposite to the normal rotation that is the rotation direction of plasticization to depressurize the molten material, and the exhaust body generated at that time is exhausted. A method of operating an injection device, characterized in that the discharge device is discharged.   The operation method of the injection apparatus according to claim 5, wherein the amount of the molding material supplied to the heating cylinder during plasticization is adjusted by an adjusting means.   The method for operating the injection apparatus according to claim 5 or 6, wherein the exhaust body is released from the molten material in a reduced-pressure atmosphere.   The injection according to any one of claims 5 to 7, wherein nitrogen gas is supplied from a gas supply port provided in an intermediate portion of the heating cylinder when the screw is rotated in the reverse rotation direction by a predetermined rotation angle. How to operate the device.   The injection device according to any one of claims 5 to 8, wherein the screw is rotated by a predetermined rotation angle in the reverse rotation direction immediately after the plasticization is completed, and then the forward rotation and the reverse rotation are repeated again. Driving method.   When the screw is rotated forward or backward after plasticizing, the set value of the control device for setting the predetermined rotation angle is a rotation means for rotating the screw corresponding to the 360-degree rotation angle of the screw. The method for operating an injection device according to any one of claims 5 to 9, wherein the rotation angle is set to 1 and an integer is set.

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