JP5732336B2 - Screw type injection device - Google Patents

Description

  The present invention relates to a screw-type injection device provided in an injection molding machine, and more particularly to a drive mechanism for a check ring for backflow prevention provided in a neck portion of a screw.

  A screw type injection device provided in an injection molding machine injects and fills a predetermined amount of molten resin into a mold cavity. A screw is placed in a heating cylinder in which a heating element called a band heater is mounted on the outer periphery. It is stored so that it can rotate and move forward and backward. Injection / filling of the molten resin into the mold cavity is performed by repeating the steps of resin kneading and plasticization, suck back, and injection / filling.

  In the resin kneading / plasticizing step, the screw is driven to rotate in a heating cylinder. On the base end side of the heating cylinder, there is a raw material supply hole for introducing pellet-shaped raw material resin falling from the hopper into the heating cylinder. A spiral groove extending from the position facing the hole to the tip is formed. Therefore, when the screw is rotationally driven in the heating cylinder, the raw material resin supplied into the heating cylinder through the raw material supply hole is received in the space formed by the inner surface of the heating cylinder and the surface of the spiral groove, and the rotation of the screw Accordingly, the screw is sequentially transferred along the spiral groove to the tip side of the screw. In this process, the raw material resin is melted by heating by a heating element and shearing heat and frictional heat accompanying rotation of the screw, and necessary kneading and plasticization are performed. A certain amount of the plasticized molten resin is stored in a resin reservoir formed between the injection nozzle attached to the tip of the heating cylinder and the tip of the screw.

  After the resin kneading and plasticizing process is completed, in order to prevent the molten resin from flowing out of the injection nozzle (drooling), a suckback is performed to lower the resin pressure in the resin reservoir by retracting the screw without rotation. Is called.

  In the molten resin injection / filling process, the screw is driven forward toward the injection nozzle at a high speed. As a result, a fixed amount of molten resin stored in the resin reservoir is injected and filled into the mold cavity, and a desired molded product is formed.

  A backflow prevention device is attached to the screw so that the molten resin stored in the resin reservoir in the molten resin injection / filling process does not return to the base end side of the screw. Thereby, the resin filling amount into the mold cavity for each shot is stabilized, and good products can be molded with a high yield.

  As shown in FIG. 6 and FIG. 7, the applicant of the present application, as shown in FIGS. 6 and 7, as a backflow prevention device provided in the screw, a screw head 102 attached to the distal end portion of the screw body 100 via a small-diameter neck portion 101 and A check sheet 103 fixed to the attachment side end of the screw head 102 of the screw body 100 and a check ring 104 loosely fitted to the neck portion 101 so as to be able to move forward and backward and to be rotatable. Is provided with a locking claw portion 105 that protrudes toward the check ring 104 and has a flat end surface. The locking claw portion 105 is accommodated at the end of the check ring 104 on the screw head 102 side. A recess 106 that is configured to be capable of projecting and projecting toward the screw head 102 along the recess 106, and its end surface being a flat surface. And a locking portion 107 has proposed one provided (e.g., see Patent Document 1.). 6 and 7, reference numeral 109 indicates an engagement groove formed in the screw head 102, and reference numeral 110 indicates a locking claw formed on the check ring 104. The locking claw 110 is slidably inserted into the engagement groove 109 and allows the check ring 104 to move forward and backward relative to the screw head 102 and restricts the rotation of the check ring 104 relative to the screw body 100 and the screw head 102.

  Below, operation | movement of the backflow prevention apparatus of patent document 1 is demonstrated. First, in the resin kneading / plasticizing step, the screw main body 100, the screw head 102, and the check ring 104 are integrally rotated, and the resin supplied along the spiral groove formed in the screw main body 100 is used. Since the check ring 104 is pressed toward the screw head 102 by the resin pressure, the locking claw portion 105 of the screw head 102 is fitted into the recess 106 of the check ring 104 as shown in FIG. Accordingly, the check ring 104 is separated from the check sheet 103, the resin passage 108 formed between the check sheet 103 and the check ring 104 is opened, and the kneaded and plasticized resin is transferred to the resin reservoir side. .

  After completion of the resin kneading / plasticizing step, the screw body 100, the screw head 102, and the check ring 104 are slightly rotated in reverse. As a result, the locking claw portion 105 of the screw head 102 is detached from the concave portion 106 of the check ring 104, and the locking claw portion 105 of the screw head 102 and the locking portion 107 of the check ring 104 are connected as shown in FIG. Abutting between flat surfaces. At this time, since the check ring 104 is pressed by the locking claw portion 105 of the screw head 102 and is in close contact with the check sheet 103, the resin passage 108 formed between the check sheet 103 and the check ring 104 is closed. In addition, backflow of the molten resin during suck back and injection / filling is prevented.

Japanese Patent No. 3433278

  However, in the technique described in Patent Document 1, the check ring 104 rotates integrally with the screw main body 100 and the screw head 102 in the resin kneading and plasticizing process, so that the outer surface of the check ring 104 and the inner surface of the heating cylinder 200 are rotated. Friction is generated between these members, and inconveniences such as wear and seizure tend to occur between these members. In particular, when it is applied to injection molding of a fiber kneaded resin, since the fibers are likely to enter between the outer surface of the check ring 104 and the inner surface of the heating cylinder 200, the above inconvenience is more likely to occur. In addition, the technique described in Patent Document 1 has a problem that the manufacturing cost becomes expensive because both the screw head 102 and the check ring 104 need to be specially processed.

  The present invention has been made in order to solve such problems of the prior art, and the object thereof is a screw type that can be implemented at low cost and does not easily cause galling or seizure on the outer surface of the check ring and the inner surface of the heating cylinder. It is to provide an injection device.

In order to solve the above problems, the present invention comprises a heating cylinder, a screw housed in the heating cylinder so as to be rotatable and capable of moving back and forth, and a backflow prevention device attached to the screw, the screw comprising: A screw main body having a spiral groove and a screw head fixed to the tip of the screw main body through a small-diameter neck, and the backflow prevention device is fixed to the end of the screw main body on the screw head mounting side. In the screw type injection device comprising the check sheet and the check ring mounted on the neck so as to be capable of rotating forward and backward, the backflow prevention device is formed on an end surface of the screw head on the check ring side. a plurality of balls loosely fitted grooves formed at equal intervals in the circumferential direction of the screw head, rolling in the ball loosely fitted in the groove And the ball loosely fitting groove is connected to the deep groove portion and the shallow groove portion. The deep groove portion, the shallow groove portion, and the connecting portion are adjusted in position so that a part of the circumferential surface of the ball accommodated therein is always in contact with the inner surface of the heating cylinder. It is, and, when placing the balls in the deep groove portion, the check ring is separated from the check sheet to allow the distribution of the molten resin in the neck, and placing the ball into the shallow groove In this case, the check ring is in close contact with the check sheet, and the molten resin cannot be circulated in the neck.

According to such a configuration, the ball is arranged to be able to roll between the screw head and the check ring, and a part of the circumferential surface of the ball abuts against the end surface of the check ring. Therefore, even when the screw body and the screw head rotate. The check ring does not rotate with respect to the heating cylinder, and wear and seizure of the outer surface of the check ring and the inner surface of the heating cylinder are prevented. In addition, since the check ring does not rotate with respect to the heating cylinder, foreign matter is hardly sandwiched between the outer surface of the check ring and the inner surface of the heating cylinder, and the fiber-mixed resin can be molded with high efficiency. Furthermore, a ball loose fitting groove having a deep groove portion and a shallow groove portion is formed on the end face of the screw head, and the check ring is opened and closed with respect to the check seat via a ball arranged in the ball loose fitting groove. In addition, it is possible to reliably prevent the backflow of the molten resin during injection / filling and suck back. In addition, since the ball contact surface of the check ring can be a flat surface, it is possible to reduce the processing cost of the check ring and consequently the manufacturing cost of the screw type injection device. In addition, when a plurality of ball loose fitting grooves are formed at equal intervals in the circumferential direction of the end face of the screw head, the check ring can be held by a plurality of balls accommodated in each ball loose fitting groove, so that the operation stability of the check ring is improved. Can be increased. Furthermore, if a part of the circumferential surface of the ball is brought into contact with the inner surface of the heating cylinder, the rotation and forward / backward movement of the screw can be performed stably, so that the outer surface of the check ring and the outer surface of the heating cylinder are worn or seized. Can be prevented.

  In the screw type injection device of the present invention, the ball is disposed between the screw head and the check ring so as to be able to roll, and a part of the peripheral surface of the ball comes into contact with the end face of the flat check ring. Even when the screw body and the screw head are rotated, the check ring does not rotate with respect to the heating cylinder, and wear and seizure of the outer surface of the check ring and the inner surface of the heating cylinder are prevented. In addition, since the check ring does not rotate with respect to the heating cylinder, foreign matter is hardly sandwiched between the outer surface of the check ring and the inner surface of the heating cylinder, and the fiber-containing resin can be molded with high efficiency. Furthermore, since the ball contact surface of the check ring can be a flat surface, the processing cost of the check ring can be reduced, and the manufacturing cost of the screw type injection device can be reduced.

It is a lineblock diagram of the screw type injection device concerning an embodiment. It is principal part sectional drawing which shows the state in the kneading | mixing and plasticizing process of the backflow prevention apparatus with which the screw type injection device which concerns on embodiment is equipped. It is principal part sectional drawing which shows the state in the injection | emission and filling process of the backflow prevention apparatus with which the screw type injection device which concerns on embodiment is equipped. It is AA sectional drawing of FIG. It is the perspective view which partially saw through the backflow prevention device with which the screw type injection device concerning an embodiment is equipped. It is sectional drawing which shows the state in the kneading | mixing and plasticizing process of the backflow prevention apparatus with which the screw type injection device which concerns on a prior art example is equipped. It is sectional drawing which shows the state in the injection | emission and filling process of the backflow prevention apparatus with which the screw type injection device which concerns on a prior art example is equipped.

  Hereinafter, the screw-type injection device according to the embodiment will be described with reference to the drawings.

  As shown in FIG. 1, the screw-type injection device according to the embodiment includes a head stock 1 and a holding plate 2 that are arranged on a not-shown injection unit base board at a predetermined distance so as to face each other. A plurality of connecting bars 3 spanned between the holding plate 2, a linear motion block 4 guided by these connecting bars 3 to move forward and backward between the headstock 1 and the holding plate 2, and a base end A heating cylinder 5 fixed to the headstock 1, a nozzle 6 attached to the tip of the heating cylinder 5, a band heater 7 wound around the outer periphery of the heating cylinder 5, and rotatable within the heating cylinder 5. And a screw 8 arranged so as to be able to move forward and backward. A base end portion of the screw 8 is held by a rotating body 9, and the rotating body 9 is rotatably held by the linear motion block 4 via a bearing 9a. Further, a driven pulley 10 is fixed to the rotating body 9, and this driven pulley 10 is interposed between a driving pulley 12 fixed to an output shaft of a measuring servo motor 11 mounted on the linear motion block 4. A timing belt (not shown) is looped around. Accordingly, the screw 8 is rotationally driven by the measuring servo motor 11 via the driving pulley 12, a timing belt (not shown), the driven pulley 10 and the rotating body 9.

  An injection servomotor 13 is mounted on the holding plate 2 and the screw shaft 16 of the ball screw mechanism 15 is rotatably held via a bearing 2a. The ball screw mechanism 15 includes a screw shaft 16 and a nut body 17 screwed to the screw shaft 16, and an end portion of the nut body 17 is fixed to the linear motion block 4 via a load cell unit 18. ing. A driven pulley 19 is fixed to the end of the screw shaft 16, and a timing belt (not shown) is provided between the driven pulley 19 and a drive pulley 14 fixed to the output shaft of the injection servomotor 13. It is hung. Accordingly, the screw 8 is moved forward and backward by the injection servo motor 13 through the driving pulley 14, a timing belt (not shown), the driven pulley 19, the ball screw mechanism 15, the linear motion block 4, and the rotating body 9. The load cell unit 18 detects the injection pressure of the molten resin into a mold cavity (not shown).

  Reference numeral 20 in the figure is drilled at a corresponding position of the head stock 1 and the heating cylinder 5 in order to supply a molding material dropped / supplied from a hopper (not shown) into the rear end portion of the heating cylinder 5. The molding material supply hole is shown.

  As shown in FIGS. 1 to 5, the screw 8 includes a screw body 31 having a spiral groove 8 a and a screw head 33 fixed to a distal end portion of the screw body 31 through a small-diameter neck portion 32. The part 32 is provided with a backflow prevention device 40.

  As shown in FIGS. 2 to 5, the backflow prevention device 40 includes a screw head 33, a check sheet 41 fixed to the end of the screw body 31 on the screw head mounting side, and a neck portion 32 that can rotate and move forward and backward. The check ring 42 is detachably mounted, and the ball (steel ball) 43 is disposed between the screw head 33 and the check ring 42 so as to be able to roll.

  As shown in FIGS. 2 to 5, three ball loose fitting grooves 44 extending in the circumferential direction are formed at equal intervals on the end face of the screw head 33 on the check ring 42 side. In each ball loose fitting groove 44, a deep groove portion 44a, a shallow groove portion 44b, and a connecting portion 44c that connects these portions are equally formed in the same direction.

  As shown in FIG. 2, when the ball 43 enters, the deep groove portion 44 a separates the check sheet 41 and the check ring 42, and forms a resin passage 45 formed between the check sheet 41 and the check ring 42. It is formed so that the molten resin can pass through. On the other hand, as shown in FIG. 3, the shallow groove portion 44b is formed between the check sheet 41 and the check ring 42 when the ball 43 enters and the check sheet 41 and the check ring 42 are in close contact with each other. The resin passage 45 is formed to be blocked. The formation positions of the deep groove portion 44a, the shallow groove portion 44b, and the connecting portion 44c of the ball loose fitting groove 44 are adjusted so that a part of the peripheral surface of the ball 43 is always in contact with the inner surface of the heating cylinder 5.

  Hereinafter, the operation of the screw-type injection device according to the embodiment configured as described above will be described. The screw-type injection device according to the embodiment controls the driving and stopping of the metering servo motor 11 and the injection servo motor 13 for each molding cycle, so that the resin kneading / plasticizing process, suck back and molten resin are performed. The injection and filling processes are repeated in this order.

  In the resin kneading / plasticizing step, the measuring servo motor 11 is rotationally driven in a predetermined direction based on a command from a control device (not shown), and a driving pulley 12, a timing belt (not shown), a driven pulley 10 and a rotating body 9 are driven. Then, the screw 8 is driven to rotate in a predetermined direction. By the rotation of the screw 8, the raw material resin is supplied from the hopper (not shown) through the raw material supply hole 20 to the inner rear end side of the heating cylinder 5. The raw material resin is transferred forward by the screw feed action of the screw 8 while being plasticized and kneaded, and is stored as a molten resin on the front side of the screw 8. As the molten resin is fed to the front side of the screw 8, the screw 8 moves backward. At this time, the injection servomotor 13 is driven and controlled by pressure feedback control based on a command from a control device (not shown). A predetermined back pressure is applied to the screw 8 by controlling the linear movement position. When one shot of molten resin is stored on the tip side of the screw 8, the rotational drive of the screw 8 by the measuring servo motor 11 is stopped.

  As described above, in the resin kneading and plasticizing step, the screw 8 is driven to rotate, and the plasticized resin is sequentially transferred to the tip end side of the screw 8, so that the check ring 42 passes through the spiral groove 8a. It is pressed against the screw head 33 side by the resin pressure of the transferred resin. At this time, since the ball 43 is disposed between the screw head 33 and the check ring 42, the check ring 42 does not rotate with respect to the heating cylinder 5 even if the screw 8 is driven to rotate. 31 and the check ring 42 are relatively displaced in the circumferential direction. Accordingly, the ball 43 enters the deep groove portion 44a of the ball loose fitting groove 44, and the check ring 42 is separated from the check sheet 41 as shown in FIG. 2, so that the ball 43 is formed between the check sheet 41 and the check ring 42. The resin passage 45 is opened, and the kneaded and plasticized resin is transferred to the resin reservoir side.

  After completion of the resin kneading / plasticizing step, the screw 8 is rotated in a slightly reverse direction. Also at this time, since the ball 43 is disposed between the screw head 33 and the check ring 42, the check ring 42 does not rotate with respect to the heating cylinder 5, and the screw body 31 and the check ring 42 are The ball 43 is relatively displaced in the circumferential direction, and the ball 43 enters the shallow groove portion 44b from the deep groove portion 44a of the ball loose fitting groove 44 through the connecting portion 44c. At this time, since the screw 8 is not rotationally driven in the resin kneading / plasticizing direction and the resin pressure in the spiral groove 8a is low, the check ring 42 is easily retracted to the check sheet 41 side. As a result, the check ring 42 comes into close contact with the check sheet 41, and the resin passage 45 formed between the check sheet 41 and the check ring 42 is blocked.

  Thereafter, the screw 8 is forcibly retracted by a predetermined amount to perform a suck back for reducing the resin pressure in the resin reservoir. During suckback, the injection servomotor 13 is driven and controlled in the direction opposite to the rotation direction in the injection / filling process by pressure feedback control based on a command from a control device (not shown). When the injection servo motor 13 is rotationally driven, the rotational motion is transmitted to the ball screw mechanism 15 via the drive pulley 14, a timing belt (not shown), and the driven pulley 19, and the ball screw mechanism 15 converts the rotational motion into a linear motion. Is done. The linear motion is transmitted to the screw 8 via the load cell unit 18, the linear motion block 4 and the rotating body 9, and the screw 8 is driven backward. At the time of suck back, the resin pressure on the screw body 31 side is higher than the resin pressure in the molten resin reservoir, but the check ring 42 is in close contact with the check sheet 41 by the balls 43, so the check ring 42 is in contact with the check sheet 41. Therefore, the molten resin is prevented from flowing backward.

  The injection / filling step of the molten resin is performed by driving and controlling the injection servo motor 13 by speed feedback control based on a command from a control device (not shown) at an appropriate timing after completion of suck back. . When the injection servo motor 13 is rotationally driven, the rotational motion is transmitted to the screw 8 through the same path as during suckback, and the screw 8 is rapidly driven forward and stored on the tip side of the screw 8. Molten resin is injected and filled into a mold cavity in a mold-clamped state, and a primary injection process is executed. In the pressure holding process subsequent to the primary injection process, the injection servo motor 13 is driven and controlled by pressure feedback control based on a command from a control device (not shown). Is added to the resin filled. In the injection / filling process of the molten resin, the resin pressure in the molten resin reservoir is higher than the resin pressure on the screw body 31 side, so that the check ring 42 is not separated from the check sheet 41 and the back flow of the molten resin is prevented. The

  In the screw injection device according to the present embodiment, the ball 43 is arranged to be able to roll between the screw head 33 and the check ring 42, and a part of the peripheral surface of the ball 43 abuts against the end surface of the check ring 42. Even when the screw 8 rotates, the check ring 42 does not rotate with respect to the heating cylinder 5, and wear and seizure of the outer surface of the check ring 42 and the inner surface of the heating cylinder 5 can be prevented. Further, since the check ring 42 does not rotate with respect to the heating cylinder 5, foreign matter is not easily caught between the outer surface of the check ring 42 and the inner surface of the heating cylinder 5, and the fiber-containing resin can be molded with high efficiency. it can. Further, in the screw injection device according to the present embodiment, a ball loose fitting groove 44 having a deep groove portion 44 a and a shallow groove portion 44 b is formed on the end surface of the screw head 33, and the ball 43 disposed in the ball loose fitting groove 44. Since the check ring 42 is opened and closed with respect to the check sheet 41, the backflow of the molten resin at the time of injection / filling and suck back can be reliably prevented. In addition, in the screw injection device according to the present embodiment, since the ball contact surface of the check ring 42 is a flat surface, the check ring 42 has a flat surface compared with a case where the check ring 42 is specially processed for preventing backflow. The processing cost can be reduced, and the manufacturing cost of the screw type injection device can be reduced.

  In addition, in the screw injection device according to the present embodiment, the three ball loose fitting grooves 44 are formed at equal intervals in the circumferential direction of the end face of the screw head 33, so that the three balls accommodated in each ball loose fitting groove 44 The check ring 43 can be held at three points by 43, and the operation stability of the check ring 42 can be improved. In addition, the screw injection device according to the present embodiment always causes a part of the ball 43 accommodated in the ball loose fitting groove 44 to abut against the inner surface of the heating cylinder 5, so that the screw 8 rotates and moves forward and backward. This can be performed stably, and wear and seizure of the outer surface of the check ring 42 and the outer surface of the heating cylinder 5 can be prevented.

  The present invention can be used for a screw type injection device or a screw pre-pull type injection device.

DESCRIPTION OF SYMBOLS 1 Headstock 2 Holding plate 3 Connecting bar 4 Linear motion block 5 Heating cylinder 6 Nozzle 7 Band heater 8 Screw 8a Spiral groove 9 Rotating body 10 Driven pulley 11 Weighing servo motor 12 Drive pulley 13 Injection servo motor 14 Drive pulley 15 Ball screw Mechanism 16 Screw shaft 17 Nut body 18 Load cell unit 19 Driven pulley 20 Molding material supply hole 31 Screw body 32 Neck 33 Screw head 40 Backflow prevention device 41 Check sheet 42 Check ring 43 Ball (steel ball)
44 Ball loose fitting groove 44a Deep groove portion 44b Shallow groove portion 44c Connecting portion

Claims (1)

A heating cylinder, a screw housed in the heating cylinder so as to be rotatable and movable back and forth, and a backflow prevention device attached to the screw, the screw having a spiral groove, and the screw body A check head fixed to an end of the screw body on the screw head mounting side, and a screw seat fixed to the tip of the screw head through a small-diameter neck. In a screw-type injection device consisting of a check ring that can be moved forward and backward,
The backflow prevention device is formed on an end surface of the screw head on the check ring side, and has a plurality of ball loose fitting grooves formed at equal intervals in the circumferential direction of the screw head, and rolls into the ball loose fitting groove. A ball that is stored in such a manner that a part of its peripheral surface is in contact with the end surface of the check ring formed in a flat shape;
The loose ball fitting groove is composed of a deep groove portion, a shallow groove portion, and a connecting portion that connects them, and the deep groove portion, the shallow groove portion, and the connecting portion are formed on the peripheral surface of the ball accommodated therein. When the formation position is adjusted so that a part is always in contact with the inner surface of the heating cylinder, and the ball is disposed in the deep groove portion, the check ring is separated from the check sheet and melts in the neck portion. Resin can be circulated, and when the ball is disposed in the shallow groove portion, the check ring comes into close contact with the check sheet and the circulated resin cannot be circulated in the neck portion. Type injection device.

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