JPH07205232A - Screw for injection molding machine - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a screw for an injection molding machine, which has a high kneading effect, improves the plasticization efficiency, and makes the molten state uniform. A screw 2 for an injection molding machine having a two-screw flight having a main flight 20 and a sub-flight 22, a notch having a helix angle larger than a helix angle of the main flight on the front side of the top of the main flight 20. 20A is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-thread flight screw having a main flight and a sub-flight, and a screw for an injection molding machine for injecting and molding a molten resin into a mold, which has a particularly high kneading effect. The present invention relates to a screw for an injection molding machine in which the molten state of the resin is made uniform by adding

[0002]

2. Description of the Related Art A conventional injection molding machine 100 is shown in FIGS. 3 and 4, respectively. It has a nozzle 3 at its tip and a cylindrical barrel 1 having a temperature control device on its outer circumference.
The barrel 1 is arranged so that the nozzle 3 faces the material injection port of the mold 4, and the screw 2 having the spiral main flight 20 on the outer peripheral surface of the screw body 2a is rotatable inside the barrel 1. And it is provided slidably in the axial direction. The screw 2 is divided into a supply zone FZ, a compression zone CZ, and a metering zone MZ, and branches off from the main flight 20 at the boundary between the supply zone FZ and the compression zone CZ and at the boundary between the compression zone CZ and the metering zone MZ. A sub-flight 22 that merges with the main flight 20 again is provided in the compression zone CZ. These flights are two flight screws consisting of a main flight 20 and a sub flight 22. In an injection molding machine equipped with such a two-thread flight screw, the resin fed from the feed hopper 10 into the barrel 1 is heated by the heater 11 from the inner wall surface of the barrel 1 while being rotated by a motor (not shown). Is transferred from the material supply zone FZ to the compression zone CZ. In the conventional two-flight flight screw, a plasticizing resin is formed between the pulling side of the main flight 20 and the sub-flight 22 to form a solid bed, and the groove depth of the screw groove gradually decreases in the compression zone, so that the compression action is gradually performed. receive. In this process, the resin between the pulling side of the main flight 20 and the sub flight 22 transfers heat from the inner wall surface of the barrel 1 by the heater 11 and the resin itself by the rotating action of the screw 2, and the resin and the barrel 1 or Due to frictional heat (shear energy) generated between the screw 2 and the screw 2, a molten melt film is formed on the inner wall surface of the barrel 1.
A melt pool is formed on the push side of the main flight 20 and the screw groove of the sub flight 22 after overcoming the sub flight 22. When the solid bed and a part of the melt pool melted are mixed here, heat generation due to shearing is reduced and the plasticizing ability is reduced.

[0003]

In such an injection molding machine 100, the resin fed into the barrel 1 is heated by the heater 11.
The heat given from the inner surface of the barrel 1 is transferred to the resin pellets, and the heat generated by the shearing heat of the resin pellets generated by the rotation of the screw 2 is transferred to the resin pellets. The closer to the top, the faster the melting, and the resin pellets in the screw groove space 21 between the main flight 20 and the main flight 20 have a relatively small amount of heat received, and the melting becomes slower accordingly.
On the other hand, the main flight 20 of the screw 2 is usually 15 ° to
It has a helix angle θ of 25 ° and is transported forward by the front side surface of the flight top. However, the resin whose viscosity has reached the molten state quickly and whose viscosity has become small and which is mainly in the screw groove space 21 There was a problem in terms of uniformity of the molten state of the resin in the tip nozzle 3 to transfer the resin having a relatively high viscosity without being melted by the main flight 20 having the same spiral angle θ. For screws that handle resins that require high kneading, in addition to the original screw flight part, a mixing zone (kneading zone)
However, there is a problem in that the length of the screw becomes longer, the equipment cost of the entire injection molding machine becomes higher, and the plasticizing ability is lowered. An object of the present invention is to solve the above-mentioned two problems at the same time, to provide a screw of an injection molding machine having a high kneading function, improving plasticization efficiency, and homogenizing a resin molten state. It is what

[0004]

In order to solve the above-mentioned problems, in the present invention, a main flight is spirally arranged around a screw main body which is provided in a barrel so as to be rotatable and axially slidable. In a screw for an injection molding machine, which has a secondary flight that is branched from the middle of the main flight and is spirally arranged between the main flights, a spiral having a helix angle larger than the helix angle of the flight on the front side of the top of the main flight. A plurality of corner cutouts were formed per circumference.

[0005]

In the present invention, among the two flight screws having the main flight and the sub-flight, the notch having a helix angle larger than the helix angle of the main flight is provided on the front side of the top of the main flight. Of the solid granular resin transferred in the screw groove space between the flight and the main flight adjacent to the downstream side, the resin close to the inner surface of the barrel is melted, and the screw groove space that gradually reduces the volume It is pushed out to the outside, apparently moving backward toward the upstream side of the slit between the top of the auxiliary flight and the inner surface of the barrel, crossing the auxiliary flight, and entering the screw groove space formed by the adjacent main and auxiliary flights. The molten liquid resin that enters the screw groove space becomes a swirling state in the vertical cross section of the screw groove space and kneading occurs. At this time, due to the notch having a helix angle larger than the helix angle of the main flight on the front side of the top of the main flight of the present invention, a large thrust in the reverse direction (resin flow direction) is received, and thus the swirling flow is large. It becomes a turbulent flow and receives a larger kneading effect, and the molten resin is made uniform. Therefore, in the present invention, the homogenization of the molten resin by the high kneading and the plasticization efficiency of the resin are improved.

[0006]

Embodiments of the present invention will be described in detail below with reference to the drawings. 1 to 2 relate to an embodiment of the present invention, FIG. 1 is a longitudinal sectional view of an essential part of an injection molding machine, and FIG. 2 is an enlarged longitudinal sectional view of an essential part of a screw flight. As shown in FIGS. 1 and 2, the screw 2 of the injection molding machine 100 includes a main flight 20 that is continuous over the entire length and a sub flight 22 that is partially formed. The main flight 20 is from the resin supply side. It comprises a constant material supply zone FZ as it goes in the direction of the plasticized resin discharge side, a compression zone CZ in which the flight height gradually decreases as it goes in the direction of the resin discharge side, and a fixed metering zone MZ. The sub-flight 22 is formed only in CZ. That is, the sub-flight 22
Has a start point at the boundary between the supply zone FZ and the compression zone CZ, and an end point at the boundary between the compression zone CZ and the metering zone MZ. At the start point, the main flight 20 branches off and the middle of one pitch of the main flight 20 is reached. At the end of the road, connect to main flight 20. In the present invention, a plurality of notches 20A having a helix angle θ _A larger than the helix angle θ are formed on the front side of the top of the main flight 20 having the helix angle θ per circumference. The height of the notch 20A of the main flight 20 may be the total flight height as shown in FIG. 2, or may be appropriately selected within the range of 1/3 to 2/3 of the total flight height. In this case, it is desirable that the notch 20A be shallower on the upstream side and have a greater depth on the downstream side.

The behavior of the resin flow in the injection molding machine 100 of the present invention having the screw 2 composed of the main flight 20 and the sub-flight 22 configured as described above will be described. The solid granular resin supplied into the barrel 1 is a screw groove space 21 between the main flight 20 and the main flight 20.
And is transferred by the thrust due to the rotation of the screw 2, and is supplied to the supply zone FZ, the compression zone CZ, the measuring zone M.
Move Z sequentially. During this time, heating is performed by frictional heat (shear energy) on the resin itself, the inner surface of the resin 1 and the inner surface of the barrel 1, or the contact surface between the resin and the screw 2 due to heating by the heater 11 wound on the outside of the barrel 1 and movement of the resin,
It gradually changes to the molten state. As shown in FIG. 2, the solid granular resin that has moved from the supply zone FZ to the compression zone CZ is located on the front side of the partitioned chamber 21A and the partitioned chamber 21B that are divided into the screw groove space 21 by the auxiliary flight 22. The diameter of the screw 2 is expanded and the sub-flight 22 is pushed into the compartment 21B as the compression zone CZ progresses.
The resin that is further compressed by the volume reduction of the compartment 21B accompanying the movement of the position and is heated to be in a semi-molten state near the inner surface of the barrel 1 and liquefied passes over the gap between the top of the sub-flight 22 and the inner surface of the barrel 1 and is adjacent It moves to the compartment 21A. At this time, the liquefied resin entering the compartment 21A swirls as shown in FIG. 2 within the longitudinal section of the compartment 21A, and kneading is effectively performed. _A notch 20A having a helix angle θ _A larger than the helix angle θ is provided on the front side of the top of the main flight 20 in the compression zone CZ of the present invention.
Since a large forward thrust is applied by the front side surface having the spiral angle θ _A , the liquid resin that has flowed back from the partition chamber 21B to the partition chamber 21A is in a violent turbulent state and the partition chamber 2
Inside 1A, a vigorous swirling flow accompanied by turbulent flow results in a highly kneaded state. In this way, the solid resin advancing in the compression zone CZ is sufficiently plasticized and uniformized in the molten state by the kneading action by heating and moving from the partition chamber 21B to the partition chamber 21A, and the solid resin is moved to the weighing zone. Be transferred.

[0008]

As described above, in the present invention, high kneading of resin, improvement of plasticization efficiency, and homogenization of molten state can be achieved, and a high-quality molded product can be obtained.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is an enlarged vertical cross-sectional view of a main part of a screw flight of the injection molding machine according to the embodiment of the present invention.

FIG. 3 is a vertical sectional view of a conventional injection molding machine.

FIG. 4 is an enlarged vertical sectional view of a main part of a screw flight of a conventional injection molding machine.

[Explanation of symbols]

1 barrel 2 screw 3 nozzle 4 mold 10 feed hopper 11 heater 20 main flight 20A notch 21 screw groove space 21A partitioned chamber (upstream side) 21B partitioned chamber (downstream side) 22 auxiliary flight 100 injection molding machine FZ supply zone CZ compression Zone MZ Weighing zone θ Spiral angle (main flight) θ _A Spiral angle (notch of main flight)

Claims (1)

[Claims] 1. A main flight is spirally arranged around a screw main body provided rotatably and axially slidably in a barrel, and is branched from the middle of the main flight to form a spiral between main flights. In a screw for an injection molding machine having sub-flights arranged in a line, a plurality of notched portions having a helix angle larger than a helix angle of the flight are formed on the front side of the top of the main flight per circumference. A screw for injection molding machine.