JP6888483B2 - Screw for injection molding machine and injection molding method - Google Patents

Description

The present invention relates to a screw for an injection molding machine without a check ring, which is used for injection molding, and an injection molding method using the screw.

First, a weighing process for plasticizing (melting) the molten resin for one molding cycle in the injection apparatus of the injection molding machine will be described. As shown in FIG. 1, in the in-line screw type injection device 1, the screw 16 rotatably arranged in the heating barrel 15 is rotated by a measuring drive mechanism such as a servomotor (not shown) to rearward the screw 16 ( The pellet-shaped (granular) resin material 14a supplied into the heating barrel 15 from the material supply unit 14 such as the hopper (right side of FIG. 1) is formed so as to project onto the outer peripheral surface of the screw 16 and the outer peripheral surface of the screw 16. The screw flows forward (left side in FIG. 1) through the resin flow path 10 continuously formed between the spiral flight 16a and the inner peripheral surface of the heating barrel 15. During that time, heating and plasticization are performed by the heat energy from the heating means 15a arranged on the outer peripheral surface of the heating barrel 15 and the shear energy generated when the rotating flight 16 and the resin material 14a come into contact with each other or when the resin materials 14a come into contact with each other. (Melted state). Note that FIG. 1 shows the start of the weighing process of the in-line screw type injection device 1, and the screw 16 is at the weighing start position (injection completion position).

The resin material 14a flows in front of the screw 16, and plasticization (melting) proceeds as the heat receiving distance and the heat receiving time in the resin flow path 10 increase. Then, when it passes through the check ring 18 in front of the screw 16, it is almost completely plasticized and reaches the space (reservoir 15b) in front of the screw head 17 at the tip of the screw 16. In the weighing step, the injection nozzle 13 in front of the heating barrel 15 is pressed by a sprue bush of a mold (not shown), and the resin cutoff / opening (not shown) arranged on either the injection nozzle 13 or the mold is opened. Since the storage portion 15b forms a closed space due to the shutoff of the switching valve or the resin at the time of the previous injection filling that has already been cooled and solidified (gate sealed) in the cold runner, the plasticized resin material 14a (molten resin). ) Can be stored in the storage unit 15b.

Here, the check ring 18 is a check ring 18 and is a hollow cylindrical (ring-shaped) valve body arranged coaxially with the screw 16 so as to be movable by a predetermined amount in the longitudinal direction of the screw 16. The check ring 18 itself is not provided with a drive source for moving the check ring 18 in the longitudinal direction with respect to the screw 16, and the flow pressure of the resin material 14a for flowing the resin flow path 10 in front of the screw 16 during the weighing process causes the check ring 18 itself to flow. By pressing the check ring 18 forward of the screw 16 and moving it to the advance limit thereof, the resin flow path 10 is maintained in an open state.

On the other hand, in the in-line screw type injection device 1, not only the screw 16 can be rotated, but also the screw 16 can be moved forward and backward at a predetermined speed and pressure in the longitudinal direction by an injection drive mechanism (not shown) for injection filling. .. The screw 16 is plasticized in the resin flow path 10 by applying a pressure (back pressure) in the forward direction (left side in FIG. 1) by the injection drive mechanism and at the same time rotating the screw 16 at a predetermined speed by the weighing drive mechanism. The resin material 14a can be continuously stored in the storage unit 15b while maintaining a pressure substantially the same as the back pressure. As a result, as shown in FIG. 2, the screw 16 retracts while being rotated. Even during the retracting operation of the screw 16, the pressure of the resin material 14a in the storage portion 15b in front of the check ring 18 and the pressure of the resin material 14a in the resin flow path 10 behind are substantially the same pressure (≈ back pressure). Therefore, the check ring 18 stays at the forward limit position of the screw 16 and the resin flow path 10 continues to be open. Note that FIG. 2 shows the time when the weighing process of the in-line screw type injection device 1 is completed, and the screw 16 is at the measurement completion position (injection start position).

Due to the plasticization / weighing process performed in the heating barrel 15 of the in-line screw type injection device 1, the entire length of the screw 16 is extended together with the shape and inner diameter of each part of the heating barrel 15. The specifications of the screw 16 (cross-sectional shape, outer diameter, etc. of each part) and the specifications of the flight 16a (flight outer diameter, pitch, cross-sectional shape, etc.) so that the plasticizing / weighing process of the resin material to be used can be suitably performed. It is designed. Generally, the total length of the screw 16 from the material supply unit 14 behind the screw 16 (right side in FIG. 1) to the check ring 18 side (left side in FIG. 1) of the screw head 17 is determined according to the required function. It is designed for each part called a feed zone (supply part), a compression zone (compression part), and a metering zone (measuring part) (neither zone is shown). Further, the temperature of each part of the injection nozzle 13 and the heating barrel 15 corresponding to the feed zone, the compression zone and the metering zone, or each part is set by the heating means 15a arranged in the longitudinal direction of the outer circumference of the heating barrel 15. Further, the temperature of each divided portion divided in the longitudinal direction is appropriately controlled.

Here, the injection drive mechanism is provided with a measuring means for measuring the position of the screw 16 in the heating barrel 15 in the longitudinal direction, and the screw 16 has a preset position (weighing completion position / injection start position). ), It is determined that the weighing process is completed, and the rotation of the screw 16 and the supply of the resin material 14a to the material supply unit 14 are stopped. Then, by advancing the screw 16 at a predetermined speed (injection speed) by the injection drive mechanism, the resin material 14a of the storage portion 15b can be injected and filled into the mold cavity in the mold.

At the start of injection filling, the pressure of the resin material 14a in the storage portion 15b in front of the check ring 18 and the pressure of the resin material 14a in the resin flow path 10 behind the check ring 18 are substantially the same pressure (≈ back pressure). Therefore, the check ring 18 cannot follow the forward movement of the screw 16. On the other hand, due to the forward movement of the screw 16, the closing seal surface (not shown) of the resin flow path 10 formed at the retractable limit position of the check ring 18 on the screw 16 advances and is formed on the rear end surface of the check ring 18. The resin flow path 10 is blocked because it comes into contact with the sealing surface (not shown). Further, after the resin flow path 10 is closed, the pressure of the resin material 14a in the storage portion 15b rises sharply with the forward movement of the screw 16, and the check ring 18 is moved backward of the screw 16 during the forward movement of the screw 16. Press. Therefore, during the forward operation of the screw 16, the backflow of the resin material 14a in the storage portion 15b into the resin flow path 10 is prevented, and the resin material 14b can be injection-filled into the mold cavity.

However, as in Patent Document 1, injection molding may be difficult with a screw provided with a check ring. In Patent Document 1, the variation in the molten state of the resin material and the variation in the amount of the measured resin due to the special molding material and the combination thereof and the check ring are the reasons why the check ring cannot be adopted. On the other hand, not only when such a special resin material is used, but also injection molding using a resin material that generates corrosive gas such as vinyl-based polyvinyl chloride (PVC) and fluororesin (PTFE, PFA). Also in the case of, the check ring is provided in consideration of the corrosion of the check ring part and the resulting cleaning of the check ring part by opening the tip of the heating barrel, or the high frequency of replacement of the check ring part. No screw is adopted.

Japanese Unexamined Patent Publication No. 2006-239975

On the other hand, even when a screw without a check ring is adopted, when the weighing process is completed and the injection filling process is started, the resin pressure of the molten resin in the storage portion rises sharply as the screw advances. .. In the case of the screw 16 provided with the check ring 18 as shown in FIGS. 1 and 2, this resin pressure pushes the check ring 18 to the rear side (right side of FIG. 2) of the screw 16 as described above. As described above, since it acts on the front surface of the check ring 18 (left side in FIG. 2), the backflow prevention function of the check ring 18 is made more reliable. At this time, since the check ring 18 is in a closed state, the resin pressure of the molten resin in the storage portion that has risen sharply thereafter does not propagate to the molten resin in the resin flow path 10 behind the check ring 18. ..

However, in the case of the screw 32 without a check ring as shown in FIG. 3A, this resin pressure is substantially equal to the metering zone in the resin flow path 20 communicating with the storage portion 30b in front of the screw 32. It propagates to the molten resin that has been plasticized (melted state). FIG. 3A is a diagram showing an outline of the screw 32 not provided with a check ring, in which left and right side views are arranged with respect to the central front view. The two-dot chain line in the side view shows the inner peripheral surface of the heating barrel (not shown). In order to make the figure easier to see, the distance between the outer peripheral surface of the flight 32a of the screw 32 and the inner peripheral surface of the heating barrel indicated by the alternate long and short dash line is drawn large.

Immediately after the start of the injection filling process, the resin pressure of the molten resin in the storage section 30b propagates only to the molten resin at the tip of the metering zone in the resin flow path 20 communicating with the storage section 30b. For example, the retention distribution of the molten resin from the front end 32b of the flight 32a of the screw 32 to the position of 1 pitch (1P) in the resin flow path 20 where the resin pressure first propagates is hatched in FIG. 3A. Shown. One pitch (1P) of the flight 32a of the screw 32 is a distance in the screw longitudinal direction of adjacent flights formed continuously on one circumference of the outer peripheral surface of the screw. The length of the metering zone in the total length of the screw varies from 1P to 5.5P depending on the resin material (screw specification) used in terms of the number of flight pitches, and may be outside this range. In the screw 32 without a check ring shown in FIG. 3A, the length of the metering zone is assumed to be 2P from the front end portion 32b of the flight 32a.

Since the direction in which the resin pressure propagates is instantaneously the longitudinal direction of the screw 32, even if it is 1P (one circumference of the outer peripheral surface), it is in the longitudinal direction of the front end portion 32b of the flight 32a and the screw 32. The overlapping portion is not hatched because the resin pressure propagates with a delay. The retention distribution of this molten resin is non-uniform as shown by hatching. Further, again, this hatching is a retention distribution of the molten resin in the resin flow path 20 in which the resin pressure of the molten resin that has risen sharply propagated in the storage portion 30b, and is a resin other than that shown in this hatching. It does not mean that there is no molten resin in the metering zone in the flow path 20.

Then, the pressing force F acting from the outer peripheral surface of the screw 32 toward the rotation axis, which is generated by propagating the resin pressure of the storage portion 30b to the molten resin in the metering zone in the resin flow path 20, is the resin flow. Since the resin pressure in the path 20 is proportional to the retention amount (retention area) of the propagated molten resin, it becomes non-uniform. Specifically, the pressing force F acting from the upper outer peripheral surface of the screw 32 having the largest amount of retention (retention area) of the molten resin to which the resin pressure has propagated in the resin flow path 20 toward the rotation axis of the screw 32. (F1) is the largest. Further, since the molten resin hardly stays in the vicinity of the front end portion 32b of the flight 32a, the pressing force F (F4) is the smallest. Here, the pressing force in the direction facing the pressing force F1 (acting from the lower outer peripheral surface of the screw 32 toward the rotation axis of the screw 32) is F3, and the pressing force in the direction facing the pressing force F4 (the left outer peripheral surface of the screw 32). Therefore, the pressing force (acting toward the rotation axis of the screw 32) is defined as F2, and the difference in the pressing force is shown by arrows having different sizes in FIG. 3 (b). F1> F2> F3> F4 in proportion to the retention amount (retention area) of the molten resin for one circumference of the outer peripheral surface of 32.

Due to the non-uniformity of the pressing force F immediately after the start of the injection filling process, the screw 32 is pressed downward in FIG. 3B due to the relationship between the opposing pressing forces F1 and F3, and similarly, the opposing pressing forces F2 and F4. 3 (b) is pressed to the right side due to the relationship of. Since the screw 32 is a cantilever support in which only the rear side of the screw is supported, it is pressed against the inner peripheral surface side of the heating barrel (not shown) in front of the screw 32, and the flight 32a and the inner peripheral surface of the heating barrel are pressed. Depending on the clearance, there is a problem that the flight 32a comes into contact with the inner peripheral surface of the heating barrel.

The present invention has been made in view of the above-mentioned problems, and the resin pressure of the molten resin in the storage portion, which increases with the forward operation of the screw during the injection filling step, is applied to the molten resin in the resin flow path. An injection molding machine without a check ring that can prevent the flight of the screw from coming into contact with the inner peripheral surface of the heating barrel due to the pressing force generated by propagation that acts from the outer peripheral surface of the screw toward the rotation axis. It is an object of the present invention to provide a plastic for use and an injection molding method using the screw.

The object of the present invention is to inject the molten resin stored in the storage portion in front of the heating barrel for accommodating the screw into the mold from the injection nozzle in front of the heating barrel by advancing the screw in the weighing process. In the injection molding machine screw without a check ring used in the injection filling process to be filled.
The molten resin in the resin flow path formed between the outer peripheral surface of the screw, the spiral flight formed so as to project to the outer peripheral surface of the screw, and the inner peripheral surface of the heating barrel, is described as described above. The pressing force acting from the outer peripheral surface of the screw toward the rotation axis, which is generated by propagating the resin pressure of the molten resin in the storage portion, which rises with the forward operation of the screw, is substantially uniform in the opposite direction. It is achieved by an injection molding machine screw characterized in that the flight is configured to be distributed.

As such a screw for an injection molding machine, the screw
A spiral main flight formed so that the flight projects on the outer peripheral surface of the screw, and a spiral main flight.
With a subfreight having the same specifications as the mainfreight,
It is preferable that the rear end portion is formed in the metering zone of the screw with the position where the subflight is 180 ° out of phase with the front end portion of the main flight as the front end portion.

Further, the above object of the present invention is an injection molding method using a screw for an injection molding machine without a check ring according to the present invention, and in the weighing step, the said screw in front of the heating barrel for accommodating the screw. In the injection filling step of advancing the screw and injecting and filling the molten resin stored in the storage portion into the mold from the injection nozzle in front of the heating barrel.
The molten resin in the resin flow path formed between the outer peripheral surface, the main flight and the subflight, and the inner peripheral surface of the heating barrel, and the molten resin in the storage portion by advancing the screw. resin pressure is generated by propagation that occurs, the outer peripheral surface pressing force acting towards the rotary axis from the screw, achieved by injection molding how to and characterized in that substantially uniformly distributed in the opposite direction Will be done.

The screw for an injection molding machine without a check ring according to the present invention has a spiral flight formed so as to project onto the outer peripheral surface of the screw, the outer peripheral surface of the screw, and the heating in the injection filling step. The resin pressure of the molten resin in the reservoir, which rises with the forward movement of the screw, propagates to the molten resin in the resin flow path formed between the inner peripheral surface of the barrel and the screw. Since the flight is configured so that the pressing force acting from the outer peripheral surface toward the rotation axis is distributed substantially uniformly in the opposite directions, the flight of the screw is formed on the inner peripheral surface of the heating barrel in the injection filling step. Can be prevented from coming into contact with.

On the other hand, the injection molding method using a screw for an injection molding machine without a check ring according to the present invention is performed in the injection filling step.
The storage that rises in the molten resin in the resin flow path formed between the outer peripheral surface, the main flight and the subflight, and the inner peripheral surface of the heating barrel as the screw advances. In the injection filling step, the pressing force generated by propagating the resin pressure of the molten resin in the portion and acting from the outer peripheral surface of the screw toward the rotation axis is distributed substantially uniformly in the opposite directions. It is possible to prevent the flight from coming into contact with the inner peripheral surface of the heating barrel.

It is schematic cross-sectional view which shows the start of the weighing process in the general injection apparatus which has a screw provided with a check ring. It is schematic cross-sectional view which shows the completion of the weighing process in the general injection apparatus which has a screw provided with a check ring. Schematic diagram showing the retention distribution of molten resin in which the resin pressure of the molten resin in the reservoir propagates in the resin flow path communicating with the reservoir immediately after the start of the injection filling process in an injection device having a screw without a check ring. (Front view and both side views), and is a schematic front view showing a pressing force F acting from the outer peripheral surface of the injection molding machine screw toward the rotation axis. In the injection device having a screw without a check ring according to the first embodiment of the present invention, the resin pressure of the molten resin in the storage portion propagates in the resin flow path communicating with the storage portion immediately after the start of the injection filling process. It is a schematic view (front view and both side view) which shows the retention distribution of the molten resin, and is a schematic front view which shows the pressing force F acting from the outer peripheral surface of the screw for an injection molding machine toward a rotation axis. From the state of FIG. 4, a schematic view showing the retention distribution of the molten resin to which the resin pressure of the molten resin in the reservoir has propagated when the propagation of the resin pressure of the molten resin in the reservoir further progresses in the resin flow path ( Front view and both side views).

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.

[First Embodiment]
A screw for an injection molding machine without a check ring and an injection molding method using the screw according to the first embodiment of the present invention will be described with reference to FIGS. 4 and 5.

First, a screw for an injection molding machine without a check ring according to the first embodiment of the present invention will be described. The difference from the screw 32 of the in-line screw injection device 1 described above with reference to FIG. 3 is that the sub-flight 42a is provided in addition to the flight 32a. In the following description, the flight 32a will be referred to as a main flight 32a, and this screw will be referred to as a screw 42. For other configurations, the same reference numerals as those of the in-line screw type injection device 1 described with reference to FIG. 3 shall be used.

The screw 42 is shown in FIG. FIG. 4A is a view showing an outline of the screw 42, in which left and right side views are arranged with respect to the central front view. The two-dot chain line in the side view shows the inner peripheral surface of the heating barrel (not shown). As shown in the right side view of FIG. 4A, the pitch of the main flight 32a of the screw 42 is 1P like the screw 32, and the length of the metering zone is 2P from the front end portion 32b. In order to make the figure easier to see, the distance between the outer peripheral surfaces of the main flight 32a and the subflight 42a of the screw 42 and the inner peripheral surface of the heating barrel indicated by the alternate long and short dash line is drawn large.

The sub flight 42a has the same specifications as the main flight 32a. The same specifications mean that the flight height, flight pitch, flight cross-sectional shape, and the like are the same as those of the main flight 32a. Further, as shown in FIG. 4A, the sub-flight 42a has the rear end portion 42c in the metering zone of the screw 42 with the front end portion 42b at a position shifted by 180 ° from the front end portion 32b of the main flight 32a. It is formed. Specifically, the rear end portion 42c is formed at a position 1P from the front end portion 42b of the subflight 42a, that is, a substantially intermediate position of the length of the metering zone from the front end portion 32b to 2P of the main flight 32a of the screw 42. ing.

As described above, when the weighing step is completed and the injection filling step is started, the resin pressure of the molten resin in the storage portion 30b rises sharply as the screw 42 advances. This resin pressure propagates to the molten resin in the resin flow path 20 in front of the screw 42, which communicates with the storage portion 30b, in which the metering zone is almost completely plasticized (melted state). Immediately after the start of the injection filling process, the resin pressure of the molten resin in the storage section 30b propagates only to the molten resin at the tip of the metering zone in the resin flow path 20 communicating with the storage section 30b. The retention distribution of the molten resin from the front end 32b of the main flight 32a of the screw 42 to the position of 1 pitch (1P) in the resin flow path 20 where the resin pressure first propagates is shown by hatching in FIG. 4A. .. As described above, this hatching is the retention distribution of the molten resin in the resin flow path 20 in which the resin pressure of the molten resin that has risen sharply is propagated in the storage portion 30b, and is other than that shown in this hatching. It does not mean that there is no molten resin in the resin flow path of.

As is clear when compared with FIG. 3A, the front end portion 42b of the main flight 32a is displaced by 180 ° from the front end portion 32b of the main flight 32a, and the subflight 42a is formed to shift the phase of the resin flow path 20. The width of the flow path in the direction orthogonal to the flow direction of the resin is approximately halved. In other words, in FIG. 4A, the resin flow path 20 which is 1P of the flight 32a of the screw 32 and is one circumference of the outer peripheral surface is substantially 0. The pitch is about half that of 5P, which is one round of the outer peripheral surface. The pressing force F acting from the outer peripheral surface of the screw 42 toward the rotation axis generated by propagating the resin pressure of the storage portion 30b to the molten resin in the metering zone in the resin flow path 20 is the resin flow path 20. As explained above, the retention amount (retention area) of the molten resin to which the resin pressure has propagated is proportional to the retention distribution of the molten resin, even if the retention distribution of the molten resin is non-uniform as shown by hatching. , The pressing force F itself becomes smaller than when there is no subflight 42a (FIG. 3A).

On the other hand, the pressing force (F4') generated in the vicinity of the front end portion 32b of the main flight 32a and the pressing force (F2') generated in the vicinity of the front end portion 42b of the sub flight 42a in the direction opposite to the pressing force (F4') are due to the molten resin. Since there is almost no retention, the pressing force F is small, and the specifications of both flights are the same, so that the values are substantially the same without causing a large difference. Further, a pressing force (F1') acting from the upper outer peripheral surface of the screw 42 toward the rotation axis of the screw 42 and a pressing force (F3') acting toward the rotation axis of the screw 42 from the lower outer peripheral surface of the screw 42. ') Is also large because the specifications of both flights with 180 ° different phases at the front end are the same, and the retention amount (retention area) of the molten resin to which the resin pressure has propagated in the resin flow path 20 is substantially the same. The values are almost the same without any difference. When this difference in pressing force is shown by arrows of different sizes in FIG. 4 (b), F1'is proportional to the amount of molten resin retained for one circumference of the outer peripheral surface of the screw 32 in the resin flow path 20. ≈F3'> F2'≈F4'. It goes without saying that the pressing forces F in the opposite directions other than F1'to F4'have substantially the same value.

As a result, the resin pressure of the molten resin in the storage portion 30b, which rises with the forward operation of the screw 42, propagates to the molten resin in the metering zone in the resin flow path 20, and is generated from the outer peripheral surface of the screw 42. The pressing force F acting toward the rotation axis can be distributed substantially uniformly in the opposite directions.

As the injection filling step progresses, the retention distribution of the molten resin in the metering zone in the resin flow path 20 through which the resin pressure of the molten resin in the storage portion 30b propagates is also expanded. The retention distribution of the molten resin for two circumferences of the outer peripheral surface of the screw 42 in the resin flow path 20 through which the resin pressure propagates is shown by hatching in FIG. As described above, this hatching is the retention distribution of the molten resin in the resin flow path 20 in which the resin pressure of the molten resin that has risen sharply is propagated in the storage portion 30b, and is other than that shown in this hatching. It does not mean that there is no molten resin in the metering zone in the resin flow path 20 of the above.

As shown in FIG. 5, as the injection filling step progresses, the retention distribution of the molten resin in the metering zone in the resin flow path 20 through which the resin pressure of the molten resin in the storage portion 30b propagates is expanded. It can be seen that the degree of non-uniformity of the retention distribution of the molten resin in the metering zone in the resin flow path 20 in which the resin pressure of the molten resin propagates is also reduced with respect to a). Therefore, the degree of non-uniformity (difference) of the pressing force F acting from the outer peripheral surface of the screw 42 toward the rotation axis gradually decreases, and the pressing force F is distributed substantially uniformly in the opposite directions.

In this way, in an injection molding machine screw that does not have a check ring, the pressing force that acts from the outer peripheral surface of the screw toward the rotation axis, which is generated by propagating the resin pressure of the molten resin in the storage portion, is in the opposite direction. The flight of the screw comes into contact with the inner peripheral surface of the heating barrel in the injection filling step because the flight is configured so as to be distributed substantially uniformly to the resin, and by the injection molding method using such a screw. Can be prevented.

In the first embodiment, as shown in FIG. 4A, the subflight 42a is the front end of the subflight 42a with the front end portion 42b at a position shifted by 180 ° from the front end portion 32b of the main flight 32a. It is assumed that the rear end portion 42c is formed at the position of the portion 42b to 1P, that is, the position of the front end portion 42b to 1P of the screw 42 (a substantially intermediate position of the length 2P of the metering zone of the screw 42). However, as described above, the non-uniformity of the pressing force F acting from the outer peripheral surface of the screw 42 toward the rotation axis, which is generated by propagating the resin pressure of the molten resin in the storage portion 30b, is caused by the injection filling step. Immediately after the start, the resin pressure of the molten resin in the storage section 30b propagates only to the molten resin at the tip of the metering zone in the resin flow path 20 communicating with the storage section 30b. It is larger than the state in which the process has progressed. Therefore, as described with reference to FIG. 4A, the rear end portion 42c of the subflight 42a is at least at a position 0.5P from the front end portion 42b of the subflight 42a, that is, the main flight 32a of the screw 42. Even if it is formed in front of the substantially intermediate position of the length of the metering zone of 2P from the front end portion 32b of the screw 42, the resin pressure of the molten resin in the storage portion 30b, which rises with the forward movement of the screw 42, propagates. The effect of distributing the generated pressing force F acting from the outer peripheral surface of the screw 42 toward the rotation axis substantially uniformly in the opposite direction can be expected.

On the other hand, depending on the resin material and molding conditions, the high resin pressure generated in the molten resin in the storage portion 30b at the start of the injection filling process and the pressure propagation speed at which the resin pressure propagates to the molten resin in the resin flow path of the screw 42. In order to ensure the above effect, the rear end portion 42c of the subflight 42a is positioned at 0.5P from the front end portion 42b of the subflight 42a, that is, the front end portion 42b to 0 of the screw 42. It is formed a little longer from the position of .5P, and is formed at the position of 1P from the front end portion 42b of the screw 42 (approximately the intermediate position of the length 2P of the metering zone of the screw 42) as in the first embodiment. Is more preferable.

However, it is not sufficient to form the position of the rear end portion 42c of the subflight 42a further rearward of the screw 42. By forming the position of the rear end portion 42c of the subflight 42a further rearward of the screw 42, that is, by lengthening the formation range of the subflight 42a, in the resin flow path 20 in the range where the subflight 42a is formed. , The resin flow cross-sectional area is halved and the resin flow length is doubled. Therefore, if the rotation speed of the screw 42 is the same, there arises a problem that the weighing time increases and the heating time of the molten resin becomes long. In order to make the weighing time the same, it is necessary to increase the rotation speed of the screw 42, but in that case, melting in the resin flow path 20 formed only by the main flight 32a, in which the subflight 42a is not formed. Due to the problem that the flow speed of the resin increases, the problem that the energy consumption of the injection device increases, and the increase in shear energy due to the increase in the resin flow speed in the resin flow path 20 in which the subflight 42a is formed, Problems such as an increase in the amount of heat received by the molten resin occur.

On the other hand, the pressing force F acting from the outer peripheral surface of the screw 42 toward the rotation axis, which is generated by propagating the resin pressure of the molten resin in the storage portion 30b, which rises with the forward operation of the screw 42, is in the opposite direction. It is clear that the effect of substantially uniformly distributing the subflight 42a is obtained by forming the rear end portion 42c of the subflight 42a in a metering zone that goes around the outer peripheral surface of the screw 42 from half a circumference to one circumference. Further, in view of the fact that the state in which the resin flow path is filled with the molten resin is only in the metering zone, which allows the pressure propagation of the resin pressure of the molten resin to generate the pressing force F, the subflight 42a Even if the maximum formation range, that is, the rearmost end position of the rear end portion 42c of the screw 42 is behind the rear end position of the metering zone of the screw 42, the effect of distributing the pressing force F substantially uniformly in the opposite direction is obtained. There is no improvement.

Although the first embodiment has been described above with respect to the embodiment for carrying out the invention, the present invention is not limited to the above-described embodiment and does not deviate from the contents described in the claims. Needless to say, it can be implemented in various ways.

1 In-line screw type injection device, 10 resin flow path, 13 injection nozzle, 14 material supply part, 14a resin material, 15 heating barrel, 15a heating means, 15b storage part, 16 screw, 16a flight, 17 screw head, 18 check ring , 20 resin flow path, 30b reservoir, 32 screw, 32a flight (main flight), 32b front end, 42 screw, 42a subflight, 42b front end, 42c rear end

Claims (2)

In the weighing process, the molten resin stored in the storage portion in front of the heating barrel that houses the screw is used in the injection filling process in which the screw is advanced and injected and filled into the mold from the injection nozzle in front of the heating barrel. In the injection molding machine screw without a check ring
The molten resin in the resin flow path formed between the outer peripheral surface of the screw, the spiral flight formed so as to project to the outer peripheral surface of the screw, and the inner peripheral surface of the heating barrel, is described as described above. The pressing force acting from the outer peripheral surface of the screw toward the rotation axis, which is generated by propagating the resin pressure of the molten resin in the storage portion, which rises with the forward operation of the screw, is substantially uniform in the opposite direction. The flights are configured to be distributed ,
A spiral main flight formed so that the flight of the screw projects onto the outer peripheral surface of the screw, and
With a subfreight having the same specifications as the mainfreight,
A screw for an injection molding machine, characterized in that a rear end portion is formed in a metering zone of the screw with a position where the subflight is 180 ° out of phase with the front end portion of the main flight as a front end portion. In the weighing step, the molten resin stored in the storage portion in front of the heating barrel that houses the screw is injected and filled into the mold from the injection nozzle in front of the heating barrel by advancing the screw. In the filling process
The molten resin in the resin flow path formed between the outer peripheral surface, the main flight and the subflight, and the inner peripheral surface of the heating barrel, and the molten resin in the storage portion by advancing the screw. resin pressure is generated by propagation that occurs, the pressing force acting towards the rotational axis from the outer peripheral surface of the screw, it characterized thereby substantially uniformly distributed in the opposite direction,
The injection molding method according to claim 1, wherein the screw for an injection molding machine without a check ring is used.

Images