JPH0688296B2 - Injection molding machine screw - Google Patents

Description

TECHNICAL FIELD The present invention relates to a screw of an injection molding machine used for improving the kneading of a plasticizing resin.

(Prior Art) The shape of a screw of an injection molding machine (hereinafter, simply referred to as a screw) is one of the important factors that determine the plasticizing ability in the plasticizing process of an injection molding operation. Generally, a screw has a single thread, and the threads have a pitch at equal intervals. Then, the height of the thread changes smoothly from the high thread to the low thread between the high feed zone with constant thread height and the low metering zone with constant thread height. The compression zone is formed in the state where it does.

Therefore, the volume ratio per pitch of the feed zone and the compression zone is smaller in the compression zone, and when the resin material is sent from the feed zone to the compression zone as the screw rotates, the resin material is compressed in the compression zone. Compressed.
Then, the resin material is exothermic plasticized by the shearing action based on such compression and the heating from the outside, and the plasticized resin is sent in the direction of the metering zone.

(Problems to be Solved by the Invention) However, although the resin material is plasticized in the compression zone as described above, since the pitch of the screw threads is evenly spaced, the plasticized resin is in the layered state in the metering zone direction. Will be sent to. For this reason, the plasticizing resin may not be sufficiently kneaded, and the temperature of the plasticizing resin may not be uniform. In such a case, there is a problem that a product of stable quality cannot be obtained. Furthermore, when the resin material moves from the compression zone to the metering zone with a low screw thread, the feeding of the resin material is restricted, so a new screw structure is required to further improve the plasticizing ability and shorten the heat history. Was there.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention forms a first screw thread 3 in a feed zone A and a compression zone B of a screw 2 and a compression zone B.
And a second thread 4 having a pitch P different from the first thread 3 and larger than the pitch p of the first thread 3 is formed in the metering zone C, and the first thread in the compression zone B is formed.
The height of one of the thread 3 and the second thread 4 is set lower than the height of the other.

(Operation) Since the present invention is configured as described above, the feed zone A
The plasticized resin sent from the compression zone B to the compression zone B is compressed, and as the screw 2 rotates, the plasticized resin flows into between the higher threads of the first screw thread 3 and the second screw thread 4, and by the lower screw thread. While being split, the two streams are mixed with each other through the gap y between the low thread and the heating barrel 5. Therefore, since the plasticized resin is agitated,
The kneading of the plasticizing resin in the compression zone B can be improved.

Further, since the resin material is fed from the feed zone A of the thread 3 having a small pitch to the metering zone C of the thread 4 having a large pitch through the compression zone B, the feed amount per one rotation of the screw 2 is changed from the feed zone to the pitch. Compared to a screw in which even a metering zone is formed by a single screw thread with small equal intervals, the screw is increased, and the plasticizing ability is increased and the heat history is shortened.

(Example) Below, one Example of this invention is described in detail based on drawing. FIG. 1 shows a schematic configuration of the injection molding machine 1 of the present invention. In the present invention, the screw 2 of the injection molding machine 1 is
A first screw thread 3 and a second screw thread 4 different from the first screw thread 3 are provided. The first thread 3 is formed in the feed zone A and the compression zone B of the screw 2, while the second thread 4 is formed in the compression zone B and the metering zone C. That is, the screw 2 has the first screw thread 3 and the second screw thread 4 formed in the compression zone B, but the intersection portion of both screw threads 3 and 4 is not provided in the compression zone B.

The pitch p of the first screw thread 3 is the pitch of a normal screw, and if the outer diameter of the screw 2 is φD, then generally p ≦
φD. The pitch P of the second thread 4 is set larger than the pitch p of the first thread 3. Further, in the compression zone B, in other words, in the section in which both screw threads 3 and 4 of the screw 2 are mutually formed, the height of the second screw thread 4 is set lower than the height of the first screw thread 3 by the height y. There is. Note that y is equal to the gap between the second screw thread 4 and the inner diameter of the heating cylinder 5, as shown in FIGS. 2 to 4.

The outer diameter of the first screw thread 3 of the screw 2 and the outer diameter of the second screw thread 4 of the metering zone C are equal to the inner diameter of the heating cylinder 5. The outer diameter φd of the second thread 4 of the compression zone B is set to be larger than the outer diameter φD of the first thread 3 of the screw 2 by a height 2y (φD = φd + 2y). Furthermore, the first thread 3 is
The crest width t is set wider than the crest width T of the second screw thread 4 (t
> T).

The height of the second screw thread 4 is gradually increased from the vicinity of the end portion of the first screw thread 3, that is, the vicinity of the boundary between the compression zone B and the metering zone C, toward the cylinder head side. The screw 2 has an outer diameter φD including the second thread 4 in the metering zone C equal to the inner diameter of the heating cylinder 5. Also, the second screw thread 4,
A gap (= y) 6 shown in FIG. 4 is provided between the ends of the first screw thread 3 on the side of the metering zone C to prevent passage of the unplasticized resin. 7 is a hopper, 8 is a band heater, 9 is a screw head, 10 is a cylinder head, 11
Is a nozzle, 12 is a housing, and 13 is a nut.

Next, the operation will be described.

When the screw 2 rotates and the resin material stored in the hopper 7 is supplied to the screw 2 via the supply port of the heating cylinder 5,
The resin material is sent from the feed zone A to the compression zone B along the first screw thread 3. The resin material sent to the compression zone B is compressed and is exothermic plasticized by the shearing action based on the compression and the heating from the outside such as the heating cylinder 5, and the plasticized resin is sent in the direction of the metering zone C.

Further, since the first thread 3 has the thread width t set to be wider than the thread width T of the second thread 4, the contact area between the heating cylinder 5 and the first thread 3 is the heating cylinder 5 and the second thread 3. The contact area of the heating cylinder 5 with respect to the first thread 3 is larger than the contact area with the thread 4,
It is better than the same heat conduction for the threads 4. As a result, the resin material sent to the compression zone B is favorably plasticized.

In the compression zone B, this plasticized resin flows in between the higher threads, that is, between the first threads 3 and 3 as the screw 2 rotates, and the lower threads, that is, the second threads. While being split by 4, the two streams are mixed with each other through the gap y between the second screw thread 4 and the heating cylinder 5. Therefore, since the plasticized resin is agitated, the kneading of the plasticized resin in the compression zone B can be improved. After that, the plasticized resin is sent to the metering zone C and extruded from the nozzle 11.

At this time, in the plasticized resin sent to the metering zone C, the pitch T of the second thread 4 is the pitch t of the first thread 3.
Since it is larger, the feed amount of the resin material per unit rotation of the screw 2 is larger than the feed amount by the first screw thread 3. Therefore, the extrusion ability of the plasticizing resin in the metering zone C, that is, the plasticizing ability is increased. Further, since the second thread 4 defines the thread width T to be narrower than the thread width t of the first thread 3, the second thread 4 has the screw 2
It is possible to reduce the torque load on the driving device (not shown) during the operation of.

In this embodiment, the height of the second screw thread 4 is set to the first
Although the height is set lower than the height of the screw thread 3, the present invention is not limited to this, and the height of the first screw thread 3 may be set lower than that of the second screw thread.

(Effects of the Invention) Since the present invention is configured as described above, the plasticized resin in the layer state sent to the compression zone and plasticized, the first screw thread and the second screw thread are generated as the screw rotates.
The layer state of the plasticized resin is disturbed by the screw threads, and the plasticized resin in the compression zone can be well kneaded. Furthermore, since the plasticized resin is fed from the first thread having a small pitch to the second thread having a large pitch,
The feed amount of the plasticizing resin per unit rotation of the screw is increased, so that the plasticizing ability is improved and the heat history time is shortened. As a result, a product of good quality can be easily obtained from the injection molding machine, the quality and accuracy of the product are improved, and the work efficiency and productivity are improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main part configuration of an embodiment of the present invention,
2 is a sectional view showing a part of the screw shown in FIG. 1, FIG. 3 is a sectional view taken along line III-III shown in FIG. 2,
FIG. 4 is a sectional view taken along the line IV-IV shown in FIG. 1 …… Injection molding machine 2 …… Screw 3 …… First screw thread 4 …… Second screw thread A …… Feed zone B …… Compression zone C …… Metering zone p …… First screw thread pitch P ...... Second thread pitch

Claims (1)

[Claims] 1. A second screw having a first thread formed in the feed zone and the compression zone, and having a pitch different from the first thread and larger than the pitch of the first thread in the compression zone and the metering zone. A screw of an injection molding machine, wherein a screw is formed, and the height of one of the first screw thread and the second screw screw in the compression zone is set lower than the height of the other screw.