JP3516853B2 - Pre-plastic injection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-plastic injection device, and more particularly, to a pre-plastic injection device improved so as to eliminate stagnation of molten resin in an injection chamber.

[0002]

2. Description of the Related Art Injection devices of injection molding machines are roughly classified into in-line injection devices and pre-plastic injection devices. The in-line injection device melts a resin material with a screw, and the screw advances to inject the molten resin. In the pre-plastic injection device, a plasticizing part for melting resin and an injection part are provided independently, and the resin melted in the plasticizing part is sent to the injection chamber of the injection part and injected by the injection plunger. Has become.

Since the pre-plastic type injection device can change the diameter and stroke of the plunger separately from the screw, it has an advantage that the injection capacity and the injection pressure can be made larger than the in-line type injection device. On the other hand,
The in-line type, which allows the resin to be melted and injected coaxially in the heating cylinder, has less resin retention, whereas the pre-plastic type, which has a separate plasticizing part and injection part, inherently has a structure in which molten resin is retained. It is easy to occur. For this reason, various improvements have been added to the pre-plastic injection device in order to reduce the retention of the molten resin. FIG. 6 shows an injection part in a conventional pre-plastic injection device described in Japanese Patent Laid-Open No. 6-23796. The injection part 2 has an injection cylinder 10, and a plunger 12 is fitted into the injection cylinder 10. The injection chamber 14 is formed in the injection cylinder 10 in front of the plunger 12. The molten resin melted in the plasticizing section is supplied to the injection chamber 14 through the resin passage 15. An injection passage 16 is opened in front of the injection chamber 14. In the injection chamber 14, the molten resin is stored while the injection plunger 12 moves backward in the measuring process (FIG. 6B), and in the injection process, the injection plunger 12 moves forward to inject the molten resin stored in the injection chamber 14. Passage 1
6 through the injection nozzle (not shown) into the mold (FIG. 6A).

In such a pre-plastic injection device, the molten resin flows into the injection chamber 14 from the resin passage 15 as shown by the arrow in FIG. 6 (b). Therefore, the corner portion A on the side opposite to the opening of the resin passage 15 with the injection passage 16 in between.
The resin tends to stay. Even if the injection plunger 12 moves forward in the injection step of FIG. 6A, the resin in the corner portion A easily remains without being injected.

[0005]

Dynamically focusing on the molten resin in the injection chamber 14 in relation to the retention, the resin passage 16
Is opened in front of the injection chamber 14,
In terms of the time before and after the inflow of the resin accumulated in the above, the resin is introduced later as it is farther from the injection plunger 12. Therefore, when the injection plunger 12 moves forward, the molten resin that has entered the injection chamber 14 later is first injected into the mold.

The homogeneity of the molten resin in injection molding includes
It is known that the history of the molten resin from plasticization to injection (hereinafter referred to as heat history) has an effect. In order to always inject a homogeneous molten resin in each injection step, it is necessary that the entire molten resin accumulated in the injection chamber 14 has the same thermal history and the same heat history.

However, as described above, the injection chamber 14 is installed later.
The new molten resin entering is injected first (that is, the thermal history of the resin in this part is small), and the oldest molten resin is injected last (the thermal history of this part is large). In this way, the molten resin whose thermal history is always varied is injected.

[0008] This variation in heat history also means that the longer the heat history is, the longer the resin stays in the injection chamber 14. That is, the distribution of thermal history is such that the molten resin is inherently likely to stay.

Further, in the injection process, it is necessary to separately provide a backflow preventing mechanism such as a check valve so that the molten resin does not flow back from the resin passage 15 to the plasticizing portion (not shown).

Therefore, an object of the present invention is to solve the problems of the above-mentioned prior art and to make it possible to inject from the old molten resin which has first entered the injection chamber first so that the heat history becomes uniform as a whole. Another object of the present invention is to provide a pre-plastic injection device that prevents molten resin from staying in the injection chamber and at the same time simplifies backflow prevention to the plasticizing part.

[0011]

In order to achieve the above object, the present invention provides a plasticizing portion for rotating a screw in a heating cylinder to plasticize a resin raw material, and an injection plunger in front of an injection cylinder in an injection cylinder. In a pre-plastic injection device, in which a molten resin sent from a plasticizing unit is stored in an injection chamber to be formed, and an injection unit for injecting this molten resin from a nozzle into a mold by advancing the injection plunger is provided independently, A resin supply port of a resin supply passage for supplying molten resin from the plasticizing section to the injection cylinder is provided so as to open to a side portion of the injection cylinder, and a long groove communicating with the resin supply port is formed on the inner circumference of the injection cylinder. Is formed in an axial direction in the portion, communicates with the long groove from the completion of the injection process to the completion of the measurement process when the injection plunger is at a predetermined rotation angle position, and melts the molten resin in the injection chamber. Provided a passage hole leading to the injection plunger, the tip of the injection plunger, the molten resin Tama
When the injection chamber is formed and the weighing process is completed after the injection process is completed
In the position where it is possible for the long grooves to overlap
A cylindrical part having a passage hole is provided and
The nozzle is provided with a shaft part that is slidably fitted in, and the injection hole is rotated so that the phase of the passage hole and the long groove coincide with each other at the time of measurement, and the phase shifts at the time of injection. It is characterized in that a plunger rotation device for changing the rotation angle position is provided.

According to the present invention, during the measuring process, the molten resin is accumulated in the injection chamber as the injection plunger retracts while the long groove and the passage hole are in phase with each other and the communication state is maintained. . Since the position of the passage hole will also retreat,
The thermal history of the molten resin accumulated in the injection chamber gradually decreases from the nozzle side toward the injection plunger side. Therefore, when the injection plunger advances, the molten resin that first enters the injection chamber is injected first.

When the rotation angle position of the injection plunger is changed by the plunger rotating device at the start of the injection process, the long groove and the passage hole are out of phase with each other.
Since it is closed, the backflow of the molten resin can be prevented.

According to a preferred embodiment of the present invention, an injection chamber for accommodating the molten resin is formed at the tip of the injection plunger, and the long grooves can be overlapped with each other from the completion of the injection process to the completion of the measuring process. A cylindrical portion having the passage hole is provided, and a shaft portion slidably fitted in the cylindrical portion is provided in the nozzle. Further, it is preferable that the passage hole is formed at a position corresponding to a front end portion of the long groove at the start of the measuring process and at a rear end portion of the cylindrical portion.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a pre-plastic injection device according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a view showing a vertical section of a pre-plastic injection device according to this embodiment. Reference numeral 20 denotes a plasticizing portion for plasticizing the resin raw material, and 22 denotes an injection portion for injecting the molten resin into a mold (not shown).

A screw 24 is inserted inside the heating cylinder 23 of the plasticizing section 20. The screw 24 rotates to plasticize the resin raw material that is fed into the heating cylinder 23 from a hopper (not shown). The connecting portion 23 a at the tip of the heating cylinder 23 is joined to the side surface of the injection cylinder 25 included in the injection unit 22. A resin supply passage 26 is formed inside the connecting portion between the plasticizing portion 20 and the injection portion 22. This resin supply passage 26 is
A resin supply port 26a is opened at a side portion of the injection cylinder 25 through a ring-shaped groove 27, and the molten resin is screwed into the screw 24.
With the rotation of the resin supply port 2 of the resin supply passage 26
It is adapted to be supplied into the cylinder 25 through 6a.

As described above, the structure in which the molten resin is supplied to the injection cylinder 25 from the side thereof improves the accessibility between the plasticizing part 20 and the mold and makes the structure less likely to interfere. Next, the configuration of the injection unit 22 will be described. The injection cylinder 25 of the injection unit 22 includes an injection plunger 28.
Has been inserted freely. This injection plunger 28
Uses an injection servo motor (not shown) as a drive source,
The injection cylinder 25 is moved forward and backward. The rotational force of the servo motor is transmitted to the ball screw shaft 29 via a transmission mechanism (not shown) including a timing belt and a pulley. A nut 30 is screwed onto the ball screw shaft 29,
The rotational movement of the ball screw shaft 29 is converted into the linear movement of the injection plunger 28 via the nut 30. The nut 30 is connected to the end of the rod portion 33 of the injection plunger 28 via the coupling 31 and the load cell 32. In the measuring process, the back pressure applied to the retracting injection plunger 28 is applied to the load cell 32.
The rotation torque of the servomotor is controlled so that the back pressure becomes a set value.

At the front end of the injection cylinder 25, the nozzle 3
4 is attached so that the nozzle 34 comes into contact with a mold (not shown) when the entire injection unit 22 advances due to the nozzle touch. On the injection plunger 28 side of the nozzle 34, a shaft portion 35 has an integral structure and extends coaxially. The injection passage 36 of the nozzle 34 is formed so as to concentrically pass through the shaft portion 35. The shaft portion 35 has an outer diameter smaller than the inner diameter of the injection cylinder 25, and has a predetermined size between the inner peripheral surface of the injection cylinder 25 and the outer peripheral surface of the shaft portion 35 when inserted into the injection cylinder 25. Gaps are formed.

Next, FIG. 4 shows a state in which the injection plunger 28 is fitted in the shaft portion 35 of the nozzle 34. A cylindrical portion 40 having the same diameter is integrally formed at the front end portion of the injection plunger 28. The cylindrical portion 40 forms an injection chamber 42 in which the molten resin sent from the plasticizing portion 20 is stored. The outer diameter of the cylindrical portion 40 corresponds to the inner diameter of the injection cylinder 25, and the inner diameter thereof corresponds to the outer diameter of the shaft portion 35 of the nozzle 34. Therefore, the cylindrical portion 4
The injection plunger 28 including 0 slides in the injection cylinder 25, and the shaft portion 35 is slidably fitted therein.

Next, the passage for guiding the molten resin to the injection chamber 42 will be described. A plurality of long grooves 44 are formed on the inner peripheral portion of the injection cylinder 25. In this embodiment, two long grooves 44 are formed symmetrically with respect to the center of the injection cylinder 25. The long groove 44 is a groove having a predetermined length along the axial direction of the injection cylinder 25, and the length thereof substantially corresponds to the stroke of the injection plunger 28. The rear end portion of the long groove 44 is provided at a position where it overlaps with the resin supply port 26a.

On the other hand, in the injection plunger 28, two passage holes 45 are provided at the rear end of the cylindrical portion 40 symmetrically with respect to the center. The passage holes 45 are shown in FIG.
At the rotation angle position of the injection plunger 28 as shown in (a), it overlaps with the long groove 44 and communicates. On the other hand, when the rotation angle position is other than this (FIG. 5B), the long groove 44 and the passage hole 45 are out of phase with each other, and the passage hole 45 is in the injection cylinder 2
It is adapted to be closed by the inner peripheral surface of 5.

When the phases are in phase, the passage hole 45 is
As shown in FIG. 1, the injection plunger 28 coincides with and overlaps with the front end portion of the long groove 44 when the injection step 28 is at the injection process completion position. In addition, as shown in FIG. 2, when the injection plunger 28 is at the measuring step completion position, the passage hole 45 coincides with the rear end portion of the long groove 44 and overlaps with the rear end portion. Therefore, during the measuring process, the resin supply passage 2
The molten resin introduced from 6 is guided through the long groove 44 and the passage hole 45 as a flow path, and is guided to the injection chamber 42 inside the cylindrical portion 40.

In this embodiment, a taper surface 46 is formed on the end surface of the shaft portion 35 that defines the injection chamber 42, the diameter of the taper surface 46 decreasing toward the discharge passage 36. A conical portion 47 is formed on the. As a result, the injection chamber 42 is designed to have a shape that prevents molten resin from staying therein.

Next, the injection plunger 28 is rotated to
A plunger rotating device 50 for aligning or shifting the phase of the passage hole 45 and the long groove 44 will be described. The plunger rotating device 50 includes a servo motor 52.
Is used as the rotation drive source. Servo motor 52
Drive-side pulley 53 attached to the output shaft of the driven-side pulley 54 and driven-side pulley 54 attached to the rod portion 33 of the injection plunger 28 and supported by a bearing 57.
The timing belt 55 is wound between the servomotor 52 and the timing belt 55.
Is transmitted to the injection plunger 28. Since the injection plunger 28 moves forward and backward, the rod portion 33
A spline 56 is formed on the outer periphery of the pulley in the axial direction, and the boss portion of the pulley 54 engages with the spline 56. By coupling the boss portion of the pulley 54 to the rod portion 33 via the spline 56, the rod portion 33 can be moved in the axial direction together with the transmission of torque.

The plunger rotating device 50 according to this embodiment is configured to transmit the rotational force of the servo motor 52 to the injection plunger 28 by using the winding transmission mechanism. The transmission mechanism is a link mechanism. You may use it. Further, a rotation system in which an air cylinder or a hydraulic cylinder is used as a drive source and transmission is performed by a link mechanism or the like may be used.

The pre-plastic injection device according to this embodiment is
It is configured as described above, and its operation will be described next. The injection plunger 28 is at the position shown in FIG. 1, and the measuring process is started when the injection process is completed. The molten resin plasticized by the screw 24 rotating in the plasticizing section 20 passes through the resin supply passage 26, flows from the resin supply port 26a through the long groove 44 and the passage hole 45, and is injected into the injection chamber 42.
Will be introduced to.

During the measuring process, while the long groove 44 and the passage hole 45 are in phase with each other and the communicating state is maintained, the injection plunger 28 retreats while applying back pressure to the molten resin. As it moves backward, it is accumulated in the injection chamber 42 and weighing is performed.

FIG. 2 shows a state in which the injection plunger 28 is retracted to the set measurement completion position. From FIG. 1 to FIG. 2, the molten resin is introduced into the injection chamber 42 through the passage hole 45 whose position moves backward as the injection plunger 28 moves backward. As a result of the movement of the passage hole 45, the thermal history of the molten resin accumulated in the injection chamber 42 gradually decreases from the nozzle 34 side toward the injection plunger 28 side.

When the injection plunger 28 has retracted to the metering completion position, the rotation of the screw 24 is stopped and the metering process is completed. FIG. 3 shows a state when the injection process is started. Simultaneously with the completion of the weighing process, the servomotor 52 of the injection plunger 28 is activated, and the injection plunger 28 moves 90%.
Rotate once. By changing the rotational angle position of the injection plunger 28, the phase between the long groove 44 and the passage hole 45 is shifted, and the passage hole 45 is closed. After that, the communication between the injection chamber 42 and the resin passage including the long groove 44 and the resin supply passage 26 is cut off so that the molten resin in the injection chamber 42 does not flow backward.
When the injection plunger 28 moves forward, the molten resin in the injection chamber 42 is injected into the mold (not shown) that is in contact with the nozzle 34 first from the resin having a large thermal history, that is, the resin that has entered first. It Therefore, the resin having a large heat history is unlikely to stay in the injection chamber 42.

As described above, the molten resin that has entered the injection chamber 42 first is injected first, and the molten resin that enters the injection chamber 42 later is injected later. There is no variation in the thermal history until the injection as a whole. That is, a part of the molten resin does not stay for a long time, there is no variation in the time accumulated in the injection chamber 42, and it is possible to inject the molten resin having uniform temperature and other conditions as a whole into the mold. it can.

Further, the backflow of the molten resin can be easily and surely achieved simply by shifting the phase between the long groove 44 and the passage hole 45.

[0032]

As is apparent from the above description, according to the present invention, the old molten resin that has first entered the injection chamber is injected first into the mold so that the heat history becomes uniform as a whole. It is possible to prevent the molten resin from staying in the injection chamber and to prevent the backflow to the plasticized portion easily by shifting the phases of the long groove and the passage hole.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of a pre-plastic injection device according to the present invention, showing a state in which an injection plunger is at a weighing process starting position.

FIG. 2 is a cross-sectional view of an embodiment of a pre-plastic injection device according to the present invention, showing a state in which the injection plunger is at the measurement process completion position.

FIG. 3 shows a state after the injection plunger has rotated at the measurement process completion position.

FIG. 4 is a sectional view showing a combination of an injection plunger and a nozzle.

FIG. 5 is a cross-sectional view showing a relative rotation angle position between a long groove of the injection cylinder and a passage hole of the injection plunger.

FIG. 6 is a cross-sectional view showing an injection chamber of a conventional pre-plastic injection device.

[Explanation of symbols]

20 Plasticizing part 22 Injection part 23 Heating cylinder 24 screws 25 injection cylinder 26 Resin supply passage 26a Resin supply port 28 Injection Plunger 29 Ball screw shaft 30 nuts 34 nozzles 35 Shaft 40 cylindrical part 42 injection chamber 44 long groove 45 passage hole 50 Plunger rotating device 56 splines

Claims (2)

(57) [Claims] 1. A plasticizing section for plasticizing a resin material by rotating a screw in a heating cylinder, and a molten resin sent from the plasticizing section in an injection chamber formed in front of an injection plunger in an injection cylinder, In a pre-plastic injection device having an injection part for injecting this molten resin from a nozzle into a mold by advancing the injection plunger independently, a resin supply passage for supplying the molten resin from the plasticizing part to the injection cylinder. The resin supply port of the injection cylinder is opened to the side of the injection cylinder, and a long groove communicating with the resin supply port is axially formed in the inner peripheral part of the injection cylinder, and the injection plunger has a predetermined rotation angle position. emitted from step completed the injection chamber communicating with the longitudinal groove over time metering process completes the passage hole for guiding the molten resin provided in the injection plunger, the injection plug when in The tip of Ja, injection of the molten resin is accumulated
Form the chamber and pass from the completion of the injection process to the completion of the weighing process
The passage hole at a position where the long grooves can overlap.
A cylindrical portion having a
A nozzle is provided with a shaft part that fits inside the nozzle, the passage hole and the long groove are in phase during measurement, and the injection plunger is rotated so that the phase is shifted during injection. A pre-plaster type injection device comprising a plunger rotating device for changing the angular position. 2. The pre-plastic type according to claim 1 , wherein the passage hole is formed at a position corresponding to a front end portion of the long groove at the start of the weighing process and at a rear end portion of the cylindrical portion. Injection device.