JP2003103575A - Moving device for pressurized fluid introduction nozzle, pressurized fluid introduction device, mold assembly and injection molding method - Google Patents

Abstract

(57) [Problem] To provide a mold assembly incorporating a moving device for a pressurized fluid introduction nozzle having a simple structure. A mold assembly includes: (A) a mold having a cavity; and a molten resin injection portion for injecting a molten thermoplastic resin into the cavity; Pressurized fluid introduction nozzle 21 having a portion 23,
And (C) a rear end portion of the pressurized fluid introduction nozzle 21 is attached, and a moving device 30 for reciprocating the pressurized fluid introduction nozzle 21 is provided, and the molten thermoplastic resin injected into the cavity 13 is provided. This is a mold assembly for forming an injection molded product having a hollow portion by introducing a pressurized fluid into a resin, and a moving device 30 includes a piezoelectric element 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving device for a pressurized fluid introducing nozzle, a pressurized fluid introducing device, a mold assembly and an injection molding method, and more specifically, to an injection molding device. A pressurized fluid introducing device for introducing a pressurized fluid into a molten thermoplastic resin injected into a cavity of a mold to form an injection-molded article having a hollow portion, and configuring the pressurized fluid introducing device The present invention relates to a moving device for a pressurized fluid introducing nozzle, a mold assembly incorporating the pressurized fluid introducing device, and an injection molding method using the mold assembly.

[0002]

2. Description of the Related Art An injection molding apparatus for injection molding a molten thermoplastic resin in order to mold an injection molded article having excellent appearance characteristics without sink marks or warps is disclosed in, for example, JP-A-64-
It is disclosed in Japanese Patent No. 14012 and Japanese Patent Laid-Open No. 6-91684. In the injection molding apparatus disclosed in these patent publications, the gas injection nozzle is configured to reciprocate. For example, in an injection molding method using an injection molding device disclosed in Japanese Patent Laid-Open No. 64-14012, as shown in FIG. 1 of this patent publication, a molten plastic material 19 is molded into a mold cavity. 1
Inject into 3. Then, a pressurized gas is injected into the plastic material 19 injected into the mold cavity 13,
A gas-containing hollow portion 25 is formed in the plastic material 19. After that, the pressurized gas in the gas-containing hollow portion 25 is opened to the atmosphere before opening the mold.

In the configurations disclosed in these patent publications, the gas injection nozzle is positioned at the forward end,
Further, a moving means for holding the position of the forward end against the pressure of the molten resin injected into the cavity is provided. Further, in order to completely release the pressurized gas in the hollow portion formed inside the thermoplastic resin in the cavity into the atmosphere before opening the mold, the gas injection nozzle is moved to the reverse end by the operation of the moving means, The seal between the molded product in the cavity and the tip of the gas injection nozzle is broken.

[0004]

By the way, such a moving means requires an external high pressure source, for example, a high hydraulic pressure. Therefore, even when the above-mentioned injection molding is performed using the electric injection molding device, it is necessary to prepare a fluid pressure generation source, for example, a hydraulic pressure generation device, as the moving means, and the manufacturing cost of the entire injection molding device is reduced. There is a problem of increase. Also, in order to counter the high pressure of the molten thermoplastic resin injected into the cavity,
A large axial force is required for the moving means, and there is a problem that the moving means becomes large.

Therefore, it is an object of the present invention to provide a moving device for a pressurized fluid introducing nozzle having a simple structure, a pressurized fluid introducing device incorporating such a moving device, and a mold assembly incorporating the pressurized fluid introducing device. An object of the present invention is to provide a solid body and an injection molding method using such a mold assembly.

[0006]

A moving device for a pressurized fluid introducing nozzle of the present invention for achieving the above object is provided with a molten thermoplastic resin injected into a cavity provided in a mold. A moving device that reciprocates a pressurized fluid introduction nozzle having an opening at the tip for introducing a pressurized fluid to mold an injection-molded product having a hollow portion, characterized by comprising a piezoelectric element. And

The pressurized fluid introducing device of the present invention for achieving the above object is (A) a pressurized fluid introducing nozzle having an opening at the tip, and (B) after the pressurized fluid introducing nozzle. A moving device for reciprocating the pressurized fluid introduction nozzle, the end portion being attached to the pressurized fluid introduction nozzle, and introducing the pressurized fluid into the molten thermoplastic resin injected into the cavity provided in the mold. A pressurized fluid introducing device for molding an injection-molded article having a hollow portion, wherein the moving device includes a piezoelectric element.

A mold assembly of the present invention for achieving the above object is a mold having a cavity (A) and a molten resin injection portion for injecting a molten thermoplastic resin into the cavity, (B) ) A pressurized fluid introduction nozzle having an opening at the tip, and (C) a moving device to which a rear end of the pressurized fluid introduction nozzle is attached and which reciprocates the pressurized fluid introduction nozzle. A mold assembly for introducing a pressurized fluid into the molten thermoplastic resin injected into the cavity to mold an injection-molded article having a hollow portion,
The moving device is characterized by including a piezoelectric element.

The injection molding method of the present invention for achieving the above-mentioned object is (A) a mold having a cavity and a molten resin injection portion for injecting a molten thermoplastic resin into the cavity, (B) A pressurized fluid introducing nozzle having an opening at its tip and (C) a piezoelectric element, the rear end of the pressurized fluid introducing nozzle is attached, and a movement for reciprocating the pressurized fluid introducing nozzle. An injection molded product using a mold assembly for forming a injection molded product having a hollow part by introducing a pressurized fluid into the molten thermoplastic resin injected into the cavity. (A) after the mold is clamped, the pressurized fluid introducing nozzle is positioned at a predetermined position by the moving device, (b) the molten thermoplastic resin is injected into the cavity, and (c) the melting is performed. During injection of thermoplastic resin After the injection is completed, the pressurized fluid is introduced from the pressurized fluid introduction nozzle into the molten thermoplastic resin injected into the cavity, so that the molten thermoplastic resin injected into the cavity is hollow. Forming part, (d)
After the elapse of a certain time, the pressurized fluid introducing nozzle is retracted by the operation of the moving device to form a gap between the tip of the pressurized fluid introducing nozzle and the thermoplastic resin, and the pressure in the hollow portion is increased through the gap. It is characterized by comprising each step of releasing the pressurized fluid.

In the injection molding method of the present invention, after the mold is clamped, the tip of the pressurized fluid introducing nozzle is placed in the cavity in a state where the pressurized fluid introducing nozzle is positioned at the predetermined position by the operation of the moving device. While the pressurized fluid is being introduced from the pressurized fluid introduction nozzle into the molten thermoplastic resin that has been projected and has been injected into the cavity, the tip of the pressurized fluid introduction nozzle is brought to that position by the operation of the moving device. It can be configured to hold. Note that such a configuration is referred to as an injection molding method according to the first configuration for convenience.

Alternatively, in the injection molding method of the present invention, after the molten thermoplastic resin is injected into the cavity, it is added to the inside of the molten thermoplastic resin injected into the cavity from the pressurized fluid introducing nozzle. Before the pressurized fluid is introduced, the pressurized fluid introduction nozzle is advanced from the predetermined position by the operation of the moving device, the tip of the pressurized fluid introduction nozzle is projected into the cavity, and the molten material injected into the cavity is melted. While the pressurized fluid introducing nozzle is introducing the pressurized fluid into the thermoplastic resin, the tip of the pressurized fluid introducing nozzle can be held at that position by the operation of the moving device. It should be noted that such a configuration has a second
It is called an injection molding method according to the above configuration.

Alternatively, in the injection molding method of the present invention, after the hollow portion is formed in the molten thermoplastic resin injected into the cavity, the moving device is actuated before the predetermined time elapses. The pressure fluid introduction nozzle may be configured to be advanced from the predetermined position.
Note that such a configuration is referred to as an injection molding method according to the third configuration for convenience.

A moving device for the pressurized fluid introducing nozzle of the present invention, a pressurized fluid introducing device of the present invention, a mold assembly of the present invention,
Alternatively, in the injection molding method of the present invention including various configurations (hereinafter, these may be collectively referred to simply as the present invention), the piezoelectric element (also referred to as a piezoelectric element actuator) is a voltage applied thereto. At this time, it refers to an element (actuator) having an inverse piezoelectric effect that causes distortion proportional to the magnitude of an applied voltage, or an element (actuator) having an electrostriction effect that causes distortion proportional to the square of the applied voltage. Since the piezoelectric element may be exposed to a relatively high temperature, the piezoelectric element is set to PbZrO ₃ and Pb.
Lead zirconate titanate which is a solid solution of TiO ₃ [PZ
T, Pb (Zr _1-y , Ti _y ) O ₃ (where 0 <y <
1)], PL is a metal oxide obtained by adding La to PZT.
It is preferably composed of a lead zirconate titanate compound such as PZT which is a metal oxide obtained by adding Nb to ZT or PZT.

In the present invention including the above modes, the position of the pressurized fluid introducing nozzle can be controlled by making the voltage applied to the piezoelectric element variable. In this case, the voltage applied to the piezoelectric element can be, for example, 25 V to 5000 V. In a conventional moving device equipped with a hydraulic cylinder, while the pressurized fluid is being introduced into the molten thermoplastic resin injected into the cavity provided in the mold, it is normally applied only to the forward end or the reverse end. The pressure fluid introduction nozzle cannot be held. On the other hand, in the present invention, since the moving device provided with the piezoelectric element is used, easily and reliably holds the pressurized fluid introduction nozzle at a desired position, for example, between the forward end and the backward end, Alternatively, the pressurized fluid introduction nozzle can be moved during injection molding. The position of the pressurized fluid introduction nozzle can be controlled by changing the amount of electric charge supplied to the piezoelectric element.

In the present invention including the above-described various forms, the displacement amount of the piezoelectric element is measured, the deviation from the set displacement amount is fed back, and the voltage applied to the piezoelectric element (or the amount of charge supplied to the piezoelectric element). ) Can be controlled. The displacement amount of the piezoelectric element can be measured by, for example, a strain gauge attached to the piezoelectric element. Furthermore, the voltage applied to the piezoelectric element (or the amount of charge supplied to the piezoelectric element) based on the relationship between the voltage applied to the piezoelectric element (or the amount of charge supplied to the piezoelectric element) and the amount of displacement of the piezoelectric element measured in advance. ) Is determined.

In the present invention including the various forms described above,
The moving device may be configured to further include a displacement magnifying mechanism for magnifying the amount of displacement of the piezoelectric element. The displacement magnifying mechanism is preferably operated by hydraulic pressure. More specifically, the displacement magnifying mechanism includes, for example, a piston main body portion, a piston portion slidable inside the piston main body portion, and a plunger portion slidably arranged inside the tip end portion of the piston main body portion. And inside the piston body,
It can consist of oil filled in the space between the piston part and the plunger part. A piezoelectric element is attached to the piston part. The piston is slid by the displacement of the piezoelectric element. The rear end of the pressurized fluid introduction nozzle is attached to the front end of the plunger portion. Sectional area of the plunger cross-sectional area of the (D ₂₎ of the piston portion (D ₁₎
By making it smaller than
It can be enlarged by (D ₁ / D ₂ ) times.

In the present invention including the various modes and configurations described above, it is desirable that the moving distance of the pressurized fluid introduction nozzle is 10 μm or more and 5 mm or less. When the moving distance of the pressurized fluid introduction nozzle is less than 10 μm, it may be difficult to completely release the pressurized fluid in the hollow portion formed inside the thermoplastic resin in the cavity into the atmosphere before mold opening. is there. On the other hand, when the moving distance of the pressurized fluid introducing nozzle exceeds 5 mm, indentations become noticeable on the injection-molded product, which may cause a defective appearance of the injection-molded product.

In the present invention including the above-described various modes and configurations, the displacement amount of the piezoelectric element is the applied voltage 10 to the piezoelectric element.
Per 0 volt and per 1 mm of piezoelectric element length,
It is desirable that the thickness is 0.01 μm or more, preferably 0.1 μm or more, and more preferably 0.5 μm or more.

In the present invention including the above-described various modes and configurations, the proof stress of the piezoelectric element against the axial force is 4.9 × 10 ^2.
It is preferably N (50 kgf) or more. here,
The axial force means a force applied to the piezoelectric element by the molten thermoplastic resin injected into the cavity. Further, the proof stress against the axial force is the force generated by the piezoelectric element,
It is a resistance force against the force applied to the piezoelectric element by the molten thermoplastic resin injected into the cavity.

It is desirable to dispose a check valve at the tip of the pressurized fluid introducing nozzle to prevent the molten thermoplastic resin injected into the cavity from entering. If the diameter of the opening is such that the thermoplastic resin does not enter, the check valve can be dispensed with. Further, a pressurized fluid introducing nozzle is disclosed in Japanese Patent Laid-Open No. 4-31.
Heating with the heating device disclosed in Japanese Patent Laid-Open No. 015 is also effective for preventing the pressurized fluid introducing nozzle from being blocked by the thermoplastic resin and for reliably introducing the pressurized fluid. Specifically, a ring-shaped heater may be attached to the outer wall of the tip of the pressurized fluid introduction nozzle.

The pressurizing fluid introduction nozzle may be attached to the mold assembly in the vicinity of the surface forming the mold cavity (referred to as the mold cavity surface) or in the molten resin injection portion. It may be in the sprue part or the runner part. When the pressurized fluid introduction nozzle is attached near the cavity surface of the mold, the tip of the pressurized fluid introduction nozzle when the pressurized fluid introduction nozzle is located at a predetermined position may be located in the cavity. It may be located in the same plane as the cavity surface of the mold. Further, the position of the tip of the pressurized fluid introduction nozzle when the pressurized fluid introduction nozzle is retracted may be located substantially in the same plane as the cavity surface of the mold, or may be located outside the cavity. May be. In this case, the clearance between the tip of the pressurized fluid introduction nozzle and the mold is preferably as small as possible, and specifically, it is desirable to set the clearance to about 10 μm to 20 μm.

The cross-sectional shape of the tip of the pressurized fluid introducing nozzle in the direction perpendicular to the axis of the pressurized fluid introducing nozzle is circular, elliptical, oval, polygonal, polygonal with rounded apex, etc. Although it may have any shape, it is preferably a circle or a polygon. The reciprocating stroke of the pressurized fluid introduction nozzle is a linear movement parallel to the axis of the pressurized fluid introduction nozzle.

The structure of the molten resin injection portion may be any known structure.

In the injection molding method of the present invention, the introduction of the pressurized fluid into the molten thermoplastic resin in the cavity may be started after the injection of the molten thermoplastic resin into the cavity is started. Can be performed during the injection into the cavity, at the same time as the injection is completed, or after the injection is completed and a predetermined time has elapsed. The amount of the molten thermoplastic resin injected into the cavity may be an amount that completely fills the cavity with the molten thermoplastic resin, or an amount that does not completely fill the cavity.

The thermoplastic resin used in the present invention includes:
There is no particular limitation, and polyolefin resins such as polyethylene resin and polypropylene resin; styrene resins such as polystyrene resin, AS resin, ABS resin, AES resin; PM
Methacrylic resins such as MA resins; polyoxymethylene (polyacetal) resins; polyamide 6, polyamide 6
6, polyamide-based resin such as polyamide MXD; modified polyphenylene ether (PPE) resin; polyphenylene sulfide resin; polyethylene terephthalate (PE
Examples thereof include T) resins, polyester resins such as polybutylene terephthalate (PBT) resins; thermoplastic resins such as liquid crystal polymers, and polymer alloys composed of at least two kinds of these thermoplastic resins. These thermoplastic resins include, for example, glass fibers, glass flakes, carbon fibers, wollastonite, aluminum borate whisker fibers in order to impart mechanical properties represented by rigidity, dimensional stability and the like to molded articles. Inorganic fibers composed of at least one material selected from the group consisting of potassium titanate whisker fibers, basic magnesium sulfate whisker fibers, calcium silicate whisker fibers and calcium sulfate whisker fibers may be contained. Further, for example, an effective expression amount of a stabilizer, a release agent, and an ultraviolet absorber may be blended with the thermoplastic resin.

As the pressurized fluid to be introduced, a gaseous substance such as nitrogen gas, carbon dioxide gas, air or helium gas at room temperature can be used, and a liquid such as water or a gas liquefied under high pressure can also be used. is there.

In molding a molded article, various conditions such as the amount of molten thermoplastic resin at the time of injection molding, temperature, pressure or injection speed, amount of pressurized fluid to be introduced, pressure or speed, cooling time of mold, etc. Must be appropriately selected and controlled depending on the type of resin used, the shape of the mold, etc., and cannot be uniquely determined.

In the present invention, since the moving device is provided with the piezoelectric element, unlike the prior art, it is not necessary to prepare a fluid pressure generating source, for example, a hydraulic pressure generating device. It can be simplified. Further, the size of the moving device can be reduced.

[0029]

EXAMPLES The present invention will be described below based on examples with reference to the drawings, but the present invention is not limited to these examples.

(Embodiment 1) Embodiment 1 relates to a moving device for a pressurized fluid introducing nozzle, a pressurized fluid introducing device, a mold assembly and an injection molding method of the present invention, and particularly to the first construction. The present invention relates to an injection molding method. A conceptual view of an injection molding apparatus including the mold assembly of the first embodiment is shown in FIG. 1, and a detailed view of the pressurized fluid introducing device including a moving device for the pressurized fluid introducing nozzle is shown in FIG.

The mold assembly according to the first embodiment includes a mold 10 and a pressurized fluid introducing device 20 composed of a pressurized fluid introducing nozzle 21 and a moving device 30. Mold 10
It is composed of a fixed mold part 11 and a movable mold part 12, and when the mold is clamped, a cavity 13 is formed. The mold 10 is provided with a molten resin injection portion (gate portion 14) for injecting a molten thermoplastic resin into the cavity 13. The gate portion 14 shown in FIG. 1 has a direct structure and includes a runner portion and a sprue portion (refer to reference numeral 15).
(Shown by) is connected to the injection cylinder 16. The structure of the gate portion 14 is not limited to the direct structure.

The pressurized fluid introduction nozzle 21 has an opening 23 at the tip 22. Also, a check valve (not shown) is arranged at the tip portion. In the example shown in FIG. 1, the mounting position of the pressurized fluid introduction nozzle 21 in the mold assembly is
It is near the cavity surface of the mold. After clamping the mold, moving device 3
When the pressurized fluid introduction nozzle 21 is positioned at a predetermined position by 0, the tip 22 of the pressurized fluid introduction nozzle 21 projects into the cavity 13. Further, the tip end portion 22 of the pressurized fluid introduction nozzle 21 when the pressurized fluid introduction nozzle 21 retracts and is located at the backward movement end is substantially aligned with the cavity surface of the mold. A circular pressurized fluid introduction nozzle 21 having a circular cross-section with a diameter of 7 mm at the tip portion of the pressurized fluid introduction nozzle 21 when cut in a direction perpendicular to the moving direction axis line of the pressurized fluid introduction nozzle 21 was used. Pressurized fluid introduction nozzle 2
1 is connected to a pressurized fluid source (not shown) via a pipe 26. Further, the pressurized fluid introduction nozzle 21 is fixed to the upper portion of the mounting portion 24.

The moving device 30 for reciprocating the pressurized fluid introduction nozzle 21 is provided with a piezoelectric element 31. A connector 32 is provided on the piezoelectric element 31 and is connected to an external power source via wiring (not shown). The lower end portion of the piezoelectric element 31 is attached to the base portion 33 by the bolt 34, and the base portion 33 is attached to the movable mold portion 12. Further, the attachment portion 24 is attached to the upper end portion of the piezoelectric element 31 using a bolt 25. Piezoelectric element 31
When a voltage is applied to the piezoelectric element 31, the piezoelectric element 31 expands,
The pressurized fluid introduction nozzle 21 is moved. As the piezoelectric element 31, a piezoelectric element having a length of 100 mm and a proof stress of the piezoelectric element against an axial force of 2.2 × 10 ³ N (224 kgf) was used. Incidentally, the relationship between the voltage applied to the piezoelectric element and the displacement amount of the piezoelectric element was measured in advance. The relationship is a displacement amount proportional to the square of the applied voltage, and the displacement amount when 600 V is applied is It was 100 μm. A strain gauge (not shown) is attached to the piezoelectric element 31.

3 and 4 which are schematic sectional views of the mold 10 and the like, and the movable mold part 12 in the vicinity of the pressurized fluid introducing nozzle 21 and a part of the cavity 13 are schematically illustrated. The injection molding method of the first embodiment will be described with reference to FIGS. 5 and 6. It should be noted that the injection cylinder 16 is not shown in FIGS. 3 and 4.

[Step-100] First, as shown in FIG. 1, the fixed mold part 11 and the movable mold part 12 are clamped, and the moving fluid 30 moves the pressurized fluid introduction nozzle 21 to a predetermined position. Positioned. Specifically, the piezoelectric element 31 has 60
Applying 0 volt, the tip 2 of the pressurized fluid introduction nozzle 21
2 was projected into the cavity 13 by about 100 μm (see FIG. 5A).

[Step-110] Then, after plasticizing, melting and measuring the thermoplastic resin in the injection cylinder 16,
From injection cylinder 16 to runner and sprue 1
5, the molten thermoplastic resin 40 was injected into the cavity 13 through the gate portion 14 (see FIG. 3). Injection conditions,
An example is given in Table 1 below. The thermoplastic resin used was polypropylene resin. Further, the volume of the molten thermoplastic resin 40 injected into the cavity 13 is set to a volume that does not completely fill the cavity 13. The tip 22 of the pressurized fluid introduction nozzle 21 remains in a state of protruding into the cavity 13 (see FIG. 5B).

[Table 1] Molten thermoplastic resin temperature: 210 ° C Mold temperature: 40 ° C Injection time: 4.0 seconds

The pressurized fluid introducing nozzle 21 is also driven by the pressure of the molten thermoplastic resin 40 injected into the cavity 13.
There is no change in the position of. Although the molten thermoplastic resin enters from the tip of the pressurized fluid introduction nozzle 21, the check valve (not shown) prevents the molten thermoplastic resin from entering the upstream side of the check valve. Furthermore, since the clearance between the tip of the pressurized fluid introduction nozzle 21 and the movable mold part 12 is about 10 μm to 20 μm, there is no risk that the molten thermoplastic resin will leak to the outside from this clearance.

[Step-120] Simultaneously with the completion of injection of the molten thermoplastic resin 40 into the cavity 13, the cavity 1
The pressurized fluid (specifically, nitrogen gas) was started to be introduced into the molten thermoplastic resin 40 injected into the nozzle 3 through the opening 23 of the pressurized fluid introduction nozzle 21. As a result, a hollow portion 41 was formed inside the molten thermoplastic resin 40 injected into the cavity 13 (see FIGS. 4 and 6 (A)). The introduction conditions of the pressurized fluid are illustrated in Table 2 below.
While the pressurized fluid was introduced from the pressurized fluid introducing nozzle 21 into the molten thermoplastic resin 40 injected into the cavity 13, the tip 22 of the pressurized fluid introducing nozzle 21 was kept held at that position. . Specifically, the output of the strain gauge is calculated to measure the displacement amount of the piezoelectric element 31, and the set displacement amount (1
The voltage applied to the piezoelectric element was controlled by feeding back the deviation from the (.00 μm), and the tip portion 22 of the pressurized fluid introduction nozzle 21 was kept held at that position.

[Table 2] Pressure of pressurized fluid at the time of introduction: 6 × 10 ⁶ Pa Holding period of pressurized fluid: 40 seconds from the start of introduction of pressurized fluid Final pressurized fluid pressure: 4 × 10 ⁶ Pa

[Step-130] After the elapse of 55 seconds from the start of injection, the moving device 30 is operated, specifically, the application of the voltage to the piezoelectric element 31 is stopped, so that the pressurized fluid introduction nozzle 21 is released. Was moved backward and was positioned at the reverse end (see FIG. 6B). As a result, the tip 22 of the pressurized fluid introduction nozzle 21 was made to substantially coincide with the cavity surface of the mold. The amount of movement of the pressurized fluid introduction nozzle 21 (the amount of displacement of the piezoelectric element 31) is 100 μm. Thus
Tip 22 of pressurized fluid introduction nozzle 21 and cavity 13
A gap 42 is formed between the thermoplastic resin 40A inside and
The pressurized fluid in the hollow portion 41 was released to the atmosphere through the gap 42.

[Step-140] After 60 seconds from the start of injection, the mold was opened and the molded product was taken out from the mold. In this way, the pressurized fluid was introduced into the molten thermoplastic resin injected into the cavity 13 provided in the mold 10, and the injection molded product having the hollow portion 41 could be molded. No noticeable indentation was found in the obtained injection-molded product. Moreover, the pressurized fluid in the hollow portion 41 could be reliably released into the atmosphere.

(Example 2) Example 2 is a modification of Example 1 and relates to an injection molding method according to the second configuration. In Example 2, the same mold assembly as in Example 1 was used.
Hereinafter, the injection of the second embodiment will be described with reference to FIGS. 7, 5A and 6 which schematically show the pressurized fluid introduction nozzle 21, the movable mold part 12 in the vicinity thereof, and part of the cavity 13. The molding method will be described.

[Step-200] First, the fixed mold part 11 and the movable mold part 12 are clamped, and by the moving device 30,
The pressurized fluid introduction nozzle 21 was positioned at a predetermined position.
Specifically, unlike the first embodiment, no voltage is applied to the piezoelectric element 31, and the tip portion 22 of the pressurized fluid introduction nozzle 21 is set to substantially match the cavity surface of the mold ((A in FIG. 7). )
reference).

[Step-210] Then, after plasticizing, melting and measuring the thermoplastic resin in the injection cylinder 16,
From injection cylinder 16 to runner and sprue 1
5, the molten thermoplastic resin 40 was injected into the cavity 13 through the gate portion 14. The injection conditions were the same as in Table 1. The thermoplastic resin used was polypropylene resin. Further, the molten thermoplastic resin 40 injected into the cavity 13
Was set so that the cavity 13 was not completely filled. The tip portion 22 of the pressurized fluid introduction nozzle 21 remains substantially aligned with the cavity surface of the mold (see FIG. 7B).

[Step-220] After the elapse of 4 seconds from the start of injection, the moving device 30 is operated and the pressurized fluid introduction nozzle 2
1 is advanced from a predetermined position to pressurize fluid introduction nozzle 2
The tip 22 of No. 1 was projected into the cavity. Specifically, 600 volt is applied to the piezoelectric element 31 so that the tip portion 22 of the pressurized fluid introduction nozzle 21 moves into the cavity 13 by about 1 mm.
It was set to a state of protruding by 100 μm (see FIG. 5B).

[Step-230] Simultaneously with the completion of injection of the molten thermoplastic resin 40 into the cavity 13, the cavity 1
The pressurized fluid (specifically, nitrogen gas) was started to be introduced into the molten thermoplastic resin 40 injected into the nozzle 3 through the opening 23 of the pressurized fluid introduction nozzle 21. As a result, a hollow portion 41 was formed inside the molten thermoplastic resin 40 injected into the cavity 13 (see FIG. 6A). The conditions for introducing the pressurized fluid were the same as those exemplified in Table 2. While the pressurized fluid was introduced from the pressurized fluid introducing nozzle 21 into the molten thermoplastic resin 40 injected into the cavity 13, the tip 22 of the pressurized fluid introducing nozzle 21 was kept held at that position. . Specifically, the output of the strain gauge is calculated to measure the displacement amount of the piezoelectric element 31, and the set displacement amount (10
0 μm) was fed back to control the voltage applied to the piezoelectric element, and the tip portion 22 of the pressurized fluid introduction nozzle 21 was kept held at that position.

[Step-240] After the elapse of 55 seconds from the start of injection, the moving device 30 is operated, specifically, by stopping the application of the voltage to the piezoelectric element 31, the pressurized fluid introducing nozzle 21. Was moved backward and was positioned at the reverse end (see FIG. 6B). As a result, the tip 22 of the pressurized fluid introduction nozzle 21 was made to substantially coincide with the cavity surface of the mold. The amount of movement of the pressurized fluid introduction nozzle 21 (the amount of displacement of the piezoelectric element 31) is 100 μm. Thus
Tip 22 of pressurized fluid introduction nozzle 21 and cavity 13
A gap 42 is formed between the thermoplastic resin 40A inside and
The pressurized fluid in the hollow portion 41 was released to the atmosphere through the gap 42.

[Step-250] After 60 seconds had elapsed from the start of injection, the mold was opened and the molded product was taken out from the mold. In this way, the pressurized fluid was introduced into the molten thermoplastic resin injected into the cavity 13 provided in the mold 10, and the injection molded product having the hollow portion 41 could be molded. No noticeable indentation was found in the obtained injection-molded product. Moreover, the pressurized fluid in the hollow portion 41 could be reliably released into the atmosphere.

(Example 3) Example 3 is a modification of Example 1 and relates to an injection molding method according to a third configuration. In Example 3, the same mold assembly as in Example 1 was used.
Hereinafter, with reference to FIG. 7, FIG. 8 and FIG. 6B schematically showing a part of the pressurizing fluid introduction nozzle 21, the movable mold part 12 and the cavity 13 in the vicinity thereof, the injection of the third embodiment The molding method will be described.

[Step-300] First, the fixed mold part 11 and the movable mold part 12 are clamped, and by the moving device 30,
The pressurized fluid introduction nozzle 21 was positioned at a predetermined position.
Specifically, unlike the first embodiment, no voltage is applied to the piezoelectric element 31, and the tip portion 22 of the pressurized fluid introduction nozzle 21 is set to substantially match the cavity surface of the mold ((A in FIG. 7). )
reference).

[Step-310] Then, after plasticizing, melting and measuring the thermoplastic resin in the injection cylinder 16,
From injection cylinder 16 to runner and sprue 1
5, the molten thermoplastic resin 40 was injected into the cavity 13 through the gate portion 14. The injection conditions were the same as in Table 1. The thermoplastic resin used was polypropylene resin. Further, the molten thermoplastic resin 40 injected into the cavity 13
Was set so that the cavity 13 was not completely filled. The tip portion 22 of the pressurized fluid introduction nozzle 21 remains substantially aligned with the cavity surface of the mold (see FIG. 7B).

[Step-320] Simultaneously with the completion of injection of the molten thermoplastic resin 40 into the cavity 13, the cavity 1
The pressurized fluid (specifically, nitrogen gas) was started to be introduced into the molten thermoplastic resin 40 injected into the nozzle 3 through the opening 23 of the pressurized fluid introduction nozzle 21. As a result, the hollow portion 41 was formed inside the molten thermoplastic resin 40 injected into the cavity 13 (see FIG. 8A). The conditions for introducing the pressurized fluid were the same as those exemplified in Table 2. While the pressurized fluid was introduced from the pressurized fluid introducing nozzle 21 into the molten thermoplastic resin 40 injected into the cavity 13, the tip 22 of the pressurized fluid introducing nozzle 21 was kept held at that position. . Specifically, the output of the strain gauge is calculated to measure the displacement amount of the piezoelectric element 31, and the set displacement amount (10
0 μm) was fed back to control the voltage applied to the piezoelectric element, and the tip portion 22 of the pressurized fluid introduction nozzle 21 was kept held at that position.

[Step-320] After the elapse of 55 seconds from the start of injection, the moving device 30 is actuated, more specifically, 600 V is applied to the piezoelectric element 31, thereby making the pressurized fluid introduction nozzle 100 μm, It was moved forward (see FIG. 8B).

[Step-330] Then, 56 seconds after the injection is started, the moving device 30 is actuated, specifically, by stopping the application of the voltage to the piezoelectric element 31, the pressurized fluid introducing nozzle 21 is released. Was moved backward and was positioned at the reverse end (see FIG. 6B). As a result, the tip 22 of the pressurized fluid introduction nozzle 21 was made to substantially coincide with the cavity surface of the mold. The amount of movement of the pressurized fluid introduction nozzle 21 (the amount of displacement of the piezoelectric element 31) is 100 μm. Thus, a gap 42 is created between the tip 22 of the pressurized fluid introduction nozzle 21 and the thermoplastic resin 40A in the cavity 13, and the pressurized fluid in the hollow portion 41 is released to the atmosphere through this gap 42. did.

[Step-340] After 60 seconds from the start of injection, the mold was opened and the molded product was taken out from the mold. In this way, the pressurized fluid was introduced into the molten thermoplastic resin injected into the cavity 13 provided in the mold 10, and the injection molded product having the hollow portion 41 could be molded. No noticeable indentation was found in the obtained injection-molded product. Moreover, the pressurized fluid in the hollow portion 41 could be reliably released into the atmosphere.

(Comparative Example) In the comparative example, the same mold assembly as in Example 1 was used. In addition, the piezoelectric element is
0mm, the proof stress of the piezoelectric element against the axial force is 2.2 × 10
³ N (224 kgf) was used. The relationship between the voltage applied to the piezoelectric element and the displacement amount of the piezoelectric element was measured in advance. The relationship is a displacement amount proportional to the square of the applied voltage, and the displacement amount when 200 V is applied is 1. It was 7 μm.

Then, the same injection molding as in Example 3 was performed. However, in the same step as [Step-320], the pressurized fluid introduction nozzle was moved forward by 1.7 μm by applying 200 V to the piezoelectric element.

The application of the voltage to the piezoelectric element was stopped to discharge the pressurized fluid from the hollow portion, and the pressurized fluid introducing nozzle was moved to the retracted position. The gap between the resin and the resin was too narrow, and it was difficult to discharge the pressurized fluid from the hollow portion.

The present invention has been described above based on the preferred embodiments, but the present invention is not limited to these. The structure of the mold assembly described in the examples, the thermoplastic resin used in the examples, injection molding conditions, etc. are examples.
It can be changed appropriately. Although the pressurized fluid introducing device is arranged in the movable mold part 12 in the embodiment, it may be arranged in the fixed mold part 11. Further, the mounting position of the pressurized fluid introduction nozzle 21 in the mold assembly may be within the molten resin injection portion (gate portion 14), or within the sprue portion or runner portion.

The moving device may be provided with a displacement magnifying mechanism. FIG. 9 shows a detailed view of the pressurized fluid introducing device including the moving device 30A for the pressurized fluid introducing nozzle having the displacement magnifying mechanism. This displacement magnifying mechanism uses the piezoelectric element 3
1 and hydraulic pressure work together. More specifically,
The displacement magnifying mechanism includes a piston body portion 50, a piston portion 51 slidable inside the piston body portion 50, a plunger portion 52 slidably arranged inside the tip portion of the piston body portion 50, and a piston. Inside the main body 50,
It is composed of oil 53 filled in the space between the piston portion 51 and the plunger portion 52. The piezoelectric element 31 is arranged in the rear space of the piston body portion 50, and the piezoelectric element 31 is attached to the piston portion 51. The displacement of the piezoelectric element 31 causes the piston portion 51 to slide. A rear end portion of the pressurized fluid introduction nozzle, more specifically, an attachment portion 24 to which the pressurized fluid introduction nozzle 21 is fixed is attached to the tip end portion of the plunger portion 52 using a bolt 25. . By making the cross-sectional area (D ₂ ) of the plunger portion 52 smaller than the cross-sectional area (D ₁ ) of the piston portion 51, the displacement of the piezoelectric element 31 can be enlarged by (D ₁ / D ₂ ) times. . That is, when the piezoelectric element 31 expands by ΔX, the pressurized fluid introduction nozzle 21 advances by (D ₁ / D ₂ ) ΔX. The piston body 50 is, for example, the movable mold unit 10
Is attached to. Note that it is possible to replenish the oil into the space between the piston portion 51 and the plunger portion 52 by using a check valve, a pipe, and the like (not shown). The moving device provided with such a displacement magnifying mechanism can be applied to the moving devices in the various embodiments described above.

[0062]

According to the present invention, since the means for holding the pressurized fluid introduction nozzle against the high pressure of the molten thermoplastic resin injected into the cavity is constituted by the piezoelectric element, the conventional technique is used. Unlike the above, it is not necessary to prepare a fluid pressure generation source such as a hydraulic pressure generation device, the structure of the pressurized fluid introduction device can be simplified, and the moving device can be downsized. As a result, it is possible to solve the problem that the manufacturing cost of the entire injection molding apparatus increases, and finally it is possible to suppress an increase in the manufacturing cost of the injection molded product.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an injection molding apparatus including a mold assembly according to a first embodiment.

FIG. 2 is a detailed view of a pressurized fluid introduction device including a moving device for a pressurized fluid introduction nozzle.

FIG. 3 is a conceptual diagram of a mold assembly for explaining the injection molding method of the first embodiment.

FIG. 4 is a conceptual diagram of the mold assembly for explaining the injection molding method of the first embodiment, following FIG.

FIG. 5 is a diagram schematically showing a pressurized fluid introduction nozzle, a movable mold part in the vicinity thereof, and a part of a cavity for explaining the injection molding method of the first embodiment.

FIG. 6 is a diagram schematically illustrating the injection molding method of the first embodiment, following FIG. 5, and schematically showing the pressurized fluid introduction nozzle, the movable mold part in the vicinity thereof, and part of the cavity.

FIG. 7 is a diagram schematically showing a pressurized fluid introduction nozzle, a movable mold part in the vicinity thereof, and a part of a cavity for explaining the injection molding method of Example 2;

FIG. 8 is a diagram schematically showing a pressurized fluid introduction nozzle, a movable mold part in the vicinity thereof, and part of a cavity for explaining the injection molding method of Example 3;

FIG. 9 is a detailed view of a pressurized fluid introduction device including a moving device for a pressurized fluid introduction nozzle.

[Explanation of symbols]

10 ... Mold, 11 ... Fixed mold part, 12 ... Movable mold part, 13 ... Cavity, 14 ... Gate part, 15 ... Runner part and sprue part, 16 ...・ ・
Injection cylinder, 20 ... Pressurized fluid introducing device, 21
... Pressurized fluid introduction nozzle, 22 ... Tip of pressurized fluid introduction nozzle, 23 ... Opening portion, 24 ... Mounting portion,
25, 34 ... Bolts, 26 ... Piping, 30, 30
A ... Moving device, 31 ... Piezoelectric element, 32 ... Connector, 33 ... Base, 40 ... Molten thermoplastic resin, 40A ... Thermoplastic resin, 41 ... Hollow part, Four
2 ... gap, 50 ... piston body, 51 ...
Piston part, 52 ... Plunger part, 53 ... Oil

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoko Imaizumi             5-6 Higashi-Hachiman 5-2, Hiratsuka City, Kanagawa Prefecture             Ryo Engineering Plastics Stock Association             Company Technology Center (72) Inventor Kazuaki Ochiai             5-6 Higashi-Hachiman 5-2, Hiratsuka City, Kanagawa Prefecture             Ryo Engineering Plastics Stock Association             Company Technology Center F-term (reference) 4F202 AG07 AJ02 AR07 AR12 AR16                       CA11 CK17                 4F206 AG07 AJ02 AR074 AR12                       AR16 JA07 JF06 JL02 JM05                       JM13 JN27 JQ81

Claims (47)

[Claims] 1. An opening is provided at a tip portion for introducing a pressurized fluid into a molten thermoplastic resin injected into a cavity provided in a mold to form an injection molded product having a hollow portion. A moving device for reciprocating the pressurized fluid introduction nozzle, comprising a piezoelectric element, and a moving device for the pressurized fluid introduction nozzle. 2. The moving device for a pressurized fluid introducing nozzle according to claim 1, wherein the piezoelectric element is composed of a lead zirconate titanate-based compound. 3. The pressurized fluid introducing nozzle according to claim 1, wherein the position of the pressurized fluid introducing nozzle is controlled by making the voltage applied to the piezoelectric element variable. Mobile device. 4. The moving device for a pressurized fluid introducing nozzle according to claim 3, wherein the voltage applied to the piezoelectric element is 25 to 5000 volts. 5. The voltage applied to the piezoelectric element is controlled by measuring the amount of displacement of the piezoelectric element and feeding back the deviation from the set amount of displacement to control the voltage applied to the piezoelectric element. A moving device for a pressurized fluid introduction nozzle according to paragraph. 6. The voltage applied to the piezoelectric element is determined based on the relationship between the voltage applied to the piezoelectric element and the displacement amount of the piezoelectric element measured in advance. 2. A moving device for a pressurized fluid introduction nozzle according to item 1. 7. The moving device for a pressurized fluid introducing nozzle according to claim 1, further comprising a displacement magnifying mechanism. 8. The moving device for a pressurized fluid introducing nozzle according to claim 7, wherein the displacement magnifying mechanism is operated by hydraulic pressure. 9. The moving distance of the pressurized fluid introducing nozzle is 10 μm.
The moving device for a pressurized fluid introduction nozzle according to any one of claims 1 to 8, wherein the moving device has a length of m or more and 5 mm or less. 10. The displacement amount of the piezoelectric element is 0.01 μm or more per 100 volt applied voltage to the piezoelectric element and per 1 mm length of the piezoelectric element. A movement device for a pressurized fluid introduction nozzle according to any one of claims. 11. The proof stress of the piezoelectric element against the axial force is 4.9.
The moving device for a pressurized fluid introduction nozzle according to any one of claims 1 to 10, wherein the moving device has a pressure of × 10 ² N or more. 12. A pressurized fluid introducing nozzle having an opening at its tip, and a rear end of said pressurized fluid introducing nozzle are attached.
An injection molding having a hollow portion by introducing a pressurized fluid into a molten thermoplastic resin injected into a cavity provided in a mold, which comprises a moving device for reciprocating the pressurized fluid introduction nozzle. A pressurized fluid introducing device for molding an article, wherein the moving device comprises a piezoelectric element. 13. The pressurized fluid introducing device according to claim 12, wherein the piezoelectric element is made of a lead zirconate titanate compound. 14. The pressurized fluid introducing apparatus according to claim 12, wherein the position of the pressurized fluid introducing nozzle is controlled by making the voltage applied to the piezoelectric element variable. 15. The voltage applied to the piezoelectric element is 25 to 5000 volts.
The pressurized fluid introduction device according to item 1. 16. The voltage applied to the piezoelectric element is controlled by measuring the displacement of the piezoelectric element and feeding back the deviation from the set displacement.
5. The pressurized fluid introduction device according to any one of 5 above. 17. The voltage applied to the piezoelectric element is determined based on the relationship between the voltage applied to the piezoelectric element and the displacement amount of the piezoelectric element measured in advance. 2. The pressurized fluid introducing device according to item 1. 18. The pressurized fluid introducing device according to claim 12, wherein the moving device further comprises a displacement magnifying mechanism. 19. The pressurized fluid introducing device according to claim 18, wherein the displacement magnifying mechanism operates by hydraulic pressure. 20. The moving distance of the pressurized fluid introducing nozzle is 10
13. The thickness is not less than μm and not more than 5 mm.
20. The pressurized fluid introduction device according to claim 19. 21. The displacement amount of the piezoelectric element is 0.01 μm or more per 100 volt applied voltage to the piezoelectric element and per 1 mm length of the piezoelectric element. The pressurized fluid introduction device according to claim 1. 22. The proof stress of the piezoelectric element against the axial force is 4.9.
22. The pressurized fluid introducing device according to any one of claims 12 to 21, characterized in that it has a density of × 10 ² N or more. 23. (A) A cavity and a mold having a molten resin injection portion for injecting a molten thermoplastic resin into the cavity, (B) a pressurized fluid introduction nozzle having an opening at the tip portion, (C) the rear end of the pressurized fluid introduction nozzle is attached,
A moving device for reciprocating the pressurized fluid introduction nozzle, for introducing a pressurized fluid into the molten thermoplastic resin injected into the cavity to form an injection-molded article having a hollow portion The mold assembly according to claim 1, wherein the moving device includes a piezoelectric element. 24. The mold assembly according to claim 23, wherein the piezoelectric element is composed of a lead zirconate titanate-based compound. 25. The mold assembly according to claim 23 or 24, wherein the position of the pressurized fluid introducing nozzle is controlled by making the voltage applied to the piezoelectric element variable. 26. The voltage applied to the piezoelectric element is 25 to 5000 volts.
The mold assembly described in. 27. The voltage applied to the piezoelectric element is controlled by measuring the displacement of the piezoelectric element and feeding back the deviation from the set displacement.
6. The mold assembly according to any one of 6 above. 28. The voltage applied to the piezoelectric element is determined based on the relationship between the voltage applied to the piezoelectric element and the displacement amount of the piezoelectric element measured in advance. The mold assembly according to item 1. 29. The mold assembly according to claim 23, wherein the moving device further comprises a displacement magnifying mechanism. 30. The mold assembly according to claim 29, wherein the displacement magnifying mechanism is hydraulically operated. 31. The moving distance of the pressurized fluid introducing nozzle is 10
24. The thickness is not less than μm and not more than 5 mm.
31. The mold assembly according to claim 30. 32. The displacement amount of the piezoelectric element is 0.01 μm or more per 100 volt applied voltage to the piezoelectric element and per 1 mm length of the piezoelectric element. The mold assembly according to any one of items. 33. The proof stress of the piezoelectric element against the axial force is 4.9.
33. The mold assembly according to claim 23, wherein the mold assembly has a density of × 10 ² N or more. 34. A mold having (A) a cavity and a molten resin injection part for injecting a molten thermoplastic resin into the cavity, (B) a pressurized fluid introduction nozzle having an opening at the tip. And (C) a piezo-electric element, a rear end of the pressurized fluid introduction nozzle is attached, and a moving device for reciprocating the pressurized fluid introduction nozzle, and a heat of fusion injected into the cavity. An injection molding method for molding an injection molded product using a mold assembly for introducing a pressurized fluid into a plastic resin to mold an injection molded product having a hollow portion, comprising: (a) after mold clamping A moving device to position the pressurized fluid introduction nozzle at a predetermined position, (b) injecting the molten thermoplastic resin into the cavity, (c) injecting the molten thermoplastic resin, or after completion of the injection, the cavity Was injected into A pressurized fluid is introduced into the molten thermoplastic resin from a pressurized fluid introduction nozzle to form a hollow portion inside the molten thermoplastic resin injected into the cavity, and (d) after a certain period of time, The pressurized fluid introducing nozzle is retracted by the operation of the moving device to create a gap between the tip of the pressurized fluid introducing nozzle and the thermoplastic resin, and the pressurized fluid in the hollow portion is released through the gap. An injection molding method comprising the steps of: 35. After the mold is clamped, the tip of the pressurized fluid introducing nozzle projects into the cavity in a state where the pressurized fluid introducing nozzle is positioned at the predetermined position by the operation of the moving device, It is characterized in that, while introducing the pressurized fluid from the pressurized fluid introducing nozzle into the injected molten thermoplastic resin, the tip of the pressurized fluid introducing nozzle is held at that position by the operation of the moving device. The injection molding method according to claim 34. 36. A moving device after injecting the molten thermoplastic resin into the cavity and before introducing the pressurized fluid from the pressurized fluid introduction nozzle into the inside of the molten thermoplastic resin injected into the cavity. The forward movement of the pressurized fluid introducing nozzle from the predetermined position by causing the operation of the above to project the tip of the pressurized fluid introducing nozzle into the cavity, and introduce the pressurized fluid into the molten thermoplastic resin injected into the cavity. 35. The injection molding method according to claim 34, wherein the tip of the pressurized fluid introducing nozzle is held at that position by the operation of the moving device while introducing the pressurized fluid from the nozzle. 37. After the hollow portion is formed inside the molten thermoplastic resin injected into the cavity, the pressurized fluid introducing nozzle is moved from the predetermined position by the operation of the moving device before the elapse of the predetermined time. The injection molding method according to claim 34, wherein the injection molding method is performed by advancing. 38. The injection molding method according to claim 34, wherein the piezoelectric element is made of a lead zirconate titanate-based compound. 39. The injection molding according to any one of claims 34 to 38, wherein the position of the pressurized fluid introducing nozzle is controlled by making the voltage applied to the piezoelectric element variable. Method. 40. The voltage applied to the piezoelectric element is 25 to 5000 volts.
The mold assembly described in. 41. The voltage applied to the piezoelectric element is controlled by measuring the displacement of the piezoelectric element and feeding back the deviation from the set displacement.
The injection molding method according to any one of 0. 42. The voltage applied to the piezoelectric element is determined based on the relationship between the voltage applied to the piezoelectric element and the displacement amount of the piezoelectric element measured in advance. The injection molding method according to Item 1. 43. The injection molding method according to claim 34, wherein the moving device further comprises a displacement magnifying mechanism. 44. The injection molding method according to claim 43, wherein the displacement magnifying mechanism operates by hydraulic pressure. 45. The moving distance of the pressurized fluid introducing nozzle is 10
35. The thickness is not less than μm and not more than 5 mm.
An injection molding method according to any one of claims 44 to 44. 46. The displacement amount of the piezoelectric element is 0.01 μm or more per 100 volts applied to the piezoelectric element and per 1 mm length of the piezoelectric element, according to claim 34 to claim 45. The injection molding method according to any one of claims. 47. The proof stress of the piezoelectric element against the axial force is 4.9.
The injection molding method according to any one of claims 34 to 46, wherein the injection molding method is × 10 ² N or more.