JPH07178779A - Cylindrical resin molded object, injection mold and injection molding method - Google Patents

Abstract

PURPOSE:To obtain a molded object of high accuracy and high quality by performing gate cutting with high accuracy while a molded object is received in a mold regardless of the presence of the odd-shaped of a key groove and certainly preventing the generation of a sink regardless of the kind of a resin. CONSTITUTION:A core pin 9 is fitted in a fixed mold 1 and the tip part of the core pin 9 is arranged in a cavity 7 to close fixed and movable molds 1, 2. A molten resin is ejected from the sprue 5 provided in the core pin 9 and charged in the cavity 7 through the disc gate 6 provided between the tip surface of the core pin 9 and the movable mold 2 opposed thereto. After the filling of the cavity 7 with the resin, the gate cutting punch 12 received in the movable mold 2 so as to be able to advance and retreat is allowed to advance and the tip part thereof is fitted to the outer periphery of the tip of the core pin 9 while the molten resin in a communication part 8 is pushed in the cavity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylindrical resin molded body which is molded by filling a cavity with a molten resin through a disc gate, an injection molding die for molding the same, and an injection molding method. It is about.

[0002]

2. Description of the Related Art Generally, when a cylindrical resin molded body is molded by an injection molding method, as shown in FIG. 6 (a), a solid core pin matching the inner diameter of the molded body is formed in the cavity. (41) is placed. In this case, in order to prevent the generation of weld marks that may cause a reduction in product strength, the gate part (4) between the sprue (42) and the cavity is
3) is formed in a disk shape (hereinafter, such a gate portion is referred to as a disk gate (43)). Sprue (4
The molten resin supplied from 2) and flowing into the disc gate (43) is supplied to the cavity from the entire circumference of the disc gate (43).

By the way, the disk gate (4
When 3) is provided, the molten resin in the disc gate (43) and the molten resin in the cavity are integrally cured as shown in Fig. B, so that the disc gate is formed on the end face of the resin molded body (44). A disc portion (45) matching the shape of (43) is integrally molded. Since the disk portion (45) is originally unnecessary, conventionally, after removing the molded body (44) from the mold, the disk portion (45) is cut and removed using a lathe or the like (see FIG. C). .

[0004]

However, if the unnecessary portion is cut after the resin is cured in this way, there is a problem that the process becomes complicated and complicated. In addition, carbon fiber (C
F), glass fiber (GF), graphite (GR
P), a fluorine-based resin, or the like may be mixed, but in this case, the blade tip of the blade (bite) is easily worn, and frequent blade replacement is required.

On the other hand, as a method for solving such a problem, there is a method of arranging a gate cut punch in a mold and using the gate cut punch to perform a gate cut in the mold. That is, as shown in FIG. 7 (a), after the molten resin is injected and before the resin is cured, the gate cut punch (47) (also used as the core pin) previously arranged in the inner diameter portion of the cavity is advanced, As shown in FIG. 6B, the gate cut is performed by pushing the resin unnecessary as a molded body back into the sprue (42) at the tip portion of the gate cut punch (47) to interrupt the gap between the disc gate (43) and the cavity. Of.

However, according to this method, since the outer diameter surface of the gate cut punch (47) slides on the inner diameter portion of the resin molded body, the method can be applied to the resin molded body in which the accuracy of the inner diameter portion does not matter so much. However, it is difficult to apply to parts that require high precision and a complicated shape for the inner diameter sliding surface, such as sliding bearings, gears with keys, sleeves, washers, bearing races and the like.

Further, for example, a thermoplastic polyimide resin (P
I), polyamideimide resin (PAI), polyetherimide resin (PEI), polyetherketone resin (PE
K), polyetheretherketone resin (PEEK),
When using a heat-resistant resin such as polyphenylene sulfide resin (PPS), polyether nitrile resin (PEN), or aromatic ester resin, or when the above-mentioned filler or lubricant is mixed in the molten resin, high temperature Since the molten resin of No. 3 is supplied to the cavity, shrinkage is likely to occur along with the curing of the resin, and it becomes difficult to obtain a molded product of high precision and high quality.

This problem can similarly occur in general-purpose resins such as polyamide resin (PA), polyoxymethylene resin (POM), and polyethylene resin (PE).

Therefore, according to the present invention, it is possible to perform the gate cut with high precision while the molded body is housed in the mold regardless of the presence or absence of a deformed portion such as a key groove, and regardless of the type of resin. An object of the present invention is to provide a mold for injection molding of a tubular resin molded product and an injection molding method capable of preventing the occurrence of shrinkage and obtaining a molded product of high precision and high quality.

[0010]

[Means for Solving the Problems] To achieve the above object,
According to the present invention, a tubular resin molded body is obtained by disposing a core pin in the cavity to cause the fixed side mold and the movable side mold to abut against each other, and to fill the cavity with the resin from the sprue through the disc gate. In the injection mold for molding

The core pin is mounted on a fixed mold, the sprue is provided inside the core pin, and the disc gate is provided between the tip of the core pin and a movable mold opposite to the tip end of the core pin. Inside the mold on the side, it is possible to move forward and backward toward the communication part interposed between the disc gate and the molded body, and it is in the retracted position when the resin is filled, and it is moved forward after the resin is filled and before it is cured. Then, a cylindrical gate cut punch for arranging the resin in the disk gate and pushing the resin in the communicating portion into the cavity at the tip portion thereof was arranged.

The molten resin is filled in the cavity through the inside of the core pin mounted on the fixed side mold and the disk gate provided between the tip end surface of the core pin and the movable side mold facing the core pin, Before the molten resin is hardened, the cylindrical gate cut punch provided on the movable mold is moved forward, and the resin inside the disc gate is internally filled, and the tip of the resin is interposed between the disc gate and the molded body. The molten resin in the part was pushed into the cavity for gate cutting.

The molten resin is filled in the cavity through the inside of the core pin mounted on the fixed side mold and the disk gate provided between the tip end surface of the core pin and the movable side mold facing the core pin, Before the molten resin is hardened, the cylindrical gate cut punch provided on the movable mold is moved forward, and the resin inside the disc gate is internally filled, and the tip of the resin is interposed between the disc gate and the molded body. A tubular resin molded body is molded by pushing the molten resin in the cavity into the cavity and performing a gate cut.

[0014]

As shown in FIG. 5, the core pin (9) is mounted on the fixed mold (1), and the core pin (9) is placed in the cavity (7) to fix the fixed mold and the movable mold (1). ) (2)
(See Figure a). The molten resin flowing out from the sprue (5) inside the core pin (9) passes through a disc gate (6) formed between the tip end surface of the core pin (9) and the movable mold (2) facing the tip surface. It flows into the communication part (8) and then into the cavity (7). After the resin is filled and before the resin is cured, the cylindrical gate cut punch (12) housed in the movable mold (2) is advanced toward the communicating portion (8), as shown in FIG. While the resin in the disk gate (6) is being housed inside, the tip portion of the disk gate (6) presses the resin in the communication portion (8) and pushes it into the cavity (7). As a result, the gap between the cavity (7) and the disc gate (6) is cut off and a gate cut is made. Along with this, resin unnecessary as a molded body is pushed into the cavity, so that the resin pressure in the cavity rises and the occurrence of shrinkage after resin curing is suppressed.

[0015]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 shows the overall structure of an injection molding die according to the present invention. As shown in the figure, the fixed side mold (1) is composed of a plurality of members located on the fixed side (right side in the drawing) with the abutting surface (A) (parting line) as a boundary, and similarly the movable side mold. (2) is composed of a plurality of members located on the movable side (left side in the drawing).

The resin injected from a nozzle (not shown) has a first sprue (3), a runner (4), a second sprue (5) and a disc gate (6) provided on the stationary mold (1). , The cavity (7) through the communication part (8)
To be filled. The runners (4) are radially provided around the axis (L) of the first sprue (3) so as to perform multi-cavity production (see FIG. 2), and each runner (4) has a second end at the downstream end. Two sprues (5), a disc gate (6), a communication part (8) and a cavity (7) are formed respectively.

The arrangement of the cavities (7) is not limited to the above-mentioned radial arrangement, and other arrangements can be adopted. In this case, the molten resin is supplied to the cavities (7) almost simultaneously and in good balance. As such, each cavity (7) is preferably arranged symmetrically with respect to the first sprue (3). As an example corresponding to this, one in which the cavities (7) are arranged in parallel is conceivable (FIG. 3).
reference).

The second sprue (5) is formed inside the core pin (9) so as to penetrate therethrough along the axial direction thereof. The core pin (9) is mounted on a core pin plate (10), which is an element of the fixed mold (1), with its tip end located in the cavity (7).

FIG. 4 shows an enlarged view of the vicinity of the cavity (7). The disk gate (6) is provided between the tip surface of the core pin (9) and the movable die (2) facing the core pin (9), specifically, the tip surface of the solid gate cut punch guide (11). Composed. The outer diameter portion of the disc gate (6) communicates with the inner diameter portion of the cavity (7) via the tubular communication portion (8).

A cylindrical gate cut punch (12) is fitted onto the gate cut punch guide (11) with its tip facing the communicating portion (8). The gate-cut punch (12) can be moved forward and backward while being guided by the gate-cut punch guide (11). When the molten resin is filled, the gate-cut punch (12) is at the retracted position and its tip end face is the gate-cut punch. It is located on the same plane as the tip surface of the guide (11).

After the molten resin has been filled and before hardening (during pressure holding or cooling), the gate cut punch (12) is advanced so that its tip is located above the tip of the core pin (9) as shown in FIG. Also, when the core pin (9) is fitted to the outer periphery of the tip of the core pin (9) by protruding toward the fixed mold (1) side, the resin in the disk gate (6) is internally housed in the gate cut punch (12), and the disk gate ( There is a disconnection between 6) and the cavity (7). Along with this, the resin in the communication portion (8) is pressed by the tip portion of the gate cut punch (12) and is pushed into the cavity (7).

As described above, in the above-described mold, the gate cutting can be performed without sliding the outer diameter surface of the gate cut punch (12) and the inner diameter surface of the resin molded body, so that the inner diameter surface of the resin molded body is raised. The accuracy can be maintained, and the gate cut can be reliably performed even when the key groove or the like is formed in the inner diameter portion. Also, gate cut punch (1
By advancing 2), the molten resin in the communication part (8) is pushed into the cavity (7), so that the pressure of the molten resin in the cavity (7) increases. Therefore, it is also possible to prevent the occurrence of shrinkage due to resin curing.

Further, in the conventional mold (see FIG. 7), it is difficult to handle a large number of molded products because the resin unnecessary as a molded product is pushed into the sprue (42). The mold according to (2) has an advantage that unnecessary resin is pushed into the cavity (7), so that it is possible to easily handle a large number of chips.

When the gate is cut, it is desirable to move the gate cut punch (12) forward while vibrating it in the axial direction (movement direction of the gate cut punch). Specifically, as shown in FIG. 1, a gate cut punch (12)
Is connected to a vibrating plate (15) via a connecting rod (14), and the vibrating plate (15) is connected to a rod of a vibrating cylinder (16) arranged along the axial direction. . This allows
The gate cut punch (12) can be moved forward smoothly.

In this way, when the gate cutting is completed and the resin is completely cured, the mold opening work is performed. The procedure of this mold opening operation will be described below with reference to FIG.

First, when the mold opening cylinder (not shown) connected to the movable mold (2) is retracted, the spring (17) compressed at the time of abutting of the mold elastically returns to the core pin plate (10). Open between the runner stripper plate (19).
Since the runner (4) is locked to the runner stripper plate (19) by the runner lock pin (20) having the truncated cone-shaped lock portion (21) at the tip, the runner (4) is opened during the opening operation. Runner stripper plate (19)
Stick to and move to the fixed side. At the same time, the tip of the second sprue (5) and the disc gate (6) are cut and separated, and the second sprue (5) comes out of the core pin (9).

When the mold opening cylinder is further retracted,
One bolt seat surface (23) of the puller bolt (22) engages with the core pin plate (10) to restrict the backward movement of the core pin plate (10). As a result, the core pin plate (10) and the fixed-side mold plate (24) are opened, the molded body and the core pin (9) are separated, and the core pin (9) comes out from the inner diameter of the molded body. At this time, the opening amount between the core pin plate (10) and the fixed-side mold plate (24) needs to be set so that the core pin (9) can be completely removed from the molded body.

When the mold opening cylinder is further retracted,
The space between the runner stripper plate (19) and the fixed side mounting plate (26) is opened until the other bolt bearing surface (25) of the puller bolt (22) engages with the fixed side mounting plate (26). As a result, the runner (4) is disengaged from the lock portion (21), and the sprues (3) (5) and the runner (4) fall off the runner stripper plate (19). Around this time, the backward movement of the fixed-side template (24) is restricted by the bolt seat surface of the shoulder bolt (27), so that the fixed-side template (24) and the movable-side template (29) move. The force acting in the separating direction increases. PL lock (30) when the specified force is reached
Is released, the abutting surface (A) between the fixed side mold plate (24) and the movable side mold plate (29) is opened, and the mold opening work is completed.

When the mold opening work is completed, the ejector rod (not shown) of the molding machine presses the ejector rod (31) of the mold, and the ejector plate (32) and the ejector sleeve connecting rod (33) are used to eject the ejector. The sleeve (34) pushes the molded body out of the cavity (7). The disc portion formed on the disc gate (6) is pushed by the ejector pin (35) and discharged to the outside of the mold.

[0031]

As described above, according to the present invention, the gate is cut in the mold by using the gate cut punch instead of cutting the unnecessary portion after the resin is hardened as in the prior art, so that the process is complicated and complicated. Even if a filler, a lubricant, or the like is mixed into the molten resin without being turned into a solid state, the problem of an increase in the frequency of blade replacement cannot occur.

Further, since the gate cutting can be performed without sliding the outer diameter surface of the gate cut punch and the inner diameter surface of the resin molded body, the inner diameter surface of the resin molded body can be maintained with high accuracy, and Even if a deformed portion such as a key groove is formed on the inner diameter surface, the gate cut can be surely performed.

Further, by advancing the gate cut punch, the molten resin in the communicating portion is pushed into the cavity, so that the pressure of the molten resin in the cavity can be increased. Therefore, for example, thermoplastic polyimide resin (PI), polyamideimide resin (PAI), polyetherimide resin (PEI), polyetherketone resin (PEK), polyetheretherketone resin (PE)
EK), polyphenylene sulfide resin (PPS),
Even when a resin such as a polyether nitrile resin (PEN) or an aromatic ester resin is used, or when a filler, a lubricant, or the like is mixed in, it is possible to prevent shrinkage due to resin curing, and thus it is possible to achieve high accuracy. -It is possible to obtain a high-quality molded body. This effect can be similarly obtained when a general-purpose resin such as a polyamide resin (PA), a polyoxymethylene resin (POM), or a polyethylene resin (PE) is used.

[Brief description of drawings]

FIG. 1 is a sectional view of an injection molding die according to the present invention.

FIG. 2 is a plan view showing an arrangement mode of cavities in an injection molding die according to the present invention.

FIG. 3 is a plan view showing another arrangement example of cavities.

FIG. 4 is an enlarged cross-sectional view near the cavity in FIG.

FIG. 5 is a cross-sectional view showing the basic structure and basic operation of an injection molding die according to the present invention.

FIG. 6 is a cross-sectional view showing a conventional gate cutting method.

FIG. 7 is a cross-sectional view showing another conventional gate cutting method.

[Explanation of symbols]

 1 Fixed side mold 2 Movable side mold 3 Sprue (1st sprue) 4 Runner 5 Sprue (2nd sprue) 6 Disc gate 7 Cavity 8 Communication part 9 Core pin 12 Gate cut punch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoto Saito 4-12-4 Sakashita-cho, Hatogaya-shi, Saitama

Claims (3)

[Claims] 1. A tubular resin molding is provided by arranging a core pin in a cavity, abutting a fixed side mold and a movable side mold, and filling resin into the cavity from a sprue through a disc gate. In an injection molding mold for molding a body, the core pin is mounted on a mold on a fixed side, the sprue is provided inside the core pin, and the disc gate is provided on a tip end portion of the core pin and a movable side opposite to the tip end portion of the core pin. It is provided between the mold and the inside of the movable mold, and is movable back and forth toward a communication part interposed between the disc gate and the molded body,
It is in the retracted position when filling the resin, and after filling the resin,
Cylindrical resin molding characterized in that a cylindrical gate-cut punch for pushing the resin in the communicating portion into the cavity is arranged at the tip of the resin while advancing before the curing to accommodate the resin in the disc gate. Mold for body injection molding. 2. The molten resin is filled in the cavity through the inside of the core pin mounted on the fixed side mold and the disk gate provided between the tip end surface of the core pin and the movable side mold opposite thereto. Then, before the molten resin is cured, the cylindrical gate cut punch provided on the movable mold is moved forward so that the resin inside the disc gate is internally housed and the tip of the resin is interposed between the disc gate and the molded body. A method for injection molding a tubular resin molded body, characterized in that the molten resin in the communicating portion is pushed into the cavity to perform gate cutting. 3. The molten resin is filled in the cavity through the inside of the core pin mounted on the fixed side mold and the disk gate provided between the tip end surface of the core pin and the movable side mold opposite thereto. Then, before the molten resin is cured, the cylindrical gate cut punch provided on the movable mold is moved forward so that the resin inside the disc gate is internally housed and the tip of the resin is interposed between the disc gate and the molded body. A tubular resin molded body, characterized in that the molten resin in the communicating portion is pushed into the cavity and gate cut is performed.