JPH07329103A - Method of molding resin pulley - Google Patents

Abstract

PURPOSE:To improve characteristic of the strength and the like of a resin pulley by setting a metal insert fitting in a cavity, closing a mold at a position where a movable side cavity is retreated by a given distance from a predetermined position where the shape of a product is formed, injecting a material to be molded and, thereafter, advancing the movable side cavity up to the predetermined position. CONSTITUTION:A metal insert fitting is set in advance to a metel-fitting setting pin 3 in a fixed side cavity 2 to be fixed by a metal-fitting press pin 4. Also, the packing of a material to be molded is performed under the condition that a movable side cavity 5 is retreated from its predetermined position. Then, a gate is sealed by advancing a gate sealing pin 6, and the movable side cavity 5 is then advanced up to the predetermined position. Thereafter, a mold is opened to release a molded resin pulley. In the case where a side gate system is adopted, swelling hardly occurs in the vicinity of a gate because a residual stress around the gate is less, whereby a molding cycle can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a resin pulley having a cylindrical insert fitting by injection compression molding.

[0002]

2. Description of the Related Art Conventionally, resin pulleys are generally molded by compression molding or injection molding. In the case of molding by compression molding, there are practically no problems such as strength, but it takes time to mold and it is not possible to take many pieces.
The major drawback is low productivity.

On the other hand, injection molding is a molding method with good productivity, but in this case, it is usual to mold with a pinpoint gate having several gates from the disk portion of the pulley. FIG. 4A shows a pulley molded product molded by the pinpoint gate method. Such a pulley has a very weak strength in the weld portion (22) around the insert fitting (21), and thus the The required characteristics cannot be sufficiently satisfied for use as important mechanical parts such as. Further, as shown in FIG. 4 (b), in the case of a pulley having a hole (23) in the disc portion, the gate (20) must be near the insert fitting (21) -resin interface, and the weld portion ( The insufficient strength of 22) becomes more remarkable.

In injection molding, it may be considered that the side gate method is used, but a weld portion is formed on the opposite side of the gate, and the decrease in strength at this weld portion is more remarkable than in the pinpoint gate method. In any case, molding the pulley by injection molding inevitably reduces the strength of the weld portion, and has not been put to practical use as a mechanical part for automobiles or the like.

[0005]

As described above, the resin pulley manufactured by the injection molding method cannot satisfy required characteristics such as insufficient strength. The present invention has been completed as a result of various studies in order to solve the above-mentioned problems in injection molding, and is intended to improve characteristics such as strength of a resin pulley while maintaining good productivity. is there.

[0006]

According to the present invention, (1) in a method of molding a resin pulley having a cylindrical insert fitting embedded therein, the insert fitting is set in a cavity, and a movable side cavity is a final molded product of a pulley. The mold is closed when it is retracted from the predetermined position for forming the shape by a certain distance, and the molding material is injected and filled into the cavity,
Then, in the injection compression molding method for a resin pulley, which is characterized in that the movable side cavity is advanced to the predetermined position, and (2) the resin pulley molding method in which a cylindrical insert fitting is embedded and a hole is formed in a disk portion. , The movable side cavity is retracted from the predetermined position for forming the final molded product shape of the pulley by a certain distance, and the mold for forming the hole is retracted from the predetermined position. Resin which is characterized in that it closes, injection-fills the molding material into the cavity, and then advances the piece for forming the hole to the predetermined position, and at the same time or thereafter, advances the movable side cavity to the predetermined position. The present invention relates to an injection compression molding method for pulleys.

A mold used in the present invention will be described with reference to the drawings. FIG. 1 shows an example of a resin pulley injection compression molding die (principal part) of the present invention. The insert metal fitting (1) is previously set on the metal fitting set pin (3) of the fixed side cavity (2) and is fixed by the metal fitting holding pin (4). FIG. 1 (a) shows a state in which the movable cavity (5) is retracted from a predetermined position and is filled with the molding material. FIG. 1B shows a state in which the gate seal pin (6) is advanced to seal the gate, and then the movable cavity (5) is advanced to a predetermined position. After that, the mold is opened and the molded resin pulley is taken out. FIG. 1C shows the mold opened state.

FIG. 2 shows an example of a die (principal portion) for molding a resin pulley having a hole in the disc portion. , Fig. 2
FIG. 2 (a) shows a state in which the movable cavity (15) and the piece (17) for forming the hole are retracted from a predetermined position and filled with the molding material, and FIG. 2 (b) shows the gate seal pin (1).
6) and the piece (17) for forming the hole are advanced to seal the gate and form the hole (23). FIG. 2 (c) shows the movable cavity (15) advanced to a predetermined position. It is in a state of being made. After that, the mold is opened and the molded resin pulley is taken out as in the case described above. Although the piece for forming this hole is provided on the movable side cavity side in FIG. 2, it may be provided on the fixed side cavity side and is moved forward and backward by an external force.

In this case, the piece for forming the hole is formed as a part of the fixed side or movable side cavity as described above, but in the conventional method, this piece penetrates the inside of the cavity. When the molding material is filled, this piece serves as an obstacle, which hinders smooth filling, and a jumping phenomenon occurs on the side opposite to the gate, which further reduces the strength of the weld portion. Therefore, in the case of a pulley having a hole, as shown in FIG. 2, the piece forming the hole is not substantially in the cavity when the molding material is filled. After injection and filling, it is necessary to advance a piece for forming a hole by an external force into the cavity to form the hole.

Although the resin pulley is molded as described above, an example of a mold structure and an operating mechanism for retracting or advancing the movable cavity (5) from a predetermined position will be described below with reference to FIG. 3 (a) and 3 (b), a locking block (8) having an inclined lower surface is provided on the back surface of the movable side template (7) integrally attached to the outside of the movable side cavity (5). A cam slide (10) that moves forward and backward by an external force is arranged between the movable side mold plate (7) and the receiving plate (9) provided below it. The cam slide (10) slides on the inclined back surface of the locking block (8) to adjust the clearance (t) between the movable side mold plate (7) and the receiving plate (9). In FIG. 3, (11) is a slide core, (12) is a fixed mold plate, and (13) is a slide core moving angular pin fixed to the fixed mold plate.

In the method of molding the resin pulley, the cam slide (10) is inserted forward by an external force, and a clearance (t) of several millimeters is generated between the movable side mold plate (7) and the receiving plate (9) to move the mold. The mold is closed with the side cavity retracted, and the molding material is filled in the cavity (FIG. 7A).
After that, the cam slide (10) is retracted by an external force,
By re-pressurizing in this state, the movable side mold plate (7) and the receiving plate (9) come into close contact with each other, and the movable side cavity (5) fixed to the receiving plate (9) rises to a predetermined position of the final shape of the pulley. Then, the molding material filled in the cavity is compressed (FIG. 7B). With this method, the influence of the decrease in the strength of the weld portion can be minimized.

In the pulley forming method of the present invention, a side gate method or a multi-point pinpoint gate method can be adopted. However, when the side gate method is adopted, residual stress around the gate is smaller than that of the pinpoint gate. Therefore, swelling in the vicinity of the gate does not easily occur, the molding cycle can be shortened, and a large number can be taken, which is preferable. In this case, a gate seal pin is further provided to perform gate sealing after filling, and when this is operated forward, the internal pressure of the cavity is kept constant at its peak value.
The effect is further recognized to improve the strength of the weld part. Also,
When molding a pulley having a hole, it is advisable to form a hole in the pulley by advancing a gate seal pin to perform gate sealing at the same time as the step of forming the hole after the molding material is filled is advanced. By performing such injection compression molding, the strength of the weld portion can be significantly improved.

[0013]

According to the method of molding the resin pulley of the present invention, it is possible to almost completely prevent the decrease in strength due to the weld. Further, if side gates are adopted, the molding cycle can be shortened and a large number of pieces can be taken, so that the productivity can be improved and the sprue and runner, which is a waste material, can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a resin pulley injection compression molding die of the present invention.

FIG. 2 is a cross-sectional view showing an example of a mold for molding a resin pulley having a hole in a disc portion.

FIG. 3 is a sectional view of an example of a resin pulley injection compression molding die structure of the present invention (a sectional view perpendicular to FIG. 1).

FIG. 4 is a plan view of a pulley molded by a conventional injection molding method, showing the positions of a gate and a weld portion.

[Explanation of symbols]

 1,21 Insert metal fitting 2 Fixed side cavity 3 Metal fitting set pin 4 Metal fitting holding pin 5,15 Movable side cavity 6,16 Gate seal pin 7 Movable side mold plate 8 Locking block 9 Receiving plate 10 Cam slide 11 Slide core 12 Fixed side mold Plate 13 Angular pin 17 Pin for forming a hole 20 Pinpoint gate 22 Weld portion 23 Hole t Clearance

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Claims (2)

[Claims] 1. A method for molding a resin pulley in which a cylindrical insert fitting is embedded, wherein the insert fitting is set in a cavity, and the movable side cavity is at a predetermined distance from a predetermined position for forming a final molded product shape of the pulley. A method of injection compression molding a resin pulley, characterized in that the mold is closed when the mold is in a retracted state, the molding material is injected and filled in the cavity, and then the movable side cavity is advanced to the predetermined position. 2. A method of molding a resin pulley in which a cylindrical insert fitting is embedded and which has a hole in a disk portion,
The movable cavity is retracted by a certain distance from the predetermined position for forming the final molded product shape of the pulley,
And when the piece for forming the hole is retracted from the predetermined position, the mold is closed, the molding material is injected and filled in the cavity, and then the piece for forming the hole is advanced to the predetermined position, At the same time as or after this, the movable side cavity is advanced to the predetermined position, which is an injection compression molding method for a resin pulley.