JP2000176971A - Annular molded product, method for injection-molding annular molded product and injection molding die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for injection-molding an annular molded product by which the sectional area of a gate can be increased and resin can be supplied into a cavity smoothly and rapidly and at the same time, the flow of resin in the cavity can be smoothed and the resin can be uniformly spread to every part of the cavity of obtain a homogeneous product as well as an annular molded product. SOLUTION: A gate mark is cleanly molded by forming the end face 1D of an annular body 1E by the movable pin 27 of a valve gate and the end face 1D of the annular body 1E is borne by the movable pin 27, so that the gate mark is inconspicuous hence no problem with an appearance. In addition, the flow of resin in the annular body 1E (a cavity 12) during molding is regulated in the one to other end face direction. Consequently, the resin is spread to every part of the annular body 1E smoothly and uniformly. Especially the property of the annular body 1E around the circumference is maintained homogeneously on the plane orthogonal to the axial line of the annular body 1E.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an annular molded article such as a hollow gear having a central hole therein, an injection molding method thereof, and an injection mold.

[0002]

2. Description of the Related Art Conventionally, when this kind of annular molded product is injection-molded, a cavity for an annular molded product is provided between a fixed mold plate and a movable mold plate to correspond to one end surface of the annular molded product. A pin point gate is provided on the fixed mold plate at a position where the molten resin is supplied into the cavity through the pin point gate, or near the mating surface (parting line) between the fixed mold plate and the movable mold plate. A tunnel gate (submarine gate) is provided at a position corresponding to the outer peripheral surface of the annular molded product, and the molten resin is supplied into the cavity through the tunnel gate to form the annular molded product. Was.

[0003]

When the conventional annular molded product is injection-molded, a large gate diameter is required because the pinpoint gate or the tunnel gate is used as described above. Difficult,
When the amount of the resin supplied into the cavity is to be increased or when the resin is to be supplied into the cavity quickly, there is a dissatisfaction that it is not possible to respond flexibly. In addition, since it is difficult to set the gate position at the symmetrical position (line symmetry or point symmetry) of the annular molded product as a product, it is difficult for the resin supplied from the gate to flow smoothly in the cavity, and the inside of the cavity is hardly formed. There has been a problem that it is difficult to obtain a uniform product depending on the shape of the product, because the product does not reach all parts uniformly.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a large gate cross-sectional area so that resin can be supplied smoothly and quickly into a cavity. At the same time, the flow of the resin in the cavity can be smoothed, the resin can be uniformly distributed to each part of the cavity, and therefore, an annular molded product capable of obtaining a homogeneous product, its injection molding method, and An object of the present invention is to provide an injection mold.

[0005]

A first aspect of the present invention is an annular molded product formed by supplying a resin through a gate into a cavity formed between a pair of mold plates. At least a part of one end face is formed by a cylindrical movable pin that opens and closes a valve gate. According to the first aspect of the present invention, at least a part of the end surface of the annular body as a product is formed by the movable pin of the valve gate, so that the gate mark is formed neatly and serves as the end face of the annular body. Is not conspicuous, does not cause a problem in appearance, and at the time of molding, the flow of the resin in the annular body (cavity) is regulated from one end face to the other end face. The resin of each part is smoothly and uniformly distributed, and the filling of the resin is reliably performed.In particular, in a plane perpendicular to the axis of the annular body, properties around the circumference of the annular body are uniformly maintained, and therefore, quality is improved. Good products can be easily obtained. Claim 2 of the present invention is an injection molding method for molding an annular molded product by supplying a resin through a valve gate into a cavity formed between a fixed mold plate and a movable mold plate, By abutting a support pin provided on the fixed mold plate and a core pin provided on the movable mold plate, at least a center hole of the annular body is formed, and a cylindrical movable member arranged around the support pin is formed. The pin closes the valve gate and forms at least a part of one end face of the annular body. According to the second aspect, the valve gate is opened by the movable pin by moving the movable pin along the support pin in a state where the support pin and the core pin abut against each other when the mold is closed. Is supplied into the cavity, the valve gate is closed by the movable pin, and an annular body is formed in the cavity. Further, the present invention provides an injection mold for forming an annular molded product by supplying a resin through a valve gate into a cavity formed between a fixed mold plate and a movable mold plate. ,
A support pin is provided on the fixed mold plate, a core pin is provided on the movable mold plate facing the support pin, and a cylindrical movable pin for opening and closing the valve gate is provided around the support pin. While being provided movably along the axis, the support pin and the core pin are configured to abut each other when the mold is closed to form at least a center hole of the annular body, and the movable pin is provided at one end face of the annular body. Is formed so as to form at least a part of the above. According to the third aspect of the present invention, the movable mold plate is brought into contact with the fixed mold plate, and the movable pin is moved along the support pin in a state where the core pin abuts against the support pin. After the resin is supplied into the cavity, the movable pin is moved while being supported and guided by the support pin, and the valve gate is closed to form an annular body in the cavity.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a sectional view of a main part showing an example of a hot runner type injection molding die, FIG. 2 is a sectional view showing a fixed mounting plate (injection molding machine) side of FIG. 1, and FIG. 3 is a sectional view of a cavity part. is there. This injection molding die is for resin-molding a hollow gear (annular molded product) 1 having a pair of large and small gear portions 1A and 1B shown in FIGS. In the figure, reference numeral 10 denotes a fixed mold plate.
The movable mold plate 11 is provided so as to be able to approach and separate therefrom. Then, nests 10A and 11A are attached to these template plates 10 and 11, respectively.
A cavity 12 for molding the gear 1 is formed between A and 11A. A fixed mounting plate 15 is mounted on the fixed mold plate 10 via a fixed receiving plate 13 and a spacer block 14. A manifold 16 is provided between the fixed receiving plate 13 and the fixed mounting plate 15. I have.
Then, the fixed mold plate 10, the insert 10A and the fixed receiving plate 1
3, the valve body 21 of the valve gate device 20 is provided.
The temperature sensor 22 and the heater 23 are provided on the outer periphery of the distal end portion of the valve main body 21.
Further, a heater cover 24 is attached to the outer periphery of the heater 23, and a seal ring 25 is provided at a tip of the valve body 21. Furthermore, the inside of the distal end of the valve body 21 has an inner peripheral wall 21 forming a circular through hole.
A has four resin passages 21B formed at equal intervals.
Then, the molten resin is supplied to the cavity 12 through the sprue bush (not shown) mounted on the fixed mounting plate 15, the manifold 16, the inside of the valve body 21, and the gate 10B formed in the insert 10A. It has become.

The closing member 2 is provided on the upper part of the valve body 21.
The movable pin 27 is slid along the axis thereof while being supported and guided by the inner peripheral wall 21 </ b> A inside the closing member 26 and at the distal end of the valve body 21. The base end of the movable pin 27 passes through the manifold 16 and the fixed mounting plate 15. The base end of the movable pin 27 is connected to a piston of a fluid pressure cylinder 28 provided in the fixed mounting plate 15. Mounting bolt 3 on 29
0 attached. This fluid pressure cylinder 28
Have two fluid passages 31 formed in the fixed mounting plate 15.
Fluid is supplied via A and 31B, whereby the piston 29 moves together with the movable pin 27. The fixed mounting plate 15
In order to fix the fluid pressure cylinder 28, first, second and third mounting members 32, 33 and 34 are mounted by mounting bolts 35. This first mounting member 32
Is provided with a proximity switch 36 for detecting the operation of the piston 29. Further, a support pin 37 is provided inside the movable pin 27 so as to be movable along its axis, and the base end of the support pin 37 is connected to the second and third mounting members 33 and 34. It is stored in the formed space 38. The support pin 37 stored in this space 38
A spring 3 for urging the support pin 37 toward its distal end is located between the flange 37A at the base end of the third member and the third mounting member 34.
9 is mounted. A center hole 37B is formed inside the support pin 37.
By supplying the compressed air to the distal end of the support pin 37 via B, the distal end of the support pin 37 is cooled. As a cooling means of the support pin 37, a heat pipe may be used instead of air cooling. In the case of this heat pipe or in the case where compressed air can be circulated as a double passage structure inside the support pin 37,
The center hole 37B of the support pin 37 has its tip closed.

The gear 1 formed in the cavity 12
The large gear portion 1A and the small gear portion 1B are formed on the outer peripheral portion of the annular body 1E, and a ring-shaped projection 1C is formed on the end surface on the large gear portion 1A side, and the end surface 1D of the projection 1C is formed. Are formed by the distal end surface of the movable pin 27 and serve as a gate surface. Therefore, the projection 1 of the gear 1
A mark of a valve gate is formed on the end face 1D of C.
Also, a center hole 1F formed in the center of the gear 1 is
It is formed by a core pin 40 provided on the movable mold plate 11 and the support pin 37. And
The pair of large and small gear portions 1A and 1B, the projection 1C and the center hole 1F are formed concentrically with respect to the axis of the annular body 1E. Reference numeral 41 in the figure denotes a cooling passage for cooling the insert 10A.

In the injection mold having the above-described structure, the movable cylinder 2 is operated by operating the fluid pressure cylinder 28.
7 is moved along its axis, and the tip of the movable pin 27 is used to open and close the gate 10B of the insert 10A. That is, a mold in which the movable mold plate 11 is brought into contact with the fixed mold plate 10 and the core pin 40 abuts against the support pin 37 to form the cavity 12 between the inserts 10A and 11A of the mold plates 10 and 11. At the time of closing, the movable pin 27 is moved along the support pin 37 by the fluid pressure cylinder 28 to open the gate 10B. Thereby, the sprue bush (not shown), the manifold 16, the inside of the valve body 21 and the gate 10 are removed from the injection molding machine.
Through B, the molten resin is supplied to the cavity 12.
In this case, since the gate 10B is formed corresponding to the ring-shaped end face 1D of the gear 1, the molten resin flows in the cavity 12 from the end face 1D of the gear 1 to the end face on the side of the small gear portion 1B. The flow of the molten resin is smooth, and the flow of the molten resin is not disturbed. Therefore, the molten resin is uniformly and uniformly supplied to each part in the cavity 12 to be surely filled. . Next, the movable pin 27 is driven by the fluid pressure cylinder 28, and the ring-shaped gate 10B is closed by the movable pin 27. Then, after the resin in the cavity 12 is cooled and solidified, the process proceeds to a mold opening step, in which the movable mold plate 11 is separated from the fixed mold plate 10 and the core pin 40 is separated from the support pins 37, thereby cooling the cavity 12. The fixed gear 1 is attached to the movable mold plate 11
Release from 0. Subsequently, the gear 1 adhering to the movable mold plate 11 is protruded by an unillustrated ejection pin, and is released from the movable mold plate 11 side.

In this manner, the gear (annular molded product) 1 is smoothly injection molded. Here, in the opening / closing operation of the gate 10B by the movable pin 27, the movable pin 27
Since the movable pin 27 moves smoothly while being supported and guided by the support pin 37, the movable pin 27 operates smoothly and reliably.
Since the movable pin 27 closes the ring-shaped gate 10B, the resin that cannot be accommodated in the cavity 12 returns smoothly from the outer edge of the distal end of the movable pin 27 to the resin reservoir in the valve body 21. The gate 10B can be easily closed without applying a large resin resistance to the gate 27. Therefore, a gate mark appearing on the end face 1D of the projection 1C of the gear 1 obtained in the cavity 12 is not conspicuous, and a high quality molded product can be formed in the cavity 12. When the mold is closed, the support pin 37 and the core pin 40 abut each other. In this case, since the support pin 37 is urged by the spring 39, for example, the two pins 37 and 40 are strongly pushed. Even if they are combined, the impact is applied to the spring 39
Is absorbed smoothly and the pins 37 and 40 are not damaged. In addition, in a state where the both pins 37 and 40 are abutted, the support pin 37 is always urged (pressed) toward the core pin 40 by the spring 39.
As a result, the two pins 37 and 40 are firmly contacted with each other, and no gap is formed between them. No burrs or the like are generated. Further, when the core pin 40 separates from the support pin 37 at the time of opening the mold, compressed air is blown out from the tip of the support pin 37 through the center hole 37B formed in the support pin 37, so that the support pin 37 is efficiently operated. Cooling.

In the gear 1 injection-molded in this manner, as described above, the resin flowing inside during the molding moves from the end surface 1D of the projection 1C, which is the gate surface, to the end surface on the side of the small gear portion 1B. Because of the flow, each part of the gear 1 is filled with a sufficient resin, and in particular, the resin is supplied from a ring-shaped gate 10B that is arranged point-symmetrically with respect to the axis of the annular body 1E of the gear 1. In the plane perpendicular to the axis of the body 1E, the properties around the circumference of the annular body 1E are uniformly maintained, and therefore, the shape, strength, etc. of each tooth portion of the large gear portion 1A and the small gear portion 1B are uniformly formed. As a result, a good quality product can be easily obtained. Further, as described above, the gate cut at the valve gate is smoothly performed by the cylindrical movable pin 27, and the protrusion 1 of the gear 1 is formed.
To make the end face 1D of C a ring-shaped gate face, the end face 1
The gate traces appearing in D become concentric, are not conspicuous, do not cause a problem in appearance, and do not cause problems in the performance as a gear. In this embodiment, the injection molding of the hollow gear 1 has been described. However, the present invention is not limited to this, and can be widely applied to molding of an annular component. Further, in the present embodiment, during the formation of the center hole 1F of the annular body 1E, the support pin 37 bears the inner peripheral surface of the projection 1C, and the other large and small pair of gear portions 1
Although it has been described that the inner peripheral surfaces of A and 1B are taken up by the core pin 40 and molded, the present invention is not limited to this. Depending on the shape of the annular molded product, the center hole (inner peripheral surface) of the annular body is entirely covered by the core pin 40. The support pins 37
May be configured to only support the core pin 40 by abutting it.

[0012]

As described above, according to the first aspect of the present invention,
According to the, by forming at least a part of the end face of the annular body as a product by the movable pin of the valve gate,
The gate is smoothly closed, the gate is cut reliably, and therefore the gate trace is formed neatly and bears the end surface of the annular body.The gate trace is integrated with the shape of this end surface, and the gate trace is formed. It is not noticeable, does not cause a problem in appearance, and has an annular body (cavity) during molding.
Since the flow of the resin inside is restricted from one end face to the other end face, the resin smoothly and uniformly spreads over each part of the annular body, and the resin filling of each part is surely performed. The properties around the circumference of the annular body are uniformly maintained in a plane perpendicular to the axis of the circle, so that a good quality product can be easily obtained. According to the second aspect of the present invention, the valve gate is opened and closed by the movable pin by moving the movable pin along the support pin with the support pin and the core pin abutting each other when the mold is closed. Therefore, since the movable pin reciprocates while being supported and guided by the support pin, the movable pin can be operated smoothly and reliably. In addition, since the gate is closed by the cylindrical movable pin, excess resin smoothly returns to the resin passage through the outer edge of the movable pin, so that even if the gate has a large diameter, a large resin resistance can be obtained. The movable pin can be easily operated without receiving, and the gate can be reliably closed by the movable pin. Therefore, the amount of resin supplied into the cavity can be greatly increased, and the resin can be quickly supplied into the cavity, and the gate can be easily and smoothly closed, so that a high quality molded product can be obtained. Can be reliably obtained.
Further, according to the third aspect of the present invention, the movable mold plate is brought into contact with the fixed mold plate, and the movable pin is moved along the support pin while the core pin is in contact with the support pin. After the resin is supplied into the cavity by opening the valve gate, the movable pin is moved while being supported and guided by the support pin to close the valve gate, whereby the annular body is smoothly formed in the cavity. be able to. Therefore, by performing the opening and closing operation of the gate with the movable pin supported and guided by the support pin, the operation of the movable pin can be made more stable, and the tree finger resistance applied to the movable pin can be reduced. The movable pin can be moved smoothly. As a result, the gate opening and closing operation can be performed smoothly and reliably, and a high-quality annular body can be easily formed in the cavity.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing one embodiment of an injection mold.

FIG. 2 is a sectional view showing a fixed mounting plate (injection molding machine) side of FIG.

FIG. 3 is a sectional view of a cavity portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gear (annular molded product) 1A Large gear part 1B Small gear part 1C Projection 1D End surface (gate surface) 1E Annular body 1F Center hole 10 Fixed mold plate 10A, 11A Insert 10B Gate 11 Movable plate 12 Cavity 27 Movable pin 37 Support pin 40 Core pin

Claims (3)

[Claims] An annular molded product formed by supplying a resin through a gate into a cavity formed between a pair of mold plates, wherein at least a part of one end surface of the annular body is provided with a valve gate. An annular molded product formed by a cylindrical movable pin that opens and closes a ring. 2. An injection molding method for molding an annular molded product by supplying a resin through a valve gate into a cavity formed between a fixed mold plate and a movable mold plate. The supporting pin provided and the core pin provided on the movable mold plate are abutted to form at least a center hole of the annular body, and the valve is formed by a cylindrical movable pin disposed around the supporting pin. A method for injection-molding an annular molded product, comprising closing a gate and molding at least a part of one end surface of the annular body. 3. An injection mold for forming an annular molded product by supplying a resin through a valve gate into a cavity formed between a fixed mold plate and a movable mold plate, wherein the fixed mold plate is provided. A support pin is provided, a core pin is provided on the movable mold plate facing the support pin, and a cylindrical movable pin that opens and closes the valve gate is provided around the support pin along an axis thereof. While being provided movably, the support pin and the core pin are configured to abut each other when the mold is closed to form at least a center hole of the annular body, and the movable pin is at least part of one end face of the annular body. An injection-molding mold for an annular molded product, characterized in that the injection-molding die is configured to mold a molded product.