JP3087997B2 - Injection molding method for resin molded product and injection mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method and a molding die for a resin molded product capable of accurately molding a resin molded product having a gas channel portion.

[0002]

2. Description of the Related Art In general, injection moldings of synthetic resin are often used for interior parts and weak electric parts of automobiles. For example, a door pocket installed below the surface of an automobile door trim is shown in FIG. As described above, the door pocket 1 is formed into a required shape by injection-molding a synthetic resin such as a PP resin or an ABS resin.
Along the a, a hollow gas channel portion 2 is formed to enhance the rigidity.

As a method for forming the gas channel portion 2 in the door pocket 1, an injection mold shown in FIG. 11 is usually used.

That is, the molding die is composed of a cavity die 3 and a core die 4, and has a sprue 3a and an entrance gate 3b.
The molten resin is injected and filled into the cavity C through the opening to form a door pocket 1 having the shape shown in FIG. 10. In order to form the gas channel portion 2, the molten resin is filled into the cavity C and then the core mold is formed. The gas is injected through a gas nozzle 5 installed in the nozzle 4, and the surplus resin in an unsolidified state is spilled out through an outlet gate 3 c while leaving the frame, and is stored in a discharge resin storage cavity 6. It is formed.

When the molten resin is injected and filled into the cavity C, a shut-off valve 7 is provided to prevent the material from leaking to the outside through the outlet gate 3c. At the time of filling, the outlet gate 3c is closed, and when injecting gas from the gas nozzle 5, the shut-off valve 7 is in an open state, and excess resin corresponding to the gas channel portion 2 is discharged from the discharge resin housing cavity 6 through the outlet gate 3c. To be housed.

A method of injection molding the door pocket 1 having the gas channel portion 2 using the above-described molding die will be described with reference to a time chart shown in FIG. 12 and a configuration explanatory diagram shown in FIGS.

First, as shown in FIG. 13, after the cavity mold 3 and the core mold 4 are clamped, a molten resin is injected into the cavity C formed between the molds 3 and 4 through the sprue 3a and the entrance gate 3b. Injection filling is performed. At this time, the shut-off valve 7 is at the upper position, and regulates the outlet gate 3c to a closed state.

After the injection and filling of the molten resin is completed, a secondary pressure is applied for a predetermined time, and thereafter, as shown in FIG. Is injected at a predetermined pressure, and the non-solidified molten resin other than the frame portion is stored in the discharge resin storage cavity 6 through the outlet gate 3c.

After that, as shown in FIG. 15, the door pocket 1 provided with the gas channel portion 2 is pushed upward at the same time as the mold is opened by the ejector pin 8, and the door pocket 1 may be removed.

[0010]

However, in the conventional injection molding method and the injection molding die for a resin molded article having a gas channel portion, a molten resin which has not been solidified to form the gas channel portion 2 is discharged. Gate 3c
To be contained in the discharge resin containing cavity 6 through
It is necessary to open the shut-off valve 7 and inject gas from the gas nozzle 5 before the outlet gate 3c is solidified and closed. Particularly, since the outlet gate 3c is thin, it is very difficult to control this timing. .

For this reason, there are restrictions on the secondary pressure and the cooling time after injection filling of the molten resin.
However, it is difficult to control the thickness of the gate, and it is necessary to set the gate cross section and the gate land to optimum conditions by trial and error.

Further, when the gate portion is cut, the hole of the exit gate 3c remains as a product mark, and there is a problem in appearance.

The present invention has been made in view of such circumstances, and in a method of injection molding a resin molded article having a gas channel portion and an injection molding die, the secondary pressure and the cooling time during injection molding are added. It is an object of the present invention to provide an injection molding method and an injection molding die for a resin molded product that can eliminate restrictions, easily control the thickness of a gas channel portion, and obtain good appearance quality of a product surface. .

[0014]

In order to achieve the above object, the present invention provides a method comprising the steps of: injecting a molten resin into a cavity formed by a cavity mold and a core mold; and injecting a gas into the cavity through a gas nozzle. Then, by discharging the excess resin in the cavity to the outside through the exit gate, in the injection molding method of a resin molded product having a gas channel portion, a valve gate pin that moves forward and backward is installed in the exit gate, When filling the cavity with molten resin through the inlet gate, the valve gate pin enters the cavity, closes the exit gate, and after filling the molten resin, the valve gate pin is used to inject gas into the cavity through the gas nozzle. By retreating and opening the exit gate, surplus resin passes over the ejector pin through the exit gate. It is characterized in that they contain the location evacuation resin receiving cavity.

Further, the present invention comprises a cavity mold and a core mold. After filling the cavity between the molds with a molten resin, a gas is injected into the cavity through a gas nozzle to form a resin having a gas channel portion. In an injection mold for molding a molded product, an inlet gate for supplying molten resin into the cavity and an outlet gate for discharging excess resin to the outside to form a gas channel portion are set,
A valve gate pin that moves forward and backward in the exit gate by a cylinder is installed in the exit gate,
The discharge resin storage cavity communicates with the exit gate and is set above an ejector pin that can move up and down.

Here, the method of the present invention and the molding die according to the present invention are applied to a door pocket having a gas channel portion on an upper edge, a door trim having a gas channel portion on at least a part of a peripheral edge, and the like. No.

Next, the molding die apparatus according to the present invention comprises a core mold and a cavity mold which can be mutually clamped and opened, and is set on a sprue provided in the cavity mold and a parting surface of both molds. The molten resin is injected and filled into the cavity formed between the cavity mold and the core mold through the formed entrance gate, whereby a molded product having a required shape is injection-molded.

In the spill-out structure for forming a gas channel in a resin molded product, a gas nozzle for injecting nitrogen gas or the like into a cavity for forming a gas channel is provided in a core mold. An outlet gate for discharging the non-solidified molten resin other than the frame portion to the outside, and a discharge resin storage cavity for storing the discharge resin are installed, but are inserted into the outlet gate, and inside the outlet gate. A valve gate pin that moves forward and backward is set, and the discharge resin housing cavity is provided above an vertically movable ejection pin.

The valve gate pin is a cylinder,
For example, a cylinder such as an air cylinder, a hydraulic cylinder, or the like moves forward and backward within the exit gate at appropriate timing.

That is, at the time of injection filling of the molten resin, the valve gate pin has its tip inserted into the cavity, the exit gate is completely closed, and nitrogen gas is injected from the gas nozzle into the cavity. In this case, the valve gate pin is retracted, and the cavity, the exit gate, and the discharge resin storage cavity are in communication.

The exit gate may be set on the parting surface between the cavity mold and the core mold. However, it is also possible to set the exit gate in a core mold such as a submarine gate and a nose gate. It is also possible to install on the outer peripheral surface of the pin.

Further, the valve gate pin is provided with a tapered tip so that heat accumulation can be increased, and it is desirable to minimize the formation of a skin layer by cooling the resin, and to heat the self (self-heating element). It is also possible to prevent the skin layer from being formed at the tip of the pin.

As is apparent from the above configuration, according to the present invention, after injecting and filling the molten resin into the cavity, when injecting the gas into the cavity through the gas nozzle, the valve gate pin is pulled out by a sliding operation, and the frame ( In order to form the minimum necessary passage for guiding the excess resin in the gas channel forming part) to the outside of the discharge resin housing cavity at the exit gate, the cooling time and the secondary pressure are not the same as in the conventional injection molding conditions but in the same manner as in the conventional injection molding conditions. Can be freely controlled.

Further, the ejector pins forming the discharge resin accommodating cavity can be moved up and down to control the amount of the discharged resin, so that the surplus resin is filled in the discharged resin accommodating cavity just before the gas flows into the outlet gate. , The hole of the gas path by the exit gate does not open on the product surface.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an injection molding method and an injection mold for a resin molded product according to the present invention will be described.
This will be described in detail with reference to the accompanying drawings.

FIG. 1 is a partially cutaway perspective view of a door pocket formed by applying the method of the present invention, FIG. 2 is a schematic view showing the configuration of an injection mold used in the method of the present invention, and FIG. 4 to 6 are cross-sectional views showing each step of the method of the present invention, and FIGS. 7 to 9 are cross-sectional views showing another embodiment of a molding die used in the method of the present invention.

First, FIG. 1 shows a door pocket 10 formed by applying the method of the present invention.
A frame 13 having a gas channel portion 12 is formed along the upper edge portion 11 where rigidity is required by molding a general-purpose thermoplastic resin such as resin or ABS resin by injection molding. Thus, the frame 13 maintains strong rigidity by giving a desired section modulus without causing sink marks on the surface.

Next, FIG. 2 shows an embodiment of a molding die used for molding the door pocket 10, particularly showing a portion where a gas channel portion 12 is formed.

That is, the injection mold includes a movable cavity mold 20 having a desired mold surface and capable of moving a predetermined stroke, and a fixed core mold 30 having a desired mold surface. 2 shows a state in which the cavity mold 20 is clamped to the core mold 30.
Reference numeral 0 denotes a sprue 21 for supplying the molten resin, and an inlet gate 2 for supplying the molten resin from the sprue 21 to a cavity C formed between the cavity mold 20 and the core mold 30.
2 is formed on the parting surface of both dies 20 and 30.

Further, the core mold 32 is provided with a gas nozzle 31 for injecting nitrogen gas or the like into the cavity C, and after molding, ejector pins 32, 33 for ejecting the molded product in conjunction with the mold opening operation. is set up.

Incidentally, the present invention is characterized by a spill-out structure in the gas injection method.

That is, in order to form the gas channel portion 12, an outlet gate 23 communicating with the cavity C is provided with a cavity mold 20 as a structure for discharging excess resin to the outside.
A discharge resin accommodating cavity 34 which is formed on the parting surface of the core 30 and the outlet die 23 is set above an ejector pin 33 which can move up and down. A valve gate pin 42 is provided on the slider 41 of the cylinder 40 so as to be able to advance and retreat.

More specifically, the valve gate pin 42 provided on the slider 41 has a diameter substantially the same as the diameter of the exit gate 23. When the operation of the cylinder 40 causes the slider 41 to extend, the valve gate pin 42 The tip of 42 enters the cavity C and completely closes the outlet gate 23. In this state, the cavity C is injected and filled with the molten resin, and a secondary pressure is applied.

When the gas is injected into the cavity C through the gas nozzle 31, the slider 41 is retracted by the operation of the cylinder 40 to smoothly discharge the molten resin to the outside, whereby the valve gate pin 42 is also retracted. Then, the excess resin is discharged from the cavity C through the exit gate 23 into the discharge resin storage cavity 34 above the ejector pins 33.

Next, a process of forming the door pocket 10 having the gas channel portion 12 using the above-described molding die will be described with reference to a time chart shown in FIG. 3 and FIGS.
The configuration will be described in detail with reference to FIG.

That is, as is clear from the time chart of FIG. 3, the method of the present invention performs the mold clamping and opening operations of the cavity mold 20 and the core mold 30 and the operation of the valve gate pin 42.
It suffices to control the timing of the operation of moving back and forth into the cavity C.

First, in the injection molding shown in FIG.
The cavity mold 20 is in a clamped state with respect to the core mold 30, and the cavity C is formed through the sprue 21 and the entrance gate 22.
The molten resin P is injected and filled therein, and a predetermined secondary pressure is applied for a predetermined time.

At this time, the valve gate pin 42 has entered the exit gate 23, the tip of the valve gate pin 42 is located in the cavity C, and the exit gate 23 is completely closed.

If the tip of the valve gate pin 42 is tapered to increase heat accumulation, the formation of a skin layer by cooling the resin can be reduced as much as possible.

Next, after injecting and filling the molten resin P into the cavity C and applying a secondary pressure, as shown in FIG. 5, the operation of the cylinder 40 causes the slider 41 to retreat and the valve gate pin 42 to move the valve gate pin 42 to the cavity C. The excess resin P2 which is pulled out from the inside and excluding the cooled and solidified resin P1 (corresponding to the frame 13) in the cavity C is discharged into the discharge resin containing cavity 3
A gas such as nitrogen gas is injected into the cavity C through the gas nozzle 31 at the same time as opening the minimum necessary passage for accommodating the gas in the cavity 4.

At this time, since the vertical stroke of the ejector pin 33 is variable, the volume of the discharge resin accommodating cavity 34 can be freely adjusted, thereby controlling the diameter of the gas channel portion 12, that is, the thickness control of the frame 13. Can be easily performed.

Further, if control is performed so that the excess resin P2 is filled in the discharge resin accommodating cavity 34 immediately before the gas flows into the exit gate 23, a hole of the gas path is not opened in the exit gate 23 portion, and the minimum number of gates is reduced. Only a trace is left.

It should be noted that it is also possible to prevent the skin layer from being formed at the tip of the pin 42 by heating the valve gate pin 42 itself or by using a self-heating element.

Thereafter, as shown in FIG. 6, the cavity mold 20 is moved and the ejector pins 32 and 33 are moved.
Is stroked upward to complete the molding of the door pocket 10. At this time, burrs corresponding to the exit gate 23 and the discharge resin accommodating cavity 34 are formed in the door pocket 10, but if gate cut processing is performed, Only a very small gate mark remains on the molded product and does not give any bearing to the appearance.

As described above, according to the method of the present invention, the surplus resin P2 is guided into the discharge resin accommodating cavity 34 by movably inserting the valve gate pin 42 into the exit gate 23 for discharging the surplus resin P2. Since the minimum passage is formed, the cooling time, the secondary pressure, and the like can be freely controlled, the surface gloss can be prevented, the gas can be prevented from flowing into general parts, and the thickness of the frame 13 can be controlled. Easy to do,
There is an advantage that the molding accuracy is excellent, a hole is not opened in the gate portion, and a minimal gate mark remains, and the appearance defect is also minimized.

FIGS. 7 to 9 show another embodiment of a molding die used in the present invention.
The valve gate pin 42 is inserted into the
7 and 8 is the same as the above-described embodiment, except that the exit gate 23 is not a parting line surface as described above, but is a core type as a submarine gate 23a. 30 is a perforated structure.

In this embodiment, as shown in FIG. 8, when the molded product is released from the mold, the submarine gate 23a can be removed from the resin by elasticity of the resin. Thereby, the gate mark can be set at a place where the gate mark is not conspicuous, and the appearance design can be improved.

Further, as shown in FIG. 9, an exit gate 23b may be provided on the outer periphery of the ejector pin 33, and a valve gate pin 42 may be installed in the exit gate 23b so as to be vertically movable. In this case, there is an advantage that the gate mark is not conspicuous outside and the appearance of the product is improved.

Although the above-described embodiment is directed to the door pocket 10 having the gas channel portion 12, the interior portion of the vehicle such as a door trim having a gas channel portion for enhancing rigidity or the like at a part of a peripheral edge thereof, or the like. Alternatively, the present invention can be effectively applied to injection molded products used for light electric parts, consumer appliances, and the like, and has a wide range of application. Therefore, the practical value of the present invention can be said to be extremely high.

[0050]

As described above, the present invention has the following special functions and effects.

(1) According to the present invention, in order to discharge surplus resin for forming a gas channel portion out of the cavity,
The valve gate pin is inserted into the exit gate between the cavity and the discharge resin storage cavity so as to be able to advance and retreat, and the minimum necessary gas passage is opened in the exit gate. It is possible to freely control the time and the like, and it is possible to prevent uneven surface gloss and gas from flowing into a general portion, thereby greatly improving the molding accuracy.

(2) According to the present invention, the amount of discharged resin can be freely controlled by installing the discharged resin accommodating cavity for storing the surplus resin above the vertically movable ejector pins. Can be performed freely.

(3) According to the present invention, the excess resin forming the gas channel portion is stored in the discharge resin storage cavity through the outlet gate by inserting the valve gate pin into the outlet gate and retracting the valve gate pin. Therefore, if control is performed so that the excess resin is filled in the discharge resin storage cavity just before gas flows into the exit gate, a hole in the exit gate gas path is not opened, and a minimum gate trace is formed. This has the effect that the appearance of the gate cut mark is improved compared to the conventional one.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing a door pocket formed by applying the method of the present invention.

FIG. 2 is a sectional view showing a schematic configuration of an injection mold according to the present invention.

FIG. 3 is a time chart of the method of the present invention.

FIG. 4 is a sectional view showing a state of injection filling of a molten resin in the method of the present invention.

FIG. 5 is a sectional view showing a state at the time of gas injection in the method of the present invention.

FIG. 6 is a sectional view showing an ejector state after molding in the method of the present invention.

FIG. 7 is a sectional view showing another embodiment of a molding die used in the method of the present invention.

FIG. 8 is a sectional view showing an ejector state in a molding method using the molding die shown in FIG. 7;

FIG. 9 is a sectional view showing still another embodiment of a molding die used in the method of the present invention.

FIG. 10 is a sectional view showing a conventional door pocket.

FIG. 11 is a schematic cross-sectional view showing an injection mold using a conventional gas injection method.

FIG. 12 is a time chart showing a conventional injection molding method.

FIG. 13 is a sectional view showing a state of filling a molten resin in a conventional injection molding method.

FIG. 14 is a cross-sectional view showing a gas injection state in a conventional injection molding method.

FIG. 15 is a sectional view showing an ejector state of a molded product in a conventional injection molding method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Door pocket 12 Gas channel part 13 Frame 20 Cavity type 22 Inlet gate 23 Outlet gate 30 Core type 31 Gas nozzle 32, 33 Ejector pin 34 Discharge resin accommodation cavity 40 Cylinder 42 Valve gate pin C cavity P Molten resin P1 Cooling solidified resin P2 Surplus resin

Claims (3)

(57) [Claims] 1. A cavity mold (20) and a core mold (30).
The molten resin (P) in the cavity (C) composed of
Is injected and filled into the cavity (C) through a gas nozzle (31), and the excess resin (P2) in the cavity (C) is discharged to the outside through an exit gate (23). In the injection molding method for a resin molded product formed by (12), a valve gate pin (42) which moves forward and backward is installed in the outlet gate (23), and is inserted into the cavity (C) through the inlet gate (22). When filling the molten resin (P), the valve gate pin (42) enters the cavity (C), closes the outlet gate (23), and after filling the molten resin (P), the cavity (31) is passed through the gas nozzle (31). When injecting gas into C), the valve gate pin (42) is retracted and the outlet gate (23) is opened, so that the excess tree is discharged through the outlet gate (23). A method of injection-molding a resin molded product, wherein a fat (P2) is stored in a discharge resin storage cavity (34) provided above an ejector pin (33). 2. A cavity mold (20) and a core mold (30).
After filling the cavity (C) between the two molds with the molten resin (P), a gas is injected into the cavity through a gas nozzle (31) to form a gas channel (12).
In order to form an inlet gate (22) for supplying a molten resin (P) into a cavity (C) and a gas channel portion (12) in an injection molding die for molding a resin molded product (10) provided with An exit gate (23) for discharging excess resin (P2) to the outside is set, and a valve gate pin (4) that moves forward and backward in the exit gate (23) by a cylinder (40).
An ejector pin (33) is provided in the outlet gate (23) and the discharge resin storage cavity (34) communicating with the outlet gate (23) is movable up and down.
An injection mold for a resin molded product, which is set upward. 3. The injection mold according to claim 2, wherein a tip portion of the valve gate pin (42) is tapered.