JPH09323335A - Method for injection molding of resin molding and injection mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to accurately control the thickness of a gas channel by enhancing the molding accuracy in a method for injection molding of a resin molding and an injection mold adopting a gas injection process. SOLUTION: The method for injection molding a resin molding comprises the steps of inserting a valve gate pin 42 telescopically operated by a cylinder 40 into an outlet gate 23, advancing the end of the pin 42 inserted into the gate 23 into a cavity C at the time of injection molding to effectively block the gate 23, retreating the pin 42 at the time of injecting gas, forming a gas passage of minimum limit at the gate 23, and discharging excess resin in the exhaust resin containing cavity 34 set above a vertically movable ejector pin 33, thereby controlling the discharged resin amount to accurately controlling the thickness of a gas channel.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Generally, a synthetic resin injection-molded product is often used for automobile interior parts, light electric parts, etc. For example, a door pocket installed under the surface of an automobile door trim is shown in FIG. As described above, a synthetic resin such as PP resin or ABS resin is injection-molded to have a desired shape, and the door pocket 1 has its upper edge 1
A hollow gas channel portion 2 is formed along a to enhance rigidity.

As a method of 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 inlet gate 3b.
The molten resin is injected and filled in through the cavity C to form the door pocket 1 having the shape shown in FIG. 10. However, in order to form the gas channel portion 2, after the molten resin is filled in the cavity C, the core mold is formed. The gas is injected through the gas nozzle 5 installed in No. 4 and the excess resin in an unsolidified state leaving the frame is spilled out through the outlet gate 3c and accommodated in the discharged resin accommodating cavity 6, whereby the gas channel portion 2 is formed. It is formed.

A shut-off valve 7 is provided in order to prevent the material from leaking to the outside through the outlet gate 3c when the cavity C is injected and filled with molten resin. The outlet gate 3c is closed at the time of filling, and when the gas is injected from the gas nozzle 5, this shut-off valve 7 is in an open state, and excess resin corresponding to the gas channel portion 2 is discharged through the outlet gate 3c into the discharge resin accommodating cavity 6. Housed in.

An injection molding method of the door pocket 1 having the gas channel portion 2 using the above molding die will be described with reference to the time chart diagram shown in FIG. 12 and the configuration explanatory diagrams shown in FIGS. 13 to 15.

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

After the injection filling of the molten resin is completed, a secondary pressure is applied for a predetermined time, and thereafter, as shown in FIG. 14, the shutoff valve 7 is opened and the inside of the cavity C is passed through the gas nozzle 5. Nitrogen gas is press-fitted into the discharge resin storage cavity 6 through the outlet gate 3c through the outlet gate 3c.

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

[0010]

However, in the conventional injection molding method and the injection molding die for the resin molded product having the gas channel portion, the molten resin which is not solidified to form the gas channel portion 2 is discharged. Gate 3c
To be accommodated in the discharged resin accommodating cavity 6 through
It is necessary to open the shutoff valve 7 and inject gas from the gas nozzle 5 before the outlet gate 3c is solidified and blocked. Especially, since the outlet gate 3c is thin, it is very difficult to control the timing. .

Therefore, there are restrictions on the secondary pressure and the cooling time after injection and filling of the molten resin, and the gas channel section 2
It was also difficult to control the wall thickness at the time, and it was necessary to set the gate cross section and gate land to the 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, which causes a problem in appearance.

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

[0014]

In order to achieve the above object, the present invention is to inject a molten resin into a cavity composed of a cavity mold and a core mold, and then inject a gas into the cavity through a gas nozzle. Then, by discharging the excess resin in the cavity to the outside through the outlet gate, in the injection molding method of the resin molded product forming the gas channel portion, the valve gate pin that moves back and forth is installed in the outlet gate, When filling the cavity with molten resin through the inlet gate, enter the valve gate pin into the cavity, close the outlet gate, and after filling the molten resin, inject gas into the cavity through the gas nozzle, use the valve gate pin. By retracting and opening the exit gate, the excess resin will move above the ejector pin through the exit gate. It is characterized in that they contain the location evacuation resin receiving cavity.

Furthermore, the present invention comprises a cavity type mold and a core type mold, and after filling the cavity between the molds with a molten resin, a gas is injected into the cavity through a gas nozzle to provide a resin having a gas channel section. In an injection molding die for molding a molded product, an inlet gate for supplying a molten resin into the cavity and an outlet gate for discharging a surplus resin to form a gas channel portion are set,
A valve gate pin that moves back and forth in the outlet gate by a cylinder is installed in the outlet gate, and
It is characterized in that the discharge resin housing cavity is set above the ejector pin which can move up and down, in communication with the outlet gate.

Here, the objects to which the method of the present invention and the molding die according to the present invention are applied include a door pocket having a gas channel portion on the upper edge, a door trim having a gas channel portion on at least a part of its peripheral edge, and the like. Can be mentioned.

Next, the molding die apparatus according to the present invention comprises a core mold and a cavity mold which can be clamped and opened to each other, and set on the sprue provided on the cavity mold and the 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 inlet gate thus formed, so that a molded product having a required shape is injection molded.

In the spill-out structure for forming the gas channel portion in the resin molded product, a gas nozzle for injecting nitrogen gas or the like into the cavity forming the gas channel portion is installed in the core type. 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. The valve gate pin that moves forward and backward is set, and the discharge resin housing cavity is provided above the vertically movable ejection pin.

The valve gate pin is a cylinder,
For example, a cylinder such as an air cylinder or a hydraulic cylinder moves forward / backward in the outlet gate at an appropriate timing.

That is, when the molten resin is injected and filled, the tip of the valve gate pin enters the cavity and the outlet gate is completely closed, and nitrogen gas is injected into the cavity from the gas nozzle. In doing so, the valve gate pin is retracted, and the cavity, the outlet gate, and the discharge resin accommodating cavity are in communication with each other.

The outlet gate may be set on the parting surface of the cavity type and the core type, but it may be installed in the core type like a submarine gate or a nose gate, and the ejector may be installed. It is also possible to install it on the outer peripheral surface of the pin.

Further, it is desirable that the valve gate pin can have a large amount of heat accumulation by installing the tip in a tapered shape, and the skin layer formation due to resin cooling can be reduced as much as possible, and by heating itself (self-heating element). It is also possible that the skin layer is not formed on the tip of the pin.

As is apparent from the above structure, according to the present invention, after injecting and filling the cavity with the molten resin, when injecting the gas into the cavity through the gas nozzle, the valve gate pin is pulled out by the sliding operation to remove the frame ( Since the minimum required passage that guides the excess resin inside the gas channel forming part) to the outside discharge resin storage cavity is formed at the exit gate, cooling time and secondary pressure are the same as in conventional injection molding conditions instead of gas injection. Etc. can be controlled freely.

Further, the ejector pin forming the discharge resin storage cavity can be moved up and down to control the discharge resin amount so that the excess resin is filled in the discharge resin storage cavity just before the gas flows into the outlet gate. If it is controlled to, the hole of the gas path by the exit gate does not open on the product surface.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an injection molding method for a resin molded product and an injection molding die according to the present invention will be described below.
A detailed description will be given 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 structure of an injection molding die used in the method of the present invention, and FIG. 3 is the method of the present invention. 4 is a sectional view showing each step of the method of the present invention, and FIGS. 7 to 9 are sectional views showing another embodiment of the 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 general-purpose thermoplastic resin such as resin or ABS resin is molded into a required shape by injection molding, and a frame 13 having a gas channel portion 12 is formed along an upper edge portion 11 requiring rigidity. The frame 13 maintains a strong rigidity by giving a desired section modulus without causing a sink mark on the surface.

Next, FIG. 2 shows an embodiment of a molding die used for molding the door pocket 10, and particularly shows a portion forming the gas channel portion 12.

That is, the injection molding die comprises a movable cavity die 20 having a desired die surface and capable of moving by a predetermined stroke, and a fixed core die 30 having the desired die surface. 2 shows a state in which the cavity mold 20 is clamped with respect to the core mold 30.
0 is a sprue 21 for supplying the molten resin, and an inlet gate 2 for supplying the molten resin from the sprue 21 into a cavity C formed between the cavity mold 20 and the core mold 30.
2 is formed on the parting surface of both molds 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 ejector pins 32, 33 for ejecting a molded product in cooperation with the mold opening operation after molding. is set up.

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

That is, in order to form the gas channel portion 12, as a structure for discharging the surplus resin to the outside, the outlet gate 23 communicating with the cavity C has the cavity mold 20.
The discharge resin storage cavity 34, which is formed on the parting surface of the core mold 30 and communicates with the outlet gate 23, is set above the ejector pin 33 that can move up and down. A valve gate pin 42 is provided on a slider 41 of the cylinder 40 so that the valve gate pin 42 can be inserted into and out of the cylinder 41.

More specifically, the valve gate pin 42 installed on the slider 41 has a diameter substantially the same as the diameter of the outlet gate 23, and if the slider 41 is extended by the operation of the cylinder 40, the valve gate pin 42 will be expanded. The tip of 42 enters the cavity C and completely closes the outlet gate 23. In this state, the molten resin is injected and filled in the cavity C, and the 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 in order 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 outlet gate 23 into the discharge resin storage cavity 34 above the ejector pin 33.

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

That is, as apparent from the time chart of FIG. 3, according to the method of the present invention, the cavity mold 20 and the core mold 30 are clamped, the mold opening operation and the valve gate pin 42 are performed.
It is sufficient to control the timing of the advancing / retreating operation into / from the cavity C.

First, at the time of injection molding shown in FIG.
The cavity mold 20 is clamped to the core mold 30, and the cavity C is passed through the sprue 21 and the inlet gate 22.
Molten resin P is injected and filled in the inside, and a predetermined secondary pressure is applied for a predetermined time.

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

If the tip of the valve gate pin 42 is tapered and the amount of heat integration is increased, the skin layer formation by resin cooling can be reduced as much as possible.

Then, after the molten resin P is injected and filled into the cavity C and a secondary pressure is applied, the slider 41 is retracted by the operation of the cylinder 40 and the valve gate pin 42 is moved to the cavity C as shown in FIG. Excess resin P2 drawn out from the inside of the cavity C and excluding the cooled and solidified resin P1 (corresponding to the frame 13) is discharged into the 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 housing in 4.

At this time, since the ejector pin 33 has a variable vertical stroke, the volume of the discharged resin accommodating cavity 34 can be freely adjusted, and as a result, the diameter of the gas channel portion 12, that is, the wall thickness of the frame 13 can be controlled. Can be done easily.

Further, if the control is performed so that the excess resin P2 is filled in the discharge resin accommodating cavity 34 just before the gas flows into the outlet gate 23, the hole of the gas passage is not opened in the outlet gate 23, and the minimum gate is formed. It will only leave a mark.

It is also possible to prevent the skin layer from forming on the tip of the pin 42 by heating the valve gate pin 42 itself or using a self-heating element.

Then, 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 discharged resin accommodating cavity 34 are formed in the door pocket 10. However, if gate cutting is performed, Only very small gate marks are left on the molded product, and no bearing is added to the appearance.

As described above, according to the method of the present invention, the valve gate pin 42 is movably inserted into the outlet gate 23 for discharging the surplus resin P2, and the surplus resin P2 is guided into the discharge resin accommodating cavity 34. Since the configuration is such that the minimum passages are formed, the cooling time, secondary pressure, etc. can be freely controlled, uneven gloss on the surface, inflow of gas into the general part, etc. can be prevented, and the wall thickness of the frame 13 can be controlled. Is also easy,
It has the advantages of excellent molding accuracy, no holes at the gate, and only minimal traces of the gate, which minimizes appearance defects.

Next, FIGS. 7 to 9 show another embodiment of the molding die used in the present invention.
Insert the valve gate pin 42 into the outlet gate 23
The basic structure of forming a minimum passage in the same manner as in the above-described embodiment, but in the one shown in FIGS. 7 and 8, the exit gate 23 is not a parting line surface described above but a sub-marine gate 23a having a core type. This is a configuration in which 30 is punched.

In this embodiment, as shown in FIG. 8, when the molded product is demolded, the submarine gate 23a can be demolded by the elasticity of the resin. Thus, the submarine gate 23a is adopted. As a result, the trace of the gate can be set in an inconspicuous place, and the appearance and design can be improved.

Further, as shown in FIG. 9, it is possible to provide an outlet gate 23b on the outer circumference of the ejector pin 33 and to install the valve gate pin 42 in the outlet gate 23b so as to be vertically movable. Also, there is an advantage that the mark of the gate is not conspicuous to the outside and the appearance of the product is improved.

Although the embodiment described above is intended for the door pocket 10 having the gas channel portion 12, interior parts for automobiles such as a door trim having a gas channel portion or the like for strengthening rigidity formed in a part of the peripheral edge, Alternatively, it can be effectively applied to injection-molded products used for light electric components, consumer appliances, etc., and has a wide range of application, so that the practical value of the present invention is extremely high.

[0050]

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

(1) In the present invention, in order to discharge the excess resin for forming the gas channel portion to the outside of the cavity,
Secondary gate pressure and cooling during injection molding because the valve gate pin is inserted in the exit gate between the cavity and the discharge resin accommodating cavity so that it can move forward and backward, and the minimum required gas passage is opened in the exit gate. The time and the like can be freely controlled, and it is possible to prevent uneven luster on the surface and to prevent gas from flowing into the general part, thereby significantly improving the molding accuracy.

(2) According to the present invention, the discharge resin amount can be freely controlled by installing the discharge resin storage cavity for storing the surplus resin above the ejector pin which can be moved up and down. Has the effect of being able to perform freely.

(3) According to the present invention, the valve gate pin is inserted into the outlet gate, and the valve gate pin is retracted so that the excess resin forming the gas channel portion is accommodated in the discharged resin accommodating cavity through the outlet gate. Therefore, if the excess resin is filled in the discharge resin storage cavity just before the gas flows into the outlet gate, the hole of the outlet gate gas path will not be opened and the minimum gate trace will be formed. Only by doing so, the appearance of the gate cut trace is improved as compared with the conventional one.

[Brief description of 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 molding die according to the present invention.

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

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

FIG. 5 is a sectional view showing a state during 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 cross-sectional view showing another embodiment of a molding die used in the method of the present invention.

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

FIG. 9 is a sectional view showing still another embodiment of the 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 molding die adopting a conventional gas injection method.

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

FIG. 13 is a sectional view showing a filled state of 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 cross-sectional view showing an ejector state of a molded product in a conventional injection molding method.

[Explanation of symbols]

 10 Door Pocket 12 Gas Channel 13 Frame 20 Cavity Type 22 Inlet Gate 23 Outlet Gate 30 Core Type 31 Gas Nozzle 32, 33 Ejector Pin 34 Ejection Resin Storage Cavity 40 Cylinder 42 Valve Gate Pin C Cavity P Molten Resin P1 Cooling and Solidifying Resin P2 Surplus resin

Claims (3)

[Claims] 1. A cavity mold (20) and a core mold (30)
Molten resin (P) in the cavity (C) composed of
Gas is injected and filled into the cavity (C) through the gas nozzle (31), and the excess resin (P2) in the cavity (C) is discharged to the outside through the outlet gate (23). In the injection molding method of a resin molded product having (12) formed, a valve gate pin (42) that moves forward and backward is installed in the outlet gate (23), and is introduced into the cavity (C) through the inlet gate (22). When the molten resin (P) is filled, the valve gate pin (42) is inserted into the cavity (C), the outlet gate (23) is closed, and after filling the molten resin (P), the cavity (C) 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 excess tree is passed through the outlet gate (23). An injection molding method for a resin molded product, characterized in that the oil (P2) is housed in a discharge resin housing cavity (34) installed above the 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), gas is injected into the cavity through the gas nozzle (31) to form the gas channel portion (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 outlet gate (23) for discharging the surplus resin (P2) to the outside is set, and a valve gate pin (4) that moves back and forth in the outlet gate (23) by the cylinder (40).
2) is installed in the exit gate (23), and the discharge resin housing cavity (34) communicating with the exit gate (23) is vertically movable.
An injection mold for a resin molded product characterized by being set upward. 3. The injection mold for a resin molded product according to claim 2, wherein a tip portion of the valve gate pin (42) is tapered.