JP2002079549A - Molding method and valve gate mold device used for molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a part where an excessively high temperature is localized from occurring by making the internal resin temperature of a material passage in a valve device uniform and thereby, prevent the properties of a resin from being deteriorated. SOLUTION: An air blowing passage 63 and an exhaust passage 64 are formed on a backing plate 17 on the fixed mold half side and the air blowing passage 63 is arranged opposite to the center, in the axial direction, of a valve body 36 of the valve device 31. Air is sent into the air blowing passage 63 by an air blower 62. The center, in the axial direction, of the valve body 36 is forcibly cooled by blowing the air to the center, in the axial direction, of the valve body 36 from the air blowing passage 63. The valve body 36 with a heater 51 mounted on the outer periphery tends to originally show a higher temperature in the center, in the axial direction, where heat is transmitted from both ends, than the both ends. However, the entire material passage 38 of the valve body 36 shows a uniform temperature due to the described cooling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method and a valve gate type mold apparatus used therefor, and is used for injection molding of a thermoplastic resin.

[0002]

For example, Japanese Patent Application Laid-Open No. 9-19 / 1991
As described in JP-A-946, for example, in a hot runner mold apparatus which heats a resin as a molding material in a material passage to a gate to a product cavity and keeps a molten state at all times, the gate is mechanically moved by a valve pin. 2. Description of the Related Art A valve gate type mold device that opens and closes in a known manner is known. The hot runner mold device aims at increasing the molding efficiency, and the reason why the gate is closed is to prevent the resin from leaking from the gate when the mold is opened.

FIG. 5 (a) shows an example of a valve device 1 in this type of valve gate type mold device. In the figure, reference numeral 2 denotes a cylindrical valve body.
Is connected to a manifold (not shown) located on the left side of the figure. The inside of the valve main body 2 is a material passage 3 communicating with a gate (not shown) located on the right side in the figure. A valve pin (not shown) that penetrates the material passage 3 and moves in the left-right direction in the figure to open and close the gate is provided. A material passage 3 is provided on the outer peripheral surface of the valve body 2.
A heater 4 for heating the resin inside is provided, and a cylindrical heater cover 5 that covers the heater 4 from the outer peripheral side is fixed. The heater 4 is composed of a linear heater and is wound around the outer peripheral surface of the valve body 1. The heater 4 is densely wound at both ends of the valve body 2, but is coarsely wound at an intermediate portion. The reason will be described later.

FIG. 5B shows the valve device 1.
The result of measuring the temperature in the vicinity is shown. In the graph of FIG. 5, the horizontal axis represents the distance from the gate-side tip of the valve body 2, and the vertical axis represents the temperature. The temperature was measured at points a1, a2, a3, a4, a5, a6, and a7 in the material passage 3 and at points b1, b2, b3, b4, and b5 on the outer peripheral surface of the valve body 2. . Then, the temperature is actually set in the molding die of the storage case of the audio cassette tape, and the measurement is performed. The control set temperature is set to 250 ° C. by the manifold, and the valve device 1 is set to 250 ° C. Was set to 26 ° C.
That is, the grounding surface of the valve body 2 with the manifold
The temperature of 2a is 250 ° C. Graph A shown by a thick solid line is
This is the temperature distribution on the outer peripheral surface of the valve body 2 during molding, that is, on the heater 4 side. A broken line graph B shows a temperature distribution in the material passage 3 in a state where the resin is contained in the material passage 3. This is the temperature of the resin. On the other hand, a two-dot chain line graph C shows the temperature distribution in the material passage 3 when there is no resin in the material passage 3. Furthermore, a thin solid line graph D
Is a temperature distribution of the valve device 1 alone when the temperature is set to 100 ° C.

As is apparent from graphs A, B and C, the temperature tends to be low at both ends of the valve device 1 and high at the center. This is considered to be because heat is transmitted from both ends in the central portion. In the illustrated valve device 1, in order to eliminate such non-uniformity in temperature, the heater 4 is wound tightly at both end sides of the valve body 2 and coarsely wound at the intermediate portion. As shown by the above, the temperature distribution has a large non-uniformity.

[0006] At the lowest temperature portion of the material passage 3, that is, at both ends, it is necessary to obtain a temperature sufficient to secure the fluidity of the resin. Therefore, the temperature at the central portion becomes excessively high. If the temperature is too high, the resin in the material passage 3 burns (causing black charring), and the characteristics of the resin deteriorate.

The present invention has been made to solve the above problems, and provides a molding method capable of making the temperature of a molding material in a material passage of a valve device uniform, and a valve gate type mold device used therefor. The purpose is to:

[0008]

According to a first aspect of the present invention, in order to achieve the above object, a plurality of molds that are opened and closed with each other are closed, and a product cavity is formed between these molds. A molding material is filled into the product cavity through a gate from a material passage formed in the product cavity, and the gate is closed by a valve device except when the molding material is filled in the product cavity. In a molding method for heating a valve body having a material passage therein communicating with a gate by a heater provided on an outer peripheral side of the valve body, an axially central portion of the valve body is forcibly cooled.

In a valve body provided with a heater on the outer peripheral side, heat is transmitted from both ends to a central portion in the axial direction, so that the temperature tends to be higher at the central portion in the axial direction than at both ends. On the other hand, by forcibly cooling the central portion in the axial direction of the valve body, the temperature can be made uniform throughout the material passage in the valve body.

According to a second aspect of the present invention, there is provided a valve gate type mold apparatus used in the molding method according to the first aspect, wherein a plurality of molds are opened and closed with each other to form a product cavity therebetween when the mold is closed, and these molds are provided. And a valve device provided on a mold having a gate opening to a product cavity, the valve device comprising a valve body having a material passage therein communicating with the gate, and a valve body provided on an outer peripheral side of the valve body. And a cooling device for cooling a central portion of the valve body in the axial direction.

By providing the cooling device as described above,
By forcibly cooling the axial center portion of the valve body, it becomes possible to adjust the temperature of the molding material in the material passage of the valve body.

According to a third aspect of the present invention, in the valve gate type mold apparatus according to the second aspect of the present invention, the cooling device sends air to a central portion of the valve body in the axial direction.

By blowing air to the axial center of the valve body in this way, the axial center of the valve body is forcibly cooled.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a molding method of the present invention and a valve gate type mold apparatus used for the molding method will be described.
This will be described with reference to the drawings. First, the first embodiment is shown in FIG.
A description will be given based on FIG. In FIG. 1, reference numeral 11 denotes a fixed mold, 12 denotes a movable mold, and the fixed mold 11 and the movable mold 12, which are molds, are shown in the vertical direction in FIG.
The molds are moved to each other to open and close, and a product cavity 13 having a product shape is formed therebetween when the mold is closed. Fixed type 11
A fixed-side mold plate 16, a fixed-side receiving plate 17 fixed to the back surface of the fixed-side mold plate 16, that is, a surface opposite to the movable mold 12, and fixed to the back side of the fixed-side receiving plate 17 via a spacer block. A fixed-side mounting plate (not shown) is provided, and a manifold 18 is provided between the fixed-side mounting plate and the fixed-side receiving plate 17. The manifold 18 has a runner 19 as a material passage formed therein, and a thermoplastic resin as a molding material in the runner 19 is always in a molten state by heating a heater (not shown) provided in the manifold 18. Is to be kept.

A gate bush 22 is inserted into a gate bush mounting hole 21 formed through the fixed mold plate 16.
Are detachably fitted. A gate 23 that opens to the product cavity 13 is formed at an end of the gate bush 22. And the gate bushing hole
A cooling water passage 24 is provided between the inner surface of 21 and the gate bush 22.
Is formed, and an O-ring 25 for preventing water leakage is mounted on the cooling water passage 24.

A valve device 31 for opening and closing the gate 23 is incorporated in the fixed mold 11. Next, the configuration of the valve device 31 will be described. The fixed side receiving plate 17 is formed with a mounting hole 32 penetrating in the mold opening and closing direction, and the inside of the gate bush 22 is a mounting hole 33 communicating with the mounting hole 32. A substantially cylindrical valve body 36 whose axial direction is the mold opening / closing direction is incorporated in the installation holes 32 and 33. One end of the valve body 36 is a flange portion 37 and is fixed to the manifold 18 and the fixed-side receiving plate 17.

The inside of the valve body 36 is a material passage 38 for connecting the runner 19 in the manifold 18 to the gate 23. Although the material passage 38 has a substantially columnar shape, three support blades 39 extending in the mold opening and closing direction are integrally formed on the inner peripheral surface of the tip portion on the gate 23 side. As shown in FIG. 2, these support blades 39
They are radially spaced 120 ° apart from the central axis of 38. The inner edge of the support blade 39 has a tapered portion on the side opposite to the gate 23, but the other portions are parallel to the mold opening / closing direction. The concave groove portion between the support blades 39 is a divided material passage portion 41. Since these divided material passages 41 have three support blades 39, they form three divided passages. In addition, the valve body 36
The inner material passage 38 has a columnar portion 42 at a portion closer to the gate 23 than the support blade 39. The inner peripheral surface of the cylindrical portion 42 is located on the same cylindrical surface as the inner edge of the support blade 39.

The valve body 36 has a built-in valve pin 46 as a valve body that moves in the mold opening and closing direction by driving a hydraulic cylinder (not shown) provided on a fixed-side mounting plate. This valve pin 46
A gate closing portion 47 formed at the end on the side of the gate 23 is adapted to be inserted into and removed from the gate 23 to close the gate 23. The axial direction of the valve pin 46 is the mold opening / closing direction, and the outer peripheral surface is constantly slidably in contact with the inner edge of the support blade 39 of the valve body 36. Thereby, the tip of the valve pin 46 on the gate 23 side is supported,
When the valve pin 46 closes the gate 23, the valve pin 46 fits into the cylindrical portion 42. On the other hand, when the gate 23 is open, the tip of the valve pin 46 is located at the middle of the support blade 39. Further, the valve pin 46 is supported by a guide bush 48 fixed in the valve body 36 at an end of the valve body 36 on the manifold 18 side. That is,
A valve pin 46 slidably passes through the guide bush 48.

A band heater 51 for heating the material passage 38 and a substantially cylindrical heater cover 52 for covering the heater 51 from the outer peripheral side are fitted on the outer peripheral surface of the valve body 46. The heater 51 is connected to the valve body 36
At the tip of the gate 23 side of the
And has a blade opposing portion 53. The heater 51 is formed by winding a linear heater. As shown in FIG. 5 described above, the winding is made dense at both ends in the axial direction of the valve body 36, while the central portion in the axial direction is formed. Then, it is preferable to make the winding coarse.

A step 56 is formed on the outer periphery of the distal end of the valve body 36 on the gate 23 side, and a short cylindrical heat insulating ring 57 is fitted and fixed to the step 56. The outer peripheral surface of the heat insulating ring 57 is
Cylindrical mating surface of the same diameter formed in the built-in hole 33 of
Fits 58. As a result, the valve body 36 is supported by the gate bush 22 of the fixed mold 11 at the tip end on the gate 23 side. Insulation ring 57 and gate bush
A gap 59 is formed between the inner surfaces of the built-in holes 32 and 33 and the outer surface of the valve body 36 or the heater cover 52 for heat insulation other than the fitting surface 58 with the 22. Also,
The insulation ring 57 is connected to the portion of the gap 59 on the gate 23 side and the heater
The part on the 51 side is blocked.

In addition, the mold apparatus includes the valve body 36.
Is provided with a cooling device 61 for cooling a central portion in the axial direction. The cooling device 61 has a blower 62, and blows air as a cooling medium supplied from the blower 62 to a central portion in the axial direction of the valve body 36 (heater cover 52) to cool the same. One or more air passages 63 are provided. The air passage 63 is, for example,
And opens toward the axial center of the outer peripheral surface of the heater cover 52. Also, the fixed side receiving plate 17
Is located closer to the manifold 18 than the ventilation passage 63
One or more exhaust passages 64 are formed. The exhaust passage 64 opens at a position near the flange 37 of the valve body 36.

Reference numeral 65 denotes a movable mold plate of the movable mold 2.

Next, a molding method using the valve gate type mold apparatus will be described. First fixed type 11 and movable type
After closing the mold 12 and forming the product cavity 13 between the fixed mold 11 and the movable mold 12, the valve pin 46 is moved to the movable mold 12.
The gate 23 is opened by moving in a direction away from the gate. Note that even when the gate 23 is open, the valve pin 46
It remains fitted to the support blade 39 of the valve body 36. Then, a molten thermoplastic resin as a thermoplastic molding material is injected into the fixed mold 11 from the injection molding machine. This resin passes through the runner 19 of the manifold 18 and the like, and further passes through the material passage 38 in the valve body 36, the divided material passage portion 41 between the supporting blades 39 in which the valve pins 46 are fitted, and the columnar portion 42. From 23 flows into the product cavity 13. After the resin is filled into the product cavity 13 in this manner, the valve pin 46 moves toward the movable mold 12 through the holding pressure, fits into the gate 23, and closes the gate 23. Product cavity
The resin in 13 is actively cooled by cooling water passing through cooling water passage 24. After the resin in the product cavity 13, that is, the product is cooled and solidified, the fixed mold 11 and the movable mold are cooled.
Open the mold and take out the molded product. afterwards,
The mold is closed again, the above steps are repeated, and the molding is repeated. During that time, the resin in the material passage 38 of the valve body 36 is always kept in a molten state by the heating of the heater 51, like the resin in the runner 19 of the manifold 18.

The blower 62 blows air. Blower
The air blown from the 62
It is sprayed through 63 onto the axial center of the valve gate body 36 (heater cover 52). As a result, the valve gate body 36, particularly the axial center portion, is forcibly cooled. Further, the air that has exchanged heat with the valve gate body 36 is discharged to the outside of the mold apparatus through an exhaust passage 64 as shown by an arrow G. Note that the cooling by the blowing is always performed throughout the molding cycle, but may be performed intermittently.

As described above, in the valve body 36 in which the heater 51 is provided on the outer peripheral side, heat is transmitted from both ends to the central portion in the axial direction. Show a tendency to become In contrast, the blower 62
The central part of the valve body 36 in the axial direction is forcibly cooled by air blown from the outside, and the temperature of the resin is reduced within the material passage 38 of the valve body 36 by lowering the temperature.
It can be made almost uniform over the entire length of 38. That is,
Partial temperature adjustment of the material passage 38 can be performed by local air blowing, and thus the temperature distribution of the material passage 38 can be made uniform. Therefore, in order to secure the fluidity of the resin in the material passage 38, it is possible to prevent a portion where the temperature of the resin becomes excessively high in the material passage 38, and to prevent the resin from being burnt. Deterioration of resin characteristics can be prevented.

Further, since the cooling is performed by blowing air, unlike the case where a liquid such as water is used for cooling, there is no problem such as water leakage while cooling is ensured. Also, the configuration of the mold apparatus can be simplified.

Next, a second embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. Parts corresponding to those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
The mold apparatus of the second embodiment uses water as a cooling medium of a cooling device 71 for forcibly cooling the axially intermediate portion of the valve body 36. In the cooling device 71, a water pipe 72 is wound around an outer peripheral surface of a central portion in the axial direction of the heater cover 52, and both ends of the water pipe 71 are connected to an external water supply device 73 through the fixed-side receiving plate 17. Have been.

At the time of molding, the water supplied from the water supply device 73 passes through the water supply pipe 72 as shown by the arrow H and returns to the water supply apparatus 73 again as shown by the arrow I. By surrounding the central portion in the axial direction of 52, the central portion in the axial direction of the heater cover 52 and thus the valve body 36 is forcibly cooled. Thereby, the temperature of the entire material passage 38 of the valve body 36 can be made uniform.

Next, a third embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In the third embodiment, one or a plurality of heat pipes 76 are used as a cooling device for forcibly cooling the axially intermediate portion of the valve body 36. As is well known, the heat pipe 76 is a device that moves the heat at high speed by moving the vapor of the heat medium enclosed in the pipe together with the wick material and transferring the latent heat of evaporation.
The heat pipe 76 is fixed, for example, by being embedded in the fixed-side receiving plate 17, and one end of the heat pipe 76 is brought into contact with the axial center of the outer peripheral surface of the heater cover 52. Fixed side support plate 17
Since the heat pipe itself is cooled, the other end of the heat pipe 76 need only be embedded in the fixed-side receiving plate 17.

Therefore, during molding, heat is applied to the valve body.
The heat is transmitted from the axial central portion of the valve body 36 to the fixed-side receiving plate 17 through the heat pipe 76, whereby the axial central portion of the valve body 36 is forcibly cooled. This allows the valve body 36
Temperature in the entire material passage 38 can be made uniform.

The present invention is not limited to the above-described embodiment, and various modifications can be made. For example,
In the first embodiment, the blower 62 is used to forcibly blow air.However, an opening hole facing the axial center of the valve body from the outside is simply formed in a mold member such as a fixed-side receiving plate. However, a cooling effect can be obtained. Further, the central portion in the axial direction of the valve body may be cooled by contacting a heat conductor made of a simple metal material or the like.

[0032]

According to the first aspect of the present invention, the gate is closed by the valve device except when the molding material is filled in the product cavity, and the valve body in the valve device has a material passage communicating with the gate therein. In the molding method in which the heater is provided on the outer peripheral side of the valve body, the central portion in the axial direction of the valve body is forcibly cooled, so that the temperature of the molding material in the material passage of the valve device can be made uniform, Therefore, it is possible to prevent the temperature of the molding material from becoming excessively high in the material passage, and prevent the characteristics of the molding material from deteriorating.

According to the valve gate type mold apparatus of the second aspect of the present invention, there is provided a valve apparatus, wherein cooling is provided for cooling a central portion in the axial direction of a valve body having a material passage therein and a heater provided on an outer peripheral side. Since the device is provided, the temperature of the molding material in the material passage of the valve device can be made uniform, so that the temperature of the molding material in the material passage of the valve device can be prevented from becoming excessively high, and the characteristics of the molding material can be reduced. It can be prevented from lowering.

According to the third aspect of the present invention, in addition to the effect of the second aspect of the present invention, since the cooling device blows air to the central portion in the axial direction of the valve body, reliable cooling can be performed. Unlike the case where a liquid such as water is used for cooling, there is no problem such as water leakage.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of a valve gate type mold apparatus according to the present invention.

FIG. 2 is a cross-sectional view showing the vicinity of the support blade.

FIG. 3 is a cross-sectional view showing a second embodiment of the valve gate type mold apparatus of the present invention.

FIG. 4 is a longitudinal sectional view showing a third embodiment of the valve gate type mold apparatus of the present invention.

FIGS. 5A and 5B show the results of temperature measurement on an example of a conventional valve gate type mold apparatus, in which FIG. 5A is a longitudinal sectional view of the valve apparatus, and FIG. 5B is a graph showing temperature.

[Explanation of symbols]

 11 Fixed mold (mold) 12 Movable mold (mold) 13 Product cavity 19 Runner (material passage) 23 Gate 31 Valve device 36 Valve body 38 Material passage 51 Heater 61 Cooling device 71 Cooling device 76 Heat pipe (Cooling device)

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kunio Yamamoto 3-1-1 Koganecho, Niigata City, Niigata F-term in Niigata Works, Mitsubishi Materials Corporation 4F202 CA11 CB01 CK02 CK07 CN05 CN22

Claims (3)

[Claims] A mold is closed between a plurality of molds which are opened and closed with each other, a product cavity is formed between the molds, and a molding material is injected into the product cavity via a gate from a material passage formed in the mold. The gate is closed by a valve device except when filling and filling the molding material into the product cavity, and a valve body having a material passage communicating with the gate in the valve device is provided on an outer peripheral side of the valve body. A molding method for heating by a provided heater, wherein a central portion in the axial direction of the valve body is forcibly cooled. 2. A valve gate type mold apparatus used in the molding method according to claim 1, wherein a plurality of molds are opened and closed with each other and a product cavity is formed between the molds when the molds are closed. A valve device provided on a mold having a gate opening to the cavity, the valve device comprising a valve body having a material passage therein communicating with the gate, and a heater provided on an outer peripheral side of the valve body. And a cooling device for cooling an axially central portion of the valve body. 3. The valve gate type mold apparatus according to claim 2, wherein the cooling device blows air to a central portion in the axial direction of the valve body.