JP2006231718A - Injection mold and injection molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of injecting a fluid in the gap between the back of a molded product and the back side cavity surface of an injection mold in quick timing. <P>SOLUTION: The injection mold is used for injecting a molten resin in a cavity to mold a molded product, and comprises a surface side cavity surface for molding the surface on the surface side of the molded product, a back side cavity surface 28 for molding the surface on the back side of the molded product, and the flow channel opened to the back side cavity surface 28. The opening 32 of the flow channel or the recessed parts 50 and 52 extending from the vicinity thereof are formed to the back side cavity surface 28. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for injection molding a resin molded product.

An injection molding technique for molding a molded product by injecting molten resin into a cavity of an injection mold is known. In the injection molding technique, after the resin injected into the cavity is cooled and solidified, the molded product is taken out from the injection mold.
The resin injected into the cavity of the injection mold shrinks when cooled and solidified. When the resin shrinks, the molded product is peeled off from the cavity surface. If the molded product peels from the cavity surface, the molded product cannot be finished in the intended shape.
Many of the molded products have a surface (surface or design surface) that needs to be finished in an intended shape and a back surface that is allowed to have a poor finish. Hereinafter, the cavity surface for molding the front surface or the design surface is referred to as “front side cavity surface”, and the cavity surface for molding the back surface is referred to as “back side cavity surface”.
Patent Document 1 discloses a technique in which a molten resin is injected into a cavity of an injection mold and then a fluid is injected from a flow path that opens to the back cavity surface toward the back of the molded product. When the fluid is injected from the flow path opened to the back side cavity surface, the fluid enters between the back surface of the molded product and the back side cavity surface, so that the back surface of the molded product is separated from the back side cavity surface. When the back surface of the molded product is peeled off from the back side cavity surface, the design surface of the molded product is kept in close contact with the front side cavity surface. When the design surface of the molded product is kept in close contact with the front cavity surface, the design surface of the molded product is finished in the intended shape.

JP 10-58493 A

The timing for injecting the fluid and peeling the back of the molded product from the back cavity surface is preferably as early as possible. When the back surface of the molded product and the back side cavity surface are peeled off at an early timing, it is easy to obtain a relationship in which the back surface of the molded product is peeled from the back side cavity surface before the design surface of the molded product is peeled from the front side cavity surface. For this reason, the design surface of the molded product is solidified and molded in close contact with the front cavity surface. Therefore, the design surface of the molded product is finished to the intended shape.
When injecting fluid from the channel that opens to the back side cavity surface and peeling the back of the molded product from the back side cavity surface, it is actually difficult to inject fluid at an early timing between the back of the molded product and the back side cavity surface. . If the resin shrinkage does not proceed, the fluid fed from the flow path cannot enter between the back surface of the molded product and the back side cavity surface. As the resin shrinks, the fluid fed from the flow path can enter between the back surface of the molded product and the back side cavity surface. At that time, the design surface may be separated from the front side cavity surface.
The present invention provides a technique capable of injecting a fluid at an early timing between a back surface of a molded product and a back surface cavity surface.

In the present invention, when a concave portion is formed on the back side cavity surface, a phenomenon that fluid can be injected between the back surface of the molded product and the back side cavity surface at an early timing is used. The resin injected into the cavity does not fill every corner of the recess, leaving a space that cannot be filled. In the present invention, fluid is injected between the back surface of the molded product and the back side cavity surface using this space. The fluid enters between the back surface of the molded product and the back side cavity surface at an early timing.
The injection mold of the present invention is used for molding a molded product by injecting molten resin into a cavity. The injection mold includes a front-side cavity surface that molds the front-side surface of the molded product, a back-side cavity surface that molds the back-side surface of the molded product, and a flow path that opens to the back-side cavity surface. A recess extending from the opening of the flow path or the vicinity thereof is formed in the back side cavity surface.
Molten resin has a high viscosity. When the molten resin is injected into the cavity, the molten resin is not filled into every corner of the recess formed in the back side cavity surface, leaving a space that cannot be filled. In this state, when a pressurized fluid is supplied to the flow path, the fluid is injected between the back surface of the molded product and the back side cavity surface. Fluid is injected between the back surface of the molded product and the back side cavity surface at an early timing prior to resin shrinkage. For this reason, the back of the molded product and the back cavity surface are peeled off at an early timing. Therefore, it is possible to remarkably suppress the occurrence of an event in which the design surface of the molded product peels from the front cavity surface.

In the case of the injection mold described above, it is preferable that the recesses extend radially from the opening of the channel on the back side cavity surface or the vicinity thereof.
Since the recesses extend radially, the fluid can be injected over a wide range between the back surface of the molded article and the back cavity surface. Therefore, the molded product back surface and the back side cavity surface can be peeled at an early timing over a wide range.

It is preferable that the recess has such a fineness that the molten resin injected into the cavity cannot enter.
In this case, prior to the shrinkage of the resin, a space for the fluid to enter is secured between the back surface of the molded product and the back side cavity surface. Fluid can be injected at an early timing between the back surface of the molded product and the back surface of the cavity.
But even if it is a recessed part large to the extent that molten resin can penetrate | invade, the effect which accelerates | stimulates permeation of fluid is recognized. If a concave portion that is continuous with the opening on the back side cavity surface of the flow path is formed, fluid can be injected at an early timing between the back surface of the molded product and the back side cavity surface. However, in order to increase the effect, it is preferable that the recess has a fineness that does not allow the molten resin to enter.

The injection molding method of the present invention includes a first step and a second step. In the first step, molten resin is injected into a cavity of an injection mold having a front cavity surface for molding the surface of the molded product and a back cavity surface for molding the back surface of the molded product. In the second step, the fluid is injected from the flow path opening in the back cavity surface into the recess extending from the opening of the flow path or in the vicinity thereof on the back cavity surface.
According to this injection molding method, when a fluid is supplied to the flow path, the fluid is injected between the back surface of the molded product and the back side cavity surface at an early timing prior to the shrinkage of the resin.

  According to the technology of the present invention, fluid can be injected at an early timing between the back surface of the molded product and the back side cavity surface of the injection mold.

The preferred embodiment of this invention is illustrated.
(Form 1)
A front cavity surface for molding the front side surface of the molded product, a back side cavity surface for molding the back side surface of the molded product, a flow path opening in the back side cavity surface, and the back side cavity surface, the flow path An injection mold having a recess extending from or near the opening;
Fluid supply means for supplying pressurized fluid to the flow path;
Control means for controlling the fluid supply means;
An injection molding apparatus comprising:

An embodiment according to the injection molding technique of the present invention will be described with reference to the drawings.
In the present embodiment, a resin molded product 12 shown in FIG. 1 is injection-molded using an injection molding apparatus 20 described later. The molded product 12 is, for example, an automobile bumper. The molded product 12 has a design surface (front surface) 14 and a back surface 16. The design surface 14 is a surface that needs to be finished in an intended shape. The back surface 16 is a surface where shape is not important.
As shown in FIG. 2, the injection molding apparatus 20 includes a molding die 22 and a pressure unit 21. The molding die 22 has a first die 24 and a second die 25. FIG. 2 shows a state in which the molding die 22 is closed by combining the first die 24 and the second die 25. When the mold 22 is closed, the cavity 26 is formed by the first cavity surface 27 of the first mold 24 and the second cavity surface 28 of the second mold 25. When the mold 22 is opened, the first mold 24 and the second mold 25 are separated. The shape of the cavity 26 corresponds to that of the molded article 12. The first cavity surface 27 of the first mold 24 molds the design surface 14 of the molded product 12. The second cavity surface 28 of the second mold 25 forms the back surface 16 and the end surface of the molded product 12.
The first mold 24 is provided with a gate 30 that communicates the outside of the mold 22 with the first cavity surface 27. Molten resin is injected into the gate 30 from an injection nozzle (not shown) arranged outside the mold 22.
A flow path 31 and a flow path 33 are formed in the second mold 25. One end of the channel 31 opens to the second cavity surface 28 at the opening 32, and the other end opens to the outside of the second mold 25. Similarly to the flow path 31, one end of the flow path 33 opens to the second cavity surface 28 at the opening 34, and the other end opens to the outside of the second mold 25.

A vent member 36 is inserted into the opening 32 of the flow path 31. A vent member 38 is also inserted into the opening 34 of the flow path 33. The flow path 31 and the vent member 36 and the flow path 33 and the vent member 38 have the same configuration. Therefore, in the following, they will be described by using the flow path 31 and the vent member 36 as a representative.
The vent member 36 is fixed to the second mold 25 with a bolt (not shown) while being inserted into the opening 32 of the flow path 31. With the vent member 35 fixed to the second mold 25, a gap 58 (see FIG. 3) is secured between the outer wall of the vent member 36 and the inner wall of the opening 32 (the gap 58 is (Because the width is narrow, it is shown as a line in FIG. 3).
As shown in FIG. 3, the second cavity surface 28 of the second mold 25 is formed with a plurality of recesses 50 and 52 extending from the opening 32 in the direction opposite to the opening. Ten recesses 50 are formed and arranged radially. Four recesses 52 are formed, and two recesses 52 are arranged in parallel. As shown in FIG. 4, the recess 50 has a triangular cross section. Similar to the recess 50, the recess 52 has a triangular cross section. The recesses 50 and 52 have a fine width.

As shown in FIG. 2, the pressurizing unit 21 includes a fluid pipe 40, a filter 43, a regulator 44, a solenoid valve 45, a timer unit 46, and a controller 48.
One end 42 of the fluid pipe 40 is supplied with high-pressure factory air. The other end side of the fluid piping 40 is bifurcated. The fluid pipe 40 is bifurcated and then connected to the flow path 31 and the flow path 33 of the second mold 25.
The filter 43, the regulator 44, and the solenoid 45 are interposed in the fluid piping 40. The filter 43 removes foreign matters from the factory air. The regulator 44 adjusts (depressurizes) the pressure of the factory air to a predetermined value (for example, 0.5 MPa). The solenoid valve 45 is an on-off valve. When the solenoid valve 45 is open, pressurized air (factory air) regulated by the regulator 44 is supplied to the flow path 31 and the flow path 33 of the second mold 25.
The timer unit 46 is connected to the solenoid valve 45. The controller 48 is connected to the timer unit 46. The controller 48 controls the timer unit 46, the opening / closing of the mold 22, the operation of the injection nozzle, and the like in an integrated manner. The controller 48 outputs a mold closing signal to the timer unit 46 at the timing when the mold 22 starts to close. The controller 48 outputs an injection signal to the timer unit 46 at the timing when the injection nozzle injects the molten resin. The timer unit 46 executes predetermined processing based on the input mold closing signal and injection signal. This process will be described later.

Each process which shape | molds the molded article 12 using the injection molding apparatus 20 is demonstrated. As shown in FIG. 5, when the molded product 12 is molded, a process of closing the mold 22 is first executed. As described above, the controller 48 outputs a mold closing signal to the timer unit 46 at the timing when the mold 22 starts to close (timing when the mold closing process is started). Then, the timer unit 46 executes processing for outputting a valve closing signal to the solenoid valve 45. The solenoid valve 45 is closed when a valve closing signal is input. Accordingly, the pressurized air is not supplied to the flow paths 31 and 33 of the mold 22.
Following the mold closing process, an injection process is performed. When the injection process is executed, the molten resin injected from the injection nozzle passes through the gate 30 and fills the cavity 26 while flowing. When the injection signal is input from the controller 48, the timer unit 46 starts measuring time. The timer unit 46 outputs a valve opening signal to the solenoid valve 45 at a timing when the flowing resin covers the region where the concave portions 50 and 52 of the second cavity surface 28 are formed based on the time measured. It is set in advance how much time has elapsed since the time when the timer unit 46 started measuring the time when the resin covers the region where the concave portions 50 and 52 of the second cavity surface 28 are formed. . In the setting, pressure measurement data in a region where the concave portions 50 and 52 of the second cavity surface 28 are formed, a flow analysis result of resin in the cavity 26, and the like are used. As described above, the widths of the recesses 50 and 52 are fine. In addition, since the molten resin has a high viscosity, it does not penetrate into fine portions. For this reason, as shown in FIG. 6, a passage path 56 is formed by the resin 72 and the recesses 50 and 52.

When the solenoid valve 45 is opened, a fluid supply process in which pressurized air is supplied to the flow path 31 is performed. As shown in FIG. 5, the fluid supply process starts from the middle of the injection process (that is, the timing at which the resin covers the region where the recesses 50 and 52 of the second cavity surface 28 are formed).
The pressurized air supplied to the flow path 31 enters between the back surface of the resin 72 and the second cavity surface 28 while passing through the passage path 56 via the gap 58 of the opening 32. Then, the back surface of the resin 72 and the second cavity surface 28 are peeled off. FIG. 7 shows a state in which the back surface 73 of the resin 72 (when the resin 72 is solidified and formed as the molded product 12, becomes the back surface 16 of the molded product 12) is peeled from the second cavity surface 28.
As shown in FIG. 5, after the injection process is completed, the process proceeds to the pressure holding process. In the pressure holding process, a substantially constant pressure is continuously applied from the gate 30 to the cavity 26. Moreover, a cooling process is also started with the start of a pressure-holding process. In the cooling step, the resin 72 is cooled and solidified by the cooling water passing through the cooling pipe (not shown in FIG. 2) passing through the first mold 24 and the second mold 25. Even if the pressure holding process is completed, the fluid supply process and the cooling process are continued. The fluid supply process and the cooling process are completed simultaneously. The timer unit 46 outputs a valve closing signal to the solenoid valve 45 at the timing when the fluid supply process and the cooling process are completed. When the valve closing signal is input and the solenoid valve 45 is closed, the air supply to the cavity 26 is stopped.
Next, the mold 22 is opened by moving to a mold opening process. Finally, a product take-out step is executed to take out the molded product 12 from the mold 22.

As described above, the pressurized air enters between the back surface 73 of the resin 72 and the second cavity surface 28 while passing through the passage path 56, whereby the back surface 73 of the resin 72 and the second cavity surface 28 are separated. For this reason, the back surface 73 of the resin 72 and the second cavity surface 28 are separated at an early timing. When the back surface 73 of the resin 72 and the second cavity surface 28 are separated at an early timing, it is possible to suppress the surface 74 of the resin 72 from being separated from the first cavity surface 27. Therefore, the design surface 14 of the molded product 12 is finished into a better shape (intended shape).
On the other hand, if the concave portions 50 and 52 are not formed on the second cavity surface 28, the pressurized air gradually enters between the back surface 73 of the resin 72 and the second cavity surface 28 around the opening 32. . Therefore, the timing at which the back surface 73 of the resin 72 and the second cavity surface 28 are peeled is delayed. When the timing is delayed, the surface 74 of the resin 72 may peel from the first cavity surface 27. When the surface 74 of the resin 72 is peeled from the first cavity surface 27, the design surface 14 of the molded product 12 is not finished in the intended shape.
When the concave portions 50 and 52 are formed in the second cavity surface 28, the back surface 73 of the resin 72 and the second cavity surface 28 can be separated in a wider range. When the back surface 73 of the resin 72 and the second cavity surface 28 can be separated in a wider range, a wider range of the design surface of the molded product is finished in a better shape. Therefore, the number of flow paths opening in the second cavity surface 28 can be reduced.

The recesses 50 and 52 may be large enough to allow the resin 72 to enter and not be filled with the resin. If the recesses 50 and 52 cannot be filled with the resin, the pressurized air passes through the recesses 50 and 52 and enters between the back surface 73 of the resin 72 and the second cavity surface 28 at an early timing.
The recesses 50 and 52 extending to the second cavity surface 28 may not extend from the opening 32. Even if the recesses 50 and 52 extend from the vicinity of the opening 32, the pressurized air flowing out from the opening 32 passes between the back surface 73 of the resin 72 and the second cavity surface 28, and the recesses 50 and 52. Enter the starting point.
The recesses 50 and 52 do not have to extend linearly. The recesses 50 and 52 can be bent according to the range in which the back surface 73 of the resin 72 is to be peeled from the second cavity surface 28.
The cross-sectional shape of the recesses 50 and 52 is not limited to a triangular shape. For example, it may have a semicircular shape or a cross-sectional shape having a deeper portion than the opening. If the cross-sectional shape of the recesses 50 and 52 is larger than the opening portion, the compressed air can easily pass, so that the compressed air can be spread over a wider range.
By injecting a gas or liquid other than the pressurized air, the back surface of the resin and the cavity surface can be separated.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
In addition, the technical elements described in the present specification or drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

The perspective view of a molded article. The block diagram of an injection molding apparatus. FIG. 3 is a view taken along the line III-III in FIG. 2 (a plan view of a portion where a concave portion of the back side cavity surface is formed). IV-IV sectional view taken on the line of FIG. Process drawing of injection molding. Sectional drawing of the state with which the cavity was filled with resin. Sectional drawing of the state in which the back surface of resin peeled from the cavity surface.

Explanation of symbols

12: Molded product 14: Design surface 16: Back surface 20: Injection molding device 21: Pressurizing unit 22: Molding mold 24: First mold 25: Second mold 26: Cavity 27: First cavity surface 28: Second cavity surface 30: Gate 31: Channel 32: Opening 33: Channel 36, 38: Vent member 40: Fluid piping 42: One end of fluid piping 43: Filter 44: Regulator 45: Solenoid valve 46: Timer unit 48: Controller 50, 52: Recess 56: Passage path 58: Gap 72: Resin 73: Resin back surface

Claims (4)

An injection mold that molds a molded product by injecting molten resin into the cavity.
A front cavity surface for molding the front side surface of the molded product;
A back side cavity surface for molding the back side surface of the molded product;
It has a channel that opens to the back cavity surface,
An injection mold, wherein a recess extending from the opening of the flow path or the vicinity thereof is formed on the back side cavity surface.   2. The injection mold according to claim 1, wherein the recess extends radially from the opening of the flow path or the vicinity thereof.   The injection mold according to claim 1 or 2, wherein the concave portion has a fineness that prevents the molten resin injected into the cavity from entering. A first step of injecting a molten resin into a cavity of an injection mold having a front cavity surface for molding the surface of the molded product and a back cavity surface for molding the back surface of the molded product;
A second step of injecting fluid from the flow path opening in the back cavity surface into the recess extending from the opening of the flow path or in the vicinity thereof on the back cavity surface;
An injection molding method characterized by comprising:

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