WO2002000415A1

WO2002000415A1 - Metal mold for injection molding machine and method for mold injection molding using the metal mold

Info

Publication number: WO2002000415A1
Application number: PCT/JP2000/004221
Authority: WO
Inventors: Itsuo Shibata; Ryoichi Sekiguchi; Masashi Kobayashi
Original assignee: Ju-Oh Inc.
Priority date: 2000-06-27
Filing date: 2000-06-27
Publication date: 2002-01-03

Abstract

An injection molding method using a metal mold comprising an openable metal mold plate and a cavity formed in the metal mold plate and capable of maintaining an excellent flowability of injected material, providing a formed product excellent in transferability, and promoting a rapid dissipation of heat from molten resin or molten metal injected into the cavity so that a cycle time for injection molding is not extended, wherein a thin sheet mold plate including a cavity surface or a core surface of the cavity is installed independently of the metal mold plate, the cavity surface or the core surface formed on the mold plate is maintained at a specified temperature at the time of injection, the metal mold plate is brought into contact with the mold plate when the injection molding is performed, and the deformation of the mold plate is suppressed by the metal mold plate and the mold plate is cooled.

Description

Technical field Mold for injection molding machine and injection molding method using this mold.

The present invention relates to a mold and an injection molding method for an injection molding machine (including die casting) for obtaining a molded product having a predetermined shape by injecting a molten material into a cavity with a mold closed. Also, the present invention relates to a mold and an injection molding method for an injection molding machine in which a material is injected while a core surface is preheated to improve the fluidity of the material inside the cavity and the transferability to the mold. Background art

In injection molding of resin, metal, and the like, a molten material is injected into a cavity with a fixed mold and a movable mold closed, and heat of the material is transferred to the cavity through the fixed mold and the movable mold. Heat is exchanged by discharging the material to the outside, and the material is solidified to obtain a molded product in the shape of the cavity.

Therefore, the temperature of the mold is set considerably lower than the molten material injected to increase the heat exchange efficiency. As a result, the injected molten material immediately begins to solidify and flows on the cavity surface while being sent by the injection pressure, resulting in poor transferability and warpage due to uneven residual stress. In addition, it may cause the need for large injection pressures, or cause unfilled products that are not perfectly shaped.

As a method for keeping the temperature of the material injected from the molding machine constant without lowering it for a certain period of time, a method of preheating the mold surface is known. For example, Japanese Patent Application Laid-Open No. 8-39571 discloses an invention aimed at improving the transferability of a material (resin) ejected into a cavity by preheating a mold surface by induction heating. Is disclosed.

According to the invention described in this publication, an induction heating coil is disposed in front of a movable mold with a pot, and the surface of the mold is preheated by induction heating of the induction heating coil. At the time of opening and closing, the induction heating coil and the mold are The heating coil is kept away from the mold. Another idea is to incorporate an induction coil inside the mold.

This method is an effective means for improving the transferability of the molded product surface and preventing warpage.

'However, it is difficult to heat only the surface of the movable mold by the conventional preheating method as described above. That is, there is a problem that it is difficult to set only the temperature of the preheated portion to a desired temperature because the heat of the preheated portion radiates heat to another portion of the mold. ,

In addition, since the mold is generally formed to be sufficiently large for the cavity in order to obtain sufficient rigidity during injection molding, it is necessary to set the surface of the mold to the desired temperature. It takes a long time. In addition, there is a problem that it takes a long time for cooling as a result of inputting extra heat energy, thereby prolonging the molding cycle time. In addition, in the injection molding of metals such as magnesium alloys, aluminum alloys, and zinc alloys, the thermal conductivity and melting point are considerably higher than those of resins, so that the injected molten metal touches the mold immediately. However, there is a problem that the above-mentioned inconveniences appear remarkably.

'' In recent years, injection molded products of magnesium have been widely used for thin molded products such as personal computer cases.However, it is important to obtain molded products excellent in fillability and transferability for these thin molded products. Extremely difficult.

The present invention has been made in view of the above problems, and when performing the injection process, the temperature of the cavity surface or the core surface is heated to a certain value or more and uniformly, and the good fluidity of the injected material is obtained. Injection molding machine that retains heat and obtains molded products with excellent transferability, promotes rapid heat dissipation of molten resin and molten metal injected into the cavity, and does not extend the cycle time of injection molding It is an object of the present invention to provide a metal mold and an injection molding method. Disclosure of the invention

When the inventors of the present invention try to improve the transferability by heating the mold surface, the input heat is stored inside the mold, which increases the cycle time of injection molding and improves heat dissipation. In order to solve the contradictory problem that a sufficient surface temperature cannot be obtained and the transferability decreases if the cycle time is shortened, the following method was devised. In other words, the portion where the cavity surface or the core forming the cavity is formed is made independent of the mold plate, and the portion is made into a thin plate shape so that the heat capacity thereof is made as small as possible. Preheating can be quickly performed to a surface temperature that can maintain fluidity. However, if it is made into a thin plate, there is no rigidity that can withstand the injection pressure as it is, so a cooled mold base such as a rigid movable mold plate is pressed against the independent part during the injection process, The rigidity of the portion can be ensured. In addition, it has been found that by making the heat capacity of the mold base larger than that of the above-mentioned independent part, the response of heat exchange can be made faster and heat can be quickly released.

Furthermore, by making the independent portions thermally suspended in a so-called "suspended" state, the temperature distribution of the independent portions can be made substantially uniform, and the predetermined portion necessary for good transfer can be obtained. It has been found that the temperature can be maintained.

In addition, unlike resin molding, metal injection molding rapidly radiates heat after injection and at the same time as filling, so even if the temperature on the mold surface is raised considerably, it does not affect the molding cycle. A sufficient effect can be expected. FIG. 1 is a perspective view for explaining the inventive concept of the present invention more specifically.

As shown in FIG. 1, the mold of the present invention is formed with a first mold plate and a second mold plate that can be opened and closed, and between the first mold plate and the second mold plate. In a mold of an injection molding machine having a cavity, a third mold plate (3) is interposed between a first mold plate (2) and a second mold plate (4). A cavity surface (5A) or a core surface (5B) is formed on the third mold plate, and the third mold plate is supported in an insulated state by supporting means (6) in a mold-open state. And heating means (7) for heating the third mold plate in the mold open state.

In order to improve the transferability of the appearance of the molded product, it is preferable to preheat the cavity surface, but it is also possible to improve the transferability by preheating the core surface. . That is, in a normal mold plate structure, there is a cavity surface on the injection side of the molding machine, but the present invention may be applied to a mold formed by reversing the cavity surface and the core surface.

By preheating the third mold plate supported in an insulated state by heating means, The third mold plate can be preheated to a uniform temperature distribution over almost the entirety. It is advisable to select an optimal preheating temperature according to the characteristics of the material.

In the example shown in FIG. 1, the third mold plate, which has been preheated to a predetermined temperature, is moved relative to the first mold plate to close the mold, and the material melted from the molding machine is placed in the capty. Almost simultaneously, the second mold plate is pressed against the third mold plate. The third mold plate should have as small a heat capacity as possible in order to quickly heat it by the heating means and to improve the heat radiation when the second mold plate is pressed. For example, it is preferable to make the thickness of the portion where the cavity surface or the core surface is formed as thin as possible, but the molten surface flows until the molten material flows through the cavity surface or the core surface and the filling is completed. It is necessary to select a wall thickness so that heat remains in the wall. For the above reason, in the present invention, the rigidity of the third mold plate is reduced, and if the injection is started, the third mold plate is deformed by the injection pressure. Therefore, in the present invention, the second mold plate is pressed against the third mold plate at the time of the injection step to secure the rigidity of the third mold plate. By making the heat capacity of the second mold plate significantly greater than that of the third mold plate, the second mold plate not only ensures the rigidity of the third mold plate, but also It also plays a role as a heat radiating means to quickly radiate the heat of the template.

The opening / closing operation of the mold is not limited to the case where the third mold plate is moved with respect to the first mold plate to open and close, and the first mold plate is moved with respect to the third mold plate. This includes the case where the template is moved to open and close. · Since the third mold plate is pre-heated to a predetermined temperature, the material injected from the molding machine is filled to every corner of the cavity with good fluidity, and is molded at low pressure and excellent in transferability. Goods can be obtained.

It is preferable that the third mold plate is formed to have an extremely smaller heat capacity than the first mold plate and the second mold plate.

With this configuration, when the mold is closed, the heat of the third mold plate is quickly radiated to the first mold plate and the second mold plate, and the material in the cavity is quickly solidified. It can be quickly heated to the desired temperature in preparation for the next injection.

In the above-mentioned mold plate, a temperature detecting means such as a temperature sensor is provided on a third mold plate for performing preheating, and control is performed so that the third mold plate has a predetermined temperature. Do Is good.

It is preferable that the support means is a guide pin of a mold, and the guide pin supports the third mold plate and is movable with respect to the first or second mold plate.

■ In this case, if the guide pin or the bush receiving the guide pin is made of a heat insulating member (a member made of a material having a low thermal conductivity, such as ceramics), the third mold plate can be surrounded by the guide bin. It is supported thermally independent of the structure. Therefore, if a part of the third mold plate is preheated by the heating means, the heat spreads over the entire mold plate, and the entire third mold plate is preheated to a substantially uniform temperature. can do.

The third mold plate includes a thin portion having a small heat capacity including a cavity surface or a core surface, and a thick portion having a large heat capacity formed around the thin portion. The mold plate may be configured to abut at least the thin portion during injection.

With this configuration, a large amount of heat can be stored in a thick portion having a large heat capacity. Therefore, by using the heat stored in the thick portion, the time for preheating can be reduced when the third movable mold is preheated for the next injection molding.

Furthermore, by pressing the first or second mold plate against the thin portion of the third mold plate, it is possible to quickly release the heat of the material injected into the gap. Considering the balance between the amount of heat supplied from the thick part to the thin part and the amount of heat transferred from the thin part to the first or second mold plate, the volume of the thick part and the thin part is taken into account.

(Heat capacity) is preferably determined.

A heat insulating member may be provided on at least a part of the periphery of the thick part.

By doing so, it is possible to reduce heat radiation from the thick part and to keep a large amount of heat in the thick part, further increasing the preheating time by the heating means for the next injection molding. It becomes possible to shorten.

The heating means may be provided outside the third mold plate separately from the third mold plate, or may be provided integrally with the third mold plate.

In particular, when a heating means is provided integrally with the third mold plate and heat is transmitted by heat conduction, the heating means may be configured to always preheat the third mold plate. However, when performing the injection, it is preferable to stop the heating by the heating means at the same time as or immediately before the start of the injection in order to quickly solidify the material in the cavity. With this configuration, at the time of injection that requires heat radiation from the cavity, preheating is stopped to promote heat radiation, and in other cases, the third mold plate is heated by preheating. By keeping the temperature constant, the time for preheating can be eliminated or significantly reduced.

The timing of closing the mold may be such that when the injection step is started, the mold is moved from a state having a minute gap between the third mold plate and the second mold plate. In particular, when injecting the material into the cavity, the third mold plate is brought into contact with the first mold plate, and simultaneously with the start of the injection, the second mold plate is moved to the second mold plate. It is preferable that the third mold plate is brought into contact with the third mold plate and the third mold plate is pressed with a force against the injection pressure.

With this configuration, the cavity surface or the core surface can be maintained at the optimum temperature for improving the transferability until the injected material is filled in the cavity, and almost simultaneously with the completion of the injection. By promoting heat radiation from the material in the cavity, the material can be solidified in a short time. In addition, with this configuration, mold clamping is performed in two stages, and the transferability of the material can be improved. In addition, one or more air vent holes communicating with the cavity are formed in the second mold plate from the side where the second mold plate abuts, and the material is injected into the cavity. In such a case, the air may be discharged into the atmosphere through the minute gap.

With this configuration, the air in the cavity can be released more smoothly, the flow of the material in the cavity can be improved, and the transferability can be further improved.

In metal injection molding, material flows into the cavity at an injection speed several times faster than that of resin, so the effect of such air bleeding is extremely large.

When the molded product is an optical disk such as a CD or a DVD, a stamper for forming pits on the optical disk may be arranged on the first mold plate side. · By doing so, the effect of preheating on the stamper is minimized be able to.

• The material to be injected into the cavity may be a metal such as a magnesium alloy, an aluminum alloy, or a zinc alloy.

These metals have a significantly higher thermal conductivity and melting point than resin, and solidify in a very short time when they come into contact with the cavity surface or core surface.However, the solidification time is increased by preheating the cavity surface or core surface. Can be delayed, and the material can be distributed to every corner of the cavity. Therefore, it is possible to suppress the occurrence of a defect such as a defective filling or a defective transfer. The material filled in the cavity is quickly radiated by the first mold plate through the second mold plate in contact with the template and the material having high thermal conductivity itself, There is no need to lengthen the cycle time.

An outer portion for supporting the third mold plate by the support means; and an inner portion fitted to the outer portion and provided with the captivity or core surface, wherein the outer portion and the inner portion are provided. It is preferable that a gap having a size capable of absorbing the thermal expansion amount of the third mold plate due to preheating is provided in the fitting portion.

In the case where the support means is a guide pin, the guide pin is formed, for example, as two pieces at the center of the mold, and a hole in the second mold plate passing therethrough is formed in the second mold plate. May be formed in a long hole extending in the horizontal direction from the center.

With this configuration, thermal expansion due to preheating can be avoided. In the injection molding method of the present invention, as set forth in claim 22, the mold plate is a first mold plate and a second mold plate that are openable and closable, and the mold plate is the first mold plate. A third mold plate provided between the mold plate and the second mold plate, wherein a cavity surface or a core surface of the cavity is formed on the third mold plate; The third mold plate is supported in a thermally insulated state, is movable in a pressing direction and a mold closing direction, and in the mold opened state, the third mold plate is heated by a heating means, and the preheated third mold plate is heated. The mold plate is closed by moving the mold plate relatively toward the first mold plate, and is brought into contact with the third mold plate from the back of the second mold plate to perform injection molding. And cooling. Even with this method, it is possible to obtain a molded product that has sufficient transferability to all corners of the cavity while maintaining the viscosity of the material at a certain level or more.

Further, by pressing a second mold plate against the third mold plate, the third mold plate is pressed. Since the heat of the material filled in the cavity is rapidly removed through the plate, the cycle time of injection molding is not prolonged. '' Brief description of the drawings

FIG. 1 is a perspective view for explaining the inventive concept of the present invention.

FIG. 2 is a sectional view of a mold according to the first embodiment of the present invention.

FIG. 3 is an enlarged cross-sectional view of a thick portion of an intermediate mold plate supported by guide pins. FIG. 4 is a longitudinal sectional view of a mold for explaining the operation of the first embodiment of the present invention, wherein (a) shows a state in which an intermediate mold plate abuts on a fixed mold, and (b) shows a movable state. This shows a state in which the mold plate comes into contact with the intermediate mold plate and the material is injected from the sprue runner.

FIG. 5 is a longitudinal sectional view of a mold according to a second embodiment of the present invention. The fixed mold, the intermediate mold, and the movable mold plate at the timing when the molten material is injected from the sprue runner. It is a figure explaining the positional relationship of.

FIG. 6 (a) is a sectional view of a mold for explaining a third embodiment of the present invention, and FIG. 6 (b) is a plan view of a mold of a fourth embodiment of the present invention.

FIG. 7 is a cross-sectional view of a mold according to a fifth embodiment of the present invention, wherein (a) shows a mold open state, and (b) shows a state when an intermediate mold plate abuts on a fixed mold plate. Is shown. BEST MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of a mold for an injection molding machine according to the present invention will be described in detail with reference to the drawings.

[First Embodiment]

FIG. 2 is an explanatory view of a configuration of a mold according to the first embodiment of the present invention, a longitudinal sectional view thereof, and FIG. 3 is a view of a thick portion of an intermediate mold plate supported by guide pins. FIG. 4 is an enlarged cross-sectional view, and FIG. 4 is a view for explaining the operation of the mold shown in FIG. 2; (a) shows the state when the intermediate mold plate is in contact with the fixed mold; FIG. 2 is a longitudinal sectional view showing a state in which the mold is closed. 'The mold 10 of this embodiment is used for manufacturing optical disks such as CDs and DVDs.

As shown in FIG. 2, the mold 10 includes a fixed mold plate 20 as a first mold plate fixed to a main body of an injection molding machine (not shown) via a mounting plate 21. Fixed mold plate 2 A movable mold plate 40 which is a second mold plate provided to be able to move forward and backward with respect to 0; and a fixed mold provided between the fixed mold plate 20 and the movable mold plate 40. A plate 20 and an intermediate mold plate 30 which is a third mold plate movable with respect to the moving mold plate 40 are provided. In this embodiment, the cavity surface 51 5 is formed on the fixed mold 20 side, and the core surface 51B is formed on the intermediate mold plate 30.

A stamper (not shown) for forming a pit of 〇0 ゃ 13 ¥ 0 is placed on the fixed mold plate 20 side where preheating is not performed. The reason why the stamper is provided on the mold side where preheating is not performed is to protect the stamper, which requires extremely high-precision pit positioning, from the influence of thermal distortion due to preheating.

The heating means for preheating the movable mold plate 40 is provided at the standby position A of the movable mold plate 40 in the mold open state. As the heating means, an electric heating heater, a wrench, an induction heating coil or the like can be used. In this embodiment, as shown in FIG. 2, an induction heating coil 70 for heating the intermediate mold plate 30 from the outer periphery is provided at a standby position A of the intermediate mold plate 30 when the mold is opened. I have.

The stationary mold plate 20 is provided with a sprue runner 24 for injecting a molten material such as polycarbonate injected from a cylinder of the injection molding machine into the cavity 51 (see FIG. 4).

As shown in FIG. 2, the intermediate mold plate 30 has a thin portion 32 having a small heat capacity and a thick portion 31 having a large heat capacity formed on the outer periphery of the thin portion 32. ing. The core surface 5 1 B is included in the thin portion 32.

When the intermediate mold plate 30 is preheated by the induction heating coil 70, heat is quickly transmitted from the outer periphery of the intermediate mold plate 30 to the entire intermediate mold plate 30 and the injection molding is performed. It is preferable to use a metal having excellent thermal conductivity, for example, beryllium, so that the heat of the material injected into the cavity 51 may be quickly dissipated.

When the mold is closed, first, the thin portion 32 of the intermediate mold plate 30 contacts the fixed mold plate 20. At this time, the heat of the pre-heated intermediate mold plate 30 is reduced by the thin portion. 3 In order to minimize the amount of heat transferred from 2 to the fixed mold plate 20 as much as possible, and to suppress the temperature drop of the core surface 51B, the contact area between the thin portion 32 and the fixed mold plate 20 Is preferably as small as possible. However, the movable mold plate 20 is set to the intermediate mold plate Needless to say, when 30 is pressed, a contact area that does not cause plastic deformation of the intermediate mold plate 30 must be ensured.

A temperature sensor 34 for burying a temperature of the preheating of the intermediate mold plate 30 by the induction heating coil 70 is buried near the portion where the core surface 51B of the thin portion 32 is formed. ing.

At the time of preheating, a control device (not shown) of the mold 1 guides the intermediate mold plate 30 to a predetermined temperature based on the detection result of the temperature sensor 34. The control of the voltage applied to the heating coil 70 is performed.

The thick part 31 of the intermediate mold plate 30 acts as a heat storage part at the time of opening and closing. In other words, when the mold is opened after the injection is completed, the heat stored in the thick portion 31 is quickly transferred to the thin portion 32, so that the core surface 51 of the intermediate mold plate 30 is formed. B The temperature can be raised quickly. Therefore, the temperature of the core surface 51 B, which must be increased by preheating the induction heating coil 70 for the next injection molding, can be small, and the heating time for preheating can be shortened. As shown in FIG. 2, the thick portion 31 may be provided with one or more heat storage members 35 made of metals having different specific heats in order to enhance heat storage.

As shown in FIG. 4 (b), the width of the thick portion 31 is such that when the mold is closed, there is a slight gap between the fixed mold plate 20 and the movable mold plate 40. It is formed to be able to. —This is to prevent heat from moving from the thick part 31 as the heat storage part to the fixed mold plate 20 and the movable mold plate 40. Preferably, as shown in FIG. 3, a heat insulating member 33 made of ceramic or the like having excellent heat insulating properties is provided on both surfaces of the thick portion 31.

In addition, the volume (heat capacity) of the thin portion 32 is set so that the temperature of the core surface 51 B is at a temperature at which the transferability of the material is optimized by the heat transferred from the thick portion 31. It is preferable to be able to quickly release the heat of the material in the cavity 51 when the movable mold plate 40 comes into contact. Further, it is preferable that the thin portion 32 be thin for quick heat exchange as described above. Therefore, the rigidity is secured by bringing the movable mold plate 40 into contact so that the thin portion 32 is not deformed by the external force acting during opening / closing of the mold, preheating and during the injection process. So that The distribution of the thickness, heat capacity, and size of each of the thick portion 31 and the thin portion 32 forming the intermediate mold plate 30 depends on the melting point of the material to be injection-molded, the cycle time of the injection molding, It is preferable to determine the optimum one by experiments, calculations, etc., taking into account the form of the heating means. If the volume of the thick portion 31 is too large, it takes a long time for preheating. Conversely, if the heat capacity of the thick portion 31 is too small, the thick portion 31 does not sufficiently act as a heat storage portion, and it takes a long time to heat the next injection molding.

In this embodiment, a plurality of (four in this embodiment) guide pins 60 are erected on the movable mold mounting plate 41 in order to support the intermediate mold plate 30 in an insulated state. The intermediate mold plate 30 is supported by the guide pins 60.

As shown in FIG. 3, through-holes 3 la are formed in the thick portion 31 of the intermediate mold plate 30 at a plurality of locations (four locations in this embodiment) in accordance with the positions of the guide pins 60. ing. A spring 63 is provided between the movable mold plate 40 and the intermediate mold plate 30 as an urging means, and the intermediate mold plate 30 is always attached to the fixed mold plate 20 side. I'm going. The movable mold plate 40 is formed with a receiving hole 46 for a guide pin 60 and a spring 63. As shown in the figure, a sleeve 47 made of a material having excellent heat insulation such as ceramic is fitted into the through hole 3 la, and the sleeve 47 is inserted between the guide pin 60 and the intermediate mold plate 30. It is preferable to improve the heat insulating property of the intermediate mold plate 30 by interposing the metal mold. Further, instead of providing the sleeve 47 having excellent heat insulating properties, the guide pins 6 • 0 may be formed of a material such as ceramic.

The movable mold plate 40 as the second mold plate is brought into contact with the intermediate mold plate 30 at the time of the injection step, and presses the intermediate mold plate 30 with a predetermined pressing force to the fixed mold plate 20 side. Not only ensures its rigidity but also acts as a heat radiating member for promoting heat radiation of the intermediate mold plate 30. Therefore, it is preferable that the heat capacity of the movable mold plate 40 be much larger than that of the intermediate mold plate 30. Further, in order to promote heat radiation, it is preferable to form a flow passage for allowing a cooling fluid to flow.

In this embodiment, the heating means for preheating the movable mold plate 40 is provided at the standby position A of the movable mold plate 40 when the mold is opened, and heats the movable mold plate 40 from the outer peripheral side. Induction heating coil 70.

When the induction heating coil 70 preheats the thick part 31, a part of the heat is Then, the core surface 51 B of the intermediate mold 30 is heated to a substantially uniform temperature over the entire surface.

The optimum temperature of the intermediate mold plate 30 preheated by the induction heating coil 70 is determined in consideration of the melting point of the material of the molded product and the temperature drop from the stop of heating to the closing of the mold and the start of injection. .

A hole 26 is formed in the fixed mold plate 20 at a position corresponding to the guide pin 60 so that the guide pin 60 can be guided into the hole 26 when the mold is closed. That is, at the time of closing the mold, the intermediate mold plate 30 moves toward the fixed mold plate 20 unless guided by the guide pins 60.

A convex portion 43 is formed on one side of the movable mold plate 40. When the convex portion 43 contacts the thin portion 32 of the movable mold plate 40 when the mold is closed, a gap for heat insulation is formed between the thick portion 31 and the movable mold plate 40. You. The contact surface of the convex portion 43 contacting the thin portion 3 2 is larger than the area of the core surface 5 10 B formed in the thin portion 32, and can contact the thin portion 32 entirely. It is formed as a flat surface so that it can be formed. Next, the operation of the mold plate having the above configuration will be described with reference to FIGS. 2 and 4. At the standby position A (see FIG. 2) in the mold open state, a voltage is applied to the induction heating coil 70 provided outside the thick portion 31 of the intermediate mold plate 30 to remove the thick portion 31. Preheat. The heat from the induction heating coil 70 is transmitted from the thick portion 31 to the thin portion 32, and heats the core surface 51B (thin portion 32) of the intermediate mold plate 30 almost uniformly over the entire surface. I do. The temperature of the thin portion 32 is monitored by a temperature sensor 34. Based on the temperature detected by the temperature sensor 34, a control device (not shown) controls a voltage applied to the induction heating coil 70 and the like.

When the thin portion 32 is preheated to a predetermined temperature, a driving body (not shown) is driven to move the movable mold plate 40 and the intermediate mold plate 30 toward the fixed mold plate 20. Since the intermediate mold plate 30 is supported in front of the movable mold plate 40 by the guide pins 60, the intermediate mold plate 30 is fixed to the fixed mold plate 20 before the movable mold plate 40. (See Fig. 4 (a)). At this time, the contact area between the fixed mold plate 20 and the thin portion 32 is relatively small as compared with the area of the core surface 50B. The amount of heat transferred to the template 20 is small, and the temperature of the core surface 50B does not decrease so much. The driving body advances the movable mold plate 40 against the urging force of the spring 63, and brings the movable mold plate 40 into contact with the intermediate mold plate 30 (see FIG. 4 (b)). ).

At this time, between the movable mold plate 40 and the thick portion 31 of the intermediate mold plate 30 and the fixed mold

'Since there is a gap between the mold plate 20 and the thick part 3 1 of the intermediate mold plate 30, the thick part 3 which is a heat storage part in the movable mold plate 40 and the fixed mold plate 20 The heat stored in 1 can be prevented from moving.

When or immediately before the movable mold plate 40 comes into contact with the intermediate mold plate 30, the molten material is injected into the cavity 51 from the molding machine. The timing of the start of the injection of the material can be determined, for example, based on the output of a start signal for starting the injection.

Since the intermediate mold plate 30 is pre-heated, the material injected from the molding machine can maintain a certain level of viscosity for a relatively long time. As a result, it is possible to obtain a molded product with high material transferability and a high transferability to every corner of the cavity 51.

Since the movable mold plate 40 is maintained at a temperature sufficiently lower than the temperature of the intermediate mold plate 30 and has a heat capacity much larger than that of the intermediate mold plate 30, it is thin after the end of the injection process. The heat of the material in the section 32 and the cavity 51 is quickly transferred to the movable mold plate 40, and the material is rapidly solidified.

Since the thin-walled part 3 2 with small heat capacity is mainly brought into contact with the movable mold plate and cooled, the temperature of the molten material injected into the cavity 51 can be quickly lowered, and the cycle time of injection molding The problem of extending the length does not occur.

After the material is solidified, a movable body (not shown) is driven to retract the movable mold plate 40 and the intermediate mold plate 30 from the fixed mold plate 20 to open the mold. As a result, the molded product comes off the cavity 51. .

Then, the intermediate mold plate 30 returning to the standby position A is heated by the induction heating coil 70, and the core surface 51B is maintained at a constant temperature. Thereafter, the above procedure is repeated.

In the first embodiment, since the molded product is a CD or DVD, the cavity surface 51A of the cavity 51 is formed on the fixed mold plate 20 side. • In the molded product, the cavity surface 51A may be formed on the intermediate mold plate 30 side. [Second embodiment]

Next, a second embodiment of the present invention will be described with reference to FIG.

FIG. 5 is a cross-sectional view of a mold according to a second embodiment of the present invention.

FIG. 9 is a view for explaining a positional relationship among a fixed mold plate 20, an intermediate mold plate 30 and a movable mold plate 40 when a molten material is injected from 24.

Since the basic configuration of the mold 1 of this embodiment is the same as that described in the previous embodiment, in FIG. 5, the same parts and members as those in the first embodiment are shown in FIGS. The same reference numerals as those in the drawings are attached, and the detailed description is omitted.

In the second embodiment, the material injected into the cavity 52 is a metal such as a magnesium alloy, an aluminum alloy, and a zinc alloy.

A cavity surface 52A is formed on the intermediate mold plate 30, and an induction heating coil 72 serving as a heating means is provided on the intermediate mold plate behind the portion where the cavity surface 52A is formed.

It is provided integrally with 30. The temperature control of the intermediate mold plate 30 by the induction heating coil 72 is detected by the temperature sensor 35 embedded near the cavity surface 52 A of the intermediate mold plate 30 as in the previous embodiment. This is performed based on this detection result.

The preheating of the intermediate mold plate 30 by the induction heating coil 72 is preferably performed at all times. However, when the material in the cavity surface 52A is solidified, the preheating by the induction heating coil 72 should be stopped in order to promote heat radiation from the material.

As described above, based on the output of the start signal for starting the injection, the timing of starting the injection of the material may be determined, and the preheating by the induction heating coil 72 may be stopped simultaneously with the start of the injection.

The intermediate mold plate 30 of this embodiment is provided with a plurality (for example, four) of the protrusion pins 58 for protruding the molded product and a uniform interval near the periphery of the cavity surface 52A. Then, by driving a driving body (not shown) provided on the movable mold plate 40 side, the tip of the protruding pin 58 protrudes from the hole 54 formed in the cavity surface 52A, and the molded product is protruded. Like that.

Although not shown in the figure, there is a small gap between the protruding pin 58 and the inner peripheral surface of the hole 54 that allows the air of the cavity ^ 52 to pass through. When the material M is injected into the cavity 52 from 4, A part of the air is discharged to the back side of the intermediate mold plate 30 (the movable mold plate 40 'side) through the minute gap.

In order to allow the air that has passed through the minute gap to be smoothly released into the atmosphere through the space between the intermediate mold plate 30 and the movable mold plate 40, the sprue runner 2 is used in this embodiment. The timing of injecting the molten material from 4 is slightly earlier than the timing of the movable mold plate 40 of the first embodiment. That is, immediately before the movable mold plate 40 comes into contact with the intermediate mold plate 30, the injection of the material M is started, and at this time, a gap is formed between the movable mold plate 40 and the intermediate mold plate 30. S is formed.

In this way, at the same time as the molten material M is injected from the sprue runner 24, a part of the air in the cavity 52 passes between the protruding pin 58 and the inner peripheral surface of the hole 54. Then, it flows to the back side of the intermediate mold plate 30, and is further released into the atmosphere through a gap S between the intermediate mold plate 30 and the movable mold plate 40.

In FIG. 5, the gap S is shown in an enlarged manner for convenience of explanation, but in practice, 'is set so that the gap S is about several mm to several mm when starting injection. The timing is adjusted.

In the mold plate of this embodiment, the air in the cavity 52 is smoothly discharged to the atmosphere, thereby further improving the flow of the material M in the cavity 52, increasing the flow length, and improving the transferability. It is possible to obtain a molded product having a high degree of performance.

In the present embodiment, since the heat capacity of the intermediate mold plate 30 is large, it is suitable for forming a metal such as magnesium having a relatively long forming cycle. Even if the heat capacity of the intermediate mold 30 is large, the material injected into the cavity 52 is a metal with high thermal conductivity, so the heat of the intermediate mold plate 30 is only from the movable mold plate 40. Instead, a large amount of heat is radiated from the fixed mold plate 20 via the material in the cavity 52.

Further, by performing the mold closing at the above timing, so-called “two-stage mold closing” is performed, so that the transferability of the material can be further improved. Furthermore, in metal injection molding, as the material flows into the cavity at an injection speed several times higher than that of resin, the above-mentioned effect of air release is extremely large.

These are particularly effective for thin molded products such as personal computer lids, which have become mainstream in recent years. [Third and fourth embodiments]

Next, third and fourth embodiments of the present invention will be described with reference to FIG. When the intermediate mold plate 30 is preheated, distortion occurs in the intermediate mold plate and the thin portion 32 due to thermal expansion. Such distortion is unacceptable for molded products that require high dimensional accuracy and shape accuracy such as CD and DVD.

Therefore, in the third embodiment shown in FIG. 6 (a), the intermediate mold plate 300 is divided into an outer portion 301 supported by guide pins 60 (see FIG. 2) and an outer portion 301 31 and an inner portion 302 having a cavity 5100.

On the inner periphery of the outer portion 301, a groove 304 is formed over the entire periphery. Then, the outer peripheral edge of the inner portion 302 is fitted into the groove 304.

As shown in the figure, between the bottom of the groove 304 and the outer periphery of the inner portion 302, thermal expansion of the outer portion 301 and inner portion 302 due to preheating was considered. A gap of dimension 305 is pre-formed. Then, when the intermediate mold plate 300 is preheated to a predetermined temperature by a heating means (not shown), the gap 3005 is formed due to the thermal expansion of the outer portion 301 and the inner portion 302. Has disappeared.

Note that the outer portion 301 may be formed of a heat insulating member such as a ceramic, and the inner portion 302 may be integrally provided with the induction heating coil 72 as described in the second embodiment.

This makes it possible to make the inner part 302 almost completely thermally independent of the other mold plates. In addition, since the thermal expansion of ceramic is smaller than that of metal, the size of the gap 305 can be reduced.

In the intermediate mold plate 310 of the fourth embodiment shown in FIG. 6 (b), a hole 315 through which the guide pin 60 passes is formed along the outer peripheral edge of the intermediate mold plate 310. Are formed at equal intervals. Each of the holes 3 15 is formed as an elongated hole extending radially from the center of the intermediate mold plate 3 10. The length of the hole 3 15 in the longitudinal direction is determined in consideration of the amount of thermal expansion of the intermediate mold plate 3 10 due to preheating.

When the intermediate mold plate 310 is preheated by a heating means (not shown), the intermediate mold plate 310 supported by the guide bin 60 is radiated from the center of the intermediate mold plate 310 in the radial direction. Thermal expansion occurs at almost the same ratio. The hole 3 15 through which the guide pin 60 passes is formed in the shape of a long hole having a long axis in the same direction as the direction of the thermal expansion. The positional relationship between the cavities 24 and the cavities 5 20 can be kept constant.

FIG. 6 (b) shows a circular movable mold 9, but the same applies to other rectangular movable molds. In this case, two guide pins are provided at the center of the mold, and the holes of the third mold plate passing therethrough are formed into elongated holes extending horizontally from the center of the third mold plate. It is good to form.

Although the cavity surface 52OA is formed on the intermediate mold plate 310, it may be formed on the fixed mold plate side as described above.

[Fifth Embodiment]

Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 7 is a longitudinal sectional view for explaining the configuration of a mold according to a fifth embodiment of the present invention. FIG. 7 (a) shows a mold in an open state, and FIG. 7 (b) shows an intermediate mold attached to a fixed mold plate. This shows the case when the plate is in contact.

The mold configuration of the fifth embodiment is basically the same as the mold of the first embodiment, except that the intermediate mold plate shown in FIG. 6 (a) is used. I have. Therefore, the same portions and the same members as those of the first and third embodiments are denoted by the same reference numerals, and detailed description is omitted.

In this embodiment, an induction heating coil 75 as a heating means is provided on one surface (the surface of the convex portion 43) of the movable mold plate 40 facing the intermediate mold plate 300.

Between the surface of the movable mold plate 40 provided with the induction heating coil 75 and the intermediate mold plate 300, the intermediate mold plate 300 is thermally independent, and the induction heating coil 75 A gap S ′ is provided to allow induction heating of the intermediate mold plate 300 by the method.

'When closing the mold, the movable mold plate 40 and the intermediate mold plate 300 move to the fixed mold plate 20 while keeping the gap S' as shown in Fig. 7 (b). I do. After the intermediate mold plate 300 contacts the fixed mold plate 20 and immediately before the movable mold plate 40 contacts the intermediate mold plate 300, the intermediate mold using the induction heating coil 75 The heating of plate 300 is stopped.

According to this embodiment, the intermediate mold plate 300 can be heated by the induction heating coil 75 until just before injection, and the core surface 5100B can be kept at a certain temperature or higher. Also, compared with the case where the induction heating coil is provided on the intermediate mold plate, the heat capacity of the intermediate mold plate 300 can be made much smaller, so that heat exchange can be performed advantageously. There are advantages.

Also according to this embodiment, since the core surface 5100B of the intermediate mold plate 300 is preheated by the induction heating coil .75, the material spreads to every corner of the cavity 5100, and the transferability is improved. A molded article having a good quality can be obtained. Further, since the heat capacity of the intermediate mold plate 300 can be made extremely small as compared with the fixed mold plate 20 and the movable mold plate 40, the heat of the material filled in the cavity 5100 can be reduced. Quickly dissipates heat and the material solidifies in a short time.

Although the preferred embodiments of the present invention have been described, the present invention is not limited to the above embodiments.

For example, in the above embodiment, the first mold plate is described as a fixed mold plate, and the second mold plate is described as a movable mold plate. However, the first mold plate is described as a movable mold plate. Then, the second mold plate may be used as a fixed mold plate.

Further, in the above embodiment, for convenience of explanation, only one molded article is molded from one mold, and a case where the present invention is applied to a so-called one-piece mold has been described as an example. However, the present invention is not limited to such single-cavity molding, but can be applied to a multi-cavity mold plate. Although the case where only one sprue runner is provided for each cavity has been described, the present invention can be applied to a mold having a plurality of sprue runners in one cavity.

Further, in the above embodiment, the driving body for driving the movable mold plate and the driving body for driving the intermediate mold plate may be separate or common. Also, the case where only one sprue runner is provided per capita has been described. However, the present invention can be applied to a mold in which a plurality of sprue runners are provided in one cavity. '' In addition, although the description has been given assuming that the injection start timing is determined based on the start signal, the injection start timing is determined based on the detection results of the cavity and the temperature sensor embedded in the slug pocket of the cavity. It is also possible. As described above, according to the present invention, a molded article having excellent transferability can be obtained by preheating the cavity surface or the core surface to a predetermined temperature.

In addition, this preheating can be performed promptly and a mold with a large heat capacity By pressing the plate, the material injected into the cavity can be cooled quickly, so that the cycle time of injection molding is not extended. Industrial applicability

The present invention is applicable to all injection molding machine dies such as cold runner type, hot and runner type, die casting, etc., as long as they are molds of injection molding machines that form molded products by injecting materials into cavities. Is possible. Further, the present invention can be applied to not only resin but also metal injection molding.

Claims

The scope of the claims

1. In a mold of an injection molding machine having a mold plate that can be opened and closed and a cavity formed in the mold plate,

A thin template that is formed independently of the mold plate and includes a cavity surface or a core surface of the cavity;

Heating and holding means for heating and holding so that the cavity surface or the core surface formed on the template becomes a predetermined temperature at the time of injection,

When performing injection molding, the mold plate is brought into contact with the mold plate, and deformation of the mold plate is suppressed by the mold plate and cooling of the mold plate is performed.

A mold for an injection molding machine.

2. The mold plate is a first mold plate and a second mold plate that can be freely opened and closed, and the mold plate is provided between the first mold plate and the second mold plate. Forming a cavity surface or a core surface of the cavity on the third mold plate;

In the mold open state, the third mold plate is supported in an insulated state, and is movable in the mold closing direction,

2. A mold for an injection molding machine according to claim 1, further comprising a heating means for heating said third mold plate in a mold open state.

3. The third mold plate includes a thin portion having a small heat capacity including a capity surface or a core surface, and a thick portion having a large heat capacity formed around the thin portion. 3. The mold for an injection molding machine according to claim 2, wherein the second mold plate is in contact with at least the thin portion during injection.

4. The mold for an injection molding machine according to claim 2, wherein the heating means is provided on the third mold plate.

5. The mold of an injection molding machine according to claim 2, wherein the heating means is provided separately from the third mold plate.

6. The mold for an injection molding machine according to any one of claims 2 to 5, wherein the heating means is an induction heating coil.

7. The heating means is an induction heating coil provided in the second mold plate, and when preheating the third mold plate, a gap capable of induction heating the third mold plate is formed. 6. The mold for an injection molding machine according to claim 5, wherein the mold is provided between a second mold plate and the third mold plate.

8. The molded product is an optical disk, and a stamper for forming pits on the optical disk is arranged on the first or second mold plate side. Item 7. A mold for an injection molding machine according to any one of the above items. ·

9. The mold for an injection molding machine according to any one of claims 2 to 7, wherein the material to be injected into the cavity is a metal.

'10. The third mold plate comprises an outer portion supported by the support means, and an inner portion fitted to the outer portion and provided with the cavity surface or the core surface, and the outer portion 10. A gap between the fitting portion of the third mold plate and the inner portion, the gap being large enough to absorb a thermal expansion amount of the third mold plate due to preheating. A mold for an injection molding machine according to any one of the above.

11. The mold for an injection molding machine according to claim 10, wherein said outer portion is formed of ceramic. .

12. When the support means is a guide pin, the hole of the third mold plate through which the guide pin passes is formed as an elongated hole extending radially from the center of the third mold plate. The mold for an injection molding machine according to any one of claims 2 to 11, characterized in that:

1 3. In an injection molding method using a mold having a mold plate that can be opened and closed and a cavity formed in the mold plate,

A thin plate including a captivity surface or a core surface of the first cavity is made independent of the mold plate,

Maintaining the cavity surface or the core surface formed on the template at a predetermined temperature during injection,

When performing injection molding, the mold plate is brought into contact with the mold plate, deformation of the mold plate is suppressed by the mold plate, and the mold plate is cooled.

An injection molding method characterized by the above-mentioned.

1 4. The mold plate is a first mold plate and a second mold plate that can be freely opened and closed, wherein the mold plate is provided between the first mold plate and the second mold plate. Forming a cavity surface or a core surface of the cavity on the third mold plate;

In the mold open state, the third mold plate is preheated by heating means,

The preheated third mold plate is relatively moved toward the first mold plate to close the mold,

Bringing the second mold plate into contact with the back surface of the third mold plate to inject and cool the material;

14. The injection molding method according to claim 13, wherein:

15. When injecting material into the cavity, the third mold plate is brought into contact with the first mold plate, and simultaneously with the start of the injection, the second mold plate is 15. The injection molding method according to claim 14, wherein the third mold plate is brought into contact with a third mold plate, and the third mold plate is pressed with a force against injection pressure.

16. The heating means is an induction heating coil, and the induction heating coil is provided on the second mold plate, and when the third mold plate is pre-heated, the third metal by the induction heating coil is used. At a position separated from the second mold plate by a distance capable of preheating the template, The injection molding method according to claim 14, wherein the third mold plate is located.

17. The molded product is an optical disk, and a stamper for forming pits on the optical disk is arranged on the first mold plate side. Item 13. The injection molding method according to any one of the items.

18. The mold for an injection molding machine according to any one of claims 14 to 16, wherein the material to be injected into the cavity is a metal. ·