JPH09300357A - Mold heating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the irregularity of the temp. distribution of a mold by setting the center part of a high frequency induction coil to a conductor free part and extending the conductor of other high frequency coil to the conductor free part. SOLUTION: Two high frequency induction coils 1a, 1b are attached on a support member 4 and respectively connected to separate high frequency power supplies 2a, 2b. The center part of the coil 1a is set to a conductor free part 3a omitted from a conductor constituting the coil 1a and the leading end of the double conductor on the outer peripheral side of the coil 1b is incorporated in the conductor free part 3a to extend out in a chevron shape. By performing the heating of the mold surface corresponding to the center part 3a of the coil 1a by the conductor of the coil 1b, the heating state of the center part 3a is compensated and the irregularity of the temp. distribution on the surface of the mold can be corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal used for high-frequency induction heating of a mold surface prior to injection of resin in order to improve the surface condition of a molded product in injection molding of thermoplastic resin. Mold heating device

[0002]

2. Description of the Related Art Conventionally, in injection molding, the mold surface has been heated prior to injection of resin.
This heating is usually performed by a high frequency induction heating device. For example, Japanese Patent Application Laid-Open No. 1-262107 discloses that a high frequency induction coil is embedded in a mold and the surface of the mold is heated thereby. In addition, Japanese Unexamined Patent Publication
-220825 discloses that a plurality of series of high frequency induction coils are arranged and each is independently controlled to control the temperature distribution on the mold surface.

[0003]

By the way, the most common mold heating apparatus is one high-frequency induction coil connected to one high-frequency power source as shown in the above-mentioned Japanese Patent Laid-Open No. 1-262107. I have.

However, in the case of such a mold heating device, there is a problem that the temperature distribution on the mold surface tends to vary. Especially, there is a problem that the temperature of the center of the mold (the center of the high frequency induction coil) becomes lower than that of the periphery thereof, which adversely affects the quality of the obtained product. In addition, such a variation in temperature distribution becomes more prominent as the mold becomes larger.

On the other hand, the mold heating apparatus disclosed in Japanese Unexamined Patent Publication No. 2-220825 independently controls a plurality of series of high frequency induction coils, but basically, the single high frequency induction coil is used. Similar to the case of arranging, the temperature distribution on the surface of the mold is unevenly distributed among a plurality of high frequency induction coils.

The present invention has been made in view of such conventional problems, and it is intended to reduce the variation in the temperature distribution on the surface of the mold, which occurs between the central portion of the high frequency induction coil and its peripheral portion. With the goal.

[0007]

Therefore, in the present invention, as shown in FIG. 1, each high-frequency induction coil 1a, 1b is connected to a separate high-frequency power source 2a, 2b, and the central portion thereof is a non-conductive wire portion 3a. For the high frequency induction coil 1a
The conductor wire on the outer peripheral side of the other high frequency induction coil 1b is extended.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An example of the present invention will be described with reference to FIG.

In the figure, reference numeral 4 denotes a heat-resistant support member made of a non-magnetic material, and two high frequency induction coils (hereinafter abbreviated as "coils") 1a and 1b are mounted on the support member 4. Each coil 1a, 1b has a separate high frequency power source 2
It is connected to a and 2b. The high frequency power supplies 2a and 2b are
It is rectified into direct current through an inverter.
A device that strongly oscillates at 0 V / 150 A and an output frequency of 30 to 50 KHz is used. The coil 1a on the left side of the drawing is drawn by a solid line, and the coil 1b on the right side is drawn by a broken line, but this is for making it easier to distinguish the two coils 1a and 1b in the drawing. Needless to say, is also composed of a series of conducting wires.

The central portion of the coil 1a on the left side of the drawing is a non-conductive wire portion 3a in which the conductive wire forming the coil 1a is omitted. Further, in the non-conductive wire portion 3a, the tips of the double conductive wires on the outer peripheral side of the coil 1b on the right side in the drawing extend into the non-conductive wire portion 3a and extend in a chevron shape.

As shown in FIG. 3, the illustrated mold heating apparatus is usually attached to an arm 5 and is inserted through the arms between the opened molds, and the coil 1 is placed on the surface of the mold.
The mounting surfaces of a and 1b are moved closer to each other, and the high frequency power source 2
The surface of the die is heated by supplying a high frequency from a, 2b to the coils 1a, 1b.

In particular, the die heating apparatus shown in the figure is capable of uniformly heating the die surface corresponding to the coil 1a portion on the left side of the figure. That is, since the conductor on the outer peripheral side of the other coil 1b is extended to the center of the coil 1a where the heating temperature becomes low, the heating of the die surface corresponding to the center of the coil 1a is performed by the conductor of the coil 1b. Is performed by the presence of the above, and thereby the heating state of the central portion of the coil 1a is supplemented, and the variation of the temperature distribution on the die surface on the coil 1a side is corrected.

The reason why the variation in the temperature distribution as described above is corrected is not always clear, but the present inventors presume as follows. That is, as shown in FIG. 4, when only one coil 1 connected to one high-frequency power source 2 is provided, as in the conventional case, the conductors that flow in the opposite direction to the central portion of the coil 1 are connected to each other. Are regularly located close to each other, and the magnetic forces cancel each other out, making it difficult to raise the temperature. On the other hand, when the coils 1a and 1b are arranged as shown in FIG. 1, in the coil 1a, the conductors in which current flows in the opposite direction are separated by the non-conductor portion 3a, and the conductors in which current flows in the opposite direction are close to each other. It is conceivable that the regularity of the magnetic field is broken and the cancellation of the magnetic force is alleviated to prevent insufficient temperature rise in the central portion of the coil 1a.

In the example shown in FIG. 1, the conductive wire on the outer peripheral side of the coil 1b is extended to the non-conductive wire portion 3a of the coil 1a, but this may be the conductive wire on the inner peripheral side of the coil 1b. However,
In order to avoid the overlapping of the conductors of the coil 1b and improve the heating efficiency, it is preferable to extend the conductor on the outer peripheral side of the coil 1b. Further, it is preferable that the conductive wire extending into the non-conductive wire portion 3a is double or more so that the mold surface corresponding to the central portion of the coil 1a can be effectively heated.

In the example shown in FIG. 1, two high frequency power supplies 2a and 2b and two coils 1a and 1b are used.
It is also possible to use three or more high frequency power supplies 2a, 2b, ... And three or more coils 1a, 1b ,. However, it is preferable to use two high-frequency power sources 2a and 2b and two coils 1a and 1b in order to suppress the facility burden as much as possible. In particular, the example shown in FIG. 1 is configured so that the heating state on the coil 1a side can be made uniform as described above, but which region is to be made into a uniform heating state depends on the shape of the mold, etc. It may be appropriately selected depending on the molding conditions.

Next, another example of the present invention will be described with reference to FIG.

Two coils 1a and 1b are mounted on the support member 4, and each of the coils 1a and 1b is connected to different high frequency power sources 2a and 2b, respectively, which is the same as that described with reference to FIG. Is.

The central portion of both coils 1a and 1b is the coil 1
non-conductive wire portions 3a, 3 in which the conductive wires forming a, 1b are omitted
b. In the non-conductive wire portion 3a of the coil 1a on the left side of the drawing, a quadruple conductive wire portion on the outer peripheral side of the coil 1b on the right side of the drawing extends in a mountain shape and enters. In addition, the coil 1b on the left side of the drawing is attached to the non-conductive wire portion 3b of the coil 1b on the right side of the drawing.
The quadruple conductor part on the outer peripheral side of a extends and enters in a mountain shape. That is, the coil 1a or 1b is such that the other conductive wire extends to one of the non-conductive wire portions 3a or 3b. Further, the arrangement of the conductor wires of the entire coils 1a and 1b is substantially symmetrical vertically and horizontally.

In the case of the example shown in FIG. 2, both coils 1a,
The insufficient temperature rise in the central portion of 1b is compensated for by the presence of the conductor wires extending from the other coil 1a or 1b, and the arrangement of the conductor wires is substantially symmetrical vertically and horizontally,
The heating temperature of the die surface can be made substantially uniform over almost the entire surfaces of both coils 1a, 1b.

As shown in FIG. 3, the mold heating apparatus described with reference to FIGS.
It will be installed and used in. That is, FIG.
As shown in FIG. 5, the mold heating device attached to the arm 5 is inserted between the opened molds, and the mounting surfaces of the coils 1a and 1b are brought close to the mold surface side to be heated, and the coils 1a and 1b are heated. The mold surface is heated by supplying a high frequency to the mold. For example, when heating only one surface of the male die and the female die, one die heating device attached to the arm 5 as shown in FIG.
The attachment surfaces of a and 1b may be brought close to the surface of the male or female mold to be heated. When heating both the male and female surfaces at the same time, two mold heating devices attached to the arm 5 as shown in FIG. 3 are prepared, and the attaching surfaces of the coils 1a and 1b are placed outside, respectively. They may be positioned back to back so that the mounting surfaces of the coils 1a and 1b can simultaneously approach the male and female surfaces.

By the way, if the heating work of the mold continues for a long time, the supporting member 4 and the arm 5 also become considerably hot, and it becomes difficult to keep the work safety. In order to reduce this, it is preferable that the support member 4 has a heat insulating material 6 sandwiched between the support members 4 to suppress heat conduction to the back side. As the heat insulating material 6, a non-magnetic material having a low thermal conductivity may be used, and for example, wood, bakelite or the like may be used, but if ferrite having an insulating property and a high magnetic permeability is used, It is preferable because heat conduction to the back side can be greatly suppressed. When this ferrite is used, even if the back surface of the support member 4 or the arm 5 is raised to about 200 ° C. with other materials, it is possible to suppress it to about 40 ° C.

[0022]

【Example】

Example 1 FIG. 5 shows a temperature distribution when the die surface is heated under the following conditions using the die heating apparatus in the state of the coils 1a and 1b as shown in FIG. 5A shows the case where the heating time is 5 seconds, and FIG. 5B shows the case where the heating time is 7 seconds.

Size of the support member 4: 120 mm × 180
mm Number of windings of the coils 1a and 1b: 8 Distance between mold heating device and mold surface: 5 mm Comparative Example 1 Typical example using one high frequency power source 1 and one coil 2 as shown in FIG. FIG. 6 shows a temperature distribution when the mold surface is heated using the conventional mold heating device under the following conditions.

Size of the supporting member 4: 220 mm × 220
mm Number of windings of the coils 1a and 1b: 16 Heating time: 10 seconds Interval between mold heating device and mold surface: 5 mm

[0025]

EFFECTS OF THE INVENTION The present invention is as described above, and even with a particularly large mold, the surface of a desired range can be heated almost uniformly, and this uniform heating region can be set arbitrarily. Since it can be set to, it is easy to obtain a product with excellent quality. Further, in particular, if ferrite is interposed in the support member 4, it is possible to prevent excessive temperature rise on the back side of the support member 4 and the arm 5, and it is easy to ensure the safety of work.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a mold heating apparatus according to the present invention.

FIG. 2 is an explanatory view showing another example of the mold heating apparatus according to the present invention.

FIG. 3 is a view showing a state in which the mold heating device according to the present invention is attached to an arm.

FIG. 4 is an explanatory diagram of a mold heating device used in Comparative Example 1.

5 is a diagram showing a temperature distribution measured in Example 1. FIG.

6 is a diagram showing a temperature distribution measured in Comparative Example 1. FIG.

[Explanation of symbols]

 1, 1a, 1b High-frequency induction coil 2, 2a, 2b High-frequency power source 3a, 3b Non-conductive wire part 4 Supporting member 5 Arm 6 Insulating material 7 Mounting tool

Claims (5)

[Claims] 1. At least two high-frequency power supplies and at least two high-frequency induction coils connected to each high-frequency power supply, wherein at least one high-frequency induction coil has a non-conductor portion at its center. A die heating device, wherein a lead wire of another high frequency coil is extended to a non-lead wire portion. 2. A high-frequency induction coil having two high-frequency power supplies and two high-frequency induction coils connected to the respective high-frequency power supplies, wherein the central parts of both high-frequency induction coils are non-conductive wire parts. 2. A die heating device, wherein the lead wires of the other high-frequency induction coil are mutually extended to the non-lead wire portion. 3. The conductor wire of another high frequency induction coil extending to the non-conductor portion of one high frequency induction coil is a conductor wire on the outer peripheral side of the other high frequency induction coil. 2 mold heating device. 4. The mold heating apparatus according to claim 1, wherein a conductor wire of another high frequency induction coil extending to a non-conductor portion of one high frequency induction coil is double or more. 5. The support member on the rear side of the high frequency induction coil,
The mold heating device according to any one of claims 1 to 4, wherein ferrite is interposed as a heat insulating material for suppressing heat conduction to the back side.