JPH069728Y2 - Mold heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a die heating device for preheating a die for light alloy casting.

[Prior Art] A method of induction heating a dielectric using a high frequency or low frequency induction heating coil is already known in various industrial fields. Further, the temperature control of the dielectric to be heated is performed in Japanese Patent Publication No. 60-45583 or Japanese Patent Publication No. 62-76.
As disclosed in Japanese Patent Publication No. 77, etc., the output of an inverter device or the like that sequentially detects the current temperature of the heating target by a temperature detection means provided to detect the temperature of the heating target and supplies electric power to the induction heating coil. It is common to compensate for the deviation between the current temperature of the heating target and the heating target temperature by automatically adjusting the frequency.

A mold heating device in which a heater plate containing an induction coil is attached to the back of the mold to preheat the temperature has already been proposed as Japanese Utility Model Publication No. 59-143563.

[Problems to be solved by the invention] However, when the dielectric material to be heated is heated to a high temperature such as preheating of a die for light alloy casting, the induction heating coil itself is overheated and an insulation coating is applied. In some cases, damage is caused to the coil, and in order to prevent this, it is necessary to dispose a forced cooling means for cooling the induction heating coil. Therefore, it is difficult and expensive to manufacture a complicated small coil, and it has been said that the heating method by induction heating is industrially unsuitable as a mold heating device such as a casting mold.

In addition, since the temperature detection device is installed to measure the temperature of the object to be heated, when heating other objects to be heated, protect the heating device by removing and installing the heating device. It is necessary to change the set value of the temperature detection device, and its loading and unloading is troublesome, and since overheating is detected through the object to be heated, it is not possible to immediately and surely detect overheating of the induction heating coil. Is.

Usually, a heating device using gas combustion or a heating wire is used as a preheating means for casting molds, but there are problems in terms of yield reduction of castings, shortening of mold life, work safety, etc. Was dissatisfied.

Also, the one that preheats from the back of the mold has poor thermal efficiency,
It has a drawback that the preheating time becomes long.

The object of the present invention is to eliminate these drawbacks of the prior art, to detect the temperature of the induction heating coil by passing, and to accurately detect the temperature of the induction heating coil without being influenced by the surrounding conditions. Precisely prevent heating in advance, the induction heating coil together with the temperature sensor can be easily attached to other molds, there is no need to forcibly cool the induction heating coil, it is small and inexpensive, and more preferably, It is an object of the present invention to provide a mold heating device that has good thermal efficiency during preheating and that can perform preheating work according to the characteristics of the mold.

[Means for Solving the Problem] In order to eliminate the need for forced cooling of the induction heating coil, the induction heating coil connected to the thyristor inverter and the induction heating coil for detecting the current temperature of the induction heating coil are used. The thyristor inverter is connected to the temperature sensor built in the coil and the temperature sensor and the thyristor inverter, and drives the thyristor inverter to keep the current temperature of the induction heating coil detected by the temperature sensor within a safe use temperature range. And a microcomputer for controlling.

In order to improve the thermal efficiency at the time of preheating, in addition to the above-mentioned configuration, the induction heating coil or the shape of the dielectric heat medium which is fitted with the induction heating coil and engages with the mold is made to have an uneven shape on the mold fitting surface. Form by copying.

In order to enable preheating work according to the characteristics of the mold and to eliminate waste of power, a plurality of induction heating coils that engage with the concave and convex shapes of each part of the mold fitting surface are provided. A timer switch for each induction heating coil is interposed between the thyristor inverter and each timer switch and a control device for controlling the energization time to the induction heating coil are connected to each other.

Also, by using a thyristor inverter whose frequency can be changed arbitrarily, preheating work according to the characteristics of the mold is possible.

The induction heating coil is coated with an inorganic insulating coating agent.

[Operation] The microcomputer detects the current temperature of the induction heating coil detected by the temperature sensor, and drives and controls the thyristor inverter so as to keep the current temperature of the induction heating coil within the safe use temperature range. Prevents damage to the insulation coating due to overheating of the heating coil.

The induction heating coil formed according to the uneven shape of the mold fitting surface and the dielectric heat medium mounted with the induction heating coil are directly engaged with the mold fitting surface to form the product surface. Efficiently preheat the vicinity of the surface by induction heating.

In addition, the induction heating coils that are engaged with the concave-convex shape of each part of the mold fitting surface are controlled in energization time by a timer switch for each induction heating coil.

The frequency of the thyristor inverter is set appropriately according to the characteristics of the mold.

In addition, the characteristics of the mold for converting the frequency, the surface corresponding to the thin wall of the cast product has a low frequency, the thick wall part has a high frequency,
Also, set the corners, tip, etc. low at the start,
It refers to the conversion from the middle to high to prevent overheating and breakage.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view of an essential part showing an electric circuit of a mold heating apparatus of an embodiment.

In FIG. 1, 1a, 1b, and 1c are high-temperature inorganic insulating coating agents (for example, Nissan Chemical Co., Ltd.) so as not to cause insulation failure between coils even when the coil temperature rises to 600 ° C.
Manufactured by the brand name Bond X 95) and coated with a copper wire for induction heating, 2a, 2b and 2c are each a magnet switch as a timer switch (hereinafter, simply referred to as a magnet switch), and 3 is an arbitrary output frequency. Thyristor inverter, which can be set and changed, 4
Is a temperature sensor built in the induction heating coil to detect the current temperature of the induction heating coil, and 5 is a thermometer having a microcomputer.

The thermometer 5 includes an A / D converter connected to the detection output from the temperature sensor 4, and the output from the A / D converter is the current temperature of the induction heating coil and is measured every predetermined minute cycle. The data is updated and input to the temporary storage means of the microcomputer 5 (hereinafter referred to as MPU).

When a plurality of induction heating coils 1a, 1b, 1c are provided, a temperature sensor 4 and an A / D converter are provided for each induction heating coil, and conversion of the A / D converter is performed for each temperature sensor 4. The cycles are set at different intervals, the outputs from the respective A / D converters are cyclically input to the temporary storage means of the MPU, and are sequentially updated and stored in the storage area for each temperature sensor 4, and the induction heating coils 1a, 1b, When the current temperature of 1c has been updated and stored in one round, the maximum value stored in each storage area is detected and regarded as the current temperature of the induction heating coil. Based on this value, the thyristor inverter 3 The output frequency of each of the temperature sensors 4, or individually turn on / off the magnet switch based on the value stored in the storage area of each temperature sensor 4.
FF control is performed to prevent the induction heating coil from overheating.

Further, the thyristor inverter 3 is configured so that the output frequency of the induction current can be arbitrarily selected from 40 to 120 Hz, and the dielectric to be heated by the induction heating coils 1a, 1b, 1c is heated to a predetermined preheating temperature. The output frequency for heating is set in advance to perform a steady output, or the current temperature of the dielectric is sequentially detected by a temperature sensor (not shown) provided in the dielectric to be heated, and the heating target is determined. The output frequency is controlled by the MPU of the thermometer 5 in order to raise the temperature to the preheating temperature of the above. In any case, the current temperature of the induction heating coil exceeds the upper limit value of the safe use temperature range by the MPU of the thermometer 5. If it is determined that the output frequency is low, the output frequency is set to a low value or the drive power supply itself is cut off. That is, it is optional whether or not the closed loop control is performed between the dielectric to be heated and the thyristor inverter 3 by the MPU of the thermometer 5, but the closed loop between the induction heating coil and the thyristor inverter 3 is not required. The loop control is always performed, and when the closed loop control is performed between the dielectric and the thyristor inverter 3, the closed loop control between the induction heating coil and the thyristor inverter 3 is preferentially performed. In the examples, the safe use temperature range of the induction heating coil is set to 200 to 400 ° C.

Each of the induction heating coils 1a, 1b, 1c individually controls ON / OFF of each magnet switch by the MPU of the thermometer 5 based on the current temperature fed back to the thermometer 5 from the dielectric to be heated. The preheating may be performed until all of the respective dielectrics to be heated reach the set temperature, but if the set preheating temperature of the heating target and the volume of the heating target are different, the preheating time varies, Until all the heating targets reach the set temperature, it is necessary to energize the heating targets that have reached the set preheating temperature relatively early after the start of preheating to prevent cooling, and useless power is consumed.

In view of this, in this embodiment, a heating time schedule is created to match the energization end times of all induction heating coils by providing a start time difference for each induction heating coil and starting continuous energization. Using the timer switch for each induction heating coil arranged above, the timer is operated according to the heating time schedule, and all heating targets are made to reach the set temperature after a predetermined time has elapsed.

For example, according to the example of the heating time schedule shown in FIG. 2, the induction heating coil 1c is energized for T3 hours and 1a.
Will be energized for T3-T1 time, 1b for T3-T1-T2 time, and finally all heating objects will reach the set temperature when T3 time elapses. Where T3, T2
The T1 time is a value experimentally measured in advance depending on the size, shape, etc. of the heating target.

FIG. 3 (a) and FIG. 3 (b) are schematic views of the convex portion and the concave portion of the casting mold, respectively. In the figure, 6a and 6b are convex portions on the die fitting surface, and 6a 'and 6b' are concave portions on the die fitting surface. In FIG. 4, 6a "and 6b" are concave portions 6a 'and 6a' on the mold fitting surface, respectively.
An induction heating medium is mounted on an induction heating medium formed following 6b ', and the induction heating mediums 6a "and 6b" are respectively inserted into the mold recesses 6a' and 6b 'to form the recesses 6a' and 6b. ′ Is heated. Of course, the mold protrusions 8a, 6
An induction heating coil formed separately according to each shape is fitted in b and is heated. The induction heating mediums 6a "and 6b" formed according to the uneven shape of the mold fitting surface and the induction heating coil formed according to the uneven shape of the mold fitting surface are directly engaged with the mold fitting surface. In addition, since the vicinity of the mold fitting surface, which is the product surface, is directly induction-heated, the thermal efficiency is far better than that of heating the mold by a heater plate mounted on the rear surface of the mold on the holding plate side. .

In this way, while the preheating operation is performed, the temperature sensor 4 sequentially detects the current temperature of the coil copper wire and inputs it to the thermometer 5, and the MPU of the thermometer 5 sets the safe operating temperature range of the induction heating coil. A voltage control signal is output to the thyristor inverter 3 by comparing with the current temperature of the induction heating coil, and the output frequency of the thyristor inverter 3 is appropriately adjusted so that the current temperature of the induction heating coil does not exceed the safe use temperature range. The setting is changed, or the drive power supply of the thyristor inverter 3 itself is temporarily cut off, or the magnet switch is individually turned on / off by the MPU to maintain the safe operating temperature range of the induction heating coil.

The induction heating device having the above-described structure can easily and easily preheat a casting mold having a plurality of concave portions and convex portions.

That is, using the electric circuit diagram of FIG. 1 and using Fuji Electric 60A as the thyristor inverter 3, FIG. 6 (a),
(Perspective view), two slide pins 7 having the shape shown in FIG. 6 (b), (front view), and FIG. 5 (a), (perspective view), FIG.
(b), 2 heating coils for slide pins 7 (7 Amp each) for heating one deformed core 8 shown in (AA'-BB 'cross section in Fig. 5 (a)) simultaneously One trapezoidal heating coil (30 Amp) for the child 8 was attached. FIG. 8 is a perspective view showing a partially broken cross section of the structure of the induction heating coil 10 engaged with the slide pin 7 protruding from the die fitting surface.
The induction heating coil 10 is separated from the outer circumference of the small-diameter portion of the slide pin 7, and is engaged so as to surround the outer circumference of the small-diameter portion.
A temperature sensor 4 is closely attached to the inner peripheral surface of the induction heating coil 10 coated with the inorganic insulating coating agent, and the temperature of the induction heating coil 10 is controlled without being directly interfered with by the temperature of the slide pin 7. It can be detected.

The time schedule of the heating coil was set to 30 minutes for the coil of 30 Amp and 20 minutes for the coil of 7 Amp for heating. That is, first, the coil for variant core is energized to
After 30 minutes, the coil for the slide pin was energized, and after 30 minutes, the temperature of the tip of the pin and core was measured.
C., core was 345.degree. The frequency at this time is 6
The coil temperature was controlled at 0 Hz and the coil temperature was controlled at 380 ° C.

This value was sufficiently satisfactory to carry out a full-scale casting operation.

FIG. 7 (a) is a perspective view of a mold 9 having a cylindrical shape and a square hole therein, and FIG. 7 (b) is a front view thereof. Of course, it is applicable.

[Advantage of the Invention] According to the mold heating apparatus of the present invention, the temperature of the induction heating coil is directly detected by the temperature sensor, so that the temperature of the induction heating coil can be controlled without being affected by the ambient conditions such as the atmosphere. The current temperature of the induction heating coil is always maintained within the safe operating temperature range based on the detected temperature, and damage to the insulation coating etc. due to overheating of the induction heating coil is reliably prevented in advance. Therefore, it is not necessary to provide a forced cooling means for cooling the induction heating coil, a small coil can be easily manufactured, and a die heating device by induction heating can be provided at low cost.

Further, since the temperature sensor is not attached to the object to be heated but is built in the induction heating coil, the induction heating coil together with the temperature sensor can be easily attached to various molds.

In addition, the small induction heating coil formed following the uneven shape of the mold fitting surface and the dielectric heat medium equipped with the induction heating coil are directly engaged with the mold fitting surface. It is possible to preheat the mold much more efficiently than the one that heats the mold with the heater plate mounted on the rear surface of the mold.

Furthermore, it is possible to set the energization time for each induction heating coil by the timer switch for each induction heating coil.
Moreover, since the output frequency of the thyristor inverter that supplies electric power can be freely set, preheating work according to the characteristics of the mold can be easily performed.

Also, by using a timer switch for each induction heating coil, it is possible to set the energization time so that preheating of each part of the mold fitting surface is completed at the same time, so energization of the induction heating coil is always ON / OFF. Compared with the conventional method of controlling and maintaining the preset temperature for each preheating portion, the time for energizing each induction heating coil is shortened, and power consumption can be reduced.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of the mold heating device of the present invention, FIG. 2 is a time schedule showing the time for energizing each heating coil, and FIGS. 3 (a) and 3 (b) are casting metal molds, respectively. Schematic diagram of the convex and concave portions of the mold, FIG. 4 is a diagram showing the dielectric heat medium of a shape that follows the concave shape of the casting mold, and FIGS. 5 (a) and 5 (b) are all different shapes. A perspective view of the child and its AA'-BB 'sectional view,
6 (a) and 6 (b) are a perspective view and a front view of a slide pin, respectively, and FIGS. 7 (a) and 7 (b) are each cylindrical and have a square hole inside. FIG. 8 is a perspective view and a front view of the mold, and FIG. 8 is a partially cutaway perspective view of the induction heating coil. 1a, 1b, 1c ... Induction heating coil, 2a, 2b, 2c ... Magnet switch, 3 ... Thyristor inverter, 4 ... Temperature sensor, 5 ... Thermometer, 6a, 6b ... Mold projection, 6a ', 6b' ... Mold recesses, 6a ″, 6b ″ ... Dielectric heat medium.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Bibliography Sho 59-143563 (JP, U) JP 60-4558 (JP, B1) JP 62-7677 (JP, B1)

Claims (5)

[Scope of utility model registration request] 1. An induction heating coil connected to a thyristor inverter, a temperature sensor built in the induction heating coil for detecting a current temperature of the induction heating coil, the temperature sensor and the thyristor inverter. A mold heating apparatus comprising: a microcomputer for driving and controlling the thyristor inverter to keep the current temperature of the induction heating coil, which is communicated and detected by the temperature sensor, within a safe use temperature range. . 2. A shape of the induction heating coil or a dielectric heat medium which is fitted with the induction heating coil and engages with a mold is formed following the uneven shape of the mold fitting surface. The mold heating device according to claim 1. 3. A plurality of induction heating coils that engage with the uneven shape of each part of the die fitting surface are provided, and a timer switch for each induction heating coil is provided between each induction heating coil and the thyristor inverter. The die heating apparatus according to claim 2, wherein the timer switches are connected to each other and the control apparatus that controls the energization time to the induction heating coil is interposed. 4. The mold heating apparatus according to claim 1, wherein the thyristor inverter can change the frequency arbitrarily. 5. The mold heating apparatus according to claim 1, wherein the induction heating coil is coated with an inorganic insulating coating agent.