JPH04141981A - Microwave heating device - Google Patents

Abstract

PURPOSE:To make a device compact, and improve the microwave absorbing ratio by disposing a ridge metal plate in a radiation furnace, and increasing the number of electric force lines passing through a subject material. CONSTITUTION:A subject part inserting slit is formed in a wall surface of an irradiation furnace 10 to be extended along the transfer direction of a subject material 18, and a ridge metal plate 16 is disposed in the direction of the slit in the irradiation furnace 10 facing the slit. When microwaves are radiated from a microwave generating means 13 into the irradiation furnace 10, the microwaves are transmitted in order along the wall surface of the irradiation furnace 10, and electric force lines converged by the ridge metal plate 16 pass through the subject material 18 for induction heating the subject material 18 effectively. The length of the irradiation furnace 10 can thus be restricted to the minimum, and the microwave absorbing ratio can be increased.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a microwave heating device, and in particular to a microwave heating device that locally heats so-called dielectric materials such as rod-shaped or plate-shaped rubber, plastic, and wood using microwaves. The present invention relates to a microwave heating device suitable for heating.

[Prior Art J] There are many types of rubber gasket rings used at the connection points of water supply pipes, ranging in diameter from several meters to several meters. Gasket rings with a diameter of 30 cm or more are made by continuously vulcanizing rubber formed into a linear shape using an extruder, cutting it into a predetermined length, applying vulcanizable rubber adhesive to the cut surfaces of both ends, and applying electricity. The adhesive is inserted into a mold heated with a heater, etc., with both ends pressed against each other, and the adhesive is heated and vulcanized by heat conduction from the electric heater to form a ring-shaped connection.

For hoses that send compressed air and whose working pressure is less than 1,000 kg/cm', extruded plastic hoses such as nylon or polyurethane are often used. Metal fittings are used to connect these hoses to pneumatic equipment, but most of the connections between hoses and fittings have a structure in which the inner and outer surfaces of the hose are mechanically tightened, making the structure of the fittings complicated. It's expensive.

When mass producing fixed-length hoses with fittings, make the outer diameter of the vibrator inserted into the hose on the fitting side slightly larger than the inner diameter of the hose, apply adhesive to the outer circumference of the vibrator, and attach the connecting end of the hose to a heater. After heating it to soften it, the vibrator of the joint is inserted into the hose and glued.

As a result, parts that tighten the outer circumference of the hose are not required, resulting in lower costs.

In addition, applications include drying the adhesive on the spines of books, heating and adhering decorative boards to the ends of wooden boards, and patent application No.
As shown in this issue, the lower part of an ampoule containing a medicinal solution is heated with microwaves to sterilize the entire medicinal solution by heating by convection.

As shown in the examples above, there are many applications in which the edges of a material are locally heated during processing in the industrial field.

Conventional local heating methods include pressing a heated metal plate against the heating material and heating it by heat conduction from the metal plate, blowing heated air onto the heating material, and heating liquid such as water or oil. A method such as dipping the end of the heated material is used.

However, many so-called dielectric materials such as rubber, plastic, and wood have low thermal conductivity, and it takes time for heat to be conducted from the surface to the inside of the heating material, resulting in low work efficiency and energy efficiency. . Furthermore, the working environment is hot, resulting in a workplace with fewer workers.

Therefore, it became necessary to heat the material in a short time without relying on heat conduction by applying the principle of microwave dielectric heat generation and exposing only the edges of the material locally to the microwave electric field. .

As a method of exposing a local area to a microwave electric field, by utilizing the fact that metal reflects microwaves, as shown in FIG. A method has been proposed in which only the portion necessary for heating is taken out of the metal tube 5I, the material to be heated 50 and the metal tube 51 are inserted into a microwave irradiation oven, and the microwave is irradiated for a predetermined period of time.

However, in this method, the entire heated material 50 must be inserted into the oven, and a large oven is required, which is not practical.

On the other hand, as shown in FIGS. 6 and 7, a waveguide 52 connected to a microwave oscillator 48 and a microwave absorber 49
A slit 53 into which the end of the heated material 50 can be inserted into the wall surface of the
A heated material 50 is formed and transported by a conveyor 54.
A method has been proposed in which the heated material 50 is moved with its end inserted into the waveguide 52 through the slit 53, and the end of the heated material 50 is irradiated with microwaves during this movement. .

``Problems to be Solved by the Invention'' In the method shown in FIG.
However, when the width of the heated material 50 becomes wider than 1/2 wavelength of the microwave, the metal tube S1 becomes able to propagate the microwave like a waveguide, and the heated part becomes The metal tube 51 can no longer be limited to the exposed portion.

In other words, it becomes impossible to heat only a specific part.

On the other hand, in the method shown in FIGS. 6 and 7, the slit 53
Although it is possible to heat only the part inserted inside, if rubber, plastic, well-dried wood, etc. are used as the heated material 50, these materials have low microwave absorption, so these materials can be heated only locally. Not enough to heat it properly.

Therefore, in order to improve the microwave absorption rate, a method of increasing the length of the waveguide 52 and inserting a large number of heated materials 50 into the slits 53 of the waveguide 52 can be considered, but this method The equipment becomes larger and more expensive, and requires a large facility area. For example, a natural rubber rod (
10mm x 20mm) with a slit 5
For microwave heating, 40 natural rubber rods were inserted into the slit 53 at a pitch of 50 mm and irradiated with microwaves to increase the temperature from room temperature to 150°C. A value of approximately 40% was obtained.

In this case, the length of the waveguide 52 is required to be 2 m or more, but if the microwave absorption rate is about 40%, the equipment area is no different from that using an electric heater.
It becomes difficult to miniaturize the device.

An object of the present invention is to propose a microwave heating device that can minimize the length of the irradiation furnace and increase the microwave absorption rate.

"Means for Solving the Problems" In order to achieve the above object, the present invention includes a microwave generation means for generating microwaves, a cylindrical irradiation furnace for propagating the microwaves from the microwave generation means, and a cylindrical irradiation furnace for propagating the microwaves from the microwave generation means. a transfer means for transferring the material to be heated along the axial direction of the furnace; a slit for inserting the material to be heated extending along the direction of transfer of the material to be heated is formed on the wall surface of the irradiation furnace; We propose a microwave heating device in which ridge metal plates are placed in an irradiation furnace facing each other along the direction in which slits extend.

Further, when the thickness of the ridge metal plate is L and the thickness of the heated material is d, the ridge metal plate is (1/2) d:i;
We propose a microwave heating device configured to satisfy the conditions of LSd.

"Operation" When a part of the material to be heated is inserted into the irradiation furnace through the slit and the material to be heated is sequentially transferred along the slit, microwaves are irradiated into the irradiation furnace from the microwave generating means. Then, the microwaves propagate sequentially along the wall surface of the irradiation furnace.

At this time, the electric lines of force focused by the ridge metal plate pass through the material to be heated, and the material to be heated can be dielectrically heated efficiently.

Also, when the thickness of the ridge metal plate of the irradiation furnace is L, and the thickness of the heated material is d, the ridge metal plate is (1/2)
If the configuration satisfies the condition of d≦LSd, the lines of electric force generated from the ridge metal plate will uniformly pass through the material to be heated,
It is possible to suppress uneven heating of the heated material.

"Example" An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, a microwave oscillator 13 and a microwave absorber 14 are connected to both ends of a cylindrical irradiation furnace 10 via external conductors 11 and 12.

On the wall of the irradiation furnace 10, as shown in FIG.
A slit 15 is formed along the axial direction of O, and a ridge metal plate 1 is provided in the irradiation furnace 10 facing the slit 15.
6 is screwed by a screw 17.

The slit 15 is formed so that the end of a heated material 18 such as a natural rubber rod for making a rubber gasket ring for a water supply pipe and the end of a belt 19 can be inserted therein.

Belt 19. is moved by a belt conveyor mechanism placed along the wall of the irradiation furnace IO.
Glass fibers with extremely low microwave absorption coated with tetrafluoroethylene resin are used.

Here, when forming the ridge metal plate 16, the thickness of the ridge metal plate 16 is L, and the thickness of the heated material 18 is d.
The configuration is such that the condition (1/2)d≦L≦d is satisfied.

That is, the number of electric lines of force passing through the heated material 18 is determined by the mutual relationship between the thickness of the ridge metal plate 16 and the thickness d of the heated material 18. It is necessary to form the ridge metal plate 16 with an optimal wall thickness.

That is, as shown in FIG. 3, when the thickness of the ridge metal plate 16 is made larger than the thickness d of the heated material 18, the lines of electric force from the ridge metal plate 16 toward the heated material 18 are shown by dotted lines. As such, more of the heat passes through the outside of the heated material 18.

Since the electric lines of force passing outside the heated material 18 do not contribute to the heating of the heated material 18, the microwave absorption rate of the heated material 18 decreases.

On the other hand, as shown in FIG. 4, when the thickness of the ridge metal plate 16 is set to 1/2 or less of the thickness d of the material to be heated 18, the lines of electric force generated from the ridge metal plate 16 are applied to the material to be heated. It was confirmed that hot spots were generated in the heated material 18, concentrated in the middle of the end face of the heated material 18, and areas 20 where electric lines of force did not pass were formed in the heated material 18, resulting in uneven heating.

Therefore, in this embodiment, the thickness of the ridge metal plate 16 was formed so as to satisfy the above-mentioned conditions relative to the thickness d of the material to be heated 18.

In the above configuration, when the microwave oscillator 13 generates microwaves in the process of moving the heated material 18 placed on the belt 19 along the irradiation furnace 10 in accordance with the movement of the belt 19, the microwaves propagates inside the irradiation furnace 10 via the outer conductor 11.

During the process of propagating within the irradiation furnace 10, this microwave is absorbed by the end of the heated material 18 and attenuated, but the remaining microwaves are transmitted to the microwave absorber 14 via the external conductor 12. Absorbed.

When the heated material 18 is moved by the belt 19 while microwaves are being propagated into the irradiation furnace 10, the slit 1
Microwaves are irradiated onto the end portion of the material to be heated 18 inserted into the irradiation furnace 10 from the irradiation furnace 10, and the material to be heated 18 can be locally heated. At this time, since the ridge metal plate 16 is placed inside the irradiation furnace 10, the cutoff wavelength is longer than when a conventional rectangular waveguide is used as the irradiation furnace 10. The diameter can be made smaller.

In addition, in the case of such an irradiation furnace, the characteristic impedance during microwave propagation is lower than that in an irradiation furnace using a rectangular waveguide, so even materials to be heated with a large dielectric constant can have good consistency. , the reflection loss of microwaves can be reduced.

Furthermore, when the microwave absorption rate was measured using the apparatus in this example, it was found that the length of the irradiation furnace 10 was longer than that of the conventional irradiation furnace in order to obtain the same microwave absorption rate as that of a conventional irradiation furnace using a rectangular waveguide. It was confirmed that the reduction was only 32%.

Furthermore, when the temperature distribution on the end face of the heated material 18 was measured, the ratio d/L of the wall thickness d of the heated material 18 to the wall thickness of the ridge metal plate 16 was between 1.0 and 0.8 (7). Then, it is 11.5℃ centering on 150℃, ±3.5℃ when d/L is 0.6,
When d/L was 0.5, the adhesive strength did not decrease even when d/L was 0°5, which had the largest temperature unevenness in a temperature distribution of ±5°C.

It was confirmed that the microwave absorption rate did not change when d/L was between 1.0 and 0.5.

"Effects of Invention 9" As explained above, according to the present invention, the ridge metal plate is arranged in the irradiation furnace to increase the number of electric lines of force passing through the material to be heated, thereby reducing the size of the device. can be achieved, and the microwave absorption rate can be increased.

In addition, because the relationship between the thickness of the ridge metal plate in the irradiation furnace and the thickness of the material to be heated is fixed, hot spots do not occur on the material to be heated, and the material to be heated can be heated uniformly. This can contribute to improving quality.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram showing one embodiment of the present invention, Fig. 2 is a sectional view of the main part of the irradiation furnace, and Fig. 3 is a diagram for explaining the relationship between the ridge metal plate and the thickness of the material to be heated. FIG. 4 is another explanatory diagram for explaining the relationship between the ridge metal plate and the thickness of the material to be heated. FIG. 5 is a perspective view of the main part of the conventional example. FIG. 7 is a perspective view of the main parts of the conventional example, and FIG. 7 is a sectional view of the main parts of FIG. Absorber 15...Slit 16...Ridge metal plate 18...Heated material 19...Belt

Claims (2)

[Claims] (1) A microwave generation means for generating microwaves, a cylindrical irradiation furnace for propagating the microwaves from the microwave generation means, and a transfer means for transporting the material to be heated along the axial direction of the irradiation furnace. A slit for inserting a heated member is formed in the wall surface of the irradiation furnace and extends along the transfer direction of the heated member, and a ridge metal plate is placed in the irradiation furnace opposite to the slit in the direction in which the slit extends. A microwave heating device arranged along the (2) A claim in which the ridge metal plate is configured to satisfy the condition (1/2) d≦L≦d, where the thickness of the ridge metal plate is L and the thickness of the heated material is d. The microwave heating device according to item (1).