JP3109002B2 - Microwave heating equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a microwave heating apparatus, and more particularly to a so-called dielectric material such as a rod-shaped or plate-shaped rubber, plastic, wood, or the like, which is locally applied using microwaves. The present invention relates to a microwave heating device suitable for heating to a low temperature.

[Prior Art] Various types of rubber gasket rings having diameters ranging from several cm to several meters are used for connecting points of water supply pipes for water supply. A gasket ring with a diameter of 30 cm or more is continuously vulcanized by using an extruder to vulcanize the rubber molded into a linear shape and cut to a predetermined length. The adhesive is inserted into a mold heated by a heater or the like so that the both end surfaces abut each other, and the adhesive is heated and vulcanized by heat conduction from an electric heater to be connected in a ring shape.

Extrusion hoses made of plastic such as nylon or polyurethane are often used for hoses that send compressed air and have a working pressure of 10 kg / cm ² or less. A metal joint is used to connect the hose to the pneumatic equipment.However, the connection between the hose and the joint often has a structure in which the inner and outer surfaces of the hose are mechanically tightened. Expensive.
When mass-producing fixed-length hoses with fittings, make the outer diameter of the pipe 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 pipe, and heat the connection end of the hose with a heater. After softening by heating, the pipe of the joint is inserted and bonded to the hose.

As a result, a component for tightening the outer periphery of the hose becomes unnecessary and the cost is reduced.

In addition to this, it is also used for bonding and drying the spine of a book and for heating and bonding a decorative board to the wood mouth of a wooden board. Then, there is a use for heat sterilization of the whole drug solution by convection.

As shown above, there are many uses for locally heating the edge of a material in the course of processing in the industrial field.

Conventional local heating methods include a method of pressing a heated metal plate against a heating material and heating by heat conduction from the metal plate, a method of blowing heated air to the heating material, and a method of heating liquid such as water or oil. For example, a method of dipping an end portion of a heating material into a material is used.

However, so-called dielectric materials such as rubber, plastic, and wood often have low heat conductivity, and it takes time to conduct heat from the surface through which heat is transferred to the inside of the heating material, resulting in low work efficiency and low energy efficiency. In addition, the work environment is hot, which makes the workplace less workable.

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

As a method of exposing a local portion to a microwave electric field, a material to be heated 50 is inserted into a metal tube 51 as shown in FIG.
Out only the part necessary for heating out of the metal tube 51,
A method has been proposed in which the material to be heated 50 and the metal tube 51 are inserted into a microwave irradiation oven to irradiate microwaves for a predetermined time.

However, in this method, the entire material to be heated 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 slit 53 is formed on the wall surface of the waveguide 52 connected to the microwave oscillator 48 and the microwave absorber 49 so that the end of the material 50 to be heated can be inserted. Then, the heated material 50 is moved in a state where the end of the heated material 50 to be transferred on the conveyor 54 is inserted into the waveguide 52 through the slit 53, and during this movement, the heated material 50 ends. There has been proposed a method of irradiating a microwave.

[Problems to be Solved by the Invention] In the method shown in FIG. 5, the material to be heated 50 can be heated by exposing not only the end of the material to be heated 50 but also the portion to be heated from the metal tube 51. However, when the width of the material to be heated 50 is wider than a half wavelength of the microwave, the metal tube 51 can propagate the microwave like a waveguide, and the heating portion is exposed from the metal tube 51. Can not be limited to.

That is, it becomes impossible to heat only a specific portion.

On the other hand, in the method shown in FIGS.
It is possible to heat only the part inserted in the inside, but if rubber, plastic, or well-dried wood is used as the material to be heated 50, these materials have low microwave absorption, so these materials are locally Is not enough to heat it.

Therefore, in order to improve the microwave absorptivity, a method of increasing the length of the waveguide 52 and inserting a large number of materials to be heated 50 into the slits 53 of the waveguide 52 is also considered. In addition to an increase in the size of the device, the device becomes expensive and requires a large equipment area. For example, a natural rubber rod (10mm ×
20mm) Insert the end 10mm into the slit 53
As microwave heating to raise the temperature to 0 ° C, 40 natural rubber rods were sequentially inserted into the slit 53 at a pitch of 50 mm into the slit 53, and these were irradiated with microwaves. As a result, a value of about 40% was obtained as the microwave absorptivity. Was done.

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

An object of the present invention is to propose a microwave heating device capable of increasing the microwave absorptivity by minimizing the length of the irradiation furnace.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a microwave generating means for generating microwaves, a cylindrical irradiation furnace for transmitting microwaves from the microwave generating means, Transfer means for transferring the material to be heated along the axial direction of the furnace,
A slit for inserting a member to be heated is formed on a wall surface of the irradiation furnace so as to extend along a direction in which the material to be heated is transferred. Further, an axial internal conductor forming a coaxial line in the irradiation furnace is formed by extending the slit. When the thickness of the inner conductor is L and the thickness of the material to be heated is d, the thickness L of the inner conductor is (1/2) d ≦ L ≦ d A microwave heating apparatus characterized by satisfying the above condition is proposed.

When the material to be heated is sequentially transferred along the slit while a part of the material to be heated is inserted into the irradiation furnace through the slit, the microwave irradiation means irradiates the irradiation furnace with the microwave. The microwaves propagate sequentially along the wall of the irradiation furnace. At this time, the lines of electric force converged by the internal conductor pass through the material to be heated, and the material to be heated can be efficiently subjected to dielectric heating.

The thickness L of the inner conductor of the irradiation furnace is equal to the thickness d of the material to be heated.
On the other hand, since it is configured so as to satisfy the condition of (1/2) d ≦ L ≦ d, the lines of electric force generated from the internal conductor pass uniformly through the material to be heated, and the material to be heated has uneven heating. Can be suppressed.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, external conductors are provided at both ends of a cylindrical irradiation furnace 10.
A microwave oscillator 15 and a microwave absorber 16 are connected via waveguides 11 and 12 and waveguides 13 and 14, respectively.

Cylindrical insulating supports 17 and 18 are mounted in the outer conductors 11 and 12, respectively.
9, 20 are inserted. Antennas 21 and 22 are connected to one ends of the internal conductors 19 and 20, and an internal conductor 23 extending along the axial direction of the irradiation furnace 10 is connected to the other end by bolts 24.

On the other hand, a slit 25 is formed on the wall surface of the irradiation furnace 10 along the axial direction of the irradiation furnace 10, as shown in FIG.

The slit 25 is formed so that an end of a heated material 26 such as a natural rubber rod for forming a rubber gasket ring of a water supply pipe for water and a part of a belt 27 can be inserted.

The belt 27 is moved by a belt conveyor mechanism arranged along the wall surface of the irradiation furnace 10, and is made of a glass fiber that absorbs very little microwave and coated with a tetrafluoroethylene resin.

Here, when forming the inner conductor 23 having a rectangular cross section that forms a coaxial line, when the thickness of the inner conductor 27 is L and the thickness of the material 26 to be heated is d, (1/2) d ≦ It is configured to satisfy the condition of L ≦ d.

That is, the number of lines of electric force passing through the material to be heated 26 is determined by the correlation between the thickness L of the internal conductor 21 and the thickness d of the material to be heated 26. On the other hand, it is necessary to form the inner conductor 23 having the optimum thickness L.

For example, as shown in FIG. 3, when the thickness L of the inner conductor 23 is made larger than the thickness d of the material 26 to be heated,
As shown by the dotted lines, the lines of electric force from
Many objects pass through the outside of the material to be heated 26.

Since the lines of electric force passing outside the material to be heated 26 do not contribute to the heating of the material to be heated 26, the microwave absorptivity of the material to be heated 26 is reduced.

On the other hand, as shown in FIG. 4, when the thickness L of the internal conductor 23 is reduced to half or less the thickness d of the material 26 to be heated,
The lines of electric force generated from the heat are concentrated in the middle of the end surface of the material to be heated 26, and a hot spot is generated in the material to be heated 26, and a portion 28 where the lines of electric force do not pass through the material to be heated 26 is formed, and heating It was confirmed that unevenness occurred.

Therefore, in the present embodiment, the thickness L of the internal conductor 23 is formed so as to satisfy the above-described condition with respect to the thickness d of the material 26 to be heated.

In the above configuration, when microwaves are generated from the microwave oscillator 15 in the process of moving the material to be heated 26 placed on the belt 27 along the irradiation furnace 10 in accordance with the movement of the belt 27, this microwave Propagates through the irradiation furnace 10 through the waveguide 13, the antenna 12, and the internal conductors 19 and 23.

This microwave is absorbed by the end of the material to be heated 26 and attenuated in the process of propagating in the irradiation furnace 10, but the remaining microwave without being absorbed passes through the inner conductor 20, the antenna 22, and the waveguide 14. The microwave is absorbed by the microwave absorber 16.

When the material to be heated 12 is moved by the belt 27 while the microwave is being propagated into the irradiation furnace 10, the microwave is irradiated to the end of the material to be heated 26 inserted into the irradiation furnace 10 from the slit 25, and the microwave is irradiated. The heating material 26 can be locally heated. At this time, the inner conductor 23 is fixed in the irradiation furnace 10,
Since the coaxial line is formed, the irradiation furnace 10 does not have a cutoff wavelength as in the case of using a conventional rectangular waveguide, and the aperture of the irradiation furnace 10 can be reduced regardless of the wavelength of the microwave. .

In addition, in the case of such an irradiation furnace 10, since the characteristic impedance at the time of microwave propagation is lower than that of the irradiation furnace using a rectangular waveguide, good matching is achieved even with a material to be heated having a large relative dielectric constant, Microwave reflection loss can be reduced.

Further, when the microwave absorption rate was measured using the apparatus in this embodiment, the length of the irradiation furnace 10 was 65%, even if the length of the irradiation furnace using a conventional rectangular waveguide was 25%. It was confirmed that microwave absorption was obtained.

Further, when the temperature distribution at the end of the heated material 26 was measured, the ratio d / L of the thickness d of the heated material 26 to the thickness L of the internal conductor 23 was obtained.
Is between 1.0 and 0.8 ± 1.5 ° C around 150 ° C, d / L
A result was obtained in which a temperature distribution of ± 3.5 ° C. was obtained at 0.6 and a temperature distribution of ± 5 ° C. at d / L of 0.5.

And it was confirmed that the microwave absorptance did not change when d / L was between 1.0 and 0.5.

[Effects of the Invention] As described above, according to the present invention, the inner conductor is fixed in the irradiation furnace to form a coaxial line, and the number of lines of electric force passing through the material to be heated is increased. The size of the device can be reduced, and the microwave absorptivity can be increased.

In addition, since the relationship between the thickness of the internal conductor in the irradiation furnace and the thickness of the material to be heated is determined to be constant, there is no hot spot on the material to be heated, and the material to be heated can be heated uniformly. And contribute to the improvement of quality.

[Brief description of the drawings]

1 is an overall configuration diagram showing one embodiment of the present invention, FIG. 2 is a cross-sectional view of a main part of an irradiation furnace, and FIG. 3 is an explanation for explaining a relationship between an inner conductor and a thickness of a material to be heated. 4 is another explanatory view for explaining the relationship between the inner conductor and the thickness of the material to be heated, FIG. 5 is a perspective view of a main part of a conventional example, and FIG. 6 is a main part of another conventional example. FIG. 7 is a sectional view of an essential part of FIG. 10 Irradiation furnace 11, 12 Outer conductor 13, 14 Waveguide 15 Microwave oscillator 16 Microwave absorber 17, 18 Insulating support 19, 20 Inner conductor 21, 22 Antenna 23 Inner conductor 25 Slit 26 Material to be heated 27 Belt

Claims (1)

(57) [Claims] 1. A microwave generating means for generating microwaves, a cylindrical irradiation furnace for transmitting microwaves from the microwave generating means, and a transfer for transferring a material to be heated along a cylindrical axis of the irradiation furnace. Means, a slit for inserting a member to be heated extending in the direction of transport of the material to be heated is formed on a wall surface of the irradiation furnace, and further, an axial internal conductor forming a coaxial line in the irradiation furnace. Are fixed along the direction in which the slits extend, and when the thickness of the internal conductor is L and the thickness of the material to be heated is d, the thickness L of the internal conductor is
Characterized by satisfying the condition of (1/2) d ≦ L ≦ d.