JP3109003B2 - 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 to bond and dry the spine of a book and to heat and bond a decorative board to the wood opening of a wooden board. There is an application to heat sterilize 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, with the end of the heated material 50 transferred by the conveyor 54 inserted into the waveguide 52 through the slit 53,
A method has been proposed in which the heating member 50 is moved, and the end of the heated material 50 is irradiated with microwaves during the movement.

[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 the wall surface of the irradiation furnace so as to extend along the direction in which the material to be heated is transferred.Further, the slit is opposed to the slit, and along the direction in which the slit extends. When a ridge metal plate arranged in the irradiation furnace is provided, and the thickness of the ridge metal plate is L and the thickness of the material to be heated is d, the thickness L of the ridge metal plate is (1 /
2) A microwave heating device characterized by satisfying the condition of d ≦ L ≦ d 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 ridge metal plate pass through the material to be heated, and the material to be heated can be efficiently subjected to dielectric heating.

Further, since the thickness L of the ridge metal plate of the irradiation furnace satisfies the condition of (1/2) d ≦ L ≦ d with respect to the thickness d of the material to be heated, the ridge metal plate is generated from the ridge metal plate. The lines of electric force that pass through the material to be heated uniformly, thereby suppressing the occurrence of uneven heating in the material to be heated.

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.
Microwave oscillator 13 and microwave absorber via 11, 12
14 are connected.

As shown in FIG. 2, the irradiation furnace 10
A slit 15 is formed along the axial direction of the irradiation furnace.
Ridge metal plate 16 has a screw 17 facing slit 15 in 10
Screwed by.

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

The belt 19 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 ridge metal plate 16, when the thickness of the ridge metal plate 16 is L and the thickness of the material to be heated 18 is d, the condition of (1/2) d ≦ L ≦ d is satisfied. It is configured to meet.

That is, the number of lines of electric force passing through the material 18 to be heated is determined by the correlation between the thickness L of the ridge metal plate 16 and the thickness d of the material 18 to be heated. Therefore, it is necessary to form a ridge metal plate 16 having an optimum thickness L.

That is, as shown in FIG. 3, when the thickness L of the ridge metal plate 16 is made larger than the thickness d of the material 18 to be heated, the lines of electric force from the ridge metal plate 16 to the material 18 to be heated are indicated by dotted lines. As described above, many objects pass outside the material to be heated 18.

Since the lines of electric force passing outside the material to be heated 18 do not contribute to the heating of the material to be heated 18, the microwave absorptivity of the material to be heated 18 is reduced.

On the other hand, as shown in FIG.
Is reduced to half or less of the thickness d of the material 18 to be heated, the lines of electric force generated from the ridge metal plate 16 are concentrated in the middle of the end face of the material 18 to be heated, and a hot spot is generated on the material 18 to be heated. Also, it was confirmed that unevenness in heating occurred in which a portion 20 through which the lines of electric force did not pass was formed in the material 18 to be heated.

Therefore, in the present embodiment, the thickness L of the ridge metal plate 16 is formed so as to satisfy the above-described condition with respect to the thickness d of the material 18 to be heated.

In the above configuration, when microwaves are generated from the microwave oscillator 13 in the process of moving the material to be heated 18 placed on the belt 19 along the irradiation furnace 10 in accordance with the movement of the belt 19, this microwave Is the irradiation furnace through the external conductor 11
Propagating in 10.

This microwave is absorbed by the end of the material to be heated 18 and attenuated in the process of propagating in the irradiation furnace 10, but the remaining microwave without being absorbed is passed through the external conductor 12 to the microwave absorber.
Absorbed in 14.

When the material to be heated 18 is moved by the belt 19 while the microwave is being propagated into the irradiation furnace 10, the microwave is irradiated to the end of the material to be heated 18 inserted into the irradiation furnace 10 from the slit 15, and the microwave is irradiated. The heating material 18 can be locally heated. At this time, since the ridge metal plate 16 is arranged in the irradiation furnace 10, the cutoff wavelength becomes longer than that in the case of using a conventional rectangular waveguide as the irradiation furnace 10, so that the irradiation furnace
10 caliber can be reduced.

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.

In addition, when the microwave absorption was measured using the apparatus in this embodiment, the length of the irradiation furnace 10 was reduced to obtain the same microwave absorption as the irradiation furnace using the conventional rectangular waveguide. It was confirmed that only 32% was required.

Further, when the temperature distribution on the end face of the heated material 18 was measured, the ratio of the thickness d of the heated material 18 to the thickness L of the ridge metal plate 16 was determined.
When d / L is between 1.0 and 0.8, ± 1.5 ° C around 150 ° C, d / L
However, when d / L is 0.5 and d / L is 0.5 and d / L is 0.5 and d / L is 0.5, the bonding strength is not reduced even when d / L is 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 ridge metal plate is arranged in the irradiation furnace to increase the number of lines of electric force passing through the material to be heated. And the microwave absorptivity can be increased.

In addition, since 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, a hot spot does not occur in the material to be heated, and the material to be heated is uniformly heated. And can contribute to the improvement of quality.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing one embodiment of the present invention, FIG. 2 is a sectional view of a main part of an irradiation furnace, and FIG. 3 is a diagram for explaining a relationship between a ridge metal plate and a thickness of a material to be heated. FIG. 4 is another explanatory view for explaining the relationship between the thickness of the metal plate to be heated 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 another conventional example. FIG. 7 is a sectional view of a main part of FIG. 10 Irradiation furnace 11, 12 External conductor 13 Microwave oscillator 14 Microwave absorber 15 Slit 16 Ridge metal plate 18 Material to be heated 19 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 is formed on the wall surface of the irradiation furnace to extend along the direction of transfer of the material to be heated, and further, opposed to the slit, and,
When a ridge metal plate is provided in the irradiation furnace along the direction in which the slit extends, and the thickness of the ridge metal plate is L and the thickness of the material to be heated is d, the ridge metal plate Characterized in that the thickness L of the microwave heating device satisfies the condition of (1/2) d ≦ L ≦ d.