JPS637433B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microwave heating device, and particularly to a device for heating an object to be heated, such as paper, which has a large surface area relative to its volume.

2. Description of the Related Art It has been well known to use microwaves to heat objects. However, with conventional equipment, in order to heat a material such as paper that has a large surface area relative to its volume, the electric field strength of the microwave must be increased more than necessary, resulting in extremely poor heating efficiency and Ta.

In addition, in order to increase this efficiency, a method has been devised in which a ladder circuit is formed on the center conductor of a microstrip line, and the object to be heated is scanned over the surface of the ladder circuit to heat the object (for example, in Japanese Patent Application No. 1983). ―
108644). However, this method has disadvantages in that uneven heating tends to occur, and since a ladder circuit must be formed on the center conductor, production costs are high.

The present invention has been made in view of these conventional difficulties, and one implementation thereof will be described below with reference to the drawings.

In FIG. 1, 1 is a rectangular substrate made of alumina ceramic or the like having a relatively high dielectric constant;
Striped dipole antennas 2a and 2b are formed symmetrically with the substrate 1 in between on the front and back sides near one of the short sides. 3a is a feeder that connects the dipole antenna 2a on the front side and the center conductor 5 of the coaxial line 4 for introducing microwaves, and a matching stub 6a is formed at an appropriate position.
3b is a feeder that connects the dipole antenna 2b on the back side and the outer conductor 7 of the coaxial line 4. 2c and 2d are the dipole antennas 2
It is connected to the microwave deriving coaxial line 8 by another dipole antenna provided on the side where a and 2b are formed and the opposite side. In the figure, the dipole antennas 2a and 2c on the front side are connected to the center conductors 5 and 9 of the coaxial lines 4 and 8, respectively, and the dipole antennas 2b and 2d on the back side are connected to the outer conductors 7 and 10, respectively. However, it is not necessary to configure it this way. The front and back sides of one of the dipole antennas (for example, 2c and 2d) may be switched, or the direction thereof may be changed. 11
is a dummy load attached to the rear of the coaxial line 8 for leading out microwaves, and is used to absorb and consume microwaves that have not been completely consumed by the dielectric substrate 1. Reference numeral 12 denotes a material to be heated, such as paper, which is scanned over the dielectric substrate 1 in the direction of the chain arrow. Note that the heated substance 12 may be scanned not only on the front surface of the dielectric substrate 1 but also on the back surface.

Since the present invention is constructed as described above, when microwaves are supplied in the direction of the solid arrow, magnetic fields and electric fields as shown in FIGS. 2A and 2B are generated in the dielectric substrate 1. FIG. 2A shows the mode of the magnetic field, and B shows the mode of the electric field. In this mode, there is no vertical electric field on the wide surface of the dielectric substrate 1, so-called
LSE mode (longitudinal-section electric
mode). Therefore, all electric fields on the wide surface of the dielectric substrate 1 are parallel to this surface. Originally, when radio waves propagate through a dielectric, a leakage electric field occurs, unlike when they propagate inside a metal waveguide. Also, the direction of this leakage electric field is the same as the original mode,
It is parallel to the wide surface of the dielectric substrate 1.

Therefore, when a sheet-shaped object to be heated 12 such as paper, cloth, or film is brought close to or in contact with the front or back surface of the dielectric substrate 1, all of the leakage electric field is applied to the object to be heated, allowing efficient heating. .

Also, unlike using a ladder circuit etc., the dipole antennas 2c, 2 on the microwave extraction side
d, feeders 3c, 3d, stub 6b, and dummy load 11 are appropriately selected and matched.
Since the radio waves in the dielectric substrate 1 are completely traveling waves, uneven heating does not occur. Furthermore, although the ladder circuit can heat only the front surface, the one of the present invention can heat both the front and back surfaces of the dielectric substrate 1.

Furthermore, since the structure is extremely simple, production costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of essential parts showing one embodiment of the present invention;
FIG. 2A is a schematic diagram showing the magnetic field mode in the dielectric substrate, and FIG. 2B is a schematic diagram showing the electric field mode. 1... Dielectric substrate, 2a, 2b, 2c, 2d... Dipole antenna, 3a, 3b, 3c, 3d... Feeder, 4, 8... Coaxial line, 5, 9... Center conductor,
6a, 6b...Stub, 7, 10...Outer conductor, 12
...Object to be heated.

Claims (1)

[Claims] 1. A pair of striped dipole antennas are formed on the front and back sides near a pair of opposite sides of the dielectric substrate, and one of the pair of dipole antennas is connected to the center conductor of the coaxial line, and the other is connected to the center conductor of the coaxial line. Connected to an external conductor, the object to be heated is brought close to or in contact between the opposing dipoles of the dielectric substrate, and the object to be heated is heated by microwaves introduced from one of the coaxial lines. A microwave heating device characterized by: 2. The microwave heating device according to claim 1, wherein a matching stub is provided on the feeder that connects the center conductor of the coaxial line and the dipole antenna.