JPS6241390B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microwave heating device, and in particular has a configuration that intensively heats a predetermined portion of an object to be heated, thereby suppressing wastage of microwave power. This invention relates to a high-frequency heating device designed to save energy.

Conventionally, this type of microwave heating device has a first
The structure illustrated in the figure is known. 1st
As shown in the figure, 1 is a microwave generator, 2 is a microwave generator that selects a wavelength below a set cutoff wavelength from among the microwaves generated from the microwave generator 1;
A rectangular waveguide with the cross section (a x b) shown in the figure,
A notch groove 6 in the shape of a right-angled isosceles triangle is formed on the tip opening surface, and the notch groove 6 has a right-angled apex having a length a on the E plane of the tip opening surface of the waveguide 2. A recess 7 located at the center is formed. Reference numeral 8 denotes a holding stand that supports the wooden cabinet component 3 of the object to be heated 5 having a generally rectangular parallelepiped shape. The thermosetting adhesive 4 is located within the recess 7 of the waveguide 2 and as close as possible to the center position of the length a on the E plane of the tip opening surface of the waveguide 2. They are positioned so that they face each other. In the microwave heating device having such a configuration, microwaves generated by the microwave generator 1 are radiated from the waveguide 2. As shown in FIG. 2, the electric field distribution inside the waveguide 2 becomes zero on the side of length b in the cross section (a x b) of the tip opening surface of the waveguide 2, and the electric field distribution on the E plane becomes zero. On the side of a, there is a trigonometric distribution that gradually increases toward the center as shown by the arrow, and the length a
The center line position on the edge of has the strongest electric field strength. On the other hand, the thermosetting adhesive 4, which is the heating target part of the object to be heated 5, is held at the center line position of the length a on the E plane of the tip opening surface of the waveguide 2 by the holding table 8 as much as possible. Because they are placed in close proximity to each other, they can be inductively heated in the strongest electric field.

However, the electric field strength A at the tip opening surface of the waveguide 2
As shown in the characteristic curve diagram of Fig. 3, the waveguide 2
The relationship is such that as the length a on the E plane of is decreased, the relationship increases. In addition, the tip opening surface of the waveguide 2 is
It is determined by the frequency of the microwave generated from the microwave generator 1, and once the frequency of the microwave to be used is set, the size of the waveguide 2 is also determined based on this, and the tip opening of the waveguide 2 is determined based on this. The electric field strength in the plane is also determined. For this reason,
As mentioned above, in this type of conventional device, it is possible to efficiently heat the object 5 by configuring the tip opening surface of the waveguide 2 in the shape of the recess 7; There was a drawback that it was impossible to further strengthen the electric field strength at the aperture at the tip of the wave tube 2.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional waveguide.The width of the opening at the tip of the waveguide is narrowed, and a recess is formed in the opening at the tip, so that the object to be heated can be heated. The predetermined portion is configured to face a recess formed at the tip opening surface of the waveguide, so that the electric field strength at the tip opening surface of the waveguide can be increased and the object to be heated can be effectively heated. The object of the present invention is to provide a microwave heating device that has the following characteristics.

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

Parts equivalent to those shown in FIGS. 1 and 2 are indicated by the same reference numerals. In FIGS. 4 and 5, 2 is below the set cutoff wavelength of the microwave generated from the microwave generator 1. A rectangular waveguide with a cross section (a x b) that selects the wavelength of
Its tip opening surface is a notch groove 6 in the shape of a right-angled isosceles triangle.
is formed, and this notch groove 6 constitutes a recess 7 whose apex having a right angle is located at the center of the length a on the E plane of the tip opening surface of the waveguide 2. The length a ₁ on the E plane of the tip opening surface of the waveguide 2 at the top of the right isosceles triangle of the recess 7 is formed so that a≧a ₁ , and The length a ₂ on the E plane of the tip opening surface of the waveguide 2 at the bottom of the waveguide 2 is formed so that a ₁ >a ₂ . The holding stand 8 is a wooden cabinet component 3 of the object to be heated 5.
The thermosetting adhesive 4, which is the part to be heated and which is interposed between adjacent ridge lines of the wooden cabinet components 3, is applied within the concave part 7 of the waveguide 2 and It is positioned as close as possible to the center position of the length A ₂ on the E plane of the tip opening surface of the wave tube 2 so as to face it.

Next, the operation of the microwave heating device of the present invention described above will be explained. In the device of this embodiment, the frequency of the microwave generated by the microwave generator 1 is 2450MHz, and the size of the rectangular waveguide 2 is such that the E plane is
The so-called WRJ-2 is used, with an H-plane of 109.22 and 54.61. Now, the microwave generator 1 generates
For a microwave with a microwave power of 500 W in TE ₁₀ mode, if the wavelength of the microwave is λ and the length on the E plane of the waveguide 2 is a, The microwave propagates in the waveguide 2 shown in FIG. 3 with a wavelength λg shown by the equation, and when the relationship λ/2>a is reached, the microwave propagation stops.

The electric field strength within the waveguide 2 of the present invention has an electric field strength defined by the dimensions of the waveguide 2 up to a position of length a on the E plane of the waveguide 2; Since the E plane of the end opening surface of the waveguide 2 has a shape that is gradually narrowed toward the opening end, as shown in the characteristic curve diagram of FIG.
The electric field strength increases as the length a on the E plane of . As shown in FIG. 3A, when the inside of the waveguide 2 is air and the dielectric constant ε _r 〓1,
The electric field strength is maximum at the position of length a ₁ on the E plane of the tip opening surface of the waveguide 2, and from this point the electric field strength is the same as above.
Equation (1) prevents microwaves from propagating.

However, in the configuration according to the present invention, the object to be heated 5 is arranged as close as possible within the recess 7 formed by the right isosceles triangular notch groove 6 formed in the opening surface of the tip end of the waveguide 2. It is set up. Here, generally the third
As shown in Figure B, the dielectric constant ε _r = 2.5 inside the waveguide 2.
If a dielectric material of 1 is inserted, the wavelength inside this dielectric material is λg/√ _r . Therefore, microwaves are not propagated to the tip of the waveguide 2 from the position of length a ₁ on the E plane of the tip opening surface of the waveguide 2, but as described above, when the heated object 5 is connected to the waveguide By inserting the waveguide 2 into the recess 7 formed on the tip opening surface of the waveguide 2, the waveguide 2 is inserted into the recess 7 formed on the tip opening surface of the waveguide 2 at a position where the length a 2 is smaller than the length a ₁ on the E plane of the tip opening surface of the waveguide ₂ , that is, a ₁ > a. Microwaves also come to be propagated inside the waveguide 2 at position ₂ .

With the above-described configuration, the thermosetting adhesive 4, which is the heating target part of the object to be heated 5, can be heated in an electric field stronger than the electric field strength inside the WRJ-2 waveguide 2.
The waveguide 2 can be efficiently heated on the center line of the E plane of the open end surface. On the other hand, the electric field received by the wooden cabinet components 3, which causes microwave power to be wasted, is relatively weak due to the trigonometric electric field distribution, and furthermore, since the area to which it is received is small, The microwave power wasted by the cabinet components 3 can be reduced as much as possible, thereby effectively suppressing the temperature rise of the wooden cabinet components 3, and also allowing the thermosetting adhesive 4 to be applied quickly and efficiently. Can be cured well.

In the above embodiment, the notched groove 6 is shaped like a right-angled isosceles triangle, but it is not limited to this and can have any other shape. It is clear that it can be formed into any suitable shape. In addition, the object to be heated 5 may have a generally convex shape other than a rectangular parallelepiped shape, and it goes without saying that the heated object 5 can also be applied to products made of dielectric materials such as synthetic resins, rather than wooden products. In addition, the dielectric heating of a predetermined portion of the object to be heated 5 to be heated need not be performed over the entire portion, but may be performed only partially as long as the dielectric heating has enough strength to withstand the next process operation.

As described in detail above, according to the present invention, a predetermined part of the object to be heated is heated intensively, and the electric field strength at the tip opening of the waveguide is significantly increased. Because of this, waste of microwave power can be suppressed as much as possible, the power saving effect can be greatly exhibited, and the working process time can be significantly shortened. moreover,
If the predetermined portion of the object to be heated is a thermosetting adhesive or the like that is used to bond parts by curing by heating, the thermal deformation of the parts during bonding can be reduced, reducing residual stress after bonding. In addition to being able to prevent a decrease in the strength of the finished product, it also has exceptional effects such as being able to perform a desirable adhesive process without deforming the design.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram of a conventional microwave heating device, Figure 2 is a diagram showing the waveguide of the device shown in Figure 1 and the electric field distribution at its tip opening, and Figure 3 is a diagram showing the waveguide of the device shown in Figure 1. A characteristic curve diagram showing the relationship between shape and electric field strength, FIG. 4 is a schematic configuration diagram of a microwave heating device that is an embodiment of the present invention, and FIG. 5 is a waveguide of the device shown in FIG. It is a figure which shows the front-end opening surface. 1...Microwave generator, 2...Waveguide, 3...
... Wooden cabinet component, 4 ... Thermosetting adhesive, 5 ... Heated object, 6 ... Notch groove, 7 ... Recess, 8 ... Holding stand.

Claims (1)

[Claims] 1. In a microwave heating device that generates microwaves that propagate in a waveguide and heats a predetermined part of a heated object with the microwaves, the width of the opening at the tip of the waveguide is In addition to narrowing the waveguide, a notched recess is formed in the opening surface of the tip end, and a predetermined portion of the object to be heated faces the recess formed in the opening surface of the tip end of the waveguide. heating device. 2. The microwave heating device according to claim 1, wherein the cutout recess formed at the tip opening surface of the waveguide has a cutout shape of a right isosceles triangle.