JPS60193291A - High frequency heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (/D Field of Industrial Application) The present invention relates to a high-frequency heating device, and aims to provide a novel structure for creating a uniform electric field within a heating chamber.

(B) Prior Art In general, in high-frequency heating devices, so-called microwave ovens, high-frequency power is supplied to the heating chamber by oscillating high-frequency waves from a high-frequency supply means, such as a magnetron, through a waveguide. However, with such a power supply method, it is not possible to create a uniform electric field distribution within the heating chamber, so that the object to be heated placed in the heating chamber is baked unevenly. Therefore, a microwave oven equipped with a radio stirring device such as the well-known Stara (Special Publication Publication No. 59-445)
5) and a microwave oven having a plurality of power feed ports (Japanese Utility Model Application Publication No. 5S-28198), etc., have been researched and developed.

However, the former type of microwave oven requires a radio stirring device such as a stirrer to be installed inside the heating chamber, which reduces the effective space inside the heating chamber, and the latter type of microwave oven requires multiple power supply ports to be installed. Since it is necessary to branch the waveguide, the space occupied by the waveguide increases, and the microwave oven becomes relatively large compared to the size of the heating chamber.

(c) Object of the Invention An object of the present invention is to provide a novel high-frequency heating device that has a large effective space within the heating chamber and has a uniform electric field distribution within the heating chamber.

B) Structure of the Invention The high-frequency heating device of the present invention comprises: a heating chamber; a microstrip antenna disposed in the heating chamber and having a high-frequency radiating element; It is characterized by consisting of an oscillator.

(E) Embodiment A feature of the present invention is that high frequency waves oscillated from a high frequency oscillator are supplied to the heating chamber using a microstrip antenna in which a radiating element is formed. Figure 1 A and Bd
, shows the first form of such a microstrip antenna (1), (2) is a substrate made of a dielectric material, (3 bars 3)...
・ is a rectangular high-frequency radiating element made of a conductor, (4) is a transmission line connecting the radiating element, (5) is a supply line serving as a high-frequency supply port to the radiating element (3), and these radiating elements (
3) The transmission line (4) and the supply line (5) are formed in a predetermined shape on the -main surface of the substrate (2).

(6) is a ground conductor formed on the entire other main surface of the substrate (2).

Each radiating element (3) has a shape that acts as a resonator for high frequency waves at a predetermined frequency. Therefore, the high frequency wave supplied from the supply line (5) is transmitted from each radiating element f3J to the direction shown in the figure. Emitted with good directionality in the direction of the arrow.

The present invention aims to heat an object to be heated using high frequency waves having such directivity. Figures 2 and 3 show one embodiment of the present invention. 11G is a heating chamber, and a microstrip antenna (1) is arranged near the center of the top surface of the heating chamber so that its ground conductor (6) faces the top surface.

U is a waveguide, (1z is a trapezoidal ridge made of a conductor placed inside the waveguide. The microstrip antenna (1) is clamped and fixed by the waveguide 1υ and the ridge α2Vc, Therefore, the ground conductor (6) is connected to the waveguide aυ,
Further, the supply lines (5) are electrically connected to the ridge sauce, respectively. (13 is a magnetron containing a high frequency generator that supplies high frequency waves to the waveguide Uυ, (14 is an electrical equipment room where a shark magnetron and its drive circuit (not shown), etc. are arranged.

Therefore, the magnetron (2 generated by 131c)
The high frequency of 450MHz is transmitted via the waveguide aυ to the supply line (
5) and is further supplied to a radiating element (3).

Then, the radiation element (3) radiates high frequency waves into the heating chamber [1ff], thereby heating the object placed in the head of the heating chamber. Note that the ridge a2 provides good impedance matching between the microstrip antenna (1) and the waveguide LD.

A specific example of the microstrip antenna (1) will be described below with reference to FIG. The substrate (2) has a thickness h=
1.58n, width W o = 56.0”s dielectric constant ξ
Teflon plate with r=2.5. The grounding conductor (6) is a copper film laminated over the entire back side of the substrate (2), and the radiating element (3), transmission line (4) and supply line (5) are connected to the substrate (2).
2) is formed by etching away the copper film laminated on the surface side.

First, the radiating element (3) will be explained. Such a rectangular radiating element (3) VC Twitter, IEEE TRANS
ACTIONS ON ANTENNA AND PR
OPAGATIONNOVoL, AP-30NQ2 M
ARCH, 1982! In this case, the ideal width W of the radiating element (3) is as follows. Here, λ0 is the high frequency wavelength supplied to the radiating element (3), which is 12.2 m in this example. Therefore, the width W is 46.2ff. Further, when the length L of the radiating element (3) is, it becomes a resonator for the frequency f and radiates a high frequency. However, C travels at the speed of light. Therefore, the length L in this example is 38°04
ff.

By the way, the present invention is a microstrip antenna (1)
The temperature of the substrate (2) increases and its dielectric constant decreases. Therefore, in this example, the shape of the radiating element (3) is changed to a width W=5 in consideration of such a decrease in dielectric constant.
By setting the length L=37.95g-, resonance for the frequency of 2450MHz is obtained.

The transmission line (4) propagates high frequencies without causing reflection of high frequencies between each radiating element (3),
It is necessary to make the length 1/ of the high frequency wavelength. here,
When propagating through the microstrip antenna (1), the wavelength λS of the high frequency becomes λ0/u1, and considering the decrease in the dielectric constant ξr as described above, in this embodiment, the transmission line (4
) has a length of 40.9 cod and a width of 5.1 silk.

The supply line (5) receives the high frequency wave oscillated by the magnetron 03 via the waveguide αυ and the ridge (121),
Radiating element (3) is for propagating VC. (Figure 3)
If the supply line (5) is too wide, the radiating element (3)
If it is narrow, the propagation efficiency of high frequency waves will deteriorate, and there is a risk that electric lines of force will leak from the supply line (5) to the outside, causing sparks and causing the supply line (5) to melt. be.

According to the inventors, it has been experimentally determined that the radio wave radiation efficiency of the radiating element (3) will not deteriorate if the width W of the supply line (5) is 1/2 or less of the width W of the radiating element [3J]. It has been found that Furthermore, if the width W is 12fi or more, no spark will be generated by the high frequency supply of 400W. Therefore, in this embodiment, the width W of the supply line is 15tI. Further, when the length l of the supply line (5) is in the range of 0°7λy to 1.2λ2, the high frequency radiation efficiency of the radiating element (3) is good.

Note that A2 is the wavelength of the high frequency within the substrate (2).

FIG. 5 shows the heating characteristics of the heating device of this embodiment and the conventional electronic heater. Such heating characteristics show the change in water temperature with respect to heating time when 200 ml of water is put in a pot.The solid lines a and b are for this example, and the bee force is at the midpoint of aFi 2nd 2nd middle B. , bVi in the same figure, avc
This shows the case where a beaker is placed. Moreover, the broken line is that of a conventional microwave oven. As is clear from this figure, the heating device of this embodiment can perform heating with almost the same efficiency as that of a conventional microwave oven. A microstrip antenna 12G' having the form shown in FIG. Such a microstrip antenna ■ has a substrate c2 made of a dielectric material.
υ consists of a substantially square base C21&) and a protrusion (21b) protruding from the base. Radiating element (2 122+・
... is formed on the surface of the base (21L) in a state connected to the transmission line (C), and the supply line (24I) is formed on the surface of the base (21L), and the supply line (24I is connected to the protrusion (21L)).
b) is formed on the surface.

Such a microstrip antenna! 20) and the base (
21a) High frequency waves are concentratedly radiated to the position relative to the IC, and concentrated heating can be performed. In this way, there is no restriction on the shape of the microstrip antenna, and it can be freely determined. (fart)
Effects of the Invention The present invention is configured as shown in I) in which a microstrip antenna is disposed within a heating chamber and high frequency waves are radiated from the antenna, and a radio wave agitation device such as a stun as in the prior art is removed. This makes it possible to widen the effective space within the heating chamber and eliminate uneven heating.

[Brief explanation of the drawing]

The figures show embodiments of the invention, and FIGS. 1A, B and ff14
[A top view and a sectional view showing the first form of the Ni BH microstrip antenna, FIG. 2 A%B is a side sectional view and a top sectional view showing the high frequency heating device, and FIG.
FIG. 5 is a characteristic diagram showing heating characteristics, and FIG. 6 is a top view showing a second form of the microstrip antenna. (1)(4)...Microstrip antenna, (2
)Qυ...Substrate, (3) (support)...Radiating element, +4
3 (23+...transmission line, (5)(2)...supply line,
II (1...Heating chamber, l]3...Magnetron. Applicant Sanyo Electric Co., Ltd. Patent attorney Shizuo Sano Figure 2 Figure 3

Claims (1)

[Claims] (1) A high-frequency heating device comprising a heating chamber, a microstrip antenna disposed in the heating chamber and having a high-frequency radiating element, and a high-frequency oscillator that supplies high-frequency waves into the heating chamber from the radiating element of the antenna. .