JPS5949191A - 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 Field of the Invention The present invention relates to a door device for a high frequency heating device.

Conventional Structure and Problems Conventionally, a see-through window has been provided in the door of a high-frequency heating device such as a microwave oven so that the cooking progress of food inside the heating chamber can be visually confirmed during cooking.

In order to prevent radio waves from leaking through the see-through window, a metal plate with many small holes is used to prevent food particles from getting stuck in the holes in the metal plate. A glass plate cover is provided for this purpose. Normally, this glass cover is held by a groove formed by a punching plate, the inner wall of the door, and another metal fitting, but as is well known, glass has a lower dielectric constant than air. Therefore, the effective depth D' of the groove for radio waves when the glass is inside is n = DJ7. However, D - the depth of the groove when the glass is not attached ε - the dielectric constant of the glass, and the glass is It will be much deeper than without it.

Therefore, the actual dimension from the end of the groove to the entrance becomes close to the dimension of λ/4, which increases the electric field strength at the entrance of the groove, resulting in the occurrence of sparks and abnormal temperatures in one part of the groove. Second elevation, etc. is less likely to occur. Of course, these abnormal phenomena are also greatly influenced by the electric field distribution pattern within the heating chamber, and therefore -C is generated at locations where the high electric field position due to the electric field distribution pattern matches the depth of the groove as described above.

To solve this problem, the groove dimensions must be made as shallow as possible, but in the conventional structure shown in Figure 1, the head of the screw S does not appear on the inside surface of the door 3.
In order to do this, it is necessary to spot weld the door inner wall 9 and the separate metal fitting 13 within the groove 20, so it cannot be made shallower than a certain level.

Purpose of the Invention Therefore, it is an object of the present invention to solve the above-mentioned conventional drawbacks and to provide a high-frequency heating device with stable quality and reliability that does not cause abnormal heat generation or sparks in the groove portion of the glass holder. In order to achieve the second object of the invention, the present invention comprises a heating chamber, a high-frequency oscillator that supplies high-frequency waves to the heating chamber, and a door that can freely open and close the section between the front surfaces of the heating chamber. A plurality of protrusions are provided at positions where the electric field is high in a groove provided to hold a glass plate covering a see-through window of the door, and the movement of the glass plate is restricted by the protrusions in the groove. The protrusion provided in the groove reduces the depth of the groove in areas where the electric field is high, reducing the electric field strength in the artificial part of the groove, which has the effect of preventing sparks and abnormal heating. It is.

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

In FIG. 2, there is a heating chamber 2 within the main body 1, and the front opening of the heating chamber 2 can be opened and closed by a door 3. 4
1 is an operation panel, which is provided with a fluorescent display tube 5 for displaying timer settings, output settings, etc., a program selection key 6, a start button, a cancel button 8, and the like.

Reference numeral 9 indicates an inner wall of the door that constitutes a part of the chalk wall provided in the door 3, and 10 indicates a window for seeing through.

In FIGS. 3 and 4, reference numeral 11 denotes a choke groove, which has a depth of approximately 174 mm, which corresponds to the wavelength used. The I-cheek groove 11 is comprised of a door inner wall 9, a door outer wall 12j', -J: and a separate metal 13 connected to the door inner wall by spot welding or the like. 14r1hide (a punching plate with many small holes to form one window, 15 is a glass plate to prevent food particles from getting stuck in these small holes. 1e & J: Dono゛17 is another glass plate provided on the outside of door 3, and 17 is a handle to be grasped when opening/closing door 3. J punching plate 14 and glass plate 16
f, J. By screwing the integrated door inner wall 9 and separate metal fitting 13 from the 1° attaching member 12 side, it is inserted and fixed in the groove 20 formed by them.

18 is a gasket to prevent the glass from breaking and to prevent hot air and steam generated from the food from escaping.

Note that since there is a coating film 19 on the surface of the glass plate 16, the screwed portions are hidden and cannot be seen from the surface.

A plurality of protrusions 21 are provided in the groove 20 that holds the glass plate 16.
is provided, and the depth of the groove 20 in this protrusion 21 is shallower by the height of the protrusion 21 than the part without the protrusion 21. The width of this protrusion 21 is approximately 1°C of the wavelength used.
74, and the distance (pitch) between one protrusion 21 and the next protrusion 21 is approximately 1/4 of the wavelength used.
The part without this protrusion 21 (X in the figure) has dimensions of
Separate metal fittings 13 and door inner wall 9
Spot welding is done.

The position where the protrusion 21 is provided is determined so as to be near the maximum electric field point according to the electric field distribution mode in the heating chamber 2.The specific method is to make a prototype door without a protrusion and actually make a prototype. The temperature of the groove 20 can be measured and observed over the entire circumference, and projections can be provided at the high points.

The reason why the protrusion must be provided in this way is that in order to spot weld the door inner wall 9 and the separate metal fitting 13, the depth of the groove 20 must be at least about 9 mm. As explained above, if glass is inserted into the groove, the actual depth of the groove for radio waves will be λ/2 times when the dielectric constant of glass is ε, so the dielectric constant ε of glass is For example, in the case of 5, the effective depth D' for radio waves of a groove with a depth of 9 sides is 20 degrees out of D' = 9 x 5.

The strength of the electric field at the entrance of the groove reaches its maximum when the depth of the groove reaches approximately 30 mm, which is 1/4 of the wavelength used, but due to the inclusion of glass, the actual depth of the groove becomes above As shown in FIG. 1, it approaches the .1' method of approximately λ/4, so when the maximum point of the electric field distribution in the heating chamber comes near this point, sparks and abnormal temperature rises occur in that area.

In this embodiment, in order to prevent this, a protrusion is provided in the groove 20 at a point where the electric field becomes locally high, and at the same time, the depth of the groove 2o is made shallow, and at the same time, the protrusion 21 allows entry into the groove. Since the dimensions of the glass are also reduced, the depth of the grooves 20 is doubly reduced, and the above-mentioned crackling and abnormal heat generation can be completely prevented.

Furthermore, due to the electric field distribution in the heating chamber 2, if there is one high electric field position, the next high electric field position will occur at a distance of approximately 172 wavelengths, so the width ρ of one protrusion 21 is approximately λ/4. In addition, from the center of the projection 21 to the other projection 2
1 and the center 1 is set to λ/2, that is, it is possible to have an effect on the electric field maximum points of all pitches P.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

■ Protrusions are provided only in the groove for holding the glass, where the maximum electric field point due to the electric field distribution pattern in the heating chamber is located.
Therefore, there is no problem in spot welding the inner wall of the door and the separate metal fittings, and abnormal temperature rises and spots can be completely prevented.

■ By providing a protrusion in the groove, the depth of the groove can be made shallow at that part, and at the same time, the size of the glass that enters the groove can be reduced. The electric field strength at 1 FIB can be kept sufficiently low.

■ Since the width of the protrusion provided in the groove is set to approximately 1/4 of the wavelength used, the oscillation frequency of the high-frequency oscillator will fluctuate slightly due to the 1'-1 load condition in the heating chamber, and the maximum electric field will be Even if the position moves a little, a sufficiently stable effect can be achieved.

■ If there are no protrusions in the groove, a gasket with a large cross-sectional area that can fill the entire groove is required to hold the glass in place. It is economical to hold the glass sufficiently with a gasket of that area.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part of a conventional high-frequency heating device, FIG. 2 is an external perspective view of a high-frequency heating device according to an embodiment of the present invention, and FIG. 3 is a door inner wall 9' of the door of the same device. f: Back view of the removed state; FIG. 4 is a sectional view taken along the line A-A in FIG. 3; 2... Heating chamber, 3... Door, 9...
Door inner wall, 13... Separate metal fittings, 15... Glass plate, 18... Gasket, 20... Groove, 21
··protrusion. Name of agent: Patent attorney Toshio Nakao and 1 other person:
A1 Figure 113 Figure 2 Figure 3 Figure 11 → ( Figure 4

Claims (1)

[Scope of Claims] (1) A heating chamber, a high-frequency oscillator that supplies high-frequency waves to the heating chamber, and a door that can open and close a front opening of the heating chamber, and a see-through window of the door is covered. 1. A high-frequency heating device comprising: a plurality of protrusions provided in a groove provided for the purpose of increasing the electric field; and a plurality of protrusions in the groove regulating the movement of the glass plate. ? ) The width of the multiple protrusions provided in the groove is approximately 1 of the wavelength used.
A high frequency heating device according to claim 1 ii+2 of Claim No. 74. (3) The high frequency heating device according to claim 1, wherein the pigginess between the protrusion provided in the groove and the other protrusions is approximately 1/2 of the wavelength used.