JPS6250955B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application 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. This see-through window uses a punched plate with many small holes in a metal plate to prevent radio waves from leaking through it, and a glass plate is used to prevent food particles from getting stuck in the holes of the punched plate. A board cover is provided.

Normally, this glass cover is held in place by a groove formed by a punching plate, the inner wall of the door, and other metal fittings, but as is well known, glass has a higher dielectric constant than air, so the actual The depth D' of the groove with respect to radio waves is D'=D√ However, D=depth of the groove without glass ε=permittivity of the glass, which is considerably deeper than without glass.

Therefore, the actual dimension from the end to the entrance of the groove approaches the dimension of λ/4, which increases the electric field strength at the entrance of the groove, causing sparks and abnormal temperature rises at the entrance of the groove. etc. are more likely to occur. Of course, these abnormal phenomena are greatly influenced by the electric field distribution pattern within the heating chamber, and therefore occur at locations where the high electric field position due to the electric field distribution pattern matches the depth of the groove as described above.

In order to solve this problem, the groove dimensions must be made as shallow as possible, but in the conventional structure shown in FIG.
In order to prevent the head from protruding, the door inner wall 9 and the separate metal fitting 13 must be spot welded within the groove 20, so it cannot be made shallower than a certain level.

OBJECTIVES 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. do.

Structure of the Invention In order to achieve the above object, the present invention includes 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 a front opening of the heating chamber, and a door for transparent viewing of the door. A plurality of protrusions are provided at positions where the electric field is high in a groove provided to hold a glass plate that covers a window, and the movement of the glass plate is restricted by the protrusions in this groove. Because the depth of the groove in the portion where the electric field is high is reduced by the protrusion provided on the groove, the electric field strength at the entrance of the groove is lowered, which has the effect of preventing sparks and abnormal heating.

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 is the operation panel, timer settings,
A fluorescent display tube 5 for displaying output settings, a program selection key 6, a start button 7, a cancel button 8, etc. are provided.

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

In FIGS. 3 and 4, reference numeral 11 is a chiyoke groove, which has a depth of about 1/4 of the wavelength used. The chain yoke groove 11 is connected to the inner wall 9 of the door, the outer wall 12 of the door, and a separate metal fitting 1 connected to the inner wall of the door by spot welding or the like.
3. 14 is a punching plate provided with a large number of small holes to form a see-through window, and 15 is a glass plate for preventing food particles from clogging the small holes. 16 is another glass plate provided on the outside of the door 3, and 17
is a handle that is grasped when opening and closing the door 3.

The punching plate 14 and the glass plate 15 are fixed by being sandwiched between the grooves 20 formed by the door inner wall 9 and the separate metal fittings 13 and screwed together from the door outer wall 12 side.

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

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 15, and the depth of the groove 20 in the protrusion 21 is larger than the part without the protrusion 21.
It is shallower by the height of 1. The width l of this protrusion 21 is about 1/4 of the wavelength used, and the pitch between one protrusion 21 and the next protrusion 21 is also about 1/4 of the wavelength used. The separate metal fitting 13 and the door inner wall 9 are spot welded in the area where the protrusion 21 is not present (the area marked with an x in the figure).

Further, the position where the protrusion 21 is provided is in the heating chamber 2.
The electric field is determined to be near the maximum point of the electric field due to the electric field distribution mode in All you have to do is measure it over the area and place protrusions at the high points.

The reason why it is necessary to provide the protrusion 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, when the dielectric constant of glass is ε, the actual depth of the groove for radio waves becomes √ times the dimension, so if the dielectric constant ε of glass is 5, for example, the depth of the groove for radio waves is 9 mm. The effective depth D' for radio waves of a groove with a depth of is D'=9×√≒20 mm.

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 greater than the above-mentioned depth. Since the dimension approaches approximately λ/4, when the maximum point of the electric field distribution in the heating chamber comes near this area, 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 the depth of the groove 20 is made shallow. Since the dimensions of the groove 20 are also reduced, the depth of the groove 20 is doubly reduced, and the sparks and abnormal heat generation described above can be completely prevented.

Furthermore, due to the electric field distribution within the heating chamber 2, if there is one high electric field position, the next high electric field position will occur at a location approximately 1/2 of the wavelength used.
If the width l is about λ/4, and the distance from the center of one protrusion 21 to the center of another protrusion 21 is λ/2, then the effect will be You can have it.

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

Since the protrusion is 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, there is no problem in spot welding the inner wall of the door and another metal fitting, and it is possible to prevent abnormal temperatures. Climbing and spots can be completely prevented.

By providing a protrusion in the groove, the depth of the groove can be reduced at that part, and at the same time, the size of the glass that enters the groove can be reduced, so the size of the structure can be made doubly shallower, and the entrance area of the groove can be reduced. The electric field strength at can be kept sufficiently low.

Because the width of the protrusion in the groove is set to approximately 1/4 of the wavelength used, the oscillation frequency of the high-frequency oscillator may vary slightly depending on the load conditions in the heating chamber, and the maximum electric field position may shift slightly. However, it is possible to have a sufficiently stable effect.

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 stably hold the glass, but by providing multiple protrusions, a gasket with a small cross-sectional area is sufficient to hold the glass. can be maintained and is economical.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the main parts of a conventional high-frequency heating device, Fig. 2 is an external perspective view of a high-frequency heating device which is an embodiment of the present invention, and Fig. 3 shows the inner wall 9 of the door of the same device. FIG. 4 is a rear view of the removed state, and 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.

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 freely open and close a front opening of the heating chamber, and a glass that covers a see-through window of the door. A high-frequency heating device having a structure in which a plurality of protrusions are provided at positions where the electric field is high in a groove provided for holding a plate, and the movement of the glass plate is restricted by the protrusions in the groove. 2. The high-frequency heating device according to claim 1, wherein the width of the plurality of protrusions provided in the groove is approximately 1/4 of the wavelength used. 3. The high-frequency heating device according to claim 1, wherein the pitch between the protrusions provided in the groove and other protrusions is approximately 1/2 of the wavelength used.