JPH0653683A - Radio wave leakage preventive structure for high frequency heater - Google Patents

Abstract

PURPOSE:To obtain a radio wave leakage preventing structure in which a radio wave leakage can be satisfactorily prevented and a door of a high frequency heater can be reduced in size. CONSTITUTION:A choke groove 30 has an inner wall 34, a bottom 36, an outer wall 35 and an opening 37. An upper part 38 of the wall 34 is connected to a door central plate 25. Slits 39 having periodicity are formed at the wall 35. A sealing plate 32 is provided in the opening 37 of the groove 30. The plate 32 has a step 40 raised from the wall 34 of the groove 30 inward of the door, an extended part 41 extended from an upper end of the step 40, and a bent part 42 bent in the groove 30 from the end of the extended part. An auxiliary groove 43 of a size to be decided by the step 40, the parts, 41, 42 and the part 38 is formed. The groove 43 is for varying a central frequency of a radio wave attenuating range of the groove 30 within a predetermined range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for preventing leakage of high frequency radio waves in a high frequency heating device.

[0002]

2. Description of the Related Art Conventionally, a structure for forming a choke groove has been known as a high-frequency radio wave leakage prevention structure in a high-frequency heating device. For example, Japanese Examined Patent Publication (Kokoku) No. 52-44815 discloses a high-frequency heater in which a choke groove is formed in the peripheral portion of the door in order to prevent radio waves from leaking from the periphery of the opening of the high-frequency heater. .

The high frequency heater disclosed in this publication is shown in FIG.
As shown in FIG. 3, a heating chamber 1 to which a radio wave is supplied is provided, and an opening 3 surrounded by an opening peripheral wall 2 is formed on the front surface of the heating chamber 1 for opening and closing the opening 3. A door 4 is provided. From the closed state of the door 4 shown in the figure, the hinge part 5
It can be freely opened in the direction of arrow A1 centering on. FIG. 11 is a schematic sectional view showing a characteristic structure in a frame W surrounded by, for example, an alternate long and short dash line shown in FIG. 10, for explaining a radio wave leakage prevention structure adopted in this high-frequency heater. FIG.

As shown in FIG. 11, the first radio wave attenuation groove 7 and the second radio wave attenuation groove 7 are formed on the peripheral edge of the door 4 facing the opening peripheral wall 2 by the door body plate 10, the door fitting 9, and the sealing plate 11. The radio wave attenuation groove 8 is formed. The first radio wave attenuation groove 7 is for shielding a radio wave of a fundamental frequency (for example, 2.45 GHz), and the second radio wave attenuation groove 8 is for shielding a second harmonic of the fundamental frequency. . Therefore, the dimension L1 of the first radio wave attenuation groove 7 seen from the groove entrance E is 1/4 wavelength of the fundamental wave = 30.6 (mm),
The dimension L2 of the second radio wave attenuation groove 8 seen from the entrance E is set to 3/4 wavelength of the second harmonic = 45.9 (mm).

As another conventional technique, Japanese Patent Publication No. 1-36.
There is a radio wave sealing device described in Japanese Patent No. 717. The radio wave sealing device described in this publication also forms a choke groove in the peripheral portion of the door, and the choke groove is divided into a first groove and a second groove by a door fitting provided with a slit having periodicity. A configuration is adopted in which a leaked radio wave having an oscillation frequency of 2450 (MHz) and a leaked radio wave of 915 (MHz) are attenuated by two types of grooves.

[0006]

Of the above-mentioned conventional techniques,
In the structure described in the former publication, as shown in FIG. 11, the second radio wave attenuation groove 8 extends toward the center of the door 4 (leftward in the drawing), and its dimension L2 is the second. It is 3/4 wavelength of the harmonic. Therefore, the door central plate connected to the inside (left side) of the second radio wave attenuation groove 8 becomes smaller. Alternatively, in order to keep the area of the door center plate connected to the inside to a predetermined size, the entire door is closed by the second radio wave attenuation groove 8 and the first radio wave attenuation groove 7 provided on the outer peripheral portion of the door center plate. Has the drawback that it becomes large.

This inner door center plate is usually formed with a large number of small holes (punching holes), and a glass plate for heat shielding is brought into contact with the inner surface or the outer surface thereof so that the inside of the heating chamber 1 can be visually recognized. Has been done. Therefore, if the center plate of the door is too small, the visibility in the heating chamber 1 is poor, and there is a drawback that the material being cooked cannot be confirmed. Therefore, it is necessary to secure the door center plate in a predetermined size.

Therefore, the above Japanese Patent Publication No. 52-44815.
The radio wave leakage prevention structure described in Japanese Patent Publication has a drawback that should be improved in order to reduce the size of the door. On the other hand, in the latter radio wave leakage prevention structure disclosed in Japanese Patent Publication No. 1-36717, the leaked radio waves are attenuated in the straight line portion of the peripheral portion of the door, but the structure of the corner portion of the door is unsatisfactory. Since it is sufficient, radio waves may leak at the corners of the door.

The present invention has been made in order to overcome the above-mentioned drawbacks of the prior art, and in a high-frequency heating device, leaked radio waves can be excellently blocked, and moreover,
An object of the present invention is to provide a structure for preventing electric wave leakage, which can realize downsizing of a door of a high frequency heating device.

[0010]

The invention according to claim 1 is
It has a heating chamber into which radio waves are supplied, an opening surrounded by an edge frame is formed on the front surface of the heating chamber, and a door for opening and closing the opening is provided. The door is the opening of the heating chamber. Having a door center plate facing to, and a peripheral edge portion surrounding the door center plate,
The door peripheral portion is made to face the opening edge frame of the heating chamber when closed, and a choke groove for shielding high frequency radio waves leaking from the heating chamber is formed at the door peripheral portion facing the opening edge frame. In the radio wave leakage prevention structure of the high-frequency heating device, the choke groove extends facing the opening edge frame,
A pair of side walls, a bottom surface, and an opening, and an upper portion of the inner side wall of the pair of side walls is connected to the door center plate,
A slit having periodicity in the longitudinal direction of the opening edge frame is formed on the outer side wall of the pair of side walls, and the choke groove opening is a seal for covering a part of the choke groove opening. A plate is provided, and the sealing plate includes a step portion that rises inward of the inner side wall of the choke groove in a direction opposite to the depth direction of the choke groove, and a bottom surface of the choke groove that is bent from the upper end of the step portion. The stepped portion, the extended portion, the bent portion, and the door are provided with an extending portion that extends substantially parallel to the outer side wall of the choke groove and a bent portion that is bent from the tip of the extended portion toward the bottom surface of the choke groove. An auxiliary groove having a predetermined size is formed by the frame plate.

According to a second aspect of the present invention, there is provided a heating chamber into which radio waves are supplied, and an opening surrounded by an edge frame is formed on the front surface of the heating chamber, and a door for opening and closing the opening is formed. And a door having a door center plate facing the opening of the heating chamber and a peripheral portion surrounding the door center plate, the door peripheral portion facing the opening edge frame of the heating chamber when closed. To be
In the radio wave leakage prevention structure of the high frequency heating device, a choke groove for shielding high frequency radio waves leaking from the heating chamber is formed on the peripheral edge of the door facing the opening edge frame. And has a pair of side walls, a bottom surface, and an opening, and an upper part of an inner side wall of the pair of side walls is connected to the door center plate, and an outer side of the pair of side walls. Has a slit having a periodicity in the longitudinal direction of the opening edge frame, and the choke groove opening is provided with a sealing plate for covering a part of the choke groove opening. The sealing plate has a step portion that rises in the direction opposite to the depth direction of the choke groove, an extending portion that bends from the upper end of the step portion and extends toward the outer side wall of the choke groove almost parallel to the bottom surface of the choke groove, and an extending portion. Bend from the tip of the to the bottom of the choke groove. The bent length of the bent portion is shorter than that of other portions in the corner portion of the choke groove facing the corner portion of the opening edge frame. is there.

[0012]

According to the first aspect of the invention, the leaked radio waves of the fundamental frequency are mainly attenuated by the choke groove. An auxiliary groove is formed by a sealing plate that covers part of the opening of the choke groove.By changing the shape of this auxiliary groove, the center frequency of the frequency range of the radio wave attenuated by the choke groove is located. Move a fixed amount. Therefore, by setting the size of the auxiliary groove, it is possible to set the center frequency of the frequency range of the radio wave attenuated by the choke groove to a desired frequency.

According to the second aspect of the present invention, by changing the bending length of the bent portion of the sealing plate between the corner portion and the non-corner portion, It is possible to have a structure in which the choke groove satisfactorily attenuates radio waves.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a main part of a high-frequency heating device that employs a radio wave leakage prevention structure according to an embodiment of the present invention, which is drawn in comparison with the conventional example shown in FIG. In FIG. 1, 21 is an edge frame,
The edge frame 1 forms a heating chamber 20 and an opening 22 on the front surface of the heating chamber 20. A door 2 for opening and closing the opening 22 is provided on the front surface of the heating chamber 20.
3 is provided. From the closed state shown in the figure, the door 23 is centered around a hinge mechanism or the like on the left side of the figure, and is indicated by an arrow A2.
It can be opened in any direction.

The door 23 includes a door frame plate 24, a door center plate 25, a glass plate 26 fixed in contact with an inner surface of the door center plate 25, and a door cover 2 covering the entire front side of the door 23.
7 and 7. A large number of punching holes 29 are formed in the door central plate 25. Further, the peripheral edge portion 28 of the door 23 is configured to face the edge frame 21 of the heating chamber 20 when closed. Further, a choke groove 30 for shielding high frequency radio waves leaking from the heating chamber 20 is formed in the facing door peripheral portion 28.

The choke groove 30 is formed by the door frame plate 24, the door fitting 31, and the sealing plate 32, and extends in the direction perpendicular to the paper surface so as to face the edge frame 21.
In addition, the opening 37 of the choke groove 30 facing the edge frame 21.
Is covered with a cover member 33 formed of a low-loss dielectric material such as polypropylene. FIG. 2 is a diagram for explaining a more detailed structure and operation of the choke groove 30 formed in the peripheral edge portion 28 of the door shown in FIG.

Referring to FIG. 2, the choke groove 3 will be described.
0 is the inner side wall 3 formed by a part of the door frame plate 24
4, an outer wall 35 formed by the door fitting 31, a bottom surface 36 formed by a part of the door frame plate 24, and an opening 37. An upper portion 38 of the inner wall 34 is bent inward of the door and connected to the door center plate 25.
Further, the outer wall 35 has a direction perpendicular to the paper surface, that is, as shown in FIG.
The slit 39 having periodicity in the longitudinal direction of the edge frame 21 shown in FIG.
Are formed. The configurations of the outer wall 35 and the slit 39 will be described later in detail.

The opening 37 is provided with a sealing plate 32 for covering a part of the opening 37. Sealing plate 32
In this embodiment, is formed by extending the edge portion of the door center plate 25. The sealing plate 32 has an inner wall 34.
A step portion 40 that rises from a predetermined position on the upper portion 38 of the choke groove 30 in a direction opposite to the depth direction of the choke groove 30 (the direction from the opening 37 to the bottom surface 36), and the bottom surface 36 of the choke groove 30 that bends from the upper end of the step portion 40 30 parallel choke grooves
An extending portion 41 extending toward the outer side wall 35, and a bent portion 42 bent from the tip of the extending portion 41 toward the bottom surface 36 of the choke groove 30.

In the above embodiment, the door central plate 25
Although the end plate is extended to form the sealing plate 32, the door center plate 25 and the sealing plate 32 may be formed of different plate materials. Further, the door center plate 25 and the door frame plate 24 may be integrally formed. One of the features of this embodiment is that the step portion 40 rises on the inner side of the door with respect to the inner side wall 34. As a result, the auxiliary groove 4 is formed by the step portion 40, the extending portion 41, the bent portion 42, and the upper portion 38 of the inner wall 34.
3 is formed.

As for the size of the auxiliary groove 43, the dimension from the inner wall 34 to the rising position of the step 40 is a, and the step 40
Assuming that the rising dimension of b is b and the dimension of the extending portion 41 is c, in this embodiment, a ≧ 3 (mm) and b ≧ 3 (m
m) and c ≧ 6 (mm). Dimension c is 6 (m
The reason for setting m or more is to secure a sufficient facing distance between the sealing plate 32 and the edge frame 21, as shown in FIG.

In such a structure, the traveling directions of the electric waves leaking from the heating chamber 20 (see FIG. 1) can be roughly classified into two types. That is, one is a leaked radio wave that travels in the direction indicated by arrow A3 in FIG. 2, and the other is a leaked radio wave that travels in the direction indicated by symbol A4 in FIG. 2 (a direction perpendicular to the paper surface). Among them, the leaked radio wave traveling in the direction of arrow A3 is attenuated by the choke groove 30. That is, the choke groove 30 is formed mainly for the purpose of attenuating the leaked radio waves traveling in the direction of the arrow A3 among the leaked radio waves of the fundamental frequency generated in the heating chamber 20 (see FIG. 1). If the center frequency of the frequency range of the radio wave attenuated by the choke groove 30 is f (MHz), f is set to a constant close to 2450 when the high frequency heating device is a microwave oven.

On the other hand, the auxiliary groove 43 has a center frequency f (MH) in the frequency range of the radio wave attenuated by the choke groove 30.
z) is moved by a predetermined amount. The operation of the auxiliary groove 43 will be described more specifically. As described above, the size of the auxiliary groove 43 ranges from the inner wall 34 to the step portion 4.
It can be represented by the dimension a up to the rising position of 0, the rising dimension b of the step portion 40, and the dimension c of the extending portion 41. Of these, when the cross-sectional area of the auxiliary groove 43 represented by a × b is changed under constant conditions, the center frequency f (M of the frequency range of the radio wave attenuated by the choke groove 30 is
Hz) can be moved.

For example, the center frequency f of the radio wave attenuation region
There are two methods for moving (MHz) in the direction of lower frequency. By moving the rising position of the step 40 of the sealing plate 32 shown in FIG. 2 to the inner side (left side in the figure) of the door, the dimension a and the dimension c are increased. At this time, the rising dimension b of the step portion 40 is not changed. In addition, the shape of the other portions forming the choke groove 30 is not changed. By doing this, the center frequency of the radio wave attenuation region moves from f (MHz) to f-α (MHz).

The inner wall 34 shown in FIG.
The rising dimension b of the step portion 40 of the sealing plate 32 is increased by that amount. In this case, the depth of the choke groove 30 does not change, but the dimension b of the auxiliary groove 43 increases. In this case, the other dimensions a and c of the auxiliary groove 43 are not changed. Further, the dimensions of the other portions forming the choke groove 30 are not changed. By doing this, the center frequency of the radio wave attenuation region is f
(MHz) to f-α (MHz).

It is to be noted that α in the above and is a positive constant in the range of several (MHz) to several hundred (MHz).
Thus, by changing the cross-sectional area of the auxiliary groove 43, that is, a × b, and increasing the cross-sectional area a × b,
The center frequency f of the radio wave attenuation area due to the choke groove 30 is
Can be moved lower.

On the contrary, in order to move the center frequency f (MHz) of the frequency range of the radio wave attenuated by the choke groove 30 to the higher frequency side, the cross-sectional area a × b of the auxiliary groove 43 should be reduced. The shape of the auxiliary groove 43 may be changed.
That is, as one method, the step portion 40 of the sealing plate 32 is used.
That is, the rising position of is moved toward the inner wall 34 (to the right in the drawing) to reduce the dimension a and the dimension c.

Another method is to reduce the rising dimension b of the step portion 40 of the sealing plate 32 without changing the depth of the choke groove 30. In this way, the auxiliary groove 4
Since the center frequency of the radio wave attenuation region of the choke groove 30 can be changed by changing the cross-sectional area a × b of the choke groove 30, the choke groove 30 can be formed in a shape that attenuates radio waves in a desired frequency band.

FIG. 3 is a perspective view of the door fitting 31. The door fitting 31 forms the outer wall 35 of the choke groove 30 as described above, and the outer wall 35 is formed with the slit 39 having a periodicity. The slits 39 have a width dimension of X and are periodically formed with a pitch interval of Y. As a result, a leaked radio wave traveling in the peripheral direction of the opening 22 (see FIG. 1) of the heating chamber 20 (a leaky radio wave traveling in the direction of arrow A4 in FIG. 3, this leaked radio wave is denoted by symbol A4 in FIG. 2).
It is shown in. ) Can be attenuated.

The door fitting 31 has a bent portion 50 formed by bending the upper portion of the outer side wall 35 by approximately 90 degrees. The bending width of the bent portion 50 is Z. As shown in FIG. 2, the bent portion 50 is bent toward the inner wall 34, and the bent portion 50 covers a part of the opening 37 of the choke groove 30. Door fitting 31
With such a configuration, the center frequency q (MHz) of the frequency region of the leaked radio wave traveling in the arrow A4 direction attenuated by the outer wall 35 is attenuated by the choke groove 30 (in the arrow A3 direction in FIG. 2). It can be set to a desired value by the width dimension X, the pitch interval Y, and the bending width Z of the slit 39 described above, irrespective of the center frequency f (MHz) of the frequency region of the traveling radio wave). Therefore, the center frequency q (MHz) of the frequency region of the leaked radio wave traveling in the direction of the arrow A4 is, for example, 2450.
It can be set near (MHz).

Returning to FIG. 2, in this embodiment, the outer wall 3
Although 5 is formed by the door metal fitting 31 different from the door frame plate 24, the outer peripheral wall 35 may be formed by bending the outermost peripheral portion of the door frame plate 24 instead. Further, in FIG. 2, the step portion 40 of the sealing plate 32 is a door central plate 25.
It rises in the direction opposite to the depth direction of the choke groove 30 (toward the heating chamber 20 as shown in FIG. 1). Therefore, the inner surface side of the door center plate 25 is surrounded by the step portion 40. Therefore, if the glass plate 26 is attached to this portion, there is an advantage that the glass plate 26 can be easily positioned and fixed. The glass plate 26 is provided to block the heat in the heating chamber 20 from leaking out from the many punching holes 29 formed in the door central plate 25.

FIG. 4 is a cross-sectional view of a main part of a high-frequency heating apparatus adopting a radio wave leakage prevention structure according to another embodiment of the present invention, which is drawn in comparison with the embodiment shown in FIG. . 4, constituent elements that are the same as or correspond to those in FIG. 1 are given the same reference numerals. The feature of the configuration shown in FIG. 4 is that the rising position of the sealing plate 32 is different from that in the embodiment of FIG. This point will be described with reference to FIG.

FIG. 5 is a view for explaining the more detailed structure and operation of the choke groove 30 formed in the peripheral portion 28 of the door shown in FIG. Referring to FIG. 5,
The choke groove 30 includes an inner wall 34 formed by a part of the door frame plate 24, an outer wall 35 formed by a door fitting 31, and a bottom plate 3 formed by a part of the door frame plate 24.
6 and an opening 37. Upper part 38 of the inner wall 34
Is bent inward of the door and connected to the door center plate 25. Further, the outer wall 35 is formed with a slit 39 having a periodicity in a direction perpendicular to the paper surface, that is, in the longitudinal direction of the edge frame 21 shown in FIG. The configurations of the outer wall 35 and the slit 39 are the same as those of the above-described embodiment (see FIG. 3).

At the opening 37, a sealing plate 32 for covering a part of the opening 37 is formed. On the sealing plate 32,
In this embodiment, the edge portion of the door center plate 25 is formed by being extended. The sealing plate 32 has a step portion 40 that rises in a direction opposite to the depth direction of the choke groove 30 (the direction from the opening 37 toward the bottom surface 36) so that the upper edge of the inner wall 34 extends upward. Bending from the upper end, the choke groove 30 is substantially parallel to the bottom surface 36 of the choke groove 30.
An extending portion 41 extending toward the outer side wall 35, and a bent portion 42 bent from the tip of the extending portion 41 toward the bottom surface 36 of the choke groove 30.

In this case, the extending portion 4 of the sealing plate 32
The dimension of 1 is h, the dimension of the bent portion 42 is i, and the distance from the tip of the extending portion 41 to the tip of the upper bent portion 50 of the outer wall 35 is j. In such a configuration, the heating chamber 20 (see FIG.
The traveling directions of radio waves leaking from (see) can be roughly classified into two types. That is, one is a leaked radio wave traveling in the direction indicated by arrow A3 in FIG. 5, and the other is a leaked radio wave traveling in the direction indicated by symbol A4 in FIG. Among them, the leaked radio wave traveling in the direction of arrow A3 is attenuated by the choke groove 30. That is,
The choke groove 30 is formed mainly for the purpose of attenuating leaked radio waves traveling in the direction of arrow A3 among leaked radio waves of the fundamental frequency generated in the heating chamber 20 (see FIG. 4). If the center frequency of the frequency range of the radio wave attenuated by the choke groove 30 is f (MHz), f is set to a constant close to 2450 when the high frequency heating device is a microwave oven.

On the other hand, if the shape of the sealing plate 32 is partially changed as described below, the center frequency f (MHz) can be moved to a lower frequency or a higher frequency. For example, if the dimension h of the extension 41 of the sealing plate 32 shown in FIG. 5 is lengthened, the center frequency f (MHz) of the radio wave attenuation region moves in the direction of lower frequency.

Further, the bent portion 4 of the sealing plate 32 shown in FIG.
If the dimension i of 2 is increased, that is, the bending length of the bent portion 42 is increased, the center frequency f (MH) of the radio wave attenuation region is increased.
z) can be moved to lower frequencies. On the contrary, if the dimension h is shortened or the dimension i is shortened, the center frequency f of the radio wave attenuation region can be moved in the higher frequency direction.

As described above, by changing the dimension h or the dimension i of the sealing plate 32, the center frequency of the radio wave attenuation region of the choke groove 30 can be changed.
The choke groove 30 can be easily designed in a shape that attenuates radio waves in a desired frequency band. Note that the leaked radio waves propagating in the direction perpendicular to the surface of the paper indicated by reference numeral A4 can be attenuated by the outer wall 35, as in the above-described embodiment.

By the way, the structure of the choke groove 30 shown in FIG. 5 is a good electromagnetic wave leakage prevention structure near the center of one side of the door, that is, when the choke groove 30 extends in the direction perpendicular to the paper surface in FIG. However, in the vicinity of the corner of the door, it cannot be said that it is an optimal radio wave leakage prevention structure.
Because near the corner of the door, choke groove 3
The inner wall 34 of 0 is normally narrowed and curved into a quarter circle shape.

The extending portion 41 of the sealing plate 32 is also narrowed down and curved in a quarter circle shape. Therefore, the cross-sectional shape of the choke groove 30 near the corner portion of the door is different from the cross-sectional shape near the center of one side of the door where the choke groove 30 extends straight. Therefore, even if the choke groove 30 near the center of one side of the door can sufficiently attenuate the radio wave of the fundamental frequency, the choke groove 30 near the corner of the door may not sufficiently attenuate the radio wave of the fundamental frequency.

Therefore, in this embodiment, as will be described below, the bending dimension i of the bent portion 42 of the sealing plate 32 is made different near the center of one side of the door and near the corner. A more specific description will be given with reference to FIG. FIG. 6 shows the door 2
3 is a partial plan view of a corner portion of FIG. In FIG. 6, the outer peripheral edge of the door central plate 25 is narrowed and curved at the corner portion of the door. Further, the sealing plate 32 connected to the outer peripheral edge of the door center plate 25 is also curved at the corner portion. On the other hand, the outer wall 35 is also linear in the corner portion.

Now, in FIG. 6, the outer peripheral edge of the door center plate 25, that is, the inner side wall 34 (see FIG. 5), is from point P to point Q.
In, a 1/4 circular curve is attached. Also,
A 1/4 circular curve is also attached to the tip of the extending portion 41 of the sealing plate 32. Therefore, in FIG. 6, points P and Q are moved to the right, points that reach the outermost periphery of the sealing plate 32 are points R and S, and similarly, points P and Q are moved downward. The points reaching the outermost circumference of the sealing plate 32 are defined as points T and U. Then, the 1/4 circular curve formed on the outermost periphery of the sealing plate 32 starts from the point S to the point T. However, in the present embodiment, the shapes of the inner wall 34 of the choke groove 30 and the corners of the sealing plate 32 are not limited to the 1/4 circular curved shape, and may be, for example, a right-angled shape.

On the other hand, the leaked radio wave attenuated by the choke groove 30 advances in the direction of arrow A3. In order to surely attenuate the leaked radio waves traveling in the direction of the arrow A3 in the choke groove 30, the dimension of the bent portion 42 (see FIG. 5) at the outermost peripheral corner portion of the sealing plate 32, that is, from the point S to the point T. i
Needs to be different compared to the straight part. This is because, in the vicinity of the center of one side of the door, the dimensions h and j described in FIG. 5 can be represented by h1 and j1 as shown in FIG. 6, but they can be represented by h2 and j2 in the corner portion of the door. Be done. Here, in the peripheral portion of the sealing plate 32, since a point R to a point S is a straight line, j1 = j
However, since the dimension h2 is between the point P and the point Q,
h2> h1. Therefore, even if the choke groove 30 near the center of one side of the door can sufficiently attenuate the radio wave of the fundamental frequency,
In the vicinity of the corner portion of the door, the center frequency of the radio wave attenuated by the choke groove 30 moves to a direction lower than the fundamental frequency, and the leaked radio wave cannot be attenuated sufficiently.

Therefore, in order to increase the center frequency of the frequency range of the radio wave attenuated by the choke groove 30 near the corner of the door and match it with the fundamental frequency, the sealing plate 32 is used.
The dimension i (see FIG. 5) of the bent portion 42 at the tip of is continuously shortened from the point R to the point S, and is made constant from the point S to the point T, and continuously from the point T to the point U. It is designed to be long. This is one of the features of this embodiment.

FIG. 7 shows the sealing plate 3 near the corner of the door.
It is the figure which took out and expanded only the bending part 42 of 2. As is clear from FIG. 7, the bent portion 42 has a relatively long dimension i1 from the center of one side of the door to the point R, is gradually shortened from the point R to the point S, and is gradually shortened from the point S to the point S. The dimension i2 is relatively short up to T, the length is gradually increased from the point T to the point U, and the dimension i1 is again after the point U.

The bent portion 42 of the sealing plate 32 may have the size shown in FIG. 8 or 9, for example, instead of the size shown in FIG. That is, in FIG. 8, the dimension i of the bent portion 42 may be minimized only in the central portion of the corner portion, and the dimension may gradually increase from the central portion of the corner portion to the points R and U. Further, as shown in FIG. 9, the dimension of the bent portion 42 may be minimized at the points S and T, and the dimension i of the bent portion 42 may be slightly increased at the central portion of the corner portion.

In the above description, in the embodiment described with reference to FIGS. 4 and 5, the case where the dimension of the bent portion 42 of the sealing plate 32 is changed in the corner portion of the door has been taken up. Also in the embodiment shown in (1), the same effect can be obtained by changing the size of the bent portion 42 of the sealing plate 32 at the corner portion of the door.

Besides, the present invention can be variously modified within the scope of the claims.

[0048]

According to the invention as set forth in claim 1, in the high frequency heating device, the center frequency of the frequency region of the attenuation radio wave of the choke groove can be moved by changing the shape of the auxiliary groove. It is possible to provide a radio wave leakage prevention structure that can have a shape capable of attenuating a desired frequency and can effectively prevent leaked radio waves.

Further, according to the first aspect of the invention, it is possible to provide a radio wave leakage preventing structure capable of downsizing the door without reducing the central plate of the door and increasing the appearance of the door. According to the invention of claim 2,
It is possible to provide a radio wave leakage prevention structure in which leaked radio waves can be favorably attenuated even near the corners of the door.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts of a high-frequency heating device that employs a radio wave leakage prevention structure according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a more detailed configuration and action of a choke groove 30 formed in a peripheral edge portion 28 of the door shown in FIG.

FIG. 3 is a perspective view of a door fitting 31.

FIG. 4 is a cross-sectional view of a main part of a high-frequency heating device that employs a radio wave leakage prevention structure according to another embodiment of the present invention.

5A and 5B are views for explaining a more detailed configuration and action of a choke groove 30 formed in the peripheral edge portion 28 of the door shown in FIG.

FIG. 6 is a partial plan view of a corner portion of a door 23.

FIG. 7: Bent portion 4 of the sealing plate 32 near the corner of the door
It is the figure which extracted and expanded only 2.

FIG. 8 is a development view showing another embodiment of the bending portion 42.

FIG. 9 is a development view showing still another embodiment of the bending portion 42.

FIG. 10 is a cross-sectional view of a high frequency heater in which a conventional high frequency radio wave leakage prevention structure is adopted.

11 is a schematic cross-sectional view showing a characteristic structure in a frame W surrounded by the alternate long and short dash line shown in FIG.

[Explanation of symbols]

 20 Heating Chamber 21 Edge Frame 22 Opening 23 Door 24 Door Frame Plate 25 Door Center Plate 26 Glass Plate 28 Edge of Door 29 Punching Hole 30 Choke Groove 31 Door Metal Fitting 32 Sealing Plate 34 Inner Side Wall 35 Outer Side Wall 36 Bottom 37 Open 39 Slit 40 Stepped portion 41 Extending portion 42 Bent portion 43 Auxiliary groove

Claims (2)

[Claims] 1. A heating chamber having a radio wave supplied therein, an opening surrounded by an edge frame is formed on a front surface of the heating chamber, and a door for opening and closing the opening is provided. A door center plate facing the opening of the heating chamber, and a peripheral edge portion surrounding the door center plate, the door peripheral portion facing the opening edge frame of the heating chamber when closed, and the opening edge frame. In the radio wave leakage prevention structure of the high frequency heating device, a choke groove is formed in the peripheral edge of the door facing to the high frequency radio wave leaking from the heating chamber. A pair of side walls, a bottom surface, and an opening, and an upper part of the inner side wall of the pair of side walls is connected to the door center plate. Has a slit with periodicity in the longitudinal direction of the opening edge frame. The opening is provided with a sealing plate for covering a part of the opening of the choke groove, and the sealing plate rises inward from the inner side wall of the choke groove in a direction opposite to the depth direction of the choke groove. A stepped portion, an extending portion bent from the upper end of the stepped portion and extending in the outer sidewall direction of the choke groove substantially parallel to the bottom surface of the choke groove, and a bent portion bent from the tip of the extending portion toward the bottom surface of the choke groove. A radio wave leakage prevention structure for a high-frequency heating device, comprising: an auxiliary groove having a predetermined size formed by the step portion, the extending portion, the bent portion, and the door frame plate. 2. A heating chamber having a radio wave supplied therein, an opening surrounded by an edge frame is formed on the front surface of the heating chamber, and a door for opening and closing the opening is provided. A door center plate facing the opening of the heating chamber, and a peripheral edge portion surrounding the door center plate, the door peripheral portion facing the opening edge frame of the heating chamber when closed, and the opening edge frame. In the radio wave leakage prevention structure of the high-frequency heating device, a choke groove is formed in the peripheral edge of the door facing to the heating chamber to shield high-frequency radio waves leaking from the heating chamber. A pair of side walls, a bottom surface, and an opening, and an upper part of the inner side wall of the pair of side walls is connected to the door center plate. Has a slit with periodicity in the longitudinal direction of the opening edge frame. The opening is provided with a sealing plate for covering a part of the opening of the choke groove, and the sealing plate bends from a step portion rising in a direction opposite to the depth direction of the choke groove and an upper end of the step portion. Equipped with an extension that extends in the direction of the outer sidewall of the choke groove almost parallel to the bottom of the choke groove, and a bend that is bent from the tip of the extension to the bottom of the choke groove. The radio wave leakage prevention structure for a high-frequency heating device, wherein the corner portion of the choke groove facing the corner portion of the opening edge frame is shorter than the other portions.