JP2007317607A - High frequency heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To relatively control a high frequency leakage amount from respective parts of a door outer circumference. <P>SOLUTION: The high frequency heating device is provided with a main body 2 including a casing having a heating chamber 1 which has a rectangular opening part 1a formed on a front surface and is supplied with high frequency to an inside, and having a frame-like opening part sheet metal 2a in a peripheral part of the rectangular opening part 1a, and a door 3 which is mounted on the main body 2 through a hinge, covers the rectangular opening part 1a so as to be opened and closed freely, and includes a choke structure 4 having dead-end like comb teeth with slits 10 formed periodically for preventing electrical wave leakage over an entire circumference on a part facing to the opening part sheet metal 2a. An arrangement cycle of the slits 10 of at least one side of the choke structure 4 and arrangement cycles of the slits of the other sides of the choke structure 4 out of the four sides of the choke structure of the entire circumference of the door are made different. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high-frequency heating apparatus that can relatively control the amount of high-frequency leakage from each part of the door outer periphery.

  A main body comprising a casing having a rectangular opening on the front surface and a heating chamber in which high frequency is supplied inside, and a frame-shaped opening sheet metal in the periphery of the rectangular opening, and the main body There is known a high-frequency heating apparatus including a door that is attached via a hinge and covers the rectangular opening so as to be freely opened and closed. In such a high-frequency heating device, a high frequency (2.45 GHz microwave in the case of a microwave oven) is used for cooking. By the way, if a high frequency leaks to the outside during cooking, an undesirable effect is exerted on the human body. Therefore, various measures are taken to prevent the leakage of the high frequency. Among them, it is particularly important to take measures against high frequencies that try to leak from the gap between the door and the main body. In addition, the specification of the leakage power required for the microwave oven is 1.0 mW / cm2 when the door is closed, and 5.0 mW / cm when the door is opened, based on the legal regulation value, where the amount of high-frequency leakage around the 50 mm outside the housing is the power density. Needless to say, it is desirable to keep the leaking high frequency as small as possible, although it is determined to be cm2.

  As a technique for suppressing the amount of high-frequency leakage that leaks from the gap between the door and the main body, the peripheral part (four sides) of the door is bent into a bag path shape, and slits are provided periodically to form a comb-tooth shape. A choke structure is known (see, for example, Patent Document 1).

JP 2000-291959 A (FIGS. 13 and 19)

  By the way, the amount of high frequency leakage from each part of the door differs depending on the shape of the heating chamber and the power feeding method of the high frequency heating device. For example, the amount of high-frequency leakage from the free end side of the door hinged to the main body tends to be relatively large. However, since all of the four sides of the choke structure on the entire periphery of the door have slits at the same period, the amount of high frequency leakage from each part of the door outer periphery cannot be controlled relatively, and the amount of high frequency leakage is averaged. The value could not be reduced.

  The technical problem of the present invention is to make it possible to relatively control the amount of high-frequency leakage from each part of the door outer periphery.

  The high-frequency heating device according to the present invention has the following configuration. That is, a main body comprising a casing provided with a rectangular opening on the front surface and having a heating chamber in which a high frequency is supplied inside, and a frame-shaped opening sheet metal on the periphery of the rectangular opening; A bag-like comb that is attached to the main body via a hinge so as to freely open and close the rectangular opening, and periodically slits are formed in a portion facing the opening sheet metal to prevent radio wave leakage over the entire circumference. A high-frequency heating apparatus including a door provided with a toothed choke structure, and the arrangement period of at least one choke structure slit among the four sides of the choke structure around the entire door, and the remaining choke structure The slit arrangement period is different from each other.

  According to the high-frequency heating device of the present invention, among the four sides of the choke structure around the entire periphery of the door, the arrangement period of the slits of the choke structure of at least one side is different from the arrangement period of the slits of the choke structure of the remaining side. Therefore, the amount of leakage from each part of the door outer periphery can be controlled relatively, and the amount of high-frequency leakage can be reduced by looking at the average value.

First, the operation principle of the choke structure will be described before describing the embodiment of the present invention.
FIG. 1 is a main part showing the relationship between a peripheral part of a door having a choke structure of a high-frequency heating device and a peripheral part of a main body rectangular opening facing the door peripheral part (hereinafter referred to as “opening sheet metal”). FIG. 2 is a longitudinal sectional view of a main part showing the choke structure of the door, FIG. 3 is a rear view showing the choke structure at one corner of the door, and FIG. 4 is a perspective view showing a corner part in the choke structure on one side. 5 and 6 are schematic views showing high-frequency propagation paths in the choke, and FIG. 7 is a graph showing a comparison of the difference in the amount of high-frequency leakage depending on whether or not the choke is slit.

  The high-frequency heating device includes a main body 2 including a casing having a heating chamber 1 in which a rectangular opening 1a is provided on the front surface and a high frequency is supplied therein, and the heating chamber attached to the main body 2 via a hinge. And a door 3 that freely opens and closes the rectangular opening 1a, and a high frequency wave oscillated from a magnetron (not shown) is propagated into the heating chamber 1 through a waveguide, whereby an object to be heated in the heating chamber 1 is heated. Can be heated. The waveguide is installed at the bottom of the heating chamber, for example, and a rotating antenna (not shown) that has a rotation axis and diffuses high frequency into the heating chamber 1 is provided inside the waveguide. There is also.

  A frame-shaped opening sheet metal 2a is provided in the periphery of the rectangular opening 1a of the main body 2, and slits 10 are periodically formed in the periphery on the door 3 side facing the opening sheet metal 2a. A choke structure 4 composed of a comb-like shape having a cover path is provided over the entire circumference, and the periphery of the choke structure 4 is covered with a resin cover 5 made of a material that absorbs high frequencies and has a low dielectric loss coefficient. The effect of the resin cover 5 on the choke performance is considered to be small.

  The choke structure 4 is formed by bending the metal plate around the door 3 four times by 90 °. That is, the first bending is bent in the opposite direction with respect to the opening sheet metal 2a of the main body 2, and the subsequent second bending is parallel to the surface of the door 3 and in the outward extension direction of the door 3 (forms an outward flange). The third fold is bent in the direction toward the opening sheet metal 2a of the main body 2, and the fourth fold is continued in parallel to the surface of the door 3 and inward of the door 3 (with an inward flange). It is formed by bending). The surface immediately before the first bending is the door contact surface 4a, and the surface between the first and second bent portions is the choke first surface 4b, and the second bent portion and 3 The surface between the second bent portion and the third bent portion 4c are the second choke surface 4c, and the surface between the third bent portion and the fourth bent portion is the third choke surface 4d. Are formed as the fourth choke surface 4e, and the slit 10 is formed by cutting from the fourth choke surface 4e to a part of the third choke surface 41d. The slits 10 are periodically arranged in the choke longitudinal direction. In addition, a space having an opening dimension W is formed between the tip of the fourth choke surface 4e and the first choke surface 4b.

  A heat resistant inner glass 6 is installed on the inner surface side of the door 3, and a heat resistant outer glass 7 is installed on the outer surface side of the door 3.

  In the high-frequency heating device, the choke structure 4 of the door 3 is configured as described above, and as shown in FIGS. 5 and 6, the leakage is caused from the gap g between the peripheral portion of the door 3 and the opening sheet metal 2 a of the main body 2. The reflected wave from the end portion (point C) of the choke structure 4 of the choke structure 4 is struck against the high frequency to be combined, and the maximum voltage and the minimum current are obtained at the choke entrance (point B), and the apparent impedance is ∞. Thus, the leakage of microwaves from between the door 3 and the main body 2 is eliminated or reduced. That is, the length of the propagation path between the entrance part (point A) of the gap g and the choke entrance part (point B) and the propagation path between the choke entrance part (point B) and the end of the bag path (point C). Each length is set to be about 1/4 of the wavelength used, and at point B, the reflected wave from point C and the high frequency that enters and leaks from point A are combined in opposite phases. It is configured to be.

  Here, the microwave (2.45 GHz) used in the microwave oven has a wavelength of about 122 mm, and a quarter of the wavelength is about 31 mm. Therefore, for example, when it is assumed that the apparent distance (straight line distance) between the choke entrance part (point B) and the end part (point C) of the bag path is the same as the actual propagation path distance, the first bent portion And the dimension between the second bent part (hereinafter referred to as the choke first surface width) U is 21 mm, the dimension between the second bent part and the third bent part (hereinafter referred to as the choke second surface). V (referred to as width) is also 21 mm, so that the length of the propagation path from point B to point C can be reduced to about 31 mm, which is a quarter of the wavelength of the microwave used.

  And the amount of high frequency leakage can be suppressed by comprising the choke structure 4 in the shape of a comb-teeth having a narrow path shape in which slits 10 are periodically formed, as is apparent from the graph of FIG. This means that there is a high frequency propagating in the groove extending direction of the choke, and the high frequency propagating in the groove extending direction can suppress the amount of leakage by the slit 10. As described above, after the principle of operation of the choke structure has been clarified, an embodiment of the present invention will be described.

Embodiment FIG. 8 is a graph showing the results of experiments on the relationship between the slit arrangement period and the amount of high-frequency leakage in the choke structure of the high-frequency heating device according to the embodiment of the present invention, and FIG. Arrangement of slits in the choke structure of the door on the long side (same on the long side of the frame-shaped opening sheet metal) and on the short side of the rectangular opening (same on the short side of the frame-shaped opening sheet metal) It is explanatory drawing which shows the test result of the amount of high frequency leaks (average value) at the time of making a period (same as a comb tooth period) different, and the arrangement | positioning period (comb tooth period) of a slit being the same. Here, in the description, reference will be made to the explanatory diagrams (FIGS. 1 to 7) of the operation principle of the choke structure described above.

  In the high-frequency heating device of the present embodiment, the opening 1a of the main body 2 has a horizontally long rectangle, and the door 3 is hinged to one of the long sides (lower side). As is apparent from FIG. 8, the amount of high frequency leakage varies greatly depending on the arrangement period (comb tooth period) of the slit 10. More preferably, it is possible to suppress the amount of high-frequency leakage around the entire circumference of the opening 1a. However, when considered from the viewpoint of the input energy versus the amount of leakage, the high-frequency reflected to the heating chamber side is input into the heating chamber. This means an increase in energy, and when viewed from the input / output of a single choke, the input may be increased, resulting in an increase in the maximum leakage.

  Therefore, a viewpoint that leaks in a balanced manner from the choke structure 4 on each side of the door 3 is necessary. As is clear from FIG. 9, the gap g between the opening 1a and the side opposite to the door hinge, that is, the choke structure 4 of the door 3 and the opening sheet metal 2a of the main body 2 is the largest and relatively leaks. When the periodic dimension S2 of the slit 10 of the choke structure 4 on the upper side (the long side in this case) is large is 48 mm, and the periodic dimension S1 of the slit 10 on the short side part where the leakage is relatively small is 24 mm, That is, when the slit period S is changed, the high-frequency leakage amount (average value) is reduced, and the maximum leakage amount is effectively suppressed. Such an effect is obtained even when the relationship of the periodic dimension S of the slit 10 is reversed, that is, as shown in FIG. 9, the periodic dimension S1 of the slit 10 of the short side choke structure 4 is 48 mm, and the long side (upper side) ) A similar tendency was observed even when the periodic dimension S2 of the slit 10 of the choke structure 4 was 24 mm.

  That is, as in the high-frequency heating device of this embodiment, among the four sides of the choke structure 4 on the entire periphery of the door, the arrangement period of the slits 10 of the choke structure 4 on at least one side and the slits of the choke structure 4 on the remaining sides By making the arrangement period of 10 different, the amount of high-frequency leakage from each part of the door outer periphery can be relatively controlled, and the amount of high-frequency leakage can be reduced by looking at the average value.

  Further, the effect of suppressing the amount of high-frequency leakage as described above, that is, the effect of being able to relatively control the amount of high-frequency leakage from each part of the outer periphery of the door and reducing the amount of high-frequency leakage in terms of an average value is 4 on the entire circumference of the door. Among the side choke structures, the slit period dimension S1 of the two opposite choke structures is the same, and the remaining two side choke structure slit period S2 is the slit period dimension S1 (for example, 24 mm) of the two opposite choke structures. It was also obtained by setting a longer period (for example, 48 mm).

  Further, the effect of suppressing the amount of high-frequency leakage as described above, that is, the effect of being able to relatively control the amount of high-frequency leakage from each part of the outer periphery of the door and reducing the amount of high-frequency leakage in terms of an average value is apparent from FIG. As described above, the slit period dimension of the choke structure facing the long side (upper and lower sides) side of the frame-shaped opening sheet metal 2a is set to be the same as that of the choke structure facing the short side (left and right side) side of the frame-shaped opening sheet metal 2a. By making it larger than the slit periodic dimension, a greater effect can be obtained.

  Further, as apparent from FIG. 8, the periodic dimension S of the slit 10 of the choke structure 4 has the largest effect of suppressing the amount of high-frequency leakage when it is about 45 mm, and the amount of high-frequency leakage when the periodic dimension S is 5 mm or less or 55 mm or more. It turns out that the inhibitory effect becomes small. Therefore, in selecting the periodic dimension S of the slit 10 of the choke structure 4 on each side, it is necessary to use this range (5 mm to 55 mm).

  More specifically, the periodic dimension S of the slit 10 of the choke structure 4 at a portion where the amount of leakage is relatively large (side opposite to the door hinge) is 30 mm or more and less than 55 mm, preferably about 45 mm. By obtaining the periodic dimension S of the slit 10 of the choke structure 4 in a small amount (left and right sides) of 5 mm or more and less than 30 mm, preferably about 25 mm, the above-described effect of maintaining the balance of the high-frequency leakage amount can be obtained. Can do. That is, the periodic dimension S of the slit 10 of the choke structure 4 is a test result that can reduce the amount of high-frequency leakage as an average value by increasing the periodic dimension on the long side of the frame-shaped opening sheet metal 2a (FIG. 9). However, it is not necessarily determined by the long side and the short side of the frame-shaped opening sheet metal 2a. Here, since the long side (upper side) of the frame-shaped opening sheet metal 2a happens to be a portion with a relatively large leakage amount (side opposite to the door hinge), the choke structure 4 on the upper side (or upper and lower sides). The periodic dimension S of the slit 10 is set to 30 mm or more and less than 55 mm.

  In short, the high-frequency heating device of the present embodiment makes it difficult to leak where high-frequency waves are likely to leak (preferably increase the periodic dimension S of the slit 10), and slightly leaks places where high-frequency waves are difficult to leak (preferably the slit 10). This is intended to reduce (balance) the leakage amount as a whole by reducing the periodic dimension S). This is important.

  As shown in FIGS. 3 and 4, only the comb teeth 40d and 40e at the corners closest to the four corners of the four-side choke structure have a longer tooth width than the other portions. This is because the amount of high-frequency leakage tends to increase at the four corners. Thus, without applying the above-described periodic dimension S, the tooth width dimension of the comb teeth 40d and 40e of the choke structure is increased so that the comb teeth at the tips of the two chalk facing each other with the corners sandwiched therebetween can be made as close as possible. In addition, the effect of suppressing the amount of high-frequency leakage by the choke structure can be obtained up to the end.

It is explanatory drawing of the principle of operation of a choke structure. It is explanatory drawing of the principle of operation of a choke structure. It is explanatory drawing of the principle of operation of a choke structure. It is explanatory drawing of the principle of operation of a choke structure. It is explanatory drawing of the principle of operation of a choke structure. It is explanatory drawing of the principle of operation of a choke structure. It is explanatory drawing of the principle of operation of a choke structure. It is a graph which shows the relationship between the arrangement | positioning period of the slit in the choke structure of the high frequency heating apparatus which concerns on Embodiment 1 of this invention, and high frequency leakage amount. When the arrangement period of the slits in the door choke structure is different between the long side and the short side of the rectangular opening of the high-frequency heating device according to Embodiment 1 of the present invention, the slit arrangement period is the same. It is explanatory drawing which shows the high frequency leakage amount (average value) at the time of doing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating chamber, 1a Rectangular opening part, 2 Main body, 2a Frame-shaped opening sheet metal, 3 Door, 4 Choke structure, 10 Slit, 40d, 40e Square comb teeth.

Claims (6)

A main body comprising a casing provided with a rectangular opening on the front surface and having a heating chamber in which a high frequency is supplied inside, and a frame-shaped opening sheet metal on the periphery of the rectangular opening;
Covered to the main body via a hinge so as to cover the rectangular opening so as to be openable and closable, and in a portion of the bag facing the opening metal plate, a slit is periodically formed to prevent radio wave leakage over the entire circumference. A high-frequency heating device provided with a door provided with a chalk structure composed of comb teeth,
A high-frequency heating apparatus characterized in that, among the four sides of the choke structure on the entire periphery of the door, the arrangement period of the slits of the choke structure of at least one side is different from the arrangement period of the slits of the choke structure of the remaining side.   Among the four sides of the choke structure around the entire door, the slit period dimension S1 of the two opposite choke structures is the same, and the remaining two side choke structure slit period S2 is the slit period of the two opposite choke structures. 2. The high frequency heating device according to claim 1, wherein the cycle is longer than the dimension S1.   The high-frequency heating device according to claim 2, wherein the two-side choke structure in which the slits are arranged with a long period is a choke structure facing the long side of the frame-shaped opening sheet metal.   4. The choke structure having two sides in which the slits are arranged with a long cycle is a choke structure provided on each of the door hinge side and the door free end side, respectively. The high-frequency heating device described.   5. The high-frequency heating device according to claim 2, wherein the slits are arranged at a cycle having a long cycle of 30 mm or more and less than 55 mm and a short cycle of 5 mm or more and less than 30 mm. The high frequency heating device according to any one of claims 1 to 5, wherein only the comb teeth closest to the four corners of the four-side choke structure have a tooth width dimension longer than that of other portions. .

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