JP5593722B2 - Microwave heating cooker - Google Patents

Description

  The present invention relates to a microwave heating cooker that performs dielectric heating by radiating microwaves to an object to be heated.

  A microwave oven, which is a typical microwave heating cooker, can directly heat food that is a typical object to be heated, and it is not necessary to prepare a pan or pot, making it an indispensable cooking tool in daily life. It has become. In recent years, products having a heating chamber having a shape in which the bottom surface of the heating chamber space for storing food is flat have been put into practical use so that a plurality of dishes can be arranged and heated.

  In this case, the radiating means for radiating the microwave into the cabinet may be a flat surface on the bottom made of a microwave transmitting material such as ceramic and disposed further below, or disposed on the ceiling surface side. Although it is conceivable, in order to efficiently heat the food, it is better to radiate microwaves from the vicinity of the food as much as possible.

  Further, the entire heating chamber is covered with a conductor by, for example, forming a wall surface with a conductor so as not to leak the microwave in the heating chamber to the outside. However, it is generally known that, for example, a punching hole is provided on the wall surface of a conductor to allow wind or light to pass through because the microwave cannot pass if the hole is smaller than the wavelength of the microwave.

  In addition, many microwave ovens have an oven function and a grill function. The oven function is called hot air circulation or convection that circulates the warmed air using a heater. The oven temperature is maintained at a high temperature (for example, 200 ° C), and foods such as cakes and cookies are carefully baked. It is a function.

  In this case, the tray on which the food is placed must be made of a heat-resistant material because the temperature inside the box becomes high. Possible materials are conductors such as iron, aluminum and stainless steel, or dielectrics such as ceramic and heat-resistant glass.

  Since mechanical strength (being difficult to break when dropped or hit) is also required as a requirement other than heat resistance, it must be made thicker (heavy) to ensure mechanical strength for ceramics and heat-resistant glass. The heat capacity becomes large.

  When the heat capacity is large, particularly immediately after the start of heating, much of the heat that is desired to be supplied to the food is also taken into the tray, and the temperature rise as a whole in the cabinet is delayed, and there is a problem that it takes a long heating time. Therefore, in order to shorten the heating time as much as possible, it is preferable to use a conductor tray that has a mechanical strength even if it is thin, and as a result, a heat capacity is small.

  The grill function is a function that arranges food near the heater and burns the surface with radiant heat, which is suitable for grilling meat and fish. The heater includes a tube type such as a miraclon heater, a halogen heater, and a sheathed heater, and a planar type such as a mica heater, and is often arranged close to the upper or lower surface of the food.

Depending on the purpose, only the upper surface of the food may be baked or only the lower surface may be baked, but recently, in order to simmer and burn quickly at the same time in both the upper and lower sides, the use of a microwave-absorbing heating element in addition to the above-mentioned heater is increasing. A microwave-absorbing heating element is integrated with the bottom surface of the tray on which food is placed, absorbs the microwaves emitted from the lower side, transfers heat generated to the tray, and heats the food by the heat from the tray when the tray itself is at a high temperature. The lower side can be baked.

  The merit of this method is in combination with a heater that burns the upper surface. By attaching the tray to the upper part of the chamber, food can be brought closer to the upper heater, the upper surface can be baked efficiently, and the lower surface can be baked directly by the heat of the tray in contact with the food .

  Therefore, even in the case of a heating chamber having a large internal volume, if the tray is mounted on the upper side, the upper surface and the lower surface can be simultaneously baked by a heating element close to each other, and the baking can be performed quickly. Here, as described in the description of the oven function, the tray material is preferably a conductor tray in order to shorten the heating time as much as possible in terms of heat resistance, mechanical strength, and heat capacity.

  On the other hand, the use of frozen foods is increasing for recent foods. Many commercial frozen foods are also being supplied, and the opportunity to freeze foods using a freezer is increasing at home. If you want to bake frozen foods in an oven or grill, you can bake them as they are, but once the size is large, it is a two-step process: thaw once and bake.

  Because ovens and grills bake foods by heat conduction from the surroundings, there is a possibility that even if the surface is burnt, heat is not transmitted to the inside and it is frozen. On the other hand, a microwave oven is generally known as a cooker suitable for thawing in a short time because microwaves penetrate into the food and heat it.

  Therefore, in order to bake frozen foods in an oven or grill, it is conceivable to combine microwaves. However, as described above, when the radiation means is formed below the flat surface and the tray is made of a conductor, the microwave is reflected by the conductor and cannot be supplied to the food on the conductor.

  Therefore, it is conceivable to make a hole in the tray, or to provide a gap between the tray and the wall of the heating chamber. However, if a large hole or gap is unnecessarily provided, the food placement area on the tray will be narrowed and food placed on the tray. Therefore, there is a demand for a method in which the central portion of the tray is the same size as before and a hole is made in the edge of the tray, or the edge is made as narrow as possible to increase the gap with the wall surface.

  However, even if the prior art is examined, there has not been much study on how the microwaves can be passed efficiently by specifically configuring the holes and gaps.

  Among the prior arts, for example, as disclosed in Patent Document 1, there is a description of conductor tray holes having different purposes, and the contents thereof will be described below. 14 to 16 are configuration diagrams of Patent Document 1, FIG. 14 is a schematic perspective view of a heating chamber, FIG. 15 is a configuration diagram of one tray, and FIG. 16 is a configuration diagram of another proposal of the tray. is there.

  Although it is a turntable system in which food is rotated instead of a flat bottom surface, a method for allowing a microwave to pass through a hole in a tray (turntable) made of a conductor has been proposed. The conductor tray 1 has a large number of holes, a glass dish 2 is mounted on the top of the tray 1 and food 3 is placed thereon, and the microwave radiation means is a right wall surface 5 made of a conductor of the heating chamber 4. It is configured as a radiation port 6.

Although not shown, a magnetron of a typical microwave generating means is connected to the radiation port 6 via a waveguide, and the microwave generated from the magnetron is radiated from the radiation port 6 into the chamber. The tray 1 is rotated around the rotating shaft 7 in order to prevent the food 3 from being heated unevenly, but a passage hole through which microwaves can pass is provided in the tray 1 for further uniform heating.

  One proposal is shown in FIG. The tray 31 is obtained by performing enamel treatment on the surface of a conductive material such as a steel plate, and has an overall outer shape of a circular flat dish and a non-homogeneous shape (a point-symmetric shape with respect to the center point) in the rotation direction. Specifically, the rotating plate 31 is configured in a lattice shape integrally including a plurality of vertical bars 31b and a plurality of horizontal bars 31c orthogonal thereto in an annular peripheral frame 31a.

  A boss portion 31d connected to the rotating shaft 10 (see FIG. 14) is provided at the center portion. At this time, a plurality of approximately square passage holes 32 (four to surround the boss portion 31d and two in front and behind the total 6) are formed in the center of the rotating plate 31 from the vertical bar 31b and the horizontal bar 31c. Formed).

  The passage holes 32 have both vertical and horizontal dimensions c that are not less than ¼ of the wavelength λ of the microwaves, so that the microwaves can easily pass through. In the portion near the outer periphery of the rotating plate 31 (left and right portions in the drawing of the passage hole 32 formation portion), several rectangular passage holes 31e elongated in the vertical direction in the figure are formed with substantially the same dimensions.

  Since the longitudinal dimension a is λ / 2 or more (for example, 64 mm), the passage hole 31e can easily pass microwaves, and even if the lateral dimension b is less than λ / 4 (for example, 30 mm), the microwaves can pass sufficiently. It is supposed to be possible. FIG. 16 shows the configuration of the tray 41 as another proposal.

  The tray 41 in this example has a shape in which a hub portion 41a at the center and an annular peripheral frame (rim portion) 41b are connected by an arm portion 41c. At this time, three arm portions 41c are provided radially at intervals of 120 degrees, and therefore the tray 41 has the same original shape when rotated 120 degrees (360 degrees / n; n = 3). It has a rotationally symmetric shape.

  In the tray 41, a fan-shaped passage hole 41e is formed between the arm portions 41c. The maximum linear dimension e of the passage hole 41e is a dimension that is 1/2 or more of the microwave wavelength λ. As a result, microwaves can be transmitted.

  As described above, Patent Document 1 describes that microwaves are difficult to pass if the longest dimension of the hole is less than λ / 4, pass if it is greater than λ / 4, and pass more easily if it is greater than λ / 2. That is.

  Each example has a hole through which microwaves can pass, but the purpose is to change the electric field distribution by changing the position of the hole by rotation. That is, in addition to changing the position of the food by rotating the tray in order to prevent uneven heating, the microwave distribution itself is changed by moving a passage hole through which the microwave can pass.

Japanese Patent No. 3901350

  However, in the conventional microwave heating cooker as described in Patent Document 1, there is no mention of what happens to the microwave that has passed through the passage hole provided in the conductor tray.

  There is no food or other object to be heated under the tray, so it is not expected to heat anything with microwaves that have passed through the passage hole. It may return to the tray from the hole, or may return to the tray from the periphery of the tray. Any route may be used, so long as the microwave finally returns to the tray and the food 3 can be heated.

  On the other hand, the problem of the present invention will be described. In the range where the tray of the conductor does not impair the function of the tray (a method of providing a passage hole at the edge of the tray), microwaves are supplied to the food on the opposite side of the conductor through the passage hole, how efficiently Although it is a big subject whether it heats, patent document 1 etc. have no description.

  Experiments with several through-holes through which microwaves can actually pass reveal that heating efficiency is often poor and varies greatly depending on how the through-holes are selected. For example, it is known that the heating efficiency of a microwave oven measured by, for example, the IEC method (= water absorption power / input when the object to be heated is water) is generally about 50%. It was found that when water is placed on a tray having a passage hole through which microwaves can pass at the edge, it varies greatly from about 10% to about 30% depending on how the passage hole is selected.

  Accordingly, an object of the present invention is to supply microwaves to an object to be heated on a tray as efficiently as possible using a tray having a passage hole through which microwaves can pass at the edge of a conductor.

In order to solve the above-described conventional problems, a microwave heating cooker according to the present invention includes a heating chamber covered with a conductor, radiating means for supplying microwaves to the heating chamber, and an edge. removably provided in the heating chamber to the outer peripheral parts in proximity with the wall surface of the heating chamber, passage for passing the tray made of conductors dividing, the provided before Kien unit microwave the heating chamber A first microwave that passes through the passage hole and a second microwave that wraps around from the outer periphery of the edge are in opposite phases on the tray. And having a shielding portion for preventing them from canceling each other out .

  With the above configuration, it is possible to prevent the microwave passing through the passage hole and the microwave that circulates from the outer periphery of the edge from being reversed in phase on the tray and canceling each other out, and efficiently supplying the microwave onto the tray. it can.

  The microwave heating cooker according to the present invention prevents the microwave passing through the passage hole and the microwave that circulates from the outer periphery of the edge from being reversed in phase on the tray and canceling each other out efficiently. Can supply waves.

The perspective view which shows the internal structure of the microwave oven which is a microwave heating cooker which concerns on 1st embodiment of this invention, and the flow of a microwave Front sectional view of the microwave oven of FIG. The figure which shows the AA cross section and external structure of the microwave oven of FIG. Explanatory drawing which shows the positional relationship of the tray and radiation | emission means of the microwave oven of FIG. The characteristic figure which shows the phase of the microwave which passed two passage holes of the microwave oven of FIG. The perspective view which shows the other microwave flow of the microwave oven of FIG. Front sectional drawing of the microwave oven which is a microwave heating cooking appliance which concerns on 2nd embodiment of this invention The figure which shows the AA cross section and external structure of the microwave oven of FIG. Explanatory drawing which shows the positional relationship of the tray and radiation | emission means of the microwave oven of FIG. BB cross section of the tray of FIG. The block diagram of the circular passage hole of the tray which concerns on 3rd embodiment of this invention The block diagram of the polygonal passage hole of the tray which concerns on 4th embodiment of this invention The block diagram of the passage hole of the corner part of the tray which concerns on 5th embodiment of this invention The perspective view which shows the internal structure of the microwave oven which is the conventional microwave heating cooker FIG. 14 is a block diagram of a draft of the microwave oven tray of FIG. 14 is a configuration diagram of another plan of the tray of the microwave oven of FIG.

(Embodiment 1)
Below, with reference to FIGS. 1-6, the microwave oven is demonstrated about the microwave heating cooker which concerns on embodiment of this invention as an example.

  FIG. 1 is a perspective view of the interior as viewed from the front, showing the internal structure of the microwave oven and the flow of microwaves, FIG. 2 is a cross-sectional view seen from the front, and FIG. 3 is a cross-sectional view taken along the line AA in FIG. 4 is a diagram of the tray viewed from directly above, illustrating the positional relationship between the tray and the radiation means, FIG. 5 is a characteristic diagram illustrating the phase of the microwaves that have passed through the two passage holes, and FIG. It is a figure which shows the flow of a different microwave.

  The heating chamber 51 is integrated with the wall surface of the conductor except for the front. Since the conductor 53 inside the door 52 faces the front, the entire heating chamber is covered with the conductor. The radiating means 54 for supplying microwaves into the heating chamber is below the plate 55 made of a dielectric material such as ceramic or glass, and when the user looks inside the chamber, the plate 55 makes the bottom surface look flat.

  The radiating means 54 guides the microwave radiated from the magnetron 56 as a typical microwave generating means to the bottom surface of the heating chamber via the waveguide 57, and enters the inside through the rotating antenna 58 disposed on the bottom surface of the heating chamber. Microwaves are radiated.

  A rotating antenna 58, which is a typical rotating body that stirs microwaves, has microwave radiation directivity in a specific direction (in the direction of the arrow in the figure), and is controlled based on the setting contents of the setting means 59. The means 60 controls the driving means 61 to freely control the direction of the rotating antenna. It can be rotated or stopped in a predetermined orientation. The control means 60 also controls the heater 63 and the fan 64 of the convection 62.

  The tray 65 is made of a conductor and has a hollow surface. The tray 65 has a peripheral edge 66 that is one step higher, and has a slit-shaped passage hole 67 through which microwaves pass. Here, the wavelength λ of the microwave in the air is expressed as λ = C / f, C is the speed of light (3.0 × 10 8 [m / s]), and f is the frequency (about 2 in the microwave oven). .45 [GHz]), the wavelength λ is about 120 mm. The slit shape has a length of 55 mm, which is approximately 90% of ½ of the wavelength, and a width of about 6 mm which is less than ¼ of the wavelength.

  When the tray 65 is mounted in the heating chamber 51, the food 68 to be heated is placed on the tray 65, and the tray 65 is placed on one of the rails 69A, 69B, 69C on the heating chamber wall surface. It is attached to the rail 69B. As a result, the outer periphery 70 of the tray 65 comes close to the wall surface of the heating chamber 51 made of a conductor and the conductor 53 of the door 52, and the heating chamber 51 is divided up and down by the tray 65.

The wall surface of the heating chamber 51 is processed with fluorine, and since the conductor of the tray 65 and the wall surface conductor are insulated by the enamel on the surface of the tray 65 and the fluorine on the surface of the wall surface, a slight amount of microwave can pass therethrough. The interval between the passage hole 67 and the outer periphery 70 is 35 mm and is larger than 30 mm, which is 1/4 of the wavelength of the microwave.

  Hereinafter, the conductor portion between the passage hole 67 and the outer periphery 70 will be referred to as a shielding portion 71 for convenience.

  The rotating antenna of the radiating means is arranged at the center of the left and right in the cabinet, and the passage hole 67 of the tray 65 is arranged only on one side before the edge 66 as shown in FIG.

  In the present embodiment, matching is performed by optimizing the rotating antenna 58, the waveguide 57, etc. so that the efficiency increases when the direction in which the rotating antenna 58 has a strong directivity is directed to the passage hole 67 as shown in FIG. I am letting.

  With the above configuration, the microwave heating cooker of the present embodiment includes the heating chamber 51 covered with a conductor, the radiating means 54 for supplying the microwave into the heating chamber 51, and the edge 66. An outer periphery 70 of the edge portion 66 is provided so as to be detachable from the heating chamber 51 in the vicinity of the wall surface of the heating chamber 51. The conductor tray 65 that divides the heating chamber 51 and the outer periphery 70 of the edge portion 66 The edge portion 66 is provided with an interval larger than ¼ of the wavelength of the microwave, and a passage hole 67 for allowing the microwave to pass therethrough is provided.

  The microwave radiated from the rotating antenna 58 of the radiating means is not only the passage hole 67 but also the outer periphery 70 of the edge 66 and the wall surface of the heating chamber 51 are close to each other. It is transmitted above the tray 65.

  At this time, it was found that when the distance between the passage hole 67 and the outer periphery 70 is short, the transmission is not so much, and when the distance is more than a certain distance, the transmission is easy. Speaking of the heating efficiency when water was placed on the tray 65, it was only 10% when the distance was short, but improved to 30% when the distance was increased. This is considered to be caused by a change at a distance of about ¼ of the wavelength λ.

  Consider the reason. As shown in FIG. 5, the microwave is a sine wave, and the wavelength λ is about 120 mm as described above. Considering a specific position α, the amplitude only increases or decreases in time, but if the position is shifted with respect to the transmission direction, the phase changes even if the amplitude is the same. For example, the phase is completely reversed at a position β separated by a half wavelength (λ / 2), and the phase is the same at a position γ separated by one wavelength (λ). This is repeated as a function of wavelength, even at distances.

  This is applied to FIG. When the microwave radiated from the radiating means 54 is divided into two in front of the gap between the left wall surface and the tray 65 and becomes an arrow line 72 and an arrow line 73, when attention is paid to the phase of the microwave at the point 74 When the phase at the point 74 of the microwave of the arrow 72 is a reference (phase 0 degree, corresponding to α in FIG. 5), the microwave of the arrow 73 reciprocates the distance to the passage hole 67, and thus the phase However, if the distance to the passage hole 67 is exactly λ / 4, a reciprocal shift of λ / 2 occurs, that is, the phase is 90 degrees, which corresponds to β in FIG.

  At this time, since the microwaves of the arrow line 72 and the arrow line 73 overlap at the point 74, the sine waves having opposite phases are combined, and when both amplitudes are the same, the amplitude of the combined wave is completely zero. That is, microwaves are not transmitted.

  When the distance to the passage hole 67 is shorter, it seems that it does not happen for a moment, but since the passage hole 67 has a certain size, the distance becomes λ / 4 depending on where the passage hole passes. This can happen enough and the microwaves may not be transmitted.

  On the other hand, if the distance to the passage hole 67 is arranged apart from λ / 4 as in the present embodiment, at least the relationship between α and β in FIG. 5 does not occur and the microwave is canceled out. Nothing happens that is not transmitted.

  Strictly speaking, when the distance is further increased, the round trip distance may be canceled if it becomes an odd multiple of λ / 2, such as 3 × λ / 2, 5 × λ / 2, etc. Is said to diffuse in various directions, and it is thought that the rate at which microwaves directed to distant passage holes return to their original positions is extremely small, that is, the closest condition (round trip distance) It is thought that if only λ / 2) is removed, the efficiency is sufficiently improved.

  Incidentally, FIG. 6 is a diagram in which the right passage hole 67 is considered as a reference contrary to FIG. 1, but the same thing occurs, that is, if the gap and the passage from one of the passage holes are obstructed. The passage from the other side is also inhibited.

  As described above, the passage hole 67 is arranged at a distance larger than ¼ of the wavelength of the microwave from the outer periphery 70 of the tray 65, so that the microwave passing through the gap between the wall surface and the outer periphery passes through the passage hole 67. Therefore, it is possible to prevent the microwaves that are in reverse phase on the tray 65 from canceling each other and efficiently supply the microwaves onto the tray 65.

  In the present embodiment, the microwave is supplied onto the tray 65 by setting the length of the longest portion of the passage hole 67 to ¼ or more of the wavelength. In particular, the passage hole 67 has a substantially slit shape and has the longest length. The length of the portion is 55 mm which is approximately 90% of ½ of the wavelength, and the width is 6 mm which is less than ¼ of the wavelength. In order to pass microwaves, it was thought that ¼ or more of the wavelength and particularly ½ or more of the wavelength was desirable, but it was found that sufficient supply was possible if it was about 90% or more of ½ of the wavelength. .

  Since the rotating antenna 58 of the rotating body having microwave radiation directivity in a specific direction and the control means 60 for controlling the stop and rotation of the rotating antenna 58 are provided, heating can be appropriately performed according to the purpose.

  For example, since the tray 65 is not mounted when performing normal warming or the like, the rotating antenna 58 is rotated and heated uniformly. However, when the oven is cooked, the tray 65 is mounted, so the rotating antenna 58 is used as a passage hole. It is possible to perform control such as stopping the vehicle.

  In particular, if the direction 75 having a strong radiation directivity is directed to the passage hole 67 during the rotation of the rotary antenna 58 (FIG. 4), it is controlled so as to be stopped or decelerated (the passage hole 67). Since the rotation antenna 58, the waveguide 57, and the like are optimized and matched (so that the transmission of microwaves from is increased), the efficiency is surely increased.

  The longest portion of the passage hole 67 is arranged toward the radiating means, and the transmitted microwave can be effectively passed even if the width of the passage hole 67 is narrow.

  The outer periphery 70 of the edge portion 66 and the wall surface of the heating chamber 51 are respectively subjected to an insulating coating so that an insulator is interposed between them, and microwaves can pass between the outer periphery 70 and the wall surface. Of course, only one side of the coating may be necessary.

(Embodiment 2)
With reference to FIGS. 7-10, the microwave heating cooker which concerns on Embodiment 2 of this invention is demonstrated using a microwave oven as an example.

7 is a cross-sectional view seen from the front, FIG. 8 is a cross-sectional view taken along the line AA of FIG. 7, FIG. 9 is a view seen from directly above the tray, and is an explanatory view showing the positional relationship between the tray and the radiating means. It is BB sectional drawing of the tray of FIG.

  The present embodiment is different from the first embodiment in that three tubular heaters 76A, 76B, and 76C are arranged on the top surface of the interior in order to provide a grill function instead of the oven function. is there. The control means 60 also controls energization of the tubular heaters 76A, 76B, and 76C.

  In order to improve the grill function, the tray 77 is attached to the upper rail 69A, and the upper surface of the food 68 is quickly baked close to the tubular heaters 76A, 76B, 76C.

  On the other hand, in order to bake the lower surface of the food, a microwave absorption heating element 78 is integrated with the lower surface of the tray 77. The passage holes 79A and 79B are disposed on two opposite sides of the left and right edges, and have a cover 80 made of a dielectric material such as PPS so as to close the passage holes 79A and 79B.

  The cover 80 not only has the effect of improving the safety so that the end surfaces of the passage holes 79A and 79B are not exposed, but the dielectric is equivalent to the insulator, so that the cover 80 is interposed between the tray 77 and the wall surface of the heating chamber 51. This has the effect of increasing the gap (insulating distance) and simultaneously compressing the wavelength of the microwave passing through the passage hole.

  As described above, the wavelength λ of the microwave in the air is λ = C / f, but the wavelength λ of the microwave in the dielectric having the relative permittivity ε is λ = λ0 / √ where the wavelength in the air is λ0. It is compressed to ε.

  Therefore, when the relative dielectric constant of the cover 80 is, for example, 2, the minimum dimension of the passage hole through which the microwave can pass is λ0 / (4√2) or more, and in air, the minimum dimension is 30 mm or more, but 21 mm or more is acceptable. . Therefore, in this embodiment, the longest dimension of the passage holes 79A and 79B is selected to be 28 mm.

  As described above, according to the present invention, the through holes 79A and 79B have the dielectric cover 80 having the relative dielectric constant ε, and the length of the longest portion of the through holes 79A and 79B is 1 / (4√ε ) By the above, microwaves can be supplied onto the tray 77.

  In addition, the longest portions of the passage holes 79A and 79B are arranged toward the radiating means, and the transmitted microwaves can be effectively passed even if the widths of the passage holes 79A and 79B are narrow.

  Further, the outer shape of the edge portion is substantially rectangular, and the plurality of passage holes 79A and 79B are arranged on the two opposite sides of the edge portion 66. Since the positions of 79A and 79B do not change, there is no problem due to incorrect insertion.

  Control is made to stop or decelerate when the direction 75 with strong radiation directivity faces the passage holes 79A and 79B during the rotation, so that the efficiency is increased in this direction in advance (the microwaves from both passage holes 79A and 79B). If the rotation antenna 58, the waveguide 57, and the like are optimized and matched, the efficiency is surely increased.

  In particular, if the direction 75 having a strong radiation directivity is controlled to stop or decelerate sequentially when the direction 75 having a strong radiation directivity faces the plurality of passage holes 79A and 79B during the rotation, the microwave distribution on the tray 77 may be symmetrical. It is predicted and the effect of distribution improvement can be expected compared with the case of only one place.

In particular, in the present embodiment, the first mode in which the microwave is concentrated on the microwave absorption heating element 78 and the second mode in which the microwave is transmitted to the passage holes 79A and 79B depending on the direction of the rotating antenna 58. Have For example, as shown in FIG. 9, the rotating antenna 58 and the waveguide are in the second mode when the rotating antenna faces the passage holes 79A and 79B, and unlike the case in FIG. This can be achieved by optimizing 57 and the like.

  When the food is a frozen product, it is possible to control by first thawing with microwaves in the second mode, switching to the first mode after the food has been thawed to some extent, and baking from the bottom. By controlling in this way, delicious grill cooking can be performed in a short time.

Further, since the longest portion of the passage hole is arranged in parallel with the outer periphery 70, the distance between the outer periphery 70 and the passage holes 79A and 79B can be kept constant, and the microwave can be stably supplied onto the tray. .
Since an insulating cover is attached to the outer periphery 70 of the edge, a wide gap can be ensured reliably.
A configuration in which an insulator is attached to the wall surface of the heating chamber is also conceivable.

  Note that, by curling the outer periphery 70 of the tray 77 as shown in FIG. 10, it is considered that the distance between the passage hole 79B and the outer periphery 70 is longer on the lower side than on the upper side. Considering this, there is a possibility that the distance can be shortened a little more.

(Embodiment 3)
FIG. 11 is a configuration diagram of the circular passage hole 81 of the tray according to the third embodiment of the present invention. The passage hole 81 is substantially circular and has a diameter of 35 mm, which is 1/4 or more of the wavelength. In the case of a circle, microwaves from any direction can be passed through equally. If it is an ellipse, it can pass if it is configured so that the major axis is ¼ or more of the wavelength.

(Embodiment 4)
FIG. 12 is a configuration diagram of the polygonal passage hole 82 of the tray according to the fourth embodiment of the present invention. The passage hole 82 is substantially octagonal, and the distance between the longest opposite sides is 40 mm, which is 1/4 or more of the wavelength.

(Embodiment 5)
FIG. 13 is a configuration diagram of the passage hole 84 of the corner portion 83 of the tray according to the fifth embodiment of the present invention. By selecting the diameter and arrangement of the passage hole 84 along the R of the corner portion 83 of the edge portion 66, the distance between the outer periphery and the passage hole can be made constant from any point of view. Can supply waves.

  As mentioned above, although embodiment was described in detail about this invention, the hole of the grade which cannot pass may be in the conductor part (shielding part 73) between several through-holes.

  Furthermore, food may be placed on the tray and below the tray for simultaneous upper and lower two-stage cooking, and in the case of a plurality of passage holes, different shapes may be combined.

  In the case of a plurality of through holes, the number of the plurality of through holes is not limited to two, and there may be many.

  Although the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

  INDUSTRIAL APPLICABILITY The present invention can be used for a microwave heating apparatus such as a microwave oven that performs heater heating in conjunction with thawing.

51 Heating chamber 54 Radiating means 58 Rotating antenna 60 Control means 65, 77 Tray 66 Edge 67, 79a, 79b, 81, 82, 84 Passing hole 70 Outer circumference 75 Direction with strong radiation directivity 80a, 80b Cover (dielectric, insulation) body)

Claims (13)

A heating chamber covered with a conductor;
Radiation means for supplying microwaves into the heating chamber;
A conductive tray that divides the heating chamber, and has an edge, and is provided detachably in the heating chamber with the outer periphery of the edge close to the wall surface of the heating chamber ;
And a passage hole for passing the provided before Kien portion microwaves,
Between the edge and the passage hole, the first microwave passing through the passage hole and the second microwave that wraps around from the outer periphery of the edge are opposite in phase on the tray and cancel each other out. A microwave heating cooker with a shielding part to prevent this . The microwave heating cooker according to claim 1, wherein the length of the longest portion of the passage hole is ¼ or more of the wavelength. The microwave heating cooker according to claim 2, wherein the passage hole has a substantially slit shape, wherein the length of the longest portion is approximately 90% or more of ½ of the wavelength and the width is less than ¼ of the wavelength. The microwave heating cooker according to claim 2, wherein the passage hole has a substantially circular shape and has a diameter of ¼ or more of the wavelength. The microwave heating cooker according to claim 2, wherein the passage hole is substantially polygonal, and the distance between the longest opposite side is ¼ or more of the wavelength. The microwave heating cooker according to claim 1, wherein the passage hole has a dielectric having a dielectric constant ε, and the length of the longest portion of the passage hole is 1 / (4√ε) or more of the wavelength. The microwave heating cooker according to claim 1, wherein the longest portion of the passage hole is arranged facing the radiation means. The microwave heating cooker according to claim 1, wherein the longest portion of the passage hole is arranged in parallel with the outer periphery. The microwave heating cooker according to claim 1, wherein the radiating means includes a rotating body having a microwave radiation directivity in a specific direction and a control means for controlling stop and rotation of the rotating body. The microwave heating cooker according to claim 9, wherein the control means controls to stop or decelerate when the direction of strong radiation directivity faces the passage hole during the rotation of the rotating body. The microwave heating cooker according to claim 1, wherein an insulator is interposed between the outer periphery of the edge and the wall surface of the heating chamber so that microwaves can pass between the outer periphery and the wall surface. The microwave heating cooker according to claim 11, wherein at least one of the outer periphery of the edge and the wall surface of the heating chamber is subjected to an insulating coating. The microwave heating cooker according to claim 11, wherein an insulator is attached to at least one of the outer periphery of the edge or the wall surface of the heating chamber.