Heating Regulator

Abstract

To provide a cooker having high microwave leakage performance.SOLUTION: A choke groove 24 comprises: a blocking wall surface nearly parallel to a bottom surface, and covering a portion of an opening part; and a folded part 26 extending nearly perpendicularly to the blocking wall surface from the blocking wall surface toward the inside of the choke groove 24. A height dimension H1 of a folded part 26A provided in the choke groove 24 in an upper side part 4p of a handle 4a of a door 4 is made lower than a height dimension H2 of a folded part 26B provided in the choke groove 24 in other sides (a lower side part 4q, a left side part, and a right side part) of the door 4.SELECTED DRAWING: Figure 8A

Description

[Technical Field]

[0001] The present invention relates to a cooking device. [Background technology]

[0002] Heating devices that use microwaves are widely used, such as microwave ovens. If microwaves leak from a heating device that uses microwaves to the outside, it can cause unintended heating of objects and interference with radio wave communications. Therefore, when the door is closed, the power density of the leaked radio waves from the microwave device is set at 1 mW / cm2 at a position 5 cm from the surface of the device when the door is closed, as required by law. 2 Below, when the door is half open (the microwave is left open until it is almost fully operational), it is 5mW / cm 2 It is stipulated that the following must be done:

[0003] A conventional microwave oven described in Patent Document 1 has a choke structure in the microwave door to prevent microwave leakage. This type of choke structure for preventing microwave leakage has a multi-stage structure with different choke groove widths, conductor widths, and effective dielectric constants, and the choke groove depth is smaller than a quarter wavelength (see, for example, Patent Document 1). This technology uses multi-stage values ​​for the characteristic impedance of microwaves entering the choke in the propagation direction, with smaller values ​​on the opening side and larger values ​​on the termination side. This inverts the impedance at a distance shorter than a quarter wavelength, making the impedance on the opening side infinite, and acts as a choke. Leaked waves incident perpendicularly toward the choke groove are blocked by the action of this choke. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-178942 Summary of the Invention [Problem to be solved by the invention]

[0005] However, while a typical choke structure such as that described in Patent Document 1 has high wave leakage shielding performance against microwaves that are incident perpendicularly toward the choke groove, the choke structure alone does not provide sufficient wave leakage shielding performance against microwaves that are incident obliquely toward the choke groove, posing the problem that it is necessary to provide an additional wave leakage suppression mechanism. [Means for solving the problem]

[0006] The present invention is characterized in that it comprises a heat source that heats an object to be heated by high frequency waves, a main body having a heating chamber in which the object to be heated is stored, and an openable and closable door provided in front of the heating chamber, the door having a choke structure portion formed by bending a metal plate multiple times around the outer periphery of the door, the choke structure portion having a bottom surface facing the main body, side surfaces extending from both ends of the bottom surface towards the main body, and a choke groove having an opening facing the main body, the choke groove being arranged along the outer periphery of the door, the choke groove having a closed wall surface that is substantially parallel to the bottom surface and covers part of the opening, and a folded portion that extends from the closed wall surface towards the inside of the choke groove substantially perpendicular to the closed wall surface, and the height dimension of the folded portion provided in the choke groove on an edge of the door where a handle is located is lower than the height dimension of the folded portion provided in the choke groove on the other edge of the door. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a perspective view of the appearance of a cooking device according to an embodiment of the present invention, as viewed from the front side. [Figure 2] 2 is a cross-sectional view taken along the line AA in FIG. 1. [Figure 3] FIG. 2 is a perspective view of a door unit of the cooking device of the present embodiment. [Figure 4] FIG. 3 is an enlarged view of the X portion of FIG. 2. [Figure 5A] 10 is a graph showing an example of analysis of leakage wave shielding performance versus frequency using conventional choke grooves. [Figure 5B]10 is a graph showing an example of an analysis of leakage shielding performance with respect to the angle of incidence of a leakage wave incident on a choke groove. [Figure 6] 10 is an explanatory diagram showing the positional relationship between the door base and the frame portion when the incident angle of the leaked wave is changed. FIG. [Figure 7] 10 is a graph showing an example of an analysis of leakage shielding performance with respect to changes in dimensions of the folded portion of the choke groove. [Figure 8A] 10 is a schematic diagram showing the choke structure of the upper and lower sides based on the analysis results. FIG. [Figure 8B] 10A and 10B are schematic diagrams showing choke structures on the left and right sides based on analysis results. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, a mode for carrying out the present invention (hereinafter referred to as "embodiment") will be described in detail with reference to the drawings as appropriate, with the direction shown in FIG.

[0009] Fig. 1 is a perspective view of the cooking device of this embodiment as seen from the front side. Fig. 2 is a cross-sectional view taken along line AA in Fig. 1. Fig. 1 shows the cooking device with the door closed, with the cabinet (outer frame) covering the top and left and right sides of the main body removed. As shown in Fig. 1, the cooking appliance 1 has a main body 3 provided with a heating chamber 2 for storing food to be cooked (not shown) inside a cabinet (outer frame). A door 4 that opens vertically is provided in front of the heating chamber 2.

[0010] The door 4 is provided with an outer glass 7 (see FIG. 2) and an inner glass 9 (see FIG. 2) that can withstand high temperatures and allow the user to check the cooking status of the food being cooked (not shown). Between the outer glass 7 and the inner glass 9, there is provided a steel punched metal 8 (see FIG. 2) with multiple holes formed therein. A handle 4a for opening and closing the door 4 is provided at the top of the exterior of the door 4. A synthetic resin cover 17 is provided on the inside of the door 4 to cover a choke structure 20 (see FIG. 3) that is provided along the outer periphery of the door 4.

[0011] A microwave generator 5 is provided at the bottom of the main body 3. This microwave generator 5 is composed of a magnetron that generates microwaves, a waveguide that sends the microwaves to the heating chamber 2, and the like. High frequency waves (microwaves) are supplied from the microwave generator 5 to an object to be heated (not shown) placed in the heating chamber 2, thereby heating the object. The location where the microwave generator 5 is provided is not limited to the bottom of the main body 3, but may also be the top or side.

[0012] A frame portion (heating chamber front plate) 16 made of a conductive plate is provided from the outer periphery of the heating chamber opening 15 toward the outer periphery of the main body 3. This frame portion 16 is formed in a rectangular frame shape. Furthermore, upper edge portion 16a and lower edge portion 16b of frame portion 16, which extend in the left-right direction on the top and bottom, are formed longer than left edge portion 16c and right edge portion 16d, which extend in the up-down direction on the left and right. The main body 3 is also provided with a door switch 18 that detects whether the door 4 is open or closed.

[0013] As shown in Fig. 2, the door 4 is rotatably connected to the lower part of the main body 3, and is configured so that when the door 4 is fully closed, the outer surface of the door 4 faces forward, and when the door 4 is fully open, the inner surface of the door 4 faces substantially upward (see Fig. 1). In addition, when the door 4 is fully closed, the handle 4a is positioned to protrude forward, and when the door 4 is fully open, the handle 4a is positioned to protrude downward (see Fig. 1).

[0014] Fig. 3 is a perspective view of the door unit of the cooking device of this embodiment, in which cover 17 (see Fig. 1) covering the outer peripheral surface of the inside of the door has been removed. 3, the door 4 has a structure in which a metal door base 4b is covered with a resin door frame 4c. The door base 4b forms the framework of the door 4, and is made by processing a metal plate such as iron by cutting, punching, bending, drawing, and the like.

[0015] The door base 4b also includes a contact surface 4d that contacts the frame 16 (see FIG. 1) and a choke structure 20 that extends vertically and horizontally from the contact surface 4d. The door base 4b is designed so that the contact surface 4d contacts the frame 16 of the main body 3. If the door base 4b and the frame 16 are in contact with each other without any gaps, microwaves will not leak from around the door 4. However, if the door base 4b or the frame 16 is heated to a high temperature, for example, by oven heating, the metal may expand, changing the flatness of the surface. In this case, a small gap may form between the door base 4b and the frame 16, potentially allowing microwaves to leak through the gap. If a gap does form between the door base 4b and the frame 16, the choke structure 20 prevents microwaves from leaking through the gap. Furthermore, the gap S is more likely to occur at the upper edge 4p of the door 4 where the handle 4a is located, which is located on the opposite side from the rotation axis g (see FIG. 2) of the lower edge 4q of the door 4, than at the lower edge 4q.

[0016] Choke structure 20 is formed by bending a metal plate made of, for example, iron multiple times and forming a comb-like shape along the circumferential direction. Choke structure 20 is arranged along the entire outer periphery on the back side of door 4. That is, choke structure 20 is located on top edge 4p, bottom edge 4q, left edge 4r, and right edge 4s of door 4. Handle 4a is located on top edge 4p. Door 4 is provided with a rotation axis g (see FIG. 2) on bottom edge 4q, which serves as a fulcrum when opening and closing door 4.

[0017] Fig. 4 is an enlarged view of the portion X in Fig. 2. In Fig. 4, the cover 17 covering the outer peripheral surface on the inside of the door is removed. 4, when door 4 is closed, choke structure 20 has bottom surface 21 (choke groove bottom surface) facing frame portion 16 of main body 3, side surfaces 22, 22 extending from both ends of bottom surface 21 toward main body 3 (toward frame portion 16), and choke groove 24 having opening (choke groove opening) 23 facing main body 3. Choke groove 24 is formed in a concave shape in vertical cross section with the concave surface facing frame portion 16 so that frame portion 16 and opening 23 face each other. Choke grooves 24 are configured to be periodically arranged at equal intervals along upper side portion 4p, lower side portion 4q, left side portion 4r, and right side portion 4s.

[0018] Choke groove 24 has a closed wall surface 25 that is substantially parallel to bottom surface 21 and covers a part of opening 23, and a folded portion 26 that extends from closed wall surface 25 toward the inside of choke groove 24, substantially perpendicular to closed wall surface 25. Closed wall surface 25 has a length that is approximately half the distance between one side surface 22 and the other side surface 22. The length (height) of folded portion 26 will be described in detail later.

[0019] In this way, by providing the folded portion 26, the choke groove 24 makes the impedance near the opening 23 infinite, thereby ensuring leakage shielding performance. Furthermore, the gap S between the door 4 and the frame portion 16 forms a leakage path R (see dashed arrow) that runs from the heating chamber 2 (see FIG. 1) toward the outer periphery of the main body 3. This leakage path R is composed of an overlapping portion 30 extending from the outer periphery of the heating chamber opening 15 (see FIG. 1) to the opening 23, and a section extending from the opening 23 to the folded portion 26. The overlapping portion 30 lowers the impedance at the entrance (opening 23) of the leakage path R on the heating chamber 2 (see FIG. 1) side, thereby suppressing microwave penetration into the leakage path R, depending on the length of the overlapping portion 30. The section length is the distance of the overlapping portion 30, and the longer the overlapping portion 30, the more effectively microwaves can be suppressed.

[0020] As described in the background art, in a heating device that uses microwaves, the amount of microwaves that leak to the outside is regulated by law in terms of the power density of the radio waves leaking from the microwave device (microwave generator 5) when the door 4 is closed (hereinafter referred to as the "door closed state") and when the door 4 is half-open (the door is open to the very limit at which cooking can begin) (hereinafter referred to as the "door half-open state"), in order to prevent unintended heating of objects or interference with communications by radio waves.

[0021] When the door is closed, the leaked radio waves are attenuated by overlapping portion 30 and enter perpendicularly into choke groove 24 through leakage path R, where they are further attenuated by choke structure 20. On the other hand, when the door is half-open, a gap S is generated between door 4 and frame portion 16, which is made of a conductive plate extending from the outer periphery of heating chamber opening 15 (see FIG. 1) toward the outer casing of the main body, reducing overlapping portion 30 and reducing the leakage radio wave performance. Furthermore, the increased rate of oblique incidence on choke groove 24 reduces the effect of choke structure 20 in suppressing leaked radio waves.

[0022] Next, an analysis example of the leakage wave shielding performance of the choke groove 24 will be described with reference to FIG. 5. FIG. 5A is a graph showing an analysis example of the leakage wave shielding performance versus frequency for a conventional choke groove. FIG. 5B is a graph showing an analysis example of the leakage wave shielding performance versus the incident angle of the leakage wave incident on the choke groove. FIG. 6 is an explanatory diagram showing the positional relationship between the door base and the frame portion when the incident angle of the leakage wave is changed. In FIGS. 5A and 5B, the horizontal axis represents frequency (GHz) and the vertical axis represents shielding characteristics (dB), with the downward movement of the graph indicating better leakage wave shielding.

[0023] The wave leakage shielding performance of the choke structure changes with frequency, as shown in the graph in Figure 5A, and there is a frequency band in which a shielding effect can be obtained. In particular, the frequency range in which the shielding characteristic (attenuation rate) is less than -50 dB is called the bandwidth, and the wider this range is, the better the wave leakage shielding performance is judged to be.

[0024] As shown in the graph in FIG. 5B, the shielding characteristic (dB) on the vertical axis drops downward, indicating a frequency band in which a shielding effect can be obtained. This frequency band varies significantly depending on the structure of the choke groove 24 and the direction of crossing the opening 23 of the choke groove 24. When leakage waves with only perpendicular components enter the opening 23, the leakage wave shielding characteristic is represented by the solid curve at an incident angle of 90 degrees. The frequency band in which leakage wave shielding performance is obtained and the operating frequency are almost identical. Note that the incident angle of 90 degrees is the state shown in the upper diagram 200 of FIG. 6, which is the angle formed by the contact surface portion 4d with respect to the perpendicular line to the frame portion 16 (see the dashed line). However, when leakage waves with shallower incident angles (see the 100 degrees shown in the middle diagram 300 of FIG. 6 or the 110 degrees shown in the lower diagram 400 of FIG. 6) including circular components enter, the characteristic is represented by the dashed curve, and the frequency band in which leakage wave shielding performance is obtained is significantly different from the operating frequency range. As a result, when the door is half-open, many leaked waves are incident that are out of the frequency band where leakage shielding performance is obtained, which shows that the leakage wave suppression effect of choke structure 20 is not fully exhibited. Also, when the incident angle is 110° as shown in lower diagram 400 of Fig. 6, the frequency that deviates from the operating frequency range is greater than when the incident angle is 100° as shown in middle diagram 300 of Fig. 6.

[0025] Figure 7 is a graph showing an example of an analysis of leakage shielding performance when the dimensions of the folded portion of the choke groove are changed. Figure 7 shows the leakage shielding performance of the choke structure when the height dimension of folded portion 26 provided in choke groove 24 is changed from the reference (0 mm) to +2 mm, +4 mm, and -2 mm. The reference is a waveform with a peak near a frequency of 2.45 GHz (between 2.4 GHz and 2.5 GHz) when the door is closed.

[0026] As can be seen from the analysis results in Figure 7, changing the height dimension of the folded portion 26 provided in the choke structure 20 (choke groove 24) shifts the frequency at which the shielding effect is greatest. When the folded portion 26 is +2 mm from the reference, the waveform shifts in the direction of increasing the frequency peak value (to the right in Figure 7), as indicated by the short-dotted dashed line. When the folded portion 26 is +4 mm from the reference, the waveform shifts in the direction of increasing the frequency peak value even more than when the folded portion 26 is +2 mm (to the right in Figure 7), as indicated by the long-dotted dashed line. On the other hand, when the folded portion 26 is -2 mm from the reference, the waveform shifts in the direction of decreasing the frequency peak value (to the left in Figure 7), as indicated by the dash-dot line.

[0027] From the above analysis results, it is possible to ensure leakage shielding performance when the door is half-open by intentionally designing the height dimension of the folded portion 26 of the choke structure on the upper edge 4p, which is located close to the handle 4a of the door 4 and where the leakage radio waves are most likely to be obliquely incident on the choke groove 24 when the door is half-open, to be smaller than the height dimension of the folded portion 26 of the choke structure on the other edges (lower edge 4q, left edge 4r, right edge 4s).

[0028] 8A and 8B are schematic diagrams showing the choke structures of the top and bottom edges based on the analysis results, respectively, and the choke structures of the left and right edges based on the analysis results. As shown in Figure 8A, choke structure 20 located on upper side 4p of door 4 has folded portion 26A (26) in choke groove 24. Also, choke structure 20 located on lower side 4q has folded portion 26B (26) in choke groove 24. Also, height dimension H1 of folded portion 26A is formed to be lower (shorter) than height dimension H2 of folded portion 26B.

[0029] As shown in Figure 8B, choke structure 20 located on left side 4r of door 4 has folded portion 26C (26) in choke groove 24. Also, choke structure 20 located on right side 4s has folded portion 26D (26) in choke groove 24. Also, height dimension H2 of folded portions 26C, 26D is the same as height dimension H2 of folded portion 26B in Figure 8A.

[0030] In this way, the height H1 of the folded portion 26A at the position (side) where the handle 4a is provided is set lower than the height H2 of the folded portions 26B, 26C, and 26D at the positions (sides) where the handle 4a is not provided. As a result, the choke structure 20 with the folded portion 26A when the door is closed has the characteristics shown by minus 2 mm in Figure 7. Therefore, when the door is half-open, the waveform shifts to the waveform shown by the reference in Figure 7, corresponding to the operating frequency range (2.4 to 2.5 GHz). This makes it possible to suppress microwave leakage when the door is half-open. In this way, suppressing microwave leakage when the door is half-open eliminates the need for separate components such as radio wave absorbing sheets that are installed in areas where radio waves leak (e.g., the upper edge).

[0031] As described above, the cooking appliance 1 of this embodiment includes a microwave generator 5 that heats an object to be heated at high frequency, a main body 3 that includes a heating chamber 2 in which the object to be heated is accommodated, and an openable / closable door 4 that is provided in front of the heating chamber 2. The door 4 has a choke structure 20 formed by bending a metal plate multiple times around the outer periphery of the door 4. The choke structure 20 has a bottom surface 21 that faces the main body 3, side surfaces 22, 22 extending from both ends of the bottom surface 21 toward the main body 3, and a choke groove 24 having an opening 23 that faces the main body 3, and the choke groove 24 is disposed along the outer periphery of the door 4. The choke groove 24 has a closing wall surface 25 that is substantially parallel to the bottom surface 21 and covers a portion of the opening 23, and a folded portion 26 that extends from the closing wall surface 25 toward the inside of the choke groove 24, substantially perpendicular to the closing wall surface 25. Height H1 of folded portion 26A provided in choke groove 24 on the side (top side 4p) where handle 4a of door 4 is located is made lower than height H2 of folded portions 26B, 26C, 26D provided in choke groove 24 on the other sides (bottom side 4q, left side 4r, right side 4s) of door 4. In other words, height H1 of folded portion 26A provided in choke groove 24 on the top side 4p opposite to bottom side 4q where pivot shaft g of door 4 is located is made lower than height H2 of folded portions 26B, 26C, 26D provided in choke groove 24 on the other sides (bottom side 4q, left side 4r, right side 4s) of door 4. This makes it possible to provide a cooking appliance 1 with high microwave leakage performance.

[0032] The present invention is not limited to the above-described embodiment and includes various modifications. For example, while the present embodiment has been described using a vertically opening door 4 with the handle 4a on the top edge 4p as an example, it may also be applied to a horizontally opening door with the handle on the left edge 4r or right edge 4s. In the case of a door with a handle on the right edge 4s, since the pivot shaft is located on the left edge 4r side, the height dimension of the folded portion 26 provided in the choke groove 24 on the right edge 4s is made lower than the height dimension of the folded portion 26 provided in the choke groove 24 on the other edges of the door 4 (the top edge 4p, the bottom edge 4q, and the left edge 4r). Even with this configuration, a cooking appliance 1 with high microwave leakage performance can be provided.

[0033] Furthermore, the gap between the door 4 and the main body 3 increases from one side where the pivot axis g is located to the other side. Therefore, the heights of the folded portions 26C, 26D provided in the choke grooves 24 on the left side 4r and right side 4s of the door 4, which are perpendicular to the bottom side 4q where the pivot axis g is located, are gradually reduced from one side where the pivot axis g is located to the other side. That is, the heights of the folded portions 26C, 26D of the choke grooves 24 located on the side where the pivot axis g is located are made the longest, and the heights of the folded portions 26C, 26D of the choke grooves 24 located on the opposite side from the pivot axis g are made the shortest. This configuration effectively reduces microwave leakage when the door is half-open compared to when the heights of the folded portions 26C, 26D are all the same. [Explanation of symbols]

[0034] 1 Cooker 2 Heating chamber 3 Main unit 4-door 4a Handle 4p Top edge (side with handle) 4q Lower part (other side) 4r Left side (other side) 4s Right side (other side) 5. Microwave generator (heat source) 20 Choke structure 21 Bottom 22 Side 23 Opening 24 Choke groove 25 Blocked Wall 26, 26A, 26B, 26C, 26D Folded part g Rotating shaft H1 Height dimension (height dimension of the folded part provided in the choke groove on the side where the door handle is located) H2 Height dimension (height dimension of the folded part provided in the choke groove on the other side of the door) R Leakage path S Gap

Claims

1. a heat source for high frequency heating of an object to be heated; a main body having a heating chamber in which the object to be heated is accommodated; an openable and closable door provided in front of the heating chamber, The door has a choke structure formed by bending a metal plate multiple times on the outer periphery of the door, the choke structure has a bottom surface facing the main body, side surfaces extending from both ends of the bottom surface toward the main body, and a choke groove having an opening facing the main body, the choke groove being arranged along the outer periphery of the door; the choke groove has a closing wall surface that is substantially parallel to the bottom surface and covers a part of the opening, and a folded portion that extends from the closing wall surface toward an inside of the choke groove substantially perpendicular to the closing wall surface, a height dimension of the folded portion provided in the choke groove on the side of the door where the handle is located being lower than a height dimension of the folded portion provided in the choke groove on the other side of the door.

2. a heat source for high frequency heating of an object to be heated; a main body having a heating chamber in which the object to be heated is accommodated; an openable and closable door provided in front of the heating chamber, The door has a choke structure formed by bending a metal plate multiple times on the outer periphery of the door, the choke structure has a bottom surface facing the main body, side surfaces extending from both ends of the bottom surface toward the main body, and a choke groove having an opening facing the main body, the choke groove being arranged along the outer periphery of the door; the choke groove has a closing wall surface that is substantially parallel to the bottom surface and covers a part of the opening, and a folded portion that extends from the closing wall surface toward an inside of the choke groove substantially perpendicular to the closing wall surface, a height dimension of the folded portion provided in the choke groove on the side opposite to the side on which the pivot shaft of the door is located, being lower than a height dimension of the folded portion provided in the choke groove on the other side of the door.

3. The cooking device according to claim 2, A cooking device characterized in that the height dimension of the folded portion provided in the choke groove on the side perpendicular to the pivot axis of the door is gradually reduced from one side of the pivot axis to the other side.

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