Electromagnetic cooker

Abstract

To effectively suppress magnetic flux leakage from a bottom of a casing to the outside.SOLUTION: An electromagnetic cooker 1 includes: a casing 3; a heating coil 11 placed in the casing 3; a first shield plate 35 placed in the casing 3 so that it is positioned below the heating coil 11; and a second shield plate 38 placed in the casing 3 below the first shield plate 35, so that it is positioned below the heating coil 11.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an induction cooker. [Background technology]

[0002] The electromagnetic cooker disclosed in Patent Document 1 has a heating coil disposed inside a casing, and induction heats an object to be heated, such as a cooking vessel, placed on the casing. A shield plate is disposed inside the casing below the heating coil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2015-159039 Summary of the Invention [Problem to be solved by the invention]

[0004] In the electromagnetic cooker of Patent Document 1, the shield plate can prevent magnetic flux from leaking out from the bottom of the casing to the outside, but there is still room for improvement.

[0005] An object of the present invention is to provide an induction cooker that can effectively prevent magnetic flux from leaking to the outside from the bottom of the casing. [Means for solving the problem]

[0006] One aspect of the present invention provides an induction cooker comprising a casing, a heating coil disposed within the casing for induction heating an object to be heated disposed on the casing, a first shield plate disposed within the casing so as to be positioned below the heating coil, and a second shield plate disposed within the casing below the first shield plate so as to be positioned below the heating coil.

[0007] In this embodiment, two shield plates are disposed below the heating coil, which effectively prevents the magnetic flux generated from the heating coil from leaking out from the bottom of the casing to the outside.

[0008] The induction cooker further includes a coil bobbin supporting the heating coil and an insulating plate interposed between the first shield plate and the second shield plate, and by attaching the coil bobbin to the casing, the first shield plate, the insulating plate, and the second shield plate are sandwiched between the bottom of the casing and the coil bobbin. This prevents heat from the heating coil from leaking to the outside through the bottom of the casing. Furthermore, no additional parts (mounting structure) are required to attach the shield plate, the insulating plate, and the second shield plate. This reduces the number of parts that make up the induction cooker and allows the induction cooker to be made thinner.

[0009] The induction cooker further includes a circuit board, positioned adjacent to the heating coil when viewed from above, on which multiple electronic components for controlling the heating coil are mounted, and the second shield plate includes an extension portion extending to be positioned below the circuit board. This more effectively prevents magnetic flux generated by the heating coil from leaking out of the bottom of the casing. Furthermore, the second shield plate with the extension portion can absorb and dissipate heat from the multiple electronic components, as well as from the heating coil. In other words, the second shield plate can both suppress magnetic flux leakage and dissipate heat from the heating coil and the electronic components mounted on the circuit board, eliminating the need for separate dedicated components for each purpose. This reduces the number of components constituting the induction cooker and allows the induction cooker to be made thinner.

[0010] The casing further includes an insulating plate having heat insulation properties and disposed between the circuit board and the extension portion so as to be adjacent to the heating coil when viewed from above, thereby ensuring the insulation of the circuit board including the electronic components and preventing heat from the electronic components from leaking to the outside through the bottom of the casing. [Effects of the Invention]

[0011] In the present invention, leakage of magnetic flux from the bottom of the casing to the outside can be effectively suppressed. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view of an induction cooker according to an embodiment of the present invention; [Figure 2] FIG. 2 is an enlarged cross-sectional view of a portion cut along line II-II in FIG. [Figure 3] FIG. 2 is a perspective view of an induction cooker with the top plate and upper case removed. [Figure 4] FIG. 2 is a perspective view showing a lower case, a coil set, and a circuit board. [Figure 5] FIG. [Figure 6] FIG. 4 is an exploded perspective view of a coil bobbin and a temperature sensor. [Figure 7] FIG. 2 is an exploded perspective view of a coil set, a circuit board, a shield plate, a heat insulating plate, and an insulating plate, as viewed from above. [Figure 8] FIG. 2 is an exploded perspective view of the coil set, the circuit board, the shield plate, the heat insulating plate, and the insulating plate as viewed from below. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] Referring to FIG. 1, an induction cooker 1 according to an embodiment of the present invention is a so-called tabletop type, and has a rectangular shape when viewed from above.

[0015] In the induction cooker 1, the extension direction of one pair of opposite sides of the rectangle is the width direction W, with the direction indicated by the arrow being the left side and the direction opposite to the arrow being the right side. In the induction cooker 1, the extension direction of the other pair of opposite sides of the rectangle is the depth direction D, with the direction indicated by the arrow being the front side and the direction opposite to the arrow being the back side. The direction perpendicular to both the width direction W and the depth direction D is the height direction (thickness direction) H, with the direction indicated by the arrow being the top side and the direction opposite to the arrow being the bottom side. When the induction cooker 1 is placed horizontally on a table, the width direction W and the depth direction D are oriented horizontally, and the height direction H is oriented vertically. This concept of directions is merely an example and can be changed as appropriate depending on the posture of the induction cooker 1, etc.

[0016] 1 to 3, the induction cooker 1 includes a casing 3, a coil set 10, and a circuit board 20. In this embodiment, the magnetic flux and heat generated from the heating coil 11 included in the coil set 10 are effectively prevented from leaking from the bottom of the casing 3 onto the table.

[0017] The casing 3 is composed of a lower case 4, an upper case 5, and a top plate 6. The lower case 4, the upper case 5, and the top plate 6 define an internal space 7 in which the coil set 10 and the circuit board 20 are disposed.

[0018] 3 and 4, the lower case 4 is tray-shaped with an open top and includes a bottom wall 4a and a peripheral wall 4b. The bottom wall 4a is rectangular when viewed from above, and the peripheral edge of the bottom wall 4a defines the rectangular outline. The peripheral wall 4b is rectangular in shape and protrudes upward from the peripheral edge of the bottom wall 4a.

[0019] The bottom wall 4a is provided with three types of bosses 4c to 4e. Of these, the first boss 4c is configured to be screwed to assemble the upper case 5. The second boss 4d is configured to be screwed to assemble the coil set 10. The third boss 4e is configured to be screwed to assemble the circuit board 20. A plurality of ribs 4f that support the underside of the circuit board 20 are formed on the outer periphery of the boss 4e.

[0020] 2 and 3, the upper case 5 is formed as a rectangular ring-shaped body and is fitted from above into the upper end opening of the lower case 4 (the upper end of the peripheral wall 4b). A rectangular upper opening 5a is formed in the center of the upper case 5. The upper case 5 covers only the outer periphery of the lower case 4 and forms a flange. The upper case 5 is assembled to the lower case 4 by fastening screws that pass through the bosses 4c.

[0021] Top plate 6 is made of a material (such as ceramic) that is permeable to magnetic flux, and is attached in close contact with upper case 5 so as to close upper opening 5a.

[0022] 2, 4, and 5, the coil set 10 is housed in the internal space 7 of the casing 3. The coil set 10 includes a heating coil 11, a coil bobbin 12, a ferrite core 13, and an upper insulating plate 14.

[0023] Heating coil 11 is configured with multiple windings wound in a double annular shape, and when a high-frequency current is passed through it, eddy currents are generated in an object to be heated (for example, a cooking vessel not shown) placed on top plate 6, thereby inductively heating the object to be heated. Heating coil 11 is supported by coil bobbin 12 and is placed close to the underside of top plate 6.

[0024] The coil bobbin 12 is attached to the casing 3 and supports the ferrite core 13, upper insulating plate 14, and heating coil 11 in this order from bottom to top. The coil bobbin 12 has a cylindrical boss portion 12a disposed in the center, a ring-shaped rim portion 12b concentric with the boss portion 12a, and a plurality of spoke portions 12c connecting the boss portion 12a and the rim portion 12b.

[0025] A plurality of (three in this embodiment) screw fastening portions 12d are provided at intervals in the circumferential direction on the outer periphery of the rim portion 12b. Referring to FIG. 8, a support portion 12e that supports the upper surface of the circuit board 20 is provided on the rim portion 12b and protrudes downward. The coil bobbin 12 is assembled to the lower case 4 by fastening a screw that passes through the screw fastening portion 12d to a boss 4d of the lower case 4. The circuit board 20 is sandwiched and supported between the coil bobbin 12 and the lower case 4 by the support portion 12e. A groove for accommodating one ferrite core 13 is provided on each of the plurality of spoke portions 12c. A rib 12f that protrudes downward is further provided on the rim portion 12b. The rib 12f extends in a roughly semicircular ring shape around the boss portion 12a and has the functions of guiding the air blown by the fans 30, 31, which will be described in detail later, and of sandwiching the first shield plate 35, the insulating plate 36, and the second shield plate 38 between itself and the bottom wall 4a of the lower case 4.

[0026] 4 and 5, the ferrite core 13 is configured to converge the magnetic flux generated from the heating coil 11. The ferrite core 13 is made of a rectangular plate and is housed in a groove formed in the spoke portion 12c of the coil bobbin 12.

[0027] The upper insulating plate 14 is made of mica, which has thermal insulation properties, and is interposed between the coil bobbin 12 and the heating coil 11, covering the ferrite core 13 from above. The upper insulating plate 14 is shaped so that it can cover the rim portion 12b and the multiple spoke portions 12c of the coil bobbin 12 from above. The upper insulating plate 14 has fan-shaped through holes at positions corresponding to the spaces between adjacent spoke portions 12c of the coil bobbin 12.

[0028] 5 and 6, two temperature sensors are attached to the coil set 10 to detect the temperature of an object to be heated placed on the top plate 6. One of the two temperature sensors is a center sensor 15 attached to the boss portion 12a of the coil bobbin 12. The other is a side sensor 16 attached between adjacent predetermined spoke portions 12c. The center sensor 15 and the side sensor 16 can both be a thermistor. The center sensor 15 and the side sensor 16 each have a pair of lead wires 15a, 16a.

[0029] The center sensor 15 is attached to the upper surface side of a center holder 17 that is fitted into the boss portion 12a of the coil bobbin 12. A pair of lead wires 15a are arranged in an orientation that extends downward (vertically) relative to the center holder 17. The center sensor 15 is exposed upward from the center holder 17 and is arranged close to or in contact with the lower surface of the top plate 6.

[0030] The side sensor 16 is attached to the upper surface of a side holder 18 that is fitted between a pair of spokes 12c of the coil bobbin 12. Similar to the center sensor 15, the pair of lead wires 16a are arranged in an orientation that extends downward (vertically) relative to the side holder 18. The side sensor 16 is exposed upward from the side holder 18 and is arranged in close proximity to or in contact with the underside of the top plate 6.

[0031] A fuse 19 is further disposed in the center holder 17. Unlike the lead wires 15a of the center sensor 15, a pair of lead wires 19a of the fuse 19 are disposed in a position extending sideways (horizontally).

[0032] 2 to 4, the circuit board 20 is disposed in the internal space 7 of the casing 3 so as to be adjacent to the outer side of the heating coil 11 when viewed from above. The circuit board 20 includes a board main body 21 and a plurality of electronic components 22 attached to the board main body 21. A wiring pattern (not shown) printed on the board main body 21 and the plurality of electronic components 22 form a heating circuit for passing electricity through the heating coil 11 to heat the object to be heated.

[0033] The board body 21 is U-shaped when viewed from above, and is placed in the lower case 4 in a position with the right side open in Figures 3 and 4. The outer periphery of the board body 21 is provided with a plurality of punched portions 21a corresponding to the plurality of bosses 4c, 4e of the lower case 4. Some of the punched portions 21a are formed as holes that penetrate the board body 21 in the height direction (thickness direction). The rest of the punched portions 21a are formed as U-shaped notches cut out from the outer periphery of the board body 21. The size of the punched portions 21a is larger than the outer shape of the bosses 4e and smaller than the imaginary outer shape connecting the outer ends of the plurality of ribs 4f.

[0034] The board main body 21 is configured so that the upper part of the boss 4e protrudes from the punched portion 21a when placed inside the lower case 4. A spacer 23 is placed over this protruding portion and screwed onto the boss 4e from above the spacer 23, thereby assembling the circuit board 20 to the lower case 4 with the board main body 21 held down from above by the spacer 23. In addition, an insulating plate 37 and a second shield plate 38, which will be described in detail later, are sandwiched between the board main body 21 and the lower case 4.

[0035] The coil set 10 is disposed in the center of the U-shaped space of the substrate body 21. When viewed from above, the substrate body 21 barely overlaps the heating coil 11. However, part of the inner peripheral edge 21b of the substrate body 21 may overlap part of the outer peripheral edge of the heating coil 11 in the height direction. Part of the inner peripheral edge 21b of the substrate body 21 overlaps part of the rim portion 12b of the coil bobbin 12 in the height direction. After being attached to the lower case 4, the inner peripheral portion of the substrate body 21 is sandwiched and supported by the support portion 12e of the coil bobbin 12 by further attaching the coil set 10 to the lower case 4. In other words, the outer peripheral portion of the substrate body 21 is fixed by screws via spacers 23, and the inner peripheral portion of the substrate body 21 is supported by the screwed coil bobbin 12.

[0036] The inner periphery of the substrate body 21 is supported by a downwardly protruding support portion 12e of the coil bobbin 12. This ensures a predetermined gap between the inner periphery of the substrate body 21 and the rim portion 12b of the coil bobbin 12. This allows electronic components to be placed on the inner periphery of the substrate body 21, located below the rim portion 12b. However, only electronic components that protrude from the substrate body 21 by 1.5 mm or less are allowed to be placed on the inner periphery of the substrate body 21. This ensures that the area of ​​the circuit board 20 is secured while preventing the induction cooker 1 from becoming too thick due to the provision of excessive gaps.

[0037] 3 and 7, the electronic components 22 include a diode bridge 22A that converts AC from a commercial power source into DC, a transistor 22B that adjusts the amount and frequency of current flowing through the heating coil 11, an IC chip 22C that functions as a controller that controls the operation of the transistor 22B, a plurality of capacitors 22D for smoothing or resonance, and a switching coil 22E that switches the diode bridge 22A. The transistor 22B is, for example, an IGBT (insulated gate bipolar transistor). At least a portion of the capacitor 22D is an electrolytic capacitor.

[0038] 1, an operation unit 25 operated by a user is provided on the front top surface of the induction cooker 1. Referring to FIGS. 3 and 4, the operation unit 25 is long in the width direction and includes a liquid crystal display unit 26 attached to the circuit board 20 and a plurality of touch switches 28 (four in this embodiment) attached to an operation board 27. Like the board main body 21, the operation board 27 is attached to the lower case 4 by screwing it to the boss 4e via the spacer 23.

[0039] Here, bosses 4c for assembling upper case 5 are provided on lower case 4 so as to be positioned near liquid crystal display unit 26. Support portions 4g for supporting the lower surface of operation board 27 are provided on boss 4c. Furthermore, screw fastening portions 5b are provided on upper case 5 so as to correspond to boss 4c.

[0040] The circuit board 20 and operation board 27 are placed inside the lower case 4, and screws passing through the bosses 4c are fastened to the screw fastening portions 5b of the upper case 5. This sandwiches the circuit board 20 and operation board 27 between the bosses 4c and the screw fastening portions 5b, allowing the LCD display unit 26 and touch switches 28 to be positioned in fixed positions. As a result, the LCD display unit 26 and touch switches 28 are placed in predetermined positions near the top plate 6 that constitutes the operation unit 25 (see FIG. 1). Therefore, visibility of the LCD display unit 26 and operability of the touch switches 28 can be ensured without adding any dedicated parts.

[0041] In response to an operation on the operation unit 25 (see FIG. 1), the circuit board 20 supplies power to the heating coil 11, thereby inductively heating an object to be heated on the top plate 6. When the induction cooker 1 is in operation, the heating coil 11 and several electronic components 22 generate heat. Examples of electronic components 22 that generate a lot of heat include a diode bridge 22A, a transistor 22B, and an IC chip 22C. Examples of electronic components 22 whose operation may become unstable due to heat include the IC chip 22C. Examples of electronic components 22 whose deterioration is accelerated by heat include a capacitor 22D (particularly an electrolytic capacitor).

[0042] To dissipate heat from the electronic components 22, a first fan 30 and a second fan 31 are disposed in the internal space 7 of the casing 3, and a heat sink 32 is disposed in the board main body 21. Referring to FIGS. 2 and 8, the air blown by the fans 30 and 31 is separated by the ribs 12f of the coil bobbin 12 and guided without mixing. This prevents unstable operation of the heating circuit due to heat and deterioration of the electronic components 22. The first fan 30 and the second fan 31 are low-profile blower fans with a rotating shaft extending in the height direction. Although only the housings of the first fan 30 and the second fan 31 are shown in the figure, rotatably supported impellers (not shown) are disposed within the housings.

[0043] During operation of the induction cooker 1, magnetic flux and heat generated from the heating coil 11 may leak out onto the table from the bottom wall 4a of the lower case 4. Therefore, in this embodiment, as shown in Figures 2, 7, and 8, a first shield plate 35, a heat insulating plate 36, an insulating plate 37, and a second shield plate 38 are arranged below the coil set 10 and the circuit board 20.

[0044] The first shield plate 35 is configured to prevent the magnetic flux of the heating coil 11 from leaking to the outside through the bottom wall 4a of the lower case. The first shield plate 35 is disposed within the casing 3 so as to be located below the heating coil 11. The first shield plate 35 is generally annular and is made of a thin aluminum plate. When viewed from above, the outer shape of the first shield plate 35 is slightly smaller than the outer shape of the heating coil 11 and the shape of the inner peripheral edge 21b of the circuit board 20, and the first shield plate 35 is disposed within the U-shaped space of the circuit board 20.

[0045] The boss portion 12a of the coil bobbin 12 passes through a through-hole 35a at the center of the first shield plate 35. The first shield plate 35 is provided with a plurality of positioning holes 35b (three in this embodiment). Positioning protrusions 4h (see also FIG. 4) formed on the lower case 4 are inserted into the positioning holes 35b. This allows the first shield plate 35 to be positioned in a fixed position in the lower case 4 by arranging the first shield plate 35 inside the lower case 4.

[0046] The heat insulating plate 36 is configured to prevent heat from the heating coil 11 from leaking to the outside through the bottom wall 4a of the lower case. The heat insulating plate 36 is disposed by stacking it on the lower surface of the first shield plate 35 and on the upper surface of the second shield plate 38, that is, it is interposed between the first shield plate 35 and the second shield plate 38, and covers the area below the heating coil 11. The heat insulating plate 36 is made of mica, which has thermal insulating properties, and is slightly larger than the first shield plate 35. When viewed from above, the outer shape of the heat insulating plate 36 is slightly smaller than the outer shape of the heating coil 11 and the shape of the inner peripheral edge 21b of the circuit board 20, and it is disposed within the U-shaped space of the circuit board 20.

[0047] The boss portion 12a of the coil bobbin 12 passes through the central through-hole 36a of the heat insulating plate 36. The heat insulating plate 36 is provided with a plurality of positioning holes 36b (three in this embodiment). The positioning holes 36b are the same in number and at the same positions as the positioning holes 35b of the first shield plate 35. Positioning protrusions 4h (also see FIG. 4) of the lower case 4 are inserted into the positioning holes 36b. This allows the heat insulating plate 36 to be positioned in a fixed position in the lower case 4 by arranging the heat insulating plate 36 inside the lower case 4.

[0048] The insulating plate 37 is configured to electrically insulate the circuit board 20 and to prevent heat from the heating coil 11 and the electronic components 22 from leaking to the outside through the bottom wall 4a of the lower case. The insulating plate 37 is disposed below the circuit board 20 so as to be adjacent to the heating coil 11 when viewed from above. The insulating plate 37 is made of mica, which has heat insulating properties, and, like the circuit board 20, is U-shaped when viewed from above and is disposed in the lower case 4 with the right side open in Figures 3 and 4.

[0049] More specifically, the insulating plate 37 has an inner peripheral edge 37a that is slightly larger than the outer peripheral edge of the heat insulating plate 36, and is disposed adjacent to the outside of the heat insulating plate 36. The inner peripheral edge 37a protrudes toward the center of the heating coil 11 more than the inner peripheral edge 21b of the circuit board 20. The thickness of the insulating plate 37 is thicker than that of the heat insulating plate 36 and is set to be equal to the total thickness of the heat insulating plate 36 and the first shield plate 35. Notches 37b are formed on the outer periphery of the insulating plate 37, corresponding to the bosses 4c to 4e (see also FIG. 4) of the lower case 4, and exposing them upward.

[0050] The second shield plate 38 is configured to prevent the magnetic flux and heat of the heating coil 11 and the heat of the electronic components 22 from leaking to the outside through the bottom wall 4a of the lower case. The second shield plate 38 is made of a thin aluminum plate and is disposed by stacking it below the heat insulating plate 36 and the insulating plate 37. More specifically, the second shield plate 38 includes a shield portion 38a located below the heating coil 11 and an extension portion 38d located below the circuit board 20.

[0051] The shield portion 38a is provided with a through hole 38b and a positioning hole 38c. The through hole 38b is provided at a position corresponding to the through hole 35a of the first shield plate 35 and has the same diameter as the through hole 35a. The boss portion 12a of the coil bobbin 12 passes through the through hole 38b. The positioning hole 38c is provided at a position corresponding to the positioning hole 35b of the first shield plate 35 and has the same diameter as the positioning hole 35b. A positioning protrusion 4h of the lower case 4 (see also FIG. 4) is inserted into the positioning hole 38c. This allows the second shield plate 38 to be positioned in a fixed position in the lower case 4 by arranging the second shield plate 38 inside the lower case 4.

[0052] The extending portion 38d is continuous with the shielding portion 38a, extends so as to be positioned below the circuit board 20, and is disposed stacked below the insulating plate 37. The extending portion 38d has a shape that is approximately one size smaller than the insulating plate 37, and protrudes outward from the shielding portion 38a so as to be flush with the shielding portion 38a. In other words, the insulating plate 37 is interposed between the extending portion 38d and the circuit board 20. The extending portion 38d is provided with a plurality of through-holes 38e that expose the bosses 4c to 4e of the lower case 4 upward. Some of the through-holes 38e are formed as holes that penetrate the extending portion 38d in the height direction (thickness direction). The remaining through-holes 38e are formed as U-shaped notches that are formed by cutting out the outer periphery of the extending portion 38d.

[0053] When assembling the induction cooker 1, for example, the second shield plate 38, the heat insulating plate 36, the insulating plate 37, and the first shield plate 35 are arranged in this order on the bottom wall 4a of the lower case 4. As a result, the heat insulating plate 36 and the insulating plate 37 are stacked on the upper side of the second shield plate 38, and the first shield plate 35 is stacked on the upper side of the insulating plate 36. In this case, the thickness of the insulating plate 37 is equal to the sum of the thicknesses of the heat insulating plate 36 and the first shield plate 35, so the upper surface of the insulating plate 37 and the upper surface of the first shield plate 35 are positioned approximately flush with each other.

[0054] Next, the circuit board 20 is placed on the lower case 4 so as to cover the upper surface of the insulating plate 37, and the operation board 27 is placed on the lower case 4, and the lower case 4 and the boards 20 and 27 are fixed together with screws. After that, the coil set 10 is placed on the lower case 4 so as to cover the upper surface of the first shield plate 35, and the lower case 4 and the coil set 10 are fixed together with screws. Finally, the upper case 5 with the top plate 6 attached is placed on the lower case 4, and the lower case 4 and the upper case 5 are fixed together with screws.

[0055] As a result, the first shield plate 35, the heat insulating plate 36, and the shield portion 38a of the second shield plate 38 are stacked and arranged below the heating coil 11, and the insulating plate 37 and the extending portion 38d of the second shield plate 38 are stacked and arranged below the circuit board 20. Furthermore, the first shield plate 35, the heat insulating plate 36, and the shield portion 38a of the second shield plate 38 are sandwiched between the bottom wall 4a of the casing 3 and the rib 12f of the coil bobbin 12. More specifically, the rib 12f is positioned inwardly and spaced apart from the inner peripheral edge 21b of the circuit board 20, and sandwiches the stacked first shield plate 35, the heat insulating plate 36, and the second shield plate 38 between the bottom wall 4a of the lower case 4. Furthermore, the circuit board 20, the insulating plate 37, and the extending portion 38d of the second shield plate 38 are sandwiched between the bottom wall 4a of the casing 3 and the support portion 12e of the coil bobbin 12. Here, sandwiching is not limited to a state in which the rib 12f abuts against the first shield plate 35 and the support portion 12e abuts against the circuit board 20, but may be a state in which they are located in the vicinity of each other.

[0056] In the induction cooker 1 configured in this manner, when magnetic flux generated from the heating coil 11 heads toward the bottom wall 4a of the casing 3, it is suppressed by the first shield plate 35 and the second shield plate 38. In particular, the second shield plate 38 has an extension portion 38d that extends below the circuit board 20. Therefore, the magnetic flux spreads radially outward from the heating coil 11, and even if it cannot be shielded by the first shield plate 35, it can be shielded by the extension portion 38d of the second shield plate 38. Therefore, leakage of magnetic flux from the bottom wall 4a of the casing 3 to the outside can be effectively suppressed.

[0057] On the other hand, leakage of heat generated from the heating coil 11 can be suppressed by the heat insulating plate 36, and leakage of heat generated from the electronic components 22 on the circuit board 20 can be suppressed by the insulating plate 37, which is thicker than the heat insulating plate 36. Moreover, the heat directed toward the bottom wall 4a via the heat insulating plate 36 and the insulating plate 37 is absorbed by the second shield plate 38, which has a large area and includes the shield portion 38a and the extension portion 38d, and is diffused throughout. Therefore, leakage of heat from the bottom wall 4a of the casing 3 to the outside can be effectively suppressed.

[0058] The induction cooker 1 configured as above has the following features.

[0059] Two shield plates 35 and 38 are arranged below the heating coil 11. This effectively prevents the magnetic flux generated from the heating coil 11 from leaking to the outside through the bottom wall 4a of the casing.

[0060] An insulating plate 36 is provided between the first shield plate 35 and the second shield plate 38. This prevents heat from the heating coil 11 from leaking to the outside from the bottom of the casing 3. Furthermore, by attaching the coil bobbin 12 to the casing 3, the first shield plate 35, the insulating plate 36, and the second shield plate 38 are sandwiched between the bottom wall 4a of the casing 3 and the coil bobbin 12. This eliminates the need for additional parts (mounting structures) to attach the first shield plate 35, the insulating plate 36, and the second shield plate 38. This allows the number of parts constituting the induction cooker 1 to be reduced, and the induction cooker 1 to be made thinner.

[0061] The second shield plate 38 includes an extension portion 38d extending to be positioned below the substrate main body 21. Specifically, the second shield plate 38 includes a shield portion 38a covering the underside of the heating coil 11 and an extension portion 38d extending outward from the shield portion 38a to cover the underside of the substrate main body 21. This more effectively prevents magnetic flux generated by the heating coil 11 from leaking out from the bottom of the casing 3. Furthermore, the second shield plate 38 including the extension portion 38d can absorb and dissipate heat from the multiple electronic components 22, as well as from the heating coil 11. Thus, the second shield plate 38 can both suppress magnetic flux leakage and dissipate heat received from the heating coil 11 and the electronic components 22 attached to the substrate main body 21, eliminating the need for separate dedicated components for each purpose. This reduces the number of components constituting the induction cooker 1 and allows the induction cooker 1 to be made thinner.

[0062] The casing 3 further includes an insulating plate 37 disposed between the board body 21 and the extending portion 38d, thereby ensuring the insulation of the circuit board 20 including the electronic components 22 and preventing the heat of the electronic components 22 from leaking to the outside through the bottom of the casing 3.

[0063] The present invention is not limited to the configuration of the above embodiment, and various modifications are possible.

[0064] For example, the heat insulating plate 36 may not be provided between the first shield plate 35 and the second shield plate 38. Furthermore, the first shield plate 35, the heat insulating plate 36, and the second shield plate 38 may not be sandwiched between the bottom wall 4 a of the casing 3 and the coil bobbin 12.

[0065] The second shield plate 38 may be configured with only the shield portion 38a without including the extension portion 38d. Also, the insulating plate 37 may not be provided between the second shield plate 38 and the circuit board 20. [Explanation of symbols]

[0066] 1 Induction cooker 3 Casing 4 Lower case 4a Bottom wall (bottom) 4b Surrounding wall 4c~4e boss 4F Rib 4g support part 4h Positioning protrusion 5 Upper case 5a Upper opening 5b Screw fastening part 6 Top Plate 7. Interior Space 10 coil set 11 Heating coil 12 Coil bobbin 12a Boss section 12b rim section 12c spokes 12d Screw fastening part 12e Support part 12th floor Rib 13 Ferrite core 14 Upper insulating plate 15 Center sensor 15a lead wire 16 Side sensor 16a lead wire 17 Center holder 18 Side holder 19. Hughes 19a lead wire 20 Circuit Board 21 Board body 21a Punching section 21b inner edge 22 Electronic Components 22A Diode Bridge 22B transistor 22C IC chip 22D capacitor 22E Switching Coil 23 Spacer 25 Control section 26 LCD display section 27 Operation board 28 Touch Switch 30 First Fan 31 Second Fan 32 Heat sink 35 First shield plate 35a through hole 35b Positioning hole 36 Insulation board 36a Through hole 36b Positioning hole 37 Insulating plate 37a inner edge 37b Notch 38 Second shield plate 38a Shield part 38b Through hole 38c Positioning hole 38d extension 38e Penetration

Claims

1. A casing; a heating coil disposed within the casing for induction heating an object to be heated disposed on the casing; a first shield plate disposed within the casing so as to be located below the heating coil; a second shield plate disposed below the first shield plate within the casing so as to be located below the heating coil; An induction cooker equipped with:

2. a coil bobbin supporting the heating coil; a heat insulating plate having heat insulating properties interposed between the first shield plate and the second shield plate; Further provided with The induction cooker according to claim 1, wherein the first shield plate, the heat insulating plate, and the second shield plate are sandwiched between the bottom of the casing and the coil bobbin by attaching the coil bobbin to the casing.

3. a circuit board disposed adjacent to the heating coil when viewed from above and having a plurality of electronic components mounted thereon for controlling the heating coil; The induction cooker according to claim 1 or 2, wherein the second shield plate includes an extending portion that extends to be positioned below the circuit board.

4. The induction cooker according to claim 3 , further comprising an insulating plate having heat insulation properties, arranged between the circuit board and the extension portion so as to be adjacent to the heating coil when viewed from above.

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