Heating element and cooking appliance

Abstract

A heating element according to the present disclosure comprises: a heating element layer that generates heat through a magnetic field; and an insulating layer that insulates the heating element layer. The heating element layer has a spiral-shaped first layer. A cooking appliance according to the present disclosure comprises: a body having a plate-shaped bottom section; and the heating element. The bottom section has a cooking surface and an outer surface positioned on the reverse side of the cooking surface. The heating element is attached to the outer surface.

Description

Heating element and cooking appliance

[0001] The present disclosure relates to a heating element and a cooking appliance.

[0002] As a cooking appliance for heating and cooking food, a cooking appliance compatible with an IH (Induction Heating) cooker is known. As such a cooking appliance, for example, there is a clay pot equipped with an IH heating element. This clay pot is sold on the market, but especially in the case of a clay pot equipped with a heating element in silver transfer, problems due to abnormal heating have occurred. Each company has taken measures such as providing a gap between the IH heating element and the IH cooker, but a fundamental solution has not been achieved.

[0003] Patent Document 1 describes a cooking container for an induction heating cooker (IH cooker). This cooking container includes a cooking container body formed of ceramics and a heating element layer provided on the outer wall bottom surface of the body, which can be heated by a high-frequency magnetic field generated by the induction heating cooker. The heating element layer is formed on the inner side of the outer wall bottom surface and on the outer side surrounding the inner side. Also, between the above-mentioned inner side and outer side, an insulating portion is provided that inhibits the concentration of eddy currents due to the high-frequency magnetic field and has a conductivity lower than a predetermined value.

[0004] Japanese Patent Application Laid-Open No. 2012-110636

[0005] The heating element according to the present disclosure includes a heating element layer that generates heat by a magnetic field and an insulating layer that insulates the heating element layer. The heating element layer has a spiral-shaped first layer.

[0006] The cooking appliance according to the present disclosure includes a main body having a plate-shaped bottom and the above-mentioned heating element. The bottom has a cooking surface and an outer surface located on the opposite side of the cooking surface. The heating element is attached to the outer surface.

[0007] This is a cross-sectional view showing a heating element (cooking appliance) of an embodiment not limited to the present disclosure. This is an enlarged view of the area around the heating element in the cooking appliance shown in Figure 1. This is a plan view of the first layer of the heating element shown in Figure 1, viewed from the cooking surface side. This is a plan view of the second layer of the heating element shown in Figure 1. This is a plan view of the first and second layers of the heating element shown in Figure 2, viewed from the V direction, showing the first and second vias in perspective. This is a plan view of a modified example of the heating element shown in Figure 5, showing the first and second vias in perspective. This is a plan view of another modified example of the heating element shown in Figure 5, showing the outer edge of the second layer in perspective. This is a plan view of another modified example of the heating element shown in Figure 5, showing the outer edge of the second layer in perspective. This is a cross-sectional view showing a heating element (cooking appliance) of another embodiment not limited to the present disclosure, corresponding to Figure 2. This is a plan view of the second layer of the heating element shown in Figure 9. This is a cross-sectional view showing a heating element (cooking appliance) of yet another embodiment not limited to the present disclosure, corresponding to Figure 2. This is a plan view of the second layer of the heating element shown in Figure 11, viewed from the cooking surface side. This is a diagram showing a heating element (cooking utensil) of yet another embodiment not limited to the present disclosure, which is a plan view of the first layer as seen from the cooking surface side, and corresponds to Figure 3. This is a plan view of a modified example of the heating element shown in Figure 13. This is a diagram showing a heating element (cooking utensil) of yet another embodiment not limited to the present disclosure, which is a plan view of the first layer as seen from the cooking surface side, and corresponds to Figure 3. This is a diagram showing a heating element (cooking utensil) of yet another embodiment not limited to the present disclosure, which is a plan view of the first layer as seen from the cooking surface side, and corresponds to Figure 3. This is a broken cross-sectional view taken along the line XVII-XVII shown in Figure 16. This is a plan view of a modified example of the heating element shown in Figure 16. This is a broken cross-sectional view taken along the line XIX-XIX shown in Figure 18. This is a diagram showing a heating element (cooking utensil) of yet another embodiment not limited to the present disclosure, which is a plan view of the first layer as seen from the cooking surface side, and corresponds to Figure 3. This is a schematic diagram showing the measurement points when measuring the temperature of the cooking surface in the embodiment.

[0008] The cooking container described in Patent Document 1 aims to improve abnormal temperature rise when the cooking container is placed in an incorrect position by making the heating element layer a separate donut shape rather than a solid shape. However, the heating is still dependent on the IH coil, and the amount of heat generated in the center where there is no IH coil is small, making it difficult for the overheat prevention sensor installed near the center to activate. In addition, the temperature difference is still large, raising concerns about further abnormal temperature rise due to scorching.

[0009] The real challenge lay in the localized heat generation that occurred during heating. Therefore, it is desirable to design the heating element so that a consistent, even heat distribution is maintained on the cooking surface, regardless of how the induction cooktop is placed.

[0010] This disclosure provides a heating element and cooking utensils that can improve the uniformity of heat distribution on cooking surfaces and the like.

[0011] The heating element and cooking utensils described herein can improve the uniformity of heat distribution on cooking surfaces and other surfaces.

[0012] Hereinafter, the heating element 1A and cooking appliance 101A of embodiments not limited to this disclosure will be described in detail with reference to the drawings. However, in the drawings referred to below, for the sake of convenience of explanation, only the main components necessary for describing the embodiments are shown in a simplified manner. Therefore, the heating element 1A and cooking appliance 101A may include any components not shown in the drawings referred to below. Furthermore, the dimensions of the components in each drawing do not faithfully represent the dimensions of the actual components or the dimensional ratios of each component. These points are also the same in other embodiments described later.

[0013] In Figure 1, a pot is shown as an example of a cooking utensil 101A. More specifically, an earthenware pot is shown as an example of a cooking utensil 101A. In addition to an earthenware pot, the cooking utensil 101A may also take the form of, for example, a frying pan, a container, a plate, or a ceramic plate. The cooking utensil 101A is, for example, a ceramic that can be used as tableware or a cooking utensil. Note that the cooking utensil 101A is not limited to the example shown.

[0014] The cooking appliance 101A comprises a main body 103 and a heating element 1A, as shown in the example in Figures 1 and 2.

[0015] The main body 103 has a plate-shaped bottom 105. The main body 103 may also be entirely concave. In the cooking utensil 101A, the main body 103 is a bottomed cylindrical shape. The surface of the main body 103 may also be coated with a glaze layer. Examples of materials for the main body 103 include materials containing clay and silica, materials containing clay and petalite, or ceramics, and materials for ceramics can be used.

[0016] The heating element 1A functions as a component that heats the main body 103, which is the object to be heated. The heating element 1A comprises a heating element layer 3 and an insulating layer 5.

[0017] The heating element layer 3 generates heat due to the magnetic field. In other words, the heating element layer 3 generates heat through Joule heating, which is caused by the induction of an eddy current (induced current) by the action of the magnetic field.

[0018] The magnetic field that generates heat in the heating element layer 3 may be generated by an IH appliance (electromagnetic appliance). In the cooking appliance 101A, the IH appliance is an IH cooker (induction cooker). Examples of IH cookers include IH stoves. In the cooking appliance 101A, the heating element layer 3 is heated by eddy currents generated by a magnetic field from a donut-shaped IH coil, for example. Examples of materials for such a heating element layer 3 include silver or silver containing glass.

[0019] The insulating layer 5 insulates the heating element layer 3. Examples of materials for the insulating layer 5 include glass.

[0020] The bottom portion 105 of the main body 103 has a cooking surface 107 and an outer surface 109. The cooking surface 107 is the surface for heating and cooking food using the heat applied from the heating element 1A. The outer surface 109 is the surface located on the opposite side of the cooking surface 107.

[0021] The heating element 1A is attached to the outer surface 109. The heating element 1A may be attached to the outer surface 109 by, for example, a glass firing process.

[0022] Here, the heating element layer 3 has a spiral-shaped first layer 7, as shown in the example in Figure 3. Because the first layer 7 is spiral-shaped, eddy currents generated by the magnetic field of the donut-shaped IH coil flow to the center of the first layer 7 as well. This increases the amount of heat generated in the center of the cooking surface 107. As a result, while there was a large temperature difference between the outer periphery and the center of the cooking surface 107 in conventional products, the temperature difference is reduced in the cookware 101A. Therefore, the heating element 1A and cookware 101A can improve the uniformity of the cooking surface 107. In addition, when the temperature in the center of the cooking surface 107 becomes high, the overheat prevention sensor located in the center of the IH cooktop is properly activated, ensuring safety.

[0023] As shown in the example in Figure 2, the imaginary straight line passing through the center 107a of the cooking surface 107 and the center 109a of the outer surface 109 is the central axis S1 of the base 105. In the cooking utensil 101A, the base 105 is disc-shaped. Also, the cooking surface 107 and the outer surface 109 are both circular. If the cooking surface 107 is polygonal, the diagonal corners of the cooking surface 107 may be connected by straight lines, and the intersection of these lines may be taken as the center 107a of the cooking surface 107. The starting point of the diagonal may be the point where the extensions of each side constituting the polygon intersect. The same applies to the center 109a of the outer surface 109.

[0024] The heating element layer 3 may further have a second layer 9, as shown in the example in Figure 2. The second layer 9 is adjacent to the first layer 7 via an insulating layer 5. In the cooking utensil 101A, the second layer 9 is adjacent to the first layer 7 via the insulating layer 5 in the direction along the central axis S1. The second layer 9 is either a flat surface or a spiral shape. In these cases, the heat generated by the second layer 9 in addition to that from the first layer 7 is also added, making it easier to improve the uniformity of the heat on the cooking surface 107. Note that the flat surface shape may also be referred to as a solid surface shape.

[0025] The heating element layer 3 described above can be manufactured using screen printing technology. Specifically, a sheet that will become the heating element layer 3 is produced by sequentially printing and laminating each layer (heating layer, insulating layer) using a screen printing plate having the desired shape. The heating element layer 3 can be provided on the bottom 105 of a pot or the like by attaching the sheet that will become the heating element layer 3 to the bottom 105 using a water transfer method or the like, and then firing it. The bottom 105 may also be coated with a glaze layer, and the heating element layer 3 is provided on top of the glaze layer.

[0026] In the cooking appliance 101A, the second layer 9 of the heating element 1A is planar in shape and is located closer to the bottom 105 than the first layer 7 (see Figures 2 and 4). In this case, the spiral-shaped first layer 7 is located near the temperature sensor of the induction cooktop, allowing the temperature sensor to detect the temperature more accurately.

[0027] In the cooking utensil 101A, as shown in the example in Figure 2, the second layer 9 is in contact with the outer surface 109 of the bottom 105. Also, the side of the first layer 7 furthest from the outer surface 109 is covered by the outermost insulating layer 5. In the cooking utensil 101A, there may be an insulating layer between the second layer 9 and the outer surface 109 of the bottom 105. Furthermore, if the outer surface 109 is coated with a glaze layer, there may be an insulating layer on the glaze layer.

[0028] The spiral shape in the first layer 7 has a first end 7a and a second end 7b, as shown in the example in Figure 3. The first end 7a is the end closest to the center S2 of the spiral shape. The second end 7b is the end furthest from the center S2. The spiral shape in the first layer 7 extends continuously from the first end 7a to the second end 7b. The first end 7a is located below the center of the cooking surface 107. The first end 7a corresponds to the center of the first layer 7.

[0029] The center S2 of the spiral shape can be defined as follows: The outer periphery 11 of the first layer 7 has an arc shape at its outer edge 11a. The center of this arc shape is the center S2 of the spiral shape. Note that the outer periphery 11 of the first layer 7 is the outermost part of the first layer 7. Therefore, the outer periphery 11 described above may also be referred to as the outermost periphery 11. Furthermore, the center S2 of the spiral shape may be located on the central axis S1 of the bottom 105 (see Figure 2). The center 9a of the second layer 9 may also be located on the central axis S1 (see Figures 2 and 4).

[0030] The first end portion 7a may be located away from the center S2 of the spiral shape, as shown in the example in Figure 3. The spiral shape in the first layer 7 extends continuously from the first end portion 7a to the second end portion 7b, surrounding the center S2 of the spiral shape, allowing eddy currents to be introduced near the center S2 and increasing the amount of heat generated.

[0031] The heating element 1A may further include vias 13, as shown in the example in Figure 2. The vias 13 are located between the first layer 7 and the second layer 9. The vias 13 also electrically connect the first layer 7 and the second layer 9. The vias 13 may also be referred to as connection points.

[0032] Examples of materials for via 13 include silver or silver containing glass. The material of via 13 may be the same as the material of the heating element layer 3.

[0033] Via 13 has a first via 15 and a second via 17. In the heating element 1A, as shown in the example in Figure 5, when the first layer 7 is viewed from above, the first via 15 is located at the first end 7a. Also, when the first layer 7 is viewed from above, the second via 17 is located at the second end 7b.

[0034] In heating element 1A', a modified version of heating element 1A, as shown in the example in Figure 6, when the first layer 7 is viewed from above, the first via 15 is located near the first end 7a. Also, when the first layer 7 is viewed from above, the second via 17 is located near the second end 7b. Note that the positional relationship between the first via 15 and the second via 17 may be confirmed by viewing the second layer 9 from above instead of viewing the first layer 7 from above.

[0035] By providing the first via 15 and the second via 17 described above, the induced current can easily circulate infinitely between the first layer 7 and the second layer 9. Furthermore, if vias 13 are present in the center and on the outer periphery, a path for the current is created, making it easier to guide the eddy currents generated in the outer periphery 11 of the first layer 7 to the center. As a result, the uniformity of the heat distribution on the cooking surface 107 can be further improved.

[0036] The diameter of via 13 is not limited to a specific value. For example, the diameter of the first via 15 may be set to 5 to 24 mm. Similarly, the diameter of the second via 17 may be set to 5 to 24 mm.

[0037] The diameters of the first via 15 and the second via 17 are set to a value that does not exceed the width W of the spiral wire 7c in the spiral shape of the first layer 7, as shown in the example in Figure 5. The width W may be set to, for example, 5 to 24 mm. In the heating element 1A, the width W is constant.

[0038] The width W is not limited to a specific value. If the diameter of the cooking surface 107 or the number of turns in the spiral shape changes, the width W will change accordingly. For example, the number of turns in the spiral shape may be set to 3 to 7. Also, the pitch P in the spiral shape may be set to 0.5 to 3.0 mm. The diameter of the cooking surface 107 may be set to 12 to 30 cm.

[0039] If the second layer 9 is a planar shape, as shown in the example in Figure 5, the outer edge 9b of the second layer 9 may overlap with the outer edge 11a of the outer periphery 11 of the first layer 7 in a plan view. More specifically, when viewed from the side of the outer surface 109 along the central axis S1, the outer edge 9b of the second layer 9 may overlap with the outer edge 11a of the outer periphery 11 of the first layer 7. The plan view described above is a concept that includes planar perspective.

[0040] When the outer edge 9b of the second layer 9 overlaps with the outer edge 11a of the outer periphery 11 of the first layer 7, the heating element 1A does not shift significantly relative to the induction cooktop. Therefore, abnormal heat generation is less likely to occur.

[0041] When manufacturing the second layer 9 so that its outer edge 9b overlaps with the outer edge 11a of the outer periphery 11 of the first layer 7, there may be a slight misalignment between the two outer edges. Even in such cases, it is sufficient that the outer edge 9b of the second layer 9 overlaps with at least a portion of the second via 17. Therefore, the term "overlapping" as described above is not limited to a strictly overlapping configuration, but rather means that a slight misalignment between the outer edge 9b of the second layer 9 and the outer edge 11a of the outer periphery 11 of the first layer 7 is permitted. Furthermore, if the outer edge 9b of the second layer 9 does not overlap with the second via 17, the dielectric current will not easily circulate infinitely between the first layer 7 and the second layer 9, and there is a risk of abnormal heat generation. Specific examples of cases where the outer edges of the two are slightly misaligned will be explained below using Figures 7 and 8.

[0042] As shown in the example in Figure 7, in heating element 1A'', which is another modified example of heating element 1A, the distance between the center of the spiral shape S2 in the first layer 7 and the center 9a of the second layer 9 (the center displacement) and the diameter of the second via 17 satisfy the relationship (center displacement) ≤ (diameter of the second via 17). When there is no displacement at the outer edges of the two, the center 9a of the second layer 9 coincides with the center of the spiral shape S2 in the first layer 7 (see Figure 5). If the center displacement from this state satisfies the above-mentioned magnitude relationship, abnormal heat generation is unlikely to occur. Therefore, when the above-mentioned magnitude relationship is satisfied, it may be considered that the outer edges of the two "overlap".

[0043] Furthermore, as shown in the example in Figure 8, in heating element 1A''', which is another modified version of heating element 1A, the center 9a of the second layer 9 is located within a virtual circle C with the center S2 of the spiral shape in the first layer 7 as the center, and the radius being the diameter of the second via 17. In this case as well, abnormal heat generation is unlikely to occur. Therefore, even when the above-described positional relationship is satisfied, it may be considered that the outer edges of the two "overlap".

[0044] Note that in the heating element 1A, as shown in an example in FIG. 5, the second layer 9 is circular. Further, as described above, in the outer peripheral portion 11 of the first layer 7, the outer edge 11a has an arc shape. The diameter of the first layer 7 is the diameter of the circumcircle that contacts the outer peripheral portion 11 of the first layer 7. In the example shown in FIG. 5, the outer edge 9b of the second layer 9 corresponds to the above-described circumcircle. Therefore, in the heating element 1A, the diameter of the second layer 9 is the same as the diameter of the first layer 7. The diameter of the second layer 9 may be set to, for example, 12 to 25 cm.

[0045] The thickness of the heating element layer 3 and the thickness of the insulating layer 5 are not limited to specific values. For example, in an example shown in FIG. 2, the thickness D of the spiral wire 7c having a spiral shape in the first layer 7 may be set to 1 to 30 μm. Further, the thickness of the second layer 9 may be set to 1 to 30 μm. The thickness of the insulating layer 5 located between the first layer 7 and the second layer 9 may be set to 5 to 55 μm. The thickness of the insulating layer 5 located outermost may be set to 1 to 30 μm. Note that in the heating element 1A, the thickness D is constant. Also, the thickness of the second layer 9 is constant.

[0046] The cooking appliance 101A may further include a lid 111 that closes the opening of the main body 103, as shown in an example in FIG. 1. The surface of the lid 111 may be coated with an enamel layer. Examples of the material of the lid 111 include materials containing clay and silica, materials containing clay and petalite, or ceramics, and materials for ceramics can be used.

[0047] Next, the heating element 1B and the cooking appliance 101B of another non-limiting embodiment of the present disclosure will be described. Hereinafter, the differences between the heating element 1B (cooking appliance 101B) and the heating element 1A (cooking appliance 101A) will be mainly described, and detailed description of the points having the same configuration as the heating element 1A (cooking appliance 101A) may be omitted. Therefore, the description regarding the heating element 1A (cooking appliance 101A) may be incorporated to understand the configuration of the heating element 1B (cooking appliance 101B). This point is the same in other embodiments described later.

[0048] In the cooking appliance 101B, as shown in an example in FIGS. 9 and 10, the second layer 9 in the heating element 1B has a planar shape and is located farther from the bottom 105 than the first layer 7.

[0049] Also in this embodiment, the same effects as those of the above-described embodiment can be obtained. That is, the spiral-shaped first layer 7 controls the flow of eddy currents generated by the magnetic field of the IH coil, and the calorific value at the center of the cooking surface 107 can be increased. As a result, while the temperature difference between the outer peripheral portion and the central portion of the cooking surface 107 was large in the conventional product, the temperature difference is small in the cooking appliance 101B. Therefore, according to the heating element 1B and the cooking appliance 101B, the heat uniformity of the cooking surface 107 can be improved. Further, the over-temperature prevention sensor existing in the center of the IH cooker can be activated correctly, and safety can be ensured.

[0050] Furthermore, when another object hits or scratches the heating element layer 3 which is the transfer surface during actual use, if the layer relatively far from the bottom 105 has a spiral shape, there is a risk of disconnection. In the cooking appliance 101B, since the layer relatively far from the bottom 105 has a planar shape (solid shape), the risk of disconnection of the spiral-shaped first layer 7 can be reduced.

[0051] In the cooking appliance 101B, as shown in an example in FIG. 9, the first layer 7 contacts the outer surface 109 of the bottom 105. Also, the surface of the second layer 9 on the side far from the outer surface 109 is covered by the insulating layer 5 located at the outermost part. In the cooking appliance 101B, an insulating layer may be provided between the first layer 7 and the outer surface 109 of the bottom 105. Also, when the outer surface 109 is coated with a glaze layer, an insulating layer may be provided on the glaze layer.

[0052] Other configurations are the same as those of the above-described heating element 1A and cooking appliance 101A, and thus the description thereof is omitted.

[0053] Next, the heating element 1C and the cooking appliance 101C according to still another embodiment not limiting the present disclosure will be described.

[0054] In the cooking appliance 101C, as shown in an example in FIGS. 11 and 12, the second layer 9 in the heating element 1C has a spiral shape.

[0055] In this embodiment as well, the same effects as in the above-described embodiment can be obtained. That is, when the second layer 9 has a spiral shape, the effect of inducing current to the center by the spiral shape can be ensured by both the first layer 7 and the second layer 9. For example, even if the heating element 1C is placed offset from the induction cooktop, the heating pattern does not change easily. Due to the effect of the spiral shape, even if the positional relationship with the induction cooktop is shifted, the current flows to the center and the entire surface can be heated. Therefore, the heating element 1C and the cooking appliance 101C can improve the uniformity of the cooking surface 107.

[0056] In the example shown in Figure 11, the first layer 7 is in contact with the outer surface 109 of the bottom 105, and the side of the second layer 9 furthest from the outer surface 109 is covered by the outermost insulating layer 5. However, the positions of the first layer 7 and the second layer 9 may be reversed. That is, the second layer 9 may be in contact with the outer surface 109, and the side of the first layer 7 furthest from the outer surface 109 may be covered by the outermost insulating layer 5. In the example shown in Figure 11, there may be an insulating layer between the first layer 7 and the outer surface 109 of the bottom 105. Also, if the positions of the first layer 7 and the second layer 9 are reversed, there may be an insulating layer between the second layer 9 and the outer surface 109 of the bottom 105. Furthermore, if the outer surface 109 is coated with a glaze layer, there may be an insulating layer on the glaze layer.

[0057] The direction of rotation of the spiral shape in the second layer 9 may be directly opposite to the direction of rotation of the spiral shape in the first layer 7 (see Figures 3 and 12). If the direction of rotation of the spiral shape in the second layer 9 is the same as the direction of rotation of the spiral shape in the first layer 7, the current directions in the first layer 7 and the second layer 9 are directly opposite and cancel each other out, resulting in less heat generation. If the direction of rotation of the spiral shape in the second layer 9 is directly opposite to the direction of rotation of the spiral shape in the first layer 7, the current directions in the first layer 7 and the second layer 9 are aligned, so cancellation does not occur, and heat generation is more likely.

[0058] The direction of rotation of the spiral shape is the direction of rotation from the center S2 of the spiral shape. In the heating element 1C, when viewed from the cooking surface 107 side in a plan view, the direction of rotation of the spiral shape in the second layer 9 is clockwise, and the direction of rotation of the spiral shape in the first layer 7 is counterclockwise. Alternatively, the direction of rotation of the spiral shape in the second layer 9 may be counterclockwise, and the direction of rotation of the spiral shape in the first layer 7 may be clockwise.

[0059] In the heating element 1C, the outer edge of the outer periphery of the second layer 9 is arc-shaped, and the center of this arc shape is the center S2 of the spiral shape in the second layer 9. Note that when the second layer 9 is spiral-shaped, the configuration of the second layer 9 other than those described above may be the same as that of the first layer 7.

[0060] The other components are the same as those described above for the heating elements 1A and 1B and the cooking appliances 101A and 101B, so their explanation will be omitted.

[0061] Next, a heating element 1D and a cooking appliance 101D of yet another embodiment not limited to the present disclosure will be described.

[0062] In the cooking appliance 101D, as shown in the example in Figure 13, in the heating element 1D, the width W of the spiral-shaped spiral wire 7c in the first layer 7 is narrower on the first end 7a side than on the outer circumference 11 side.

[0063] The amount of heat generated by the heating element layer 3 is determined by the following factors: (1) the resistance of the heating element layer 3, (2) the amount of induced current, and (3) the cross-sectional area of ​​the heating element layer 3.

[0064] By changing the width W, the central part (3) can be altered, thereby increasing the heat output. As a result, further improvements in heat uniformity can be achieved. For example, if the heat output is insufficient in a certain part of the cooking surface 107, it is possible to increase the heat output and improve overall heat uniformity by narrowing the width W corresponding to that location.

[0065] The width W on the outer circumference 11 side may be set to 15 to 25 mm. The width W on the first end 7a side may be set to 5 to 15 mm. For example, the width W on the outer circumference 11 side may be set to 20 mm and the width W on the first end 7a side may be set to 10 mm.

[0066] In heating element 1D', a modified version of heating element 1D, the width W gradually narrows towards the first end 7a, as shown in the example in Figure 14. In this case, the amount of heat generated changes gradually towards the first end 7a, which further improves the overall uniformity of heating.

[0067] In the heating element 1D', the width W at locations a to e along the radial direction of the spiral shape (first layer 7) may be set as follows, starting from the side closest to the center S2 of the spiral shape: a: 5 to 10 mm b: 7 to 13 mm c: 7 to 13 mm d: 11 to 17 mm e: 18 to 24 mm

[0068] In the heating element 1D', for example, the width W at locations a to e may be set as follows: a: 9.3 mm b: 10.0 mm c: 10.0 mm d: 14.0 mm e: 21.0 mm

[0069] Furthermore, the spiral shape in the first layer 7 may have a tapered region, as will be described later. In this case, the width W on the outer circumference 11 will be the value excluding the tapered region. Also, as mentioned above, the width W is not limited to a specific value. If the diameter of the cooking surface 107 or the number of turns in the spiral shape changes, the width W will change accordingly. In the cooking appliance 101D, the diameter of the cooking surface 107 is 18 cm and the number of turns is 5. In addition, in the heating element 1D', as an example, the pitch P in the spiral shape may be set to 1.5 mm.

[0070] The other components are the same as those described above for the heating elements 1A to 1C and cooking appliances 101A to 101C, so their explanation will be omitted.

[0071] Next, a heating element 1E and a cooking appliance 101E of yet another embodiment not limited to the present disclosure will be described.

[0072] In the cooking appliance 101E, as shown in the example in Figure 15, the spiral shape of the first layer 7 of the heating element 1E has a tapered region 19. The tapered region 19 is located from the vicinity of the second end 7b to the second end 7b. In the tapered region 19, the width W gradually narrows towards the second end 7b. For ease of visual understanding, the tapered region 19 is shaded in Figure 15.

[0073] When the first layer 7 and the second layer 9 of the heating element layer 3 are stacked, there may be some areas where only one layer is present (see Figure 5). When this configuration is heated by induction heating, the area with only one layer will have a relatively higher heat output compared to the area with two layers stacked.

[0074] The amount of heat generated by the heating element layer 3 is determined by the following factors, as described above: (1) the resistance of the heating element layer 3, (2) the amount of induced current, and (3) the cross-sectional area of ​​the heating element layer 3.

[0075] In the single-layer portion, (3) is smaller compared to the double-layer portion, resulting in a greater heat generation. When the spiral shape of the first layer 7 has the tapered region 19 described above, the area with only one layer can be reduced. This allows for further improvement of heat uniformity.

[0076] The other components are the same as those described above for the heating elements 1A to 1D and cooking appliances 101A to 101D, so their explanation will be omitted.

[0077] Next, a heating element 1F and a cooking appliance 101F of yet another embodiment not limited to the present disclosure will be described.

[0078] In the cooking appliance 101F, as shown in the example in Figures 16 and 17, the thickness D of the spiral-shaped spiral wire 7c in the first layer 7 of the heating element 1F differs between the outer circumference 11 side and the first end 7a side.

[0079] The amount of heat generated by the heating element layer 3 is determined by the following factors, as described above: (1) the resistance of the heating element layer 3, (2) the amount of induced current, and (3) the cross-sectional area of ​​the heating element layer 3.

[0080] Controlling the thickness of the heating element layer 3 changes the cross-sectional area of ​​the heating element layer 3. In other words, if the thickness of the heating element layer 3 is reduced and the cross-sectional area is decreased, the amount of heat generated increases. By utilizing this, for example, by reducing the thickness D on the side of the first end 7a near the center S2 of the spiral shape, the amount of heat generated is relatively increased, thereby further reducing the temperature difference between the center and the outer periphery.

[0081] In the heating element 1F, the thickness D on the side of the first end 7a is thinner than the thickness D on the side of the outer circumference 11. More specifically, the thickness D gradually decreases towards the side of the first end 7a. In the heating element 1F, the thickness D at locations a to e along the radial direction of the spiral shape (first layer 7), starting from the side closest to the center S2 of the spiral shape, may be set as follows: a: 2 to 8 μm b: 4 to 10 μm c: 7 to 13 μm d: 10 to 16 μm e: 12 to 18 μm

[0082] In the heating element 1F, for example, the thickness D at locations a to e may be set as follows: a: 5 μm b: 7 μm c: 10 μm d: 13 μm e: 15 μm

[0083] In the heating element 1F, the width W is constant, as shown in the example in Figure 16. In heating element 1F', a modified version of heating element 1F, the width W is narrower on the side of the first end 7a than on the side of the outer circumference 11, as shown in the example in Figure 18. More specifically, the width W gradually narrows towards the first end 7a. In heating element 1F', as an example, the width W at locations a1 to e1 along the radial direction of the spiral shape (first layer 7) may be set as follows: a1: 9.3 mm b1: 10.0 mm c1: 11.0 mm d1: 14.0 mm e1: 21.0 mm

[0084] In the heating element 1F', as shown in the example in Figure 19, the thickness D on the side of the first end 7a is thinner than the thickness D on the side of the outer circumference 11. More specifically, the thickness D gradually decreases toward the side of the first end 7a. In the heating element 1F', the thickness D at locations a to e along the radial direction of the spiral shape (first layer 7) may be set as follows: a: 2 to 8 μm b: 4 to 10 μm c: 7 to 13 μm d: 10 to 16 μm e: 12 to 18 μm

[0085] In the heating element 1F', for example, the thickness D at locations a to e may be set as follows: a: 5 μm b: 7 μm c: 10 μm d: 13 μm e: 15 μm

[0086] The other components are the same as those described above for the heating elements 1A to 1E and cooking appliances 101A to 101E, so their explanation will be omitted.

[0087] Next, we will describe a heating element 1G and a cooking appliance 101G of yet another embodiment not limited to the present disclosure.

[0088] In the cooking appliance 101G, as shown in the example in Figure 20, in the heating element 1G, the width W of the spiral-shaped spiral wire 7c in the first layer 7 changes from the side of the first end 7a to the side of the outer circumference 11, becoming thicker and then becoming thinner.

[0089] Depending on the induction cooktop used, the diameter of the first layer 7 may be larger than the diameter of the donut-shaped induction coil. In this case, the outer periphery 11 of the first layer 7 will extend beyond the outer edge of the induction coil. Since less current is induced in the outer periphery 11 that extends beyond the outer edge of the induction coil, the amount of heat generated tends to be less compared to the part located inside the outer edge of the induction coil. Therefore, it is difficult to ensure uniform heating throughout the entire surface.

[0090] When the width W of the spiral wire 7c changes as described above, the resistance increases on the outer peripheral portion 11 that extends beyond the outer edge of the IH coil due to the narrowing of the width W, thus compensating for the insufficient current and ensuring sufficient heat generation. Furthermore, in the portion located inside the outer edge of the IH coil, in addition to the induction of current to the center due to the spiral shape, the resistance increases near the center due to the narrowing of the width W, thus ensuring sufficient heat generation in the same way as on the outer peripheral portion 11. Therefore, with the heating element 1G and cooking appliance 101G, it is possible to improve overall heat uniformity when the diameter of the first layer 7 is larger than the diameter of the donut-shaped IH coil.

[0091] In the heating element 1G, the width W at locations a to g along the radial direction of the spiral shape (first layer 7) may be set as follows, starting from the side closest to the center S2 of the spiral shape: a: 5 to 10 mm b: 7 to 13 mm c: 7 to 13 mm d: 11 to 17 mm e: 18 to 24 mm f: 17 to 21 mm g: 8 to 12 mm

[0092] For example, in the heating element 1G, the width W at locations a to g may be set as follows: a: 9.25 mm b: 11 mm c: 11 mm d: 17 mm e: 22 mm f: 19 mm g: 10 mm

[0093] The other components are the same as those described above for the heating elements 1A to 1F and cooking appliances 101A to 101F, so their explanation will be omitted.

[0094] While the embodiments described above are examples of those relating to this disclosure, it goes without saying that this disclosure is not limited to the embodiments described above, and any embodiments can be used as long as they do not deviate from the gist of this disclosure.

[0095] For example, the heating element (cooking appliance) according to this disclosure is not limited to the respective heating elements 1A to 1G (cooking appliances 101A to 101G) according to the above-described embodiment, but may also be a heating element (cooking appliance) according to an embodiment that combines the heating elements (cooking appliances) according to each embodiment.

[0096] Furthermore, although the above-described embodiment explained the case where the heating element is used in a cooking appliance, the heating element can be applied to other uses as well. Other uses include, for example, home appliances.

[0097] Furthermore, the heating element and cooking appliance according to this disclosure may have the following configurations: [1] The heating element comprises a heating element layer that generates heat in a magnetic field and an insulating layer that insulates the heating element layer, wherein the heating element layer has a spiral-shaped first layer. [2] The heating element according to [1] further comprises a second layer adjacent to the first layer via the insulating layer, wherein the second layer may be planar or spiral-shaped. [3] The heating element according to [2] has a spiral shape for the second layer, and the direction of rotation of the spiral shape in the second layer may be directly opposite to the direction of rotation of the spiral shape in the first layer. [4] The heating element according to any one of [1] to [3] has a spiral shape in the first layer that has a first end closer to the center of the spiral shape and a second end further from the center, and the width of the spiral wire of the spiral shape in the first layer may be narrower on the first end side than on the outer circumference side. [5] Any one of the heating elements described in [2] to [4] above may have a spiral shape in the first layer that includes a first end near the center of the spiral shape, a second end far from the center, and a tapered region located near the second end and extending toward the second end, with the width gradually decreasing toward the second end. [6] Any one of the heating elements described in [2] to [5] above may have a spiral shape in the first layer that includes a first end near the center of the spiral shape and a second end far from the center, and further includes vias located between the first layer and the second layer that electrically connect the first layer and the second layer, wherein the vias may include a first via located at or near the first end when the first layer is viewed through a plane, and a second via located at or near the second end when the first layer is viewed through a plane. [7] Any one of the heating elements described in [2] to [6] above may have a second layer that is planar in shape, and in plan view, the outer edge of the second layer may overlap with the outer edge of the outer periphery of the first layer. [8] Any one of the heating elements described in [1] to [7] above has a spiral shape in the first layer that has a first end closer to the center of the spiral shape and a second end further from the center, and the thickness of the spiral wire of the spiral shape in the first layer may differ on the outer circumference side and on the first end side.[9] The cooking utensil comprises a main body having a plate-shaped bottom and one of the heating elements described in [1] to [8] above, wherein the bottom has a cooking surface and an outer surface located opposite to the cooking surface, and the heating element is attached to the outer surface.

[10] In the cooking utensil of [9] above, a virtual straight line passing through the center of the cooking surface and the center of the outer surface is the central axis of the bottom, and the heating element layer further has a second layer adjacent to the first layer via the insulating layer in a direction along the central axis, and the second layer may be planar or spiral in shape.

[11] In the cooking utensil of

[10] above, the second layer may be planar and located closer to the bottom than the first layer.

[12] In the cooking utensil of

[10] above, the second layer may be planar and located further from the bottom than the first layer.

[13] In the cooking utensil of

[10] above, the second layer may be spiral in shape.

[0098] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to the following examples.

[0099] (Example 1) The temperature of the cooking surface 107 was measured for the heating element 1A and cooking utensil 101A described above (see Figure 2).

[0100] The specific configuration of the heating element 1A and the cooking utensil 101A is as follows: Material of the main body 103: Ceramic material consisting of 50% clay, 47% petalite, and 3% sodium silicate by weight. Material of the heating element layer 3: Silver Material of the insulating layer 5: Glass Material of the via 13: Silver Shape of the cooking surface 107: Circular shape with a diameter of 20 cm Width W of the spiral wire 7c in the spiral shape of the first layer 7: 2 cm Pitch P in the spiral shape: 0.5 mm Number of turns in the spiral shape: 6 Diameter of the second layer 9 (diameter of the first layer 7): 16 cm Thickness D of the spiral wire 7c in the spiral shape of the first layer 7: 5 μm Thickness of the second layer 9: 5 μm Thickness of the insulating layer 5 located between the first layer 7 and the second layer 9: 50 μm Thickness of the outermost insulating layer 5: 20 μm Others: The configuration other than those described above is shown in Figures 1 to 5.

[0101] The method for measuring the temperature is as follows: 1. Place the earthenware pot (cooking utensil 101A) with the lid 111 removed on the induction cooktop. 2. Fix the thermographic camera on a tripod directly above the earthenware pot (cooking surface 107). 3. Turn on the induction cooktop and start heating. Heating will be performed under the conditions of 1000W x 5 minutes. 4. Stop heating and measure the temperature of the cooking surface 107.

[0102] The induction cooktop used was one equipped with a donut-shaped induction coil. The diameter of this induction coil was 16.4 cm. A FLIR E53 thermograph was used. The thermograph was fixed at a distance of 50 cm from the measurement surface (cooking surface 107). As shown in Figure 21, nine measurement points (Sp1 to Sp9) were set at equal intervals along the radial direction of the cooking surface 107. Sp5 is located at the center 107a of the cooking surface 107.

[0103] The measurement results are as follows: Sp1: 252.3°C, Sp2: 295.3°C, Sp3: 319.6°C, Sp4: 304.2°C, Sp5: 289.8°C, Sp6: 311.7°C, Sp7: 320.3°C, Sp8: 297.6°C, Sp9: 281.7°C

[0104] (Example 2) The temperature of the cooking surface 107 was measured for the heating element 1B and cooking utensil 101B described above (see Figure 9). The configuration of the heating element 1B and cooking utensil 101B is the same as in Example 1, except that the first layer 7 and the second layer 9 are configured as shown in Figures 9 and 10. The method of measuring the temperature is also the same as in Example 1.

[0105] The measurement results are as follows: Sp1: 280.7°C, Sp2: 335.5°C, Sp3: 354.1°C, Sp4: 345.5°C, Sp5: 325.1°C, Sp6: 349.9°C, Sp7: 361.7°C, Sp8: 346.5°C, Sp9: 324.4°C

[0106] (Example 3) The temperature of the cooking surface 107 was measured for the heating element 1C and cooking utensil 101C described above (see Figure 11). The configuration of the heating element 1C and cooking utensil 101C is the same as in Example 1, except that the first layer 7 and the second layer 9 are configured as shown in Figures 11 and 12. The method of measuring the temperature is also the same as in Example 1.

[0107] The measurement results are as follows: Sp1: 234.5°C, Sp2: 349.2°C, Sp3: 361.8°C, Sp4: 337.3°C, Sp5: 322.7°C, Sp6: 332.4°C, Sp7: 350.2°C, Sp8: 328.0°C, Sp9: 215.4°C

[0108] Furthermore, a thermal image of the cooking surface 107 of the cooking appliance 101C was obtained. Specifically, the heating conditions were the same as in Example 1, except that the heating conditions were changed from 1000W x 5 minutes to 900W x 3 minutes, and a thermal image of the cooking surface 107 after heating was obtained. A total of five thermal images were obtained: one when the heating element 1C was placed without being moved relative to the induction cooktop, and two when it was shifted by 2 cm in each direction (up, down, left, and right). Observation of the obtained thermal images confirmed that even when the positional relationship with the induction cooktop was shifted, the current flowed to the center, and the uniform heating was improved by heating the entire surface.

[0109] (Example 4) For the cooking utensils 101A to 101C in Examples 1 to 3, the difference between the highest temperature on the outer periphery of the cooking surface 107 and the temperature of the center 107a of the cooking surface 107 was calculated. Specifically, the measurement results of Sp1 to Sp9 were applied to the formula: (highest temperature among Sp1 to Sp4 and Sp6 to Sp9) - (Sp5) to calculate ΔT (°C). For example, in Example 1, the highest temperature among Sp1 to Sp4 and Sp6 to Sp9 is 320.3°C at Sp7. Also, Sp5 is 289.8°C. Therefore, ΔT calculated from the formula: 320.3°C - 289.8°C is 30.5°C.

[0110] As a comparative example, a cooking utensil with the same configuration as cooking utensil 101A was prepared, except that the first layer 7 was omitted and the heating element layer 3 was composed only of the second layer 9, which has a surface shape (solid shape), and the vias 13 were omitted. Using this cooking utensil, the temperature of the cooking surface 107 was measured using the same measurement method as in Example 1, and ΔT (°C) was calculated.

[0111] ΔT (°C) is as follows. Note that the value of ΔT (°C) is an absolute value. ΔT may be 100°C or less, or 50°C or less. Comparative example: 164°C Cooking utensil 101A: 30.5°C Cooking utensil 101B: 36.6°C Cooking utensil 101C: 39.1°C

[0112] 1A... Heating element 1B... Heating element 1C... Heating element 1D... Heating element 1E... Heating element 1F... Heating element 1G... Heating element 3... Heating element layer 5... Insulating layer 7... First layer 7a... First end 7b... Second end 7c... Spiral wire 9... Second layer 9a... Center 9b... Outer edge 11... Outer periphery 11a... Outer edge 13... Via 15... First via 17... Second via 19... Tapered region 101A... Cooking utensil 101B... Cooking utensil 101C... Cooking utensil 101D... Cooking utensil 101E... Cooking utensil 101F... Cooking utensil 101G... Cooking utensil 103... Main body 105... Bottom 107... Cooking surface 107a... Center 109...Outer surface 109a...Center 111...Lid S1...Central axis S2...Center W...Width D...Thickness P...Pitch C...Virtual circle

Claims

1. A heating element comprising a heating element layer that generates heat in response to a magnetic field, and an insulating layer that insulates the heating element layer, wherein the heating element layer has a spiral-shaped first layer.

2. The heating element according to claim 1, wherein the heating element layer further comprises a second layer adjacent to the first layer via the insulating layer, and the second layer is planar or spiral in shape.

3. The heating element according to claim 2, wherein the second layer is spiral-shaped, and the direction of rotation of the spiral shape in the second layer is directly opposite to the direction of rotation of the spiral shape in the first layer.

4. The heating element according to any one of claims 1 to 3, wherein the spiral shape in the first layer has a first end closer to the center of the spiral shape and a second end further from the center, and the width of the spiral wire of the spiral shape in the first layer is narrower on the side of the first end than on the side of the outer circumference.

5. The heating element according to any one of claims 2 to 4, wherein the spiral shape in the first layer has a first end close to the center of the spiral shape, a second end far from the center, and a tapered region located near the second end and extending to the second end, with the width gradually narrowing toward the second end.

6. The heating element according to any one of claims 2 to 5, wherein the spiral shape in the first layer has a first end closer to the center of the spiral shape and a second end further away from the center, and further comprises vias located between the first layer and the second layer and electrically connecting the first layer and the second layer, wherein the vias have a first via located at or near the first end when the first layer is viewed through a plane, and a second via located at or near the second end when the first layer is viewed through a plane.

7. The heating element according to any one of claims 2 to 6, wherein the second layer has a planar shape, and in a plan view, the outer edge of the second layer overlaps with the outer edge of the outer periphery of the first layer.

8. The heating element according to any one of claims 1 to 7, wherein the spiral shape in the first layer has a first end closer to the center of the spiral shape and a second end further from the center, and the thickness of the spiral wire of the spiral shape in the first layer differs on the outer circumference side and on the first end side.

9. The heating element according to claim 1, wherein the spiral shape in the first layer has a first end closer to the center of the spiral shape and a second end further from the center, and the width of the spiral wire of the spiral shape in the first layer changes so that it becomes thicker from the side of the first end to the outer circumference and then becomes thinner.

10. A cooking appliance comprising a main body having a plate-shaped bottom, and a heating element according to any one of claims 1 to 8, wherein the bottom has a cooking surface and an outer surface located opposite to the cooking surface, and the heating element is attached to the outer surface.

11. The cooking utensil according to claim 10, wherein a virtual straight line passing through the center of the cooking surface and the center of the outer surface is the central axis of the bottom, the heating element layer further comprises a second layer adjacent to the first layer via the insulating layer in a direction along the central axis, and the second layer is planar or spiral in shape.

12. The cooking utensil according to claim 11, wherein the second layer is planar in shape and is located closer to the bottom than the first layer.

13. The cooking utensil according to claim 11, wherein the second layer is planar in shape and is located further from the bottom than the first layer.

14. The cooking utensil according to claim 11, wherein the second layer is spiral-shaped.

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