Heating element, heating system and manufacturing method

Abstract

The invention discloses a heating element with a self-balancing effect for an appliance. The heating element comprises a substrate; a plurality of resistive heating traces, each trace comprising a first electrical contact and a second electrical contact, each electrical contact for connection to a power source; wherein: each trace comprises: an input portion connected to a first electrical contact; an output portion connected to the second electrical contact; and a partition defining portion connected at a first end to the input portion and at a second end to the output portion, the partition defining portion of the trace defining a respective partition and including at least three laterally adjacent trace portions of the trace. A heating system including the heating element and a method of manufacturing the heating element are also provided.

Description

Technical Field

[0001] The invention relates to a heating element for use in an appliance, a heating system comprising the heating element and a method of manufacturing the heating element. Background Art

[0002] The survival of ceramic heating elements with embedded Joule heating traces strongly depends on the uniformity of the peak temperature and the spatial temperature across the ceramic. Undesirably high deviations from nominal operation have been observed for co-fired ceramic heaters even with state-of-the-art manufacturing processes and equipment.

[0003] Figure 1 shows a trace arrangement of a prior art heating element 1. The heating element 1 is arc-shaped and thus can define radial and circumferential directions. For completeness, the circumferential direction is the direction along the curve of the arc, while the radial direction is perpendicular thereto, extending from the inner edge to the outer edge of the arc (or vice versa).

[0004] The heating element 1 comprises three tracks T1, T2, T3 arranged in a serpentine manner and mounted on, for example, a ceramic substrate (not shown). The tracks define three marked zones. Each zone comprises at least two circumferentially extending portions from each of the three tracks T1, T2, T3, and shorter radial portions of the tracks connecting the circumferentially extending portions.

[0005] In the heating element 1, most of the circumferential extension is radially adjacent to the circumferential extension from a different one of the three tracks T1, T2, T3. Thus, for example, an increase in heating in track T1 leads to an increase in heating in tracks T2 and T3. It has been observed that this leads to runaway thermal effects, particularly at downstream locations of the track ends. Figure 3A and 3B This is illustrated by showing high temperatures marked "H" downstream of the input and output of the trace, which are at the bottom right of the figure. This downstream heating can cause degradation of the heat sink and eventually cause the ceramic substrate to crack and fail.

[0006] The present invention has been designed to avoid such uncontrolled downstream heating of the traces and, therefore, of the ceramic substrate. Summary of the invention

[0007] In summary, the present invention solves this problem by providing a heating element having a zoned layout, wherein the traces are arranged into zones, each zone substantially comprising only a portion of the trace. More specifically, a first aspect of the present invention provides a heating element for an appliance, the heating element comprising: a substrate; a plurality of resistive heating traces, each trace comprising a first electrical contact and a second electrical contact, each electrical contact being for connecting to a power source; wherein: each trace comprises: an input portion connected to the first electrical contact; an output portion connected to the second electrical contact; and a zone defining portion connected to the input portion at a first end and to the output portion at a second end, the zone defining portion of the trace defining a respective zone and comprising at least three laterally adjacent trace portions of the trace.

[0008] In effect, this produces a set of partitions, each containing rolled-up "bundles" of trace portions all from the same trace, rather than regions where trace portions are highly interwoven with trace portions from other traces, which has been observed to produce runaway thermal effects.

[0009] In the context of the present application, "substrate" should be understood as a component on which or in which another component is located. Preferably, a plurality of resistive heating traces are located on or in the substrate. Here, in the substrate may mean that the traces are embedded in the substrate. Due to the high temperature resistance and electrical insulation properties of ceramic materials, the substrate may include or be formed of a ceramic material. Examples of ceramic materials that can be used in the implementation of the present invention include aluminum oxide and aluminum nitride. Other suitable ceramic materials, such as silicon nitride, silicon oxide, zinc oxide, barium nitride, may also be used.

[0010] In the context of the present application, the term "resistance heating trace" is used to refer to a conductive element, which may be in the form of a wire or a thin conductive trace on a surface, for example, which is configured to heat in response to an applied current. The trace is preferably elongated and narrower in width than in length. In this case, the longitudinal direction of the trace is the length direction along the path of the trace, and the transverse direction is perpendicular to the longitudinal direction. More simply, the longitudinal direction is the direction along the trace, and the transverse direction is the direction across the trace. Preferably, the resistance heating trace is formed by an ohmic conductor, such as a metal. Examples of suitable metals include tungsten, tantalum, molybdenum, or any combination thereof. The term "trace portion" refers to a longitudinal portion of the trace, i.e., a segment along the length of the trace (as opposed to, for example, a segment along the width of the trace). Here, "transversely adjacent trace portions" are trace portions that are adjacent to each other in the transverse direction, i.e., trace portions that are placed side by side. "Transversely adjacent" trace portions are also preferably spaced laterally apart. Multiple resistance heating traces may not overlap. In this way, it is meant that no resistance trace crosses or contacts another resistance trace. Furthermore, preferably, the resistor traces themselves do not cross, as this may create alternative current paths, which may result in non-uniform heating of the traces, and therefore of the substrate. In some cases, either only the zoned defined portions of the traces may not overlap, or at least the zoned defined portions of the traces may not overlap. However, in preferred cases, the entire resistor trace is non-overlapping.

[0011] The first aspect of the invention requires that the partition defining portion of the trace defines the corresponding partition. Here, this should be understood to mean that at least a portion of the partition defining portion of the trace defines the corresponding partition. It is not necessarily the entire trace that defines the corresponding partition. "Partition defining portion" can refer to an entire sub-segment of a trace that includes at least three laterally adjacent trace portions. Alternatively, the entire partition defining portion can include at least three laterally adjacent trace portions of the trace.

[0012] By increasing the degree to which portions of a given trace are laterally adjacent to portions of the same trace (e.g., relative to the arrangement shown in FIG. 1 , where no partition includes three laterally adjacent trace portions, as required by the first aspect of the invention), the resistive traces in these partitions respond to higher temperatures by having higher resistances, which in turn results in lower power dissipation. This creates a self-balancing effect, balancing sources of variation from part to part by varying power dissipation in each resistive heating trace.

[0013] It is provided that each trace comprises a first electrical contact and a second electrical contact, each electrical contact being used to connect to a power source. The first and / or second electrical contacts may comprise, for example, contact pads or bonding pads which may be connected to a power source such as a battery of the appliance, or configured to receive power from a mains power source. The input and output portions of the resistive trace are connected to the first and second electrical contacts, respectively. In this context, the terms "input" and "output" are used as labels and do not necessarily reflect the direction of current flow or the direction in which electrons pass through the resistive trace. In practice, the input and output portions of the trace are respectively routes to and from a partitioned defined portion of the resistive trace.

[0014] The geometry of the traces is now discussed in more detail. In a preferred case, the plurality of resistive traces are serpentine traces. In the context of the present invention, "serpentine" may be understood to mean that each trace includes at least one S-shaped or Σ-shaped portion. For example, when traveling longitudinally along the trace, there may be a clockwise turn followed by a counterclockwise turn, or vice versa. In the serpentine region, the corresponding longitudinal directions of two laterally adjacent trace portions may be opposite (in a reference frame outside the heating element, not in a reference frame inside the trace). In other words, when passing through the serpentine region, the direction of travel along the first trace portion is opposite to the direction of travel along the laterally adjacent second trace portion. It should be noted that travel will still be in the same longitudinal direction, which is used to represent the direction along the trace. In a reference frame outside this reference frame, the longitudinal direction may therefore change.

[0015] In some cases, laterally adjacent trace portions within a partition defining area are parallel to each other. Here, the term "parallel" is used to mean "parallel or substantially parallel." In the context of the present application, "substantially parallel" may mean that the straight portions of the two traces do not differ by more than, for example, 5°, 10°, or 20°, or within manufacturing tolerances.

[0016] We now discuss the geometric properties of the partition-defined areas of the heating element. The following disclosure can be applied to one, some or preferably all of the resistive traces of the heating element. The partition-defined portion of each trace of a plurality of resistive heating traces may include a border area and a central area. The central area may be surrounded by a border area. The trace portion of the central area may be only laterally adjacent to the border area, the input portion or the output portion of the trace (as described above). In other words, the trace portion of the central area is not laterally adjacent to any trace portion from a different resistive trace. In this article, "surrounded" may be understood to mean that at least 25%, 33%, 50%, 67% or 75% of the periphery of the central area is laterally adjacent to the border area. In each trace, only the input portion, the output portion and the border area of ​​the partition-defined area may be laterally adjacent to different traces of the plurality of resistive heating traces. This does not necessarily mean that all three of the border areas of the input portion, the output portion and the partition-defined portion must be laterally adjacent to different traces in the plurality of resistive traces, as opposed to, for example, the central area of ​​the partition-defined portion, where only one of these portions may be laterally adjacent to different traces. It should be understood that the central region of the zone-defined portion of each trace is isolated from other traces, which avoids uncontrolled heating in the zone. In addition, because at least in the central region of each zone, the resistive trace is only laterally adjacent to other portions of the same trace, the self-balancing effect is enhanced.

[0017] Obviously, the greater the extent to which a given trace is wrapped around a partition, the greater the extent to which portions of that trace are isolated from other traces, and the greater the self-balancing effect. Therefore, it is advantageous that the partition-defined portions represent a substantial length of each trace. More specifically, in each trace, the partition-defined portions may constitute at least a first predetermined proportion of the length of the trace. The first predetermined proportion may be 25%, 30%, 33%, 35%, 40%, 45%, 50%, 55%, 60%, 67%, 70%, 75%, 80%, 85%, 90% or 95%. Here, when we refer to the length of a trace, we refer to the total longitudinal length, the longitudinal direction having been defined in the present application. Similarly, the central area may constitute at least a second predetermined proportion of the length of the partition-defined portions. The second predetermined ratio may be 25%, 30%, 33%, 35%, 40%, 45%, 50%, 55%, 60%, 67%, 70%, 75%, 80%, 85%, 90% or 95%.

[0018] The plurality of traces may include a first trace and a second trace. The partition defining portion of the first trace may define a first partition, and the partition defining portion of the second trace may define a second partition. The plurality of traces may also include a third trace, and the partition defining portion of the third trace defines a third partition. The heating element may be arc-shaped, so some or all of the plurality of partitions may also be arc-shaped. The heating element may have a circumferential range of not less than 30°, 35°, 40°, 45°, 50° or 55°, and not more than 90°, 85°, 80°, 75°, 70° or 65°. The circumferential range of the heating element is preferably about 60°.

[0019] The boundary (i.e. edge) between the first partition and the second partition may be radial, or alternatively, circumferential. The boundary between the first partition and the second partition may include radial and circumferential portions. The third partition may be arcuate. The boundary between the first partition and the third partition may be radial, and the boundary between the second partition and the third partition may be radial. It has been found that an arrangement in which the boundary between the first partition and the second partition is circumferential, the boundary between the first partition and the third partition is radial, and the boundary between the second partition and the third partition is radial shows particularly effective self-balancing.

[0020] The heating element may also include machine readable indicia defining a respective duty cycle applied by the power source to each of the plurality of traces.The purpose of this feature will be outlined later in this application.

[0021] A first aspect of the present invention relates to a heating element and an appliance. The heating element may form part of a heating system, which is a second aspect of the present invention. More specifically, a second aspect of the present invention provides a heating system for an appliance, the heating system comprising: a heating element of the first aspect of the present invention; and a power supply configured to apply a current to a first contact of each of a plurality of resistive heating traces. The heating system may further include a controller configured to control the respective duty cycle of each first contact of the plurality of resistive heating traces applied to the heating element. Such a variation in the duty cycle is also helpful when avoiding uncontrolled heating of certain parts of the heating element. For example, each trace may have a desired or predetermined (see below) target power consumption in order to minimize undesirable heating, i.e., to minimize the peak substrate temperature. Using a constant duty cycle for each trace, it has been observed that the power consumption may deviate from the predetermined target value. This is believed to be an effect of manufacturing tolerances, resulting in the manufactured parts deviating from the nominal design. Therefore, it is useful to vary the duty cycle between different traces. Of course, given the inherent variability of deviations from the nominal characteristics, heating elements installed in different heating systems may require different duty cycles from each other. In view of this, the heating system may further include a scanner configured to scan the machine-readable mark to generate duty cycle data and transmit the duty cycle data to the controller. The controller may then be configured to control the corresponding duty cycle applied to each first contact of the plurality of resistive heating traces based on the received duty cycle data.

[0022] "Machine-readable indicia" as referred to in this application may refer to a visible indicia (e.g., an alphanumeric code, a barcode, or a QR code) printed or otherwise applied to a substrate surface, such as a heating element. Alternatively, the indicia may be stored in a memory of an RFID chip and may be obtained using an appropriate reader (covered herein by the term "scanner"). The term should be interpreted broadly to cover any information that may be stored on or in a heating element and that may be read by a suitable, preferably electronic, instrument (i.e., a scanner).

[0023] A third aspect of the invention provides a method of manufacturing a specific embodiment of a heating element of the first aspect of the invention, the method comprising the following steps: providing a substrate; applying a plurality of resistive heating traces to the surface of the substrate; measuring the operating power consumption of each of the plurality of resistive heating traces (e.g., using an electric power meter); and calculating a corresponding duty cycle to be applied to each of the plurality of resistive heating traces based on the measured operating power consumption; encoding the calculated duty cycle in a machine-readable mark, and applying the machine-readable mark to the heating element. In an optional additional step, the method may further include, after applying the plurality of resistive traces to the surface of the substrate, applying additional substrate material on the resistive heating traces so that the resistive heating traces are embedded in the substrate material. Measuring the operating power consumption and selecting an appropriate duty cycle means that power imbalances can be further addressed by obtaining actual power measurements. It is able to take into account power imbalances due to room temperature resistance, as well as imbalances due to changes in device temperature. In some cases, resistance may also be measured. Additional features of the manufacturing process may be as described in US7799267B, the entire contents of which are incorporated herein by reference. The present invention includes combinations of the described aspects and preferred features unless such combinations are expressly impermissible or explicitly avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

[0025] Fig. 1 shows a prior art heating element.

[0026] Figures 2A to 2G An example of a heating element according to the invention is shown.

[0027] Figure 3A and 3B A thermal map obtained using the prior art heating element shown in FIG. 1 is shown.

[0028] Figures 4A to 4H Shows the use of Figures 2A to 2G Thermal images obtained with the heating element of the present invention are shown. DETAILED DESCRIPTION

[0029] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying drawings. Other aspects and embodiments will be apparent to those skilled in the art. All documents mentioned herein are incorporated herein by reference.

[0030] Fig. 1 shows a heating element 1 of the prior art and has already been described in the background section of this patent application.

[0031] Figures 2A to 2G An embodiment of a heating element according to the first aspect of the invention is shown in each case and is described in detail below. Figures 2A to 2G The multiple traces shown in were developed iteratively. Therefore, for the sake of brevity, we will describe them in detail. Figure 2A , then explain Figure 2B Relative to Figure 2A , and so on.

[0032] Figure 2A A heating element 200 is shown that includes three resistive heating traces 202, 204, 206. The heating element 200 is generally arc-shaped, and each resistive heating trace 202, 204, 206 is also generally arc-shaped, arranged in a "rainbow-like" configuration. The traces 202, 204, 206 are generally serpentine and arranged as a plurality of parallel lines extending back and forth in a circumferential direction.

[0033] The heating element 200 includes a power input region 208 where the traces 202, 204, 206 are close to each other so that they can receive power input from a power source. The end of the heating element 200 close to the power input region 208 can be referred to as a proximal end 200p, while the opposite end can be referred to as a distal end 200d. Each heating trace 202, 204, 206 includes an input region 202a, 204a, 206a and an output region 202b, 204b, 206b. Between the input region 202a, 204a, 206a and the output region 202b, 204b, 206b of each trace 202, 204, 206 is a zone defining portion 202z, 204z, 206z. It will be noted that the zone defining portion of each trace 202, 204, 206 includes at least three laterally adjacent traces, as defined earlier in this patent application.

[0034] We now discuss the partition defining portion 204z in more detail, but it should be noted that the following description applies to all three partition defining portions 202, 204, 206. The partition defining portion 204z is arcuate, and includes six parallel trace portions that are laterally adjacent to each other. Figure 2A In an embodiment of the present invention, the spacing between the trace portions of the partition defining portion 204z is equal. Within the partition defining portion 204z, a central region 204c and a border region 204d can be identified. The central region 204c represents the area of ​​the partition defining portion 204z that is not laterally adjacent to the trace portions of the traces 202 or 206. The central region 204c is surrounded by the border region 204d, which represents the area of ​​the partition defining portion 204z that is laterally adjacent to the trace 206. Alternatively, the central region 204c is only laterally adjacent to other portions of the same trace 204. In this way, the self-balancing effect is more pronounced in this region 204c.

[0035] Figure 2B A heating element 300 is shown, very similar to Figure 2A Reference numerals having the same last two digits denote Figure 2A The same features in Figure 2B Reference numeral 302 in the figure denotes Figure 2A 202 in the figure, and so on), unless otherwise noted. Figure 2B The heating element 300 is Figure 2A The heating element 200 differs in the geometry of the zone defining portions 304z and 306z. Figure 2A In the heating element 200, each partition defining portion 202z, 204z, 206z is a pure arc. Figure 2B The zone defining portion 302z of the heating element 300 is a pure arc, but the zone defining portions 304z and 306z are not. Specifically, the portion 310 located on the right hand side of the zone defining portion 306z extends radially outward and extends to Figure 2A In the area occupied by the partition defining portion 204z. Therefore, Figure 2B The zone defining portion 306z of the heating element 300 is substantially arcuate, but has a greater width (in the radial direction) at one end, and the zone defining portion 304z is also substantially arcuate, but has a smaller width (in the radial direction) in the portion 312 at the same end. Figure 2BIn the specific example shown, the circumferential extent of the wider portion 310 of the partition defining portion 306z is approximately 10% to 20% of the entire circumferential extent of the heating element 300. However, this should not be considered as limiting: the circumferential extent of the wider portion 310 may not exceed 5%, 10%, 15%, 20%, 25%, 30%, 33%, 35%, 40%, 45% of the entire circumferential extent of the heating element. The circumferential extent may also be no less than 5%, 10%, 15%, 20%, 25%, 30%, 33%, 35%, 40%, 45% of the entire circumferential extent of the heating element. These options can be used to construct compatible appropriate percentage ranges, such as 5% to 50%, 10% to 25%, and so on. The same applies to the corresponding circumferential extent of the narrow portion 312 of the partition defining portion 304z. It should also be noted that it can be any one of the three partition defining portions 302z, 304z, 306z including a wider portion 310, and a corresponding second partition defining portion in the partition defining portions 302z, 304z, 306z including a narrower portion 312. The partition defining portion can include more than one wider portion 310 or more than one narrower portion 312. The wider or narrower portion 310, 312 is preferably located at one or both ends of the partition defining portion 302z, 304z, 306z. Due to the presence of the wider / narrower portion 310 / 312, the boundary between the partition defining portion 304z and the partition defining portion 306z is mainly circumferential, but includes a radial step 314 between the two circumferential portions 316, 318.

[0036] Figures 2C to 2E Heating elements 400, 500, 600 are shown, which are generally similar to Figure 2B Heating element 300. Figure 2C The heating element 400 with Figure 2B The difference between the heating element 300 of FIG. 4 is that the area of ​​the zone defining portion 404z extends radially upward toward the outer edge of the heating element 400 (except for the input portion 402a of the trace 402 and the input portion 404a of the trace 404). Therefore, the upper boundary between the zone defining portion 402z and the zone defining portion 404z is mainly circumferential, but includes a radial step 420 between the two circumferential portions 422, 424. It should also be noted that Figure 2CAll portions of the zone defining portion 404z of the heating element 400 include at least three laterally adjacent trace portions. The zone defining portion 404z includes two main arcuate regions 426 and 428. The arcuate region 426 is substantially elongated and extends along most of the circumferential extent of the heating element 400. The arcuate region 428 is wider than the arcuate region 426 in the radial direction and shorter than the arcuate region 426 in the circumferential direction. It is located at the proximal end 400p of the heating element 400. In the heating element 400, all the resistive traces 402, 404, 406 have a constant width.

[0037] Figure 2D The heating element 500 and Figure 2E The trace layout of the heating element 600 is Figure 2C The layout of the heating element 400 is the same. However, in Figure 2D The heating element 500 and Figure 2E In the heating element 600, the widths of the traces 502, 504, 506, 602, 604, 606 are variable:

[0038] Figure 2D : Here, trace 502 includes a first thicker region 530 located at an outer distal region of partition defining portion 502z. More specifically, trace 502 gradually increases from a first width to a second width when moving longitudinally from input portion 502a to partition defining portion 502z. Then, as trace 502 wraps around the entire partition defining portion 502z, the width of trace 502 gradually decreases from the second width to a third width (which may be the same as the first width). Then, in output portion 502b, the width of trace 502 increases from the third width to a fourth width (which is greater than the first, second, and third widths). The change in trace width in trace 504 is less obvious, but the trace in arc region 528 is slightly wider than in arc region 526. Input portion 506a of trace 506 has a first width and decreases to a second width in partition defining portion 506z. In partition defining portion 506z, the trace width is slightly narrower on the proximal side than on the distal side.

[0039] Figure 2E : Figure 2E The trace width of the heating element 600 is Figure 2D The heating element 500 is slightly different.

[0040] exist Figure 2F In the example, the layout of the heating element 700 is similar to that of Figure 2DThe differences of the heating element 500 are as follows. In the heating element 700, the trace 702 (specifically, its partition defining portion 702z) extends further radially inward, and the trace 706 (specifically, its partition defining portion 706z) extends further radially outward to abut the partition defining portion 702z of the trace 702. There is no longer a portion of the partition defining portion 704z between the partition defining portions 702z and 706z. In other words, the partition defining portions 702z and 706z are both arc-shaped and share a circumferential boundary 732. The partition defining portion 704z extends through the entire radial extent of the heating element 700 (except for the input portion 702a, the output portion 702b, the input portion 706a and the output portion 706b) at the proximal end 700p of the heating element 700. The partition defining portion 704z includes an arc-shaped region 734, which has a larger circumferential extent than the arc-shaped region 736. The trace width profile of the trace 702 is similar to Figure 2E The same as the trace 602 in FIG. 704. The input portion 704a of the trace 704 is wider than the partition defining portion 704z. In the arc region 734, the trace width is slightly larger at the far end.

[0041] exist Figure 2G The variation of trace width is minimized. Figures 2A to 2F The spacing between the traces in Figure 2G In FIG. 8 , the trace spacing between different traces 802 , 804 , and 806 is different. Figure 2G In the heating element 800 of FIG. 8A , a zone defining portion 804z of the trace 804 extends through the entire radial extent of the heating element 800 (except for the input portion 802a, the output portion 802b, the input portion 806a, and the output portion 806b). The trace portions in the zone defining portion 804z are spaced apart from laterally adjacent trace portions by a first spacing distance. The circumferential extent of the zone defining portion 804z is narrowest at the outermost and innermost regions (i.e., the regions with the greatest and smallest radial distances from the inner edge of the arc) and gradually increases to a point of maximum circumferential extent that spans approximately halfway across the heating element 800 in the radial direction. The zone defining portions 802z and 806z occupy the same radial extent as the zone defining portions 802a and 806z. Figure 2F However, in Figure 2G In the heating element 800, the outermost trace portion of the partition defining portion 802z does not extend all the way to the distal end 800b of the heating element. In addition, the spacing between laterally adjacent trace portions is greater than Figure 2F The boundary 838 between the partition defining portion 802z and the partition defining portion 804z is no longer radial, but is tilted. The partition defining portion 806z is substantially the same as the partition defining portion 706z in FIG. 7, except that the spacing between its laterally adjacent trace portions is smaller.

[0042] We now present some experimental results. These results were obtained using a computational fluid dynamics model, specifically the conjugate transfer model, which models the solid ceramic in detail based on its material properties, including the variation of electrical resistance with temperature. The model also simulates the geometry of the airflow around the heating element and takes into account voltage boundary conditions.

[0043] Figure 3A and 3B The heat distribution of the prior art heating element shown in FIG1 under two extreme conditions is shown. Figure 3A and Figure 3B In the examples, there is uneven heating throughout the heating element, with large peak temperatures of 437°C or 410°C at the far end of the heating element (ie, away from the power input point).

[0044] Figure 4A It is shown that in the first limiting case (i.e., corresponding to Figure 3A ) obtained from Figure 2A The heating element 200 shown is obtained. It can be seen that the runaway thermal effect at the far end of the heating element 200 is reduced and the peak temperature is reduced from 437°C to 401°C, thereby demonstrating the effectiveness of self-balancing. The overall heating of the heating element 200 is more balanced.

[0045] Figure 4B It is shown that the same from the first limiting case (i.e. corresponding to Figure 3A ) heat map, which is as follows Figure 2B Again, it can be seen that the temperature distribution is more uniform, with less pronounced heating at the far end of the heating element 300. The peak temperature is reduced from 437°C to 435°C. This reduction is less pronounced, but given the improved spatial temperature distribution and lower peak temperature, it still represents an improvement relative to Figure 3A A clear improvement over the prior art is shown.

[0046] Figure 4C Again, the result from the first limiting case (corresponding to Figure 3A ), which is obtained from Figure 2C The heating element 400 shown is obtained. Again, it can be seen that the temperature distribution is more uniform, with less significant heating at the far end of the heating element 400. The peak temperature is reduced from 437°C to 414°C.

[0047] Figure 4D Shows that from Figure 2D A pair of thermal images obtained by the heating element 500 shown correspond to Figure 3A and 3BIt can be seen that in both cases, the temperature distribution on the heating element 400 is more uniform, and the peak temperature is reduced from 437°C to 436°C and from 410°C to 406°C.

[0048] Figure 4E Four heatmaps are shown, the upper two corresponding to Figure 3A In the limiting case, the following two correspond to Figure 3B These heatmaps are generated using Figure 2E 600. For the first extreme case, it can be seen that the temperature distribution is more uniform, with the peak temperature decreasing from 437°C to 404°C (in both cases). The same effect is observed in the bottom two cases, with the peak temperature decreasing from 410°C to 388°C and from 410°C to 380°C.

[0049] Figure 4F Shows that from Figure 2F A pair of thermal images obtained by the heating element 700 shown correspond to Figure 3A and 3B It can be seen that in both cases, the temperature distribution on the heating element 400 is more uniform, and the peak temperature is reduced from 437°C to 414°C and from 410°C to 384°C. Figure 4G It is shown that in the first limiting case (corresponding to Figure 3A ) When power balancing is also applied from Figure 2F Additional thermal images were obtained for the heating element 700 of FIG. 10 as described elsewhere in this application. In this case, the temperature profile is further improved, with the peak temperature further reduced from 414° C. to 396° C.

[0050] Figure 4H Shows that from Figure 2G A pair of thermal images obtained by the heating element 800 shown correspond to Figure 3A and 3B It can be seen that in both cases, the temperature distribution on the heating element 400 is more uniform, and the peak temperature is reduced from 437°C to 417°C and from 410°C to 392°C.

[0051] It can therefore be understood that in all examples of heating elements 200, 300, 400, 500, 600, 700, 800 falling within the scope of the present invention, more uniform temperature distribution and reduced peak temperature are observed. In other words, significant technical effects are achieved throughout the scope of the present invention.

[0052] The features disclosed in the preceding description, or in the following claims, or in the accompanying drawings, expressed in their specific form or as means for performing the disclosed functions, or as methods or processes for obtaining the disclosed results, may, where appropriate, be used alone or in any combination of these features to implement the invention in its different forms.

[0053] Although the present invention has been described in conjunction with the above exemplary embodiments, many equivalent modifications and variations will be apparent to those skilled in the art when this disclosure is given. Therefore, the above exemplary embodiments of the present invention are considered to be illustrative rather than restrictive. Various changes may be made to the described embodiments without departing from the spirit and scope of the present invention.

[0054] For the avoidance of any doubt, any theoretical explanations provided herein are intended to enhance the reader's understanding. The inventors do not wish to be bound by any of these theoretical explanations.

[0055] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0056] Throughout the specification, including the following claims, unless the context requires otherwise, the words "comprise" and "comprising", and variations such as "comprises", "including" and "comprising", will be understood to imply the inclusion of stated integers or steps or integers or groups of steps but not the exclusion of any other integers or steps or integers or groups of steps.

[0057] It must be noted that, as used in the specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" one particular value, and / or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when a value is expressed as an approximation by using the antecedent "about," it will be understood that the particular value forms another embodiment. The term "about" in relation to a numerical value is optional and means, for example, + / - 10%.

Claims

1. A heating element for an appliance, the heating element comprising: substrate; a plurality of resistive heating traces, each trace comprising a first electrical contact and a second electrical contact, each electrical contact for connection to a power source; in: Each trace consists of: an input portion connected to the first electrical contact; an output section connected to the second electrical contact; and A zone defining portion is connected to the input portion at a first end and to the output portion at a second end, the zone defining portion of the trace defining a corresponding zone and comprising at least three laterally adjacent trace portions of the trace.

2. The heating element according to claim 1, wherein: The partition-defining portions of each trace are arranged in a serpentine manner; and The plurality of resistive heating traces do not overlap.

3. The heating element according to claim 1 or 2, wherein: The substrate is a ceramic substrate; and the plurality of traces are metallic.

4. The heating element according to any one of claims 1 to 3, wherein: Laterally adjacent trace portions within the zone defining portion are parallel to each other.

5. The heating element according to any one of claims 1 to 4, wherein: The zone-defined portion of each trace of the plurality of resistive heating traces comprises: Boundary areas; and A central region is surrounded by the border region, and the trace portion of the central region is only laterally adjacent to the border region, the input portion or the output portion of the trace.

6. The heating element according to claim 5, wherein: In each trace, only boundary regions of the input portion, the output portion, and the zone defining portion are laterally adjacent to a different trace of the plurality of resistive heating traces.

7. The heating element according to any one of claims 1 to 6, wherein: The partition defining portion occupies at least 50% of the length of each trace.

8. The heating element according to any one of claims 1 to 7, further comprising: A machine-readable indicia defines a respective duty cycle applied by a power source to each of the plurality of traces.

9. The heating element according to any one of claims 1 to 8, wherein: The plurality of traces include a first trace, a second trace, and a third trace, the zone defining portion of the first trace defining a first zone, the zone defining portion of the second trace defining a second zone, and the zone defining portion of the third trace defining a third zone.

10. The heating element of claim 9, wherein: The heating element or the substrate is arc-shaped; and Each partition of the plurality of partitions is arc-shaped.

11. The heating element of claim 10, wherein: a boundary between the first subarea and the second subarea is circumferential; A boundary between the first partition and the third partition is radial; and The boundary between the second partition and the third partition is radial.

12. A heating system for an appliance, the heating system comprising: A heating element according to any one of claims 1 to 11; A power source is configured to apply a current to a first contact of each of the plurality of resistive heating traces.

13. The heating system according to claim 12, further comprising: A controller is configured to control a respective duty cycle applied to each first contact of the plurality of resistive heating traces.

14. A heating system according to claim 13 as appended to claim 8, further comprising: a scanner configured to scan the machine-readable indicia to generate duty cycle data and transmit the duty cycle data to the controller, Wherein the controller is configured to control a respective duty cycle applied to each first contact of the plurality of resistive heating traces based on the received duty cycle data.

15. A method of manufacturing a heating element according to any one of claims 1 to 11, the method comprising: providing the substrate; applying the plurality of resistive heating traces to a surface of the substrate; measuring an operating power consumption of each of the plurality of resistive heating traces; and calculating a respective duty cycle to be applied to each of the plurality of resistive heating traces; The calculated duty cycle is encoded in a machine-readable indicia and the machine-readable indicia is applied to the heating element.

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