An electromagnetic oven coil capable of improving uniformity and thermal efficiency simultaneously

Abstract

The application discloses an electromagnetic oven line disc capable of simultaneously improving uniformity and thermal efficiency, and belongs to the technical field of electromagnetic ovens. The electromagnetic oven line disc comprises a line disc support, a magnetic strip and a magnetic ring. The magnetic permeability of the magnetic ring is lower than that of the magnetic strip. The strong magnetic field of the inner ring is dispersed by the weak magnetic ring, and the weak magnetic field of the outer ring is effectively strengthened by the strong magnetic strip. The application realizes the double breakthrough of improving thermal efficiency and improving heating uniformity by optimizing the material collocation. According to the test of a third-party testing institution according to GB 21456, the thermal efficiency of heating 2 kg of water from 15 DEG C to 75 DEG C under the power of 2500 W reaches 91%, which exceeds the national first-class energy efficiency standard, and an unexpected technical effect is achieved.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic heating technology, and specifically relates to an induction cooker coil. Background Technology

[0002] An induction cooker generates a high-frequency alternating magnetic field through a coil, causing eddy currents in the bottom of the pot and thus heating it. Magnetic strips are arranged at the bottom of the coil to shield the magnetic field and prevent it from leaking downwards. A magnetic ring is located at the center of the coil to concentrate the magnetic field, directing the magnetic lines of force upwards into the bottom of the pot.

[0003] In the field of induction cooker coils, those skilled in the art have long faced a dilemma: improving thermal efficiency and enhancing heating uniformity are two technical goals that cannot be achieved simultaneously; only one can be chosen. This is because the industry typically employs two approaches. The first approach is the uniform approach: the magnetic strip and magnetic ring use the same material (e.g., both are manganese-zinc ferrite), and the coil is wound evenly (the inner and outer coils have the same turn density). This approach achieves a relatively uniform heating effect through homogeneous material combinations and even winding, but the thermal efficiency typically only reaches 85% to 88%, making it difficult to exceed 90%.

[0004] The second approach is the center reinforcement approach: the magnetic ring uses a material with higher magnetic permeability than the magnetic strip, which enhances the central magnetic focusing ability to improve heating speed and thermal efficiency. Although this approach can improve thermal efficiency to some extent, the excessive concentration of the magnetic field in the central region leads to a severe deterioration in heating uniformity—the central temperature soars while the edge temperature remains low.

[0005] Therefore, those skilled in the art generally believe that improving thermal efficiency inevitably comes at the cost of sacrificing heating uniformity, and improving heating uniformity inevitably prevents thermal efficiency from exceeding 90%. These two technical goals are mutually exclusive and cannot be achieved simultaneously, which is a long-standing technical problem that has remained unsolved in this field.

[0006] Through long-term research and extensive experimentation, the inventors have overcome this technical bias and discovered the following key physical laws for the first time, based on which they proposed the technical solution of this invention: The high coil turn density in the inner ring double-layer winding region results in a large number of highly concentrated magnetic field lines. If a high-permeability magnetic ring (center reinforcement scheme) is used here, it will further concentrate the already highly concentrated magnetic field lines. Although the central heating speed is increased, it exacerbates the deterioration of heating uniformity, and the magnetic ring itself is prone to magnetic saturation. This invention takes the opposite approach, using a low-permeability weak magnetic ring in the central region of the inner ring to disperse the concentrated strong magnetic field—effectively concentrating the magnetic field while avoiding excessive concentration, allowing the magnetic field lines to disperse naturally. At the same time, the low-permeability magnetic ring has stronger anti-saturation capability, able to withstand the high magnetic flux density in the inner ring double-layer region without saturation.

[0007] The coil turns density in the outer ring single-layer winding region is low, resulting in a relatively small number and weak intensity of magnetic field lines. This invention uses a strong magnetic strip with high permeability in the outer ring region to effectively strengthen the weak magnetic field—efficiently absorbing the magnetic field lines dissipating from the bottom of the coil, reducing bottom magnetic leakage loss, and improving overall thermal efficiency.

[0008] More importantly, the magnetic strip and magnetic ring of this invention overlap in the vertical direction, and this overlapping structure, combined with the aforementioned materials, creates a synergistic effect. The overlapping structure eliminates air gaps in the magnetic circuit, allowing magnetic lines of force to transition directly from the magnetic strip to the magnetic ring without passing through a high-resistivity air gap, significantly reducing leakage magnetic losses. At the same time, the gap between the overlapping surfaces acts as a built-in "distributed air gap," preventing the risk of local magnetic saturation exacerbated by the overlap.

[0009] Through a systematic design that combines a strong inner magnetic field with a weak magnetic ring for dispersion, a weak outer magnetic field with a strong magnetic strip for effective reinforcement, and overlapping with gaps for synergistic enhancement, this invention achieves a dual breakthrough in both thermal efficiency and heating uniformity for the first time—achieving a high thermal efficiency of 91% while significantly improving heating uniformity. This effect is unforeseen by those skilled in the art based on existing technologies, completely breaking the technical prejudice that "improving thermal efficiency inevitably sacrifices heating uniformity."

[0010] Currently, the thermal efficiency of similar induction cooker coils on the market is typically between 85% and 88%. No existing technology has disclosed or implied that applying the above-mentioned systematic design scheme to induction cooker coils can achieve a thermal efficiency exceeding 90%. Therefore, the technical solution of this invention is not a conventional optimization that would be easily conceived by those skilled in the art, but rather an innovative solution that has been verified through extensive experiments and has produced unexpected technical effects. Summary of the Invention

[0011] The technical problem to be solved by the present invention is that the existing induction cooker coils cannot simultaneously improve thermal efficiency and heating uniformity, and the thermal efficiency is difficult to exceed 90%.

[0012] To solve the above-mentioned technical problems, the present invention provides an induction cooker coil, including a coil support, a magnetic strip, and a magnetic ring. The magnetic strip is fixed to the bottom of the coil support, and the magnetic ring is disposed at the center of the coil support. The magnetic ring is characterized in that the magnetic permeability of the magnetic ring is lower than that of the magnetic strip, so that the strong magnetic field concentrated in the inner ring double-layer region is dispersed by the weak magnetic ring, and the relatively weak magnetic field in the outer ring single-layer region is effectively strengthened by the strong magnetic strip, thereby improving heating uniformity while improving thermal efficiency.

[0013] The present invention also provides a method for improving the thermal efficiency of an induction cooker coil and improving heating uniformity. A weak magnetic ring with a magnetic permeability lower than that of a magnetic strip is selected and placed at the center of the coil support to disperse the strong magnetic field of the inner ring. A strong magnetic strip is fixed to the bottom of the coil support to strengthen the weak magnetic field of the outer ring, so that the magnetic field energy does not excessively concentrate in the central area and is effectively strengthened in the edge area.

[0014] The beneficial effects of this invention are as follows: Through the synergistic design of "inner ring strong magnetic field combined with weak magnetic ring dispersion, and outer ring weak magnetic field combined with strong magnetic strip effective reinforcement," the high permeability strong magnetic strip can efficiently absorb the magnetic lines of force scattered at the bottom of the coil, reduce bottom leakage magnetic loss, and improve overall thermal efficiency; the low permeability weak magnetic ring has stronger anti-saturation capability, is less prone to local magnetic saturation during high-power operation, stabilizes the inductance, and reduces the voltage stress and temperature rise of the IGBT; the weak magnetic ring disperses the inner ring strong magnetic field, so that the concentrated magnetic lines of force are naturally dispersed when gathered by the magnetic ring, avoiding excessive magnetic flux density in the central area. The high magnetic field guides more magnetic lines of force to the edge of the pot bottom, improving heating uniformity; the overlapping structure of the magnetic ring and magnetic strip eliminates air gaps in the magnetic circuit, further reducing magnetic leakage loss; this invention achieves a dual breakthrough in thermal efficiency and heating uniformity for the first time, breaking the long-standing technical prejudice in the field that "improving thermal efficiency inevitably sacrifices heating uniformity"; this invention goes against the grain, achieving a technical goal that those skilled in the art have long been unable to achieve simultaneously through a specific material combination of an inner ring weak magnetic ring and an outer ring strong magnetic strip, a reverse design concept that has never been disclosed or implied in the field.

[0015] It should be noted that the aforementioned 91% thermal efficiency is the combined effect of the technical features claimed in this invention and other optimized designs of the induction cooker coil (including winding method, overlapping and gapped magnetic circuit structure, forward and reverse winding wire, etc.), and is not solely contributed by a single technical feature of material combination. However, the technical features claimed in this invention, when applied alone without being combined with other optimized designs, can produce independent beneficial effects: through the material combination of "inner ring weak magnetic ring dispersing strong magnetic field and outer ring strong magnetic strip effectively strengthening weak magnetic field," while keeping other structures as traditional solutions (equal winding, separate magnetic circuit, traditional enameled wire), the thermal efficiency can be increased from 86.2% to 88.5%, an increase of approximately 2.3 percentage points, while simultaneously improving heating uniformity. This independent effect is unrelated to other technical features of this invention, fully demonstrating that the material combination scheme of this invention is inventive in itself and does not necessarily rely on other technical features to achieve its technical effect.

[0016] According to the national standard GB 21456, the induction cooker coil of this invention, when heated from 15°C to 75°C at 2500W, achieved a thermal efficiency of 91%, exceeding the national first-class energy efficiency standard. The thermal efficiency of similar products on the market is usually between 85% and 88%. This invention improves upon existing technologies by about 3 to 6 percentage points, achieving unexpected technical results. Attached Figure Description

[0017] Figure 1 This is a cross-sectional view of the magnetic circuit structure of the induction cooker coil according to Embodiment 1 of the present invention.

[0018] Figure 2 This is a schematic diagram of the magnetic field lines in Embodiment 1 of the present invention.

[0019] In the diagram: 1-coil support, 2-magnetic strip, 3-magnetic ring, 4-bottom of the pot, 5-magnetic lines. Detailed Implementation

[0020] Example 1 (Optimal Solution - Manganese-zinc ferrite magnetic strip + iron powder core magnetic ring, 2500W) Reference Figure 1 and Figure 2 This embodiment provides a coil for use in a 2500W induction cooker. The coil includes a coil support (1), magnetic strips (2) fixed to the bottom of the support, and a magnetic ring (3) located at the center of the support. The magnetic strips (2) are seven manganese-zinc ferrite magnetic strips, arranged radially and evenly at the bottom of the coil support (1), with high permeability, used to strengthen the weak magnetic field in the outer single-layer region. The magnetic ring (3) is an iron powder core magnetic ring with low permeability, used to disperse the strong magnetic field in the inner double-layer region. The particles inside the iron powder core magnetic ring have a natural insulating layer, forming a distributed micro-air gap, which has excellent anti-saturation ability.

[0021] The coil in this embodiment is made of coiled wire in both directions. The magnetic ring (3) and the magnetic strip (2) overlap in the vertical direction by 0.5 cm. A gap of 1 mm is left between the overlapping surfaces of the magnetic ring (3) and the magnetic strip (2).

[0022] Reference Figure 2 The direction of the magnetic field lines (5) embodies the core design principle of this invention: the strong magnetic field generated by the inner double-layer winding area is dispersed by the low permeability weak magnetic ring (3), and the magnetic field lines are naturally dispersed when passing through the magnetic ring, avoiding excessive magnetic flux density in the central area and guiding more magnetic field lines to the edge of the bottom of the pot (4); the weak magnetic field generated by the outer single-layer winding area is effectively strengthened by the high permeability strong magnetic strip (2), efficiently absorbing the dissipated magnetic field lines and reducing the leakage magnetic loss at the bottom. The overlapping structure of the magnetic strip and the magnetic ring eliminates the air gaps in the magnetic circuit, allowing the magnetic field lines to transition directly.

[0023] Testing showed that this embodiment, at 2500W power, achieved a thermal efficiency of 91% when heating 2kg of water from 15℃ to 75℃ according to GB 21456, exceeding the national Class 1 energy efficiency standard. After continuous operation for 30 minutes under the same conditions, the steady-state temperature of the IGBT heatsink was approximately 6℃ lower than that of traditional homogeneous material solutions. Simultaneously, heating uniformity was significantly improved. These test results have been officially verified by a qualified third-party testing institution (Report No.: CEL-A-20260703-069817).

[0024] Example 2 (2200W verification) With the same structure as Example 1, at a power of 2200W, the thermal efficiency reaches 90.2% according to GB 21456, which also exceeds the national first-class energy efficiency standard.

[0025] Example 3 (Magnetic ring is made of nickel-zinc ferrite) The difference from Example 1 is that the magnetic ring in this example uses nickel-zinc ferrite, whose permeability is also lower than that of manganese-zinc ferrite magnetic strips. Testing shows that the thermal efficiency and heating uniformity of this example are still superior to traditional homogeneous material solutions.

[0026] Comparative Example 1 (Traditional Uniform Scheme – Magnetic Strips and Magnetic Rings are Made of the Same Material and are Wound Evenly) In contrast, under the exact same test conditions (2500W power, same motherboard, same cookware, 2kg water), the induction cooker coil using the traditional uniform design (the magnetic strip and magnetic ring are both manganese-zinc ferrite, and the coil is wound evenly) has a thermal efficiency of only 86.2%. The heating uniformity is acceptable, but the thermal efficiency is difficult to exceed 90%.

[0027] Comparative Example 2 (Center-Reinforced Scheme – Magnetic Ring Permeability Higher Than Magnetic Strip) In contrast, under identical testing conditions, the induction cooker coil employing a center-strengthened design (with a manganese-zinc ferrite magnetic ring and an iron powder core for the magnetic strip, the magnetic permeability of the magnetic ring being higher than that of the magnetic strip) achieved a thermal efficiency of 87.5%. While slightly higher than the traditional uniform design, this was far lower than the 91% of Example 1, and the heating uniformity was severely deteriorated. This indicates that while the center-strengthened design can improve thermal efficiency to some extent, it comes at the cost of sacrificing heating uniformity, making it impossible to simultaneously achieve both technical objectives.

[0028] Comparative Example 3 (Independent Effect Verification – Only the material combination was changed, while other structures remained the traditional scheme) In contrast, under exactly the same test conditions (2500W power, same motherboard, same cookware, 2kg water), an induction cooker coil was made, only the material combination of the magnetic strip and magnetic ring was changed to the scheme of this invention (the magnetic strip is manganese zinc ferrite, the magnetic ring is iron powder core, and the magnetic permeability of the magnetic ring is lower than that of the magnetic strip), but other structures remained the traditional scheme (the coil uses traditional enameled wire, is wound evenly, and the magnetic strip and magnetic ring are separated without overlap or gap).

[0029] Test results show that the thermal efficiency of this comparative example is 88.5%, which is about 2.3 percentage points higher than the 86.2% of the traditional uniform scheme (the magnetic strips and magnetic rings are all manganese-zinc ferrite, and other structures are the same). At the same time, the heating uniformity is improved.

[0030] This result demonstrates that the material combination scheme claimed in this invention, when applied alone without being combined with other optimized designs (non-uniform winding, overlapping with gaps, and reverse winding), can produce independent beneficial effects—simultaneously improving thermal efficiency and heating uniformity. This independent effect is unrelated to other technical features of this invention, fully proving that the material combination scheme of this invention is inventive in itself and does not necessarily rely on other technical features to achieve its technical effects.

[0031] Proof of a Double Breakthrough The test results of Comparative Example 1 and Comparative Example 2 jointly demonstrate a long-standing technical bias in the field: traditional uniform solutions have limited thermal efficiency, while center-strengthened solutions suffer from deteriorated uniformity. However, the solution of this invention—an inner ring weak magnetic ring dispersing a strong magnetic field and an outer ring strong magnetic strip effectively strengthening the weak magnetic field—simultaneously overcomes both the thermal efficiency bottleneck and uniformity limitations, achieving a high thermal efficiency of 91% while significantly improving heating uniformity. This achieves a dual technical objective that those skilled in the art have long been unable to simultaneously achieve. This dual breakthrough effect is something that those skilled in the art could not have foreseen from the prior art, further demonstrating the inventiveness of this invention.

[0032] Proof of independent creativity The test results of Comparative Example 3 independently demonstrate the inventiveness of the material combination scheme of this invention: even without any other optimized design, applying the "magnetic ring permeability is lower than that of the magnetic strip" material combination scheme of this invention alone can increase the thermal efficiency from 86.2% to 88.5%, an increase of approximately 2.3 percentage points, based on traditional uniform winding, split magnetic circuit structure, and traditional enameled wire, while also improving heating uniformity. This independent effect does not depend on other technical features of this invention, fully demonstrating that the material combination scheme of this invention itself possesses significant inventiveness.

[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An induction cooker coil, comprising a coil support, a magnetic strip, and a magnetic ring, wherein the magnetic strip is fixed to the bottom of the coil support, and the magnetic ring is disposed at the center of the coil support, characterized in that: The magnetic permeability of the magnetic ring is lower than that of the magnetic strip, which disperses the strong magnetic field concentrated in the inner ring double-layer region by the weak magnetic ring and effectively strengthens the relatively weak magnetic field in the outer ring single-layer region by the strong magnetic strip, thereby improving heating uniformity while increasing thermal efficiency.

2. A method for improving the thermal efficiency of an induction cooker coil and enhancing heating uniformity, characterized in that: A weak magnetic ring with a lower permeability than the magnetic strip is selected and placed at the center of the coil support to disperse the strong magnetic field of the inner ring. The strong magnetic strip is fixed at the bottom of the coil support to strengthen the weak magnetic field of the outer ring, so that the magnetic field energy does not excessively concentrate in the central area and is effectively strengthened in the edge area.

3. The induction cooker coil according to claim 1, characterized in that: The magnetic strip is made of manganese-zinc ferrite, and the magnetic ring is made of iron powder core.

4. The induction cooker coil according to claim 3, characterized in that: The iron powder core magnetic ring has distributed micro-air gaps inside.

5. The induction cooker coil according to claim 1, characterized in that: The magnetic permeability of the magnetic ring is 30% to 80% of the magnetic permeability of the magnetic strip.

6. The induction cooker coil according to claim 1, characterized in that: The magnetic ring and the magnetic strip overlap in the vertical direction, and there is a gap between the overlapping surfaces.

7. The induction cooker coil according to claim 1, characterized in that: It also includes a coil, which is double-wound in the inner coil area and single-wound in the outer coil area, with the inner and outer coils having the same winding spacing.

8. The induction cooker coil according to claim 1, characterized in that: The induction cooker coil, within a power range of 2200W to 2500W, heats 2kg of water from 15℃ to 75℃. According to GB 21456 testing, the thermal efficiency reaches over 90%, with a thermal efficiency of 91% at 2500W power.

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