Cathode filament, cathode electron emitter, cathode assembly, magnetron, and electrical appliance

Abstract

A cathode filament (100), a cathode electron emitter (500), a cathode assembly (300), a magnetron (200), and a microwave cooking appliance are disclosed. The cathode filament (100) has a spiral structure, the wire material of the cathode filament (100) comprises a filament core (14) and a carburized layer (16), the carburized layer (16) covers the filament core (14) at least in the circumferential direction of the filament core (14), the material of the filament core (14) comprises a lanthanum-tungsten material, and the carburized layer (16) comprises a lanthanum-tungsten carburized layer.

Description

Cathode filament, cathode electron emitter, cathode assembly, magnetron and electrical components

[0001] Priority information

[0002] This application claims priority and benefits to patent applications filed with the China National Intellectual Property Administration on November 29, 2024, with patent application numbers 202411750363.7, and filed with the China National Intellectual Property Administration on June 12, 2025, with patent application numbers 202510788118.3 and 202510788138.0, the entire contents of which are incorporated herein by reference as if copied herein. Technical Field

[0003] This application relates to the field of household appliance technology, and in particular to a cathode filament, a cathode electron emitter, a cathode assembly, a magnetron, and a microwave cooking appliance. Background Technology

[0004] According to current market statistics, microwave ovens using magnetrons have a minimum output power of 500 watts or more. Lowering the power will result in unstable microwave output, and in severe cases, no microwave output at all. Summary of the Invention

[0005] This application provides a cathode filament, a cathode electron emitter, a cathode assembly, a magnetron, and a microwave cooking appliance to solve at least one of the aforementioned technical problems.

[0006] This application provides a cathode filament for a magnetron. The cathode filament has a spiral structure, and the filament material includes a filament core and a carbonized layer. The carbonized layer covers the filament core at least in the circumferential direction. The material of the filament core includes lanthanum-tungsten, and the carbonized layer includes a lanthanum-tungsten carbonized layer.

[0007] In the aforementioned cathode filament, the filament core material includes lanthanum tungsten material, and the carbide layer includes lanthanum tungsten carbide layer. This reduces the work function of the cathode filament to a certain extent and enhances the migration ability of rare earth elements in the cathode filament, thereby improving the electron emission capability of the cathode filament to a certain extent, enabling the magnetron to adapt to the higher power requirements of microwave cooking appliances.

[0008] In some embodiments, the thickness of the carbonized layer is 6% to 10% of the thickness of the filament.

[0009] In some embodiments, the thickness of the carbonized layer is 8% of the thickness of the filament.

[0010] In some embodiments, the thickness of the carbonized layer is 42 μm, and the thickness of the filament is 0.5 mm.

[0011] In some embodiments, the cathode filament material further includes at least one of yttrium, rhenium, lutetium, zirconium, and hafnium.

[0012] In some embodiments, the grain size of the filament core ranges from 0.4 μm to 2 μm.

[0013] In some embodiments, the cathode filament is capable of emitting electrons after being powered on and after being powered off.

[0014] In some embodiments, the length of the cathode filament is 12 ± 0.5 mm.

[0015] The present application provides a cathode assembly for a magnetron, the cathode assembly including the cathode filament of any of the above embodiments.

[0016] In some embodiments, the cathode assembly includes a support with two end caps, and the two ends of the cathode filament are respectively disposed within the two end caps.

[0017] The magnetron provided in this application includes the cathode assembly of any of the above embodiments.

[0018] The microwave cooking appliance provided in this application includes the magnetron described in the above embodiment.

[0019] In some embodiments, the cathode filament is capable of emitting electrons at a minimum output power of 100 watts in the microwave cooking appliance.

[0020] In the aforementioned cathode assembly, magnetron, and microwave cooking appliance, the filament core material includes lanthanum-tungsten material, and the carbide layer includes lanthanum-tungsten carbide layer. This reduces the work function of the cathode filament to a certain extent and enhances the migration ability of rare earth elements in the cathode filament, thereby improving the electron emission capability of the cathode filament to a certain extent and enabling the magnetron to adapt to the higher power requirements of the microwave cooking appliance.

[0021] The embodiments of this application provide a cathode electron emitter for a magnetron, wherein the cathode electron emitter is cylindrical.

[0022] The aforementioned cathode electron emitter is cylindrical, which can effectively improve the internal stress of the cathode electron emitter and reduce the failure rate of the cathode electron emitter to a certain extent.

[0023] In some embodiments, the inner diameter of the cathode electron emitter is 2.5 mm to 3.5 mm.

[0024] In some embodiments, the outer diameter of the cathode electron emitter is 3.6 mm to 4.5 mm.

[0025] In some embodiments, the height of the cathode electron emitter is 10 mm to 13 mm.

[0026] In some embodiments, the cathode electron emitter is made of a tungsten alloy.

[0027] In some embodiments, the cathode electron emitter includes a core and a carbide layer, the carbide layer covering the core at least in the circumferential direction, the core being made of lanthanum-tungsten material, and the carbide layer being a lanthanum-tungsten carbide layer.

[0028] In some embodiments, the thickness of the carbonized layer is 6% to 10% of the sum of the thickness of the carbonized layer and the core.

[0029] In some embodiments, the thickness of the carbonized layer is 8% of the sum of the thickness of the carbonized layer and the core.

[0030] In some embodiments, the thickness of the carbonized layer is 42 μm, and the sum of the thicknesses of the carbonized layer and the core is 0.5 mm.

[0031] In some embodiments, the cathode electron emitter is further made of at least one of yttrium, rhenium, lutetium, zirconium, and hafnium.

[0032] In some embodiments, the grain size of the core ranges from 0.4 μm to 2 μm.

[0033] In some embodiments, the cathode electron emitter is capable of emitting electrons after power is applied and then continuing to emit electrons after power is de-energized.

[0034] The present application provides a cathode assembly for a magnetron, the cathode assembly including the cathode electron emitter of any of the above embodiments.

[0035] In some embodiments, the cathode assembly includes a support with two end caps, and the two ends of the cathode electron emitter are respectively disposed within the two end caps.

[0036] The magnetron provided in this application includes the cathode assembly of any of the above embodiments.

[0037] The microwave cooking appliance provided in this application includes the magnetron described in the above embodiment.

[0038] In some embodiments, the cathode electron emitter includes a core and a carbonized layer, the carbonized layer covering the core at least in the circumferential direction, the core being made of lanthanum-tungsten material, and the carbonized layer being a lanthanum-tungsten carbonized layer, the cathode electron emitter being capable of emitting electrons at a minimum output power of 100 watts in the microwave cooking appliance.

[0039] In the aforementioned cathode assembly, magnetron, and microwave cooking appliance, the cathode electron emitter is cylindrical, which can effectively improve the internal stress of the cathode electron emitter and reduce the failure rate of the cathode electron emitter to a certain extent.

[0040] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0042] Figure 1 is a schematic diagram of the structure of the cathode filament according to an embodiment of this application;

[0043] Figure 2 is a cross-sectional schematic diagram of the cathode filament of the present application embodiment;

[0044] Figure 3 is a schematic diagram of the structure of the cathode assembly according to an embodiment of this application;

[0045] Figure 4 is a cross-sectional schematic diagram of the magnetron according to an embodiment of this application;

[0046] Figure 5 is a schematic diagram of the operation of the magnetron electrons in the embodiment of this application;

[0047] Figure 6 is a metallographic cross-sectional view of the cathode filament of the present application embodiment;

[0048] Figure 7 is a partial schematic diagram of the metallographic cross-section of the cathode filament of the present application embodiment;

[0049] Figure 7a is a schematic diagram of the grain size distribution of the filament core of the cathode filament according to an embodiment of this application;

[0050] Figure 7b is a schematic diagram of the grain morphology distribution of the filament core of the cathode filament according to an embodiment of this application;

[0051] Figure 8 is a comparison of the electron emission capabilities of the cathode filament in the embodiment of this application and the cathode filament in related technologies;

[0052] Figure 9 is a circuit diagram of a frequency converter based on related technologies;

[0053] Figure 10 is a schematic diagram showing the relationship between microwave output power and control current in related technologies;

[0054] Figure 11 is a schematic diagram of the metal band structure in the related technology;

[0055] Figure 12 is a schematic metallographic cross-section of the cathode filament of the related technology;

[0056] Figure 13 is a partial schematic diagram of the metallographic cross-section of the cathode filament of the related technology;

[0057] Figure 14 is a schematic diagram of the grain size distribution of the filament core of a cathode filament in a related technology;

[0058] Figure 15 is a schematic diagram of the grain morphology distribution of the filament core of a cathode filament in a related technology.

[0059] Explanation of the main component reference numerals in Figures 1 to 15: Cathode filament 100, magnetron 200, cathode assembly 300, anode assembly 400, wire 12, filament core 14, carbonized layer 16, bracket 18, connecting rod 20, cathode connector 24, end cap 26, anode cylinder 28, anode plate 30, interaction space 32, upper magnet 34, lower magnet 36, energy output window 38.

[0060] Figure 16 is a three-dimensional schematic diagram of the cathode electron emitter according to an embodiment of this application;

[0061] Figures 17 and 18 are schematic diagrams of the dimensions of the cathode electron emitter according to the embodiments of this application;

[0062] Figure 19 is a schematic diagram of the structure of the cathode assembly according to an embodiment of this application;

[0063] Figure 20 is a cross-sectional schematic diagram of the magnetron according to an embodiment of this application;

[0064] Figure 21 is a cross-sectional schematic diagram of the cathode electron emitter according to an embodiment of this application;

[0065] Figure 22 is a schematic diagram of the operation of the magnetron electronics in the embodiment of this application;

[0066] Figure 23 is a schematic diagram of the grain size distribution of the core of the cathode electron emitter according to an embodiment of this application;

[0067] Figure 24 is a schematic diagram of the grain morphology distribution of the core of the cathode electron emitter according to an embodiment of this application;

[0068] Figure 25 is a circuit diagram of a frequency converter based on related technologies;

[0069] Figure 26 is a schematic diagram showing the relationship between microwave output power and control current in related technologies;

[0070] Figure 27 is a schematic diagram of the metal band structure in related technologies;

[0071] Figure 28 is a metallographic cross-sectional view of a cathode electron emitter in a related technology;

[0072] Figure 29 is a partial schematic diagram of the metallographic cross-section of a cathode electron emitter in a related technology;

[0073] Figure 30 is a schematic diagram of the grain size distribution of the core of a cathode electron emitter in a related technology;

[0074] Figure 31 is a schematic diagram of the grain morphology distribution of the core of a cathode electron emitter in a related technology;

[0075] Figure 32 is a schematic diagram of the structure of a cathode filament in a related technology;

[0076] Figure 33 shows the relationship between the number of turns of the cathode filament and the internal stress in related technologies;

[0077] Figure 34 is a metallographic cross-section of a cathode filament in a related technology.

[0078] Explanation of the main component reference numerals in Figures 16 to 34: Cathode electron emitter 500, magnetron 600, through hole 50, bracket 52, connecting rod 54, cathode connector 56, end cap 58, anode assembly 60, anode cylinder 62, anode plate 64, interaction space 66, upper magnet 68, lower magnet 70, energy output window 72, core 74, carbonized layer 76, cathode assembly 700. Detailed Implementation

[0079] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0080] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0081] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. They can refer to a mechanical connection or an electrical connection. They can refer to a direct connection or an indirect connection through an intermediate medium, and they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0082] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0083] The following disclosure provides many different embodiments or examples for implementing different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0084] Please refer to Figures 1 to 4. An embodiment of this application provides a cathode filament 100 for use in a magnetron 200. The cathode filament 100 has a helical structure. The filament 12 of the cathode filament 100 includes a filament core 14 and a carbonization layer 16. The carbonization layer 16 covers the filament core 14 at least in the circumferential direction. The material of the filament core 14 includes lanthanum-tungsten material, and the carbonization layer 16 includes a lanthanum-tungsten carbonization layer.

[0085] In the aforementioned cathode filament 100, the filament core 14 is made of lanthanum tungsten material, and the carbide layer 16 is made of lanthanum tungsten carbide layer. This reduces the work function of the cathode filament 100 to a certain extent and enhances the migration ability of rare earth elements in the cathode filament 100, thereby improving the electron emission capability of the cathode filament 100 to a certain extent, so that the magnetron 200 can adapt to the greater power requirements of microwave cooking appliances.

[0086] Specifically, the cathode filament 100 can be applied to the magnetron 200. Referring to Figures 1, 3, and 4, the magnetron 200 includes a cathode assembly 300, which includes a bracket 18, connecting rods 20, and a cathode connector 24. The bracket 18 includes two end caps 26. The two ends of the cathode filament 100 are respectively located within the two end caps 26, and the cathode connector 24 is connected to the two end caps 26 via the two connecting rods 20. The cathode connector 24 can be connected to a power source, which can be provided by the filament winding of a transformer. As shown in Figure 3, when the power source is connected to the cathode connector 24, current is supplied to the cathode filament 100 through the connecting rods 20. The cathode filament 100 spontaneously emits electrons under strong thermal resistance, which are then converted into microwaves by a high-voltage field and a high-magnetic field. Optionally, slots are provided within the end caps 26, and the two ends of the cathode filament 100 are respectively inserted into the slots of the two end caps 26, thereby effectively positioning the cathode filament 100.

[0087] In related technologies, according to market statistics, microwave ovens using magnetrons currently have a minimum output power of 500 watts or more. Lowering the power further leads to unstable microwave output, and in severe cases, no microwave output at all. Specifically, referring to Figure 9, a microwave oven includes an inverter. The inverter adjusts the power by controlling the switching of two IGBTs (Insulated Gate Bipolar Transistors) via a control chip (IC). This maintains a certain current in the system, providing a relatively stable power supply to the magnetron. Current I = Q / t (where I is current, Q represents charge, and t is time). When the switching frequency of the IGBT increases, the amount of charge moving per unit time increases, thus increasing the current; conversely, when the switching rate of the IGBT decreases, the current decreases accordingly. P = U*I (where P is power, U is voltage, and I is current). When the voltage in the system remains constant, changing the operating current changes the output power. Referring to Figure 10, the measured microwave output power is 600 watts, and the input current decreases by 40% compared to the normal current. When the microwave output power is below 500 watts, the input current decreases by about 50% compared to the normal current. The cathode filament 100 emits fewer electrons, making it difficult to form corresponding electron wheels in the cathode and anode, thus leading to unstable microwave power.

[0088] As can be seen from the above, the microwave output power is controlled by the switching frequency of the IGBT. However, the thorium tungsten filament used in the existing magnetrons has a drastic reduction in the number of electrons in the filament below a certain current, making it impossible to use microwave ovens below wattage. For example, it cannot be used in some low-power cooking scenarios (such as microwave heating milk, microwave boiling milk, etc.), which affects the further promotion of microwave ovens.

[0089] In this embodiment, the filament core 14 is made of lanthanum-tungsten, and the carbide layer 16 is a lanthanum-tungsten carbide layer. As shown in Figure 11, when the metal is heated, electrons gain energy to undergo energy level transitions. The work done by an electron escaping from the metal surface (Fermi level) (vacuum level) is called the work function. The smaller the work function, the easier it is for electrons to escape from the metal surface. Therefore, based on this characteristic, this application uses lanthanum instead of thorium, resulting in a lower work function for the cathode filament 100 compared to the original thorium-tungsten filament. Furthermore, the lanthanum-tungsten filament 12 can be further carbonized to adapt to the operating conditions of the magnetron 200. For example, a lanthanum-tungsten carbide layer can be formed on the outer layer of the filament 12 using a carburizing reaction after methane cracking, while the uncarbonized interior forms the filament core 14. This enhances the migration ability of rare earth elements in the cathode filament 100 material and simultaneously homogenizes the entire emission surface, thereby improving the electron emission capability of the cathode filament 100 to a certain extent, allowing the magnetron 200 to meet the higher power requirements of microwave cooking appliances. Furthermore, an orthogonal design can be performed on multiple experimental parameters of the carbonization reaction, ultimately yielding the carbonization layer 16 results shown in Figures 6 and 7.

[0090] The filament core 14 serves two main functions. First, it stabilizes the spiral structure of the cathode filament 100. Second, it forms a lanthanum-tungsten carbide layer. This lanthanum-tungsten carbide layer possesses electron emission capability, primarily due to the electrons generated by the reaction of lanthanum with tungsten carbide and ditungsten carbide. During this process, lanthanum is consumed. Because lanthanum is consumed in the carbide layer 16, a concentration gradient is created, allowing the lanthanum in the filament core 14 to diffuse to the carbide layer 16 for timely replenishment, thus ensuring the continuous electron emission capability of the cathode filament 100.

[0091] The carbide layer 16 covers the filament core 12 at least in the circumferential direction, so that during the operation of the cathode filament 100, the carbide layer 16 emits electrons outward, and the filament core 12 can continuously and timely replenish lanthanum to the carbide layer 16 through diffusion. Optionally, in one embodiment, the carbide layer 16 covers the filament core 12 in both the circumferential and longitudinal directions.

[0092] Please refer to Figures 12 and 13. Figure 12 is a cross-sectional view of the thorium-tungsten filament of the related technology, and Figure 13 is a partially enlarged view of the cross-sectional view of the thorium-tungsten filament of the related technology. As can be seen from Figures 12 and 13, in the related technology, the filament core is blocky, with coarse grains and weak bonding, and the carbide layer is mostly blocky tungsten carbide.

[0093] Referring to Figures 6 and 7, Figure 6 is a cross-sectional view of the filament 12 of the cathode filament 100 comprising lanthanum-tungsten material according to an embodiment of this application, and Figure 7 is a partially enlarged cross-sectional view of the filament 12 of the cathode filament 100 comprising lanthanum-tungsten material according to an embodiment of this application. As can be seen from Figures 6 and 7, in this embodiment, the internal structure of the filament core 14 is compact and has strong breakage resistance. The carbide layer 16 is predominantly composed of fine layered tungsten carbide, increasing the electron emission channel and enhancing the electron emission capability of the cathode filament 100.

[0094] According to actual measurements, referring to Figure 8, under no magnetic field, the total electron current received by the anode of the original filament at a current of 9A is 360mA, while the electron current of the lanthanum-tungsten filament at a current of 9A is 692mA.

[0095] The cathode filament 100 has a helical structure. Specifically, in the embodiment shown in FIG1, the cathode filament 100 has a cylindrical helical structure. During manufacturing, the filament 12 can be wound to form the cathode filament 100 with a cylindrical helical structure.

[0096] It is understandable that the ratio of lanthanum to tungsten can be determined according to specific needs, such as power requirements and cost, and the process parameters of the carbonization process can also be determined according to the design performance. This application does not impose any specific limitations on this.

[0097] In some embodiments, the thickness of the carbonized layer 16 is 6% to 10% of the thickness of the filament 12.

[0098] Therefore, the long-term electron emission capability of the cathode filament 100 can be guaranteed to a certain extent.

[0099] Specifically, referring to Figure 2, the thickness of the carbonized layer 16 is D1, and the thickness of the filament 12 is D2. The thickness of the carbonized layer 16 is 6% to 10% of the thickness of the filament 12, that is, 6% × D2 ≤ D1 ≤ 10% × D2. In Figure 2, the filament 12 is cylindrical, and the thickness D2 of the filament 12 is its diameter. The thickness D1 of the carbonized layer 16 is the difference between the diameter of the filament 12 and the diameter of the filament core 14.

[0100] In some examples, D1 = 6% × D2, 6.5% × D2, 7% × D2, 7.5% × D2, 8% × D2, 8.5% × D2, 9% × D2, 9.5% × D2, 10% × D2, or other values ​​between 6% × D2 and 10% × D2.

[0101] The thickness of the carbonized layer 16 is 6% to 10% of the thickness of the filament 12. The thickness ratio of the carbonized layer 16 is moderate. During the long-term use of the cathode filament 100, it can ensure that the filament core 14 can continuously supply lanthanum to the carbonized layer 16 to a certain extent, so that the carbonized layer 16 has a long-term stable electron emission capability.

[0102] Verification has shown that the thickness of the carbide layer including the lanthanum tungsten carbide layer in the embodiments of this application is 6% to 10% of the thickness of the wire 12, which is 16% thicker than the carbide layer in related technologies. Moreover, the carbide layer 16 in the embodiments of this application is mostly layered channels with a larger crystal gap area, which is more conducive to increasing the electron emission capability of the wire 12.

[0103] In some embodiments, the thickness of the carbonized layer 16 is 8% of the thickness of the filament 12.

[0104] Therefore, the thickness of the carbonized layer 16 can be further prioritized.

[0105] Specifically, the emission performance of the cathode filament 100 is positively correlated with the thickness of the carbide layer 16. Increasing the thickness of the carbide layer 16 will increase the brittleness of the cathode filament 100. Therefore, in order to balance the emission performance and vibration resistance of the cathode filament 100, the thickness D1 of the carbide layer 16 is 8% of the thickness D2 of the wire 12.

[0106] In some embodiments, the thickness D1 of the carbonized layer 16 is 42 μm (micrometers), and the thickness D2 of the filament 12 is 0.5 mm (millimeters).

[0107] This is beneficial for increasing the electron emission capability of the cathode filament 100.

[0108] Specifically, in this embodiment, the thickness of the carbide layer 16 is D1 = 42 μm, and the thickness of the wire 12 is D2 = 0.5 mm. As a comparative example, the thickness of the thorium tungsten carbide layer is about 35 μm. In the cathode filament of this application embodiment, the carbide layer 16 is mostly in the form of layered channels, and the increased crystal gap area compared with the comparative example is more conducive to increasing the electron emission capability of the cathode wire 100.

[0109] In some embodiments, the cathode filament 100 is made of at least one of yttrium, rhenium, lutetium, zirconium, and hafnium.

[0110] This can improve the electron emission capability, melting point, and / or saturated vapor pressure of the cathode filament 100.

[0111] Specifically, adding yttrium to the cathode filament 100 can enhance the electron emission capability of the cathode filament 100, and adding rhenium to the cathode filament 100 can increase the high melting point characteristic of the cathode filament 100, thereby extending the service life of the cathode filament 100.

[0112] In one embodiment, any one or any two or three of lutetium, zirconium, and hafnium can increase the saturated vapor pressure and melting point of the cathode filament 100, hindering the volatilization of lanthanum, thereby achieving a balance between the volatilization and diffusion of the main functional element lanthanum and better maintaining the dynamic balance of lanthanum.

[0113] In one embodiment, the cathode filament 100 material further includes yttrium, rhenium, lutetium, zirconium, or hafnium; that is, yttrium, rhenium, lutetium, zirconium, or hafnium can be added to the lanthanum-tungsten material. In another embodiment, the cathode filament 100 material further includes any two, three, four, or five of yttrium, rhenium, lutetium, zirconium, and hafnium; that is, any two, three, four, or five of yttrium, rhenium, lutetium, zirconium, and hafnium can be added to the lanthanum-tungsten material.

[0114] The proportions of yttrium, rhenium, lutetium, zirconium, and hafnium can be determined based on factors such as the performance enhancement of electron emission capability, the maximum operating temperature of the cathode filament 100, and the saturated vapor pressure. This application does not impose specific limitations on these proportions.

[0115] Optionally, in one embodiment, the cathode filament 100 contains more than 98% tungsten matrix and no more than 2% based on lanthanum and other added elements.

[0116] In some embodiments, the grain size of the filament core 14 ranges from 0.4 μm to 2 μm.

[0117] This is beneficial for increasing the electron emission capability of the cathode filament 100.

[0118] Specifically, the grains of the filament core 14 can be lanthanum-tungsten alloy grains, or lanthanum-tungsten alloy grains with other additive elements. The grain size ranges from 0.4 μm to 2 μm. Referring to Figures 7a and 7b, the lanthanum-tungsten alloy grains of the embodiments of this application are generally smaller and more uniformly distributed than the thorium-tungsten grains of the comparative examples (Figures 14 and 15), which is beneficial for increasing the electron emission capability of the cathode filament 100.

[0119] In some examples, the grain size is 0.4 μm, 0.6 μm, 0.8 μm, 0.87 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.45 μm, 1.6 μm, 1.8 μm, 2 μm, or other values ​​from 0.4 μm to 2 μm. In one example, the average grain size is 0.87 μm.

[0120] In some embodiments, the cathode filament 100 is capable of emitting electrons after being powered on and after being powered off.

[0121] Therefore, even after a power outage, the cathode filament 100 maintains a strong and stable operating performance.

[0122] Specifically, the carbonized layer 16 of the cathode filament 100 in this embodiment has a strong secondary back-bombardment capability. During the operation of the magnetron 200, after the cathode filament 100 is energized and emits electrons, the power to the cathode filament 100 can be cut off. Even after the power is cut off, the cathode filament 100 can still emit electrons to enable the magnetron 200 to generate microwaves for heating food. More specifically, under the influence of the magnetic field of the magnetron 200, some of the emitted electrons will back-bombard the carbonized layer 16. The back-bombarded electrons collide with the carbonized layer 16, thereby causing the carbonized layer 16 to continuously emit new electrons. For example, one back-bombarded electron can cause the emission of two new electrons, and two back-bombarded electrons can cause the emission of four new electrons, etc. Therefore, even if the power to the cathode filament 100 is cut off (equivalent to 0 amp current) after it is energized and emits electrons, the carbonized layer 16 can continue to emit electrons stably under the action of secondary back-bombardment, enabling the magnetron 200 to continuously and stably output microwaves to heat food.

[0123] In some embodiments, the length L of the cathode filament 100 is 12 ± 0.5 mm.

[0124] Therefore, the length of the cathode filament 100 is adapted to the spatial structure of the magnetron 200.

[0125] Specifically, the length L of the cathode filament 100 is 12 ± 0.5 mm, that is, 11.5 mm ≤ L ≤ 12.5 mm. In some examples, L = 11.5 mm, 11.7 mm, 11.9 mm, 12 mm, 12.1 mm, 12.3 mm, 12.5 mm, or other values ​​between 11.5 mm and 12.5 mm.

[0126] During manufacturing, the wire 12 workpiece can be wound to form a cylindrical helical structure. In one example, the diameter of the wire 12 of the cathode filament 100 is 0.5 mm.

[0127] The cathode filament 100 of the aforementioned length can be adapted to the spatial structure of the magnetron 200, enabling the magnetron 200 to be applied to microwave cooking appliances of corresponding structural dimensions, thus improving the versatility of the cathode filament 100.

[0128] In one embodiment, the DC electron emission capability of the cathode filament 100 of this application embodiment is improved by 92% compared with the original product after DC emission test. In addition, the cathode filament 100 has a strong secondary back-bombing capability after being adjusted by the carbonization layer 16 (using electron collision energy to generate new electrons), which means that the cathode filament 100 can maintain stable microwave operation under power failure (0A current) after emitting electrons by heating. Moreover, it has been tested that the microwave cooking appliance can operate stably to heat food when the microwave output power is 100 watts.

[0129] The present application provides a cathode assembly 300 for a magnetron 200, the cathode assembly 300 including the cathode filament 100 of any of the above embodiments.

[0130] In the aforementioned cathode assembly 300, the filament core 14 is made of lanthanum tungsten material, and the carbide layer 16 is made of lanthanum tungsten carbide layer. This reduces the work function of the cathode filament 100 to a certain extent and enhances the migration ability of rare earth elements in the cathode filament 100, thereby improving the electron emission capability of the cathode filament 100 to a certain extent, enabling the magnetron 200 to adapt to the greater power requirements of microwave cooking appliances.

[0131] Specifically, referring to Figure 4, the magnetron 200 includes an anode assembly 400, which includes an anode cylinder 28 and multiple anode plates 30. One end of each anode plate 30 is connected to the side wall of the receiving cavity inside the anode cylinder 28 and is spaced apart along the circumferential direction of the anode cylinder 28. The other ends of the multiple anode plates 30 are suspended to form a receiving space. The cathode filament 100 is disposed in the receiving space, and an interaction space 32 is formed between the cathode filament 100 and the anode plates 30. Referring to Figures 4 and 5, the working principle of the magnetron 200 is as follows: When the magnetron 200 is working, a DC voltage (such as a DC voltage of several kilovolts) is applied between the cathode filament 100 and the anode plates 30. At the same time, the upper magnet 34 and the lower magnet 36 of the magnetron 200 provide a magnetic field to the interaction space 32. The DC electric field and the DC magnetic field in the interaction space 32 are perpendicular to each other. The cathode filament 100 emits electrons, which are accelerated by the electric field and deflected by the magnetic field, undergoing stable oscillating motion in the interaction space 32. The electron velocity is proportional to the ratio E / B, where E is the electric field strength and B is the magnetic flux density. The energy gained by the electron stream emitted by the cathode filament 100 from the electric field in the interaction space 32 is transferred to the high-frequency field under certain conditions and output as microwaves through the energy output window 38.

[0132] In some embodiments, the cathode assembly 300 includes a support 18, which includes two end caps 26, with the two ends of the cathode filament 100 respectively disposed within the two end caps 26.

[0133] This facilitates the installation of the cathode filament 100.

[0134] Specifically, the end caps 26 are provided with slots, and the two ends of the cathode filament 100 are respectively inserted into the slots of the two end caps 26, so that the cathode filament 100 can be easily installed on the bracket 18. The cathode assembly 300 also includes connecting rods 20 and cathode connectors 24, which are connected to the two end caps 26 respectively through the two connecting rods 20. The cathode connectors 24 can be connected to a power source, which can be provided by the filament windings of the transformer.

[0135] Referring to Figure 4, the magnetron 200 provided in this application includes the cathode assembly 300 of any of the above embodiments.

[0136] The microwave cooking appliance provided in this application includes the magnetron 200 of the above embodiment.

[0137] In the aforementioned magnetron and microwave cooking appliance, the filament core 14 is made of lanthanum tungsten material, and the carbide layer is a lanthanum tungsten carbide layer. This reduces the work function of the cathode filament 100 to a certain extent and enhances the migration ability of rare earth elements in the cathode filament 100, thereby improving the electron emission capability of the cathode filament 100 to a certain extent, enabling the magnetron 200 to adapt to the higher power requirements of the microwave cooking appliance.

[0138] Specifically, microwave cooking appliances include, but are not limited to, microwave ovens, microwave-steam-grill combos, and integrated cooktops. The magnetron 200 can be used as a microwave source, and the microwaves generated by the magnetron 200 can be guided into the cooking cavity of the microwave cooking appliance via a waveguide to cook the food inside the cooking cavity.

[0139] In some implementations, the cathode filament 100 is capable of emitting electrons at a minimum output power of 100 watts for a microwave cooking appliance.

[0140] Therefore, the cathode filament 100 can be adapted to more application scenarios of microwave cooking appliances.

[0141] Specifically, microwave cooking appliances with magnetrons 200 are used in scenarios requiring low power, such as microwave heating milk or microwave boiling milk. In one embodiment, the minimum output power of the microwave cooking appliance is 100 watts. The cathode filament 100 of this embodiment can emit electrons even when the minimum output power of the microwave cooking appliance is 100 watts, enabling the microwave cooking appliance to operate normally and provide heating for low power requirements.

[0142] Actual measurements showed that when the cathode filament 100 is used in a microwave cooking appliance with an output power of 100 watts, the microwave cooking appliance can operate stably and heat the food.

[0143] In summary, the cathode filament 100 of this embodiment can be made of lanthanum-tungsten material or lanthanum-tungsten material with other additives, replacing the original thorium-tungsten cathode filament, and the electron work function is reduced by 20% compared to the original material. The thickness of the lanthanum-tungsten carbide layer formed after carbonization treatment accounts for 6% to 10% of the thickness of the filament 12, and the carbide layer 16 is distributed in layers. The emission capability is improved by 92% compared to the original product. The carbide layer 16 of this embodiment can make its secondary back-bombing capability strong, so that secondary electrons are continuously emitted. Therefore, after the cathode filament 100 emits electrons after heating, it can still continue to operate stably under power failure (0A current). When the minimum output power of the microwave cooking appliance is 100 watts, the cathode filament 100 can also enable the magnetron 200 to output stable microwaves, so that the microwave cooking appliance can heat the food.

[0144] In related technologies, microwave ovens include a magnetron with a filament. When energized, the filament heats up and emits electrons, causing the magnetron to output microwaves. During filament manufacturing, a carbonization process is applied. However, carbonization significantly increases the filament's brittleness, making it susceptible to breakage from vibrations during production and even minor impacts from the microwave oven. Once the filament breaks, the entire magnetron becomes open-circuited, preventing microwave generation.

[0145] Please refer to Figures 16 and 19. An embodiment of this application provides a cathode electron emitter 500 used in a magnetron 600. The cathode electron emitter 500 is cylindrical.

[0146] The aforementioned cathode electron emitter 500 is cylindrical, which can effectively improve the internal stress of the cathode electron emitter 500 and reduce the failure rate of the cathode electron emitter 500 to a certain extent.

[0147] Specifically, the cathode electron emitter 500 can be used in the magnetron 600. The cathode electron emitter 500 is cylindrical, and the cylinder is a cylindrical body. Optionally, the cylinder can be formed by forming a smaller cylindrical through hole 50 in the middle of the cylinder. The cylindrical cathode electron emitter 500 can be manufactured by processes including but not limited to stamping, rolling, and spinning.

[0148] In Figure 16, the height of the cathode electron emitter 500 is along the vertical direction. Referring to Figures 19 and 20, the magnetron 600 includes a cathode assembly 700, which includes a bracket 52, connecting rods 54, and a cathode connector 56. The bracket 52 includes two end caps 58. The two ends of the cathode electron emitter 500 are respectively located within the two end caps 58, and the cathode connector 56 is connected to the two end caps 58 via the two connecting rods 54. The cathode connector 56 can be connected to a power source, which can be provided by the filament winding of a transformer. As shown in Figure 19, when the power source is connected to the cathode connector 56, approximately 10A of current is supplied to the cathode electron emitter 500 through the connecting rods 54. The cathode electron emitter 500 spontaneously emits electrons under strong thermal resistance, which are then converted into microwaves by a high-voltage field and a high-magnetic field. Optionally, a slot is provided within the end cap 58, into which one end of the cathode electron emitter 500 can be inserted, thereby effectively positioning the cathode electron emitter 500.

[0149] The cathode electron emitter 500 is cylindrical. Optionally, during manufacturing, a smaller cylindrical through hole 50 can be formed in the middle of the cylindrical workpiece to form the cylindrical cathode electron emitter 500.

[0150] In related technologies, the magnetron is the most crucial component of a microwave oven. The microwaves generated by the magnetron are produced by electrons from the cathode filament, which are heated and then pass through a strong electromagnetic field to form electron spheres. Therefore, the cathode filament is also known as the heart of the magnetron. Referring to Figure 32, in related technologies, the cathode filament 900 has a cylindrical helical structure with a constant pitch. When the cathode filament 900 is energized, the strong heat creates significant stress within the filament, as shown in Figure 33. The stress is greatest in the 2nd and 9th turns (counting from top to bottom). Vibrations during the manufacturing process and minor impacts from the microwave oven can cause the filament to break. Once the filament breaks, the entire magnetron becomes an open circuit, preventing the generation of microwaves. In more serious cases, if a filament break is not detected in time, consumers may find the microwave oven malfunctioning upon first use, impacting user experience and damaging the company's brand image.

[0151] As shown in Figure 16, the cathode electron emitter 500 of this embodiment is cylindrical, which can effectively improve the internal stress of the cathode electron emitter 500. Actual measurements show that its static pressure is increased by 121% compared with the original, which greatly reduces the failure rate of the cathode electron emitter 500.

[0152] Furthermore, referring to Figure 32, in the cathode filament 900 of the related technology, the main emission area is relatively narrow (shown by the dashed box in Figure 32). The cathode filament 900 requires a longer preheating time to generate microwaves, and the uniformity of electron emission in the main emission area is poor, negatively impacting the overall microwave conversion efficiency. In the embodiment of this application, because the cathode electron emitter 500 is cylindrical, the overall structure is changed, and the carbonization layer and core area of ​​the cathode electron emitter 500 are simultaneously improved after processing. In the cross-sectional metallographic image shown in Figure 34, the original filament core is agglomerated after carbonization, and the grains are coarse. However, the cathode electron emitter 500 in this application has fine grains after carbonization, and the grains do not agglomerate, resulting in a compact internal structure. Therefore, the cylindrical cathode electron emitter 500 has a larger overall emission area, and the electrons emitted by the cathode electron emitter 500 form larger spokes, resulting in a significant improvement in microwave efficiency. The middle part is the core 74, and the outer periphery is the carbonization layer 76.

[0153] In some embodiments, referring to Figure 17, the inner diameter of the cathode electron emitter 500 is 2.5 mm to 3.5 mm.

[0154] This can further improve the breakage resistance and electron emission uniformity of the cathode electron emitter 500.

[0155] Specifically, the inner diameter of the cathode electron emitter 500 is R1, where 2.5 mm ≤ R1 ≤ 3.5 mm. In some examples, R1 = 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, or other values ​​between 2.5 mm and 3.5 mm.

[0156] The inner diameter of the cathode electron emitter 500 is 2.5 mm to 3.5 mm. The cathode electron emitter 500 can be structurally coupled with other structures of the magnetron 600, such as the anode assembly 60 and the end cap 58 of the cathode assembly 700, thereby improving the breakage resistance and electron emission uniformity of the cathode electron emitter 500.

[0157] In some embodiments, referring to Figure 17, the outer diameter of the cathode electron emitter 500 is 3.6 mm to 4.5 mm.

[0158] This can further improve the breakage resistance and electron emission uniformity of the cathode electron emitter 500.

[0159] Specifically, the outer diameter of the cathode electron emitter 500 is R2, where 3.6 mm ≤ R2 ≤ 4.5 mm. In some examples, R2 = 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm, 4.0 mm, 4.1 mm, 4.2 mm, 4.3 mm, 4.4 mm, 4.5 mm, or other values ​​between 3.6 mm and 4.5 mm.

[0160] The outer diameter of the cathode electron emitter 500 is 3.6 mm to 4.5 mm. The cathode electron emitter 500 can be structurally coupled with other structures of the magnetron 600, such as the anode assembly 60 and the end cap 58 of the cathode assembly 700, thereby improving the breakage resistance and electron emission uniformity of the cathode electron emitter 500.

[0161] In some embodiments, referring to Figure 18, the height of the cathode electron emitter 500 is 10 mm to 13 mm.

[0162] This can further improve the breakage resistance and electron emission uniformity of the cathode electron emitter 500.

[0163] Specifically, the height of the cathode electron emitter 500 is H, where 10 mm ≤ H ≤ 13 mm. In some examples, H = 10 mm, 10.2 mm, 10.5 mm, 10.8 mm, 11 mm, 11.5 mm, 11.8 mm, 12 mm, 12.5 mm, 12.8 mm, 13 mm, or other values ​​between 10 mm and 13 mm.

[0164] The height of the cathode electron emitter 500 is 10mm to 13mm. The cathode electron emitter 500 can be structurally coupled with other structures of the magnetron 600, such as the anode assembly 60 and the end cap 58 of the cathode assembly 700, thereby improving the breakage resistance and electron emission uniformity of the cathode electron emitter 500.

[0165] In one embodiment, the inner diameter R1 of the cathode electron emitter 500 is 2.5 mm to 3.5 mm, the outer diameter R2 is 3.6 mm to 4.5 mm, and the height H is 10 mm to 13 mm. It can cooperate with other components of the magnetron 600, such as the anode assembly 60 and the end cap 58, which has a better effect on improving the breakage resistance and electron emission uniformity of the cathode electron emitter 500.

[0166] In some embodiments, the cathode electron emitter 500 is made of a tungsten alloy.

[0167] This can improve the performance of the cathode electron emitter 500.

[0168] Specifically, in one embodiment, the melting point of the tungsten alloy is typically between 3420 and 3800°C, which is much higher than that of ordinary metals. This allows the tungsten alloy to remain stable in high-temperature environments when used in the cathode electron emitter 500, making it less prone to melting or deformation, thereby extending the service life of the magnetron 600.

[0169] Tungsten alloys also possess high hardness and strength, enabling them to withstand the impact and vibration of high-frequency electromagnetic fields, thus ensuring the stable performance of the magnetron 600 even in harsh working environments. Tungsten alloys have excellent electrical conductivity, allowing current to flow smoothly through the cathode electron emitter 500, generating sufficient heat to heat it. The heated cathode electron emitter 500 emits more electrons, thereby improving the electron emission efficiency of the magnetron 600. Tungsten alloys exhibit excellent corrosion resistance, resisting corrosion from most acids, alkalis, and salts, allowing the tungsten alloy cathode electron emitter 500 to maintain stable performance in humid or corrosive environments.

[0170] Tungsten alloys include, but are not limited to, thorium tungsten, lanthanum tungsten, yttrium tungsten, and other tungsten alloys used in the magnetron 600 cathode electron emitter 500 of microwave cooking appliances.

[0171] In some embodiments, referring to FIG21, the cathode electron emitter 500 includes a core 74 and a carbide layer 76, the carbide layer 76 covering the core 74 at least in the circumferential direction, the core 74 being made of lanthanum tungsten, and the carbide layer 76 being a lanthanum tungsten carbide layer.

[0172] Therefore, the core 74 is made of lanthanum tungsten material, and the carbide layer 76 is made of lanthanum tungsten carbide layer. This reduces the work function of the cathode electron emitter 500 to a certain extent and improves the migration ability of rare earth elements in the cathode electron emitter 500. This can improve the electron emission capability of the cathode electron emitter 500 to a certain extent, so that the magnetron 600 can adapt to the power requirements of microwave cooking appliances.

[0173] In related technologies, according to current market statistics, microwave ovens using magnetrons have a minimum output power of 500 watts or more. Lowering the power output further leads to unstable microwave output, and in severe cases, no microwave output at all. Specifically, referring to Figure 25, the microwave oven includes an inverter. The inverter adjusts the power by controlling the switching of two IGBTs (Insulated Gate Bipolar Transistors) via a control chip (IC). This maintains a certain current in the system, providing a relatively stable power supply to the magnetron. Current I = Q / t (where I is current, Q represents charge, and t is time). When the switching frequency of the IGBT increases, the amount of charge moving per unit time increases, thus increasing the current; conversely, when the switching rate of the IGBT decreases, the current decreases accordingly. P = U*I (where P is power, U is voltage, and I is current). When the voltage in the system remains constant, changing the operating current changes the output power. Referring to Figure 26, the measured microwave output power is 600 watts, and the input current decreases by 40% compared to the normal current. When the microwave output power is below 500 watts, the input current decreases by about 50% compared to the normal current. The cathode filament emits fewer electrons, making it difficult to form corresponding electron wheels in the cathode and anode, thus leading to unstable microwave power.

[0174] As can be seen from the above, the microwave output power is controlled by the switching frequency of the IGBT. However, the thorium tungsten filament used in the existing magnetrons has a drastic reduction in the number of electrons in the filament below a certain current, making it impossible to use microwave ovens below wattage. For example, it cannot be used in some low-power cooking scenarios (such as microwave heating milk, microwave boiling milk, etc.), which affects the further promotion of microwave ovens.

[0175] In this embodiment, the core 74 is made of lanthanum-tungsten, and the carbide layer 76 is a lanthanum-tungsten carbide layer. As shown in Figure 27, when a metal is heated, electrons gain energy and undergo energy level transitions. The work done by an electron escaping from the metal surface (Fermi level) (vacuum level) is called the work function. The smaller the work function, the easier it is for electrons to escape from the metal surface. Therefore, based on this characteristic, this application uses lanthanum instead of thorium, resulting in a lower work function of the cathode electron emitter 500 than that of the original thorium-tungsten filament. Furthermore, the structure including the lanthanum-tungsten material can be further carbonized to adapt to the operating conditions of the magnetron 600. For example, a lanthanum-tungsten carbide layer can be formed on the outer layer of the structure using a carburizing reaction after methane cracking, while the uncarbonized interior forms the core 74. This enhances the migration ability of rare earth elements in the cathode electron emitter 500 material and simultaneously homogenizes the entire emission surface, thereby improving the electron emission capability of the cathode electron emitter 500 to a certain extent, allowing the magnetron 600 to meet the higher power requirements of microwave cooking appliances.

[0176] The core 74 serves two main functions. First, it stabilizes the cylindrical structure of the cathode electron emitter 500. Second, it forms a lanthanum-tungsten carbide layer. This layer possesses electron emission capability, primarily due to the reaction of lanthanum with tungsten carbide and ditungsten carbide. During this process, lanthanum is consumed. Because lanthanum is consumed in the carbide layer 76, a concentration gradient is created, allowing the lanthanum in the core 74 to diffuse and replenish the carbide layer 76 in a timely manner, thus ensuring the continuous electron emission capability of the cathode electron emitter 500.

[0177] The carbide layer 76 covers the core 74 at least in the circumferential direction, so that during the operation of the cathode electron emitter 500, the carbide layer 76 emits electrons outward, and the core 74 can continuously and timely replenish lanthanum to the carbide layer 76 through diffusion. Optionally, in one embodiment, the carbide layer 76 covers the core 74 in both the circumferential and longitudinal directions.

[0178] Please refer to Figures 28 and 29. Figure 28 is a cross-sectional view of the thorium-tungsten filament of the related technology, and Figure 29 is a partially enlarged view of the cross-sectional view of the thorium-tungsten filament of the related technology. As can be seen from Figures 8 and 29, in the related technology, the core of the thorium-tungsten filament is blocky, with coarse grains and weak bonding, and the carbide layer is mostly blocky tungsten carbide.

[0179] In this embodiment, the cathode electron emitter, comprising lanthanum-tungsten material, has a compact internal structure in its core 74, resulting in strong fracture resistance. The carbide layer 76 is predominantly composed of fine, layered tungsten carbide, which increases the electron emission channel and enhances the electron emission capability of the cathode electron emitter 500.

[0180] It is understandable that the ratio of lanthanum to tungsten can be determined according to specific needs, such as power requirements and cost, and the process parameters of the carbonization process can also be determined according to the design performance. This application does not impose any specific limitations on this.

[0181] In some embodiments, the thickness of the carbide layer 76 is 6% to 10% of the sum of the thicknesses of the carbide layer 76 and the core 74.

[0182] Therefore, the long-term electron emission capability of the cathode electron emitter 500 can be guaranteed to a certain extent.

[0183] Specifically, referring to Figure 21, the thickness of the carbonized layer 76 is D1, the sum of the thicknesses of the carbonized layer 76 and the core 74 is D2, and the thickness of the carbonized layer 76 is 6% to 10% of the sum of the thicknesses of the carbonized layer 76 and the core 74, that is, 6%×D2≤D1≤10%×D2.

[0184] In some examples, D1 = 6% × D2, 6.5% × D2, 7% × D2, 7.5% × D2, 8% × D2, 8.5% × D2, 9% × D2, 9.5% × D2, 10% × D2, or other values ​​between 6% × D2 and 10% × D2.

[0185] The thickness of the carbide layer 76 is 6% to 10% of the sum of the thickness of the carbide layer 76 and the core 74. The thickness ratio of the carbide layer 76 is moderate. During the long-term use of the cathode electron emitter 500, the core 74 can continuously provide lanthanum to the carbide layer 76 to a certain extent, so that the carbide layer 76 has a long-term stable electron emission capability.

[0186] Verification has shown that the thickness of the carbide layer 76, which includes the lanthanum tungsten carbide layer, in the embodiments of this application is 6% to 10% of the sum of the thickness of the carbide layer 76 and the core 74, which is 16% thicker than the carbide layer in related technologies. Moreover, the carbide layer 76 in the embodiments of this application is mostly composed of layered channels with a larger crystal gap area, which is more conducive to increasing the electron emission capability of the cathode electron emitter.

[0187] In some embodiments, the thickness of the carbide layer 76 is 8% of the sum of the thicknesses of the carbide layer 76 and the core 74.

[0188] Therefore, the thickness of the carbonized layer 76 can be further prioritized.

[0189] Specifically, the emission performance of the cathode electron emitter 500 is positively correlated with the thickness of the carbide layer 76. Increasing the thickness of the carbide layer 76 will increase the brittleness of the cathode electron emitter 500. Therefore, in order to balance the emission performance and vibration resistance of the cathode electron emitter 500, the thickness D1 of the carbide layer 76 is 8% of the sum of the thicknesses D2 of the carbide layer 76 and the core 74.

[0190] In some embodiments, the thickness of the carbide layer 76 is 42 μm (micrometers), and the sum of the thicknesses of the carbide layer 76 and the core 74 is 0.5 mm (millimeters).

[0191] This is beneficial for increasing the electron emission capability of the cathode electron emitter 500.

[0192] Specifically, in this embodiment, the thickness of the carbide layer 76 is D1 = 42 μm, and the sum of the thicknesses of the carbide layer 76 and the core 74 is D2 = 0.5 mm. As a comparative example, the thickness of the thorium tungsten carbide layer is about 35 μm. In the cathode electron emitter 500 of this application embodiment, the carbide layer 76 is mostly in the form of layered channels, and the crystal gap area is larger than that of the comparative example, which is more conducive to increasing the electron emission capability of the cathode electron emitter 500.

[0193] In some embodiments, the cathode electron emitter 500 is further made of at least one of yttrium, rhenium, lutetium, zirconium, and hafnium.

[0194] This can improve the electron emission capability, melting point, and / or saturated vapor pressure of the cathode electron emitter 500.

[0195] Specifically, adding yttrium to the cathode electron emitter 500 can enhance the electron emission capability of the cathode electron emitter 500, and adding rhenium to the cathode electron emitter 500 can increase the high melting point characteristic of the cathode electron emitter 500, thereby extending the service life of the cathode electron emitter 500.

[0196] In one embodiment, any one or any two or three of lutetium, zirconium, and hafnium can increase the saturated vapor pressure and melting point of the cathode electron emitter 500, hindering the volatilization of lanthanum, thereby achieving a balance between the volatilization and diffusion of the main functional element lanthanum and better maintaining the dynamic balance of lanthanum.

[0197] In one embodiment, the material of the cathode electron emitter 500 further includes yttrium, rhenium, lutetium, zirconium, or hafnium; that is, yttrium, rhenium, lutetium, zirconium, or hafnium can be added to the lanthanum-tungsten material. In another embodiment, the material of the cathode electron emitter 500 further includes any two, three, four, or five of yttrium, rhenium, lutetium, zirconium, and hafnium; that is, any two, three, four, or five of yttrium, rhenium, lutetium, zirconium, and hafnium can be added to the lanthanum-tungsten material.

[0198] The proportions of yttrium, rhenium, lutetium, zirconium, and hafnium can be determined based on the performance enhancement of electron emission capability, as well as factors such as the maximum operating temperature and saturated vapor pressure of the cathode electron emitter 500. This application does not impose specific limitations on these proportions.

[0199] The aforementioned added elements may be present in the core 74 and the carbonized layer 76.

[0200] Optionally, in one embodiment, the cathode electron emitter 500 contains more than 98% tungsten matrix and no more than 2% lanthanum and other additive elements. It is understood that this application does not limit the proportion of tungsten, lanthanum, or other additive elements in the cathode electron emitter 500.

[0201] In some embodiments, the grain size of the core 74 ranges from 0.4 μm to 2 μm.

[0202] This is beneficial for increasing the electron emission capability of the cathode electron emitter 500.

[0203] Specifically, the grains of the core 74 can be lanthanum-tungsten alloy grains, or alloy grains of lanthanum-tungsten with other additive elements. The grain size ranges from 0.4 μm to 2 μm. Referring to Figures 23 and 24, the lanthanum-tungsten alloy grains of the embodiments of this application are generally smaller and more uniformly distributed than the thorium-tungsten grains of the comparative examples (Figures 30 and 31), which is beneficial to increasing the electron emission capability of the cathode electron emitter 500.

[0204] In some examples, the grain size is 0.4 μm, 0.6 μm, 0.8 μm, 0.87 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.45 μm, 1.6 μm, 1.8 μm, 2 μm, or other values ​​from 0.4 μm to 2 μm. In one example, the average grain size is 0.87 μm.

[0205] In some embodiments, the cathode electron emitter 500 is capable of emitting electrons after being powered on and after being powered off.

[0206] Therefore, even after a power outage, the cathode electron emitter 500 maintains strong and stable operation.

[0207] Specifically, the carbonized layer 76 of the cathode electron emitter 500 in this embodiment has a strong secondary back-bombing capability. During the operation of the magnetron 600, after the cathode electron emitter 500 is energized and emits electrons, the power to the cathode electron emitter 500 can be cut off. Even after the power is cut off, the cathode electron emitter 500 can still emit electrons to enable the magnetron 600 to generate microwaves for heating food. More specifically, under the influence of the magnetic field of the magnetron 600, some of the emitted electrons will back-bomb the carbonized layer 76. The back-bombing electrons collide with the carbonized layer 76, thereby causing the carbonized layer 76 to continuously emit new electrons. For example, one back-bombing electron can cause the emission of two new electrons, and two back-bombing electrons can cause the emission of four new electrons, etc. Therefore, even if the power to the cathode electron emitter 500 is cut off (equivalent to 0 amp current) after it is energized and emits electrons, the carbonized layer 76 can continue to emit electrons stably under the action of secondary back-bombing, enabling the magnetron 600 to continuously and stably output microwaves to heat food.

[0208] Referring to Figures 19 and 20, an embodiment of this application provides a cathode assembly 700 for use with a magnetron 600. The cathode assembly 700 includes the cathode electron emitter 500 of any of the above embodiments.

[0209] In the aforementioned cathode assembly 700, the cathode electron emitter 500 is cylindrical, which can effectively improve the internal stress of the cathode electron emitter 500 and reduce the failure rate of the cathode electron emitter 500 to a certain extent.

[0210] Specifically, referring to Figure 20, the magnetron 600 includes a cathode assembly 700 and an anode assembly 60. The anode assembly 60 includes an anode cylinder 62 and multiple anode plates 64. One end of each anode plate 64 is connected to the side wall of the receiving cavity inside the anode cylinder 62 and is spaced apart along the circumferential direction of the anode cylinder 62. The other ends of the multiple anode plates 64 are suspended to form a receiving space. A cathode electron emitter 500 is disposed in the receiving space, and an interaction space 66 is formed between the cathode electron emitter 500 and the anode plates 64. The working principle of the magnetron 600 is as follows: When the magnetron 600 is working, a DC voltage (such as a DC voltage of several kilovolts) is applied between the cathode electron emitter 500 and the anode plates 64. At the same time, the upper magnet 68 and the lower magnet 70 of the magnetron 600 provide a magnetic field to the interaction space 66. The DC electric field and the DC magnetic field in the interaction space 66 are perpendicular to each other. The cathode electron emitter 500 emits electrons, which are accelerated by the electric field and deflected by the magnetic field, undergoing stable oscillating motion in the interaction space 66. The electron velocity is proportional to the ratio E / B, where E is the electric field strength and B is the magnetic flux density. The electron stream emitted by the cathode electron emitter 500 gains energy from the electric field in the interaction space 66. Under certain conditions, this energy is transferred to the high-frequency field and output as microwaves through the energy output window 72.

[0211] In some embodiments, referring to FIG19, the cathode assembly 700 includes a support 52, the support 52 includes two end caps 58, and the two ends of the cathode electron emitter 500 are respectively disposed in the two end caps 58.

[0212] This facilitates the installation of the cathode electron emitter 500.

[0213] Specifically, the end cap 58 is provided with slots, and the two ends of the cathode electron emitter 500 can be placed in the slots of the two end caps 58, so that the cathode electron emitter 500 can be conveniently installed on the bracket 52.

[0214] In some embodiments, referring to FIG19, the cathode assembly 700 includes a connecting rod 54 and a cathode connector 56, with two end caps 58 connected to the cathode connector 56 respectively via the connecting rod 54.

[0215] This allows for the formation of an electrical connection path for the cathode assembly 700.

[0216] Specifically, the cathode connector 56 is connected to two end caps 58 via two connecting rods 54, allowing current to flow into and out of the cathode electron emitter 500 through the cathode connector 56, connecting rods 54, and end caps 58. The cathode connector 56 can be connected to a power source, which can be provided by the filament winding of a transformer. As shown in Figure 19, when the power is turned on at the cathode connector 56, approximately 10A of current is supplied to the cathode electron emitter 500 through the connecting rods 54. The cathode electron emitter 500 spontaneously emits electrons under strong thermal resistance, which are then converted into microwaves by a high-voltage field and a high-magnetic field.

[0217] Referring to Figure 30, an embodiment of this application provides a magnetron 600 including the cathode assembly 700 of any of the above embodiments.

[0218] The microwave cooking appliance provided in this application includes the magnetron 600 of the above embodiment.

[0219] In the aforementioned magnetron 600 and microwave cooking appliance, the cathode electron emitter 500 is cylindrical, which can effectively improve the internal stress of the cathode electron emitter 500 and reduce the failure rate of the cathode electron emitter 500 to a certain extent.

[0220] Specifically, microwave cooking appliances include, but are not limited to, microwave ovens, microwave-steam-grill combos, and integrated cooktops. The magnetron 600 can be used as a microwave source, and the microwaves generated by the magnetron 600 can be guided into the cooking cavity of the microwave cooking appliance via a waveguide to cook the food inside the cooking cavity.

[0221] In some embodiments, the cathode electron emitter 500 includes a core 74 and a carbide layer 76, the carbide layer 76 covering the core 74 at least in the circumferential direction, the core 74 being made of lanthanum tungsten, and the carbide layer 76 being a lanthanum tungsten carbide layer, and the cathode electron emitter 500 is capable of emitting electrons with a minimum output power of 100 watts in a microwave cooking appliance.

[0222] Therefore, the cathode electron emitter 500 can be adapted to more application scenarios of microwave cooking appliances.

[0223] Specifically, microwave cooking appliances with magnetrons 600 are used in scenarios requiring low power, such as microwave heating milk or microwave boiling milk. In one embodiment, the minimum output power of the microwave cooking appliance is 100 watts. The cathode electron emitter 500 of this application embodiment can emit electrons even when the minimum output power of the microwave cooking appliance is 100 watts, enabling the microwave cooking appliance to operate normally and provide heating for low power requirements.

[0224] Actual measurements showed that the cathode electron emitter 500 could stably heat food in a microwave cooking appliance with an output power of 100 watts.

[0225] In summary, the technical solution of this application, by introducing a cylindrical cathode electron emitter 500, increases the static pressure of the cathode electron emitter 500 by 121% and significantly reduces the failure rate of the cathode electron emitter 500. Moreover, the effective area of ​​the cathode electron emitter 500 in the emission region is more concentrated, the effective emission area is increased, the electron emission homogenization is increased, and the oscillation start-up time can be accelerated by 13%.

[0226] Furthermore, the cathode electron emitter 500 of this embodiment can be made of lanthanum-tungsten material or lanthanum-tungsten material with other additives, replacing the original thorium-tungsten cathode filament, reducing the electron work function by 20% compared to the original material. The thickness of the lanthanum-tungsten carbide layer formed after carbonization treatment accounts for 6% to 10% of the sum of the thickness of the carbide layer 76 and the core 74, and the carbide layer 76 is distributed in layers. Its emission capability is improved by 92% compared to the original product. The carbide layer 76 of this embodiment can make its secondary back-bombing capability strong, so that secondary electrons are continuously emitted. Therefore, after the cathode electron emitter 500 emits electrons by heating, it can still operate stably under power failure (0A current). When the minimum output power of the microwave cooking appliance is 100 watts, the cathode electron emitter 500 can also enable the magnetron 600 to output stable microwaves, so that the microwave cooking appliance can heat the food.

[0227] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with an embodiment or example that are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0228] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A cathode filament for use in a magnetron, characterized in that, The cathode filament has a spiral structure, and the filament material includes a filament core and a carbonized layer. The carbonized layer covers the filament core at least in the circumferential direction. The material of the filament core includes lanthanum-tungsten material, and the carbonized layer includes a lanthanum-tungsten carbonized layer.

2. The cathode filament according to claim 1, characterized in that, The thickness of the carbonized layer is 6% to 10% of the thickness of the filament.

3. The cathode filament according to claim 1 or 2, characterized in that, The thickness of the carbonized layer is 8% of the thickness of the filament.

4. The cathode filament according to any one of claims 1-3, characterized in that, The thickness of the carbonized layer is 42 μm, and the thickness of the filament is 0.5 mm.

5. The cathode filament according to any one of claims 1-4, characterized in that, The cathode filament material also includes at least one of yttrium, rhenium, lutetium, zirconium, and hafnium.

6. The cathode filament according to any one of claims 1-5, characterized in that, The grain size of the filament core ranges from 0.4 μm to 2 μm.

7. The cathode filament according to any one of claims 1-6, characterized in that, The cathode filament is capable of emitting electrons after being powered on and continuing to emit electrons after the power is turned off.

8. The cathode filament according to any one of claims 1-7, characterized in that, The length of the cathode filament is 12±0.5mm.

9. A cathode assembly for a magnetron, characterized in that, The cathode assembly includes the cathode filament as described in any one of claims 1-8.

10. The cathode assembly according to claim 9, characterized in that, The cathode assembly includes a support, which includes two end caps, and the two ends of the cathode filament are respectively disposed in the two end caps.

11. A magnetron, characterized in that, Includes the cathode assembly as described in claim 9 or 10.

12. A microwave cooking appliance, characterized in that, Including the magnetron of claim 11.

13. The microwave cooking appliance according to claim 12, characterized in that, The cathode filament is capable of emitting electrons at a minimum output power of 100 watts in the microwave cooking appliance.

14. A cathode electron emitter for use in a magnetron, characterized in that, The cathode electron emitter is cylindrical.

15. The cathode electron emitter according to claim 14, characterized in that, The inner diameter of the cathode electron emitter is 2.5 mm to 3.5 mm.

16. The cathode electron emitter according to claim 14 or 15, characterized in that, The outer diameter of the cathode electron emitter is 3.6 mm to 4.5 mm.

17. The cathode electron emitter according to any one of claims 14-16, characterized in that, The height of the cathode electron emitter is 10 mm to 13 mm.

18. The cathode electron emitter according to any one of claims 14-17, characterized in that, The cathode electron emitter is made of tungsten alloy.

19. The cathode electron emitter according to any one of claims 14-18, characterized in that, The cathode electron emitter includes a core and a carbide layer, the carbide layer covering the core at least in the circumferential direction, the core being made of lanthanum-tungsten material, and the carbide layer being a lanthanum-tungsten carbide layer.

20. The cathode electron emitter according to claim 19, characterized in that, The thickness of the carbonized layer is 6% to 10% of the sum of the thickness of the carbonized layer and the core.

21. The cathode electron emitter according to claim 19 or 20, characterized in that, The thickness of the carbonized layer is 8% of the sum of the thickness of the carbonized layer and the core.

22. The cathode electron emitter according to any one of claims 19-21, characterized in that, The thickness of the carbonized layer is 42 μm, and the sum of the thicknesses of the carbonized layer and the core is 0.5 mm.

23. The cathode electron emitter according to any one of claims 19-22, characterized in that, The cathode electron emitter is also made of at least one of yttrium, rhenium, lutetium, zirconium, and hafnium.

24. The cathode electron emitter according to any one of claims 19-23, characterized in that, The grain size of the core ranges from 0.4 μm to 2 μm.

25. The cathode electron emitter according to any one of claims 19-24, characterized in that, The cathode electron emitter is capable of emitting electrons after being powered on and continuing to emit electrons after the power is turned off.

26. A cathode assembly for a magnetron, characterized in that, The cathode assembly includes the cathode electron emitter as described in any one of claims 14-25.

27. The cathode assembly according to claim 26, characterized in that, The cathode assembly includes a support, which includes two end caps, and the two ends of the cathode electron emitter are respectively disposed in the two end caps.

28. A magnetron, characterized in that, Includes the cathode assembly as described in claim 26 or 27.

29. A microwave cooking appliance, characterized in that, Including the magnetron of claim 28.

30. The microwave cooking appliance according to claim 29, characterized in that, The cathode electron emitter includes a core and a carbonized layer, the carbonized layer covering the core at least in the circumferential direction, the core being made of lanthanum-tungsten material, and the carbonized layer being a lanthanum-tungsten carbonized layer. The cathode electron emitter is capable of emitting electrons when the minimum output power of the microwave cooking appliance is 100 watts.

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