Cathode electron emitter, cathode assembly, magnetron and microwave cooking appliance

Abstract

The utility model discloses a cathode electron emitter, cathode assembly, magnetron and microwave cooking electric appliance. The cathode electron emitter is used for the magnetron, and the cathode electron emitter is cylindrical. The above-mentioned cathode electron emitter is cylindrical, can effectively improve the internal stress of the cathode electron emitter, and reduces the breakage quality defective rate of the cathode electron emitter to a certain extent.

Description

[0001] Priority information

[0002] This utility model claims priority and benefits to patent application No. 202422953101.2, filed with the China National Intellectual Property Administration on November 29, 2024, the entire contents of which are incorporated herein by reference. Technical Field

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

[0004] 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. Utility Model Content

[0005] This invention provides 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 utility model provides a cathode electron emitter for a magnetron, wherein the cathode electron emitter is cylindrical.

[0007] 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.

[0008] In some embodiments, the inner diameter of the cathode electron emitter is 2.5 mm to 3.5 mm.

[0009] In some embodiments, the outer diameter of the cathode electron emitter is 3.6 mm to 4.5 mm.

[0010] In some embodiments, the height of the cathode electron emitter is 10 mm to 13 mm.

[0011] In some embodiments, the cathode electron emitter is made of a tungsten alloy.

[0012] 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.

[0013] 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.

[0014] In some embodiments, the thickness of the carbonized layer is 8% of the sum of the thickness of the carbonized layer and the core.

[0015] 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.

[0016] In some embodiments, the cathode electron emitter is further made of at least one of yttrium, rhenium, lutetium, zirconium, and hafnium.

[0017] In some embodiments, the grain size of the core ranges from 0.4 μm to 2 μm.

[0018] 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.

[0019] This invention provides a cathode assembly for a magnetron, the cathode assembly including a cathode electron emitter according to any of the above embodiments.

[0020] 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.

[0021] The present invention provides a magnetron including the cathode assembly of any of the above embodiments.

[0022] The present invention provides a microwave cooking appliance including the magnetron described in the above embodiment.

[0023] 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.

[0024] 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.

[0025] Additional aspects and advantages of this invention 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 the invention. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this utility model 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 utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0027] Figure 1 This is a three-dimensional schematic diagram of the cathode electron emitter according to an embodiment of the present invention;

[0028] Figures 2 to 3 This is a schematic diagram showing the dimensions of the cathode electron emitter according to an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the cathode assembly according to an embodiment of the present invention;

[0030] Figure 5 This is a cross-sectional schematic diagram of the magnetron according to an embodiment of the present invention;

[0031] Figure 6 This is a cross-sectional schematic diagram of the cathode electron emitter according to an embodiment of the present invention;

[0032] Figure 7 This is a schematic diagram of the operation of the magnetron electrons in an embodiment of the present invention.

[0033] Figure 8 This is a schematic diagram of the grain size distribution of the core of the cathode electron emitter according to an embodiment of the present invention;

[0034] Figure 9 This is a schematic diagram of the grain morphology distribution of the core of the cathode electron emitter according to an embodiment of the present invention;

[0035] Figure 10 This is a circuit diagram of a frequency converter based on related technologies;

[0036] Figure 11 This is a schematic diagram illustrating the relationship between microwave output power and control current in related technologies;

[0037] Figure 12 This is a schematic diagram of the metal band structure in related technologies;

[0038] Figure 13 A metallographic cross-sectional schematic diagram of a cathode electron emitter in a related technology;

[0039] Figure 14 This is a partial schematic diagram of the metallographic cross-section of a cathode electron emitter in a related technology.

[0040] Figure 15 This is a schematic diagram of the grain size distribution in the core of a cathode electron emitter in a related technology.

[0041] Figure 16 This is a schematic diagram of the grain morphology distribution in the core of a cathode electron emitter in a related technology.

[0042] Figure 17 This is a schematic diagram of the structure of a cathode filament in a related technology;

[0043] Figure 18 This is a diagram showing the relationship between the number of turns of the cathode filament and the internal stress in related technologies.

[0044] Figure 19 This is a metallographic cross-section of a cathode filament in a related technology.

[0045] Explanation of key component reference numerals:

[0046] Cathode electron emitter 100, magnetron 200, through hole 10, bracket 12, connecting rod 14, cathode connector 16, end cap 18, anode assembly 20, anode cylinder 22, anode plate 24, interaction space 26, upper magnet 28, lower magnet 30, energy output window 32, core 34, carbonization layer 36, cathode assembly 300. Detailed Implementation

[0047] The embodiments of this utility model 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 utility model, and should not be construed as limiting this utility model.

[0048] In the description of this utility model, 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 the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description. They 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 utility model. 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 utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0049] In the description of this utility model, it should be noted that, unless otherwise explicitly 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 utility model can be understood according to the specific circumstances.

[0050] In this invention, unless otherwise explicitly 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 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 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.

[0051] The following disclosure provides many different embodiments or examples for implementing various structures of this invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of the invention. 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, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0052] Please refer to Figure 1 and Figure 4 The present invention provides a cathode electron emitter 100 for use in a magnetron 200. The cathode electron emitter 100 is cylindrical.

[0053] The aforementioned cathode electron emitter 100 is cylindrical, which can effectively improve the internal stress of the cathode electron emitter 100 and reduce the failure rate of the cathode electron emitter 100 to a certain extent.

[0054] Specifically, the cathode electron emitter 100 can be used in the magnetron 200. The cathode electron emitter 100 is cylindrical, and the cylinder is a cylindrical body. Optionally, the cylinder can be formed by forming a smaller cylindrical through hole 10 in the middle of the cylinder. The cylindrical cathode electron emitter 100 can be manufactured by processes including but not limited to stamping, rolling, and spinning.

[0055] exist Figure 1 In the image, the height of the cathode electron emitter 100 is along the vertical direction. Please refer to... Figure 4 and Figure 5 The magnetron 200 includes a cathode assembly 300, which includes a bracket 12, connecting rods 14, and a cathode connector 16. The bracket 12 includes two end caps 18. The two ends of the cathode electron emitter 100 are respectively disposed within the two end caps 18, and the cathode connector 16 is connected to the two end caps 18 respectively via the two connecting rods 14. The cathode connector 16 can be connected to a power source, which can be provided by the filament winding of a transformer. Figure 4 As shown, when the power is turned on at the cathode connector 16, approximately 10A of current is supplied to the cathode electron emitter 100 via the connecting rod 14. The cathode electron emitter 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, a slot is provided inside the end cap 18, into which one end of the cathode electron emitter 100 can be inserted, thereby enabling effective positioning of the cathode electron emitter 100.

[0056] The cathode electron emitter 100 is cylindrical. Optionally, during manufacturing, a smaller cylindrical through hole 10 can be formed in the middle of the cylindrical workpiece to form the cylindrical cathode electron emitter 100.

[0057] In related technologies, the magnetron is the most crucial component of a microwave oven. The microwaves generated by the magnetron are produced by electrons supplied by the heating of the cathode filament passing through a strong electromagnetic field to form electron spheres. Therefore, the cathode filament is also known as the heart of the magnetron. Please refer to... Figure 17 In related technologies, the cathode filament 400 has a cylindrical helical structure with a constant pitch. When the cathode filament 400 is energized, the strong heat effect causes strong stress inside the filament, such as... Figure 18 As shown, the second and ninth rings are the largest (counting from top to bottom). Vibrations during the production process and slight collisions with the microwave oven can cause the filament to break. Once the filament breaks, the entire magnetron will become an open circuit and will not be able to generate microwaves. Even worse, if the filament break is not detected in time, consumers will find that the microwave oven does not work when they use it for the first time, which will affect the user experience and also cause some damage to the company's brand image.

[0058] like Figure 1As shown, the cathode electron emitter 100 of this utility model is cylindrical, which can effectively improve the internal stress of the cathode electron emitter 100. 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 100.

[0059] Additionally, please combine Figure 17 In the cathode filament 400 of the related technology, the main emission area is relatively narrow ( Figure 17 As shown in the dashed box, the cathode filament 400 requires a relatively long 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 this embodiment of the invention, because the cathode electron emitter 100 is cylindrical, the overall structure is changed, and the carbonization layer and core area of ​​the cathode electron emitter 100 are simultaneously improved after treatment. Figure 19 In the cross-sectional metallographic image shown, the original filament, after carbonization, had a hardened core with coarse grains. In contrast, the cathode electron emitter 100 of this invention, after carbonization, has fine grains that do not agglomerate, resulting in a compact internal structure. Therefore, the cylindrical cathode electron emitter 100, due to its increased overall emission area, produces a larger emission radius, significantly improving microwave efficiency. The middle section is the core 34, and the outer periphery is the carbonized layer 36.

[0060] In some implementations, please refer to Figure 2 The inner diameter of the cathode electron emitter 100 is 2.5 mm to 3.5 mm.

[0061] This can further improve the breakage resistance and electron emission uniformity of the cathode electron emitter 100.

[0062] Specifically, the inner diameter of the cathode electron emitter 100 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.

[0063] The inner diameter of the cathode electron emitter 100 is 2.5 mm to 3.5 mm. The cathode electron emitter 100 can be structurally coupled with other structures of the magnetron 200, such as the anode assembly 20 and the end cap 18 of the cathode assembly 300, thereby improving the breakage resistance and electron emission uniformity of the cathode electron emitter 100.

[0064] In some implementations, please refer to Figure 2 The outer diameter of the cathode electron emitter 100 is 3.6 mm to 4.5 mm.

[0065] This can further improve the breakage resistance and electron emission uniformity of the cathode electron emitter 100.

[0066] Specifically, the outer diameter of the cathode electron emitter 100 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.

[0067] The outer diameter of the cathode electron emitter 100 is 3.6 mm to 4.5 mm. The cathode electron emitter 100 can be structurally coupled with other structures of the magnetron 200, such as the anode assembly 20 and the end cap 18 of the cathode assembly 300, thereby improving the breakage resistance and electron emission uniformity of the cathode electron emitter 100.

[0068] In some implementations, please refer to Figure 3 The height of the cathode electron emitter 100 is 10 mm to 13 mm.

[0069] This can further improve the breakage resistance and electron emission uniformity of the cathode electron emitter 100.

[0070] Specifically, the height of the cathode electron emitter 100 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.

[0071] The height of the cathode electron emitter 100 is 10mm to 13mm. The cathode electron emitter 100 can be structurally coupled with other structures of the magnetron 200, such as the anode assembly 20 and the end cap 18 of the cathode assembly 300, thereby improving the breakage resistance and electron emission uniformity of the cathode electron emitter 100.

[0072] In one embodiment, the inner diameter R1 of the cathode electron emitter 100 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 200, such as the anode assembly 20 and the end cap 18, which has a better effect on improving the breakage resistance and electron emission uniformity of the cathode electron emitter 100.

[0073] In some embodiments, the cathode electron emitter 100 is made of a tungsten alloy.

[0074] This can improve the performance of the cathode electron emitter 100.

[0075] 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 100, making it less prone to melting or deformation, thereby extending the service life of the magnetron 200.

[0076] Tungsten alloys also possess high hardness and strength, enabling them to withstand the impact and vibration of high-frequency electromagnetic fields, thus ensuring the magnetron 200 maintains stable performance even in harsh working environments. Tungsten alloys have excellent electrical conductivity, allowing current to flow smoothly through the cathode electron emitter 100, generating sufficient heat to heat it. The heated cathode electron emitter 100 emits more electrons, thereby improving the electron emission efficiency of the magnetron 200. Tungsten alloys exhibit excellent corrosion resistance, resisting corrosion from most acids, alkalis, and salts, allowing the tungsten alloy cathode electron emitter 100 to maintain stable performance in humid or corrosive environments.

[0077] Tungsten alloys include, but are not limited to, thorium tungsten, lanthanum tungsten, yttrium tungsten, and other tungsten alloys used in the magnetron 200 cathode electron emitter 100 of microwave cooking appliances.

[0078] In some implementations, please refer to Figure 6 The cathode electron emitter 100 includes a core 34 and a carbide layer 36. The carbide layer 36 covers the core 34 at least in the circumferential direction. The core 34 is made of lanthanum tungsten, and the carbide layer 36 is a lanthanum tungsten carbide layer.

[0079] Therefore, the core 34 is made of lanthanum tungsten material, and the carbide layer 36 is made of lanthanum tungsten carbide layer. This reduces the work function of the cathode electron emitter 100 to a certain extent and improves the migration ability of rare earth elements in the cathode electron emitter 100. This can improve the electron emission capability of the cathode electron emitter 100 to a certain extent, so that the magnetron 200 can adapt to the higher power requirements of microwave cooking appliances.

[0080] 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 further will result in unstable microwave output, and in severe cases, no microwave output at all. For specific details, please refer to… Figure 10Microwave ovens include inverters. The principle behind inverter power adjustment is that a control chip (IC) controls the switching on and off of two IGBTs (Insulated Gate Bipolar Transistors), maintaining a certain current in the system and thus providing a relatively stable power supply to the magnetron. Current I = Q / t (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, and therefore the current increases; conversely, when the switching rate of the IGBT decreases, the current decreases accordingly. P = U*I (P is power, U is voltage, and I is current). When the voltage in the system remains constant, changing the magnitude of the operating current changes the output power. Please refer to... Figure 11 The measured microwave output power was 600 watts, and the input current decreased by 40% compared to the normal current. When the microwave output power was below 500 watts, the input current decreased by about 50% compared to the normal current. The cathode filament emitted fewer electrons, making it difficult to form corresponding electron wheels in the cathode and anode, thus resulting in unstable microwave power.

[0081] 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.

[0082] In this embodiment of the invention, the core 34 is made of lanthanum-tungsten, and the carbide layer 36 is a lanthanum-tungsten carbide layer. For example... Figure 12 As shown, 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 invention uses lanthanum instead of thorium, resulting in a lower work function for the cathode electron emitter 100 compared to the original thorium-tungsten filament. Furthermore, the structure, including lanthanum-tungsten materials, 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 structure using a carburizing reaction after methane cracking, while the uncarbonized interior forms the core 34. This enhances the migration ability of rare earth elements in the cathode electron emitter 100 material and simultaneously homogenizes the entire emission surface, thereby improving the electron emission capability of the cathode electron emitter 100 to a certain extent, allowing the magnetron 200 to meet the higher power requirements of microwave cooking appliances.

[0083] The core 34 serves two main functions. First, it stabilizes the cylindrical structure of the cathode electron emitter 100. Second, it forms a lanthanum-tungsten carbide layer. This 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 36, a concentration gradient is created, allowing the lanthanum in the core 34 to diffuse and replenish the carbide layer 36 in a timely manner, thus ensuring the continuous electron emission capability of the cathode electron emitter 100.

[0084] The carbide layer 36 covers the core 34 at least in the circumferential direction, so that during the operation of the cathode electron emitter 100, the carbide layer 36 emits electrons outward, and the core 34 can continuously and timely replenish lanthanum to the carbide layer 36 through diffusion. Optionally, in one embodiment, the carbide layer 36 covers the core 34 in both the circumferential and longitudinal directions.

[0085] Please combine Figure 13 and Figure 14 , Figure 13 This is a cross-sectional view of the thorium-tungsten filament material in related technologies. Figure 14 This is a partially enlarged view of the cross-section of a thorium-tungsten filament from a related technology. Figure 13 and Figure 14 It can be seen that in the relevant technologies, the core of the thorium tungsten filament is blocky with coarse grains and weak bonding force, and the carbide layer is mostly blocky tungsten carbide.

[0086] In this embodiment of the invention, the cathode electron emitter, comprising lanthanum-tungsten material, has a compact internal structure in the core 34, resulting in strong fracture resistance. The carbide layer 36 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 100.

[0087] It is understood 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 utility model does not make any specific limitations in this regard.

[0088] In some embodiments, the thickness of the carbide layer 36 is 6% to 10% of the sum of the thicknesses of the carbide layer 36 and the core 34.

[0089] Therefore, the long-term electron emission capability of the cathode electron emitter 100 can be guaranteed to a certain extent.

[0090] Specifically, please combine Figure 6 The thickness of the carbonized layer 36 is D1, and the sum of the thicknesses of the carbonized layer 36 and the core 34 is D2. The thickness of the carbonized layer 36 is 6% to 10% of the sum of the thicknesses of the carbonized layer 36 and the core 34, that is, 6%×D2≤D1≤10%×D2.

[0091] 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.

[0092] The thickness of the carbide layer 36 is 6% to 10% of the sum of the thickness of the carbide layer 36 and the core 34. The thickness ratio of the carbide layer 36 is moderate. During the long-term use of the cathode electron emitter 100, the core 34 can continuously provide lanthanum to the carbide layer 36 to a certain extent, so that the carbide layer 36 has a long-term stable electron emission capability.

[0093] Verification has shown that the thickness of the carbide layer 36, which includes the lanthanum tungsten carbide layer, in this embodiment of the present invention is 6% to 10% of the sum of the thickness of the carbide layer 36 and the core 34, which is 16% thicker than the carbide layer in related technologies. Moreover, the carbide layer 36 in this embodiment of the present invention 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.

[0094] In some embodiments, the thickness of the carbide layer 36 is 8% of the sum of the thicknesses of the carbide layer 36 and the core 34.

[0095] Therefore, the thickness of the carbonized layer 36 can be further prioritized.

[0096] Specifically, the emission performance of the cathode electron emitter 100 is positively correlated with the thickness of the carbide layer 36. Increasing the thickness of the carbide layer 36 will increase the brittleness of the cathode electron emitter 100. Therefore, in order to balance the emission performance and vibration resistance of the cathode electron emitter 100, the thickness D1 of the carbide layer 36 is 8% of the sum of the thicknesses D2 of the carbide layer 36 and the core 34.

[0097] In some embodiments, the thickness of the carbide layer 36 is 42 μm (micrometers), and the sum of the thicknesses of the carbide layer 36 and the core 34 is 0.5 mm (millimeters).

[0098] This is beneficial for increasing the electron emission capability of the cathode electron emitter 100.

[0099] Specifically, in this embodiment, the thickness of the carbide layer 36 is D1 = 42 μm, and the sum of the thicknesses of the carbide layer 36 and the core 34 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 100 of this embodiment, the carbide layer 36 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 100.

[0100] In some embodiments, the cathode electron emitter 100 is made of at least one of yttrium, rhenium, lutetium, zirconium, and hafnium.

[0101] This can improve the electron emission capability, melting point, and / or saturated vapor pressure of the cathode electron emitter 100.

[0102] Specifically, adding yttrium to the cathode electron emitter 100 can enhance the electron emission capability of the cathode electron emitter 100, and adding rhenium to the cathode electron emitter 100 can increase the high melting point characteristic of the cathode electron emitter 100, thereby extending the service life of the cathode electron emitter 100.

[0103] 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 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.

[0104] In one embodiment, the material of the cathode electron emitter 100 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 100 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.

[0105] 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 100. This invention does not impose specific limitations on these proportions.

[0106] The aforementioned added elements may be present in the core 34 and the carbonized layer 36.

[0107] Optionally, in one embodiment, the tungsten matrix content of the cathode electron emitter 100 exceeds 98%, and the content of lanthanum and other additive elements does not exceed 2%. It is understood that this invention does not limit the tungsten content, lanthanum content, or the content of other additive elements in the cathode electron emitter 100.

[0108] In some embodiments, the grain size of the core 34 ranges from 0.4 μm to 2 μm.

[0109] This is beneficial for increasing the electron emission capability of the cathode electron emitter 100.

[0110] Specifically, the grains of core 34 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. Please refer to... Figure 8 and Figure 9 The average grain size of the lanthanum-tungsten alloy in this embodiment of the invention is compared with that in the comparative example (e.g., Figure 15 and Figure 16 The thorium-tungsten grains are small and uniformly distributed, which helps to increase the electron emission capability of the cathode electron emitter 100.

[0111] 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.

[0112] In some embodiments, the cathode electron emitter 100 is capable of emitting electrons after being powered on and after being powered off.

[0113] Therefore, even after a power outage, the cathode electron emitter 100 maintains a strong and stable operating performance.

[0114] Specifically, the carbonized layer 36 of the cathode electron emitter 100 in this embodiment of the invention has a strong secondary back-bombing capability. During the operation of the magnetron 200, after the cathode electron emitter 100 is energized and emits electrons, the power to the cathode electron emitter 100 can be cut off. Even after the power is cut off, the cathode electron emitter 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-bomb the carbonized layer 36. The back-bombing electrons collide with the carbonized layer 36, thereby causing the carbonized layer 36 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 100 is cut off (equivalent to 0 amp current) after it is energized and emits electrons, the carbonized layer 36 can continue to emit electrons stably under the action of secondary back-bombing, enabling the magnetron 200 to continuously and stably output microwaves to heat food.

[0115] Please combine Figure 4 and Figure 5 The present invention provides a cathode assembly 300 for use in a magnetron 200. The cathode assembly 300 includes the cathode electron emitter 100 of any of the above embodiments.

[0116] In the aforementioned cathode assembly 300, the cathode electron emitter 100 is cylindrical, which can effectively improve the internal stress of the cathode electron emitter 100 and reduce the failure rate of the cathode electron emitter 100 to a certain extent.

[0117] Specifically, please combine Figure 5 The magnetron 200 includes a cathode assembly 300 and an anode assembly 20. The anode assembly 20 includes an anode cylinder 22 and multiple anode plates 24. One end of each anode plate 24 is connected to the side wall of a receiving cavity inside the anode cylinder 22 and is spaced apart along the circumferential direction of the anode cylinder 22. The other ends of the multiple anode plates 24 are suspended to form a receiving space. A cathode electron emitter 100 is disposed in the receiving space, and an interaction space 26 is formed between the cathode electron emitter 100 and the anode plates 24. 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 electron emitter 100 and the anode plates 24. At the same time, the upper magnet 28 and the lower magnet 30 of the magnetron 200 provide a magnetic field to the interaction space 26. The DC electric field and the DC magnetic field in the interaction space 26 are perpendicular to each other. The cathode electron emitter 100 emits electrons, which are accelerated by the electric field and deflected by the magnetic field, undergoing stable oscillating motion in the interaction space 26. 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 100 gains energy from the electric field in the interaction space 26. Under certain conditions, this energy is transferred to the high-frequency field and output as microwaves through the energy output window 32.

[0118] In some implementations, please refer to Figure 4 The cathode assembly 300 includes a support 12, which includes two end caps 18, and the two ends of the cathode electron emitter 100 are respectively disposed in the two end caps 18.

[0119] This facilitates the installation of the cathode electron emitter 100.

[0120] Specifically, the end cap 18 is provided with slots, and the two ends of the cathode electron emitter 100 can be placed in the slots of the two end caps 18, so that the cathode electron emitter 100 can be conveniently installed on the bracket 12.

[0121] In some implementations, please refer to Figure 4 The cathode assembly 300 includes a connecting rod 14 and a cathode connector 16, with two end caps 18 connected to the cathode connector 16 via the connecting rod 14.

[0122] This allows for the formation of an electrical connection path for the cathode assembly 300.

[0123] Specifically, the cathode connector 16 is connected to two end caps 18 via two connecting rods 14, allowing current to flow into and out of the cathode electron emitter 100 through the cathode connector 16, connecting rods 14, and end caps 18. The cathode connector 16 can be connected to a power source, which can be provided by the filament windings of a transformer. Figure 4As shown, when the power is turned on, the cathode connector 16 provides a current of about 10A to the cathode electron emitter 100 through the connecting rod 14. The cathode electron emitter 100 spontaneously emits electrons under strong thermal resistance, and then converts them into microwaves through a high voltage field and a high magnetic field.

[0124] Please combine Figure 5 The magnetron 200 provided in this embodiment includes the cathode assembly 300 of any of the above embodiments.

[0125] The present invention provides a microwave cooking appliance including the magnetron 200 of the above embodiment.

[0126] In the aforementioned magnetron 200 and microwave cooking appliance, the cathode electron emitter 100 is cylindrical, which can effectively improve the internal stress of the cathode electron emitter 100 and reduce the failure rate of the cathode electron emitter 100 to a certain extent.

[0127] 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.

[0128] In some embodiments, the cathode electron emitter 100 includes a core 34 and a carbide layer 36, the carbide layer 36 covering the core 34 at least in the circumferential direction, the core 34 being made of lanthanum-tungsten material, and the carbide layer 36 being a lanthanum-tungsten carbide layer, and the cathode electron emitter 100 is capable of emitting electrons with a minimum output power of 100 watts for a microwave cooking appliance.

[0129] Therefore, the cathode electron emitter 100 can be adapted to more application scenarios of microwave cooking appliances.

[0130] 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 electron emitter 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 needs.

[0131] Actual measurements show that when the cathode electron emitter 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.

[0132] In summary, the technical solution of this utility model, by introducing a cylindrical cathode electron emitter 100, increases the static pressure of the cathode electron emitter 100 by 121% and significantly reduces the failure rate of the cathode electron emitter 100. Moreover, the effective area of ​​the cathode electron emitter 100 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%.

[0133] Furthermore, the cathode electron emitter 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, 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 36 and the core 34, and the carbide layer 36 is distributed in layers. Its emission capability is improved by 92% compared to the original product. The carbide layer 36 of this embodiment can make its secondary back-bombing capability strong, enabling continuous emission of secondary electrons. Thus, after the cathode electron emitter 100 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 100 can also enable the magnetron 200 to output stable microwaves, allowing the microwave cooking appliance to heat the food.

[0134] 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 utility model. 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.

[0135] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

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

2. The cathode electron emitter according to claim 1, characterized in that, The inner diameter of the cathode electron emitter is 2.5 mm to 3.5 mm.

3. The cathode electron emitter according to claim 1, characterized in that, The outer diameter of the cathode electron emitter is 3.6 mm to 4.5 mm.

4. The cathode electron emitter according to claim 1, characterized in that, The height of the cathode electron emitter is 10 mm to 13 mm.

5. The cathode electron emitter according to claim 1, characterized in that, The cathode electron emitter is made of tungsten alloy.

6. The cathode electron emitter according to claim 1, 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.

7. The cathode electron emitter according to claim 6, 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.

8. The cathode electron emitter according to claim 6 or 7, characterized in that, The thickness of the carbonized layer is 8% of the sum of the thickness of the carbonized layer and the core.

9. The cathode electron emitter according to claim 6 or 7, 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.

10. The cathode electron emitter according to claim 6, characterized in that, The cathode electron emitter is also made of at least one of yttrium, rhenium, lutetium, zirconium, and hafnium.

11. The cathode electron emitter according to claim 6, characterized in that, The grain size of the core ranges from 0.4 μm to 2 μm.

12. The cathode electron emitter according to claim 6, 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.

13. A cathode assembly for a magnetron, characterized in that, The cathode assembly includes the cathode electron emitter as described in any one of claims 1-12.

14. The cathode assembly according to claim 13, characterized in that, The cathode assembly includes a support, the support includes two end caps, and the two ends of the cathode electron emitter are respectively disposed in the two end caps.

15. A magnetron, characterized in that, Includes the cathode assembly as described in claim 13 or 14.

16. A microwave cooking appliance, characterized in that, Including the magnetron of claim 15.

17. The microwave cooking appliance according to claim 16, 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 microwave cooking appliance has a minimum output power of 100 watts.

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