Cathode filament, cathode assembly, magnetron and microwave cooking appliance

Abstract

The application discloses a cathode filament, a cathode assembly, a magnetron and a microwave cooking appliance. The cathode filament comprises a filament core and a carbonized layer, the carbonized layer at least wraps the filament core in the circumferential direction of the filament core, the material of the filament core comprises lanthanum tungsten material, the carbonized layer comprises a lanthanum tungsten carbonized layer, and the working voltage of the cathode filament is 2.0-2.6 volts or the working current is 7-8.8 amperes. In the cathode filament, the material of the filament core comprises lanthanum tungsten material, and the carbonized layer comprises a lanthanum tungsten carbonized layer, so that the electron emission capacity of the cathode filament can be improved to a certain extent, the cathode filament can stably emit electrons at a lower working voltage (2.0-2.6 volts) or working current (7-8.8 amperes), the thermal load of the cathode filament is reduced, and the working temperature of the cathode filament is lowered.

Description

[0001] Priority information This application claims priority and benefits to patent application No. 202411750363.7, filed with the China National Intellectual Property Administration on November 29, 2024, the entire contents of which are incorporated herein by reference as if copied herein. Technical Field

[0002] This invention relates to the field of household appliance technology, and in particular to a cathode filament, cathode assembly, magnetron, and microwave cooking appliance. Background Technology

[0003] In related technologies, microwave ovens include magnetrons, which in turn include cathode filaments. Currently, the cathode filaments operate in extremely high-temperature environments, typically maintaining a temperature of around 1600-1800 degrees Celsius, during which microwaves are generated. However, this high-temperature condition causes the following problems: First, the high temperature causes other materials to release gases, leading to a decrease in vacuum; second, the high-temperature environment causes the cathode filament grains to gradually grow, eventually creating a risk of brittle fracture at the grain boundaries, significantly weakening the filament's shock resistance; third, directly lowering the cathode filament temperature results in insufficient electron emission, leading to a slow conversion to microwaves or even no microwave generation. Summary of the Invention

[0004] The present invention provides a cathode filament, a cathode assembly, a magnetron, and a microwave cooking appliance to solve at least one of the above-mentioned technical problems.

[0005] The present invention provides a cathode filament for a magnetron, the cathode filament comprising a filament core and a carbonized layer, the carbonized layer covering the filament core at least in the circumferential direction, the filament core being made of lanthanum-tungsten material, the carbonized layer comprising a lanthanum-tungsten carbonized layer, and the cathode filament having an operating voltage of 2.0 volts to 2.6 volts or an operating current of 7 amps to 8.8 amps.

[0006] In the aforementioned cathode filament, the filament core material includes lanthanum-tungsten material, and the carbide layer includes lanthanum-tungsten carbide layer, which can improve the electron emission capability of the cathode filament to a certain extent, enabling the cathode filament to emit electrons stably at a lower operating voltage (2.0 volts to 2.6 volts) or operating current (7 amps to 8.8 amps), thereby reducing the thermal load of the cathode filament and thus reducing the operating temperature of the cathode filament.

[0007] In some embodiments, the cathode filament operates at a voltage of 2.3 volts or an operating current of 7.6 to 7.8 amps.

[0008] In some embodiments, the oscillation time of the cathode filament is 4 to 4.7 seconds.

[0009] In some embodiments, the operating temperature of the cathode filament is 1300 to 1400 degrees Celsius.

[0010] In some embodiments, the cathode filament is helical or cylindrical.

[0011] In some embodiments, the thickness of the carbonized layer is 6% to 10% of the thickness of the cathode filament.

[0012] In some embodiments, the thickness of the carbonized layer is 8% of the thickness of the cathode filament.

[0013] In some embodiments, when the cathode filament has a helical structure, the thickness of the carbonized layer is 42 μm, and the thickness of the cathode filament is 0.5 mm; or, When the cathode filament is cylindrical, the thickness of the carbonized layer is 35 to 45 μm, and the thickness of the cathode filament is 0.4 mm.

[0014] In some embodiments, the cathode filament material further includes at least one of yttrium, rhenium, lutetium, zirconium, and hafnium.

[0015] In some embodiments, the grain size of the filament core ranges from 0.4 μm to 2 μm.

[0016] In some embodiments, the cathode filament is capable of emitting electrons after being powered on and after being powered off.

[0017] An embodiment of the present invention provides a cathode assembly for a magnetron, the cathode assembly comprising the cathode filament of any of the above embodiments.

[0018] The magnetron provided by the embodiments of the present invention includes the cathode assembly of any of the above embodiments.

[0019] The present invention provides a microwave cooking appliance including the magnetron described in the above embodiments.

[0020] In some embodiments, the cathode filament is capable of emitting electrons when the microwave cooking appliance has an output power of 100 watts.

[0021] 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 can improve the electron emission capability of the cathode filament to a certain extent, enabling the cathode filament to emit electrons stably at a lower operating voltage (2.0 volts to 2.6 volts) or operating current (7 amps to 8.8 amps), thereby reducing the heat load of the cathode filament and thus lowering the operating temperature.

[0022] Additional aspects and advantages of the 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

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the cathode filament according to an embodiment of the present invention; Figure 1a This is another structural schematic diagram of the cathode filament according to an embodiment of the present invention; Figure 2 This is a schematic cross-sectional view of the cathode filament of an embodiment of the present invention; Figure 2a This is a cross-sectional schematic diagram of the cathode filament according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the cathode assembly according to an embodiment of the present invention; Figure 4 This is a cross-sectional schematic diagram of the magnetron according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the operation of the magnetron electrons according to an embodiment of the present invention; Figure 6 This is a graph showing the relationship between the working voltage and the start-up time of the cathode filament in an embodiment of the present invention. Figure 7 A comparison chart showing the operating temperatures of cathode filaments in related technologies at an operating voltage of 3.3 volts and those of the cathode filaments in this invention at an operating voltage of 2.3 volts. Figure 8 This is a metallographic cross-sectional schematic diagram of the cathode filament according to an embodiment of the present invention; Figure 8a This is a partial schematic diagram of the metallographic cross-section of the cathode filament according to an embodiment of the present invention. Figure 8b This is a schematic diagram of the grain size distribution of the filament core of the cathode filament according to an embodiment of the present invention; Figure 8c This is a schematic diagram of the grain morphology distribution of the filament core of the cathode filament according to an embodiment of the present invention. Figure 9 This is a graph showing the relationship between the thickness of the carbonized layer and the static pressure of the cathode filament in an embodiment of the present invention. Figure 10This is a comparison diagram of the electron emission capabilities of the cathode filament in the embodiment of the present invention and the cathode filament in related technologies; Figure 11 This is a schematic diagram of the metal band structure in related technologies; Figure 12 This is a metallographic cross-sectional schematic diagram of the cathode filament of a related technology; Figure 12a This is a partial schematic diagram of the metallographic cross-section of a cathode filament in a related technology. Figure 12b This is a schematic diagram of the grain size distribution in the filament core of a cathode filament in a related technology. Figure 12c This is a schematic diagram of the grain morphology distribution in the filament core of a cathode filament in a related technology.

[0025] Explanation of key component reference numerals: 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. Detailed Implementation

[0026] Embodiments of the present invention are described in detail below, examples of which 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 the present invention, and should not be construed as limiting the present invention.

[0027] In the description of this invention, 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 orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention 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 the invention. 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 invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0028] In the description of this invention, 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. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0029] 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.

[0030] The following disclosure provides many different embodiments or examples for implementing various structures of the 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 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.

[0031] Please refer to Figures 1 to 4 This invention provides a cathode filament 100 for use in a magnetron 200. The cathode filament 100 includes a filament core 14 and a carbide layer 16. The carbide layer 16 covers the filament core 14 at least in the circumferential direction. The filament core 14 is made of lanthanum-tungsten, and the carbide layer 16 is a lanthanum-tungsten carbide layer. The cathode filament 100 operates at a voltage of 2.0 volts to 2.6 volts, or at a current of 7 amps to 8.8 amps.

[0032] 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 can improve the electron emission capability of the cathode filament 100 to a certain extent, enabling the cathode filament 100 to emit electrons stably at a lower operating voltage (2.0 volts to 2.6 volts) or operating current (7 amps to 8.8 amps), thereby reducing the heat load of the cathode filament 100 and thus reducing the operating temperature of the cathode filament 100.

[0033] Specifically, the cathode filament 100 can be used in the magnetron 200. Please refer to... Figure 1 , Figure 3 and Figure 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 disposed within the two end caps 26, and the cathode connector 24 is connected to the two end caps 26 respectively via the two connecting rods 20. The cathode connector 24 can be connected to a power source, which can be provided by the filament windings of a transformer. Figure 3 As shown, when the power is turned on at the cathode connector 24, current is supplied to the cathode filament 100 through the connecting rod 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, the end cap 26 is provided with slots, 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.

[0034] In related technologies, microwave ovens include magnetrons, which in turn include cathode filaments. Currently, to ensure sufficient electron emission to meet the normal operating requirements of the magnetron, existing cathode filaments typically operate under high voltage and current conditions, placing them in an extreme high-temperature environment for extended periods. Their operating temperature is usually maintained at around 1600-1800 degrees Celsius, generating microwaves in the process. However, this high-temperature condition causes the following problems: First, the high temperature causes other materials to release gases, leading to a decrease in vacuum. Second, the high-temperature environment causes the cathode filament grains to gradually grow, eventually creating a risk of brittle fracture at the grain boundaries, significantly weakening the filament's shock resistance. Third, directly lowering the cathode filament temperature results in insufficient electron emission, leading to a slow conversion to microwaves or even no microwave generation.

[0035] In this embodiment of the invention, the filament core 14 is made of lanthanum-tungsten material, and the carbide layer 16 is a lanthanum-tungsten carbide layer. For example... Figure 11As 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 to replace the original thorium, resulting in a lower work function of the cathode filament 100 than that of the original thorium-tungsten filament. Furthermore, the lanthanum-tungsten material 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 lanthanum-tungsten material 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. This allows the cathode filament 100 to stably emit electrons at lower operating voltages (2.0 V to 2.6 V) or lower operating currents (7 A to 8.8 A). Furthermore, orthogonal designs can be performed for multiple experimental parameters of the carbonization reaction, ultimately yielding results such as... Figure 8 and Figure 8a The results of carbonized layer 16 are shown.

[0036] It is understandable that the cathode filament 100 can spontaneously emit electrons under strong thermal resistance, which are then converted into microwaves via a high-voltage field and a high-magnetic field. The temperature of the cathode filament 100 mainly originates from the resistance heating of the cathode filament 100. This invention improves the electron emission capability of the cathode filament 100, enabling it to achieve stable and effective electron emission even at lower operating voltages or currents. In other words, it achieves spontaneous release of thermionic electrons under lower thermal resistance conditions, thereby reducing the operating temperature of the cathode filament 100 and extending its service life. For comparison, the operating voltage of a thorium-tungsten filament is 3.3V, or the operating current is 10A.

[0037] Please combine Figure 6 , Figure 6 This is a graph showing the relationship between the operating voltage of the cathode filament and the oscillation start-up time. The oscillation start-up time refers to the time required from the moment the cathode filament 100 is energized and heated until the magnetron 200 begins to generate microwaves. From... Figure 6 As can be seen, the higher the operating voltage of the cathode filament 100, the shorter the oscillation time, indicating that a higher voltage helps to accelerate the heating rate of the cathode filament 100, thus enabling it to enter the emission state more quickly. However, as the operating voltage increases, the operating temperature of the cathode filament 100 also increases accordingly.

[0038] In this embodiment of the invention, the operating voltage of the cathode filament 100 is controlled between 2.0 volts and 2.6 volts. On the one hand, this can avoid the oscillation time being too long and the operating temperature of the cathode filament 100 being too high. On the other hand, by improving the electron emission efficiency of the cathode filament 100, the electron emission of the cathode filament 100 remains stable and reliable at a lower voltage (2.0 volts to 2.6 volts).

[0039] In some examples, the operating voltage of the cathode filament 100 is U1. U1 = 2.0 V, 2.05 V, 2.1 V, 2.15 V, 2.2 V, 2.25 V, 2.3 V, 2.35 V, 2.4 V, 2.45 V, 2.5 V, 2.55 V, 2.6 V, or any other value between 2.0 V and 2.6 V.

[0040] In some examples, the operating current is I1. I1 = 7 A, 7.2 A, 7.4 A, 7.6 A, 7.8 A, 8.0 A, 8.2 A, 8.4 A, 8.6 A, 8.8 A, or other values ​​between 8 A and 8.8 A.

[0041] Please combine Figure 7 , Figure 7 This is a comparison chart showing the operating temperatures of a thorium-tungsten filament in related technologies at an operating voltage of 3.3 volts and the cathode filament 100 of this invention at an operating voltage of 2.3 volts. From... Figure 7 It can be seen that the operating temperature of the thorium-tungsten filament is around 1650 degrees Celsius when the operating voltage is 3.3 volts, and the operating temperature of the cathode filament 100 is around 1300 degrees Celsius when the operating voltage is 2.3 volts.

[0042] It should be noted that the operating voltage and operating current of the cathode filament 100 are usually closely related, and can be considered as equivalent control parameters under a certain load. Therefore, the descriptions of "operating voltage" or "operating current" in the embodiments of this invention can be understood interchangeably.

[0043] exist Figure 1 and Figure 2 In the illustrated embodiment, the cathode filament 100 has a spiral structure. The filament core 14 has two main functions: first, to stabilize the spiral structure of the cathode filament 100; and second, to form 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, thereby ensuring the continuous electron emission capability of the cathode filament 100.

[0044] The carbide layer 16 covers the filament core 14 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 14 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 14 in both the circumferential and longitudinal directions.

[0045] Please combine Figure 12 and Figure 12a , Figure 12 This is a cross-sectional view of a thorium-tungsten filament in a related technology. Figure 12a This is a partially enlarged cross-sectional view of a thorium-tungsten filament from a related technology. From Figure 12 and Figure 12a It can be seen that in the relevant technologies, the filament core is blocky with coarse grains and weak bonding, and the carbide layer is mostly blocky tungsten carbide.

[0046] Please combine Figure 8 and Figure 8a , Figure 8 This is a cross-sectional view of the cathode filament 100 comprising lanthanum-tungsten material according to an embodiment of the present invention. Figure 8a This is a partially enlarged cross-sectional view of the cathode filament 100 comprising lanthanum-tungsten material according to an embodiment of the present invention. Figure 8 and Figure 8a As can be seen, in this embodiment of the invention, the internal structure of the filament core 14 is compact and has strong resistance to breakage. In the carbide layer 16, fine layered tungsten carbide is predominant, which increases the electron emission channel and enhances the electron emission capability of the cathode filament 100.

[0047] Based on actual testing, please combine... Figure 10 When tested without a magnetic field, the original filament in the related technology receives a total electron current of 360mA from the cathode filament at a current of 9A, while the cathode filament 100 (lanthanum tungsten filament) has an electron current of 692mA at a current of 9A.

[0048] 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 invention does not impose specific limitations on this.

[0049] In some embodiments, the cathode filament 100 operates at a voltage of 2.3 volts or an operating current of 7.6 to 7.8 amps.

[0050] Therefore, the operating voltage or operating current of the cathode filament 100 can be further prioritized.

[0051] Specifically, the oscillation time of the cathode filament 100 is positively correlated with the operating voltage of the cathode filament 100. An increase in the operating voltage of the cathode filament 100 will increase the operating temperature of the cathode filament 100. Therefore, in order to balance the oscillation time and operating temperature of the cathode filament 100, the operating voltage of the cathode filament 100 is 2.3 volts, or the operating current is 7.6 to 7.8 amps.

[0052] In some examples, U1 = 2.3 volts. I1 = 7.6 amps, 7.62 amps, 7.64 amps, 7.66 amps, 7.68 amps, 7.7 amps, 7.72 amps, 7.74 amps, 7.76 amps, 7.78 amps, 7.8 amps, or other values ​​between 7.6 amps and 7.8 amps.

[0053] In some embodiments, the oscillation time of the cathode filament 100 is 4 to 4.7 seconds.

[0054] This can improve the lifespan of the cathode filament and enhance the response speed of microwave cooking appliances.

[0055] Specifically, the cathode filament 100 includes a filament core 14 and a carbide layer 16. The filament core 14 is made of lanthanum-tungsten material, and the carbide layer 16 is a lanthanum-tungsten carbide layer, which reduces the electron work function of the cathode filament 100 and improves the electron emission capability of the cathode filament 100, thereby shortening the start-up time required for the cathode filament 100 to generate microwaves from heating.

[0056] In this embodiment of the invention, the operating voltage of the cathode filament 100 is 2.0 volts to 2.6 volts, or the operating current is 7 amps to 8.8 amps, and the oscillation time can reach 4 seconds to 4.7 seconds, thereby reducing the operating temperature of the cathode filament 100 and enabling rapid oscillation.

[0057] In one implementation, from Figure 6 As can be seen from this, when the working voltage of the cathode filament 100 is 2.0 volts to 2.6 volts, the corresponding oscillation time is 4 seconds to 4.7 seconds.

[0058] In some examples, when the operating voltage of the cathode filament 100 is 2.0 volts to 2.6 volts, the oscillation time is t, where t = 4 seconds, 4.1 seconds, 4.2 seconds, 4.3 seconds, 4.4 seconds, 4.6 seconds, 4.7 seconds, or other values ​​between 4 seconds and 4.7 seconds.

[0059] In some embodiments, the operating temperature of the cathode filament 100 is 1300 to 1400 degrees Celsius.

[0060] This reduces energy consumption and increases the lifespan of the cathode filament 100.

[0061] Specifically, the cathode filament 100 mainly raises its temperature through resistance heating during operation, thereby achieving the thermionic emission function. According to Ohm's law and the Joule heating effect, the temperature of the cathode filament 100 is related to the input voltage, current, and its own resistance.

[0062] In thorium-tungsten filament solutions of related technologies, the operating temperature of the thorium-tungsten filament typically needs to be maintained between 1600°C and 1800°C to obtain sufficient electron emission current density. However, the high-temperature environment not only increases energy consumption but also accelerates problems such as grain coarsening, material volatilization, and structural aging of the thorium-tungsten filament, resulting in shortened service life, reduced vacuum level, and deteriorated vibration resistance.

[0063] In this embodiment of the invention, the cathode filament 100 includes a filament core 14 and a carbide layer 16. The filament core 14 is made of lanthanum-tungsten, and the carbide layer 16 is a lanthanum-tungsten carbide layer, which has a low work function and higher emission efficiency. Under the same voltage, the cathode filament 100 can emit electrons earlier and more efficiently. Therefore, to meet the microwave requirements of microwave cooking appliances, the operating temperature of the cathode filament 100 can be reduced to 1300°C to 1400°C by lowering the operating voltage or current of the cathode filament 100.

[0064] In some examples, the operating temperature of the cathode filament 100 is T, where T = 1300℃, 1310℃, 1320℃, 1330℃, 1340℃, 1350℃, 1360℃, 1370℃, 1380℃, 1390℃, 1400℃, or other values ​​between 1300℃ and 1400℃.

[0065] In some embodiments, the cathode filament 100 has a spiral structure or is cylindrical.

[0066] Therefore, the shape of the cathode filament 100 can be selected according to different application scenarios.

[0067] Specifically, in one embodiment, the cathode filament 100 has a helical structure; specifically, in... Figure 1 In the embodiment shown, the cathode filament 100 has a cylindrical helical structure. During manufacturing, the cathode filament 100 with a cylindrical helical structure can be formed by winding the wire 12, which is simple and has controllable precision.

[0068] In one implementation, please refer to Figure 1a and Figure 2a The cathode filament 100 is cylindrical. Because the cylindrical shape provides a larger stress-bearing surface, it improves the breakage resistance of the cathode filament 100. Furthermore, the cylindrical shape provides a larger and more continuous effective emission surface, thereby improving the uniformity of the electron flux density.

[0069] In some embodiments, the thickness of the carbonized layer 16 is 6% to 10% of the thickness of the cathode filament 100.

[0070] Therefore, the long-term electron emission capability of the cathode filament 100 can be guaranteed to a certain extent.

[0071] Specifically, please combine Figure 2 In one embodiment, the cathode filament 100 has a helical structure and is formed by winding wire 12. The thickness of the cathode filament 100 can be the thickness of the wire 12. The thickness of the carbonized layer 16 is D1, and the thickness of the wire 12 is D2. The thickness of the carbonized layer 16 is 6% to 10% of the thickness of the wire 12, that is, 6% × D2 ≤ D1 ≤ 10% × D2. Figure 2 In the process, the filament 12 is cylindrical, the thickness D2 of the filament 12 is the diameter of the filament 12, and 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.

[0072] 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.

[0073] Please combine Figure 1a and Figure 2a In one embodiment, the cathode filament 100 is cylindrical, and its thickness is equal to its diameter. The thickness of the carbonized layer 16 is D3, and the thickness of the cathode filament 100 is D4. The thickness of the carbonized layer 16 is 6% to 10% of the thickness of the cathode filament 100, that is, 6% × D4 ≤ D3 ≤ 10% × D4. The thickness D3 of the carbonized layer 16 is the difference between the diameter of the cathode filament 100 and the diameter of the filament core 14.

[0074] In some examples, D3 = 6%×D4, 6.5%×D4, 7%×D4, 7.5%×D4, 8%×D4, 8.5%×D4, 9%×D4, 9.5%×D4, 10%×D4, or other values ​​between 6%×D4 and 10%×D4.

[0075] The thickness of the carbide layer 16 is 6% to 10% of the thickness of the cathode filament. The thickness ratio of the carbide layer 16 is moderate. During the long-term use of the cathode filament 100, it can ensure that the filament core 14 can continuously provide lanthanum to the carbide layer 16 to a certain extent, so that the carbide layer 16 has a long-term stable electron emission capability.

[0076] Verification has shown that the thickness of the carbide layer including the lanthanum-tungsten carbide layer in the embodiments of the present invention is 6% to 10% of the thickness of the cathode filament, which is 16% thicker than the carbide layer in related technologies. Moreover, the carbide layer 16 in the embodiments 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 filament.

[0077] In some embodiments, the thickness of the carbonized layer 16 is 8% of the thickness of the cathode filament 100.

[0078] Therefore, the thickness of the carbonized layer 16 can be further prioritized.

[0079] 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 cathode filament 100. In one embodiment, the cathode filament 100 has a helical structure and is formed by winding the wire 12. The thickness of the cathode filament 100 can be the thickness of the wire 12.

[0080] Please combine Figure 9 , Figure 9 This is a curve showing the relationship between the thickness of the carbonized layer 16 and the static pressure of the cathode filament 100. The static pressure of the cathode filament 100 refers to the maximum pressure that the cathode filament 100 can withstand under external mechanical loads in a non-energized state. Static pressure reflects the structural strength or compressive strength of the cathode filament 100. From... Figure 9 It can be seen that as the thickness of the carbonized layer 16 increases, the static pressure of the cathode filament 100 decreases, indicating that the brittleness of the cathode filament 100 increases and its mechanical strength decreases. In this embodiment of the invention, the thickness of the carbonized layer 16 is 8% of the thickness of the cathode filament. This helps the cathode filament 100 to have good electron emission performance and also allows the cathode filament 100 to meet the impact and vibration resistance requirements of the magnetron 200 during transportation and operation.

[0081] In some embodiments, when the cathode filament 100 has a spiral structure, the thickness D1 of the carbonized layer 16 is 42 μm (micrometers), and the thickness D2 of the cathode filament 100 is 0.5 mm (millimeters).

[0082] This is beneficial for increasing the electron emission capability of the cathode filament 100.

[0083] Specifically, when the cathode filament 100 has a spiral structure, the thickness of the carbonized layer 16 is D1=42μm, and the thickness of the cathode filament 100 is equal to the thickness of the wire 12, D2=0.5mm.

[0084] When the cathode filament 100 is cylindrical, the thickness of the carbonized layer 16 is D3 = 35 μm to 45 μm, and the thickness of the cathode filament 100 is D4 = 0.5 mm.

[0085] As a comparative example, the thickness of the thorium tungsten carbide layer is about 35 μm. In the cathode filament of the present invention, the carbide layer 16 is mostly in the form of layered channels. The increased crystal gap area compared to the comparative example is more conducive to increasing the electron emission capability of the cathode filament 100.

[0086] In some examples, the thickness of the carbide layer 16 is D3, where D3 = 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, or other values ​​between 35 μm and 45 μm.

[0087] In some embodiments, the cathode filament 100 is made of at least one of yttrium, rhenium, lutetium, zirconium, and hafnium.

[0088] This can improve the electron emission capability, melting point, and / or saturated vapor pressure of the cathode filament 100.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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 invention does not impose specific limitations on these proportions.

[0093] 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.

[0094] In some embodiments, the grain size of the filament core 14 ranges from 0.4 μm to 2 μm.

[0095] This is beneficial for increasing the electron emission capability of the cathode filament 100.

[0096] 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. Please refer to... Figure 8b and Figure 8c The average grain size of the lanthanum-tungsten alloy in the embodiments of the present invention is compared with that in the comparative example (e.g.) Figure 12b and Figure 12c The thorium-tungsten grains are small and uniformly distributed, which helps to increase the electron emission capability of the cathode filament 100.

[0097] 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.

[0098] In some embodiments, the cathode filament 100 is capable of emitting electrons after being powered on and after being powered off.

[0099] Therefore, even after a power outage, the cathode filament 100 maintains a strong and stable operating performance.

[0100] Specifically, the carbonized layer 16 of the cathode filament 100 in this embodiment of the invention has a strong secondary back-bombardment capability. During the operation of the magnetron 200, after the cathode filament 100 is energized and emits electrons (i.e., after providing a working voltage of 2.0V to 2.6V or a working current of 7A to 8.8A), the cathode filament 100 can be de-energized after oscillation. Even after de-energization, 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-bombardment electron can cause the emission of two new electrons, and two back-bombardment electrons can cause the emission of four new electrons, etc. Therefore, after the cathode filament 100 emits electrons when energized, even if the power is cut off (equivalent to 0 amp current), the carbonized layer 16 can continue to emit electrons stably under the action of secondary back bombardment, so that the magnetron 200 can continuously and stably output microwaves to heat the food.

[0101] In some embodiments, the length L of the cathode filament 100 is 12 ± 0.5 mm.

[0102] Therefore, the length of the cathode filament 100 is adapted to the spatial structure of the magnetron 200.

[0103] 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.

[0104] In one embodiment, when manufacturing the helical cathode filament 100, the filament 12 can be wound to form a cylindrical helical structure. In one example, the diameter of the filament 12 of the cathode filament 100 is 0.5 mm.

[0105] 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.

[0106] In one embodiment, a DC emission test showed that the DC electron emission capability of the cathode filament 100 of the present invention was improved by 92% compared with the original product. In addition, after the adjustment of the carbonization layer 16, the cathode filament 100 has a strong secondary back-bombing capability (using electron collision energy to generate new electrons), which means that after the cathode filament 100 emits electrons after heating, it can maintain stable microwave operation under power failure (0A current). Moreover, it was tested that when the microwave output power is 100 watts, the microwave cooking appliance can operate stably to heat the food.

[0107] An embodiment of the present invention provides a cathode assembly 300 for a magnetron 200, the cathode assembly 300 including the cathode filament 100 of any of the above embodiments.

[0108] 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 can improve the electron emission capability of the cathode filament 100 to a certain extent, enabling the cathode filament 100 to emit electrons stably at a lower operating voltage (2.0 volts to 2.6 volts) or operating current (7 amps to 8.8 amps), thereby reducing the heat load of the cathode filament 100 and thus reducing the operating temperature of the cathode filament 100.

[0109] Specifically, please combine Figure 4The magnetron 200 includes an anode assembly 400, which includes an anode cylinder 28 and a plurality of anode plates 30. One end of each anode plate 30 is connected to the side wall of a receiving cavity within the anode cylinder 28 and is spaced apart along the circumferential direction of the anode cylinder 28. The other ends of the anode plates 30 are suspended to form a receiving space, in which a cathode filament 100 is disposed. An interaction space 32 is formed between the cathode filament 100 and the anode plates 30. Please refer to... Figure 4 and Figure 5 The working principle of the magnetron 200 is as follows: When the magnetron 200 is working, a DC voltage is applied between the cathode filament 100 and the anode plate 30. Simultaneously, the upper magnet 34 and lower magnet 36 of the magnetron 200 provide a magnetic field to the interaction space 32. The DC electric field and DC magnetic field within the interaction space 32 are perpendicular to each other. Electrons emitted from the cathode filament 100 are accelerated by the electric field and deflected by the magnetic field, resulting in stable oscillating motion within 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 from the electric field in the interaction space 32 by the electron stream emitted from the cathode filament 100 is transferred to a high-frequency field under certain conditions and output as microwaves through the energy output window 38.

[0110] 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.

[0111] This facilitates the installation of the cathode filament 100.

[0112] 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.

[0113] Please combine Figure 4 The magnetron 200 provided in this embodiment includes the cathode assembly 300 of any of the above embodiments.

[0114] The present invention provides a microwave cooking appliance including the magnetron 200 of the above embodiment.

[0115] In the aforementioned magnetron and microwave cooking appliance, the filament core 14 is made of lanthanum tungsten and the carbide layer is a lanthanum tungsten carbide layer, which can improve the electron emission capability of the cathode filament 100 to a certain extent, so that the cathode filament 100 can stably emit electrons at a lower operating voltage (2.0 volts to 2.6 volts) or operating current (7 amps to 8.8 amps), thereby reducing the heat load of the cathode filament 100 and thus reducing the operating temperature of the cathode filament 100.

[0116] 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.

[0117] In some implementations, the cathode filament 100 is capable of emitting electrons when the microwave cooking appliance has an output power of 100 watts.

[0118] Therefore, the cathode filament 100 can be adapted to more application scenarios of microwave cooking appliances.

[0119] Specifically, microwave cooking appliances with magnetrons 200 are used in scenarios requiring low power, such as microwave heating or boiling milk. In one embodiment, the output power of the microwave cooking appliance is 100 watts. The cathode filament 100 of this embodiment can emit electrons even when the 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. Optionally, the output power of 100 watts is the minimum output power of the microwave cooking appliance.

[0120] Actual testing showed that when the cathode filament 100 outputs 100 watts in a microwave cooking appliance, the appliance can operate stably and heat food.

[0121] In summary, the cathode filament 100 of this invention 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 cathode filament 100, and the carbide layer 16 is distributed in a layered manner. The emission capability is improved by 92% compared to the original product. The carbide layer 16 of this invention enables strong secondary back-bombardment capability, allowing continuous emission of secondary electrons. Thus, after the cathode filament 100 emits electrons through heating, it can still operate stably under power failure (0A current). Even with a minimum output power of 100 watts for microwave cooking appliances, the cathode filament 100 can enable the magnetron 200 to output stable microwaves, allowing the microwave cooking appliance to heat the food.

[0122] 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., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of the invention. 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.

[0123] Although embodiments of the 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 invention, 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 includes a filament core and a carbonized layer. The carbonized layer covers the filament core at least in the circumferential direction. The filament core is made of lanthanum-tungsten material, and the carbonized layer is a lanthanum-tungsten carbonized layer. The operating voltage of the cathode filament is 2.0 volts to 2.6 volts, or the operating current is 7 amps to 8.8 amps.

2. The cathode filament according to claim 1, characterized in that, The cathode filament operates at a voltage of 2.3 volts or a current of 7.6 to 7.8 amps.

3. The cathode filament according to claim 1, characterized in that, The starting time of the cathode filament is 4 to 4.7 seconds.

4. The cathode filament according to claim 1, characterized in that, The operating temperature of the cathode filament is 1300 to 1400 degrees Celsius.

5. The cathode filament according to claim 1, characterized in that, The cathode filament has a spiral structure or is cylindrical.

6. 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 cathode filament.

7. The cathode filament according to claim 1 or 6, characterized in that, The thickness of the carbonized layer is 8% of the thickness of the cathode filament.

8. The cathode filament according to claim 1 or 6, characterized in that, When the cathode filament has a spiral structure, the thickness of the carbonized layer is 42 μm and the thickness of the cathode filament is 0.5 mm; or, when the cathode filament is cylindrical, the thickness of the carbonized layer is 35 to 45 μm and the thickness of the cathode filament is 0.4 mm.

9. The cathode filament according to claim 1, characterized in that, The cathode filament material also includes at least one of yttrium, rhenium, lutetium, zirconium, and hafnium.

10. The cathode filament according to claim 1, characterized in that, The grain size of the filament core ranges from 0.4 μm to 2 μm.

11. The cathode filament according to claim 1, 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.

12. A cathode assembly for a magnetron, characterized in that, The cathode assembly includes the cathode filament as described in any one of claims 1-11.

13. A magnetron, characterized in that, Includes the cathode assembly as described in claim 12.

14. A microwave cooking appliance, characterized in that, Including the magnetron of claim 13.

15. The microwave cooking appliance according to claim 14, characterized in that, The cathode filament is capable of emitting electrons when the microwave cooking appliance has an output power of 100 watts.

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