Control method of microwave cooking appliance, microwave cooking appliance, and storage medium

Abstract

The application discloses a microwave cooking utensil control method, a microwave cooking utensil and a storage medium. The microwave cooking utensil comprises a magnetron, the magnetron comprises a cathode filament, the cathode filament comprises a filament core and a carbonized layer, the carbonized layer at least wraps the filament core in a circumferential direction of the filament core, a material of the filament core comprises lanthanum tungsten material, and the carbonized layer comprises a lanthanum tungsten carbonized layer. The control method comprises the following steps: energizing the magnetron to start the magnetron; and after the magnetron is started, reducing the working power of the cathode filament. In the microwave cooking utensil, the working temperature of the cathode filament can be reduced to a certain extent, and the working life of the cathode filament is prolonged.

Description

Technical Field

[0001] This invention relates to the field of household appliance technology, and in particular to a control method for a microwave cooking appliance, the microwave cooking appliance, and a storage medium. Background Technology

[0002] In related technologies, microwave ovens include a magnetron, which includes a cathode assembly, which includes a cathode filament. Currently, the cathode filament operates in an extremely high-temperature environment, typically maintaining an operating temperature of around 1600-1800 degrees Celsius, during which microwaves are generated. However, this high-temperature condition affects the lifespan of the cathode filament. Summary of the Invention

[0003] The present invention provides a control method for a microwave cooking appliance, a microwave cooking appliance, and a computer-readable storage medium to solve at least one of the aforementioned technical problems.

[0004] This invention provides a control method for a microwave cooking appliance. The microwave cooking appliance includes a magnetron, the magnetron includes a cathode filament, 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;

[0005] The control method includes:

[0006] Powering the magnetron causes it to oscillate.

[0007] After the magnetron has started oscillating, reduce the operating power of the cathode filament.

[0008] In the aforementioned control method for microwave cooking appliances, the filament core material includes lanthanum-tungsten, and the carbide layer includes a lanthanum-tungsten carbide layer. After the magnetron starts oscillating, some electrons emitted by the cathode filament can bombard the carbide layer, causing it to generate secondary electrons to maintain microwave generation. Therefore, even when the operating power of the cathode filament is reduced after the magnetron starts oscillating, the magnetron can still generate continuous microwaves, maintaining its operation. This can, to some extent, reduce the operating temperature of the cathode filament and extend its lifespan.

[0009] In some embodiments, energizing the magnetron to cause it to oscillate includes:

[0010] The magnetron is energized for a preset duration to cause it to oscillate.

[0011] After the magnetron has started oscillating, reducing the operating power of the cathode filament includes:

[0012] After the preset time, the operating power of the cathode filament is reduced.

[0013] In some implementations, the preset duration is negatively correlated with the operating voltage and / or operating current of the cathode filament.

[0014] In some embodiments, the cathode filament operates at a voltage of 2.0 volts to 4.3 volts, or at a current of 7.8 amps to 11 amps.

[0015] In some embodiments, reducing the operating power of the cathode filament after the magnetron has started oscillating includes:

[0016] Reduce the operating power of the cathode filament to zero power.

[0017] In some embodiments, the control method includes:

[0018] During the start-up process of the magnetron, the microwave output power of the microwave cooking appliance is monitored;

[0019] When the microwave output power of the microwave cooking appliance is greater than or equal to the set power, it is determined that the magnetron has completed oscillation.

[0020] The present invention provides a microwave cooking appliance including a controller and a magnetron. The magnetron includes a cathode filament, 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 material of the filament core includes lanthanum tungsten material, and the carbonized layer includes a lanthanum tungsten carbonized layer.

[0021] The controller includes a processor and a memory, the memory storing a computer program that, when executed by the processor, implements the steps of the control method for a microwave cooking appliance according to any of the above embodiments.

[0022] In some embodiments, the cathode filament is helical or cylindrical.

[0023] In some embodiments, the thickness of the carbonized layer is 6% to 10% of the thickness of the cathode filament.

[0024] In some embodiments, the thickness of the carbonized layer is 8% of the thickness of the cathode filament.

[0025] 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,

[0026] When the cathode filament is cylindrical, the thickness of the carbonized layer is 35 μm to 45 μm, and the thickness of the cathode filament is 0.4 mm.

[0027] In some embodiments, the cathode filament material further includes at least one of yttrium, rhenium, lutetium, zirconium, and hafnium.

[0028] In some embodiments, the grain size of the filament core ranges from 0.4 μm to 2 μm.

[0029] In some embodiments, the length of the cathode filament is 12 ± 0.5 mm.

[0030] This invention provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the control method for a microwave cooking appliance according to any of the above embodiments.

[0031] In the aforementioned control method for microwave cooking appliances, microwave cooking appliances, and computer-readable storage media, the filament core material includes lanthanum-tungsten, and the carbide layer includes a lanthanum-tungsten carbide layer. After the magnetron starts oscillating, some electrons emitted by the cathode filament can bombard the carbide layer, causing it to generate secondary electrons to maintain microwave generation. Therefore, even when the operating power of the cathode filament is reduced after the magnetron starts oscillating, the magnetron can still generate continuous microwaves, maintaining its operation. This can, to some extent, reduce the operating temperature of the cathode filament and extend its lifespan.

[0032] 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

[0033] 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.

[0034] Figure 1 This is a schematic diagram of the cathode filament according to an embodiment of the present invention;

[0035] Figure 1a This is another structural schematic diagram of the cathode filament according to an embodiment of the present invention;

[0036] Figure 2 This is a schematic cross-sectional view of the cathode filament of an embodiment of the present invention;

[0037] Figure 2a This is a cross-sectional schematic diagram of the cathode filament according to an embodiment of the present invention;

[0038] Figure 3 and Figure 4 This is a flowchart illustrating the control method according to an embodiment of the present invention;

[0039] Figure 5 This is a schematic diagram of the structure of the cathode assembly according to an embodiment of the present invention;

[0040] Figure 6 This is a cross-sectional schematic diagram of the magnetron according to an embodiment of the present invention;

[0041] Figure 7 This is a schematic diagram of the operation of the magnetron electrons according to an embodiment of the present invention;

[0042] Figure 8 This is a circuit diagram of the frequency converter according to an embodiment of the present invention;

[0043] Figure 9 This is a comparison diagram of the electron back-bombardment capability of the cathode filament in the embodiment of the present invention and the cathode filament in related technologies;

[0044] Figure 10 This is a comparison diagram of the thermionic emission model of the cathode filament in the embodiment of the present invention and the cathode filament in related technologies;

[0045] Figure 11 This is a metallographic cross-sectional schematic diagram of the cathode filament according to an embodiment of the present invention;

[0046] Figure 11a This is a partial schematic diagram of the metallographic cross-section of the cathode filament according to an embodiment of the present invention.

[0047] Figure 11b 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;

[0048] Figure 11c 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.

[0049] Figure 12 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.

[0050] Figure 13 This 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;

[0051] Figure 14 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.

[0052] Figure 15 This is a schematic diagram of the modules of a microwave cooking appliance according to an embodiment of the present invention;

[0053] Figure 16 This is a schematic diagram of the metal band structure in related technologies;

[0054] Figure 17 This is a metallographic cross-sectional schematic diagram of the cathode filament of a related technology;

[0055] Figure 17a This is a partial schematic diagram of the metallographic cross-section of a cathode filament in a related technology.

[0056] Figure 17b This is a schematic diagram of the grain size distribution in the filament core of a cathode filament in a related technology.

[0057] Figure 17c This is a schematic diagram of the grain morphology distribution in the filament core of a cathode filament in a related technology.

[0058] Explanation of key component reference numerals:

[0059] Microwave cooking appliance 1000, cathode filament 100, magnetron 200, cathode assembly 300, anode assembly 400, filament 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, controller 20, processor 21, memory 22, power meter 30. Detailed Implementation

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] Please refer to Figures 1 to 3 , Figure 5 and Figure 6 This invention provides a control method for a microwave cooking appliance 1000. The microwave cooking appliance 1000 includes a magnetron 200. The magnetron 200 includes a cathode filament 100, which includes a filament core 14 and a carbonized layer 16. The carbonized layer 16 covers the filament core 14 at least in the circumferential direction. The filament core 14 is made of lanthanum-tungsten, and the carbonized layer 16 is a lanthanum-tungsten carbonized layer.

[0066] Control methods include:

[0067] Step S01: Power is supplied to the magnetron 200 to make the magnetron 200 oscillate;

[0068] Step S03: After the magnetron 200 has started oscillating, reduce the operating power of the cathode filament 100.

[0069] In the control method of the microwave cooking appliance 1000 described above, the filament core 14 is made of lanthanum-tungsten, and the carbide layer 16 is a lanthanum-tungsten carbide layer. After the magnetron 200 starts oscillating, some electrons emitted by the cathode filament 100 can bombard the carbide layer 16, causing the carbide layer 16 to generate secondary electrons to maintain microwave generation. Therefore, after the magnetron 200 starts oscillating, reducing the operating power of the cathode filament 100 can still enable the magnetron 200 to generate continuous microwaves, maintaining the operation of the magnetron 200. This can, to a certain extent, reduce the operating temperature of the cathode filament 100 and extend its service life.

[0070] Specifically, the microwave cooking appliance 1000 includes a magnetron 200, and the magnetron 200 includes a cathode filament 100. Please refer to... Figure 1 , Figure 1a , Figure 5 and Figure 6The 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 5 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.

[0071] Please combine Figure 6 The magnetron 200 also 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 6 and Figure 7 The working principle of the magnetron 200 is as follows: When the magnetron 200 is working, a DC voltage (such as a DC voltage of several kilovolts) is applied between the cathode filament 100 and the anode 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, undergoing stable oscillating motion in the interaction space 32. The electron velocity is proportional to the ratio E / B, where E is the electric field strength and B is the magnetic flux density. The energy gained by the electron stream emitted from the cathode filament 100 from the electric field in the interaction space 32 is transferred to a high-frequency field under certain conditions and output as microwaves through the energy output window 38.

[0072] In one implementation, please refer to Figure 8The microwave cooking appliance 1000 includes an inverter and a controller 20. The inverter adjusts the microwave output power of the microwave cooking appliance 1000 by adjusting the DC current between the cathode filament 100 and the anode plate 30 of the magnetron 200. The inverter includes a control chip (IC) and an IGBT (Insulated Gate Bipolar Transistor). The controller 20 is electrically connected to the control chip (IC). The control chip controls the switching on and off of the two IGBTs to maintain a certain DC current, thereby providing a relatively stable DC power supply to the magnetron 200. Current I = Q / t (where I is current, Q represents charge, and t is time). When the switching frequency of the IGBT increases, the amount of charge moving per unit time increases, and therefore the current also 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 DC voltage between the cathode filament 100 and the anode plate 30 remains constant, the microwave output power can be adjusted by regulating the magnitude of the DC current between the cathode filament 100 and the anode plate 30.

[0073] In related technologies, 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 can cause the following problems: First, the high temperature can cause other materials to release gases, leading to a decrease in vacuum. Second, the high-temperature environment can cause 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 can result in insufficient electron emission, leading to a slow conversion to microwaves or even no microwave generation at all.

[0074] 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 16As 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. Furthermore, an orthogonal design can be performed for multiple experimental parameters of the carbonization reaction to ultimately achieve the desired result. Figure 11 and Figure 11a The results of carbonized layer 16 are shown.

[0075] The cathode filament 100 of this invention has a strong secondary back-bombardment capability in its carbonized layer 16. During the operation of the magnetron 200, after the magnetron 200 has started oscillating, that is, after the cathode filament 100 is energized and emits electrons, the power of the cathode filament 100 can be reduced (e.g., power is cut off). Even after power is cut off, the cathode filament 100 can still emit electrons to enable the magnetron 200 to generate microwaves for heating food. More specifically, under the influence of the magnetic field of the magnetron 200, some of the emitted electrons will back-bombard the carbonized layer 16. The back-bombarded electrons collide with the carbonized layer 16, thereby causing the carbonized layer 16 to continuously emit new electrons. For example, one back-bombarded electron can cause the emission of two new electrons, and two back-bombarded electrons can cause the emission of four new electrons, etc. Therefore, after the cathode filament 100 emits electrons while energized, even if the power is cut off (equivalent to zero power), the carbonized layer 16 can continue to emit electrons stably under the action of secondary back-bombardment, enabling the magnetron 200 to continuously and stably output microwaves to heat food.

[0076] Based on actual testing, please combine... Figure 9 A voltage of 3.3V was applied to both the original filament and the lanthanum-tungsten filament for 5 seconds. The voltage was then maintained or gradually reduced to 0V, and the changes in microwave output power corresponding to the original and lanthanum-tungsten filaments were tested. Figure 9As can be seen, for the original filament, the microwave output power slightly decreases when the operating voltage drops to 2.6V and 1.9V; the microwave output power decreases significantly when it drops to 1.2V; and the microwave output power drops to 0W at 0.7V and 0V. In contrast, during the same voltage reduction process, the lanthanum-tungsten filament of this invention can maintain a stable microwave output power, remaining above 1000W. Even when the voltage drops to 0V, the magnetron 200 can still continuously generate microwaves to enable the microwave cooking appliance 1000 to operate normally. That is, after the magnetron 200 starts oscillating, reducing the operating power of the cathode filament 100 can lower the temperature of the cathode filament 100, thereby extending the service life of the cathode filament 100.

[0077] In step S01, energizing the magnetron 200 includes simultaneously providing voltage between the anode and cathode filament 100 of the magnetron 200, and supplying power to the cathode filament 100. On the one hand, a low-voltage heating power supply is needed to heat the cathode filament 100 to the temperature required for thermionic emission. On the other hand, a high-voltage DC power supply is needed between the cathode filament 100 and the anode plate 30 to form a strong electric field, which accelerates the electrons emitted by the cathode filament 100 towards the anode plate 30. Under the action of the external magnetic field, the electrons do not move in a straight line, but move along a spiral path under the combined action of the magnetic and electric fields, and interact with the interaction space 32 of the magnetron 200.

[0078] As the electron group moves periodically within the interaction space 32, energy is gradually converted into a high-frequency electromagnetic oscillation signal, causing the magnetron 200 to enter a working state, i.e., "oscillation start-up". After oscillation start-up, the magnetron 200 can emit microwaves to heat food.

[0079] In step S03, after the magnetron 200 has started oscillating and begins to output microwaves, the controller 20 can control the cathode filament 100 to reduce its operating power. The operating power of the cathode filament 100 refers to the electrical power applied to heat the cathode filament 100 to achieve thermionic emission.

[0080] In one embodiment, the controller 20 can reduce the operating power of the cathode filament 100 to zero, that is, cut off the power to the cathode filament 100. At this time, the cathode filament 100 no longer relies on its own heating to maintain thermionic emission, but instead uses a portion of the emitted electrons to bombard the carbide layer 16 under the action of a magnetic field, thereby exciting the carbide layer 16 to emit secondary electrons to maintain thermionic emission.

[0081] Understandably, in step S03, since the magnetron 200 has already started oscillating in step S01, some of the electrons emitted by the cathode filament 100 can bombard the carbide layer 16 under the influence of the magnetic field, thereby exciting the carbide layer 16 to emit secondary electrons to maintain microwave generation. Therefore, the cathode filament 100 no longer needs to maintain a high temperature; microwave generation can be maintained by bombarding the carbide layer 16 with some electrons. At this time, reducing the operating power of the cathode filament 100 can, to some extent, reduce the operating temperature of the cathode filament 100 and extend its service life.

[0082] Please combine Figure 10 , Figure 10 This describes the thermionic emission models of the original mode in related technologies and the novel mode of this invention. In the original mode, the cathode filament is continuously heated, causing it to continuously emit primary electrons while simultaneously generating secondary electrons through backflushing. In the novel mode, after oscillation is initiated, heating of the cathode filament 100 can be stopped, allowing it to generate secondary electrons through backflushing to maintain the continuous generation of microwaves.

[0083] exist Figure 1 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.

[0084] 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.

[0085] Please combine Figure 17 and Figure 17a , Figure 17 This is a cross-sectional view of a thorium-tungsten filament in a related technology. Figure 17a This is a partially enlarged cross-sectional view of a thorium-tungsten filament from a related technology. From Figure 17 and Figure 17a 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.

[0086] Please combine Figure 11 and Figure 11a , Figure 11 This is a cross-sectional view of the cathode filament 100 comprising lanthanum-tungsten material according to an embodiment of the present invention. Figure 11a 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 11 and Figure 11a 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.

[0087] Based on actual testing, please combine... Figure 13 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.

[0088] 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.

[0089] In some implementations, step S01 includes:

[0090] Powering the magnetron 200 for a preset time causes the magnetron 200 to start oscillating;

[0091] Step S03 includes:

[0092] After a preset time, reduce the operating power of the cathode filament 100.

[0093] Therefore, the start-up of the magnetron 200 can be determined by setting a preset duration.

[0094] Specifically, the preset duration refers to the pre-set energizing duration for the magnetron 200 to complete oscillation. Optionally, the preset duration can be pre-set through simulation, testing, or other methods based on the structural characteristics of the magnetron 200, ambient temperature, heating efficiency of the cathode filament 100, and operating voltage and / or operating current of the cathode filament 100. This embodiment of the invention does not impose specific limitations on this.

[0095] In step S01, voltage is simultaneously supplied between the anode and cathode filament 100 of the magnetron 200, and power is supplied to the cathode filament 100 for a preset duration, so that the magnetron 200 can start oscillating and form a stable microwave oscillation output.

[0096] In step S03, after a preset time, that is, after the magnetron 200 has started oscillating, the working power of the cathode filament 100 is reduced.

[0097] In some implementations, the preset duration is negatively correlated with the operating voltage and / or operating current of the cathode filament 100.

[0098] Therefore, it can be ensured to a certain extent that the magnetron 200 will successfully start oscillating within the preset time.

[0099] Specifically, please combine Figure 14 , Figure 14 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 for the magnetron 200 to start generating microwaves after being energized. From... Figure 14 As can be seen, the higher the operating voltage of the cathode filament 100, the shorter the start-up time, indicating that a higher voltage helps to accelerate the heating speed of the cathode filament 100, thus enabling it to enter the emission state more quickly.

[0100] Understandably, the preset duration is related to the start-up time of the magnetron 200, which in turn is affected by the operating voltage of the cathode filament 100. That is, the higher the operating voltage, the shorter the start-up time, and the shorter the preset duration.

[0101] The higher the operating current of the cathode filament 100, the shorter the oscillation time, indicating that a higher current helps to accelerate the heating rate of the cathode filament 100, thus enabling it to enter the emission state more quickly. The preset duration is related to the oscillation time of the magnetron 200, which in turn is affected by the operating current of the cathode filament 100. That is, the higher the operating current, the shorter the oscillation time, and the shorter the preset duration.

[0102] In some examples, the preset duration t is 2 seconds, 2.5 seconds, 3 seconds, 3.5 seconds, 4 seconds, 4.5 seconds, 5 seconds, 5.5 seconds, 6 seconds, or other values ​​between 2 seconds and 6 seconds.

[0103] In some embodiments, the cathode filament 100 operates at a voltage of 2.0 volts to 4.3 volts, or at a current of 7.8 amps to 11 amps.

[0104] This can increase the starting speed of the cathode filament 100, while also preventing the cathode filament 100 from overheating to some extent.

[0105] Specifically, in step S01, the operating voltage of the cathode filament 100 is 2.0 volts to 4.3 volts. At this time, the cathode filament 100 can start oscillating quickly, thereby improving the user experience. At the same time, it can avoid the cathode filament 100 temperature from being too high due to excessive operating voltage, which helps to extend the life of the cathode filament 100.

[0106] In some examples, the operating voltage U1 of the cathode filament 100 is 2.0 V, 2.2 V, 2.4 V, 2.6 V, 2.8 V, 3.0 V, 3.2 V, 3.4 V, 3.6 V, 3.8 V, 4.0 V, 4.2 V, 4.3 V, or other values ​​between 2.0 V and 4.3 V.

[0107] In some examples, the operating current I1 is 7.8 A, 8 A, 8.2 A, 8.4 A, 8.6 A, 8.8 A, 9 A, 9.2 A, 9.4 A, 9.6 A, 9.8 A, 10 A, 10.2 A, 10.4 A, 10.6 A, 10.8 A, 11 A, or other values ​​greater than or equal to 7.8 A and less than or equal to 11 A.

[0108] In some implementations, step S03 includes:

[0109] Reduce the operating power of the cathode filament 100 to zero power.

[0110] This can further reduce the operating temperature of the cathode filament 100 and the power consumption of the microwave cooking appliance 1000.

[0111] Specifically, the operating power of the cathode filament 100 is reduced to zero, which means the power to the cathode filament 100 is turned off. At this time, the cathode filament 100 no longer relies on its own heating to maintain thermionic emission. Instead, a portion of the emitted electrons can bombard the carbide layer 16 under the influence of a magnetic field, thereby exciting the carbide layer 16 to emit secondary electrons to maintain thermionic emission. The cathode filament 100 of this embodiment has a strong secondary bombardment capability of the carbide layer 16. Even when the power is off, the cathode filament 100 can still maintain a certain intensity of electron emission, thus ensuring that the magnetron 200 continuously outputs microwaves.

[0112] In some implementations, please refer to Figure 4 The control methods include:

[0113] Step S05: During the oscillation process of the magnetron 200, monitor the microwave output power of the microwave cooking appliance 1000;

[0114] Step S07: When the microwave output power of the microwave cooking appliance 1000 is greater than or equal to the set power, the magnetron 200 is confirmed to have started oscillation.

[0115] Therefore, the start-up of the magnetron 200 can be determined by the microwave output power of the microwave cooking appliance 1000.

[0116] Specifically, the set power refers to the reference power threshold used to determine whether the magnetron 200 has completed oscillation. Optionally, the set power is equal to the microwave power that the magnetron 200 can output after entering a stable oscillation state. In one example, the set power is equal to 1000 watts.

[0117] During the oscillation process of magnetron 200, that is, during the process of energizing magnetron 200 to start oscillation, the microwave output power of microwave cooking appliance 1000 can be monitored in real time. When the detected microwave output power is greater than or equal to the set power, it can be considered that the oscillation of magnetron 100 is complete. Afterwards, the operating power of cathode filament 100 can be reduced to lower the operating temperature of cathode filament 100.

[0118] Optionally, step S05 can be executed in parallel with step S01, that is, the monitoring of microwave output power is started at the same time as the magnetron 200 is powered on; or, step S05 can be included in the execution process of step S01 to assist in the real-time determination of the oscillation state of the magnetron 200.

[0119] Similarly, step S07 can be executed independently before step S03 to determine whether the magnetron 200 has completed oscillation; or it can be integrated into step S03 as a prerequisite for step S03 to trigger a reduction in the operating power of the cathode filament 100.

[0120] Optionally, the microwave cooking appliance 1000 includes a power meter 30 and a controller 20, which are electrically connected. The power meter 30 can be used to monitor the microwave output power of the microwave cooking appliance 1000 in real time and feed the monitoring results back to the controller 20. The controller 20 can determine whether the magnetron 200 has started oscillating based on the detection results fed back by the power meter 30.

[0121] Please combine Figure 15 A microwave cooking appliance 1000 provided by an embodiment of the present invention includes a magnetron 200 and a controller 20. The magnetron 200 includes a cathode filament 100, which 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, and the carbonized layer is a lanthanum-tungsten carbonized layer. The controller 20 includes a processor 21 and a memory 22. The memory 22 stores a computer program. When the computer program is executed by the processor 21, it implements the steps of the control method of the microwave cooking appliance 1000 according to any of the above embodiments.

[0122] In the aforementioned microwave cooking appliance 1000, the filament core 14 is made of lanthanum-tungsten, and the carbide layer 16 is a lanthanum-tungsten carbide layer. After the magnetron 200 starts oscillating, some electrons emitted by the cathode filament 100 can bombard the carbide layer 16, causing the carbide layer 16 to generate secondary electrons to maintain microwave generation. Therefore, even when the operating power of the cathode filament 100 is reduced after the magnetron 200 starts oscillating, the magnetron 200 can still generate continuous microwaves, maintaining the operation of the magnetron 200. This can, to a certain extent, reduce the operating temperature of the cathode filament 100 and extend its service life.

[0123] Specifically, the microwave cooking appliance 1000 includes, but is not limited to, microwave ovens, microwave-steam-grill combos, and integrated cooktops. The magnetron 200 can serve as a microwave source, and the microwaves generated by the magnetron 200 can be guided through a waveguide into the cooking cavity of the microwave cooking appliance 1000 to cook the food inside the cooking cavity.

[0124] Please combine Figure 6 The 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 6 and Figure 7 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.

[0125] In one embodiment, the cathode assembly 300 includes a bracket 18 with two end caps 26, each containing one end of a cathode filament 100. Each end cap 26 has a slot into which the two ends of the cathode filament 100 are inserted, allowing for convenient mounting of the cathode filament 100 onto the bracket 18. The cathode assembly 300 also includes connecting rods 20 and a cathode connector 24, which connects to the two end caps 26 via the 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.

[0126] 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 16 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 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. Furthermore, an orthogonal design can be performed for multiple experimental parameters of the carbonization reaction to ultimately achieve the desired result. Figure 11 and Figure 11a The results of carbonized layer 16 are shown.

[0127] The cathode filament 100 of this invention has a strong secondary back-bombardment capability in its carbonized layer 16. During the operation of the magnetron 200, after the magnetron 200 has started oscillating, that is, after the cathode filament 100 is energized and emits electrons, the power of the cathode filament 100 can be reduced (e.g., power is cut off). Even after power is cut off, the cathode filament 100 can still emit electrons to enable the magnetron 200 to generate microwaves for heating food. More specifically, under the influence of the magnetic field of the magnetron 200, some of the emitted electrons will back-bombard the carbonized layer 16. The back-bombarded electrons collide with the carbonized layer 16, thereby causing the carbonized layer 16 to continuously emit new electrons. For example, one back-bombarded electron can cause the emission of two new electrons, and two back-bombarded electrons can cause the emission of four new electrons, etc. Therefore, after the cathode filament 100 emits electrons while energized, even if the power is cut off (equivalent to zero power), the carbonized layer 16 can continue to emit electrons stably under the action of secondary back-bombardment, enabling the magnetron 200 to continuously and stably output microwaves to heat food.

[0128] In some embodiments, the cathode filament 100 has a spiral structure or is cylindrical.

[0129] Therefore, the shape of the cathode filament 100 can be selected according to different application scenarios.

[0130] 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.

[0131] 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.

[0132] In some embodiments, the thickness of the carbonized layer 16 is 6% to 10% of the thickness of the cathode filament 100.

[0133] Therefore, the long-term electron emission capability of the cathode filament 100 can be guaranteed to a certain extent.

[0134] Specifically, please combine Figure 1 and 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.

[0135] 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.

[0136] Please combine Figure 1a and Figure 2aIn 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.

[0137] 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.

[0138] The thickness of the carbide layer 16 is 6% to 10% of the thickness of the cathode filament 100. The thickness ratio of the carbide layer 16 is moderate. During the long-term use of the cathode filament 100, it can ensure to a certain extent that the filament core 14 can continuously provide lanthanum to the carbide layer 16, so that the carbide layer 16 has a long-term stable electron emission capability.

[0139] 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 100, 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 100.

[0140] In some embodiments, the thickness of the carbonized layer 16 is 8% of the thickness of the cathode filament 100.

[0141] Therefore, the thickness of the carbonized layer 16 can be further prioritized.

[0142] 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.

[0143] Please combine Figure 12 , Figure 12This 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 12 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 100. 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.

[0144] In some embodiments, when the cathode filament 100 has a helical structure, the thickness D1 of the carbide layer 16 is 42 μm (micrometers), and the thickness D2 of the cathode filament 100 is 0.5 mm (millimeters); or,

[0145] When the cathode filament 100 is cylindrical, the thickness of the carbonized layer 16 is 35 μm to 45 μm, and the thickness of the cathode filament 100 is 0.4 mm.

[0146] This is beneficial for increasing the electron emission capability of the cathode filament 100.

[0147] Specifically, when the cathode filament 100 has a spiral structure, the thickness of the carbonized layer 16 is D1 = 42 μm, and the thickness of the cathode filament 100 is equal to the thickness of the wire 12, D2 = 0.5 mm.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] In some embodiments, the cathode filament 100 is made of at least one of yttrium, rhenium, lutetium, zirconium, and hafnium.

[0152] This can improve the electron emission capability, melting point, and / or saturated vapor pressure of the cathode filament 100.

[0153] 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.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] 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.

[0158] In some embodiments, the grain size of the filament core 14 ranges from 0.4 μm to 2 μm.

[0159] This is beneficial for increasing the electron emission capability of the cathode filament 100.

[0160] 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 11b and Figure 11c 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 17b and Figure 17c The thorium-tungsten grains are small and uniformly distributed, which helps to increase the electron emission capability of the cathode filament 100.

[0161] 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.

[0162] In some embodiments, the length L of the cathode filament 100 is 12 ± 0.5 mm.

[0163] Therefore, the length of the cathode filament 100 is adapted to the spatial structure of the magnetron 200.

[0164] 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.

[0165] 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.

[0166] 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 1000 of corresponding structural dimensions, thereby improving the versatility of the cathode filament 100.

[0167] 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 1000 can operate stably to heat the food.

[0168] In some embodiments, the cathode filament 100 is capable of emitting electrons when the microwave cooking appliance 1000 has an output power of 100 watts.

[0169] Therefore, the cathode filament 100 can be adapted to more application scenarios of microwave cooking appliances 1000.

[0170] Specifically, the microwave cooking appliance 1000 with magnetron 200 is used in applications requiring low power, such as microwave heating milk or microwave boiling milk. In one embodiment, the output power of the microwave cooking appliance 1000 is 100 watts. The cathode filament 100 of this embodiment can emit electrons even when the output power of the microwave cooking appliance 1000 is 100 watts, enabling the microwave cooking appliance 1000 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 1000.

[0171] Actual measurements show that the cathode filament 100 outputs 100 watts in the microwave cooking appliance 1000, which can operate stably and heat food.

[0172] 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 layers. Its emission capability is improved by 92% compared to the original product. The carbide layer 16 of this invention can make its secondary back-bombing capability strong, so that secondary electrons are continuously emitted. Therefore, after the cathode filament 100 emits electrons after heating, it can still continue to operate stably under power failure (0A current). When the minimum output power of the microwave cooking appliance 1000 is 100 watts, the cathode filament 100 can also enable the magnetron 200 to output stable microwaves, so that the microwave cooking appliance 1000 can heat the food.

[0173] This invention provides a computer-readable storage medium storing a computer program that, when executed by a processor 21, implements the steps of the control method for the microwave cooking appliance 1000 according to any of the above embodiments.

[0174] In the aforementioned computer-readable storage medium, the filament core 14 is made of lanthanum-tungsten, and the carbide layer 16 is a lanthanum-tungsten carbide layer. After the magnetron 200 starts oscillating, some electrons emitted by the cathode filament 100 can bombard the carbide layer 16, causing the carbide layer 16 to generate secondary electrons to maintain microwave generation. Therefore, after the magnetron 200 starts oscillating, reducing the operating power of the cathode filament 100 can still enable the magnetron 200 to generate continuous microwaves, maintaining the operation of the magnetron 200. This can, to a certain extent, reduce the operating temperature of the cathode filament 100 and extend its service life.

[0175] 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.

[0176] 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 control method for a microwave cooking appliance, characterized in that, The microwave cooking appliance includes a magnetron, the magnetron includes a cathode filament, 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 material of the filament core includes lanthanum tungsten material, and the carbonized layer includes a lanthanum tungsten carbonized layer; The control method includes: Powering the magnetron causes it to oscillate. After the magnetron has started oscillating, reduce the operating power of the cathode filament.

2. The control method according to claim 1, characterized in that, Energizing the magnetron to cause it to oscillate includes: The magnetron is energized for a preset duration to cause it to oscillate. After the magnetron has started oscillating, reducing the operating power of the cathode filament includes: After the preset time, the operating power of the cathode filament is reduced.

3. The control method according to claim 2, characterized in that, The preset duration is negatively correlated with the operating voltage and / or operating current of the cathode filament.

4. The control method according to claim 3, characterized in that, The cathode filament operates at a voltage of 2.0 volts to 4.3 volts, or at a current of 7.8 amps to 11 amps.

5. The control method according to claim 1, characterized in that, After the magnetron has started oscillating, reducing the operating power of the cathode filament includes: Reduce the operating power of the cathode filament to zero power.

6. The control method according to claim 1, characterized in that, The control method includes: During the start-up process of the magnetron, the microwave output power of the microwave cooking appliance is monitored; When the microwave output power of the microwave cooking appliance is greater than or equal to the set power, it is determined that the magnetron has completed oscillation.

7. A microwave cooking appliance, comprising a controller and a magnetron, the magnetron comprising a cathode filament, 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, and the carbonized layer comprising a lanthanum-tungsten carbonized layer; The controller includes a processor and a memory, the memory storing a computer program that, when executed by the processor, implements the steps of the control method for a microwave cooking appliance according to any one of claims 1-6.

8. The microwave cooking appliance according to claim 7, characterized in that, The cathode filament has a spiral structure or is cylindrical.

9. The microwave cooking appliance according to claim 7, characterized in that, The thickness of the carbonized layer is 6% to 10% of the thickness of the cathode filament.

10. The microwave cooking appliance according to claim 7 or 9, characterized in that, The thickness of the carbonized layer is 8% of the thickness of the cathode filament.

11. The microwave cooking appliance according to claim 7 or 9, characterized in that, 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 μm to 45 μm, and the thickness of the cathode filament is 0.4 mm.

12. The microwave cooking appliance according to claim 7, characterized in that, The cathode filament material also includes at least one of yttrium, rhenium, lutetium, zirconium, and hafnium.

13. The microwave cooking appliance according to claim 7, characterized in that, The grain size of the filament core ranges from 0.4 μm to 2 μm.

14. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the control method for the microwave cooking appliance according to any one of claims 1-6.

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