Magnetron heating control method

Abstract

The invention relates to the technical field of magnetrons, in particular to a magnetron heating control method. The control mode of the magnetron heating control method is as follows: the low-voltage electric power output of the transformer is controlled to be 1.4-2.0 V, and continuous operation is carried out until the end; or after the low-voltage electric power output is controlled to be 3.0-3.6 V and continuous operation is carried out for 5-10 s, the low-voltage electric power output is reduced to 0 V by adopting the voltage regulating module and continuous operation is carried out until the end; or the low-voltage electric power output is controlled to be 3.0-3.6 V for continuous operation for 5-10 s, then the low-voltage electric power output is reduced to 1.4-2.0 V for continuous operation by adopting the voltage regulating module, and the magnitude of the low-voltage electric power output is regulated by the voltage regulator in the operation process so that the temperature of the outer surface of the magnetron is controlled to be within the preset temperature range until the operation is finished. According to the magnetron heating control method, the actual working temperature of the lamp filament can be kept in a proper working temperature range, and the service life and the use stability of a heating device can be improved. In addition, electric energy consumption can be effectively reduced.

Description

[0001] This application claims the priority of the Chinese patent application filed with the China Patent Office on October 25, 2023, with application number 2023113863234 and invention name “A tungsten carbide alloy filament, its preparation method, and heating device”, the entire contents of which are incorporated by reference in this application. Technical Field

[0002] The present application relates to the technical field of magnetrons, and in particular to a magnetron heating control method. Background Art

[0003] The cathode filament is the electron emitter and is widely used in the field of microwave oven magnetrons. The performance of the cathode filament has a great influence on the working characteristics and life of the magnetron and is regarded as the heart of the magnetron. The existing filament material is mainly made of tungsten-thorium oxide material.

[0004] At present, the existing method of providing electric energy for the magnetron of a microwave oven and controlling the heating operation of the magnetron is: the power supply is connected to a transformer, and the output power of the transformer is divided into two paths, one is high voltage (voltage 2000~6000V), which is respectively connected to the cathode of the magnetron (that is, the filament of the cathode structure of the magnetron) and the anode to form an electric field, and the other is low voltage, which is connected to the filament of the cathode structure of the magnetron.

[0005] For the existing tungsten-thorium oxide filament, the output voltage of the low-voltage circuit in the transformer is generally controlled at about 3.3V when the magnetron is powered on for heating. At this voltage, the cathode tungsten-thorium oxide filament can be powered on to generate heat, and electrons can overcome the material barrier and be emitted. Since the temperature required for the existing tungsten-thorium oxide filament to overcome the filament barrier and emit electrons is relatively high, and the thorium element has a high melting point, the operating temperature of the filament also needs to be relatively high.

[0006] When the magnetron is running, the heat required for the cathode filament to reach the required temperature is composed of three parts: the first is the heat generated by the cathode filament when it is powered on; the second is that the kinetic energy of the electrons emitted by the filament is converted into heat when some of the electrons fly back and forth in the electromagnetic field between the anode and cathode of the magnetron; the third is the heat brought to the cathode filament by the high-temperature thermal radiation of the magnetron anode.

[0007] When the heating control method of the tungsten-thorium oxide filament type magnetron is applied to a magnetron made of other filament materials (compared with the tungsten-thorium oxide filament, the temperature required to overcome the filament barrier to emit electrons is relatively low, and the melting point and the suitable working temperature of the filament are both low), the cathode itself will continue to heat up. Based on the temperature required to overcome the filament barrier to emit electrons, this will cause the actual working temperature of the cathode filament to be high, resulting in increased oxide loss of the cathode filament, which will adversely affect the stable operation and service life of the magnetron. For example, compared with the tungsten-thorium oxide filament, the temperature required for the tungsten-rare earth oxide cathode filament to overcome the filament barrier to emit electrons is not so high, and the melting point of the rare earth single substance atoms generated by the tungsten-rare earth tungsten filament reaction is relatively low. If the control method of the tungsten-thorium oxide magnetron is applied to the magnetron made of the tungsten-rare earth oxide material filament, the tungsten-rare earth oxide cathode filament will work at a higher working temperature, resulting in excessive loss of rare earth in the material component, thereby damaging its service life. Summary of the invention

[0008] In order to solve the problems existing in the above-mentioned prior art, the present application provides a magnetron heating control method, and the specific technical solution is as follows: The present application provides a magnetron heating control method, wherein the heating system of the magnetron includes a power conversion circuit; the power conversion circuit includes a transformer for providing voltage to the anode and cathode filaments of the magnetron, and the transformer includes a high-voltage winding for generating a high-voltage electric power output and a low-voltage winding for generating a low-voltage electric power output; the anode and cathode filaments of the magnetron receive the high-voltage electric power output and the low-voltage electric power output respectively; the heating control method includes the following steps: the low-voltage electric power output of the transformer is preset to 1.4 to 2.0V, and after the power supply is energized to the power conversion circuit, the low-voltage electric power output is controlled to run continuously at 1.4 to 2.0V until the power supply of the power conversion circuit is disconnected.

[0009] In some embodiments, the low voltage electric power output of the transformer is preset to 1.6-2.0V. After the power supply is powered on to the power conversion circuit, the low voltage electric power output is controlled to run continuously at 1.6-2.0V until the power supply of the power conversion circuit is disconnected.

[0010] The present application provides a magnetron heating control method, wherein the heating system of the magnetron includes a power conversion circuit, a control module, and a voltage regulating module electrically connected to the control module; the power conversion circuit includes a transformer for providing voltage to the anode and cathode filament of the magnetron, and the transformer includes a high-voltage winding for generating a high-voltage electric power output and a low-voltage winding for generating a low-voltage electric power output; the anode and cathode filament of the magnetron receive the high-voltage electric power output and the low-voltage electric power output respectively; wherein the voltage regulating module is connected in series between the output end of the low-voltage winding and the voltage input end of the cathode filament to regulate the low-voltage electric power output; The heating control method includes the following steps: presetting the low-voltage electric power output to 3.0-3.6V, and after the power supply is energized to the power conversion circuit, the low-voltage electric power output is controlled to be 3.0-3.6V and continuously runs for 5-10s; after continuously running for 5-10s, the control module controls the voltage regulating module to disconnect, so that the low-voltage electric power output is reduced to 0V, and continues to run until the power supply of the power conversion circuit is disconnected; or, after continuously running for 5-10s, the control module controls the voltage regulating module to reduce the low-voltage electric power output to 1.4-2.0V and continuously run, and during the operation, the low-voltage electric power output is adjusted by the voltage regulating module, so that the outer surface temperature of the magnetron is controlled within a predetermined temperature range.

[0011] In some embodiments, the heating control method includes the following steps: the low-voltage electric power output is preset to 3.3V, and after the power supply is powered on to the power conversion circuit, the low-voltage electric power output is controlled to 3.3V and continues to run for 5 to 10 seconds; after running continuously for 5 to 10 seconds, the control module controls the voltage regulating module to disconnect, so that the low-voltage electric power output is reduced to 0V, and continues to run until the power supply of the power conversion circuit is disconnected; or, after running continuously for 5 to 10 seconds, the control module controls the voltage regulating module to reduce the low-voltage electric power output to 1.6 to 2.0V and continue to run, and during the operation, the low-voltage electric power output is adjusted by the voltage regulating module so that the outer surface temperature of the magnetron is controlled within a predetermined temperature range.

[0012] In some embodiments, when the voltage regulating module is a relay, the normally open contact of the relay is connected in series between the low-voltage winding output end and the voltage input end of the cathode filament; the heating control method includes the following steps: the low-voltage electric power output is preset to 3.0~3.6V, and after the power supply is energized to the power conversion circuit, the low-voltage electric power output is controlled to run continuously at 3.0~3.6V for 5~10s; then the control module controls the relay to disconnect, so that the low-voltage electric power output is reduced to 0V, and continues to run in the relay disconnected state until the power supply of the power conversion circuit is disconnected.

[0013] In some embodiments, when the voltage regulating module includes a temperature sensing component and a voltage regulator for sensing the temperature of the outer surface of the magnetron, the voltage regulator is connected in series between the output end of the low-voltage winding and the voltage input end of the cathode filament, and is used to increase or decrease the low-voltage electric power output; the temperature sensing component and the voltage regulator are electrically connected to the control module; the heating control method includes the following steps: the low-voltage electric power output is preset to 3.0~3.6V, and after the power supply is energized to the power conversion circuit, the low-voltage electric power output is controlled to 3.0~3.6V and continues to operate for 5~10s; then the control module controls the voltage regulator to reduce the low-voltage electric power output to 1.4~2.0V for continuous operation, and during the operation, the low-voltage electric power output is adjusted by the voltage regulator so that the temperature sensed by the temperature sensing component is controlled within a predetermined temperature range.

[0014] In some embodiments, the process of adjusting the low-voltage electric power output through the voltage regulator during operation is as follows: when the temperature sensed by the temperature sensing component is greater than or equal to 350°C, the control module controls the voltage regulator, and the voltage regulator adjusts the low-voltage electric power output to 1.4V for operation; when the temperature sensed by the temperature sensing component is greater than or equal to 355°C, the low-voltage electric power output is reduced to 1.2V for operation; when the temperature sensed by the temperature sensing component is greater than or equal to 380°C, the low-voltage electric power output is reduced to 0V for operation; when the temperature sensed by the temperature sensing component is less than or equal to 330°C, the low-voltage electric power output is increased to 1.4~2.0V for operation.

[0015] In some embodiments, the operating temperature of the cathode filament in the magnetron is 1100°C to 1500°C; the components of the cathode filament include element M; and the element M is selected from one or more combinations of La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, and Zr.

[0016] In some embodiments, the cathode filament in the magnetron includes a substrate and a carbide layer attached to the outer surface of the substrate; wherein the grain width of the carbide layer is between 1.0 μm and 15.0 μm; the components of the substrate and the carbide layer both contain tungsten, carbon, oxygen and M; the M element is selected from one or more combinations of La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, and Zr; wherein the components of the tungsten carbide alloy filament do not contain thorium.

[0017] In some embodiments, a plurality of second channels are distributed on the carbonized layer to form a radially stacked layered structure on the cross section of the filament; a plurality of first channels are distributed on the carbonized layer, and at least some of the first channels are cross-arranged with the second channels to divide the layered structure into a plurality of block structures.

[0018] Based on the above, compared with the prior art, this application has the following beneficial effects: The magnetron heating control method provided by the present application can keep the actual working temperature of the filament within a suitable working temperature range, preventing the temperature from continuously rising, which is beneficial to improving the service life and stability of the heating device. In addition, the heating control method can effectively reduce power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0020] Figure 1 A schematic diagram of a portion of the structure of the tungsten alloy filament provided in this application; Figure 2 A schematic diagram of the cross-section of a tungsten alloy filament provided in this application; Figure 3 A schematic diagram of the longitudinal section of the tungsten alloy filament provided in this application; Figure 4 for Figure 2 The enlarged view of point A in the middle; Figure 5 Schematic diagram of the overall structure of the tungsten alloy filament provided in this application; Figure 6 A partial structural schematic diagram of a cross section of a tungsten alloy filament provided in this application; Figure 7 A circuit diagram of a first magnetron heating control method provided in this application; Figure 8 A circuit diagram of the second magnetron heating control method provided in this application; Fig. 9 This is a circuit diagram of the third magnetron heating control method provided in this application.

[0021] Figure numerals: 100, substrate; 200, carbonized layer; 210, channel; 220, outer edge of the filament; 211, first channel; 212, second channel; 10, power supply; 20, transformer; 30, low-voltage winding; 40, high-voltage winding; 50, magnetron; 60, relay; 70, voltage regulator. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments; the technical features designed in different implementation modes of the present application described below can be combined with each other as long as they do not conflict with each other; based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0023] In the description of this application, it should be noted that all terms (including technical terms and scientific terms) used in this application have the same meanings as those generally understood by ordinary technicians in the field to which this application belongs, and cannot be understood as limitations on this application; it should be further understood that the terms used in this application should be understood to have meanings consistent with the meanings of these terms in the context of this specification and in the relevant fields, and should not be understood in an idealized or overly formal sense, unless explicitly defined in this application.

[0024] The present application provides a tungsten carbide alloy filament, and its technical solution is as follows: The tungsten carbide alloy filament comprises a substrate and a carbide layer attached to the outer surface of the substrate; the grain width of the carbide layer is between 1.0 μm and 15.0 μm; the components of the substrate include M element, and the components of the carbide layer include carbon element and M element; the M element is selected from one or more combinations of La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, and Zr; wherein the components of the tungsten carbide alloy filament do not include thorium element.

[0025] 1. Preferred structural features and phase composition features of the carbonized layer 200: (1) The M element in the carbonized layer exists in the form of an oxide, and the carbon element exists in the form of a carbide, and the particle size of the M oxide particles is 10 nm to 1000 nm.

[0026] (2) If Figure 1-4 As shown, a plurality of first channels 211 are distributed on the carbonized layer 200; at least part of the first channels 211 are distributed along the radial direction of the cross section of the filament; and / or at least part of the first channels 211 point to the center of the cross section of the filament.

[0027] (3) If Figure 4 and 6As shown, a plurality of channels 210 are distributed on the carbide layer 200, and the channels 210 include a first channel 211 and a plurality of second channels 212; at least a portion of the first channels 211 are distributed radially along the cross section of the tungsten alloy filament; and / or, at least a portion of the first channels 211 point to the center of the cross section of the tungsten alloy filament; and at least a portion of the second channels 212 are distributed circumferentially along the cross section of the tungsten alloy filament, wherein at least a portion of the second channels 212 are cross-arranged with the first channels 211, so that the cross section of the carbide layer 200 is in a layer block shape. Specifically, the present application controls the structure of the carbonized layer 200: its grain size is controlled within a certain small range, so that a large number of first channels 211 and second channels 212 are formed, thereby forming a layer block structure, and the rare earth components in the tungsten alloy filament are matched to achieve a stable emission effect. The specific mechanism is: Figure 6 As shown, the second channel 212 divides the carbonized layer 200 into a layered structure stacked in a radial direction, and then divides the carbonized layer 200 into a block structure through the first channel 211 designed to cross it, so that the carbonized layer 200 forms a layer block. Compared with other structural distributions, for example, the first channel 211 divides the carbide layer 200 into a block structure, the second channel 212 divides the carbide layer 200 into a radially stacked layer structure, the second channel 212 and the first channel 211 are not designed to intersect, and the carbide layer 200 forms two clearly divided areas, one area is a block structure, and the other area is a layered structure; the grain control of the carbide layer 200 of the present application makes its cross section a layered block design, which has the advantages of: the radial or quasi-vertical distribution design of the first channel 211 is conducive to the outward migration of rare earth atoms of the M element, and the layered structure in the carbide layer 200 separated by the second channel 212 is where the oxides of M are distributed. The second channel 212 is combined with the first channel 211 (vertical channel 210) to form a layered block of the carbide layer 200, which can effectively control the migration speed of the oxides of M to the filament surface (i.e., the outer surface of the carbide layer 200), thereby improving the stable emission ability of the tungsten carbide alloy. It should be noted that: Figure 1 The filament structure, Figure 2 The cross section of the filament and Figure 3 As shown in the longitudinal section of the filament, the “radial distribution along the cross section of the filament” and “at least part of the first channel 211 points to the center of the cross section of the filament” mentioned herein. For the radial distribution and the center of the circle: it means that the end point of the first channel 211 close to the substrate 100 and the end point close to the edge of the filament are connected to form a first straight line, and the angle between the first straight line and the tangent line of the intersection of the outer edge 220 of the filament is (60-90)°.

[0028] like Figure 6As shown, for the "circumferential distribution along the cross section of the tungsten alloy filament" described in this article, the circumferential distribution means connecting the end points of the second channel 212 into a second straight line, and the angle between the second straight line and the straight line where the filament radial direction is located is (-45 to +45) degrees.

[0029] In the present application, the first channel 211 is quasi-vertically and quasi-radially distributed to the outer edge 220 of the filament (i.e., the outer edge of the carbonized layer 200). The radial or quasi-vertical distribution design of the first channel 211 is beneficial to the outward migration of M element atoms, but it does not mean that the first channel 211 is a straight line structure, nor does it mean that the two end points of the first channel 211 need to pass through to the outer edge of the substrate 100 and the carbonized layer 200 (i.e., the outer edge 220 of the filament).

[0030] In the present application, the second channel 212 is distributed along the annular direction or is cross-arranged with the first channel 211, which does not mean that the second channel 212 is a standard arc structure, and does not mean that the second channel 212 is continuously connected to run through the entire outer ring. It can be a quasi-annular distribution composed of multiple sections of second channels 212 separated from each other, or a cross-distribution of multiple sections of second channels 212 separated from each other and the first channel 211, so that the carbonized layer 200 is divided into a layered structure stacked along the radial direction.

[0031] (3) The tungsten carbide alloy filament is a spiral structure, and the thickness of the carbide layer of at least one spiral turn is 30 μm to 90 μm, preferably 35 to 45 μm, 50 to 90 μm, for example 60 μm, 70 μm, 80 μm.

[0032] (4) The carbonized layer 200 comprises W2C and WC; 2 The weight ratio of C to WC is (60-100):(0-40).

[0033] 2. Preferred component characteristics for tungsten carbide alloy materials: (1) The components of the matrix include an M element and a carbon element, wherein the M element exists in the form of an oxide, and the carbon element exists in the form of a carbide or a single carbon substance.

[0034] The present application adds one or more oxides of M and carbides or carbon elements. Since the oxides of M and carbides in the tungsten matrix react at high temperatures, for example, lanthanum oxide reacts with tungsten carbide to generate lanthanum atoms, and the size of the generated lanthanum atoms is much smaller than that of lanthanum oxide particles, the migration and diffusion speed of lanthanum atoms in the tungsten matrix will be very fast, thereby increasing the diffusion speed of M metal atoms. In summary, the present application combines the oxides of M with carbides or carbon elements, and can achieve the same or even higher electron emission capability as thoriated tungsten at a lower operating voltage (excitation temperature) than thoriated tungsten filaments, and it is easier to ensure the balance between the loss and migration of rare earth atoms in the carbide layer of the filament, thereby ensuring the stability of the electron emission of the filament.

[0035] (2) The matrix of the tungsten carbide alloy filament comprises the following components: 0.0005-0.3 wt% carbon element, 0.25-2.6 wt% M element, 0.05-0.5 wt% oxygen element, and the balance is tungsten element and inevitable impurities. Preferably, the matrix of the tungsten carbide alloy filament comprises the following components: 0.0005-0.3 wt% carbon element, 0.25-2.6 wt% M element, 0.05-0.5 wt% oxygen element, and the balance is tungsten element and inevitable impurities.

[0036] Among them, the M element can be 1.28-2.6wt%, and the tungsten alloy filament made of the tungsten alloy material with this composition ratio is better for use in microwave ovens <800W. The M element can be 0.25-1.28wt%, and the tungsten alloy filament made of the tungsten alloy material with this composition ratio is better for use in microwave ovens >800W. Furthermore, the M element can be 0.25-0.86wt%, and the tungsten alloy filament made of the tungsten alloy material with this composition ratio is better for use in microwave ovens >1000W.

[0037] Wherein, preferably, the M is present in the tungsten alloy material in the form of an oxide, and the oxide of the M is selected from one or more combinations of lanthanum oxide, yttrium oxide, scandium oxide, neodymium oxide, samarium oxide, lutetium oxide, cerium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, praseodymium oxide, erbium oxide, hafnium oxide, and zirconium oxide; the carbon element is present in the tungsten alloy material in the form of a carbide or a single carbon substance, and the carbide is selected from one or more combinations of lanthanum carbide, zirconium carbide, yttrium carbide, hafnium carbide, and tungsten carbide. For example, the oxide of the M can be selected from lanthanum oxide, or a combination of lanthanum oxide and yttrium oxide, or a combination of lanthanum oxide and zirconium oxide, or a combination of lanthanum oxide and scandium oxide, or a combination of lanthanum oxide and hafnium oxide, etc.

[0038] Preferably, the matrix of the tungsten alloy material further comprises T, wherein T is a solid solution metal element or a dispersed metal element, and T is selected from at least one of K, Re, Mo, Fe, and Co. Further preferably, the mass content of Re is less than 1000 ppm.

[0039] It should be noted that: "La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, Zr" in the text are element symbols in the periodic table, representing the metal elements lanthanum, yttrium, scandium, neodymium, samarium, lutetium, cerium, gadolinium, terbium, dysprosium, holmium, praseodymium, erbium, thulium, ytterbium, europium, hafnium and zirconium in the periodic table respectively; "K, Re, Mo, Fe, Co" in the text are element symbols in the periodic table, representing the metal elements potassium, rhenium, molybdenum, iron and cobalt in the periodic table respectively; W is the symbol of tungsten in the periodic table; C is the symbol of carbon in the periodic table; in addition, "M" and "T" are only reference symbols, do not represent elements in the periodic table, and are only used for reference.

[0040] 3. The tungsten carbide alloy filament has a spiral structure in actual use. The preferred structural features of the spiral structure of the tungsten alloy filament are as follows: 3.1 Turn control: Figure 5 The structural schematic diagram of the tungsten alloy filament shown in the figure preferably has a number of turns of (9.5-13) turns, a control tolerance of ±0.125, and a statistical CPK>1.33.

[0041] The number of turns of the filament is between 9.50 and 13.00 turns. The preferred number of turns may be between 9.70 and 10.70 turns, such as 9.90 turns, 10.00 turns, 10.28 turns, 10.5 turns, etc.; it may also be between 10.70 and 11.70 turns, such as 11.00 turns, 11.20 turns, 11.5 turns, etc.; it may also be between 11.80 and 13.00 turns, such as 12.00 turns, 12.20 turns, 12.5 turns, etc.

[0042] 3.2 Pitch uniformity, the tolerance of the tungsten alloy filament pitch L1 is ±0.02, and the statistical CPK>1.33; wherein, the tungsten alloy filament pitch L1 is Figure 5 In the implementation process, those skilled in the art can use a dedicated wire winding device to make the filament pitch uniform so that the heating device can emit electrons more stably.

[0043] It should be noted that the number of filament turns is related to the filament length L and the pitch L 1 Related, filament length L = (filament turns - 1) * L 1 .

[0044] 3.3 Pitch size: the pitch L1 of the tungsten alloy filament is 0.800~1.800mm, and the preferred pitch L 1 , can be 1.000-1.150 mm, such as 1.018 mm, 1.044 mm, 1.135 mm, etc., can also be 1.230 mm-1.330 mm, such as 1.240 mm, 1.290 mm, etc., can also be 1.400 mm-1.600 mm, such as 1.470 mm, 1.500 mm, etc.; 3.4 Length: The length L of the filament is between 10.00 and 16.00 mm, and the preferred length L can be between 10.50 and 12.00 mm, such as 11.00 mm, 11.20 mm, 11.70 mm, etc., or can be between 12.50 and 14.00 mm, such as 12.83 mm, 13.40 mm, 13.55 mm, etc.; The outer diameter of the filament Φ 1 In the range of 3.00~6.00mm, the preferred outer diameter Φ 1 , it can be 3.50~4.50mm, such as 3.70mm, 3.80mm, 3.90mm, 3.92mm, 4.00mm, etc., or it can be 5.00~6.00mm, such as 5.20mm, 5.48mm, 5.60mm, etc.

[0045] 4. The wire diameter of tungsten carbide alloy filament can reach 800μm and below: In the pressure processing process, the tungsten alloy material provided by the present application has good processing performance, and can be processed into wires with fine wire diameter specifications (i.e., fine wire diameter tungsten alloy wire), and the wire diameter tolerance can be controlled within a very small range. Furthermore, the wire diameter can reach 600μm and below, 550μm and below, or even 500μm and below. The wire diameter can be 450-550μm, such as 470μm, 490μm, 500μm, 520μm, etc., or 700-800μm, such as 750μm, 760μm, 780μm, etc.

[0046] Among them, the present application also provides the following preferred embodiments for preparing tungsten alloy wire (before carburization), carbide tungsten alloy filament, and prepare a heating device containing tungsten alloy filament: It includes the following steps: Step 1, obtaining a finished powder raw material through a doping process, a reduction process and a powder making process in sequence; wherein the doping process is solid-liquid doping or solid-solid doping; Step 2, powder pressing: using isostatic pressing to press powders of different particle sizes into green compacts, and pre-sintering the green compacts at low temperature in a hydrogen atmosphere to increase the green compact strength; wherein the powders are pressed into green compacts with a unit weight of 1.5 to 5.0 kg at a pressure of 160 to 240 MPa; Step 3: High temperature sintering: high temperature sintering is used to obtain a density of 17.5-18.3 g / cm 3 The sintered billet is to obtain the tungsten alloy material in billet form; The heating curve of the high temperature sintering method is: From room temperature to A1, the heating time H1 is (5-8) h, and A1 is (950-1250) °C; for example, H1 is (5-7) h, (7-8) h, etc., and another example is 6 h, 7.5 h, etc.; A1 is (950-1050) °C, (1050-1250) °C, etc., and another example is 1000 °C, 1100 °C, etc.; Keep warm at A1 for H2 hours, where H2 is (1-3); for example, H2 is (1-2) h, (2-3) h, etc., or 1.5 h, 2.5 h, etc.; The temperature is raised from A1 to A2, and the heating time is H3, H3 is (1.5-2.5) h, and A2 is (1300-1500) °C; for example, H3 is (1.5-2.0) h, (2.0-2.5) h, etc., and another example is 1.5 h, 2.0 h, 2.4 h, etc.; A2 is (1300-1400X) °C, (1400-1500) °C, etc., and another example is 1350 °C, 150 °C, etc.; Keep warm at A2 for H4 hours, where H4 is (2.5-4.5); for example, H4 is (2.5-3.0) h, (3.0-4.0) h, etc., and another example is 2.8 h, 3.5 h, etc.; The temperature is raised from A2 to A3, and the heating time is H5, H5 is (1-3) h, and A3 is (1700-1900) °C; for example, H5 is (1-2) h, (2-3) h, etc., and another example is 1.6 h, 2.0 h, 2.5 h, etc.; A3 is (1700-1800) °C, (1800-1900) °C, etc., and another example is 1750 °C, 1850 °C, etc.; Keep warm at A3 for H6 hours, where H6 is (1-3); for example, H6 is (1-2) h, (2-3) h, etc., and for example, 1.5 h, 2.5 h, etc.; The temperature is raised from A3 to A4, and the heating time is H7, H7 is (1-3) h, and A4 is (2050-2250) °C; for example, H7 is (1-2) h, (2-3) h, etc., and another example is 1.5 h, 2.5 h, etc.; A4 is (2050-2150) °C, (2150-2250) °C, etc., and another example is 2100 °C, 2200 °C, etc.; Keep warm at A4 for H8 hours, where H8 is (5-10); for example, H8 is (5-7) h, (7-10) h, etc., and another example is 6 h, 8 h, etc.; cool naturally from A4 to obtain.

[0047] Step 4: Pressure processing: 4.1 In the pressure processing step, the tungsten alloy sintered billet obtained after sintering is refined into an intermediate specification wire with a diameter of 1.5 to 3.5 mm; 4.2 Then, the intermediate specification wire is subjected to oxidation annealing at (1200-1500)°C, and the annealing speed is (3-10) m / min; for example, the annealing speed is (3-7) m / min, (7-10) m / min, etc., and another example is 3 m / min, 5 m / min, 7 m / min, etc.; the oxidation annealing is (1200-1350)°C, (1350-1500)°C, etc., and another example is 1250°C, 1400°C, etc.; 4.3 After oxidation annealing, the intermediate specification wire is further processed to the required wire diameter specification to obtain tungsten alloy wire; wherein, multiple passes of rotary forging and drawing are used for thinning; the oxidation annealing process is carried out in the oxidation annealing equipment, and the annealing speed refers to the speed of the wire passing through the annealing tank, which indicates the length of the wire passing through the annealing tank per unit time.

[0048] Step 5, white wire cleaning: Use electrolytic cleaning to clean the black wire into tungsten alloy white wire that can be processed into microwave oven heating device filament; Step 6, Winding: Wind the white wire into a spring-shaped filament structure for heating devices to obtain tungsten alloy wire.

[0049] 1. The preferred structural features of the tungsten alloy wire before carburization (i.e. the wire obtained after pressure processing): 1.1 Characteristics of the initial recrystallization temperature: The initial recrystallization temperature of the tungsten alloy wire provided in the present application is higher than that of the thoriated tungsten wire, which is 48%Fc to 56%Fc in the present application, while the thoriated tungsten wire is around 46%FC (2020°C).

[0050] The average size of the 80%Fc recrystallized grains of the tungsten alloy wire provided by the present application is finer than that of the thoriated tungsten wire. The average size of the 80%Fc recrystallized grains of the tungsten alloy wire provided by the present application is (1-15) μm, and the average size of the 80%Fc recrystallized grains of the thoriated tungsten filament is (16-150) μm. The above-mentioned characteristics of high initial recrystallization temperature and small average size of 80%Fc recrystallized grains make the tungsten matrix structure of the filament produced by the tungsten alloy wire of the present application finer than that of the thoriated tungsten filament after carburization in the magnetron 50, thereby making the grain width of the carbide layer of the tungsten alloy filament fine after carburization, so that the grain width of the carbide layer is controlled within the required range; There is a carbonization process in the process of preparing tungsten alloy wire into tungsten carbide alloy. The carbonization temperature is 2000-2500℃. The original thoriated tungsten filament is carbonized at this temperature (analysis shows that the reason is that its initial recrystallization temperature is too low). The grain structure will undergo recrystallization, and the grains will be coarse, resulting in the brittleness and poor seismic performance of the filament after carbonization. The problem of wire breaking is very likely to occur during the assembly, production, transportation and subsequent use of the magnetron 50 in the microwave oven. Compared with the thoriated tungsten filament, the initial recrystallization temperature of the filament material selected in this application is higher than that of the original thoriated tungsten filament, and the average size of the 80%Fc recrystallized grains is smaller than that of the original thoriated tungsten filament. After the tungsten alloy wire of this application is carbonized, the filament structure is still a fine-grained structure, which is less brittle than the traditional thoriated tungsten filament material. The tungsten alloy filament with a fine-grained structure has better seismic performance than the thoriated tungsten filament. The filament breaking rate of the magnetron 50 produced in this application is much lower than that of the magnetron 50 produced by traditional thoriated tungsten.

[0051] Optionally, the initial recrystallization temperature of the tungsten alloy wire may be 48-52%FC, such as 48%FC, 50%FC, 52%FC, etc. Optionally, the average size of the 80%Fc recrystallized grains of the tungsten alloy wire may be (1-8) μm, (8-12)% μm, (12-15) μm, etc., for example, 4.0 μm, 8.5 μm, 13 μm, etc.

[0052] 1.2 The average size characteristics of the oxide particles in the tungsten alloy wire: The average size of the oxide particles in the tungsten alloy wire is (100-500) nm The average size of the oxide particles of the tungsten alloy wire of the present application is (100-500) nm. The size of the oxide particles of the tungsten alloy wire determines the size of the oxide particles of the filament after carburization. If the oxide particles of the wire are too coarse relative to the limited range of the present application, resulting in coarse particles of the tungsten alloy filament after carburization, then during the use of the magnetron 50, it is more difficult for the oxide particles of M to migrate to the surface of the filament, which makes it easier to break the balance between the loss and replenishment of rare earth elements on the surface of the filament, and the electron emission of the magnetron 50 is more unstable.

[0053] Optionally, the average size of the oxide particles may also be (100-300) nm, (300-500) nm, etc., for example, 200 nm, 300 nm, 450 nm, etc.

[0054] 1.3 For the above tungsten alloy wire crack detection characteristics: The number of crack points detected by the above tungsten alloy wire is less than 5 (per 100 meters). Further, the number of crack points detected by the tungsten alloy wire can be less than 2 per 100 meters, such as 0 per 100 meters, 0.5 per 100 meters, 1 per 100 meters, etc. The number of crack points detected by the tungsten alloy wire is small, the filament yield is high, and the wire is not easy to break.

[0055] 2. Important control points for the preferred implementation of the method for preparing tungsten alloy wire before carburization: The present application can obtain the above-mentioned tungsten alloy wire before carbide with the above-mentioned starting recrystallization temperature and average size characteristics of oxide particles through the preferred implementation scheme of the above-mentioned preparation method. Through the carbonization treatment of the tungsten alloy wire, a tungsten carbide alloy filament with the above-mentioned carbide layer grain width, carbide layer oxide particle size and other characteristics can be obtained. The specific process control points of the preparation method for obtaining the tungsten alloy wire before carbide are as follows: (1) Oxidation annealing treatment of intermediate specification products: The present application provides a specific treatment method for oxidation annealing in the above-mentioned pressure processing step, so that the initial recrystallization temperature of the tungsten alloy is controlled within the above-mentioned required range (48%Fc~56%Fc): a stress relief oxidation annealing at a temperature of 1200~1500°C is added at the middle specification of the wire of 1.5~3.5mm, so that the initial recrystallization temperature of the tungsten alloy wire is effectively controlled within 48%Fc~56%Fc; in this preparation process, if the oxidation annealing process is removed, the initial recrystallization temperature of the tungsten alloy wire exceeds 56%Fc, and the excessively high initial recrystallization temperature will be detrimental to the electron emission performance of the tungsten carbide alloy filament under the working conditions of the magnetron 50.

[0056] (2) By controlling the time for A1 to be heated to A2 and the sintering time at A2 (1300-1500°C) during the sintering process: In the high-temperature sintering stage of the tungsten billet, the present application provides a sintering process, by controlling the time for A1 to be heated to A2 and the sintering time at A2 (1300-1500°C) during the sintering process, the sintering neck of the tungsten billet is allowed to grow rapidly, the holes are closed, and the oxide particles in the holes are prevented from being squeezed into another hole from the unclosed connecting channel during the shrinkage of the billet sintering cavity. On the basis of ensuring the density of the sintered billet, the size of the oxide particles of the sintered billet is controlled, thereby controlling the oxide size of the tungsten alloy wire or the filament after carbonization; Among them, the oxide particle size distribution range of the tungsten alloy sintered billet obtained by the above sintering process is 100-2000nm, and the average size of the oxide particles is 600-1000nm, and the average size of the oxide particles of the tungsten alloy wire is (100-500)nm; optionally, the average size of the oxide particles can also be (100-300)nm, (300-500)nm, etc., for example, 200nm, 300nm, 450nm, etc. Without the above sintering process, the oxide particle size distribution range of the tungsten alloy sintered billet is 400-5000nm, and the average size of the oxide particles is 1200-2000nm. The average size of the oxide particles of the tungsten alloy wire after further refinement is also relatively coarse (about 500-900nm).

[0057] Among them, the mechanism of the sintering process affecting the oxide size of the billet, tungsten alloy wire, and carbonized filament, and the effect of the oxide size of the tungsten alloy wire and carbonized filament on the performance of the filament are as follows: the reason why the oxide particle size is controlled within a smaller range is that the oxide particle size of the billet directly determines the oxide size of the tungsten alloy wire or carbonized filament. If the wire oxide particles are coarser, it will be more difficult for the particles to migrate to the filament surface during the use of the magnetron 50, which will make the balance of rare earth element loss and replenishment on the filament surface easier to be broken, so that the electron emission of the magnetron 50 will be more unstable.

[0058] The adjustment of sintering process affects the speed of sintering neck growth and pore closure of tungsten blank. The sintering process provided can reduce the possibility of oxide particle aggregation, thereby reducing the oxide particle size of sintered blank. The specific principle of high temperature sintering process is explained as follows: Isostatic pressing green sheet is a dense accumulation of powder, and its porosity is about 35-45%. We can simply imagine these pores as multiple channels connected to each other, and oxide particles are evenly distributed on the inner surface of the cavity.

[0059] During the high-temperature sintering process, the tungsten particles bonded together form a "sintering neck". As the sintering temperature increases, the sintering neck continues to grow and blocks the channels connecting the holes, which produces isolated holes. These isolated holes will gradually become round, making the surface area inside the holes smaller, which in turn causes the originally similar-sized small oxide particles to gather together to form larger oxide particles. As the high-temperature sintering proceeds, the holes further shrink through diffusion, and the oxide particles distributed on the inner surface of the holes can only further gather to form one or several larger oxide particles.

[0060] Some of the smaller holes merge with adjacent large holes due to diffusion, or shrink before the connecting hole channels are closed. The oxide particles in these small holes will be pushed to the adjacent unclosed holes, making the unclosed holes contain more oxide than other places, which in turn causes the oxide particles to be larger than other places.

[0061] In summary, the above technical solution provided by the present application includes at least the following working principles or mechanisms and beneficial effects: (1) The grain width of the carbide layer 200 of the filament of the present application is controlled within a certain small size range, and the grain width of the carbide layer 200 is 1.0-15.0 μm. Compared with the thoriated tungsten filament, the grain size of the carbide layer 200 in the thorium-free filament of the present application is smaller than that of the thoriated tungsten filament, and the grain width is slightly narrower than that of the thoriated tungsten filament. The number of channels 210 in the carbide layer 200 of the present application is more. The organization of the carbide layer 200 at different positions in the filament provided by the present application has a layered block structure organization similar to that formed by the intersection of the first channel 211 and the second channel 212. The first channel 211 is vertically distributed with the edge of the filament, connecting the inside of the substrate 100 and the second channel 212 with the edge of the filament, which is conducive to the outward migration of rare earth atoms and timely replenishment of rare earth elements evaporated from the surface, thereby improving the stability of material emission.

[0062] (2) The initial recrystallization temperature of the filament material provided in the present application is between 48% FC (about 2070°C) and 56% FC (about 2290°C). Therefore, after carburization at a temperature of 2000-2100°C, the grains of the tungsten matrix 100 are relatively fine, and the brittleness of the carburized filament is less than that of the traditional thoriated tungsten filament material, which will reduce the wire breakage rate of customers during production and use.

[0063] (3) The processing performance of the filament material of the present application is better than that of the existing thoriated tungsten, the number of flaw detection cracks is less (when the filament wire diameter can reach 500 μm, the number of flaw detection cracks of the filament is less than 2 / 100 meters), the processing yield is high, the wound filament is not easy to break, the production efficiency is improved, and the wire material has fewer cracks, and the proportion of carbonized broken wires in the manufactured filament is also low.

[0064] In the filament material provided by the present application, the oxide of M (such as lanthanum oxide particles) has good plasticity. As the pressure processing proceeds, the oxide particles of M will become thin and long, and exist in a linear or quasi-linear shape; while the thorium oxide in the traditional thoriated tungsten material has poor plasticity. When the thoriated tungsten is processed to a certain extent, the thorium oxide will break. As the processing proceeds further, the thorium oxide will appear in the form of particle strings; the types of rare earth oxides added in the present application and the changes in morphological structure during the refinement process make the filament material have good processing performance. When preparing wire materials for winding filaments, the wire diameter of the filament material can be refined to 500μm or less, and the number of crack points detected by flaw detection can be effectively reduced, thereby improving the yield rate.

[0065] (4) The thickness of the carbonized layer 200 of the filament of the present application is preferably controlled within a range of 30-90 μm; The thickness of the conventional thoriated tungsten filament carbide layer 200 is generally 35-45μm; the thicker the carbide layer 200 is, the longer the service life of the heating device is; however, the conventional thoriated tungsten carbide layer 200 cannot be made thicker, because if the thickness is too large, the recrystallized grains of the tungsten matrix 100 after carbide will be greatly coarsened, making the carbide filament very brittle, and the broken filament ratio in the heating device during production and use will reach 10,000 to 30,000 ppm; At present, the thickness of the filament carbonization layer 200 of the embodiment of the present application is also basically 35-50 μm. Unlike the thoriated tungsten filament, the thickness of the carbonization layer of the present application can be thickened, which is conducive to increasing the life. The initial recrystallization temperature of the present application is relatively high, and the tungsten matrix 100 after carburization is still a fine-grained structure, and the filament breakage rate is very low. In this way, the present application can increase the thickness to increase the service life while ensuring that the filament breakage rate remains at a low level, making it possible to thicken the carbonization layer 200.

[0066] (5) The operating temperature of the heating device provided in the present application (i.e., the operating temperature of the filament) can be reduced from 1500-1600°C to 1100-1500°C, such as within the range of 1200-1300°C, and still maintain a good working condition; while the operating temperature of the traditional thoriated tungsten filament is 1600-1900°C. Therefore, the energy consumption and life of the filament provided in the present application and the heating device made therefrom will be improved.

[0067] In summary: the filament provided by the present application adds one or more oxides and carbides or carbon elements of M into the tungsten matrix 100. The combination of the oxides and carbides or carbon elements can improve the diffusion rate of the material in the matrix 100. Compared with the thorium tungsten filament, it can achieve the same or even higher electron emission capability at a lower operating voltage (excitation temperature). At the same time, the grains of the carbide layer 200 are controlled within a certain small size range, and the channel 210 formed on the surface of the carbide layer 200 of the filament is organized to form a layer block. The first channel 211 and the second channel 212 and the edge of the filament are distributed quasi-vertically, which is conducive to the outward migration of rare earth atoms and the timely replenishment of the rare earth elements evaporated from the surface, thereby improving the stability of the material emission. The tungsten alloy filament material provided by the present application replaces the existing thoriated tungsten filament cathode, and has a service life equivalent to or exceeding that of thoriated tungsten. The present application can significantly reduce the initial recrystallization temperature of the material, improve the processing performance of the material, reduce the electron work function of the material, and refine the microstructure grain of the filament by doping M oxide and carbide or carbon element into the tungsten matrix 100 powder. It can reduce the wire breakage rate to reduce the production and transportation costs, and effectively increase the service life of the filament, so that its service life reaches and far exceeds the service life of the existing thoriated tungsten filament.

[0068] The filament provided in the present application can obtain an extremely high recrystallization temperature, and can still obtain extremely fine grains at the same carburization temperature as thoriated tungsten. The material has excellent shock resistance, and can reduce the breakage and failure of the filament during production, transportation and use.

[0069] In addition, in view of the characteristics of the thorium-free tungsten carbide alloy filament (rare earth tungsten alloy material) provided by the present application, the present application provides the following magnetron 50 heating control method to adapt to the use of the thorium-free rare earth tungsten carbide alloy carbide filament type magnetron 50: The temperature required for the existing tungsten-thorium oxide filament to overcome the filament barrier and emit electrons is relatively high, and the thorium element has a high melting point, so the operating temperature of the cathode filament also needs to be relatively high. Compared with the tungsten-thorium oxide filament, the tungsten carbide alloy filament made of the above-mentioned thorium-free rare earth tungsten alloy material provided in this application has a relatively low temperature required to overcome the filament barrier and emit electrons, and the melting point and the suitable operating temperature of the filament are both low. If the heating control method of the tungsten-thorium oxide filament type magnetron 50 is applied to the heating operation of the filament material, the operating temperature of the cathode filament is too high, resulting in an increase in the oxide loss of the cathode filament, which has an adverse effect on the stable operation and service life of the magnetron 50.

[0070] Therefore, for the thorium-free rare earth tungsten carbide alloy carbide filament type magnetron 50 provided by the present application, the present application provides the following heating control method for the magnetron 50: 1. Magnetron 50 heating control method 1 1. Heating control method 1 like Figure 7 As shown, the heating system of the magnetron 50 includes a power supply 10 conversion circuit, the power supply 10 conversion circuit includes a transformer 20 for providing voltage to the anode and cathode filaments of the magnetron 50, the transformer 20 includes a high voltage winding 40 for generating a high voltage electric power output, and a low voltage winding 30 for generating a low voltage electric power output; the anode and cathode filaments of the magnetron 50 receive the high voltage electric power output and the low voltage electric power output respectively. The heating control method includes the following steps: the low voltage electric power output of the transformer 20 is preset to 1.4-2.0V, and after the power supply 10 is energized to the power supply 10 conversion circuit, the low voltage electric power output is controlled to run continuously at 1.4-2.0V until the power supply of the power supply 10 conversion circuit is disconnected.

[0071] 2. Specific operation process and working principle of heating control mode 1 During specific operation, compared with the conventional heating control method of the tungsten-thorium oxide filament type magnetron 50, the heating control method of the magnetron 50 provided in the present application directly reduces the low-voltage electric power output of the transformer 20 to 1.4-2.0V, and the power supply 10 conversion circuit of the magnetron 50 is powered on and operated at this output voltage until the power supply 10 is turned off.

[0072] The mechanism and effect of the control process design of the heating control method are as follows: since the tungsten alloy filament provided in the present application has good emission performance, the potential barrier that the material needs to overcome to emit electrons is relatively small, the melting point and the suitable working temperature of the filament are both low (the suitable working temperature is 1100°C to 1500°C), the low-voltage electric power output is designed to be reduced to 1.4 to 2.0V for continuous operation. During operation, the heat generated by the cathode filament to reach the required temperature is composed of three parts: the first is the heat generated by the cathode filament being energized; the second is the kinetic energy of some electrons emitted by the filament that is converted into heat during the flight of the electromagnetic field between the anode and cathode of the magnetron 50 and the return bombardment of the cathode filament surface; the third is the heat brought to the cathode filament by the high-temperature thermal radiation of the anode of the magnetron 50. At this output voltage, although the heat generated by the thorium-free rare earth tungsten alloy carbide filament when it is powered on is less than the heat generated by the thorium tungsten carbide filament at a voltage of 3.0 to 3.6V, the heat generated by the thorium-free rare earth tungsten alloy carbide filament when it is powered on supplements the heat generated by the electrons bombarding the cathode filament surface and the heat radiated to the cathode by the anode heat of the magnetron 50, which is sufficient to allow the cathode filament to reach a certain operating temperature, so that a large number of electrons can overcome the cathode filament material barrier and be emitted. Moreover, at this output voltage, it can also ensure that the actual operating temperature of the cathode filament is within the appropriate operating temperature range when the magnetron 50 is running, avoiding excessively high temperatures that cause a large loss of M metal elements in the filament during operation, thereby improving the stability and service life of the electron emission of the magnetron 50. In addition, compared with the existing magnetron 50 control scheme, this heating control method 1 maintains operation at a relatively low low-voltage power output, which can effectively reduce power consumption.

[0073] In the first heating control method, the design of the key parameter "1.4~2.0V" in "the low-voltage electric power output is controlled to run continuously at 1.4~2.0V until the power supply of the power supply 10 conversion circuit is disconnected": If the low-voltage electric power output value in the heating control mode 1 is controlled above 2.0 V, the actual operating temperature of the cathode filament is prone to get out of control and overheat, which is not conducive to the long-term stable operation and service life of the magnetron 50.

[0074] Since the cathode filament needs to be vibrated in the early stage of operation, if the low-voltage electric power output value in the heating control method 1 is controlled below 1.4V, the magnetron 50 will take longer to start or even fail to start. When the cathode filament is cold-started, there is no heat from the three heat sources of the filament, namely, electron back-bombardment and anode thermal radiation, and the heat only comes from the heat generated by the filament itself when it is powered on. The reason is that: when it is just started, the magnetron 50 has not yet started to vibrate, and no large amount of electrons are emitted, only very few electrons are emitted, so there is almost no electron back-bombardment (tungsten-thorium oxide filament or rare earth tungsten alloy filament is a hot cathode material, even if it does not reach the working temperature, there are very few electrons emitted, and only when it reaches the working temperature will a large amount of electrons be emitted to complete the start-up); when it is cold-started, the anode is also cold, so there is no thermal radiation. Therefore, if the initial low-voltage electric power output is lower than 1.4V, the heat generated by the cathode filament through its own power supply during initial startup will be too little, causing the cathode filament temperature to be too low. The electrons cannot overcome the potential barrier of the filament material and cannot be emitted in large quantities. The starting time of the magnetron 50 will be prolonged or even unable to start working.

[0075] In summary, the low-voltage power output is designed to be reduced to 1.4-2.0V for continuous operation. At this output voltage, the heat generated by the thorium-free rare earth tungsten carbide alloy carbide filament can be powered on to supplement the heat generated by the electrons bouncing back on the surface of the cathode filament and the heat radiated to the cathode by the anode heat of the magnetron 50, which is sufficient to enable a large number of electrons to overcome the material barrier and be emitted. In addition, at this output voltage, it can also ensure that the cathode filament of the magnetron 50 actually operates at an appropriate temperature, avoiding excessively high temperatures that cause a significant loss of the M metal element in the filament during operation, thereby improving the stability and service life of the electron emission of the magnetron 50.

[0076] 3. Verification of the effect of heating control method 1 In order to verify the effect of the above-mentioned heating control method 1, the following verification experiment is provided. The verification experiment process is: the low-voltage electric power output of the preset transformer 20 is A value V. After the power supply 10 supplies power to the power supply 10 conversion circuit, the low-voltage electric power output is controlled to continue to operate at the A value until the power supply of the power supply 10 conversion circuit is disconnected.

[0077] The specific low-voltage power output parameter A value of each verification experiment item and the actual measured temperature of the cathode filament (cathode coil) are shown in Table 1 below: Table 1 Corresponding cathode adjustment voltage A value (V) Cathode filament operating temperature (℃) Corresponding cathode adjustment voltage A value (V) Cathode filament operating temperature (℃) 3.4 1800 2.0 1400 3.2 1700 1.9 1350 3.0 1600 1.8 1300 2.8 1600 1.7 1250 2.6 1550 1.6 1200 2.4 1500 1.5 1150 2.2 1450 1.4 1100 4. Analysis of the operating effect of control method 1: It can be seen from the data in Table 1 that: when the low-voltage electric power output A value in the heating control mode 1 is controlled at 1.4-2.0V, the operating temperature of the cathode filament is controlled at 1100°C-1400°C, which is just within the suitable operating temperature range of 1100°C-1500°C of the above-mentioned thorium-free rare earth tungsten carbide alloy carbide filament. This can avoid excessively high temperatures that cause a significant loss of the M metal element in the filament during operation, thereby improving the stability and service life of the electron emission of the magnetron 50.

[0078] Moreover, the actual operating temperature measured at a voltage of 2.0V is 1400°C. When the upper limit of the voltage range defined in this application is increased by 0.2-0.4V (the A value is 2.2V and 2.4V), the actual operating temperature rises to a value close to the upper limit of the suitable temperature of 1500°C. Therefore, the voltage upper limit in the control method is designed to be 2.0V, which can leave a certain gap between the actual cathode filament operating temperature and the upper limit of the suitable filament operating temperature of 1500°C, thereby avoiding the filament heating up too fast and out of control at this voltage, resulting in overheating exceeding 1500°C. Such a design is safer and more secure.

[0079] When the low-voltage power output A value in the heating control mode 1 is controlled to be above 2.0V, the actual working temperature of the cathode filament is 1450°C, and most of the time it exceeds 1500°C. Too high a temperature is not conducive to the long-term stable operation and service of the magnetron 50. When the low-voltage power output A value in the heating control mode 1 is controlled to be below 1.4V, the heat generated by the thorium-free rare earth tungsten carbide filament through its own power supply at the initial startup is relatively small, and there is no heat generated by electrons bombarding the cathode filament surface and the heat supplemented by the anode heat radiation of the magnetron 50, which makes the cathode filament temperature low, and the electrons cannot overcome the filament material barrier, and cannot be emitted in large quantities, and the magnetron 50 cannot start to work.

[0080] 2. Heating control method 2 for magnetron 50 (voltage regulating module is relay 60), heating control method 3 for magnetron 50 (voltage regulating module includes temperature sensing component and voltage regulator 70) The above-mentioned heating control method 1 of the magnetron 50 uses a relatively low-voltage electric power output of 1.4 to 2.0V to start oscillation and maintain operation at this voltage. This control method can start oscillation and normal heating of the cathode filament of the magnetron 50, and ensure that the actual working temperature of the cathode filament is maintained at a suitable working temperature. However, as the operating time increases, the cathode filament of the magnetron 50 needs a certain amount of oscillation time in the later period of its service life (for example, after 1500 to 2000 hours of working time), which may cause the problem of delayed oscillation.

[0081] The present application provides the following magnetron 50 heating control method 2 and magnetron 50 heating control method 3, which can not only maintain the effect of the magnetron 50 heating control method 1, but also overcome the start-up delay problem of the magnetron 50 in the later period of its service life.

[0082] Heating control method 2 of magnetron 50 (voltage regulating module is relay 60) (1) Scheme of the second heating control method of the magnetron 50 like Figure 8 As shown, the heating system of the magnetron 50 includes a power supply 10 conversion circuit, a control module, and a relay 60 electrically connected to the control module; the power supply 10 conversion circuit includes a transformer 20 for providing voltage to the anode and cathode filaments of the magnetron 50, and the transformer 20 includes a high-voltage winding 40 for generating a high-voltage electric power output and a low-voltage winding 30 for generating a low-voltage electric power output; the anode and cathode filaments of the magnetron 50 receive the high-voltage electric power output and the low-voltage electric power output respectively; wherein the normally open contact of the relay 60 It is connected in series between the output end of the low-voltage winding 30 and the voltage input end of the cathode filament; the heating control method includes the following steps: the low-voltage electric power output is preset to 3.0-3.6V, and after the power supply 10 supplies power to the power supply 10 conversion circuit, the low-voltage electric power output is controlled to be 3.0-3.6V and continues to run for 5-10s; then the control module controls the relay 60 to disconnect, so as to disconnect the low-voltage winding 30 and reduce the low-voltage electric power output to 0V; and continues to run when the relay 60 is disconnected until the power supply of the power supply 10 conversion circuit is disconnected.

[0083] Optionally, the preset low-voltage electric power output is 3.3V. After the power supply 10 supplies power to the power supply conversion circuit, the low-voltage electric power output is controlled at 3.3V and continues to run for 5 to 10 seconds. After running continuously for 5 to 10 seconds, the control module controls the voltage regulation module to disconnect, so that the low-voltage electric power output is reduced to 0V, and continues to run until the power supply conversion circuit of the power supply 10 is disconnected.

[0084] (2) Specific operation process and working principle of heating control mode 2 During specific operation, the operation process of the second heating control mode of the magnetron 50 provided in the present application is: it first controls the initial low-voltage electric power output at 3.0~3.6V for 5~10s. The function of this stage is to allow the magnetron 50 to complete the oscillation and start normal operation. The voltage is subsequently reduced to 0V for operation (at this time, the low-voltage winding 30 is disconnected, and the high-voltage winding 40 is still operating normally) to reduce the heat generated by the cathode filament when it is powered on. At this stage, while ensuring the normal operation of the cathode filament (keeping the cathode filament at the operating temperature required to emit a large number of electrons), it can reduce the cathode filament from continuing to heat up by self-heating through power-on. The specific operating mechanism is: Since the cathode filament of the magnetron 50 has been heated to the required operating temperature during the 5-10s operation at the voltage of 3.0-3.6V in the early stage, the cathode filament electrons overcome the potential barrier of the filament material and are emitted in large quantities. The electrons emitted by the filament perform spoke flying motion in the electromagnetic field between the cathode and the anode of the magnetron 50, and the magnetron 50 completes the oscillation and starts to work normally. Therefore, after the subsequent operation is reduced to 0V to reduce the heat generated by the cathode itself through the power supply, when the low-voltage power output is 0V, the electrons emitted by the cathode filament perform spoke flying motion in the electromagnetic field between the cathode and the anode of the magnetron 50, but a small part of the electrons will bombard the cathode filament, and the kinetic energy of these electrons will be converted into heat, providing heat to the cathode; another part of the electrons will bombard the anode of the magnetron 50, and the kinetic energy of these electrons will be converted into heat, causing the anode temperature to rise, and then provide heat to the cathode through thermal radiation. Therefore, instead of heating the cathode filament by energizing it, the cathode filament can be provided with enough heat by using the heat radiation from the anode and the electrons bouncing back to the cathode filament to generate heat, so that the cathode filament can be kept at the operating temperature required to emit a large number of electrons.

[0085] In summary, due to the good emission performance of tungsten alloy filament, relatively small potential barrier and relatively low suitable working temperature, there is no need for low-voltage electrical power output. The cathode temperature can be guaranteed by the anode thermal radiation and the supplementary heat effect of the above-mentioned electron back bombardment, so that the filament is maintained at the operating temperature required to emit a large number of electrons, and the temperature is not allowed to continue to rise, thereby avoiding the increase in the loss of M metal elements (such as lanthanum, etc.) in the component due to the increase in temperature, which is beneficial to prolonging the service life of the heating device and improving its operating stability.

[0086] Among them, the design of the key parameters "3.0~3.6V" and "5~10s" in "controlling the initial low-voltage power output at 3.0~3.6V for 5~10s" is as follows: For the initial low voltage power output controlled at 3.0~3.6V: If the initial output voltage exceeds 3.6V, the cathode filament may work at a temperature exceeding 1800°C, and the number of electrons emitted by the cathode filament will increase significantly. First, the number of electrons bombarding the anode will also be large, and the anode temperature will increase significantly, even exceeding 500°C. The melting point of the silver-copper solder used for welding the components of the magnetron 50 is only about 600°C. The high anode temperature will cause the strength of the silver-copper soldering point to decrease, and the internal components of the magnetron 50 will be deformed, which will cause the magnetron 50 to fail to work. In addition, the number of electrons bombarding the cathode will also increase. Coupled with the voltage exceeding 3.6V, the heat generated by itself will also increase significantly. The operating temperature of the cathode filament will exceed 1800°C, and the rare earth elements will also be greatly consumed. This rare earth element will be greatly consumed in a short period of time and evaporate into the internal space of the magnetron 50, affecting the vacuum tube of the magnetron 50, causing the magnetron 50 to fail to work. In addition, the temperature rise rate of the cathode filament is too fast in the early stage, causing the cathode filament to lose control and overheat. Even if the relay 60 is quickly disconnected later, it is easy for the cathode filament temperature to fail to quickly cool down from the overheating after the relay 60 is disconnected, which will damage the service life of the heating device.

[0087] If the initial output voltage is lower than 3.0V, the magnetron 50 start-up time may be prolonged, exceeding the microwave oven manufacturer's requirement (<10s). The reason is that when the voltage is lower than 3.0V, the heat generated by the cathode filament per unit time becomes less, and a longer power-on time is required to generate enough heat to allow the cathode filament to reach the operating temperature where it can emit a large number of electrons, so the magnetron 50 start-up time will be prolonged.

[0088] For running time 5 to 10 seconds: If the continuous operation time is too short (less than 5s), the number of emitted electrons is insufficient, resulting in insufficient number of electrons bombarding the cathode and the anode. The heat brought by the thermal radiation of the anode and the electron bombardment of the cathode filament is insufficient to maintain the operating temperature required for the cathode filament to emit electrons; if the continuous operation time is too long (greater than 10s), during this stage, the cathode filament generates and accumulates too much heat through its own power-on heating, anode thermal radiation, and electron bombardment of the cathode filament. The actual operating temperature of the cathode filament is too high (similar to working at the operating temperature of a thorium tungsten filament), which will cause a large loss of rare earth elements, which is not conducive to the working life and stability of the cathode filament.

[0089] In summary, the design of the second heating control method "controlling the initial low-voltage electric power output at 3.0-3.6V for 5-10s" can not only ensure that the magnetron 50 can start working in a relatively short time (≤5s), but also control the temperature of the cathode filament at a suitable working temperature (1100-1400°C), which is beneficial to prolonging the service life of the heating device and improving its operating stability.

[0090] In summary, the present application provides the above-mentioned heating control method 2, and its action mechanism and effect are: On the one hand, since the tungsten alloy filament targeted by the present application has good emission performance, a relatively small potential barrier, and a relatively low suitable operating temperature, after the initial low-voltage electric power output is controlled at 3.0 to 3.6V and operates for 5 to 10 seconds, the cathode filament can be maintained at the operating temperature required to emit a large number of electrons by relying solely on the anode thermal radiation and the supplementary heat effect of the above-mentioned electron back bombardment, and the cathode filament temperature will not continue to rise, and the cathode filament does not need to be energized to generate heat.

[0091] Therefore, when the magnetron 50 heating control method 2 of the present application is used, the magnetron 50 is first designed to start oscillating at a higher initial low-voltage electric power output voltage, start emitting electrons, and then disconnect the cathode filament circuit, relying solely on electron back bombardment and anode radiation to maintain the cathode filament temperature, which can reduce energy consumption.

[0092] On the other hand, through the above-mentioned second heating device control method, after the magnetron 50 completes the oscillation and works normally, the voltage of the cathode low-voltage winding 30 is disconnected to reduce the heat generated by the cathode filament. The cathode temperature can be guaranteed by the anode heat radiation and the supplementary heat effect of the above-mentioned electron back bombardment, so that the filament is kept at the operating temperature required for emitting a large number of electrons, and the filament temperature is not allowed to continue to rise, thereby avoiding the increase in the loss of M metal elements (such as lanthanum, etc.) in the components due to the increase in temperature, which is beneficial to prolonging the service life of the heating device and improving its operating stability.

[0093] (3) Verification of the effect of heating control method 2 In order to verify the effect of the above-mentioned heating control method 2, the following verification experiment is provided. The verification experiment process is as follows: the low-voltage electric power output is preset to 3.3V. After the power supply 10 supplies power to the power supply 10 conversion circuit, the low-voltage electric power output is controlled to 3.3V and continues to run for 7s; then the control module controls the relay 60 to disconnect, so that the low-voltage electric power output is reduced to 0V; and the operation continues when the relay 60 is disconnected until the power supply of the power supply 10 conversion circuit is disconnected.

[0094] When the low voltage power output is reduced to 0V, the actual working temperature of the cathode filament is measured to be about 1200-1400℃. At this stage, the microwave input current obtained by the user is >4.5A, which means that the magnetron 50 has started to oscillate normally (if it does not start to oscillate normally, the microwave input current is <4.0A); through the detection of the special electron emission capability detection equipment of the microwave oven, it can be known that the anode current of the magnetron 50 is >250mA, which means that the magnetron 50 starts to oscillate normally and starts to emit electrons.

[0095] 2. Magnetron 50 heating control method three (voltage regulating module includes temperature sensing component and voltage regulator 70) (1) Magnetron 50 heating control method 3 solution like Fig. 9 As shown, the heating system of the magnetron 50 includes a power supply 10 conversion circuit, a control module (not shown in the figure), a temperature sensing component (not shown in the figure) for sensing the temperature of the outer surface of the magnetron 50, and a voltage regulator 70; the power supply 10 conversion circuit includes a transformer 20 for providing voltage to the anode and cathode filaments of the magnetron 50, and the transformer 20 includes a high-voltage winding 40 for generating a high-voltage electric power output and a low-voltage winding 30 for generating a low-voltage electric power output; the anode and cathode filaments of the magnetron 50 receive the high-voltage electric power output and the low-voltage electric power output respectively; wherein the voltage regulator 70 is connected in series to the output end of the low-voltage winding 30 and the cathode filament. The voltage input terminal of the pole filament is used to increase or decrease the low-voltage electric power output; the temperature sensing component and the voltage regulator 70 are electrically connected to the control module; the heating control method includes the following steps: the low-voltage electric power output is preset to 3.0-3.6V, and after the power supply 10 supplies power to the power supply 10 conversion circuit, the low-voltage electric power output is controlled at 3.0-3.6V and continues to run for 5-10s; then the control module controls the voltage regulator 70 to reduce the low-voltage electric power output to 1.4-2.0V for continuous operation, and during the operation, the low-voltage electric power output is adjusted by the voltage regulator 70 to control the temperature sensed by the temperature sensing component within a predetermined temperature range.

[0096] In specific implementation, the temperature sensing component senses the temperature information of the outer surface of the magnetron 50, and the temperature information is transmitted to the control module for processing through a signal, and then the control module controls the voltage regulator 70 to adjust the low-voltage electric power output so that the outer surface temperature of the magnetron 50 is controlled within a predetermined temperature range. The specific signal transmission process is: the temperature sensing component (temperature sensor) outputs a signal S1 into the control module (PLC controller), and the control module outputs an analog signal P1 through calculation inside, and the analog signal P1 is connected to the analog signal input terminals CL and COM of the voltage regulator 70.

[0097] Optionally, the preset low-voltage electric power output is 3.3V. After the power supply 10 supplies power to the power supply conversion circuit, the low-voltage electric power output is controlled at 3.3V and continues to run for 5 to 10 seconds. After running for 5 to 10 seconds, the control module controls the voltage regulator 70 to reduce the low-voltage electric power output to 1.6 to 2.0V for continuous operation. During the operation, the low-voltage electric power output is adjusted by the voltage regulator 70 so that the outer surface temperature of the magnetron 50 is controlled within a predetermined temperature range.

[0098] (2) Specific operation process and working principle of heating control mode 3 During specific operation, the operation process of the third heating control mode of the magnetron 50 provided in the present application is: it first controls the initial low-voltage electric power output at 3.0~3.6V for 5~10s. The function of this stage allows the magnetron 50 to complete the oscillation and work. In this stage, the cathode filament electrons overcome the potential barrier of the filament material and are emitted in large quantities. The cathode filament of the magnetron 50 is heated to the required operating temperature (keeping the cathode filament at the required operating temperature for emitting a large number of electrons) by means of energizing the cathode filament, thermal radiation from the anode, electron back bombardment, etc.; and then continues to operate by controlling the initial low-voltage electric power output at 1.4~2.0V.

[0099] Since the surface temperature of the anode tube of the magnetron 50 (i.e., the outer surface temperature of the magnetron 50) is related to the actual working temperature of the cathode filament. During the actual operation of the magnetron 50, the size of the low-voltage electric power output affects the actual working temperature of the cathode filament, thereby affecting the surface temperature of the anode tube of the magnetron 50. Therefore, during the continuous operation of 1.4-2.0V, the temperature information of the outer surface of the magnetron 50 is sensed by the temperature sensing component, and the temperature information is transmitted to the control module for processing through a signal. Then, the control module controls the voltage regulator 70 to adjust the low-voltage electric power output. This control principle controls the outer surface temperature of the magnetron 50 within a predetermined temperature range, and the actual working temperature of the cathode filament can be controlled within a certain range to avoid over-temperature runaway and damage to its service life. The specific operating mechanism is: Since the cathode filament of the magnetron 50 has been heated to the required operating temperature after running at a voltage of 3.0 to 3.6 V for 5 to 10 seconds in the early stage, the subsequent operation at a voltage of 1.4 to 2.0 V can reduce the self-heating of the cathode through power-on. Under this low voltage of 1.4 to 2.0 V, the temperature of the cathode filament is increased by powering the cathode filament, radiating heat from the anode, and electrons bombarding the cathode filament to generate heat, so that the cathode filament is heated and maintained at the required temperature (the cathode filament is maintained at the operating temperature required to emit a large number of electrons).

[0100] Among them, since the later stage is operated at a relatively low low-voltage power output of 1.4 to 2.0V, compared with the method of maintaining the temperature of the cathode filament only by the heat radiation of the anode and the electrons bombarding the cathode filament to generate heat, the heat generated by the cathode filament powering on is supplemented to make the temperature of the cathode filament rise faster. In order to avoid the cathode filament from losing control and overheating during this period, a flexible over-temperature adjustment mechanism is designed, in which the temperature sensing component senses and the voltage regulator 70 adjusts the low-voltage power output through the voltage regulator 70, and the outer surface temperature of the magnetron 50 is controlled within a predetermined temperature range, thereby controlling the actual working temperature of the cathode filament within a certain range, so that it operates at a suitable working temperature (1100 to 1500°C). For example, the outer surface temperature of the magnetron 50 (i.e., the surface temperature of the anode tube of the magnetron 50) is controlled within the range of 300 to 350°C, and the actual working temperature of the cathode filament is within the range of 1100 to 1400°C.

[0101] Among them, the design of the key parameters "3.0~3.6V" and "5~10s" in "controlling the initial low-voltage power output at 3.0~3.6V for 5~10s" is as follows: For the initial low voltage power output controlled at 3.0~3.6V: If the initial output voltage exceeds 3.6V, the cathode filament may work at a temperature exceeding 1800°C, and the number of electrons emitted by the cathode filament will increase significantly. First, the number of electrons bombarding the anode will also be large, and the anode temperature will increase significantly, even exceeding 500°C. The melting point of the silver-copper solder used for welding the components of the magnetron 50 is only about 600°C. The high anode temperature will cause the strength of the silver-copper soldering point to decrease, causing the internal components of the magnetron 50 to deform, and further causing the magnetron 50 to fail to work. In addition, the number of electrons bombarding the cathode will also increase. Coupled with the voltage exceeding 3.6V, the heat generated by itself will also increase significantly. The operating temperature of the cathode filament will exceed 1800°C, and the rare earth elements will also be greatly consumed. This rare earth element will be greatly consumed in a short period of time and evaporate into the internal space of the magnetron 50, affecting the vacuum tube of the magnetron 50, causing the magnetron 50 to fail to work. In addition, the temperature rise rate of the cathode filament is too fast in the early stage, causing the cathode filament to lose control and overheat. Even if the relay 60 is quickly disconnected later, it is easy for the cathode filament temperature to fail to quickly cool down from the overheating after the relay 60 is disconnected, which will damage the service life of the heating device.

[0102] If the initial output voltage is lower than 3.0V, the magnetron 50 start-up time may be prolonged, exceeding the microwave oven manufacturer's requirement (<10s). The reason is that when the voltage is lower than 3.0V, the heat generated by the cathode filament per unit time becomes less, and a longer power-on time is required to generate enough heat to allow the cathode filament to reach the operating temperature where it can emit a large number of electrons, so the magnetron 50 start-up time will be prolonged.

[0103] For running time 5 to 10 seconds: If the continuous operation time is too short (less than 5s), the number of emitted electrons is insufficient, resulting in insufficient number of electrons bombarding the cathode and the anode. The heat brought by the thermal radiation of the anode and the electron bombardment of the cathode filament is insufficient to maintain the operating temperature required for the cathode filament to emit electrons; if the continuous operation time is too long (greater than 10s), during this stage, the cathode filament generates and accumulates too much heat through its own power-on heating, anode thermal radiation, and electron bombardment of the cathode filament. The actual operating temperature of the cathode filament is too high (similar to working at the operating temperature of a thorium tungsten filament), which will cause a large loss of rare earth elements, which is not conducive to the working life and stability of the cathode filament.

[0104] In summary, the design of the third heating control method "controlling the initial low-voltage electric power output at 3.0-3.6V for 5-10s" can not only ensure that the magnetron 50 can start working in a relatively short time (≤5s), but also control the temperature of the cathode filament at a suitable working temperature (1100-1400°C), which is beneficial to prolonging the service life of the heating device and improving its operating stability.

[0105] Among them, regarding the design of the key parameter "1.4~2.0V" in "the control module controls the voltage regulator 70 to reduce the low voltage power output to 1.4~2.0V for continuous operation": From the data in Table 1 above, it can be seen that the low-voltage power output is designed to run continuously at 1.4-2.0V. When running for a long time at this output voltage, the actual working temperature of the cathode filament of the magnetron 50 is at a suitable temperature of 1100-1400°C. Although the early start-up of the heating control method 3 will cause a certain rise in the cathode filament temperature, so that when the heating control method 3 is running at a voltage of 1.4-2.0V, the working temperature of the cathode filament is inconsistent with that in Table 1 (may be too high), but when it is designed to run at a voltage of 1.4-2.0V, with the flexible over-temperature adjustment mechanism of the temperature sensing component induction and the voltage regulator 70 adjustment of this control method, the actual working temperature of the cathode filament can be quickly controlled within a suitable range. It is easier to control when running at a voltage of 1.4-2.0V, effectively avoiding excessive temperature that causes a large loss of M metal elements in the filament during operation, thereby improving the stability and service life of the electron emission of the magnetron 50.

[0106] In summary, the present application provides the above-mentioned heating control method 3, and its action mechanism and effect are: On the one hand, since the tungsten alloy filament targeted by the present application has good emission performance, a relatively small potential barrier, and a relatively low suitable operating temperature, after the initial low-voltage electric power output is controlled at 3.0-3.6V and operates for 5-10s, the initial low-voltage electric power output does not need to continue to operate at a high voltage of 3.0-3.6V. The cathode temperature can be ensured by the cathode filament power-on, anode thermal radiation, and the supplementary heat effect of the above-mentioned electron back bombardment under the condition of the initial low-voltage electric power output of 1.4-2.0V, so that the cathode filament can be maintained at the operating temperature required for emitting a large number of electrons, and the temperature control mechanism of the temperature sensing component-control module-voltage regulator 70 is operated to prevent the temperature of the cathode filament from continuing to rise. Therefore, when the magnetron 50 heating control mode 3 of the present application is used for operation, the magnetron 50 is first designed to complete the oscillation and start normal operation under a higher initial low-voltage electric power output, and then maintain low-voltage operation. The cathode filament is energized, electron back bombardment and anode radiation under the condition of an initial low-voltage electric power output of 1.4 to 2.0 V to allow the cathode filament to reach the operating temperature required for emitting a large number of electrons. This can not only reduce energy consumption, but also prevent the cathode filament from overheating through a temperature control mechanism.

[0107] On the other hand, since the melting point of the M metal element in the component of the tungsten alloy filament material targeted by the heating control method is relatively low (for example, lanthanum or some rare earth elements have a relatively low melting point), the working temperature of the filament also needs to be relatively low, otherwise the loss during operation will increase significantly, affecting the stability of electron emission. Through the above-mentioned heating device control method three, after the magnetron 50 completes the oscillation and works normally, the cathode low-voltage winding 30 voltage is disconnected to reduce the heat generated by the cathode filament when it is powered on, so as to avoid the continuous and rapid increase in the actual working temperature of the cathode filament under the high voltage state. Subsequently, the cathode filament temperature is maintained by means of powering on the cathode filament, electron back bombardment and anode radiation under the initial low-voltage power output of 1.4 to 2.0V, and at the same time, the flexible over-temperature adjustment mechanism of temperature sensing component induction and voltage regulator 70 adjustment is used to control the outer surface temperature of the magnetron 50 within a predetermined temperature range, so as to control the actual working temperature of the cathode filament within a certain range, avoid the increase in the loss of the M metal element (such as lanthanum, etc.) in the component due to the temperature increase, and is conducive to improving the service life and operation stability of the magnetron 50.

[0108] In addition, for the control mechanism of "adjusting the low-voltage electric power output through the voltage regulator 70 during operation so that the temperature sensed by the temperature sensing component is controlled within a predetermined temperature range", the present application also provides the following optional control mechanism operation examples.

[0109] Optionally, the following regulation process mechanism of the voltage regulator 70 for regulating the low-voltage electric power output is provided: when the temperature sensed by the temperature sensing component is greater than or equal to 350°C, the control module controls the voltage regulator 70, and the voltage regulator 70 adjusts the low-voltage electric power output to 1.4V for operation. When the temperature sensed by the temperature sensing component is greater than or equal to 355°C, the low-voltage electric power output is reduced to 1.2V for operation. When the temperature sensed by the temperature sensing component is greater than or equal to 380°C, the low-voltage electric power output is reduced to 0V for operation. Similarly, the higher the temperature, the greater the decrease in the low-voltage electric power output and the smaller the voltage value. When the temperature sensed by the temperature sensing component is less than or equal to 330°C, the low-voltage electric power output is adjusted back to 1.4~2.0V for operation.

[0110] Specifically, when the control mechanism is in operation, when the magnetron 50 is started, the low-voltage electric power output is set to a low voltage of 3.0 to 3.6V. After working at this voltage for 5 to 10 seconds, it is automatically adjusted to a low voltage of 1.4 to 2.0V through the control module, and then the voltage is maintained at 1.4 to 2.0V. At this time, during the operation under the voltage of 1.4 to 2.0V, once an over-temperature out-of-control situation occurs, the over-temperature control mechanism is started according to the above-mentioned control process mechanism, and the voltage is immediately reduced. The higher the actual working temperature of the cathode filament exceeds, the greater the voltage drop is, thereby reducing the over-temperature duration of the filament. Similarly, at this time, during this operation, once the temperature is low, there is also a low-temperature callback control mechanism: when the temperature sensed by the temperature sensing component is less than or equal to 330°C, the low-voltage electric power output callback is increased to 1.4 to 2.0V to operate, so that the actual working temperature of the cathode filament is at a suitable temperature for a long time.

[0111] In addition, the low-temperature voltage callback regulation mechanism can be further refined. The lower the actual operating temperature of the cathode filament, the greater the voltage callback increase. Optionally, when the temperature sensed by the temperature sensing component is less than or equal to 330°C, the low-voltage electric power output is increased to 1.6V for operation, when the temperature sensed by the temperature sensing component is less than or equal to 320°C, the low-voltage electric power output is increased to 1.7V for operation, and when the temperature sensed by the temperature sensing component is less than or equal to 310°C, the low-voltage electric power output is increased to 1.8V for operation. By analogy, the lower the temperature, the greater the callback increase of the low-voltage electric power output.

[0112] According to the above control scheme, different voltage transformation amplitudes and voltage values ​​are adjusted according to different actual working temperatures. Such step-by-step control enables the actual temperature of the cathode filament to be quickly adjusted to the required temperature, thereby further improving the temperature stability of the heating operation of the magnetron 50. Specifically, the above-mentioned step-by-step over-temperature or over-cooling control process mechanism can be further refined, as shown in Table 2 below: Table 2

[0113] The operation process of Detailed Explanation Table 2 is as follows: the low-voltage electric power output is reduced to 1.4-2.0V for continuous operation. During the operation, the low-voltage electric power output is adjusted by the voltage regulator 70 so that the temperature sensed by the temperature sensing component is controlled within a predetermined temperature range. The specific control mechanism is as follows: when the temperature sensed by the temperature sensing component is greater than or equal to the D value, the voltage regulator 70 adjusts the low-voltage electric power output to reduce to the E value for operation; when the temperature sensed by the temperature sensing component is less than or equal to the B value, the voltage regulator 70 adjusts the low-voltage electric power output to return to the C value for operation.

[0114] It should be noted that the optional low-temperature voltage callback control mechanism (low-temperature-voltage callback control mechanism) in Table 2 is only an example that can be implemented. In fact, for the low-temperature voltage callback control process: due to the above-mentioned electron back bombardment and anode thermal radiation to supplement the heat of the cathode filament, the magnetron 50 still works normally after the low-voltage power output is adjusted to 1.4-2.0V, and the lower the temperature of the outer surface of the anode tube, the more beneficial it is to the heating component. Therefore, even if the temperature of the outer surface of the anode tube decreases under the operation of 1.4-2.0V, it is feasible that the voltage no longer rises and falls back when the magnetron 50 can work normally. At this time, the magnetron 50 can still operate normally (similar to the control method 2 scheme of this application). That is, in the specific implementation process, when the temperature sensed by the temperature sensing component is lower than a certain limit value (for example, 330°C), the voltage is adjusted back to 1.4V-2.0V for continuous operation. Even if the temperature continues to drop, there is no need to further increase and fall back the voltage according to the "low-temperature-voltage callback control" scheme in Table 2.

[0115] Optionally, the temperature sensing component is a temperature sensor, and the control module is a PLC controller. Among them, the PLC controller, the temperature sensor, and the voltage regulator 70 are all existing devices, and those skilled in the art can make adaptive selections. The working mechanism of the PLC controller receiving the temperature sensor signal and feedback controlling the operation of the voltage regulator 70 is also an existing technology, which will not be repeated here.

[0116] It should be noted that: In this article, “~” is used to indicate a numerical range, and the range indicated by this expression includes two endpoint values.

[0117] In addition, unless otherwise specified, the raw materials used may also be conventional commercial products in the art, or may be prepared by conventional methods in the art. In addition, those skilled in the art should understand that, although there are many problems in the prior art, each embodiment or technical solution of the present application may be improved in only one or several aspects, without having to solve all the technical problems listed in the prior art or in the background technology at the same time. Those skilled in the art should understand that the content not mentioned in a claim should not be used as a limitation on the claim. Although terms such as carbonized layer, matrix, channel, PLC controller, temperature sensor, voltage regulator, etc. are used more in this article, the possibility of using other terms is not excluded. The use of these terms is only to more conveniently describe and explain the essence of the present application; interpreting them as any additional limitation is contrary to the spirit of the present application. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A magnetron heating control method, characterized in that: The heating system of the magnetron includes a power conversion circuit; the power conversion circuit includes a transformer for providing voltage to the anode and cathode filament of the magnetron, the transformer includes a high voltage winding for generating a high voltage electric power output and a low voltage winding for generating a low voltage electric power output; the anode and cathode filament of the magnetron receive the high voltage electric power output and the low voltage electric power output respectively; The heating control method comprises the following steps: The low-voltage electric power output of the transformer is preset to be 1.4-2.0V. After the power supply is energized to the power conversion circuit, the low-voltage electric power output is controlled to run continuously at 1.4-2.0V until the power supply of the power conversion circuit is disconnected.

2. The magnetron heating control method according to claim 1, characterized in that: The low-voltage electric power output of the transformer is preset to be 1.6-2.0V. After the power supply is energized to the power conversion circuit, the low-voltage electric power output is controlled to run continuously at 1.6-2.0V until the power supply of the power conversion circuit is disconnected.

3. A magnetron heating control method, characterized in that: The heating system of the magnetron includes a power conversion circuit, a control module, and a voltage regulating module electrically connected to the control module; the power conversion circuit includes a transformer for providing voltage to the anode and cathode filament of the magnetron, and the transformer includes a high-voltage winding for generating a high-voltage electric power output and a low-voltage winding for generating a low-voltage electric power output; the anode and cathode filament of the magnetron receive the high-voltage electric power output and the low-voltage electric power output respectively; Wherein, the voltage regulating module is connected in series between the output end of the low voltage winding and the voltage input end of the cathode filament to regulate the output of the low voltage electric power; The heating control method comprises the following steps: The low voltage electric power output is preset to be 3.0 to 3.6 V. After the power supply is powered on to the power conversion circuit, the low voltage electric power output is controlled to be 3.0 to 3.6 V and continuously operates for 5 to 10 seconds. After running continuously for 5 to 10 seconds, the control module controls the voltage regulating module to disconnect so that the low-voltage electric power output is reduced to 0V, and continues to run until the power supply of the power conversion circuit is disconnected; or, after running continuously for 5 to 10 seconds, the control module controls the voltage regulating module to reduce the low-voltage electric power output to 1.4 to 2.0V and continue to run, and during the operation, the low-voltage electric power output is adjusted by the voltage regulating module so that the outer surface temperature of the magnetron is controlled within a predetermined temperature range.

4. The magnetron heating control method according to claim 3, characterized in that: When the voltage regulating module is a relay, the normally open contact of the relay is connected in series between the output end of the low voltage winding and the voltage input end of the cathode filament; The heating control method includes the following steps: the low-voltage electric power output is preset to 3.0-3.6V, and after the power supply is energized to the power conversion circuit, the low-voltage electric power output is controlled to run continuously at 3.0-3.6V for 5-10s; then the control module controls the relay to disconnect, so that the low-voltage electric power output is reduced to 0V, and continues to run in the relay disconnected state until the power supply of the power conversion circuit is disconnected.

5. The magnetron heating control method according to claim 3, characterized in that: When the voltage regulating module includes a temperature sensing component and a voltage regulator for sensing the temperature of the outer surface of the magnetron, the voltage regulator is connected in series between the output end of the low-voltage winding and the voltage input end of the cathode filament, and is used to increase or decrease the low-voltage electric power output; the temperature sensing component and the voltage regulator are electrically connected to the control module; The heating control method comprises the following steps: The low-voltage electric power output is preset to 3.0-3.6V. After the power supply is energized to the power conversion circuit, the low-voltage electric power output is controlled at 3.0-3.6V for continuous operation for 5-10s; then the control module controls the voltage regulator to reduce the low-voltage electric power output to 1.4-2.0V for continuous operation. During the operation, the low-voltage electric power output is adjusted by the voltage regulator so that the temperature sensed by the temperature sensing component is controlled within a predetermined temperature range.

6. The magnetron heating control method according to claim 5, characterized in that: The process of regulating the low voltage electric power output through the voltage regulator during operation is: When the temperature sensed by the temperature sensing component is greater than or equal to 350° C., the control module controls the voltage regulator, and the voltage regulator adjusts the low-voltage electric power output to reduce it to 1.4V for operation; When the temperature sensed by the temperature sensing component is greater than or equal to 355°C, the low voltage electric power output is reduced to 1.2V for operation; When the temperature sensed by the temperature sensing component is greater than or equal to 380°C, the low voltage electric power output is reduced to 0V for operation; When the temperature sensed by the temperature sensing component is less than or equal to 330° C., the low voltage electric power output is increased to 1.4-2.0V for operation.

7. The magnetron heating control method according to claim 3, characterized in that: The heating control method comprises the following steps: The low voltage electric power output is preset to 3.3V. After the power supply is powered on to the power conversion circuit, the low voltage electric power output is controlled to run continuously at 3.3V for 5 to 10 seconds. After running continuously for 5 to 10 seconds, the control module controls the voltage regulating module to disconnect so that the low-voltage electric power output is reduced to 0V, and continues to run until the power supply of the power conversion circuit is disconnected; or, after running continuously for 5 to 10 seconds, the control module controls the voltage regulating module to reduce the low-voltage electric power output to 1.6 to 2.0V and continues to run, and during the operation, the low-voltage electric power output is adjusted by the voltage regulating module so that the outer surface temperature of the magnetron is controlled within a predetermined temperature range.

8. The magnetron heating control method according to any one of claims 1 to 7, characterized in that: The operating temperature of the cathode filament in the magnetron is 1100°C to 1500°C; The components of the cathode filament include M element; the M element is selected from one or more combinations of La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, and Zr.

9. The magnetron heating control method according to claim 8, characterized in that: The cathode filament in the magnetron comprises a substrate and a carbonized layer attached to the outer surface of the substrate; wherein the grain width of the carbonized layer is between 1.0 μm and 15.0 μm; The components of the substrate and the carbide layer both contain tungsten, carbon, oxygen and M; the M element is selected from one or more combinations of La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf and Zr; Wherein, the components of the tungsten carbide alloy filament do not contain thorium element.

10. The magnetron heating control method according to claim 9, characterized in that: A plurality of second channels are distributed on the carbonized layer, so that a layered structure stacked radially is formed on the cross section of the filament; a plurality of first channels are distributed on the carbonized layer, and at least part of the first channels and the second channels are cross-arranged, so that the layered structure is divided into a plurality of block structures.

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