A microwave-heated coaxial resonator printhead and its assembly and testing method

Abstract

This invention provides a microwave-heated coaxial resonator printhead and its assembly and testing method, comprising an outer conductor microwave shielding shell with a microwave source input port conductively disposed on its outer wall, an outer conductor microwave shielding block welded to the top of the outer conductor microwave shielding shell, a coaxial inner conductor fixed inside the outer conductor microwave shielding block, the coaxial inner conductor being disposed within the outer conductor microwave shielding shell and forming a coaxial resonant cavity with the outer conductor microwave shielding shell, a choke groove shell welded to the bottom of the outer conductor microwave shielding shell, a flange mounted at the bottom of the choke groove shell, a quartz tube passing through the coaxial inner conductor and extending to the flange outlet end, the length of the coaxial inner conductor within the outer conductor microwave shielding shell being less than the height of the coaxial resonant cavity, so that part of the quartz tube is exposed within the coaxial resonant cavity. By applying microwaves, conductive composite thermoplastic filaments can be rapidly heated in a short time, greatly improving the heating rate compared to traditional resistance heating.

Description

Technical Field

[0001] This invention relates to a microwave-heated coaxial resonator printhead and its assembly and testing method, which is applied in the field of 3D printing. Background Technology

[0002] 3D printing technology, also known as additive manufacturing technology, is based on modern digital and computer technologies. As a result, 3D printing technology has become increasingly mature. 3D printers melt and heat conductive filaments to print workpiece models layer by layer. They can print various complex three-dimensional models. 3D printing technology can solve the problems of complex processing in traditional manufacturing, reduce the process steps of complex traditional manufacturing, save on model manufacturing costs, enable rapid prototyping, greatly shorten the production cycle, improve production efficiency, and reduce waste of raw materials.

[0003] Existing 3D printers use resistance heating to heat the filament. The heating rate of traditional 3D printer filaments is only 2℃ / s, which is slow, has a long heating time, and is uneven. Therefore, this invention designs a microwave-heated coaxial resonator print head and its assembly and testing method. Summary of the Invention

[0004] This invention provides a microwave-heated coaxial resonator printhead and its assembly and testing method, which can effectively solve the above-mentioned problems.

[0005] This invention is implemented as follows:

[0006] A microwave-heated coaxial resonator printhead, comprising:

[0007] An outer conductor microwave shielding shell has a microwave source input port conductively disposed on its outer wall. An outer conductor microwave shielding block is welded to the top of the outer conductor microwave shielding shell. A coaxial inner conductor is fixed inside the outer conductor microwave shielding block. The coaxial inner conductor is disposed inside the outer conductor microwave shielding shell and forms a coaxial resonant cavity with the outer conductor microwave shielding shell. A choke groove shell is welded to the bottom of the outer conductor microwave shielding shell. A flange is installed at the bottom of the choke groove shell. A quartz tube is inserted inside the coaxial inner conductor and extends to the outlet end of the flange. The length of the coaxial inner conductor disposed inside the outer conductor microwave shielding shell is less than the height of the coaxial resonant cavity, so that part of the quartz tube is exposed inside the coaxial resonant cavity.

[0008] As a further improvement, the bottom of the choke housing is provided with a connecting groove, the flange includes a mounting part and a connecting part integrally formed with the mounting part, the mounting part is installed on the bottom of the choke housing by a first bolt, the connecting part is located in the connecting groove, and a choke cavity is provided between the connecting groove and the connecting part, and a polytetrafluoroethylene ring is installed in the choke cavity.

[0009] As a further improvement, the outer diameter of the coaxial inner conductor is defined as... The inner diameter of the outer conductor microwave shielding shell is Then there is

[0010] , <

[0011] in The relative permittivity of the filler in the coaxial line. Characteristic impedance, This is the minimum operating wavelength.

[0012] As a further improvement, the outer wall of the coaxial inner conductor is provided with a plurality of first annular grooves, and the inner wall of the outer conductor microwave shielding shell is provided with a plurality of second annular grooves corresponding to the first annular grooves. The radius of the first annular grooves is defined as... The radius of the second annular groove is Then there is =( - )-( - =0.25~0.3mm.

[0013] As a further improvement, the offset of the first and second annular grooves relative to the axial direction of the coaxial resonant cavity is defined as Δl, then Δl = 0~0.2mm.

[0014] As a further improvement, the outer conductor microwave shielding block includes a first mounting housing and a second mounting housing. The bottom of the first mounting housing is welded to the top of the outer conductor microwave shielding housing. The bottom of the first mounting housing has a first through hole adapted to the coaxial inner conductor. An annular mounting groove is provided on the outer side of the first mounting housing away from the outer conductor microwave shielding housing. An inner conductor mounting groove, coaxial with the annular mounting groove, is provided on the inner side of the first mounting housing away from the outer conductor microwave shielding housing. A bolt mounting block is provided on the sidewall of the inner conductor mounting groove. A bolt fixing hole penetrating the annular mounting groove and the bolt mounting block is provided on the sidewall of the first mounting housing. An mounting block adapted to the inner conductor mounting groove is provided on the outer side wall of the inner conductor. The mounting block is located in the inner conductor mounting groove. The second mounting housing is provided with a housing side wall corresponding to the annular mounting groove. The housing side wall is provided with bolt mounting holes corresponding to the bolt fixing groove. An abutment block adapted to the inner conductor mounting groove is provided inside the housing side wall. The top of the second mounting housing is provided with a second through hole adapted to the coaxial inner conductor. When the housing side wall is inserted into the annular mounting groove, the bolt mounting holes are aligned with the bolt fixing holes and are locked in place with a second bolt. The abutment block abuts against the mounting block, so that the coaxial inner conductor is securely mounted on the outer conductor microwave shielding block.

[0015] As a further improvement, a polytetrafluoroethylene block is provided at the bottom of the abutment block.

[0016] An assembly and testing method for a microwave-heated coaxial resonator printhead includes the following steps:

[0017] S10: The outer conductor microwave shielding shell, the coaxial inner conductor, the first mounting shell, the second mounting shell, and the outer conductor microwave shielding shell are manufactured by machining, and the microwave source input port is installed on the side wall of the outer conductor microwave shielding shell;

[0018] S20: Weld the first mounting housing and the choke slot housing to both ends of the outer conductor microwave shielding housing:

[0019] S30: Place the polytetrafluoroethylene ring in the connecting groove, then place the flange in the connecting groove, and secure the flange by tightening the first bolt;

[0020] S40: Place the quartz tube inside the coaxial inner conductor, and place the coaxial inner conductor inside the outer conductor microwave shielding shell, then move the quartz tube to the flange outlet end;

[0021] S50: Insert the second mounting housing into the first mounting housing and secure it with the second bolt;

[0022] S60: Connect the microwave source input port to the microwave generator, and use an electromagnetic radiation tester to test the microwave radiation at both ends of the outer conductor microwave shielding shell. When the microwave radiation at both ends of the outer conductor microwave shielding shell is >5mW / If the microwave radiation at both ends of the outer conductor microwave shielding shell is <5mw / Then proceed to step S70;

[0023] S70: The Q value of the coaxial resonant cavity is detected by frequency sweep measurement using the reflection method. If the Q value is <15000, it is returned to the non-conforming product warehouse for inspection. If the Q value is >15000, the printhead meets the manufacturing standards.

[0024] The beneficial effects of this invention are:

[0025] (1) The outer wall of the outer conductor microwave shielding shell is provided with a microwave source input port. By applying microwaves, the conductive composite thermoplastic filament can be heated quickly in a short time. Compared with traditional resistance heating, the heating rate is greatly improved. The conductive thermoplastic filament can also be heated more quickly by increasing the power of the microwave source, thus improving the heating rate. When the conductivity of the conductive composite thermoplastic filament is high, the magnetic field can be better introduced to the inlet and outlet accessories, so that the heating area of ​​the filament is near the extrusion port. The length of the coaxial inner conductor in the outer conductor microwave shielding shell is less than the height of the coaxial resonant cavity, so that the quartz tube is partially exposed in the coaxial resonant cavity. The quartz tube is a wave-transparent material, and microwaves act on the filament through the quartz tube to heat the filament.

[0026] (2) A connecting groove is provided at the bottom of the choke housing. The flange includes a mounting part and a connecting part integrally formed with the mounting part. The mounting part is installed at the bottom of the choke housing by a first bolt. The connecting part is located in the connecting groove. There is a choke cavity between the connecting groove and the connecting part. The choke cavity has the function of guiding the microwave to reverse the phase. At the entrance of the choke cavity, the microwave will be canceled by its reverse reflection wave, that is, the current of certain frequency bands is restricted to pass through, and microwave leakage is prevented. A polytetrafluoroethylene (PTFE) ring is installed in the choke cavity. The PTFE ring not only has the characteristics of wear resistance and aging resistance, but can also effectively enhance the service life of the print head. The choke cavity can effectively reduce signal transmission loss and prevent microwave leakage, which can cause harm.

[0027] (3) Based on the relative permittivity of the filler in the coaxial line Characteristic impedance Minimum operating wavelength The appropriate outer diameter of the coaxial inner conductor can be calculated. and the inner diameter of the outer conductor microwave shielding shell. Increasing the Q value within the coaxial resonant cavity is crucial. The Q value is an indicator of resonant cavity performance, defined as the ratio of the total energy stored in the cavity to the energy lost per cycle. A high Q value indicates that the resonant cavity has very low energy loss per unit time, thus enabling it to maintain oscillation for a longer period.

[0028] (4) The outer wall of the coaxial inner conductor is provided with a plurality of first annular grooves, and the inner wall of the outer conductor microwave shielding shell is provided with a plurality of second annular grooves corresponding to the first annular grooves. =( - )-( - When the Q value is 0.25~0.3mm, setting the first annular groove and the second annular groove, and the offset of the first annular groove and the second annular groove relative to the axial direction of the coaxial resonant cavity is Δl=0~0.2mm, can effectively increase the Q value of the coaxial resonant cavity. A high Q value means that the energy loss of the resonant cavity is low per unit time, which is generally beneficial to improving the performance of the equipment, increasing the utilization rate of microwave energy, and suppressing self-excited oscillation, ensuring the stable operation of the printing process.

[0029] (5) As the offset Δl of the first and second annular grooves relative to the axial direction of the coaxial resonant cavity increases, the Q value of the coaxial resonant cavity decreases. If the coaxial inner conductor is installed by means such as thread fixing or snap-fit ​​fixing, the microwave shielding shell of the coaxial inner conductor and the outer conductor may move along the axial direction. Since the quartz tube is a vulnerable part that needs to be replaced frequently, it is very likely that it will not be tightened or the snap-fit ​​will not be installed properly during the replacement process, causing the first and second annular grooves to be misaligned. Therefore, the coaxial inner conductor can be installed between the first and second mounting shells by the second bolt to prevent the first and second annular grooves from being misaligned, thereby reducing the working efficiency of the coaxial resonant cavity and effectively preventing microwave leakage. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 This is a structural schematic diagram provided in Embodiment 1 of the present invention.

[0032] Figure 2 This is a cross-sectional structural diagram provided in Embodiment 1 of the present invention.

[0033] Figure 3 yes Figure 2 A magnified schematic diagram of the central part of the structure.

[0034] Figure 4 This is a schematic diagram of a three-dimensional modeling using COMSOL software provided in Embodiment 1 of the present invention.

[0035] Figure 5 This is a diagram showing the electric field mode results of a simulated microwave heating coaxial resonator provided in Embodiment 1 of the present invention.

[0036] Figure 6 This is a simulation result diagram of the magnetic field mode of a microwave-heated coaxial resonator provided in Embodiment 1 of the present invention.

[0037] Figure 7 This is a structural diagram of the wire heating part in the magnetic field concentration area provided in Embodiment 1 of the present invention.

[0038] Figure 8 This is a graph showing the electromagnetic power loss density results of a simulated microwave-heated coaxial resonator provided in Embodiment 1 of the present invention.

[0039] Figure 9 This is an enlarged view of the electromagnetic power loss density of the simulated microwave heating coaxial resonator provided in Embodiment 1 of the present invention.

[0040] Figure 10 This is a schematic diagram of the electric and magnetic field distributions of TEM and TM01 modes in a coaxial resonant cavity provided in Embodiment 2 of the present invention.

[0041] Figure 11 This is a schematic diagram of the electric and magnetic field distributions in different regions of the coaxial resonant cavity provided in Embodiment 2 of the present invention.

[0042] Figure 12 This is a schematic diagram showing the variation of the Q value of the coaxial resonant cavity with the difference Δr between the inner and outer slot depths provided in Embodiment 2 of the present invention.

[0043] Figure 13 This is a schematic diagram showing the variation of the Q value of the coaxial resonant cavity with the internal and external misalignment value Δl provided in Embodiment 2 of the present invention.

[0044] Figure 14 This is a schematic diagram of the structure provided in Embodiment 2 of the present invention.

[0045] Figure 15 This is a cross-sectional structural diagram provided in Embodiment 2 of the present invention.

[0046] Figure 16 This is a schematic diagram of the first mounting housing and the second mounting housing provided in Embodiment 2 of the present invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0049] Example 1:

[0050] Reference Figures 1-3 As shown, a microwave-heated coaxial resonator printhead includes an outer conductor microwave shielding shell 10. The sidewall of the outer conductor microwave shielding shell 10 is integrally formed into a sidewall pipe by machining. The sidewall pipe is equipped with a microwave source input port 11. In this embodiment, the microwave source input port 11 can be connected to a 300W microwave source to input electromagnetic waves into the coaxial cavity. An outer conductor microwave shielding block 20 is welded to the top of the outer conductor microwave shielding shell 10. A coaxial inner conductor 30 is fixed inside the outer conductor microwave shielding block 20. The coaxial inner conductor 30 is located inside the outer conductor microwave shielding shell 10 and forms a coaxial resonant cavity 21 with the outer conductor microwave shielding shell 10. A choke groove shell 40 is welded to the bottom of the outer conductor microwave shielding shell 10. A flange 50 is installed at the bottom of the choke groove shell 40. A quartz tube 60 is inserted inside the coaxial inner conductor 30 and extends to the outlet end of the flange 50. The length of the coaxial inner conductor 30 inside the outer conductor microwave shielding shell 10 is less than the height of the coaxial resonant cavity 21, so that part of the quartz tube 60 is exposed inside the coaxial resonant cavity 21. This exposed part is the heating section of the wire.

[0051] The bottom of the choke housing 40 is provided with a connecting groove 41. The flange 50 includes a mounting part 51 and a connecting part 52 integrally formed with the mounting part 51. The mounting part 51 is installed at the bottom of the choke housing 40 by a first bolt 53. The connecting part 52 is located in the connecting groove 41. There is a choke cavity 54 between the connecting groove 41 and the connecting part 52. A polytetrafluoroethylene ring 55 is installed in the choke cavity 54. The polytetrafluoroethylene ring 55 not only has the characteristics of wear resistance and aging resistance, which can effectively extend the service life of the printhead, but also can effectively reduce signal transmission loss and prevent microwave leakage and damage within the choke cavity.

[0052] Reference Figure 2 As shown, the outer diameter of the coaxial inner conductor 30 is defined as... The inner diameter of the outer conductor microwave shielding shell 10 is The characteristic impedance of the coaxial transmission line and the TEM mode of the coaxial resonant cavity are determined. and Then there is

[0053] , <

[0054] in The relative permittivity of the filler in the coaxial line. Characteristic impedance, To achieve the minimum operating wavelength, in this embodiment, the relative permittivity of the coaxial cable is [value missing]. Set the value to 1, and select the characteristic impedance. The resistance is 50Ω to facilitate compatibility with existing RF and microwave equipment, and the calculated value is... and The ratio between them is approximately 7:3, while the minimum operating wavelength... It can be done through formula = ,in, It is frequency (unit: Hertz Hz). It is the speed of light (approximately 3 × 10⁻⁶ in a vacuum). In this embodiment, the microwave frequency used is 2.45 GHz, and its corresponding minimum operating wavelength can be calculated to be approximately 0.12 m. <0.12m, then <0.038m, then according to and The ratio between them is approximately 7:3. Based on the design of commonly used 3D printing heads, we can derive... =8.75mm, =3.75mm.

[0055] A microwave-heated coaxial resonator printhead for fused deposition modeling according to the present invention is shown in the 3D model in COMSOL software as follows: Figure 4 As shown, the modeling area only includes the air, polytetrafluoroethylene, and choke structure areas in the microwave-heated coaxial resonator. The rest of the external metal frame is replaced by metal boundaries to shield electromagnetic waves.

[0056] Electromagnetic and thermal simulation of a microwave-heated coaxial resonator printhead for fused deposition modeling in COMSOL software according to the present invention. Figure 5 These are the electric field mode results of a simulated microwave-heated coaxial resonator; Figure 6 The results show the magnetic field mode of a simulated microwave-heated coaxial resonator. According to the results, the electric and magnetic fields are successfully introduced into the microwave-heated coaxial resonator. According to Maxwell's principle, the magnetic field is weaker in areas with a strong electric field and stronger in areas with a weak electric field.

[0057] Simulation results show that the heating element of the wire is mainly located in the region where the magnetic field is concentrated, such as... Figure 7 As shown, with a heating time T=8s, the wire temperature reached 219℃, which is the material's melting temperature. The dB values ​​at both the wire input port and the extrusion port are less than -10dB, indicating that the microwave leakage meets the requirements, demonstrating the effectiveness of the choke structure in suppressing microwave leakage.

[0058] like Figure 8 The results show the electromagnetic power loss density of a simulated microwave-heated coaxial resonator. Figure 9 This is an enlarged view of the electromagnetic power loss density of a simulated microwave-heated coaxial resonator; this area also represents the heating location.

[0059] An assembly and testing method for a microwave-heated coaxial resonator printhead includes the following steps:

[0060] S10: Install the microwave source input port 11 on the side wall of the outer conductor microwave shielding housing 10;

[0061] S20: Weld the first mounting housing 22 and the choke slot housing 40 to both ends of the outer conductor microwave shielding housing 10:

[0062] S30: Place the polytetrafluoroethylene ring 55 in the connecting groove 41, then place the flange 50 in the connecting groove 41, and secure the flange 50 by tightening it with the first bolt 53.

[0063] S40: Place the quartz tube 60 inside the coaxial inner conductor 30, and place the coaxial inner conductor 30 inside the outer conductor microwave shielding shell 10. Then move the quartz tube 60 to the outlet end of the flange 50.

[0064] S50: Insert the second mounting housing 23 into the first mounting housing 22 and secure it by tightening the second bolt 235;

[0065] S60: Connect the microwave source input port 11 to the microwave generator, and use an electromagnetic radiation tester to test the microwave radiation at both ends of the outer conductor microwave shielding shell 10. When the microwave radiation at both ends of the outer conductor microwave shielding shell 10 is >5mW / If the microwave radiation at both ends of the outer conductor microwave shielding shell 10 is <5mw / If the microwave leakage is detected, step S70 is executed. This can effectively prevent the leakage from affecting the Q value of the coaxial resonant cavity 21 and causing unstable test results. In addition, it can be used to check whether the sealing is not properly set, which lays the groundwork for subsequent work and increases the efficiency of production and manufacturing as well as the quality of the product.

[0066] S70: The Q value of the coaxial resonant cavity 21 is measured by frequency sweep measurement using the reflection method. If the Q value is <15000, it is returned to the non-conforming product warehouse for inspection. If the Q value is >15000, the printhead meets the manufacturing standards.

[0067] Example 2:

[0068] like Figures 10-16 As shown, the difference between this embodiment and Embodiment 1 is that, since the coaxial resonant cavity 21 in Embodiment 1 is in TEM mode, both the electric field E and the magnetic field H are perpendicular to the propagation direction in TEM mode, which may cause a decrease in microwave propagation speed. Therefore, using the coupling method of TM01 and TEM mode can improve microwave propagation efficiency, such as... Figure 10 As shown, in this embodiment, the outer wall of the coaxial inner conductor 30 is provided with two sets of first annular grooves 31, and the inner wall of the outer conductor microwave shielding shell 10 is provided with two sets of second annular grooves 12 corresponding to the first annular grooves 31. The second annular grooves 12 corresponding to the first annular grooves 31 adopt TM01 mode, and the second annular grooves 12 corresponding to other parts without first annular grooves 31 adopt TEM mode. The Q value of the coaxial resonant cavity can be expressed as Q = W / P, where =2 W and P represent the angular frequency, stored energy, and coupling power of the resonant cavity, respectively. Therefore, it can be seen that when the angular frequency and stored energy of the resonant cavity are constant, the Q value of the resonant cavity is maximized when the coupled power is minimized. To obtain the minimum coupling power, we analyzed the coupling process between the TM01 and TEM modes in the coaxial resonant cavity, as follows... Figure 11 As shown, the TM01 mode of a closed coaxial resonant cavity only has the axial electric field Ez and the angular magnetic field. The TEM mode of a coaxial waveguide only has the radial electric field Er and the angular magnetic field. The axial electric field Ez of the TM01 mode is orthogonal to the radial electric field Er of the TEM, meaning that when the two parts of the structure form an open coaxial resonant cavity, the coupling between the TM01 and TEM modes is mainly through the angular magnetic field. Transformation. Further analysis of the angular magnetic field of the open coaxial resonant cavity. Analyze the distribution, such as Figure 11 As shown, the TM01 mode in the open coaxial resonant cavity was found to have an angular magnetic field in the inner diameter. Angular magnetic field greater than outer diameter And in opposite directions, the angular magnetic field of the TEM mode in the coaxial waveguide There is only one direction, such as Figure 10 As shown in (3), this means that the TM01 mode in the resonant cavity has an angular magnetic field in the inner diameter. With outer diameter angular magnetic field The difference ( - This can be used to characterize the strength of the coupling between the TM01 mode and the TEM mode. Therefore, the angular magnetic field can be changed by adjusting the difference in slot depth Δr between the inner and outer sides of the coaxial resonant cavity. Distribution, causing the angular magnetic field within the inner diameter of the coaxial resonant cavity As close as possible to the outer diameter angular magnetic field This minimizes the magnetic field coupling between the TM01 and TEM modes, allowing the coaxial resonator to be designed with a high Q value. Based on the above analysis of the coaxial resonator's structural characteristics, the radius of the first annular groove 31 is defined as... The radius of the second annular groove 12 is Then there is =( - )-( - The offset of the first annular groove 31 and the second annular groove 12 relative to the axial direction of the coaxial resonant cavity 21 is defined as Δl. The Q-value characteristics of the coaxial resonant cavity under different structural parameters are studied using CST simulation software. 5mm 7.5mm It is 21.5mm. When the diameter is 23 mm and Δl is 0 mm, change The value of , The variation range is 23–25 mm, and typical simulation results are as follows: Figure 12 As shown, the Q value of the coaxial resonant cavity 21 is related to... The changes are very sensitive, when It is 23.4mm, corresponding to The diameter is 0.25 mm. At this time, the Q value of the coaxial resonant cavity 21 is 14376. It is 23.3mm, corresponding to The diameter is 0.3 mm. At this point, the Q value of the coaxial resonant cavity 21 is 16548. Designing the coaxial resonant cavity 21 as a high-Q cavity means that the TEM mode leakage in the coaxial resonant cavity 21 is minimized. When The diameter is 23 mm, corresponding to a Δr of 0 mm. The Q value of the coaxial resonant cavity is only 2406. Therefore, the coaxial resonant cavity 21 is a low-Q cavity. Thus, when designing the coaxial resonant cavity 21, the variation of Δr within the range of 0.25~0.3 mm should be considered. Therefore, in the structural design of the coaxial resonant cavity 21, strict control of Δr is also necessary. The changes. Figure 13 Given It is 5 mm. It is 7.5 mm. It is 21.5mm. It is 23mm. When the diameter is 0.3mm, the frequency of the resonant cavity is... Based on the relationship between Q value and Δl, it can be seen that when Δl = 0~0.2mm, the axial misalignment Δl has little effect on the frequency f of the resonant cavity. Furthermore, as the axial misalignment Δl increases, the Q value gradually decreases, and the decreasing trend intensifies. Therefore, when designing the coaxial resonant cavity 21, the axial offset Δl should be considered to be between 0~0.2mm, which can effectively improve the Q value and increase the efficiency of microwave heating.

[0069] Since the axial offset Δl is between 0 and 0.2 mm, it can effectively maintain the high Q value cavity state. Therefore, if conventional threaded connections or snap-fit ​​fixing methods are used to fix the coaxial inner conductor 30 and the outer conductor microwave shielding block 20, there may be problems with improper installation. To address the above problems, this invention designs an outer conductor microwave shielding block 20, which includes a first mounting housing 22 and a second mounting housing 23. The bottom of the first mounting housing 22 is welded to the top of the outer conductor microwave shielding housing 10, which can effectively prevent microwave leakage. The bottom of the first mounting housing 22 is provided with a first through hole 221 adapted to the coaxial inner conductor 30. The outer side of the first mounting housing 22 away from the outer conductor microwave shielding housing 10 is provided with an annular mounting groove 222. The inner side of the first mounting housing 22 away from the outer conductor microwave shielding housing 10 is provided with an inner conductor mounting groove 223 coaxial with the annular mounting groove 222. The side wall of the inner conductor mounting groove 223 is provided with a bolt mounting block 2231. The side wall of the first mounting housing 22 is provided with a through hole. The annular mounting groove 222 and the bolt mounting block 2231 have bolt fixing holes 2232. A mounting block 32, adapted to the inner conductor mounting groove 223, is provided on the outer wall of the coaxial inner conductor 30. The mounting block 32 is disposed within the inner conductor mounting groove 223. The second mounting housing 23 has a housing sidewall 231 corresponding to the annular mounting groove 222. The housing sidewall 231 has bolt fixing holes 232 corresponding to the bolt fixing groove. An abutment block 23 adapted to the inner conductor mounting groove 223 is provided within the housing sidewall 231. 3. The top of the second mounting housing 23 is provided with a second through hole 234 adapted to the coaxial inner conductor 30. When the housing sidewall 231 is inserted into the annular mounting groove 222, the bolt mounting hole 232 is aligned with the bolt fixing hole 2232 and locked in place by the second bolt 235. The abutment block 233 abuts against the mounting block 32, so that the coaxial inner conductor 30 is securely mounted on the outer conductor microwave shielding block 20, thereby realizing the installation and fixation of the coaxial inner conductor 30 and preventing the reduction of microwave efficiency due to excessive axial offset Δl. A polytetrafluoroethylene block 236 is provided at the bottom of the abutment block 233. When the abutment block 233 presses down against the mounting block 32, it can effectively compress the polytetrafluoroethylene block 236, so as to achieve a good effect of suppressing microwave leakage.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A microwave-heated coaxial resonator printhead, characterized in that, include: An outer conductor microwave shielding shell (10) has a microwave source input port (11) conductively disposed on its outer wall. The outer conductor microwave shielding shell (10) is made of metal and has an outer conductor microwave shielding block (20) welded to its top. A coaxial inner conductor (30) is fixedly disposed inside the outer conductor microwave shielding block (20). The coaxial inner conductor (30) is disposed inside the outer conductor microwave shielding shell (10) and forms a coaxial resonant cavity (21) with the outer conductor microwave shielding shell (10). A choke groove shell (40) is welded to the bottom of the outer conductor microwave shielding shell (10). A flange (50) is installed at the bottom of the choke groove shell (40). A quartz tube (60) passes through the coaxial inner conductor (30) and extends to the flange (50). At the port end, the length of the coaxial inner conductor (30) disposed within the outer conductor microwave shielding shell (10) is less than the height of the coaxial resonant cavity (21), so that part of the quartz tube (60) is exposed within the coaxial resonant cavity (21). A connecting groove (41) is provided at the bottom of the choke groove shell (40). The flange (50) includes a mounting part (51) and a connecting part (52) integrally formed with the mounting part (51). The mounting part (51) is installed at the bottom of the choke groove shell (40) by a first bolt (53). The connecting part (52) is disposed within the connecting groove (41). A choke cavity (54) is provided between the connecting groove (41) and the connecting part (52). A polytetrafluoroethylene ring (55) is installed within the choke cavity (54). The outer diameter of the coaxial inner conductor (30) is defined as... The inner diameter of the outer conductor microwave shielding shell (10) is Then there is ＜ in The relative permittivity of the filler in the coaxial line. Characteristic impedance, This is the minimum operating wavelength.

2. The microwave-heated coaxial resonator printhead according to claim 1, characterized in that, The outer wall of the coaxial inner conductor (30) is provided with a plurality of first annular grooves (31), and the inner wall of the outer conductor microwave shielding shell (10) is provided with a plurality of second annular grooves (12) corresponding to the first annular grooves (31). The radius of the first annular groove (31) is defined as... The radius of the second annular groove (12) is Then there is =( - )-( - =0.25~0.3mm.

3. The microwave-heated coaxial resonator printhead according to claim 2, characterized in that, The offset of the first annular groove (31) and the second annular groove (12) relative to the axial direction of the coaxial resonant cavity (21) is defined as Δl, then Δl = 0~0.2mm.

4. A microwave-heated coaxial resonator printhead according to claim 3, characterized in that, The outer conductor microwave shielding block (20) includes a first mounting housing (22) and a second mounting housing (23). The bottom of the first mounting housing (22) is welded to the top of the outer conductor microwave shielding housing (10). The bottom of the first mounting housing (22) is provided with a first through hole (221) adapted to the coaxial inner conductor (30). An annular mounting groove (222) is provided on the outer side of the first mounting housing (22) away from the outer conductor microwave shielding housing (10). An inner conductor mounting groove (223) coaxial with the annular mounting groove (222) is provided on the inner side of the first mounting housing (22) away from the outer conductor microwave shielding housing (10). A bolt mounting block (2231) is provided on the side wall of the inner conductor mounting groove (223). A bolt fixing hole (2232) penetrating the annular mounting groove (222) and the bolt mounting block (2231) is provided on the side wall of the first mounting housing (22). A bolt fixing hole (2232) is provided on the outer side wall of the coaxial inner conductor (30). A mounting block (32) adapted to the inner conductor mounting groove (223) is provided inside the inner conductor mounting groove (223). The second mounting housing (23) is provided with a housing sidewall (231) corresponding to the annular mounting groove (222). The housing sidewall (231) is provided with bolt mounting holes (232) corresponding to the bolt fixing groove. An abutment block (233) adapted to the inner conductor mounting groove (223) is provided inside the housing sidewall (231). The second mounting housing (23) has a second through hole (234) at the top that is adapted to the coaxial inner conductor (30). When the housing sidewall (231) is inserted into the annular mounting groove (222), the bolt mounting hole (232) is aligned with the bolt fixing hole (2232) and the second bolt (235) is used to lock and fix it. The abutment block (233) abuts against the mounting block (32), so that the coaxial inner conductor (30) is securely mounted on the outer conductor microwave shielding block (20).

5. A microwave-heated coaxial resonator printhead according to claim 4, characterized in that, A polytetrafluoroethylene block (236) is provided at the bottom of the abutment block (233).

6. An assembly and testing method for a microwave-heated coaxial resonator printhead. Applied to a microwave-heated coaxial resonator printhead as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S10: Install the microwave source input port (11) on the side wall of the outer conductor microwave shielding shell (10); S20: Weld the first mounting housing (22) and the choke housing (40) to both ends of the outer conductor microwave shielding housing (10): S30: Place the polytetrafluoroethylene ring (55) in the connecting groove (41), then place the flange (50) in the connecting groove (41), and secure the flange (50) by the first bolt (53). S40: Place the quartz tube (60) inside the coaxial inner conductor (30), and place the coaxial inner conductor (30) inside the outer conductor microwave shielding shell (10), and then move the quartz tube (60) to the outlet end of the flange (50); S50: Insert the second mounting housing (23) into the first mounting housing (22) and secure it by tightening it with the second bolt (235); S60: Connect the microwave source input port (11) to the microwave generator, and use an electromagnetic radiation tester to test the microwave radiation at both ends of the outer conductor microwave shielding shell (10). When the microwave radiation at both ends of the outer conductor microwave shielding shell (10) is >5mw / If the microwave radiation at both ends of the outer conductor microwave shielding shell (10) is less than 5mw / Then proceed to step S70; S70: The Q value of the coaxial resonant cavity (21) is measured by frequency sweep measurement using the reflection method. If the Q value is <15000, it is returned to the non-conforming product warehouse for inspection. If the Q value is >15000, the printhead meets the manufacturing standard.

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