Novel microwave heating printing head

Abstract

The utility model provides a novel microwave heating printing head which comprises an outer conductor microwave shielding shell, a microwave input source is arranged on the outer wall of the outer conductor microwave shielding shell in a conducting mode, an outer conductor microwave shielding upper shell is welded to the top of the outer conductor microwave shielding shell, and a coaxial microwave shielding inner conductor is fixedly arranged in the outer conductor microwave shielding upper shell. The coaxial microwave shielding inner conductor is arranged in the outer conductor microwave shielding shell, the coaxial microwave shielding inner conductor and the outer conductor microwave shielding shell define a coaxial resonant cavity, an outer conductor microwave shielding lower shell is welded to the bottom of the outer conductor microwave shielding shell, and a flange plate is installed at the bottom of the outer conductor microwave shielding lower shell. A quartz tube is arranged in the coaxial microwave shielding inner conductor in a penetrating manner and extends to the outlet end of the flange plate, and the length of the coaxial microwave shielding inner conductor arranged in the outer conductor microwave shielding shell is smaller than the height of the coaxial resonant cavity, so that the quartz tube is partially exposed in the coaxial resonant cavity. The conductive composite thermoplastic wire can be rapidly heated within a short time by applying microwaves, and compared with traditional resistance heating, the heating rate is greatly increased.

Description

Technical Field

[0001] The utility model relates to a novel microwave heating print head, which is applied to the field of 3D printing. Background Art

[0002] 3D printing technology, also known as additive manufacturing technology, has gradually developed into a mature manufacturing method based on advanced digital and computer technology. 3D printers build three-dimensional object models by melting conductive filaments and stacking these materials layer by layer. This method can produce three-dimensional models with complex designs and rich details. Compared with traditional manufacturing processes, 3D printing technology can simplify the manufacturing process, reduce manufacturing costs, quickly produce finished products, significantly improve production efficiency, and reduce material waste.

[0003] However, traditional 3D printers mostly use resistance heating when heating filaments, and the heating speed is slow, usually only 2℃ / s, which makes the heating process take a long time and the heating process may not be uniform. In order to overcome these limitations, the utility model proposes a new type of microwave heating print head, which uses coaxial resonator technology to heat the filament. This design is expected to improve heating efficiency, shorten heating time, and achieve a more uniform heating effect, thereby further improving the performance of 3D printing technology. Utility Model Content

[0004] The utility model provides a novel microwave heating print head, which can effectively solve the above problems.

[0005] The utility model is achieved in this way:

[0006] A novel microwave heating print head, comprising:

[0007] An outer conductor microwave shielding shell, an outer wall of which is conductively connected to a microwave input source, an outer conductor microwave shielding upper shell is welded on the top of the outer conductor microwave shielding shell, a coaxial microwave shielding inner conductor is fixedly arranged in the outer conductor microwave shielding upper shell, the coaxial microwave shielding inner conductor is arranged in the outer conductor microwave shielding shell, and is enclosed with the outer conductor microwave shielding shell to form a coaxial resonant cavity, an outer conductor microwave shielding lower shell is welded to the bottom of the outer conductor microwave shielding shell, a flange is installed at the bottom of the outer conductor microwave shielding lower shell, a quartz tube is passed through the coaxial microwave shielding inner conductor and extends to the flange outlet end, the length of the coaxial microwave shielding inner conductor arranged 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.

[0008] As a further improvement, a connecting groove is provided at the bottom of the outer conductor microwave shielding lower shell, the flange includes a mounting portion and a connecting portion integrally formed with the mounting portion, the mounting portion is installed on the bottom of the outer conductor microwave shielding lower shell by a first bolt, the connecting portion is provided in the connecting groove, a choke cavity is provided between the connecting groove and the connecting portion, and a polytetrafluoroethylene ring is installed in the choke cavity.

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

[0010] , <

[0011] in is the relative dielectric constant filled in the coaxial line, is the characteristic impedance, is the minimum operating wavelength.

[0012] As a further improvement, the outer wall of the coaxial microwave shielding 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, and the radius of the first annular groove is defined as , the radius of the second annular groove is , then =( - )-( - )=0.25~0.3mm.

[0013] As a further improvement, the offset of the first annular groove and the second annular groove 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 upper shell includes a first mounting shell and a second mounting shell, the bottom of the first mounting shell is welded to the top of the outer conductor microwave shielding shell, the bottom of the first mounting shell is provided with a first penetration hole adapted to the coaxial microwave shielding inner conductor, the outer side of the first mounting shell away from the end of the outer conductor microwave shielding shell is provided with a circle of annular mounting grooves, the inner side of the first mounting shell away from the end of the outer conductor microwave shielding shell is provided with an inner conductor mounting groove coaxial with the annular mounting groove, the side wall of the inner conductor mounting groove is provided with a bolt mounting block, the side wall of the first mounting shell is provided with a bolt fixing hole that penetrates the annular mounting groove and the bolt mounting block, and the coaxial microwave shield A mounting block adapted to the inner conductor mounting groove is provided on the outer side wall of the shielded inner conductor, and the mounting block is provided in the inner conductor mounting groove. The second mounting shell is provided with a shell side wall corresponding to the annular mounting groove, and the shell side wall is provided with a bolt mounting hole corresponding to the bolt fixing groove. An abutment block adapted to the inner conductor mounting groove is provided in the shell side wall. A second penetration hole adapted to the coaxial microwave shielding inner conductor is provided on the top of the second mounting shell. When the shell side wall is inserted into the annular mounting groove, the bolt mounting hole is aligned with the bolt fixing hole and is locked and fixed using the second bolt. The abutment block abuts against the mounting block, so that the coaxial microwave shielding inner conductor is fastened to the outer conductor microwave shielding upper shell.

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

[0016] The beneficial effects of the utility model are:

[0017] (1) The outer wall of the outer conductor microwave shielding shell is provided with a microwave input source, and the conductive composite thermoplastic wire can be quickly heated in a short time by applying microwaves. Compared with the traditional resistance heating, the heating temperature rise rate is greatly improved; the conductive thermoplastic wire can also be heated more quickly by increasing the power of the microwave source, thereby improving the heating temperature rise rate; when the conductivity of the conductive composite thermoplastic wire is high, the magnetic field can be better introduced into the inlet and outlet accessories, so that the heating area of ​​the wire is near the extrusion outlet. The length of the coaxial microwave shielding inner conductor arranged 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-transmitting material, and the microwave acts on the wire through the quartz tube to heat the wire.

[0018] (2) A connecting groove is provided at the bottom of the outer conductor microwave shielding lower shell, and the flange includes a mounting portion and a connecting portion integrally formed with the mounting portion. The mounting portion is installed on the bottom of the outer conductor microwave shielding lower shell by a first bolt, and the connecting portion is provided in the connecting groove. A choke cavity is provided between the connecting groove and the connecting portion. 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 offset by its reverse reflected wave, that is, the current passing through certain frequency bands is limited to prevent the leakage of microwaves. A polytetrafluoroethylene (PTFE) ring is installed in the choke cavity. The polytetrafluoroethylene ring is not only wear-resistant and aging-resistant, but can also effectively extend the service life of the print head. The choke cavity can effectively reduce the transmission loss of the signal and prevent microwave leakage and damage.

[0019] (3) According to the relative dielectric constant filled in the coaxial line , characteristic impedance , minimum operating wavelength The outer diameter of the suitable coaxial microwave shield inner conductor can be calculated , and the inner diameter of the outer conductor microwave shielding shell , increase the Q value in the coaxial resonant cavity. The Q value is an indicator to measure the performance of the resonant cavity. It is defined as the ratio of the total energy stored in the resonant cavity to the energy lost in each cycle. A high Q value means that the energy loss of the resonant cavity per unit time is very low, so it can maintain oscillation for a longer time.

[0020] (4) The outer wall of the coaxial microwave shielding 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. =( - )-( - )=0.25~0.3mm, a first annular groove and a second annular groove are set, 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, which can effectively increase the Q value of the coaxial resonant cavity. A high Q value means that the energy loss of the resonant cavity per unit time is low, which is usually beneficial to improving the performance of the equipment, improving the utilization rate of microwave energy, and can suppress self-excited oscillation to ensure the stability of the printing process.

[0021] (5) As the axial offset Δl of the first annular groove and the second annular groove relative to the coaxial resonant cavity increases, the Q value of the coaxial resonant cavity decreases. If the coaxial microwave shielding inner conductor is installed by means such as threaded fixing or snap-on fixing, the coaxial microwave shielding inner conductor and the outer conductor microwave shielding shell may move axially. Since the quartz tube is a consumable part that needs to be replaced more frequently, during the replacement process, it is very likely that the tube will not be tightened or the snap-on will not be installed in place, causing the first annular groove and the second annular groove to be misaligned. Therefore, the coaxial microwave shielding inner conductor can be installed between the first mounting shell and the second mounting shell by the second bolt to prevent the first annular groove and the second annular groove from being misaligned, thereby reducing the working efficiency of the coaxial resonant cavity and effectively preventing microwave leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solution of the implementation mode of the utility model, the drawings required for use in the implementation mode will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the utility model and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 It is a structural schematic diagram provided by Example 1 of the utility model.

[0024] Figure 2 It is a schematic cross-sectional structure diagram provided by Embodiment 1 of the present utility model.

[0025] Figure 3 yes Figure 2 Schematic diagram of the partially enlarged structure.

[0026] Figure 4 It is a schematic diagram of three-dimensional modeling using COMSOL software provided in the first embodiment of the present utility model.

[0027] Figure 5 This is a diagram of the electric field mode result of the simulated microwave heating coaxial resonator provided in Example 1 of the utility model.

[0028] Figure 6 This is a diagram of the magnetic field mode results of a simulated microwave heating coaxial resonator provided in Example 1 of the utility model.

[0029] Figure 7 This is a structural diagram of the wire heating portion in the magnetic field concentration area provided in the first embodiment of the present utility model.

[0030] Figure 8 This is a diagram of the electromagnetic power loss density results of a simulated microwave heating coaxial resonator provided in Example 1 of the utility model.

[0031] Fig. 9 This is an enlarged diagram of the electromagnetic power loss density of the simulated microwave heating coaxial resonator provided in Example 1 of the utility model.

[0032] Fig.10 This is a schematic diagram of the electric and magnetic field distribution of the TEM and TM01 modes in the coaxial resonant cavity provided in the second embodiment of the present utility model.

[0033] Fig.11 This is a schematic diagram of the electric field and magnetic field distribution in different areas of the coaxial resonant cavity provided in the second embodiment of the present utility model.

[0034] Fig.12 It is a schematic diagram of the variation of the Q value of the coaxial resonant cavity with the difference Δr between the inner and outer groove depths provided in the second embodiment of the present utility model.

[0035] Fig.13 It is a schematic diagram of the variation of the Q value of the coaxial resonant cavity with the internal and external misalignment value Δl provided in the second embodiment of the present utility model.

[0036] Fig.14 It is a structural schematic diagram provided by the second embodiment of the present utility model.

[0037] Fig.15 It is a schematic cross-sectional structure diagram provided by Embodiment 2 of the present utility model.

[0038] Fig.16 It is a schematic diagram of the structure of the first mounting shell and the second mounting shell provided in the second embodiment of the present utility model. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the utility model. Therefore, the following detailed description of the embodiments of the utility model provided in the drawings is not intended to limit the scope of the utility model for which protection is sought, but merely represents the selected embodiments of the utility model. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the utility model.

[0040] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0041] Embodiment 1:

[0042] Reference Figures 1 to 3 As shown, a new type of microwave heating print head includes an outer conductor microwave shielding shell 10, the side wall of the outer conductor microwave shielding shell 10 is integrally formed by machining to form a side wall pipe, and the side wall pipe is installed with a microwave input source 11. In this embodiment, the microwave input source 11 can be connected to a 300W microwave source to input electromagnetic waves into the coaxial cavity. An outer conductor microwave shielding upper shell 20 is welded to the top of the outer conductor microwave shielding shell 10, and a coaxial microwave shielding inner conductor 30 is fixedly arranged in the outer conductor microwave shielding upper shell 20. The coaxial microwave shielding inner conductor 30 is arranged in the outer conductor microwave shielding shell 10, and is enclosed with the outer conductor microwave shielding shell 10 to form a coaxial resonant cavity 21. An outer conductor microwave shielding lower shell 40 is welded to the bottom of the outer conductor microwave shielding shell 10, and a flange 50 is installed at the bottom of the outer conductor microwave shielding lower shell 40. A quartz tube 60 is passed through the inside of the coaxial microwave shielding inner conductor 30 and extends to the outlet end of the flange 50. The length of the coaxial microwave shielding inner conductor 30 arranged in the outer conductor microwave shielding shell 10 is less than the height of the coaxial resonant cavity 21, so that the quartz tube 60 is partially exposed in the coaxial resonant cavity 21, and the exposed part is the heating section of the wire.

[0043] A connecting groove 41 is provided at the bottom of the outer conductor microwave shielding lower shell 40, and the flange 50 includes a mounting portion 51 and a connecting portion 52 integrally formed with the mounting portion 51. The mounting portion 51 is installed on the bottom of the outer conductor microwave shielding lower shell 40 by a first bolt 53, and the connecting portion 52 is provided in the connecting groove 41. A choke cavity 54 is provided between the connecting groove 41 and the connecting portion 52, and a polytetrafluoroethylene ring 55 is installed in the choke cavity 54. The polytetrafluoroethylene ring 55 is not only wear-resistant and aging-resistant, but can also effectively extend the service life of the print head, and can also effectively reduce the transmission loss of the signal in the choke cavity to prevent microwave leakage and damage.

[0044] Reference Figure 2 As shown, the outer diameter of the coaxial microwave shielding inner conductor 30 is defined as The inner diameter of the outer conductor microwave shielding shell 10 is , determined according to the characteristic impedance of the coaxial transmission line and the TEM mode of the coaxial resonant cavity and , then

[0045] , <

[0046] in is the relative dielectric constant filled in the coaxial line, is the characteristic impedance, is the minimum operating wavelength. In this embodiment, the relative dielectric constant filled in the coaxial line is =1, select characteristic impedance 50Ω, so as to match with existing RF and microwave equipment, then the calculation is and The ratio between them is about 7:3, and the minimum working wavelength The formula can be = ,in, is the frequency (in Hertz Hz), is the speed of light (about 3× m / s), in this embodiment, the microwave frequency used is 2.45 GHz, and its corresponding minimum operating wavelength can be calculated to be approximately equal to 0.12 m, so, <0.12m, then <0.038m, then according to and The ratio between them is about 7:3. According to the size design of the commonly used 3D printing head, it can be concluded that =8.75mm, =3.75mm.

[0047] The utility model is a microwave heating coaxial resonator print head for fused deposition molding in COMSOL software 3D modeling as shown in FIG. Figure 4 As shown, the modeling area of ​​the model only includes the air, polytetrafluoroethylene, and choke slot structure areas in the microwave heating coaxial resonator, and the rest of the external metal frames are replaced by setting metal boundaries to shield electromagnetic waves.

[0048] The utility model is a microwave heating coaxial resonator print head for fused deposition molding. The electromagnetic thermal simulation of COMSOL software, Figure 5 It is the result of simulating the electric field mode of the microwave heating coaxial resonator; Figure 6It is the result of simulating the magnetic field model of the microwave heating coaxial resonator. According to the results, it can be seen that the electric field and magnetic field are successfully introduced into the microwave heating coaxial resonator. According to Maxwell's principle, the magnetic field is weak in the area with strong electric field, and the magnetic field is strong in the area with weak electric field.

[0049] According to the simulation results, we can know that the wire heating part is mainly in the area where the magnetic field is concentrated, such as Figure 7 As shown in the figure, the heating time T=8s, the wire heating temperature reaches 219℃, reaching the melting temperature of the material. The dB values ​​of the wire input port and the extrusion port are both less than -10dB, which shows that the microwave leakage meets the requirements and the choke slot structure suppresses microwave leakage.

[0050] like Figure 8 As shown in the figure, the electromagnetic power loss density results of the simulated microwave heating coaxial resonator are Fig. 9 This is an enlarged view of the electromagnetic power loss density of the simulated microwave heating coaxial resonator. This area is also the heating location.

[0051] A novel assembly and testing method for a microwave heating print head comprises the following steps:

[0052] S10: Install the microwave input source 11 on the side wall of the outer conductor microwave shielding shell 10;

[0053] S20: Welding the first installation shell 22 and the outer conductor microwave shielding shell 10 to both ends of the outer conductor microwave shielding shell 10:

[0054] S30: placing the polytetrafluoroethylene ring 55 in the connecting groove 41, and then placing the flange 50 in the connecting groove 41, and fastening and fixing the flange 50 by means of the first bolt 53;

[0055] S40: placing the quartz tube 60 in the coaxial microwave shielding inner conductor 30, and placing the coaxial microwave shielding inner conductor 30 in the outer conductor microwave shielding shell 10, and then moving the quartz tube 60 to the outlet end of the flange 50;

[0056] S50: inserting the second mounting housing 23 into the first housing and fastening and fixing it by means of the second bolt 235;

[0057] S60: Connect the microwave input source 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 greater than 5mw / , then the unqualified products are returned to the warehouse for inspection. When the microwave radiation at both ends of the outer conductor microwave shielding shell 10 is less than 5mw / , then execute step S70, first check whether there is leakage of microwaves, which can effectively prevent the influence of microwaves on the Q value of the coaxial resonant cavity 21, resulting in unstable detection results, and can prioritize checking whether the sealing is not properly set, paving the way for subsequent work, and increasing the efficiency of production and the quality of products;

[0058] S70: Detect the Q value of the coaxial resonant cavity 21 by reflection scanning measurement. When the Q value is less than 15000, the unqualified product is returned to the warehouse for inspection. When the Q value is greater than 15000, the print head meets the manufacturing standards.

[0059] Embodiment 2:

[0060] like Figures 10 to 16 As shown, the difference between this embodiment and the first embodiment is that since the coaxial resonant cavity 21 in the first embodiment is in TEM mode, in the TEM mode, the electric field E and the magnetic field H are perpendicular to the propagation direction, which may cause the microwave propagation rate to decrease. Therefore, the microwave propagation efficiency can be improved by coupling the TM01 and TEM modes. Fig.10 As shown, in this embodiment, the outer wall of the coaxial microwave shielding inner conductor 30 is provided with two groups of first annular grooves 31, and the inner wall of the outer conductor microwave shielding shell 10 is provided with two groups 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 the TM01 mode, and the other second annular grooves 12 corresponding to the first annular grooves 31 are not provided. The TEM mode is adopted, and the Q value of the coaxial resonant cavity can be expressed as Q = W / P, where =2 , W and P are the angular frequency, energy storage and coupling power of the resonant cavity respectively. It can be seen that when the angular frequency and energy storage of the resonant cavity are constant, the Q value of the resonant cavity is the largest when the power coupled out of the resonant cavity is the smallest. In order to obtain the minimum value of the coupling power, we analyze the coupling process of the TM01 and TEM modes in the coaxial resonant cavity, as shown in the figure. Fig.11 As shown, it can be seen that the TM01 mode of the closed coaxial resonant cavity only has the axial electric field Ez and the angular magnetic field , the TEM mode of the coaxial waveguide only has radial electric field Er and angular magnetic field The axial electric field Ez of the TM01 mode is orthogonal to the radial electric field Er of the TEM mode, which means 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. Further analysis of the angular magnetic field of the open coaxial resonant cavity The distribution is analyzed, such as Fig.11 As shown in the figure, it is found that the angular magnetic field of the TM01 mode in the open coaxial resonant cavity is Greater than the angular magnetic field of the 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 Fig.10 (3) shows that the angular magnetic field of the TM01 mode in the resonant cavity at the inner diameter is Angular magnetic field with outer diameter The difference ( − ) 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 the depth of the inner and outer grooves of the coaxial resonant cavity Δr. Distribution, so that the angular magnetic field of the inner diameter of the coaxial resonant cavity As close as possible to the angular magnetic field of the outer diameter , so that the magnetic field coupling between the TM01 and TEM modes is minimized. At this time, the coaxial resonant cavity can be designed to have a high Q value. Based on the above analysis of the structural characteristics of the coaxial resonant cavity, the radius of the first annular groove 31 is defined as , the radius of the second annular groove 12 is , then =( - )-( - ). Define the axial offset of the first annular groove 31 and the second annular groove 12 relative to the coaxial resonant cavity 21 as Δl, and use CST simulation software to study the Q value characteristics of the coaxial resonant cavity under different structural parameters. 5mm, 7.5mm, 21.5mm, When Δl is 0 mm, change The value of The range is 23 to 25 mm. Typical simulation results are as follows: Fig.12 As shown, it can be seen that the Q value of the coaxial resonant cavity 21 is Very sensitive to changes, when is 23.4mm, corresponding to is 0.25 mm, at this time the Q value of the coaxial resonant cavity 21 is 14376. is 23.3mm, corresponding to is 0.3 mm. At this time, the Q value of the coaxial resonant cavity 21 is 16548. The coaxial resonant cavity 21 is designed to be a high-Q cavity, which means that the TEM mode leakage in the coaxial resonant cavity 21 is a minimum. is 23 mm, corresponding to Δr of 0 mm, the Q value of the coaxial resonant cavity is only 2406, and the coaxial resonant cavity 21 is a low Q value cavity. Therefore, when designing the coaxial resonant cavity 21, it is necessary to consider controlling the change of Δr in the range of 0.25~0.3mm. Therefore, when designing the structure of the coaxial resonant cavity 21, it is necessary to strictly control changes. Fig.13 Given 5 mm, 7.5 mm, 21.5mm, 23mm, When it is 0.3mm, the frequency of the resonant cavity From the relationship between the Q value and the change of 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, and with the increase of the axial misalignment Δl, the Q value gradually decreases, and the decreasing trend increases. Therefore, when designing the coaxial resonant cavity 21, the axial offset Δl should be considered between 0~0.2mm, which can effectively improve the Q value and improve the efficiency of microwave heating.

[0061] Since the axial offset Δl is between 0 and 0.2 mm, the high Q value cavity state can be effectively maintained. Therefore, if the coaxial microwave shielding inner conductor 30 and the outer conductor microwave shielding upper shell 20 are fixed by conventional threaded connection or snap-on fixing, there may be a problem of improper installation. In view of the above problem, the utility model designs an outer conductor microwave shielding upper shell 20, and the outer conductor microwave shielding upper shell 20 includes a first mounting shell 22 and a second mounting shell 23. The bottom of the first mounting shell 22 is welded to the top of the outer conductor microwave shielding shell 10. The first installation shell 22 is provided with a first through hole 221 adapted to the coaxial microwave shielding inner conductor 30 at the bottom, and the first installation shell 22 is provided with a circle of annular installation groove 222 on the outer side of one end away from the outer conductor microwave shielding shell 10, and the first installation shell 22 is provided with an inner conductor installation groove 223 coaxial with the annular installation groove 222 on the inner side of one end away from the outer conductor microwave shielding shell 10, and the inner side of the inner conductor installation groove 223 is provided with a bolt installation block 2231, and the side wall of the first installation shell 22 is provided with a through hole 2231. The annular mounting groove 222 and the bolt fixing hole 2232 of the bolt mounting block 2231, the outer wall of the coaxial microwave shielding inner conductor 30 is provided with a mounting block 32 adapted to the inner conductor mounting groove 223, the mounting block 32 is arranged in the inner conductor mounting groove 223, the second mounting shell 23 is provided with a shell side wall 231 corresponding to the annular mounting groove 222, the shell side wall 231 is provided with a bolt mounting hole 232 corresponding to the bolt fixing groove, the shell side wall 231 is provided with an abutment block 233 adapted to the inner conductor mounting groove 223, the second A second through hole 234 adapted to the coaxial microwave shielding inner conductor 30 is provided at the top of the installation shell 23. When the shell side wall 231 is inserted into the annular installation groove 222, the bolt installation hole 232 is aligned with the bolt fixing hole 2232 and is locked and fixed using the second bolt 235. The abutment block 233 abuts the installation block 32, so that the coaxial microwave shielding inner conductor 30 is fastened to the outer conductor microwave shielding upper shell 20, thereby achieving the installation and fixation of the coaxial microwave shielding inner conductor 30, and preventing the reduction of microwave efficiency due to excessive deviation of the axial offset Δl. A polytetrafluoroethylene block 236 is provided at the bottom of the abutment block 233. When the abutment block 233 is pressed down to abut the installation block 32, the polytetrafluoroethylene block 236 can be effectively compressed, so that it can achieve a good effect of suppressing microwave leakage.

[0062] The above description is only the preferred implementation of the utility model, and is not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

Claims

1. A novel microwave heating print head, characterized in that: include: An outer conductor microwave shielding shell (10) is provided with a microwave input source (11) on its outer wall, an outer conductor microwave shielding upper shell (20) is welded to the top of the outer conductor microwave shielding shell, a coaxial microwave shielding inner conductor (30) is fixedly provided in the outer conductor microwave shielding upper shell (20), the coaxial microwave shielding inner conductor (30) is arranged in the outer conductor microwave shielding shell (10) and encloses the outer conductor microwave shielding shell (10) to form a coaxial resonant cavity (21), the outer conductor microwave shielding shell (10) An outer conductor microwave shielding lower shell (40) is welded at the bottom, a flange (50) is installed at the bottom of the outer conductor microwave shielding lower shell (40), a quartz tube (60) is passed through the inside of the coaxial microwave shielding inner conductor (30) and extends to the outlet end of the flange (50), and the length of the coaxial microwave shielding inner conductor (30) arranged in the outer conductor microwave shielding shell (10) is less than the height of the coaxial resonant cavity (21), so that the quartz tube (60) is partially exposed in the coaxial resonant cavity (21).

2. A novel microwave heating print head according to claim 1, characterized in that: A connecting groove (41) is provided at the bottom of the outer conductor microwave shielding lower shell (40); the flange (50) comprises a mounting portion (51) and a connecting portion (52) integrally formed with the mounting portion (51); the mounting portion (51) is mounted on the bottom of the outer conductor microwave shielding lower shell (40) via a first bolt (53); the connecting portion (52) is arranged in the connecting groove (41); a choke cavity (54) is provided between the connecting groove (41) and the connecting portion (52); a polytetrafluoroethylene ring (55) is installed in the choke cavity (54).

3. A novel microwave heating print head according to claim 1, characterized in that: The outer diameter of the coaxial microwave shielding inner conductor (30) is defined as The inner diameter of the outer conductor microwave shielding shell (10) is , then ＜ in is the relative dielectric constant filled in the coaxial line, is the characteristic impedance, is the minimum operating wavelength.

4. A novel microwave heating print head according to claim 3, characterized in that: The outer wall of the coaxial microwave shielding 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 =( - )-( - )=0.25~0.3mm.

5. A novel microwave heating print head according to claim 4, characterized in that: The axial offset of the first annular groove (31) and the second annular groove (12) relative to the coaxial resonant cavity (21) is defined as Δl, and Δl=0-0.2 mm.

6. A novel microwave heating print head according to claim 5, characterized in that: The outer conductor microwave shielding upper shell (20) comprises a first mounting shell (22) and a second mounting shell (23), the bottom of the first mounting shell (22) being welded to the top of the outer conductor microwave shielding shell (10), the bottom of the first mounting shell (22) being provided with a first through hole (221) adapted to the coaxial microwave shielding inner conductor (30), the outer side of the first mounting shell (22) being away from the outer conductor microwave shielding shell (10) being provided with a circle of annular mounting groove (222), the inner side of the first mounting shell (22) being away from the outer conductor microwave shielding shell (10) being 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) being provided with a bolt mounting block (2231), the side wall of the first mounting shell (22) being provided with a bolt fixing hole (2232) penetrating the annular mounting groove (222) and the bolt mounting block (2231), the outer side wall of the coaxial microwave shielding inner conductor (30) being provided with a a mounting block (32) adapted to the inner conductor mounting groove (223), the mounting block (32) being arranged in the inner conductor mounting groove (223), the second mounting housing (23) being provided with a housing side wall (231) corresponding to the annular mounting groove (222), the housing side wall (231) being provided with a bolt mounting hole (232) corresponding to the bolt fixing groove, the housing side wall (231) being provided with an abutment block (233) adapted to the inner conductor mounting groove (223), the second A second through hole (234) adapted to the coaxial microwave shielding inner conductor (30) is provided at the top of the mounting shell (23); when the shell side wall (231) is inserted into the annular mounting groove (222), the bolt mounting hole (232) is aligned with the bolt fixing hole (2232) and is locked and fixed using a second bolt (235); the abutment block (233) abuts against the mounting block (32), so that the coaxial microwave shielding inner conductor (30) is fixedly arranged on the outer conductor microwave shielding upper shell (20).

7. A novel microwave heating print head according to claim 6, characterized in that: A polytetrafluoroethylene block (236) is provided at the bottom of the abutment block (233).

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