Tobacco microwave dryer and control method thereof

Abstract

The invention discloses a tobacco microwave dryer and a control method thereof, and the tobacco microwave dryer comprises a housing which is internally provided with a shielding cavity; the partition plate is arranged in the shielding cavity so as to divide the shielding cavity into a drying cavity for containing tobacco and a mounting cavity, and a microwave antenna is arranged in the mounting cavity; the microwave antenna comprises a micro-strip feeder line extending in the direction close to the drying cavity, the extending end of the micro-strip feeder line is connected with an emitting part expanding outwards in the radial direction, the emitting part is provided with a first surface facing the drying cavity and parallel to the partition plate, and the first surface emits microwaves to the drying cavity. The tobacco drying device has the beneficial effects that the emitting part which is parallel to the partition plate and has a certain area is arranged in the mounting cavity, so that microwaves are directionally propagated into the drying cavity in a manner of being perpendicular to the first surface and can directly pass through tobacco without being reflected by the wall of the cavity, the energy loss in the microwave propagation process is reduced, and the tobacco drying efficiency is improved. Therefore, the heating and drying efficiency of the tobacco microwave dryer is improved, and the heating and drying time is shortened.

Description

Technical Field

[0001] The present invention belongs to the field of tobacco drying, and more specifically, relates to a tobacco microwave dryer and a control method thereof. Background Art

[0002] Currently, the standard drying oven method is the mainstream method for tobacco leaf preparation in the tobacco industry. Drying ovens at home and abroad usually use electric heating for drying. The principle is to heat the resistance wire, and after the resistance wire generates heat, the tobacco is dried by the way of heat transfer through contact or medium; however, it has the defects of low heating efficiency, uneven heating, and the tobacco closer to the resistance wire is easily overheated. There is a drying oven with a magnetron installed inside, which heats the tobacco by the microwave generated by the magnetron.

[0003] However, since the magnetron cannot emit microwaves directionally, the microwaves can only pass through the tobacco and heat the tobacco after being reflected by the chamber walls in the shielding cavity of the drying oven for multiple times. Each reflection process of the microwaves will cause a loss of microwave energy, which makes the drying oven using a magnetron have the problems of low heating efficiency and long heating and drying program time.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, and provide a tobacco microwave dryer and a control method thereof. By providing an emitting part with a certain area parallel to the partition in the installation cavity, the microwaves are propagated directionally perpendicular to the first surface into the drying cavity, and can directly pass through the tobacco without being reflected by the chamber walls, reducing the energy loss during the propagation of the microwaves, thereby solving the problems of low heating and drying efficiency and long heating and drying program time of the drying oven.

[0006] To solve the above technical problem, the basic concept of the technical solution adopted by the present invention is: a tobacco microwave dryer, including a housing with a shielding cavity formed inside; a partition disposed in the shielding cavity to divide the shielding cavity into a drying cavity for accommodating tobacco and an installation cavity, and a microwave antenna is disposed in the installation cavity; the microwave antenna includes a microstrip feeder extending towards the drying cavity, and the extending end of the microstrip feeder is connected with an emitting part that expands radially outwards. The emitting part has a first surface facing the drying cavity and parallel to the partition, and the first surface emits microwaves towards the drying cavity.

[0007] Further, the shielding cavity is a columnar structure with a vertically arranged axis, the partition is horizontally arranged, and its outer peripheral part is connected to the peripheral chamber wall of the columnar cavity. The drying cavity and the installation cavity are arranged in the up-down direction; the emitting part is horizontally arranged coaxially with the shielding cavity.

[0008] Further, the installation cavity is located below the drying cavity. The upper surface of the partition plate is used to support the tobacco to be dried, and the first surface of the transmitting part is arranged at a certain distance from the lower surface of the partition plate.

[0009] Further, a support structure is arranged in the installation cavity. An installation part is connected to the lower side surface of the transmitting part, and the installation part is erected in the installation cavity through the support structure.

[0010] Further, each support structure extends vertically upward from the bottom of the installation cavity, and the end faces of the extending ends are respectively abutted against the lower surface of the installation part.

[0011] Further, the installation part is a disc-shaped structure coaxially arranged with the transmitting part. The diameter of the disc-shaped installation part is greater than or equal to the diameter of the transmitting part, and the transmitting part is in fitting contact with the installation part.

[0012] Further, the shielding cavity is a cylindrical structure, and the transmitting part is a horizontally arranged polygonal sheet structure.

[0013] Further, the diameter of the transmitting part is greater than the radius of the shielding cavity and less than the diameter of the shielding cavity.

[0014] A control method for a tobacco microwave dryer adopts the above-mentioned tobacco microwave dryer, and further includes a microwave generating device. The microwave generated by the microwave generating device is conducted to the transmitting part through a microstrip feeder; the heating and drying program includes a plurality of processes executed in sequence. In different process procedures, the microwave generating device generates microwaves in different working modes.

[0015] Further, when the heating and drying program starts, a preheating process is executed. During the preheating process, the microwave generating device is controlled to intermittently generate microwaves at a preset duty cycle to preheat the tobacco.

[0016] After adopting the above technical solution, compared with the prior art, the present invention has the following beneficial effects: By arranging a transmitting part parallel to the partition plate and having a certain area in the installation cavity, so that the microwave propagates directionally into the drying cavity perpendicular to the first surface and can directly pass through the tobacco without being reflected by the cavity wall, reducing the energy loss during the microwave propagation process, thereby improving the heating and drying efficiency of the tobacco microwave dryer and shortening the time required for heating and drying.

[0017] At the same time, the structure of the present invention is simple, the effect is remarkable, and it is suitable for popularization and use.

[0018] The following further describes in detail the specific embodiments of the present invention with reference to the accompanying drawings. Description of the Drawings

[0019] The accompanying drawings, as part of the present invention, are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an improper limitation to the present invention. Obviously, the accompanying drawings in the following description are only some embodiments. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. In the drawings:

[0020] Figure 1 is a schematic diagram of the internal structure of the housing of the embodiment of the present invention;

[0021] Figure 2 is a bottom view schematic diagram of a certain position of the housing of the embodiment of the present invention;

[0022] Figure 3 is a schematic diagram of the structure of the microwave antenna of the embodiment of the present invention.

[0023] In the figure: 1. Housing; 110. Shielding cavity; 111. Drying cavity; 112. Installation cavity; 120. Partition; 130. Support structure; 2. Microwave antenna; 210. Transmitting part; 211. Extension part; 212. Spiral part; 213. Conductive part; 214. Conductor patch; 220. Installation part; 221. Through hole; 222. Fixing hole; 230. Microstrip feeder.

[0024] It should be noted that these accompanying drawings and text descriptions are not intended to limit the scope of the concept of the present invention in any way, but to illustrate the concept of the present invention to those skilled in the art by referring to specific embodiments. Detailed Embodiments

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0026] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0027] In the description of the present invention, it should be noted that, unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] As Figures 1 - 3 shown, in an embodiment of the present invention, a tobacco microwave dryer is introduced, which includes a housing 1 with a shielding cavity 110 formed inside; a partition 120 disposed in the shielding cavity 110 to divide the shielding cavity 110 into a drying cavity 111 for accommodating tobacco and an installation cavity 112, and a microwave antenna 2 is disposed in the installation cavity 112; the microwave antenna 2 includes a microstrip feeder 230 extending in a direction close to the drying cavity 111, and an extending end of the microstrip feeder 230 is connected to a transmitting portion 210 that expands radially outward. The transmitting portion 210 has a first surface facing the drying cavity 111 and parallel to the partition 120, and the first surface emits microwaves to the drying cavity 111.

[0029] Through the above arrangement, by providing a transmitting portion 210 parallel to the partition 120 and having a certain area in the installation cavity 112, the microwaves are made to propagate directly into the drying cavity 111 perpendicular to the first surface, passing directly through the tobacco without being reflected by the chamber wall, reducing the energy loss during the propagation of the microwaves, thereby improving the heating and drying efficiency of the tobacco microwave dryer and shortening the time required for heating and drying; the partition 120 isolates the microwave antenna 2 from the tobacco in the drying cavity 111 to prevent the tobacco from adhering to or scratching the surface of the transmitting portion 210, realizing the protection of the transmitting portion 210.

[0030] In an embodiment of the present invention, the shielding cavity 110 is a columnar structure with a vertically arranged axis, the partition 120 is horizontally arranged, and its outer peripheral portion is connected to the peripheral chamber wall of the columnar cavity. The drying cavity 111 and the installation cavity 112 are arranged in the up-down direction; the transmitting portion 210 is horizontally arranged coaxially with the shielding cavity 110.

[0031] Through the above arrangement, the front surface of the transmitting portion 210 faces the vertical direction, directly facing the bottom surface of the drying cavity 111, so that the microwave field strength at each position in the same cross-section of the drying cavity 111 is equal, thereby ensuring uniform heating and drying of the tobacco placed or laid flat on the bottom of the drying cavity 111 by the microwave antenna 2.

[0032] In an embodiment of the present invention, the installation cavity 112 is located below the drying cavity 111, the upper surface of the partition 120 is used to support the tobacco to be dried, and the first surface of the transmitting portion 210 is spaced apart from the lower surface of the partition 120 by a certain distance.

[0033] With the above settings, by arranging the installation cavity 112 below the drying cavity 111, the microwave antenna 2 is closer to the bottom surface of the microwave cavity, thereby reducing the energy loss during the propagation of microwaves to the vicinity of the bottom surface of the drying cavity 111, enhancing the microwave field strength at the bottom of the drying cavity 111, and improving the drying efficiency of the tobacco by the microwave drying box. Additionally, by setting the emitting part 210 at a certain distance from the partition 120 to form a clearance space, it prevents the partition 120 for receiving tobacco from deforming downward due to aging or impact and squeezing the emitting part 210, causing the emitting part 210 to deform vertically or even be damaged, resulting in uneven distribution of the microwave field strength generated by the emitting part 210 or abnormal operation.

[0034] In an embodiment of the present invention, at least a part of the bottom of the installation cavity 112 is provided with an insulating layer, and the microwave antenna 2 is adhered to the insulating layer at the bottom of the installation cavity 112.

[0035] In an embodiment of the present invention, the emitting part 210 is a sheet-shaped circular conductor. The microwave antenna 2 further includes a microstrip feeder 230 for conducting microwaves. The microstrip feeder 230 extends upward from the bottom of the installation cavity 112, and the extending end is connected to the emitting part 210. The emitting part 210 is erected in the installation cavity 112 through the microstrip feeder 230.

[0036] In a preferred embodiment of the present invention, a support structure 130 is provided in the installation cavity 112. An installation part 220 is connected to the lower side surface of the emitting part 210. The installation part 220 is erected in the installation cavity 112 through the support structure 130, so that the microwave antenna 2 is assembled in the installation cavity 112 through the support structure 130. Compared with the adhesion method, the assembly stability of the support structure 130 is higher and the service life is longer.

[0037] In an embodiment of the present invention, each support structure 130 extends vertically upward from the bottom of the installation cavity 112, and the end faces of the extending ends are respectively abutted against the lower surface of the installation part 220, so that the emitting part 210 is erected in the installation cavity 112 at a certain distance from the lower side chamber wall of the installation cavity 112. By the upper end face of the support structure 130 being in close contact with the installation part 220, the support stability between the support structure 130 and the installation part 220 is improved. At the same time, the support structure 130 shortens the distance between the emitting part 210 of the microwave antenna 2 and the partition 120, further enhancing the field strength of the microwave field where the tobacco is located and improving the drying efficiency of the microwave antenna 2 for the tobacco.

[0038] In an embodiment of the present invention, the mounting portion 220 is a disc-shaped structure coaxially arranged with the transmitting portion 210. The diameter of the disc-shaped mounting portion 220 is greater than or equal to the diameter of the transmitting portion 210, and the transmitting portion 210 is in close contact with the mounting portion 220. By setting the mounting structure; by setting the mounting portion 220 with a larger surface, the contact area between the mounting portion 220 and the transmitting portion 210 is increased, and the stability of the connection between the two is improved; at the same time, the mounting portion 220 can support the transmitting portion 210 to prevent the transmitting portion 210 from deforming, resulting in an unstable microwave field intensity and affecting the drying effect of tobacco.

[0039] In an embodiment of the present invention, the outer peripheral edge of the mounting portion 220 is arranged at a certain distance from the transmitting portion 210 to form an annular spaced area. A plurality of fixing holes 222 are circumferentially distributed in the mounting portion 220 within the annular spaced area; so that the microwave antenna 2 is installed in the drying box through the fixing holes 222 on the mounting portion 220, and the support structure 130 connected to the mounting portion 220 is arranged at a certain distance from the fixing holes 222 to prevent the support structure 130 from colliding or rubbing against the transmitting portion 210, resulting in damage to the transmitting portion 210; in addition, the circumferentially distributed fixing holes 222 can ensure the stable fixed installation of the mounting portion 220 and prevent the mounting position of the mounting portion 220 from shifting, resulting in a reduction in the drying efficiency of the microwave antenna 2 for tobacco.

[0040] In an embodiment of the present invention, the support structure 130 is a screw post, and a screw hole is provided on the upper end face of the support structure 130. The mounting portion 220 is fixed on the support structure 130 by sequentially passing screws through the fixing holes 222 and the corresponding screw holes.

[0041] In an embodiment of the present invention, the support structure 130 is a telescopic rod that can be telescoped in the vertical direction, and the telescopic end of the upper end of the telescopic rod is connected to the mounting portion 220; by controlling the extension and compression of each telescopic rod, the orientation of the first surface of the transmitting portion 210 is adjusted; preferably, the telescopic end of the telescopic rod is hinged to the mounting portion 220.

[0042] In an embodiment of the present invention, the support structure 130 is arranged as a sleeve structure and is coaxially arranged with the through hole 221 of the mounting portion 220. The support structure 130 is sleeved on the outer periphery of the microstrip feeder 230, and a universal wheel is installed at the upper end of the support structure 130. The movable end of the universal wheel is connected to the mounting portion 220; by controlling the rotation of the universal wheel, the orientation of the first surface of the transmitting portion 210 can be adjusted.

[0043] In an embodiment of the present invention, at least one set of pressure sensors is provided on the partition 120. When the tobacco microwave dryer executes the heating and drying program, the pressure value is obtained, the center of gravity position of the tobacco is judged according to the pressure value, and the orientation of the transmitting part 210 is adjusted so that the first surface of the transmitting part 210 faces the center of gravity position of the tobacco; when the tobacco is unevenly laid in the drying cavity 111, by adjusting the orientation of the transmitting part 210, the microwave is targeted to heat the area with more tobacco, so as to ensure that the tobacco microwave dryer can uniformly heat the tobacco.

[0044] In an embodiment of the present invention, the mounting part 220 is made of an insulating material, and the insulating material is a material with a relatively high dielectric constant and a stable dielectric constant or a small change rate in the temperature range from normal temperature to drying temperature; including but not limited to ceramics, quartz stones, glass and zirconia; preferably, the mounting part 220 is made of ceramic material.

[0045] In an embodiment of the present invention, the transmitting part 210 is formed by bending and winding an antenna wire on a plane. An installation groove matching the transmitting part 210 and recessed inward is provided on the surface of the mounting part 220 facing the drying cavity 111, and the transmitting part 210 is correspondingly arranged in the installation groove; so that the transmitting part 210 emits microwaves through the notch of the installation groove in the direction of the notch.

[0046] In an embodiment of the present invention, the microwave antenna 2 further includes a microstrip feeder 230 for conducting microwaves; the transmitting part 210 and the microstrip feeder 230 are respectively arranged on the front and back sides of the mounting part 220. The transmitting part 210 is laid on the front of the mounting part 220, and the conducting end of the microstrip feeder 230 is connected to the transmitting part 210 through a through hole 221 opened on the mounting part 220, so that the microwave is transmitted to the transmitting part 210 through the microstrip feeder 230.

[0047] In an embodiment of the present invention, the mounting part 220 is a strip-shaped conductor patch 214, and one end is connected to the conducting end of the microstrip feeder 230; the conductor patch 214 is laid on the front of the mounting part 220 to form a sheet-shaped generating part parallel to the front of the mounting part 220 on the mounting part 220, so that the microwave extends in a direction perpendicular to the front of the mounting part 220.

[0048] Through the above settings, by laying the conductor patch 214 for emitting microwaves on the insulating mounting part 220, the microwave is propagated in a direction away from the mounting part 220, so as to realize the directional emission of the microwave, and the microwave antenna 2 can uniformly dry the tobacco.

[0049] The strip-shaped transmitting part 210 is printed on the front of the mounting part 220.

[0050] With the above settings, the emitting part 210 is adhered to the mounting part 220 through printing technology, which facilitates the production and processing of the microwave antenna 2. At the same time, through printing, an emitting part 210 with an extremely small thickness can be formed on the mounting part 220, greatly reducing the peripheral area of the emitting part 210. As a result, the microwaves emitted by the emitting part 210 in the direction parallel to the mounting part 220 are significantly reduced, and the loss of microwaves during propagation in the emitting part 210 is greatly reduced, improving the heating and drying efficiency of tobacco.

[0051] In an embodiment of the present invention, the conductor patch 214 is in a waveform. The horizontal axis of the waveform conductor patch extends circumferentially around the microstrip feeder 230, and the vertical axis extends in the radial direction. The starting end and the ending end of the conductor patch 214 are arranged in a dislocation manner. The conductor patch 214 is provided with an extension part 211. One end of the extension part 211 is connected to the microstrip feeder 230, and the opposite end is integrally connected to the starting end, the ending end, or the middle part of the waveform conductor patch 214, so as to form a microwave emitting surface of the conductor patch 214 on the mounting part 220.

[0052] In a preferred embodiment of the present invention, the starting end of the strip-shaped conductor patch 214 is connected to the microstrip feeder 230, and the free end spirally extends on the front surface of the mounting part 220 with the starting end as the center.

[0053] With the above settings, through the spiral extension of a strip-shaped conductor patch 214, a planar spiral-shaped emitting part 210 is formed on the surface of the mounting part 220. The conductor patch 214 extends with the circumferential radius gradually increasing from the starting end, so that the microwave intensities emitted by the parts of the conductor patch 214 with the same radius in different radial directions are basically equal, thereby further improving the uniformity of tobacco heating by the microwave antenna 2.

[0054] In another embodiment of the present invention, the conductor patch 214 is strip-shaped. The starting end of the strip-shaped conductor patch 214 is located at the center position of the front surface of the mounting part 220, and the free end spirally extends on the front surface of the mounting part 220 with the starting end as the center. The free end of the conductor patch 214 is connected to the microstrip feeder 230.

[0055] In an embodiment of the present invention, the conductor patch 214 includes an extension part 211 and a spiral part 212. The extension part 211 extends radially outward from the starting end of the conductor patch 214 for a certain distance. The extending end of the extension part 211 is integrally formed with one end of the spiral part 212, and the other end of the spiral part 212 spirally extends outward with the starting end of the conductor patch 214 as the center.

[0056] For the helically extending conductor patch 214, due to the relatively cramped space in the central region of the conductor patch 214, the part of the conductor patch 214 located in this region is prone to electromagnetic mutual coupling, causing the output power of the part of the conductor patch 214 in this region to decrease. In severe cases, the part of the conductor patch 214 in this region may be damaged, resulting in the overall disconnection between the microstrip feeder 230 and the conductor patch 214, making the microwave antenna 2 unable to work properly.

[0057] By providing the extension part 211, the starting end of the spiral part 212 is arranged at a certain distance from the initial end of the conductor patch 214, so that a blank area is formed on the mounting part 220 by the innermost circle of the spiral part 212. Without affecting the microwave field intensity, it prevents the central part of the conductor patch 214 from interfering with each other and being damaged, thus ensuring the stability of the operation of the microwave antenna 2 and improving the overall service life.

[0058] In an embodiment of the present invention, the extension length of the extension part 211 of the conductor patch 214 is greater than or equal to twice the width of the strip-shaped conductor patch 214; preferably, the extension length of the extension part 211 of the conductor patch 214 is less than or equal to four times the width of the strip-shaped conductor patch 214.

[0059] Through the above settings, by limiting the length of the conductor patch 214, only one or two turns of spiral-shaped conductor patches 214 are arranged less in the center of the conductor patch 214. Without interfering with each other in the innermost circle of the spiral part 212, the microwave field intensity in the central region of the conductor patch 214 will not decrease excessively, thus ensuring that the microwave field intensities output from each region of the conductor patch 214 are uniform, and enabling the microwave antenna 2 to heat the tobacco evenly.

[0060] In an embodiment of the present invention, an annular conduction part 213 is provided on the outer periphery of the through hole 221 of the transmitting part 210. The inner diameter of the annular conduction part 213 is equal to the aperture of the through hole 221, and the microstrip feeder 230 is connected to the annular conduction part 213; by providing the annular conduction part 213, the contact area of the microstrip feeder 230 is increased, ensuring the stability of the microstrip feeder 230 in conducting microwaves to the transmitting part 210.

[0061] In an embodiment of the present invention, the conductor patch 214 extends helically for multiple turns, and each turn of the conductor patch 214 is arranged at a certain distance from the adjacent turn of the conductor patch 214; by arranging each turn of the conductor patch 214 at intervals, the microwaves emitted are prevented from interfering with each other, reducing the energy loss during the microwave propagation process, thereby improving the utilization rate of microwave energy and the heating efficiency of the tobacco.

[0062] In an embodiment of the present invention, the strip-shaped conductor patch 214 is an Archimedean spiral structure centered on the initial end.

[0063] In an embodiment of the present invention, the strip-shaped conductor patch 214 spirally extends outward in a polygon with the initial end as the center to form the polygon-shaped emitting part 210; preferably, the conductor patch 214 spirally extends outward in an octagon with the initial end as the center to form the octagon-shaped emitting part 210.

[0064] Through the above arrangement, by setting a spiral structure with edges and corners, each turn of the conductor patch 214 has eight tips, and compared with the conductor patch 214 that spirally extends in a smooth arc shape, the effect of releasing microwaves is better, effectively improving the field strength of the microwave field; further, the emitting part 210 is a regular octagon-shaped sheet structure, making the distribution of microwave release points more uniform; for the polygon-shaped emitting part 210 with seven or fewer sides, due to the small number of corners and the large distance between them, the field strength at each position in the cross-section of the formed microwave field varies greatly; for the polygon-shaped emitting part 210 with nine or more sides, due to the large angle of the corners, the microwave release amount at each corner decreases with the increase of the number of sides, resulting in a lower field strength of the formed microwave field, and the heating and drying efficiency of tobacco is lower than that of the octagon-shaped emitting part 210; through simulation verification, among all microwave antennas with an input return loss S11 less than -10 dB, the S11 of the microwave antenna 2 with the octagon-shaped emitting part 210 is the smallest and the effect is the best.

[0065] It should be noted that for the present invention, the return loss is the reflection generated by the impedance mismatch of the emitting part 210, which is the reflection of a pair of lines itself and is an important parameter for measuring the performance of the microwave antenna 2; the return loss is negative, and only the microwave antenna with S11 less than -10 dB has better impedance matching, and the smaller the S11, the better the performance of the microwave antenna 2.

[0066] In an embodiment of the present invention, the shielding cavity 110 is a cylindrical structure, and the emitting part 210 is a horizontally arranged polygon-shaped sheet structure.

[0067] Through the above arrangement, by setting the cylindrical shielding cavity 110 to adapt to the emitting part 210 that emits microwaves through the first surface, each position of the circumferential chamber wall of the cylindrical shielding cavity 110 faces the central axis of the shielding cavity 110, so that the microwaves directly incident on the tobacco are refracted or reflected by the internal structure of the tobacco and diverge around, and the circumferential chamber wall can reflect the divergent microwaves in the direction close to the central axis of the drying cavity 111, so that at least most of the divergent microwaves are reflected once and then re-enter the tobacco, thereby improving the absorption efficiency of the tobacco for microwave energy and reducing the microwave energy lost due to reflection in the shielding cavity 110.

[0068] In an embodiment of the present invention, the diameter of the emitting part 210 is greater than the radius of the shielding cavity 110 and less than the diameter of the shielding cavity 110; during actual use, although most of the microwaves extend perpendicular to the first surface, there will still be some microwaves that propagate obliquely radially outward. By appropriately reducing the coverage area of the emitting part 210, the obliquely propagating microwaves are made to propagate to the area near the circumferential side wall of the drying cavity 111, so that the obliquely propagating microwaves directly pass through the tobacco without passing through the chamber wave emission, thereby further improving the utilization rate of microwaves and the heating and drying efficiency of the tobacco microwave dryer.

[0069] In an embodiment of the present invention, the housing 1 is made of a metal material so that the inner peripheral wall of the housing 1 shields microwaves to prevent microwave leakage.

[0070] In another embodiment of the present invention, a shielding layer is laid on the inner side surface of the housing 1; so that the housing 1 forms a shielding cavity 110 that can prevent microwave leakage through the shielding layer.

[0071] In an embodiment of the present invention, a microwave generating device is provided outside the housing 1, and a communication hole communicating with the shielding cavity 110 is opened on the lower side surface of the housing 1. The lower end of the microstrip feeder 230 extends to the outside of the housing 1 through the communication hole and is connected to the microwave generating device; so as to conduct the microwaves generated by the microwave generating device to the emitting part 210 inside the housing 1.

[0072] In an embodiment of the present invention, a microwave chip is provided inside the microwave generating device to generate microwaves; compared with the solution using a magnetron, the microwave chip has the advantages of light weight, high reliability, long service life, and simple control circuit, making the microwave drying box small in size, light in weight, and convenient to carry, suitable for use in the field; specifically, the weight of the microwave drying box is less than or equal to 15 kg, and the service life is greater than 100,000 hours.

[0073] In an embodiment of the present invention, the microwave frequency generated by the microwave chip is 915 MHz; compared with a 2450 MHz microwave chip, the 915 MHz microwave chip has the advantages of high efficiency, high reliability, and low cost, reducing the production cost of the microwave drying box and improving the drying efficiency.

[0074] In an embodiment of the present invention, a placement opening is provided at the top of the columnar housing 1 with a vertically arranged axis, and the object to be dried is taken and placed through the placement opening.

[0075] In an embodiment of the present invention, a basket with an upward opening is further provided in the drying cavity 111. The basket has a horizontal basket bottom, and an upwardly extending annular basket peripheral wall is provided around the outer periphery of the basket bottom, and the tobacco is laid in the basket.

[0076] In an embodiment of the present invention, an openable and closable door body is buckled on the access opening of the housing 1. The door body is made of a metal structure or an insulating layer is laid on the lower surface of the door body. The access opening is sealed by the door body, and a closed shielding cavity 110 is formed in cooperation with the housing 1.

[0077] In an embodiment of the present invention, a control method for a tobacco microwave dryer is also introduced. The above-mentioned tobacco microwave dryer is adopted, and a microwave generating device is further included. The microwave generated by the microwave generating device is conducted to the emitting part 210 through the microstrip feeder 230. The heating and drying program includes a plurality of processes executed in sequence. In different process procedures, the microwave generating device generates microwaves in different working modes.

[0078] Through the above settings, although the heating and drying program duration of the tobacco dryer for drying tobacco is relatively short, during the drying process, due to the change of the moisture content of the tobacco and the change of the humidity of the environment where the tobacco is located, the thermal conductivity between the tobaccos and the microwave energy absorption efficiency of the microwave will be affected. By making the microwave generating device operate in different working modes at different stages, the heating effect on the tobacco is optimized, and the tobacco microwave dryer uniformly heats the tobacco.

[0079] In an embodiment of the present invention, different working modes of the microwave generating device include, but are not limited to: generating microwaves at different powers and generating microwaves intermittently at different duty cycles.

[0080] When starting to dry the tobacco, the moisture content of the tobacco is relatively high. Since the absorption efficiency of water for microwaves is much higher than that of tobacco, the tobacco near the microwave antenna 2 absorbs a large amount of microwaves and heats up rapidly, and the internal moisture is rapidly volatilized into the gaps between the tobaccos. However, the microwave energy contained in the microwaves transmitted to the tobacco slightly farther away from the microwave antenna 2 is less, resulting in slower heating of this part of the tobacco and slower volatilization of the internal moisture. And it takes a certain amount of time for the volatilized water to be discharged through the gaps between the tobaccos. Especially for the microwave dryer with the installation cavity 112 arranged below the drying cavity 111, the volatilized water needs to flow upward and pass through the tobacco with slower heating to be discharged. At this time, if microwaves are continuously emitted into the drying cavity 111, since the absorption efficiency of the tobacco near the microwave antenna 2 for microwaves decreases as the moisture content decreases, the tobacco slightly farther away from the microwave antenna 2 is rapidly heated up and the internal moisture is rapidly volatilized, causing the air pressure in the downstream space of the original flow direction of the moisture volatilized from the tobacco near the microwave antenna 2 to increase, resulting in poor outward circulation of the volatilized moisture. Therefore, the volatilized moisture flows directly in the gaps between the tobaccos, and most of the microwaves radiated into the drying cavity 111 are absorbed by the volatilized water, making the heating rate of the tobacco in the initial stage of the heating and drying program slower. It is not until the tobacco at a relatively long distance from the microwave antenna 2 is heated to a certain temperature and all the volatilized water generated in the initial stage of the heating and drying program is discharged that the tobacco can be dried uniformly and efficiently. The following embodiments are proposed for the above problems.

[0081] In an embodiment of the present invention, a preheating process is performed at the start of the heating and drying program. During the preheating process, the microwave generating device is controlled to intermittently generate microwaves at a preset duty cycle to preheat the tobacco.

[0082] With the above settings, after the microwave generating device works for a period of time and then stops working, most of the volatile water generated by the tobacco closer to the microwave antenna 2 is discharged through the gaps between the tobacco. Then, after controlling the microwave generating device to work for a period of time and then stop working again, it is possible to prevent the moisture volatilized from the tobacco farther from the microwave antenna 2 from increasing the air pressure in the tobacco gaps, resulting in poor circulation of the moisture volatilized from the tobacco closer to the microwave antenna 2, thereby causing poor heating and drying efficiency of the tobacco at the beginning of the heating and drying program.

[0083] In an embodiment of the present invention, a detection unit is provided on the side of the heating chamber away from the installation chamber 112. The detection unit obtains the temperature of the tobacco. When the detected actual temperature is greater than or equal to a preset first temperature threshold, the pre-drying process is ended and the main drying process is started.

[0084] With the above settings, by providing the detection unit, it is possible to determine whether the tobacco at the farthest part from the microwave antenna 2 has completed preheating. When preheating is satisfied, the microwave generating device can be controlled to continuously generate microwaves to continuously heat and dry the tobacco.

[0085] In an embodiment of the present invention, during the main drying process, the microwave generating device is controlled to continuously operate.

[0086] In an embodiment of the present invention, after the execution time of the main drying process is greater than or equal to a preset heating time, the main drying process is ended.

[0087] In an embodiment of the present invention, an image acquisition module is provided in the heating chamber. When the heating and drying program is started, the image information of the tobacco in the heating chamber is acquired, and the thickness of the cut tobacco is judged according to the image information, and the operating power of the microwave generating device is adjusted according to the thickness of the cut tobacco.

[0088] With the above settings, since the thickness of the cut tobacco is different, the efficiency of absorbing microwaves is also different under the same microwave field strength, resulting in different heating rates. By adjusting the microwave field strength according to the thickness of the cut tobacco to be heated, it is possible to prevent the cut tobacco from being overheated or not being effectively dried to the expected moisture content.

[0089] In an embodiment of the present invention, a cut tobacco diameter threshold is preset; after acquiring the image information, it is judged whether the diameter of the cut tobacco is greater than the cut tobacco diameter threshold; if so, it is judged as thick cut tobacco, and the microwave generating device is made to operate at a first operating power; if not, it is judged as thin cut tobacco, and the microwave generating device is made to operate at a second operating power.

[0090] In an embodiment of the present invention, the first operating power is greater than the second operating power.

[0091] In an embodiment of the present invention, the control steps of the tobacco microwave dryer include:

[0092] S1: Start executing the heating and drying program;

[0093] S2: Obtain the image information of the tobacco, and judge whether the diameter of the cut tobacco is greater than the cut tobacco diameter threshold according to the obtained image information. If so, execute S3; if not, execute S4;

[0094] S3: Adjust the microwave generating device to operate at the first operating power, and execute S5;

[0095] S4: Adjust the microwave generating device to operate at the second operating power, and execute S5;

[0096] S5: Start the preheating process, and control the microwave generating device to generate microwaves at a preset duty cycle interval;

[0097] S6: The detection unit obtains the actual temperature in real time. When the obtained actual temperature is greater than or equal to the first temperature threshold, the technical preheating process is performed;

[0098] S7: Start the main drying process;

[0099] S8: After controlling the microwave generating device to continuously operate for a preset heating time, end the main drying process;

[0100] S9: End the heating and drying program.

[0101] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art of this patent, without departing from the scope of the technical solution of the present invention, can make some changes or modifications to the above-mentioned technical content by using the above-mentioned hints to make equivalent embodiments of equivalent changes. The implementation schemes in the above embodiments can be further combined or replaced, but as long as the content does not depart from the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the present invention.

Claims

1. A tobacco microwave dryer, comprising: A housing, internally formed with a shielding cavity; A partition board, disposed in the shielding cavity to divide the shielding cavity into a drying cavity for accommodating tobacco and an installation cavity, and a microwave antenna is disposed in the installation cavity; It is characterized in that: The microwave antenna includes a microstrip feeder extending towards the drying cavity, and the extending end of the microstrip feeder is connected with a transmitting part that expands radially outwards. The transmitting part has a first surface facing the drying cavity and parallel to the partition board, and the first surface emits microwaves towards the drying cavity.

2. The tobacco microwave dryer according to claim 1, It is characterized in that: The shielding cavity is a columnar structure with a vertically arranged axis, the partition board is horizontally arranged, and its outer peripheral part is connected to the circumferential chamber wall of the columnar cavity. The drying cavity and the installation cavity are arranged in the up and down direction; the transmitting part is horizontally arranged coaxially with the shielding cavity.

3. The tobacco microwave dryer according to claim 2, It is characterized in that: The installation cavity is located below the drying cavity, the upper surface of the partition board is used to support the tobacco to be dried, and the first surface of the transmitting part is arranged at a certain distance from the lower surface of the partition board.

4. The tobacco microwave dryer according to claim 3, It is characterized in that: A support structure is arranged in the installation cavity, an installation part is connected to the lower side surface of the transmitting part, and the installation part is erected in the installation cavity through the support structure.

5. The tobacco microwave dryer according to claim 3, It is characterized in that: Each support structure extends vertically upwards from the bottom of the installation cavity, and the end faces of the extending ends are respectively abutted against the lower surface of the installation part.

6. The tobacco microwave dryer according to claim 4, It is characterized in that: The installation part is a disc-shaped structure arranged coaxially with the transmitting part, the diameter of the disc-shaped installation part is greater than or equal to the diameter of the transmitting part, and the transmitting part is in close contact with the installation part.

7. The tobacco microwave dryer according to claim 2, It is characterized in that: The shielding cavity is a cylindrical structure, and the transmitting part is a horizontally arranged polygonal sheet structure.

8. The tobacco microwave dryer according to any one of claims 1-7, It is characterized in that: The diameter of the transmitting part is greater than the radius of the shielding cavity and less than the diameter of the shielding cavity.

9. A control method for a tobacco microwave dryer, It is characterized in that: The tobacco microwave dryer according to any one of claims 1-8 is adopted, and it further includes a microwave generating device. The microwaves generated by the microwave generating device are conducted to the transmitting part through the microstrip feeder; The heating and drying program includes a plurality of processes executed in sequence. In different process stages, the microwave generating device generates microwaves in different working modes.

10. The control method for a tobacco microwave dryer according to claim 9, It is characterized in that: When the heating and drying program starts, a preheating process is executed. During the preheating process, the microwave generating device is controlled to intermittently generate microwaves at a preset duty cycle to preheat the tobacco.

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